- Email: [email protected]
The Lung Worm and the Stomach Worm in the Cat
THE LU TG WORM IN THE CAT
97
6~n~ral Jlrticl~ THE LUNG WORM AND THE STOMACH WORM IN THE CAT. By THOMAS W. M. CAMERON, M.A., Ph.D., D.Se., M.R.C.V.S., [ ect'urer and M ilner R esearch FelloZIJ in the Department of Helminthology of the London School of Hygiem and Tropical !VIedicine .
Introduction. IN 1865, Leucka rt found in the stomach of the domestic cat a minute bursate worm which he named Oll1llanus tric~tspis. H e found also what h e believed were the free la rva! of Ollula nus ; fonns which measured about 320". long by 15". wide, had a truncated oral extremi ty and a short tail whi ch end ed in a short S-shaped tip (PI. 1 (a)): t he ccsophagus was between one-third and one-ha lf of the total length of the intestine. A !though there are seldom more than t hree embryos inside th e female, larva! were usuall y found in large numbers throughout the whole intes tina l tract of the host, as well as encysted (in cysts · 15 to ·2 mm. in diameter) on ,·arious intern al organs. The cyst wall had a connective tissue-like structure of such thickness that it might b e three or four times the diameter of the enclosed s pace. This space was either filled by the tightly wound coils of the worm or with a clear liquid . 1£ p resent in la rge numbers in the lungs, these capsules caused the appearance of miliary t uberculosis- especially when surrounded by a n area of hepatisation . They might even be th e focus of a widespread inflammation which in one of his cases at least , led to the death of the cat. Embryos were not found in th e blood or muscles, hut in heavy infect ions were free in the bronchi. The encys ted embryos , unlike Trichinella, did Ilot continue their development , but gradually degenerated, and fmally came to resemble a n egg. Leuckart fed these e mbryos to a mouse a nd six weeks la ter found humlreds of them encapsuled in th e muscles- these forms being intermedia te in form between the free embryo a nd the fully developed Ollulanus. The capsules- about . 3 mm.- were not only found in th e rump muscles a nd cesophageal wall, hut also in the heart and in the loose connective tissue of the neck. The wall was it simple connective tissue one, surrounded by nodules and containing numerous gran ules which we re moved about by the movem ents of the larva (PI. 1 (b) ). The enclosed worm had increased in size and was about ·8 mm. long by ·04 mm . broad. The blunt end sh owed a retracted chitinous
98
THE VETERL'\.\RY ]OLR\AL
disc which, from analog.\-, might be taken as the tirst indication" (" the future mouth, The cuticle was thicker and ringed. I{oune! th( lip-like projections were a few papilla-like outgrowths, The tail was simple and pointed, The in testine had not changed except that tJw pharynx was comparat ively shorter and showed a muscular structure The intestine was brown and towards its middle the ~Iighth' enlarge(t bean-shaped gcnital primordia could be seen, He was unable to decide whether these stages had reached maturity but going by the results of an experiment, he considered that furthe r dCH'lopment in the mouse was possible. ,-\n infectcd mouse was fed to a cat and eight days later the worms were lTco\'ered from i t unchanged, but in the cGecum and rectum, not the stomach, As only a few were found, it was belie\'ed that they were cn route fo r the exterior and Leuckart considered that all the conditions necessary for further de\'Clopment were not present.
Platl' I .
(a) Embryo of Oltulanlls tricu , pis (after LClIckarl, 1R67) (b) Fn capslIJat.-cl cmhn'o in mllscles of mOllsP (after Lell c ka,·t, 1;;67)
Only one other experiment is recorded. Two young rat,; were fed with the stomach wall of a cat infrcted with Ollulanns laJT<-e , and after 2 ~ hours and three clavs respecti\'cly, the majority of the introdnced worms were rrco\'Cred ali\'e and undamaged in the stomach, Cobbold in Britain was also studying the parasite, although he preferred to lise the namc 01 ulanus in stead of the more correct Ollulanus, In discussing the probable life histories of the lung \l'orms ill general, Cobbold (1875) drew attention to I.euckart's belief that " all these strongyloides required a change of hosts bdore they can take up their final abode in the sexually mature state . This he infers especially because their respective embryos display characters very similar to those exhibited by Olulanus," He considered the question fully in a paper read before the Quecket t }Iicroscopical Club in 1885. He stated that his f1rst arquaintane,
THE LUNG
~,YORM
IN THE CAT
99
with the larvce of Olulanus was made about 35 years previously, when a young cat in his room suddenly rushed about and finally fell dead, asphyxiated. While yet warm, it was dissected and its lungs were found to be swarming with nematode larvce. Drawings were made, but no specimens were preserved, and it is not stated whether any adults were seen in the stomach. He then briefly recapitulated Leuckart's work on the subject, and described a case which he had seen with Mr. Gay, a surgeon, in which a family, together with their donkey and cat, had suffered from a condition which was suspected to be Trichinosis. On investigation, no evidence of this was found, but the lungs of the exhumed cat were
c A
D
Plate 2.-(a), (b), anrl (e), Eggs of St1'nngylus pusillus (a fter H.n.illipt). (d) Free embn'o (after Railliet). (e) Bursa of Strongylus pusilhts (after Muller). (f) and (g) Posterior ends of embryos (after MUller)
found to be swarming with" Nematoids." Cobbold considered that this was a case of "Olulanosis," and states that "Whatever interpretation be put upon the human outbreak, the coincidence of the occurrence in man of an affection symptomatic of trichinosis, found in association with a trichinoid affection in an animal which proved olulaniasis, was both curious am! instructive," No subsequent work on the subject seems to have been done, excepting some negative experimental attempts at infection by Galli-Valerio in 1921. Meanwhile, in 1890, Mi.iller described from the cat in Germany a new form of lung-worm which he called Strongylus pusill1ts, and Eailiiet (1898) proposed the new specific name of S. abstrus1/S instead :
100
THE VETERINARY JOURNAL
Later (1907) H.ailliet a nd Henry transferred thi s species to the gen us Synthetocaulus, a genus recently shown by Leiper to be a synon ym of Protostrongylus. It is unnecessary to recapitulate MUller's desc ription of this parasite. The origi nal figures a re reproduced (PI. 2) , which show that Leuckart had C0nfused two separate a nd distinct parasites in his work. This is furth er confirmed in t hf' account of the life histories which follows. Both of these parasites have been mentioned in \'etcrinary literat ure since the dates of thei r discovery, but nothing has been added t.o our knowledge of their morphology a nd life history.
The" Lung"Worm" of the Cat. The lengt h is approximately 4 mm . in the male a nd (1 mm . in the female. The mouth ope ning is surrounded by six inconspicuous papilla:. a nd opens directly into th e short almost cylindrical (eso ph agns. which is about 0·25 mm. long. The m ale has a sma ll but well-formed bursa, which is complete a nd undivided . The cuticul a r hursal supports seen in Protostron/!,yllls a re absent. The spicules a rC' similar and eq ual, measuring 0·075 mm. in length . Each consists of a cuticnla r t ube, which is swollen a nteriorly, but terminates in a blunt point. To each is a tt ac h ~d a voluminous sheat h which is tra nsversely striated . but which is without the supporting lingers Sf'en in Protostrongylus. Th e female has a double genital system. The tail is bluntly pointed and the re a re no papillcc present . Th e an us is 0·04 mm . from the t ip of the tail and t he rectum is ve ry short. The ndva is (). 09 mm. {rom the a nus a Ild comm un icates wi th a long single vagin a, which in turn joins th e two parallel uteri . The \'agina is abo ut 1·5 mm . long and contain s unsegm ented eggs measuring abo ut 80/J, long by 70 fl broad. This parasite was originally placed in the ge nus IJrotostrongyllls by Kamensk)" and in the genus Syntf1etocallllls (whi ch is a synonym of Protostro ngylus) by Rai llid and H enr~T. but it obv iously docs not belong to the same genus as Protostrollgyllls YlIJesce1-ls : and accord ingly the new gC'n us Aellirostrongyllls has DC'en creatC'd b~' the writer for its rrception. Its correct namc is the refore A elllrostron{!yllls (IhstmslIs.
The Morphology of the Larva in the Cat. The eggs , laid in the ah'coli and parenchymatous tissue of the lungs, hatch il1 situ. and the la n '
T HE LUNG WOR M IN TH E CAT
] 01
s wallowed and pass out with the freces. From the time of hatching until the time that they leave the body in the freces , no apparent c hange in morphology takes place. The larvce have been allowed to hatch in the dead body of the female A elurostrongylus, so that there is no possibility of this heing the larval stage of any other species of worms. The larva is about 0·36 mm. long and 0·015 mm . broad (Plate 3). The mouth opening is simple and is surrounded hy six low papillce. The cuticle is covered with very fine transverse striations and a douhle lateral line is seen, suggesting that the first larval stage is omitted in this species. The cesophagus is 0·14 mm. long and has a central, as well as a posterior, swelling. The anterior part of the cesophagus, t('rminating at the central bulb , i largely muscular ; th(' posterior portion is distinctly glandular. The anterior swelling has a diameter of about O' 006 mm., the posterior swelling, about O'Ol mm., and the narrow part, 0·003 mm. The cesophagus communicates with the mouth opening by means of a cuticular buccal tube which seems to be continuous with the cesophageal lumen. This tube is dila ted centrally, but converges slightly towards its . Uurostrongylus abstmsus. Pla te 3.- 0 vum a mI larva as found in the lungs and intestine anterior junction with the inof a cat, ~ h owin g th e varia tion in ta il fo rm . fl eAcd cuticle. The intestine is very granular and measures about O· 19 mm . in length . It is connected with the anus by m eans of a short cuticular rectum . JlIst posterior to the anu<; i<; a small protuberan ce which is inconstant in siz(' , but is always present . The anus is about 0·03 mm . rrom the tip of the tail. The tail is very characteristic and carries a n undula ting appendix a nd normally a dorsal proj ec tion: these vary very considerably in s ize and relative position .
] 02
THE VETERI NARY J OURNAL Biology of the Larva.
Althoug h la n ' are \'ery acti ve when isola ted on a slide from the lung o r intestin a l contents. and , wh en collec ted in wa ter , they still retain t heir activit y. They normally move a bout with a n undulating movement , but in a flu id medium mak e very little forward progress. In mucoid fcecal material, hO\\'ever, they do p rogress slig htly. Th e~ ' do not apPGar to climb from fcecal cultn!'es in Pctri-di shE's as so man.\· of th e Strongyle lan ';e do. SJ\ I:\ P E:\ETRAT IO:-l.- .\ lI11m ber {Jf la rvce were collected in a small drop of water and tested for skin penet ration by means of the Goode\' " Floating Ha ft " techn ique, the skin of a young rat being used. Th e la n 'ce mo\'ed act i\'ely on t he surface of the skin , but mad e no attempt to pene trate it. .-\fter t he drop of wate r had e \'apora ted th e surface of the skin was cove red with egg albumen ~l.I1c1 when this had dried , t he skin was fixed , an d se rial sec ti on cu t. Th e la n 'ce could be seen on the surface a nd none h ad attempted to penetra te the skin . The salin e used for floating the raft was centrifuged , but no trace of la n ',e could be di scovered . Thi s e xperim ent was repeated with lan';{' from the fceces (coll ec ted by straining, a nd d ecanting and centri fuging) \'a ry ing in age from one to eight days. In a ll cases, 110 lan·a.: were found to penetrate the skin , and it appears legitim a te to conclude from thi s series of expe riments th a t the larvce arc not skin penetrato!'s. D URATI O:\ OF LI FE.- The lan'ce do not see m to be ab le to live ill the free state for o\'er a fortnight- the longes t period for which the writer could keep t helll ali ve in wa ter being 11 d ays. Th ey appeared to die e\'e n earli er in fceces. During their period of free life only dege nera ti ve cha nges we re observed, a nd in no case did they show a ny sign of further e\·olution. FEEDI?\G EXPERBIEt\TS WITII i\lI CE. - Following the cxampl e of Leuckart , these lan'ce \\'ere fed to a num ber of tame whi te mi ce bred in capti\'ity. All thc mi ce we re oht
THE L NG WOl.{M I N THE CAT
103
were fou nd to be negative, so far as could be ee n. All these experiments were full y controlled by keeping mi ce o f the same origin and age, uninfected with la rva' of Aelurostrongyhts: in none of t hese was any extra-intestinal parasite ever found . In this way, 21 control mice were examined . ~fi ce were fed in batches: (a) by feeding on infected embryo-bearing lungs; or (b) by feeding with la rva' isolated from lungs or intestine or stomach placed on moistened biscuit or bread. Care was ta ken to see tha t all the ma terial was eaten, but it was no t possible to say if every mouse in every ba tch had swallowed larva'. It is, th erefore, impossible to say whether the six negative results recorded aboye were due to not being infected , or were slight in fec tions overlooked , or we re really failure . Sufficient positives were obta ine d, however, to ma ke it certain tha t the larva' described below arc really furt her s tages in the developmen t of A elurostrongyltts.
The Infective Larva.
., 1
\ \
'J ,
._
'~t>~~ . - . ,.
.
,, -
.TluYo;;/ro l1[!)'lus abstrusus . Plate 4.- L
It was fo und t hat t he most convenient way to fi nd if a mouse was infected was to pin the anima l on a board with its ;:l.bdomin al surface upward. The skin was then
;~::C~~dt~:ct~~~n~~~~ s~;~
underlying areola r t issne examined T he worm-con.
.
tain ing cysts we re often "isible to the naked eye, as " bubbles" lying superfi cial to the muscles of the leg. Whether so visible or not, a piece of this tissue was fl'Il1o' -ed with c urved scissors and placed between two slides and examined microscopi cally. Tn this way material was obtained for the follo wing description. If the mouse proved to be infected the remainde r was fed to a kitten. The cysts are about 0·3 mm . in diam eter, a nd ha\-e a thin fibrous \I-a ll. They arc filled with a yellow granular or caseous materi al in th l' centre o f which the larva is seen coiled on itsel f. \Vhen removed from the cys t the larva is found to be 0·725 mill . long (Plate 4) a nd about 0·025 mm. in t hicknes. It is finely striated trans\·ersel\-. The <:esophagus is now 0·21111ll. long, 1·.e. the ratio
L04
THE VETERI NARY JOURNAL
of the length of the <:esophagus to the body length is 1 : 3·5; whereas in the earlier larva it is about 1 : 2·5. The central bulb has disappeared a nd the posterior bulb i rela tively smaller. The whole <:esophagus is mu ch more muscula r a nd less gra nula r th a n in the previous stage. The mou th is a simple pore communicating with the <:esophag us by means of a cuticula r buccal tube. The buccal tub~ consists of a more highly cuti cula rised a nterior portion, and a less high ly cuti cularised posterior portion whi ch communicates directly with the lumen of the <:esophagus. The anterior portion has a small number of rugce on its exteri or surface , while the interior surface is smooth . The intestine is about 0·35 mm . long and is very gra nul ar. It communi cates with the a nus hy means of a straight rectum abo ut 0·02 mm. long. Th e a nus is situa ted a hout 0·04 mm . from the tip of the tail. The tail is bluntly pointed . Towa rds its tip, the body narrows rather suddenly and the posterior portion is s urro unded by deep striations whi ch give it a errated a ppearance. There is n ow no trace of th e undul ating appendix seen in the previous stage (Pl at e 3) .
Experiments on Cats. The experimental work on cats fell into two groups: (a) feeding with free la rvc.e from othpr ca ts; a nd (b) feeding with encysted la rva:' from mice. (a) Four cats were fed on various dates with the larvce isolated from the lung tissue and from the intestine. The first two we re feel from tree t infections which were contaminated with OUulantts tricuspis. In these two animals the infec tion with th e latter parasite was demon trated on post-mortem examination , bllt in all four no evidence of A elu,rostrongylu s could be seen . (b) Seven animals were fed at various da tes with mice which contained encysted la rvce as elpscribed above. Two of these ani m al .~ died from distemper shortly a fter infec ti on, and no evidence of lung infection could be seen. In tr.e ot her five , howeve r . Ae!1Irostrongylus was found in the lungs. Habitat. The exact habita t of the adults has never been described. There a re four possible localities in the lungs where parasitic worms can live: in the bronchi or bronchioles ; in t he alveoli; in the interstitia l tissue; or finally , in the blood vessels of the lung. During a stud y of th e lesions provo ked by t his parasite in the lungs of the cat, one was struck by two peculiar facts. First ly, adults were never seen in severa l hundreds of secti ons exam ined. although
THE LUNG WORM IN THE CAT
105
eggs and la rvce were plentiful. The adults were only found in teased (The ections we re mainly prepared from marginal specimens. portions of the lung.) Secondly , the eggs in varying stages of development were eve nly di stributed throughout the lung a nd were not isolated in any particular a rea. These facts suggested the possibility of a blood distribution of the ('ggs, and th e blood stream as the norm al habitat 0f th e ad ults. An infection in a kitten was diagno ed by the presence of the cha racteristi c larvce in the fceces. Th e vessels between the heart a nd the lung were th en ligatured close to each of th ese organs, but without in a ny way interfering with them . Th e ligatured portion of the vessels was then removed, opened in saline and the contents shaken out. Fully adult male a nd female specimens of Aelttrostrongylus were found in these vessels. The lung itself wa then removed from the body, and still othe r adults were recove red in th e la rger branches of th e pulmonary vessels. Although th ere a re ma ny essential details of the life history of . Ielurostrongylus abstmws still remaining to be elucid ated- more especially th e development of the la rva in the mouse a nd t he development of the ad ult in the cat- it may be sta ted tha t th e essenti a l outline of its life history is as follows ;The adult parasites become mature in t he p ulmon a ry vessels, and th e female deposits her la rge, thin-shelled eggs in the blood stream. They are mechanically carried to the capillaries of t he lung, where their progress is arrested , a nd where the unsegmented ovum develops into the characteristic la rva. When m at ure, the la rvce force their way thro ugh the t hin -walled tissue into the alveoli , a nd in this way reach th e exterior afte r trave rsing the bronch ioles, bronchi , trachea and a limenta ry tract. Occasionally in v ery young animals a nd with \'c ry heavy in fecti ons, t he eggs th emselves ru pture the capillaries and, escaping in a n undeveloped condi tion into the a lveoli , then continue their development. The fceces are eaten by mice and the la rva migrates to various situations a mong the mu scles and in the subcuta neous tissue, where, within three weeks, it assumcs a n infecti ve, encysted form . It may rcmain v iablr for a t Irast a year in this situa tion. If the mouse is now eate n by a cat , th e la rva e capes from the cy t a nd , reaching the Illngs, within six wee ks becomes a ma ture egg-laying ad ult . vVhile the prese nt writer has neve r seen la rvce outside of th e respirato ry or alim enta ry t racts, Leucka rt has described them from \',uious parts of th e boely. Leuckart beli eved that he was dealing with the lan 'ce of OIlIf/al1l1s , hut in that he was unrloubterll y mistaken.
106
THE VETERINARY JOUR:\AL
Hi s infections were, unknown to him , mix cd ones, of both tl1(' lu ng a nd the stomach forms. Recently , Professor Leiper has becn cond uct ing a scrics of experiments with Trichinella spiralis , a nd he was struck with t he unusual appeara nce of t he cysts· in cats caused by the la r va of this species. I nstead of th e usual lemon-s haped cyst so characte ristic of mice a nd pigs, the cyst was almost sphcrical, altho ugh the infection was originally from rats with" normal" cysts. This is obviously because the host reaction in t he cat (and exam ina tion of cysts fro m ot her ca rni vores, showed that it is probably a 'gro\l p rcaction) differs fro m that of thc roden t or the pig, and is not due to the rc hein g present a different spcc ies of Trichinella. These cysts'measurc about 0·2 mm. in diameter a nd corrcspond to Leuckart' s description , cxcept that th e cyst wall is not so thi ck. As rodents a re na t urally eaten by cats, it is possible t hat Leucka rt's an imal in add ition to suffering from A elurostrongyl1ls and OUulanu s, also suffered from a "Frichinella infect ion ; hut their distribution docs not lend support to thi s hypo th esis, as they occurred in situations wherc Trichinella larvee rarely a rc found . From the aboye discussion, it would seem morc probahle th a t t hey were la rvee whi ch had- eith er as o"a or la r\'<:e- passed through th e pu lmonary capill a ry n etwork and so bee n ca rried to th e \'a rious organ s by the blood stream. The encystment would bc t he na tural reaction of the host tissues to any foreign body. The geog ra phical d ist ri bution of .-1 el llrostroll[;yl ll s abstrtl slI s is in completely kn own. It has bee n reported from Ge rma ny, Fran ce, a nd from Nort hern Italy and Switzc rla nd . It h as no t pre\'iously bcc n recorded frol11 Britain, but th crc is li ttlc doubt tha t the forms sec n b\" Cobbold and Stirli ng should be refe rrcd to thi s spccics.
Ollulanus tricuspis, the Stomach- Worm of the Cat. The adult worms li\"e on th e surface of t he stomach a nd in th e acini of thc stomach glands. In ve ry hca"y infec tions, th ey m ay evcn bc fo und in th e first in ch of t he duodenum , b ut t he:-" h a \'c ne \'er becn fo un d bcyond th e d uodenal fl ex ure. This is a nalogous to thc sta te of aftairs see n in other stomach worms in other a nimals. Thcir presence on t hc surfacc of t hc gastric mucosa ca uses th c prod uct ion of a t hick glai ry mucus whi ch assists in kecping t hcm in posit ion. Th ey a p pear to bc \'e ry let ha rgic in t hcir mo\·cme nts . I n t hc frcsh statc the parasitcs a rc colourless, anct a rc genc rall l' fo und with thc hcad e nd coiled on itsel f. Thcy a rc very minutc , t he male mcasuring only ·7 to ·8 mm. ill lcngt h, with a n avcrage breadth of . 03;) mm.; whil c thc fcma le i,; ·8 to I mm . long, a nd about ·01 mm . broad .
THE LUNG WORM I
THE CAT
107
The cuticle is faintly striatcd transversely and more conspicuously striated longitudinally. THE ANTERIOR EXTREMITY.-A small buccal cavity is present con taining no t eeth, cutting plates, ~ or similar structures. The cavity is formed by a reflection of the I . cuticle, and in optical section is almost spherical (Plate 6). The lateral diameter is . 004 mm., and its antero-posterior diameter is ·005 mm. The cesophagus, which is about . 2 mm. long, i only slightly swollen posteriorly. The cesophageal muscles are poorly developed. THE MALE.- The bursa (Plate 5) is undivided , and is open only Plate [) -Ollulanus tricusp ·is. Titil of m ale on the ventral side. O/tu/.1nlls triCltspi s. (a) Dorsa l ray of The spicules are equal in length mal e bur'ia, (h ) SpIcule (c) taIl of femp-le. (about ·05 mm. ) and are bifurcated , onc bifurcation being sharp and the other rounded . Th cre is no accessory piecc. THE F E ~IALE. _ . The vulva (Plate 6) is a prominen t structure si tna tcd in the posterior reg ion of th e body, whi ch it dividcs in the ratio of approx imately fi ve to one. The \'llh'a opc ns into a short \'agina, wh ich is continued anteriorly as a singlc uterus. Thc junction of uteru s a nd vagina is smrounded by a granular mass in .J the immature female. This disappears in th e mat urc f(,male. There is no ovejector. P late 6.- 011utallus triCltsp is. Gravid fe. The si ngle ovary originates about male showing egg, developing first st age and developed first stage larva. tl1 e. Ie\.e I 0 f th e cesop h agea I buIb , larvit A second stage la rva was also removed and inse nsibly joins thc nterus: by dissection fro m t his sprr imen , hut it is not sh own i n th e drawing. t I1C o\'a are very I a rge an d g ran ular. ,As tbe worm becomcs older, the ovary becomes confined to th e anterior part of the body, the remainder of whi ch is occupied by the
'.
~
~.
~
' 01 UUD
trim
J08
THE VETERINARY JOURNAL
intestine and one to three very large larv::e (. 3 to ·35 mm. long). The anu is situatecl abo ut ·03 to ·04 mm. from the posterior end. The tip of the tail has typically three" cusps" or teeth ; but occasionally one or two small extra cusps are found. GENERAL EVOL UTIO N.- The large gran ular egg formed in the single uterus grad ually develops into a larva, whi ch escapes from the thin eggshell , and subsequently moults--still inside the female- resulting in a form with tricuspid tail. The next stage seen is free in th e stomach of the cat. Fin ally, a lso free in the stomach , i~ found a stage comparable with th e fourth stage larva of the ot her Strongyles_ The sheath o f this form , in both sexes, carries a typical tricuspid tail. All t he forms found free in th e stomach of th e at- except the ad ult m ale- possess a typical tricuspid tail and bear no resemblan ce whateve r to the larva of A elurostrongyl·us abstntsus_ TH E FIRST LARVAL STAGE.- This form is first seen in side t he distendeo egg-shell (Pl a te 7), but ultim ately com es to lie free in the uterus of the female. The descripti on of this a nd the next s tage has been prepared from specimens di s ected from the uterUS of gravid females. This larva differs from all subseq uent stages ill possessing a round blunt tail. It is 0-35 mm . long and about 0-002 mm. in thicknes _ The mouth opening is a simple pore, apparently not surrounded by circumoral papillce. A distinct bu cca] tube, somewhat dilated centrally, connects the mouth pore with the <:esophagus. T he (esophagus is about 0,] 25 mm . long and is of the usnal type seen in young strongyle larv
THE Ll NG WORM I
THE CAT
109
length with an ce ophagus 0·0125 mm. long, have been dissected from gravid females. THIRD STAGE LAHVA .- This form measures 0·5 mm. in length with a width of about 0·022 mm . Th e sk in is fin ely st riated. The mouth openi ng i impl e, but it communicates with u. V-shaped buccal cavity, th e straight sides of which a re cuti cularised. The (esophagus whi ch sti ll has a sli ght constriction, is 0 ·15 mm. long with a maximum width of 0·012 mm. Th e inte tine is yery granul a r
Plate
j
(Icft to right) ..- DeveJopi ng first stage larva; fully d('\"(: loped first stage ; second stagc: third or infective stage.
a nrl measures 0·35 mm . in length. Towar~ls the posteri or portion of the intestine, a nd running parallel with it, is seen the elongated genital rudiment. Th ere is, of course, still no trace of a gen i tal opening. Th e a nus is 0·03 mm . from th e tip of the tricuspid tail. This form , unlik e the adults, usually lies curved like a n arc, and is found , 110t only in the sa me positi on as th e adu lts. b11t free in the cavitv of th e stom ac h.
110
THE VETERINARY TOt:RK AL
THE F OL· RTH STAGE L.<\R,·A.- ··These a re usually found on th e surface of t he mucosa of the stomach. The exes a re distinct. The female is 0·625 mm. long a nd t he <:esophag us is 1·1 mm. to 1·6 mm. long, a nd claviform in shape. The intes tine resembles the adult in test inc. The mouth opening. in all the specimens observed is unde rgoing change a nd the temporary buccal capsule is being replaced by a new one on the anterior end of th e reso phagus. The ovary is present as a long tube running forwa rd to almost the level of the beginning of th e intestin e. P oste riorly it b ecomes vacuola ted and join s a vulva , whi ch does not ye t comm uni cate with th e exterior. Th e a nus is present in its final position a nd is joined to t he a nal opening of the la rval sheath . Th(' sheath an d body have th c t:v·pical tri cuspi d tail. Th e male is a bout 0·65 mm. long. Th e diges ti,·e system is simila r to t ha t seen in the female. The male genita l t ube is present as a soli d mass running forward from the cloaca , whi ch it appears to join. The bursa. has ass umed its final form and spicules and accesso ry piece a re present. Th e la rval sheath is swollen posteri orl y , but contracts at its extreme tip to form a tricll spid a ppe ndix.
The Biology of Ollulanus. Early in the expe rimental work , it was found to be comparat ively easy to produce a stock infection in cats by t ransfe rring the fresh s tomach contents of an infected an imal to an uninfected kitte n by feeding . Th e question of the n a tural ex it of th e parasite was, h oweve r, not solved by t hese experiment s. I n mo t an imals on ly two normal routes wh ere by a parasite may lea'·e t he stomach can be found: (a) by pa sage with the fceces to t he exte rior; or (b) by remaining in the st0mach till after cleath , when it wou ld be eateE h~' some intermediate host or even by a definitive host. H.epeated sea rch of th e intestinal tract of all the infected cats in th is series of e:-.periments fail ed to reveal any t race of Ollulanus lan ·ce, a nd the first route did not see m to be t he norm al one in thi s case . Experiments with mice, fed not only on the stomach, but on the intestinal co ntents, were a lso uniform ly n egat ive. In the cat a third possible route may be considered, ,·i7. by emesis. T he cat is able to '·omit with such facili ty , and it does so with such regulari ty--o ften eat ing grass to cause emesis- that the action might al most be called a normal one. Th e paras ite, moreo ' ·e r, causes an in flammato ry or a catarrhal condition of th e gastric mucosa, and emesis, therefore, would be a natural sequal to this infection. MoreO\·er, cats will readily eat the vomit of other cats, especia lly if they a re hungr~· , and all natural infect ions of th is parasite \\·hich I ha\"e
THE LUNG WORM I
T
THE CAT
III
seen, have occurred in stray, badly-fed animals. Acco rdingly it was decided to test the possibilities of this route. A cat was infected by feeding on a n ollulanised stomach, a nd a few months la ter was inj ected subcutaneously with apomorphine (in preference to an oral emetic which might have affected th e parasite). The animal vomited in a few minutes, and a rapid examination of the vomit showed the presence of the third stage la rva. The mass was placen be fore a kitten, whi ch readily ate it. When this animal was destroyed a few months lat er, it was found to be heavily infected with Ollulanus. This suggests that infection m ay be produced by direct feeding of t he vomit of a n infected animal. Another cat was placed in the same cage as the first, which was observed to vomit occasionally, and it was given the opportunity of eating the \'omited m aterial. When it was destroyed some months later, it also was found to have acquired the parasite. Accordingly it seems probable th at emesis is at least one method of conveying the infection from one animal to another, and although it is not claimed that this is the on ly m et hod , so far no othe r is apparent. A fourth cat was infected with 10 larvee-·similar to those observed in the vomit-and when destroyed six months later, was found to have a very h eavv infection of fourth stage la rvee and adults of Oltutanus. During this }Jeriod it han been enclosed in a cage by itself and could not possibly have been infected from outside. It seem s extremely preba ble th a t this is due to continuOLls auto-infection from the animal's own vomit. At the sam e time, it is not possible to exclude entirely the con .. tillllOUS development of the ]Jarasite within the host, cS}JcciaJly when it is co nsidered that onl y a ve ry short time need necessarily elapse b etween the emi ssion of the la rvee i~l the vomit and their-ingestion by a nother host. Inmost other parasites a " time factor" outside thl' body of the de finitive host is in volved, a nd this seems to be wholly or partly a hsent in the case of Ottutanus. This parasite differs in several important respects from other parasites, n ot only in its peculia r habitat , but in bei ng vi\'iparous , ann in the Jarvee comple ting their prelimin ary moults within th e uterus of the female. It is accordingly not sa fe to gene rali se o n a nalogy fro m ot her forms having different biological cha racte rs . Fiilleborn has recently st udied Rhabditis bufonis, a parasite of the lung of th e frog, a nel he suggests tha t in this fo rm some substance is produced which wonld inhibit t he continuoLls development in the lungs . It is possible that sLlch a substance is also produced in t his form o r oth erwise there would be infections e\'en higher tha n those observed . Or it might be that thi s substance would only be produced after an opt imum concr n trat ion of ad ults in t he stomach h ad b er n reach ed.
112
THE VETERINARY JOURNAL
It is not possible either to prO\'e or dispro\'e eithe r o f these hypotheses at the present moment , a nd this cannot be done until all possibility of continuous a uto-infection can be elimin ated. The development of the parasite inside th e stomac h has not yet been elucidated , but seri al sec tion s of pa rts of the stomac h of several infected ca ts suggest the possibility of a deve lopment in the mucosa. CONTRoLs.- All the cats Llsed in these experiments were obtained as kitten three to fOLlr month s old from th e same source. At th e ~a me time a bout twice thi s number was obta ined for ot her expe riments , a nd these a nim als we re Llsed to control t he Ollul anlls experiments. In no case was this parasite fo und in any of the control animals, and this ma kes it practically ce rtain tha t the experimental cats were free from Ollulanlls when fed . The rea fter th rv were confined to cage,; a nd accidenta l infec tion from outside sO llrcrs rendered impossible. The present conception of th e life hi story of Oll1ltanlls tric'l/.spis is as follows. The egg ha tches in th e uterus a nd the la rva which emerges mou lts -in situ and its tail changes from a rounded to a typica l tricuspid one. The seco nd s tage larva develops into a third stage which is found outside t he fe male, but til(' exac t peri od at which it leaves th e mother is still unknown. Thi s form leaves the stomach in the vomit a nd is swa llowed by a new host. ill whi ch it develops into a fourth stage la r va and fin a lly th e typica l ad ult. Some part of thi s developm ent seems to take place in t he depth s o f the mucous membran e a bove the mu scu la ri s mucosa. It is possible that there a re other methods whereby the infrc ti vr lan'a mav leave th e host . but th rsl" have not yet been discove red. The geographi cal di stribution o f Ulllltanas tricll spis is not fully known. It was found in Ge rm any by Leuckart and in Switzerla nd hy Galli-Va lerio. Co bbold a lso reported it from Brita in , but th ere is no clear ev idC'lIce th at he eve r act ually aw thi s species, a nd probabh' his recorel should apply to .-l etllrosir oll{{yilfs abstnlslIs . Hall records its prese nce from " 'ashington, D.C. , hut it is not stated whether he is referring to the adult in the ca t or the larva in t he mouse. In the latte r case, hi s reco rd would, of course, refer to Miiller's speci e~. ~ e umann r.: ports t hat, although he searched \'ery carefully for Ollulan us in Fra nce . he was una.bl e to find it. The m orp ltological and bio logical studies d escribed in tlti s ar ti cle Ita ve occupied severa l years, and res ul ts have been publisheci in a numbe r of papers in tlw J ournal oj H dJllililholo[!y. Th ese papers a re lis t ed below a n d co ntai n fu'l acco u nts of th e ex per i me n ts toget he r wi tit refe re nces to " Ii th e previous p u blicat ion s. J I. 11 1'1111. I , 1\1 2:1, 1;; i - I Utl . 1\', 1926, ;j :!,60. \ ', Hl:n , 1-24 .
.I I. H elll!. \ ', 1927, .;;;-66.
Y , 1027 , (ii , SO. YI . Ifl28, 16;; · 1611 .
Th e illu s trations arc red uced from plates in th e,;c articles bv kind p er mi s ,i o ll of the Editor o f tlte j oum al of H elJllilllhologl'.
97
6~n~ral Jlrticl~ THE LUNG WORM AND THE STOMACH WORM IN THE CAT. By THOMAS W. M. CAMERON, M.A., Ph.D., D.Se., M.R.C.V.S., [ ect'urer and M ilner R esearch FelloZIJ in the Department of Helminthology of the London School of Hygiem and Tropical !VIedicine .
Introduction. IN 1865, Leucka rt found in the stomach of the domestic cat a minute bursate worm which he named Oll1llanus tric~tspis. H e found also what h e believed were the free la rva! of Ollula nus ; fonns which measured about 320". long by 15". wide, had a truncated oral extremi ty and a short tail whi ch end ed in a short S-shaped tip (PI. 1 (a)): t he ccsophagus was between one-third and one-ha lf of the total length of the intestine. A !though there are seldom more than t hree embryos inside th e female, larva! were usuall y found in large numbers throughout the whole intes tina l tract of the host, as well as encysted (in cysts · 15 to ·2 mm. in diameter) on ,·arious intern al organs. The cyst wall had a connective tissue-like structure of such thickness that it might b e three or four times the diameter of the enclosed s pace. This space was either filled by the tightly wound coils of the worm or with a clear liquid . 1£ p resent in la rge numbers in the lungs, these capsules caused the appearance of miliary t uberculosis- especially when surrounded by a n area of hepatisation . They might even be th e focus of a widespread inflammation which in one of his cases at least , led to the death of the cat. Embryos were not found in th e blood or muscles, hut in heavy infect ions were free in the bronchi. The encys ted embryos , unlike Trichinella, did Ilot continue their development , but gradually degenerated, and fmally came to resemble a n egg. Leuckart fed these e mbryos to a mouse a nd six weeks la ter found humlreds of them encapsuled in th e muscles- these forms being intermedia te in form between the free embryo a nd the fully developed Ollulanus. The capsules- about . 3 mm.- were not only found in th e rump muscles a nd cesophageal wall, hut also in the heart and in the loose connective tissue of the neck. The wall was it simple connective tissue one, surrounded by nodules and containing numerous gran ules which we re moved about by the movem ents of the larva (PI. 1 (b) ). The enclosed worm had increased in size and was about ·8 mm. long by ·04 mm . broad. The blunt end sh owed a retracted chitinous
98
THE VETERL'\.\RY ]OLR\AL
disc which, from analog.\-, might be taken as the tirst indication" (" the future mouth, The cuticle was thicker and ringed. I{oune! th( lip-like projections were a few papilla-like outgrowths, The tail was simple and pointed, The in testine had not changed except that tJw pharynx was comparat ively shorter and showed a muscular structure The intestine was brown and towards its middle the ~Iighth' enlarge(t bean-shaped gcnital primordia could be seen, He was unable to decide whether these stages had reached maturity but going by the results of an experiment, he considered that furthe r dCH'lopment in the mouse was possible. ,-\n infectcd mouse was fed to a cat and eight days later the worms were lTco\'ered from i t unchanged, but in the cGecum and rectum, not the stomach, As only a few were found, it was belie\'ed that they were cn route fo r the exterior and Leuckart considered that all the conditions necessary for further de\'Clopment were not present.
Platl' I .
(a) Embryo of Oltulanlls tricu , pis (after LClIckarl, 1R67) (b) Fn capslIJat.-cl cmhn'o in mllscles of mOllsP (after Lell c ka,·t, 1;;67)
Only one other experiment is recorded. Two young rat,; were fed with the stomach wall of a cat infrcted with Ollulanns laJT<-e , and after 2 ~ hours and three clavs respecti\'cly, the majority of the introdnced worms were rrco\'Cred ali\'e and undamaged in the stomach, Cobbold in Britain was also studying the parasite, although he preferred to lise the namc 01 ulanus in stead of the more correct Ollulanus, In discussing the probable life histories of the lung \l'orms ill general, Cobbold (1875) drew attention to I.euckart's belief that " all these strongyloides required a change of hosts bdore they can take up their final abode in the sexually mature state . This he infers especially because their respective embryos display characters very similar to those exhibited by Olulanus," He considered the question fully in a paper read before the Quecket t }Iicroscopical Club in 1885. He stated that his f1rst arquaintane,
THE LUNG
~,YORM
IN THE CAT
99
with the larvce of Olulanus was made about 35 years previously, when a young cat in his room suddenly rushed about and finally fell dead, asphyxiated. While yet warm, it was dissected and its lungs were found to be swarming with nematode larvce. Drawings were made, but no specimens were preserved, and it is not stated whether any adults were seen in the stomach. He then briefly recapitulated Leuckart's work on the subject, and described a case which he had seen with Mr. Gay, a surgeon, in which a family, together with their donkey and cat, had suffered from a condition which was suspected to be Trichinosis. On investigation, no evidence of this was found, but the lungs of the exhumed cat were
c A
D
Plate 2.-(a), (b), anrl (e), Eggs of St1'nngylus pusillus (a fter H.n.illipt). (d) Free embn'o (after Railliet). (e) Bursa of Strongylus pusilhts (after Muller). (f) and (g) Posterior ends of embryos (after MUller)
found to be swarming with" Nematoids." Cobbold considered that this was a case of "Olulanosis," and states that "Whatever interpretation be put upon the human outbreak, the coincidence of the occurrence in man of an affection symptomatic of trichinosis, found in association with a trichinoid affection in an animal which proved olulaniasis, was both curious am! instructive," No subsequent work on the subject seems to have been done, excepting some negative experimental attempts at infection by Galli-Valerio in 1921. Meanwhile, in 1890, Mi.iller described from the cat in Germany a new form of lung-worm which he called Strongylus pusill1ts, and Eailiiet (1898) proposed the new specific name of S. abstrus1/S instead :
100
THE VETERINARY JOURNAL
Later (1907) H.ailliet a nd Henry transferred thi s species to the gen us Synthetocaulus, a genus recently shown by Leiper to be a synon ym of Protostrongylus. It is unnecessary to recapitulate MUller's desc ription of this parasite. The origi nal figures a re reproduced (PI. 2) , which show that Leuckart had C0nfused two separate a nd distinct parasites in his work. This is furth er confirmed in t hf' account of the life histories which follows. Both of these parasites have been mentioned in \'etcrinary literat ure since the dates of thei r discovery, but nothing has been added t.o our knowledge of their morphology a nd life history.
The" Lung"Worm" of the Cat. The lengt h is approximately 4 mm . in the male a nd (1 mm . in the female. The mouth ope ning is surrounded by six inconspicuous papilla:. a nd opens directly into th e short almost cylindrical (eso ph agns. which is about 0·25 mm. long. The m ale has a sma ll but well-formed bursa, which is complete a nd undivided . The cuticul a r hursal supports seen in Protostron/!,yllls a re absent. The spicules a rC' similar and eq ual, measuring 0·075 mm. in length . Each consists of a cuticnla r t ube, which is swollen a nteriorly, but terminates in a blunt point. To each is a tt ac h ~d a voluminous sheat h which is tra nsversely striated . but which is without the supporting lingers Sf'en in Protostrongylus. Th e female has a double genital system. The tail is bluntly pointed and the re a re no papillcc present . Th e an us is 0·04 mm . from the t ip of the tail and t he rectum is ve ry short. The ndva is (). 09 mm. {rom the a nus a Ild comm un icates wi th a long single vagin a, which in turn joins th e two parallel uteri . The \'agina is abo ut 1·5 mm . long and contain s unsegm ented eggs measuring abo ut 80/J, long by 70 fl broad. This parasite was originally placed in the ge nus IJrotostrongyllls by Kamensk)" and in the genus Syntf1etocallllls (whi ch is a synonym of Protostro ngylus) by Rai llid and H enr~T. but it obv iously docs not belong to the same genus as Protostrollgyllls YlIJesce1-ls : and accord ingly the new gC'n us Aellirostrongyllls has DC'en creatC'd b~' the writer for its rrception. Its correct namc is the refore A elllrostron{!yllls (IhstmslIs.
The Morphology of the Larva in the Cat. The eggs , laid in the ah'coli and parenchymatous tissue of the lungs, hatch il1 situ. and the la n '
T HE LUNG WOR M IN TH E CAT
] 01
s wallowed and pass out with the freces. From the time of hatching until the time that they leave the body in the freces , no apparent c hange in morphology takes place. The larvce have been allowed to hatch in the dead body of the female A elurostrongylus, so that there is no possibility of this heing the larval stage of any other species of worms. The larva is about 0·36 mm. long and 0·015 mm . broad (Plate 3). The mouth opening is simple and is surrounded hy six low papillce. The cuticle is covered with very fine transverse striations and a douhle lateral line is seen, suggesting that the first larval stage is omitted in this species. The cesophagus is 0·14 mm. long and has a central, as well as a posterior, swelling. The anterior part of the cesophagus, t('rminating at the central bulb , i largely muscular ; th(' posterior portion is distinctly glandular. The anterior swelling has a diameter of about O' 006 mm., the posterior swelling, about O'Ol mm., and the narrow part, 0·003 mm. The cesophagus communicates with the mouth opening by means of a cuticular buccal tube which seems to be continuous with the cesophageal lumen. This tube is dila ted centrally, but converges slightly towards its . Uurostrongylus abstmsus. Pla te 3.- 0 vum a mI larva as found in the lungs and intestine anterior junction with the inof a cat, ~ h owin g th e varia tion in ta il fo rm . fl eAcd cuticle. The intestine is very granular and measures about O· 19 mm . in length . It is connected with the anus by m eans of a short cuticular rectum . JlIst posterior to the anu<; i<; a small protuberan ce which is inconstant in siz(' , but is always present . The anus is about 0·03 mm . rrom the tip of the tail. The tail is very characteristic and carries a n undula ting appendix a nd normally a dorsal proj ec tion: these vary very considerably in s ize and relative position .
] 02
THE VETERI NARY J OURNAL Biology of the Larva.
Althoug h la n '
THE L NG WOl.{M I N THE CAT
103
were fou nd to be negative, so far as could be ee n. All these experiments were full y controlled by keeping mi ce o f the same origin and age, uninfected with la rva' of Aelurostrongyhts: in none of t hese was any extra-intestinal parasite ever found . In this way, 21 control mice were examined . ~fi ce were fed in batches: (a) by feeding on infected embryo-bearing lungs; or (b) by feeding with la rva' isolated from lungs or intestine or stomach placed on moistened biscuit or bread. Care was ta ken to see tha t all the ma terial was eaten, but it was no t possible to say if every mouse in every ba tch had swallowed larva'. It is, th erefore, impossible to say whether the six negative results recorded aboye were due to not being infected , or were slight in fec tions overlooked , or we re really failure . Sufficient positives were obta ine d, however, to ma ke it certain tha t the larva' described below arc really furt her s tages in the developmen t of A elurostrongyltts.
The Infective Larva.
., 1
\ \
'J ,
._
'~t>~~ . - . ,.
.
,, -
.TluYo;;/ro l1[!)'lus abstrusus . Plate 4.- L
It was fo und t hat t he most convenient way to fi nd if a mouse was infected was to pin the anima l on a board with its ;:l.bdomin al surface upward. The skin was then
;~::C~~dt~:ct~~~n~~~~ s~;~
underlying areola r t issne examined T he worm-con.
.
tain ing cysts we re often "isible to the naked eye, as " bubbles" lying superfi cial to the muscles of the leg. Whether so visible or not, a piece of this tissue was fl'Il1o' -ed with c urved scissors and placed between two slides and examined microscopi cally. Tn this way material was obtained for the follo wing description. If the mouse proved to be infected the remainde r was fed to a kitten. The cysts are about 0·3 mm . in diam eter, a nd ha\-e a thin fibrous \I-a ll. They arc filled with a yellow granular or caseous materi al in th l' centre o f which the larva is seen coiled on itsel f. \Vhen removed from the cys t the larva is found to be 0·725 mill . long (Plate 4) a nd about 0·025 mm. in t hicknes. It is finely striated trans\·ersel\-. The <:esophagus is now 0·21111ll. long, 1·.e. the ratio
L04
THE VETERI NARY JOURNAL
of the length of the <:esophagus to the body length is 1 : 3·5; whereas in the earlier larva it is about 1 : 2·5. The central bulb has disappeared a nd the posterior bulb i rela tively smaller. The whole <:esophagus is mu ch more muscula r a nd less gra nula r th a n in the previous stage. The mou th is a simple pore communicating with the <:esophag us by means of a cuticula r buccal tube. The buccal tub~ consists of a more highly cuti cula rised a nterior portion, and a less high ly cuti cularised posterior portion whi ch communicates directly with the lumen of the <:esophagus. The anterior portion has a small number of rugce on its exteri or surface , while the interior surface is smooth . The intestine is about 0·35 mm . long and is very gra nul ar. It communi cates with the a nus hy means of a straight rectum abo ut 0·02 mm. long. Th e a nus is situa ted a hout 0·04 mm . from the tip of the tail. The tail is bluntly pointed . Towa rds its tip, the body narrows rather suddenly and the posterior portion is s urro unded by deep striations whi ch give it a errated a ppearance. There is n ow no trace of th e undul ating appendix seen in the previous stage (Pl at e 3) .
Experiments on Cats. The experimental work on cats fell into two groups: (a) feeding with free la rvc.e from othpr ca ts; a nd (b) feeding with encysted la rva:' from mice. (a) Four cats were fed on various dates with the larvce isolated from the lung tissue and from the intestine. The first two we re feel from tree t infections which were contaminated with OUulantts tricuspis. In these two animals the infec tion with th e latter parasite was demon trated on post-mortem examination , bllt in all four no evidence of A elu,rostrongylu s could be seen . (b) Seven animals were fed at various da tes with mice which contained encysted la rvce as elpscribed above. Two of these ani m al .~ died from distemper shortly a fter infec ti on, and no evidence of lung infection could be seen. In tr.e ot her five , howeve r . Ae!1Irostrongylus was found in the lungs. Habitat. The exact habita t of the adults has never been described. There a re four possible localities in the lungs where parasitic worms can live: in the bronchi or bronchioles ; in t he alveoli; in the interstitia l tissue; or finally , in the blood vessels of the lung. During a stud y of th e lesions provo ked by t his parasite in the lungs of the cat, one was struck by two peculiar facts. First ly, adults were never seen in severa l hundreds of secti ons exam ined. although
THE LUNG WORM IN THE CAT
105
eggs and la rvce were plentiful. The adults were only found in teased (The ections we re mainly prepared from marginal specimens. portions of the lung.) Secondly , the eggs in varying stages of development were eve nly di stributed throughout the lung a nd were not isolated in any particular a rea. These facts suggested the possibility of a blood distribution of the ('ggs, and th e blood stream as the norm al habitat 0f th e ad ults. An infection in a kitten was diagno ed by the presence of the cha racteristi c larvce in the fceces. Th e vessels between the heart a nd the lung were th en ligatured close to each of th ese organs, but without in a ny way interfering with them . Th e ligatured portion of the vessels was then removed, opened in saline and the contents shaken out. Fully adult male a nd female specimens of Aelttrostrongylus were found in these vessels. The lung itself wa then removed from the body, and still othe r adults were recove red in th e la rger branches of th e pulmonary vessels. Although th ere a re ma ny essential details of the life history of . Ielurostrongylus abstmws still remaining to be elucid ated- more especially th e development of the la rva in the mouse a nd t he development of the ad ult in the cat- it may be sta ted tha t th e essenti a l outline of its life history is as follows ;The adult parasites become mature in t he p ulmon a ry vessels, and th e female deposits her la rge, thin-shelled eggs in the blood stream. They are mechanically carried to the capillaries of t he lung, where their progress is arrested , a nd where the unsegmented ovum develops into the characteristic la rva. When m at ure, the la rvce force their way thro ugh the t hin -walled tissue into the alveoli , a nd in this way reach th e exterior afte r trave rsing the bronch ioles, bronchi , trachea and a limenta ry tract. Occasionally in v ery young animals a nd with \'c ry heavy in fecti ons, t he eggs th emselves ru pture the capillaries and, escaping in a n undeveloped condi tion into the a lveoli , then continue their development. The fceces are eaten by mice and the la rva migrates to various situations a mong the mu scles and in the subcuta neous tissue, where, within three weeks, it assumcs a n infecti ve, encysted form . It may rcmain v iablr for a t Irast a year in this situa tion. If the mouse is now eate n by a cat , th e la rva e capes from the cy t a nd , reaching the Illngs, within six wee ks becomes a ma ture egg-laying ad ult . vVhile the prese nt writer has neve r seen la rvce outside of th e respirato ry or alim enta ry t racts, Leucka rt has described them from \',uious parts of th e boely. Leuckart beli eved that he was dealing with the lan 'ce of OIlIf/al1l1s , hut in that he was unrloubterll y mistaken.
106
THE VETERINARY JOUR:\AL
Hi s infections were, unknown to him , mix cd ones, of both tl1(' lu ng a nd the stomach forms. Recently , Professor Leiper has becn cond uct ing a scrics of experiments with Trichinella spiralis , a nd he was struck with t he unusual appeara nce of t he cysts· in cats caused by the la r va of this species. I nstead of th e usual lemon-s haped cyst so characte ristic of mice a nd pigs, the cyst was almost sphcrical, altho ugh the infection was originally from rats with" normal" cysts. This is obviously because the host reaction in t he cat (and exam ina tion of cysts fro m ot her ca rni vores, showed that it is probably a 'gro\l p rcaction) differs fro m that of thc roden t or the pig, and is not due to the rc hein g present a different spcc ies of Trichinella. These cysts'measurc about 0·2 mm. in diameter a nd corrcspond to Leuckart' s description , cxcept that th e cyst wall is not so thi ck. As rodents a re na t urally eaten by cats, it is possible t hat Leucka rt's an imal in add ition to suffering from A elurostrongyl1ls and OUulanu s, also suffered from a "Frichinella infect ion ; hut their distribution docs not lend support to thi s hypo th esis, as they occurred in situations wherc Trichinella larvee rarely a rc found . From the aboye discussion, it would seem morc probahle th a t t hey were la rvee whi ch had- eith er as o"a or la r\'<:e- passed through th e pu lmonary capill a ry n etwork and so bee n ca rried to th e \'a rious organ s by the blood stream. The encystment would bc t he na tural reaction of the host tissues to any foreign body. The geog ra phical d ist ri bution of .-1 el llrostroll[;yl ll s abstrtl slI s is in completely kn own. It has bee n reported from Ge rma ny, Fran ce, a nd from Nort hern Italy and Switzc rla nd . It h as no t pre\'iously bcc n recorded frol11 Britain, but th crc is li ttlc doubt tha t the forms sec n b\" Cobbold and Stirli ng should be refe rrcd to thi s spccics.
Ollulanus tricuspis, the Stomach- Worm of the Cat. The adult worms li\"e on th e surface of t he stomach a nd in th e acini of thc stomach glands. In ve ry hca"y infec tions, th ey m ay evcn bc fo und in th e first in ch of t he duodenum , b ut t he:-" h a \'c ne \'er becn fo un d bcyond th e d uodenal fl ex ure. This is a nalogous to thc sta te of aftairs see n in other stomach worms in other a nimals. Thcir presence on t hc surfacc of t hc gastric mucosa ca uses th c prod uct ion of a t hick glai ry mucus whi ch assists in kecping t hcm in posit ion. Th ey a p pear to bc \'e ry let ha rgic in t hcir mo\·cme nts . I n t hc frcsh statc the parasitcs a rc colourless, anct a rc genc rall l' fo und with thc hcad e nd coiled on itsel f. Thcy a rc very minutc , t he male mcasuring only ·7 to ·8 mm. ill lcngt h, with a n avcrage breadth of . 03;) mm.; whil c thc fcma le i,; ·8 to I mm . long, a nd about ·01 mm . broad .
THE LUNG WORM I
THE CAT
107
The cuticle is faintly striatcd transversely and more conspicuously striated longitudinally. THE ANTERIOR EXTREMITY.-A small buccal cavity is present con taining no t eeth, cutting plates, ~ or similar structures. The cavity is formed by a reflection of the I . cuticle, and in optical section is almost spherical (Plate 6). The lateral diameter is . 004 mm., and its antero-posterior diameter is ·005 mm. The cesophagus, which is about . 2 mm. long, i only slightly swollen posteriorly. The cesophageal muscles are poorly developed. THE MALE.- The bursa (Plate 5) is undivided , and is open only Plate [) -Ollulanus tricusp ·is. Titil of m ale on the ventral side. O/tu/.1nlls triCltspi s. (a) Dorsa l ray of The spicules are equal in length mal e bur'ia, (h ) SpIcule (c) taIl of femp-le. (about ·05 mm. ) and are bifurcated , onc bifurcation being sharp and the other rounded . Th cre is no accessory piecc. THE F E ~IALE. _ . The vulva (Plate 6) is a prominen t structure si tna tcd in the posterior reg ion of th e body, whi ch it dividcs in the ratio of approx imately fi ve to one. The \'llh'a opc ns into a short \'agina, wh ich is continued anteriorly as a singlc uterus. Thc junction of uteru s a nd vagina is smrounded by a granular mass in .J the immature female. This disappears in th e mat urc f(,male. There is no ovejector. P late 6.- 011utallus triCltsp is. Gravid fe. The si ngle ovary originates about male showing egg, developing first st age and developed first stage larva. tl1 e. Ie\.e I 0 f th e cesop h agea I buIb , larvit A second stage la rva was also removed and inse nsibly joins thc nterus: by dissection fro m t his sprr imen , hut it is not sh own i n th e drawing. t I1C o\'a are very I a rge an d g ran ular. ,As tbe worm becomcs older, the ovary becomes confined to th e anterior part of the body, the remainder of whi ch is occupied by the
'.
~
~.
~
' 01 UUD
trim
J08
THE VETERINARY JOURNAL
intestine and one to three very large larv::e (. 3 to ·35 mm. long). The anu is situatecl abo ut ·03 to ·04 mm. from the posterior end. The tip of the tail has typically three" cusps" or teeth ; but occasionally one or two small extra cusps are found. GENERAL EVOL UTIO N.- The large gran ular egg formed in the single uterus grad ually develops into a larva, whi ch escapes from the thin eggshell , and subsequently moults--still inside the female- resulting in a form with tricuspid tail. The next stage seen is free in th e stomach of the cat. Fin ally, a lso free in the stomach , i~ found a stage comparable with th e fourth stage larva of the ot her Strongyles_ The sheath o f this form , in both sexes, carries a typical tricuspid tail. All t he forms found free in th e stomach of th e at- except the ad ult m ale- possess a typical tricuspid tail and bear no resemblan ce whateve r to the larva of A elurostrongyl·us abstntsus_ TH E FIRST LARVAL STAGE.- This form is first seen in side t he distendeo egg-shell (Pl a te 7), but ultim ately com es to lie free in the uterus of the female. The descripti on of this a nd the next s tage has been prepared from specimens di s ected from the uterUS of gravid females. This larva differs from all subseq uent stages ill possessing a round blunt tail. It is 0-35 mm . long and about 0-002 mm. in thicknes _ The mouth opening is a simple pore, apparently not surrounded by circumoral papillce. A distinct bu cca] tube, somewhat dilated centrally, connects the mouth pore with the <:esophagus. T he (esophagus is about 0,] 25 mm . long and is of the usnal type seen in young strongyle larv
THE Ll NG WORM I
THE CAT
109
length with an ce ophagus 0·0125 mm. long, have been dissected from gravid females. THIRD STAGE LAHVA .- This form measures 0·5 mm. in length with a width of about 0·022 mm . Th e sk in is fin ely st riated. The mouth openi ng i impl e, but it communicates with u. V-shaped buccal cavity, th e straight sides of which a re cuti cularised. The (esophagus whi ch sti ll has a sli ght constriction, is 0 ·15 mm. long with a maximum width of 0·012 mm. Th e inte tine is yery granul a r
Plate
j
(Icft to right) ..- DeveJopi ng first stage larva; fully d('\"(: loped first stage ; second stagc: third or infective stage.
a nrl measures 0·35 mm . in length. Towar~ls the posteri or portion of the intestine, a nd running parallel with it, is seen the elongated genital rudiment. Th ere is, of course, still no trace of a gen i tal opening. Th e a nus is 0·03 mm . from th e tip of the tricuspid tail. This form , unlik e the adults, usually lies curved like a n arc, and is found , 110t only in the sa me positi on as th e adu lts. b11t free in the cavitv of th e stom ac h.
110
THE VETERINARY TOt:RK AL
THE F OL· RTH STAGE L.<\R,·A.- ··These a re usually found on th e surface of t he mucosa of the stomach. The exes a re distinct. The female is 0·625 mm. long a nd t he <:esophag us is 1·1 mm. to 1·6 mm. long, a nd claviform in shape. The intes tine resembles the adult in test inc. The mouth opening. in all the specimens observed is unde rgoing change a nd the temporary buccal capsule is being replaced by a new one on the anterior end of th e reso phagus. The ovary is present as a long tube running forwa rd to almost the level of the beginning of th e intestin e. P oste riorly it b ecomes vacuola ted and join s a vulva , whi ch does not ye t comm uni cate with th e exterior. Th e a nus is present in its final position a nd is joined to t he a nal opening of the la rval sheath . Th(' sheath an d body have th c t:v·pical tri cuspi d tail. Th e male is a bout 0·65 mm. long. Th e diges ti,·e system is simila r to t ha t seen in the female. The male genita l t ube is present as a soli d mass running forward from the cloaca , whi ch it appears to join. The bursa. has ass umed its final form and spicules and accesso ry piece a re present. Th e la rval sheath is swollen posteri orl y , but contracts at its extreme tip to form a tricll spid a ppe ndix.
The Biology of Ollulanus. Early in the expe rimental work , it was found to be comparat ively easy to produce a stock infection in cats by t ransfe rring the fresh s tomach contents of an infected an imal to an uninfected kitte n by feeding . Th e question of the n a tural ex it of th e parasite was, h oweve r, not solved by t hese experiment s. I n mo t an imals on ly two normal routes wh ere by a parasite may lea'·e t he stomach can be found: (a) by pa sage with the fceces to t he exte rior; or (b) by remaining in the st0mach till after cleath , when it wou ld be eateE h~' some intermediate host or even by a definitive host. H.epeated sea rch of th e intestinal tract of all the infected cats in th is series of e:-.periments fail ed to reveal any t race of Ollulanus lan ·ce, a nd the first route did not see m to be t he norm al one in thi s case . Experiments with mice, fed not only on the stomach, but on the intestinal co ntents, were a lso uniform ly n egat ive. In the cat a third possible route may be considered, ,·i7. by emesis. T he cat is able to '·omit with such facili ty , and it does so with such regulari ty--o ften eat ing grass to cause emesis- that the action might al most be called a normal one. Th e paras ite, moreo ' ·e r, causes an in flammato ry or a catarrhal condition of th e gastric mucosa, and emesis, therefore, would be a natural sequal to this infection. MoreO\·er, cats will readily eat the vomit of other cats, especia lly if they a re hungr~· , and all natural infect ions of th is parasite \\·hich I ha\"e
THE LUNG WORM I
T
THE CAT
III
seen, have occurred in stray, badly-fed animals. Acco rdingly it was decided to test the possibilities of this route. A cat was infected by feeding on a n ollulanised stomach, a nd a few months la ter was inj ected subcutaneously with apomorphine (in preference to an oral emetic which might have affected th e parasite). The animal vomited in a few minutes, and a rapid examination of the vomit showed the presence of the third stage la rva. The mass was placen be fore a kitten, whi ch readily ate it. When this animal was destroyed a few months lat er, it was found to be heavily infected with Ollulanus. This suggests that infection m ay be produced by direct feeding of t he vomit of a n infected animal. Another cat was placed in the same cage as the first, which was observed to vomit occasionally, and it was given the opportunity of eating the \'omited m aterial. When it was destroyed some months later, it also was found to have acquired the parasite. Accordingly it seems probable th at emesis is at least one method of conveying the infection from one animal to another, and although it is not claimed that this is the on ly m et hod , so far no othe r is apparent. A fourth cat was infected with 10 larvee-·similar to those observed in the vomit-and when destroyed six months later, was found to have a very h eavv infection of fourth stage la rvee and adults of Oltutanus. During this }Jeriod it han been enclosed in a cage by itself and could not possibly have been infected from outside. It seem s extremely preba ble th a t this is due to continuOLls auto-infection from the animal's own vomit. At the sam e time, it is not possible to exclude entirely the con .. tillllOUS development of the ]Jarasite within the host, cS}JcciaJly when it is co nsidered that onl y a ve ry short time need necessarily elapse b etween the emi ssion of the la rvee i~l the vomit and their-ingestion by a nother host. Inmost other parasites a " time factor" outside thl' body of the de finitive host is in volved, a nd this seems to be wholly or partly a hsent in the case of Ottutanus. This parasite differs in several important respects from other parasites, n ot only in its peculia r habitat , but in bei ng vi\'iparous , ann in the Jarvee comple ting their prelimin ary moults within th e uterus of the female. It is accordingly not sa fe to gene rali se o n a nalogy fro m ot her forms having different biological cha racte rs . Fiilleborn has recently st udied Rhabditis bufonis, a parasite of the lung of th e frog, a nel he suggests tha t in this fo rm some substance is produced which wonld inhibit t he continuoLls development in the lungs . It is possible that sLlch a substance is also produced in t his form o r oth erwise there would be infections e\'en higher tha n those observed . Or it might be that thi s substance would only be produced after an opt imum concr n trat ion of ad ults in t he stomach h ad b er n reach ed.
112
THE VETERINARY JOURNAL
It is not possible either to prO\'e or dispro\'e eithe r o f these hypotheses at the present moment , a nd this cannot be done until all possibility of continuous a uto-infection can be elimin ated. The development of the parasite inside th e stomac h has not yet been elucidated , but seri al sec tion s of pa rts of the stomac h of several infected ca ts suggest the possibility of a deve lopment in the mucosa. CONTRoLs.- All the cats Llsed in these experiments were obtained as kitten three to fOLlr month s old from th e same source. At th e ~a me time a bout twice thi s number was obta ined for ot her expe riments , a nd these a nim als we re Llsed to control t he Ollul anlls experiments. In no case was this parasite fo und in any of the control animals, and this ma kes it practically ce rtain tha t the experimental cats were free from Ollulanlls when fed . The rea fter th rv were confined to cage,; a nd accidenta l infec tion from outside sO llrcrs rendered impossible. The present conception of th e life hi story of Oll1ltanlls tric'l/.spis is as follows. The egg ha tches in th e uterus a nd the la rva which emerges mou lts -in situ and its tail changes from a rounded to a typica l tricuspid one. The seco nd s tage larva develops into a third stage which is found outside t he fe male, but til(' exac t peri od at which it leaves th e mother is still unknown. Thi s form leaves the stomach in the vomit a nd is swa llowed by a new host. ill whi ch it develops into a fourth stage la r va and fin a lly th e typica l ad ult. Some part of thi s developm ent seems to take place in t he depth s o f the mucous membran e a bove the mu scu la ri s mucosa. It is possible that there a re other methods whereby the infrc ti vr lan'a mav leave th e host . but th rsl" have not yet been discove red. The geographi cal di stribution o f Ulllltanas tricll spis is not fully known. It was found in Ge rm any by Leuckart and in Switzerla nd hy Galli-Va lerio. Co bbold a lso reported it from Brita in , but th ere is no clear ev idC'lIce th at he eve r act ually aw thi s species, a nd probabh' his recorel should apply to .-l etllrosir oll{{yilfs abstnlslIs . Hall records its prese nce from " 'ashington, D.C. , hut it is not stated whether he is referring to the adult in the ca t or the larva in t he mouse. In the latte r case, hi s reco rd would, of course, refer to Miiller's speci e~. ~ e umann r.: ports t hat, although he searched \'ery carefully for Ollulan us in Fra nce . he was una.bl e to find it. The m orp ltological and bio logical studies d escribed in tlti s ar ti cle Ita ve occupied severa l years, and res ul ts have been publisheci in a numbe r of papers in tlw J ournal oj H dJllililholo[!y. Th ese papers a re lis t ed below a n d co ntai n fu'l acco u nts of th e ex per i me n ts toget he r wi tit refe re nces to " Ii th e previous p u blicat ion s. J I. 11 1'1111. I , 1\1 2:1, 1;; i - I Utl . 1\', 1926, ;j :!,60. \ ', Hl:n , 1-24 .
.I I. H elll!. \ ', 1927, .;;;-66.
Y , 1027 , (ii , SO. YI . Ifl28, 16;; · 1611 .
Th e illu s trations arc red uced from plates in th e,;c articles bv kind p er mi s ,i o ll of the Editor o f tlte j oum al of H elJllilllhologl'.