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Studies on the Pathogenesis of Infection with Hyostrongylus Rubidus (Nematoda). The Effects of Levels of Infection of up to 150,000 Infective Stage Larvae on the Growing Pig
Br. vet.
J. (1972), 128, 147
STUDIES ON THE PATHOGENESIS OF INFECTION WITH HYOSTRONGYLUS RUBIDUS (NEMATODA). THE EFFECTS OF LEVELS OF INFECTION OF UP TO 150,000 INFECTIVE STAGE LARVAE ON THE GROWING PIG II. BLOOD STUDIES By 1.
J.
LEAN,
1. V.
HERBERT, AND
J.
B.
CASTELINO
Department of Agricultural and Forest Zoology, University College of North Wales, Bangor
SUMMARY
Colostrum-deprived specific pathogen-free (S.P.F.) and conventionally reared animal disease growing pigs were experimentally infected with single doses of up to 150,000 H. rubidus infective larvae. The following haematological indices were studied: mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration, total iron binding capacity and total white cell counts. No deviations from normal values occurred which suggest blood deficit. Differences between uninfected and control animals were not statistically significant and such slight differences as there were persisted for a very short period of time. INTRODUCTION
The nematodes of the Trichostrongylidae have often been incriminated in effecting blood changes in their host animals, an oligocythaemia being commonly found. The anaemia is induced either by a continual removal of host blood or by the parasite's utilizing some nutritive factor necessary to the host's blood production, or by the parasite's producing conditions in the host under which other organisms can thrive, or as a result of malabsorption or abnormal gut enzyme activity which in turn would affect formed elements of the blood. Recorded data involving infections with the Trichostrongylidae of ruminants shows some extremely varied results, which suggest that the "condition" of animals at time of infection is of importance in relation to the subsequent pathogenesis of infection as demonstrated by the blood. Anaemia has been observed in the field in both young pigs and sows which have also been shown to harbour Hyostrongylus rubidus. Gerber (1968) and Kendall, Thurley & Peirce (1969) found no change in the blood picture when following the course of single experimental infections of up to 4000 larvae. The present experiments are a more extensive study of blood changes, including information on infection in animals of different ages kept on different diets, and infected with single doses of up to 150,000 larvae. The effect of a single reinfestation with 20,000 larvae is also detailed. The animals used in these trials were some of those used in the nutritional studies which have been previously reported * and correspond to
BRITISH VETERINARY JOURNAL, 128,3
Trials I, 3, 4 and S. Reference should be made to Lean, Herbert & Castelino (1972) for full experimental details. MATERIALS AND METHODS
Four groups of Large White and Large 'White cross Landrace conventionally reared minimal disease growing pigs were infected with single doses of H. rubidus larvae. Blood samples were taken from the ear veins of animals in Trial 1 on alternate days, once the day before infection and then following infection for the prepatent period of 20 days. The animals were weaned at patency to avoid possible infection of the sow. Sufficient blood was taken to determine packed cell volume (p.c.v.), and total white cell count (w.b.c.). The animals in Trial 3 were bled weekly for 12 weeks starting one week before infection. Blood was collected by tail snipping. In Trials 4 and S the animals were bled from the anterior vena cava, in Trial 4 at weekly intervals and Trial S on alternate days. Heparin was used as an anticoagulant in this technique and EDTA in the tail snip method. In Trial I, blood was collected directly into heparinized microhaematocrit tubes, and dilution pipettes. P.c.v. was measured on a Hawksley microhaematocrit, total haemoglobin percentage (Hb per cent) by the cyanomethoglobin method in an EEL haemoglobinometer, and total red blood cell (r.b.c.) and w.b.c. were determined on a Coulter electronic counter. Calculation of mean cell volume (m.c.v.), mean cell haemoglobin (m.c.h.), and mean cell haemoglobin concentration (m.c.h.c.) were made as described in Dacie & Lewis (1963). Additionally, serum iron, and total iron binding capacity (t.i.b.c.) were determined on samples taken from Trials 4 and S by a method derived from the work of Neth, Schafer, Dilly & Lack (1963), Lauber (196S) and Bambach (1966) by Schweizerhall Chemicalst. In this method bathophenanthroline disulphonate is used as the colour reagent. RESULTS
In Trial 1 there was an increase in p.c.v. over the first 6 days of the experiment, and the increased levels persisted throughout the infection period. This occurred in both infected and non-infected animals. The mean w.b.c. counts for infected and non-infected animals were similar, with the mean readings for the infected animals being slightly higher throughout the recordings. In Trials 3 and 4, where animals were bled weekly, r.b.c. counts for the noninfected animals tended to be slightly higher than those of the infected animals, whereas w.b.c. counts, Hb per cent and p.c.v. values showed no difference (see Lean, 1969). The observations in Trials were on an alternate day basis (Fig. I) for the first 30 days of a single large infection (150,000) and show no difference between infected and non-infected animals. • See Part I, p. 138. t Unicam Limited, Cambridge.
H. RUBIDUS INFECTION IN THE PIG
%
:~ ~
A.
35 -
Hb%
149
, paint of Infection
-
~._ ';II""~-==i:---===i:-==~-&::::-::::::J.t:--::::::::.e:=-i-~~-:::t..>-oe
B.
14 13 12
.-e_
II
9 8xl0 6 7
'0
C.
r·-·-·-"e=~~_·~·_i_~
:~"O'r:-: o
2
4
= 6
8
10
12
1416
18
20
22
24
26
28
30
Days
Fig.
I.
Group mean blood values of trial 5 animals. A= B= C= D =
o •
Packed cell volume, percentage. Haemoblobin percentage. Red blood cells. White blood cells. 0 Non-infected. • Infected; 150,000 larvae.
Calculations of m.c. v., m.c.h. and m.c.h.c. were made on the data from Trials 2, 3, and 4. No deviation from normal appeared in the derived values to suggest an anaemic condition. Serum iron and t.i. b.c. of serum determinations carried out on trials 4 and 5, revealed no trends in the data which might indicate a blood deficit (see Lean, 1969). DISCUSSION
Baker & Douglas (1966) discussed the alterations which occurred in the erythron during the course of nematode infection, paying special attention to the effects caused by trichostrongyles which infect ruminants. Their report indicated that the effects of different worm infections vary greatly and are related to factors such as age, nutrition, and management of the animal, in addition to the size of infection. Occasional reports of hyostrongylosis refer to symptoms of anaemia in infected animals (Nicholson & Gordon, 1959; Dodd, 1960; Davidson, Murray & Sutherland, 1968). Signs of blood loss such as tarry faeces are also reported and it seems possible that such loss may be brought about either by the mechanical activity or the feeding activity of the worm, for Larsen (1967) has
BRITISH VETERINARY JOURNAL, 128, 3
demonstrated the presence of erythrocytes in the worm's gut, which shows that some blood is ingested even if not utilized. In Trial 1 where the animals were infected at one week of age the recorded data falls within the ranges recognized by other workers as normal. Lie (1968) showed that the p.c.v. was high in piglets at birth, decreased during the first week of life then increased during the next week. Lie's piglets had earth sprinkled with ferrous sulphate as a dietary source of iron, whereas the animals used in these trials were injected at 3 days of age with an iron dextran preparation. The consistently high p.c.v.'s recorded could be a result of this form of iron administration, since the concentration of iron present is directly related to the p.c.v. in the young animal (Kerncamp, 1932). The total white cell count fell within normally recorded ranges (Schalm, 1965), but tended to rise in both groups in the last four days, possibly owing to the effects of weaning. No differences were observed as a result of infection. In Trials 3 and 4 blood values were within the limits recognized in Schalm (1965) for animals of similar age and condition. The counts for Trial 3 tended to be more variable than those of 4, possibly a result of the different sampling methods used, the vena caval (puncture) technique being more efficient than the tail snipping method. There was no difference in the two trials which suggests that the difference in diet had affected the counts. Hacket, Seigneur & Bustad (1957) state that the only trend in haematological indices noticed in two groups of animals on different nutritional levels seemed to be related to season and age. The lowest level of crude protein fed in the present work (13 per cent) would have been adequate for maintenance needs and in Trial 5 the animals, bled on alternate days throughout the larval development period, showed no blood changes, even though larval activity was high at this time. Serum iron was measured in this group and the level remained steady throughout. The values were low but within the range of those recorded in pigs by other workers. Data produced from studies of anaemia following trichostrongylosis in ruminants have indicated that many other factors are involved, besides the worm, in the manifestation of an anaemia as a symptom of the disease (Baker & Douglas, 1966). The pathological changes produced in the stomach wall by H. rubidus have been examined under experimental conditions by a number of authors; these seem to agree that the greater part of the damage caused is mechanical-a result of the burrowing activity of the larvae, and the irritating presence of the worm on the stomach surface. Kendall et al. (1969) suggest that the damage noted in experimental studies could progress to the symptoms recorded from natural infestations. The failure to demonstrate an anaemia in any of the infections reported here might suggest that the levels of infection were too low to bring about significant blood loss due to larval penetration. However, under field conditions the chances of an animal contracting the same level of parasitaemia as recorded here are probably small. On the basis of these findings, therefore, it seems reasonable to suggest that reports of anaemia occurring where H. rubidus is found in the field are due primarily to some other cause, a nutritional deficiency possibly being the main factor. The aetiologies
H. RUBIDUS INFECTION IN THE PIG
of gastrointestinal parasitism and mal- or undernutrition are frequently difficult to differentiate. Amino acids are essential to the erythron production cycle, and a reduction in these may result in the development of an anaemia. Data on ruminant trichostrongylid infections indicate that hypoproteinaemia, especially hypoalbuminaemia, is a common finding in infected animals; in anaemic animals the degree of hypoalbuminaemia is greater than in nonanaemic animals (Cornelius, Baker, Kaneko & Douglas, 1962). Nielsen (1966) measured the turnover rate of radioactive labelled albumin in H. rubidus infected sows, and found that values were essentially normal, similar to those in uninfected sows, but postulated that a high rate of leakage into the stomach might occur when the larvae were active in the mucosa. If such a depletion of amino acids from the body's pool occurs, coupled with a loss of appetite in the animal, it could quickly lead to an anaemic condition. In the present study anaemia was clearly not clinically recognized in the experimental animals, for erythron production was not apparently impaired in any way, either as a result of haemorrhage, or as a result of depletion of the amino acid reserve. At no time were animals disinclined to eat, nor were there detectably significant differences in nutrition parameters. Animals were receiving adequate rations, and a nutrition-infection interaction resulting in blood change did not occur. ACKNOWLEDGEMENT
This work was supported by the Meat and Livestock Commission to whom we offer our sincere thanks. I. J. Lean was a Sir William Roberts postgraduate student and J. B. Castelino a British Commonwealth Scholar. REFERENCES
BAKER, N. F . & DOUGLAS, J. R. (1966). In Biology of Parasites, ed. E. J. L. Soulsby, p. 155. New York: Academic Press. BAMBACH, M. N. (1966). Klin. Wschr.44, 1276. CORNELIUS, C. E ., BAKER, N. F., KANEKO, J.]. & DOUGLAS,]. R. (1962) Am. J. vet. Res. 23, 837· DACIE,]. V. & LEWIS, S. M. (1963). Practical Haematology, 3rd edn. London:]. & A. Churchill. DAVIDSON,]. B., MURRAY, M. & SUTHERLAND, I. H. (1968). Vet. Rec. 83, 582. DODD, D. C. (1960). N.Z. vet. J. 8, 100. GERBER, H. C. (1968). Thesis, Free University, Berlin. RACKET, P. L., SEIGNEUR, L.]. & BUSTAD, L. K. (1957). U.S. Atomic Energy Commissior,. Biology Research Annual Report, p. I 12. KENDALL, S. B., THURLEY, D. C. & PEIRCE, M. A. (1969). J. compo Path. 79, 87· KERNCAMP, H. C. H. (1932). Minnesota Agric. Exp. Stn. Tech. Bull. no. 86. LARSEN, S. (1967) . Acta vet. scand. 8, 347. LAUBER, K. (1965). Z. klim. Chern. 3, 96. LEAN, I.]. (1969). Ph. D. Thesis, University of Wales, Bangor. LEAN, I. j., HERBERT,!.]., & CASTELINO,]. B. (1972). Br. vet. J. 128,000. LIE, H. (1968). Acta vet. scand. 9, 105. NETH, R., SCHAFER, K. H., DILLY, P. & LACK, E. (1963). Klin. Wschr. 41,1087. NICHOLSON, T. B. & GORDON,]. B. (1959). Vet. Rec. 71, 133. NIELSEN, K. (1966). Acta vet. scand. 7, 321. SCHALM, O. W. (1965). Veterinary Hematology. London: Bailliere, Tindall & Cassell.
(Receivedfor publication 20 October 1971)
BRITISH VETERINARY JOURNAL, 128, 3 Etudes sur la pathogenicite de l'infection par Hyostrongylus rubidus (nelDatode). Effets des taux d'infection allant jusqu'li 150.000 larves en phase infectieuse chez Ie cochon en voie de croissance II. Etudes du sang (Lean et al.) ResulDe. On a infecte experimentalement avec des doses uniques allant jusqu'a 150.000 larves infectieuses de H. rubidus des cochons en voie de croissance prives de colostrum, sans, pathogene specifique (S.P.F.) et eleves conventionnellement avec Ie minimum de maladies. Les indices hematologiques suivants ont ete etudies; Ie volume moyen globulaire, l'hemglobine moyenne des globules, la concentration moyenne des globules en hemoglobine, la capacite totale de liaison du fer (T.LB.C.) et Ie compte total de globules blancs. Les differences entre animaux infectes et animaux temoins n'etaient pas significatives statistiquement et des petites differences comme celles-ci persistaient pendant tres peu de temps. Studien fiber die Pathogenese der Infektion IDit Hyostrongylus rubidus (NelDatoda). Der Effekt von Infektion IDit bis zu 150 000 Larven ilD infektiosen StadiulD auf heranwachsende Schweine II. Blutuntersuchungen (Lean et al.) ZusalDlDenfassung. Schweine, die kein Colostrum (S.P.F.) erhalten hatten und in der liblichen Weise als "minimal disease" Schweine aufgezogen worden waren, wurden experimentell mit bis zu ISO 000 infektiosen H. rubidus Larven in einer Einzeldosis infiziert. Die folgenden haematologischen Daten wurden beobachtet: durchschnittliches Zellvolumen, durchschnittlicher Haemoglobingehalt der Zellen, durchschnittliche Haemoglobinkonzentration der Zellen, die totale Eisenabsorptionsfahigkeit (T.LB.C.) und die Gesamtleukozytenmenge. Es fanden sich Abweichungen von den normalen Werten, die auf ein Blutdefizit schliessen lassen. Unterschiede zwischen infizierten und Kontrolltieren waren statistisch nicht signifikant und die vorhandenen geringen Unterschiede hielten nur sehr kurze Zeit an. Estudios sobre la patogenesis de Infecci6n con Hyostrongylus rubidus (nelDatodes). Efectos de los niveles de infecci6n de hasta 150.000 larvas en fase infectiva sobre el cerdo en creciIDiento II. Estudios heIDatol6gicos (Lean et al.) ResUIDen. Cerdos en crecirniento privados de calostrum, libres de pat6genos especificos y criados con metodos convencionaIt-s fueron infectados experimentalmente con dosis (micas de hasta 150.000 larvas infecciosas de H. rubidus. Se estudiaron los siguientes indices hematol6gicos; volumen celular medio, hemoglobin a media en celulas, concentraci6n de hemoglobina media en celula, capacidad total de uni6n del hierro (T.LB.C.) y recuento total de leucocitos. No se presentaron desviaciones de los valores normales que pudiesen sugerir un deficit sanguineo. Los diferencias entre los animales no infectados y los controles no tuvieron ningun significado estadistico y tales diferencias ligeras como las encontradas persistieron solamente por un periodo muy breve de tiempo.
J. (1972), 128, 147
STUDIES ON THE PATHOGENESIS OF INFECTION WITH HYOSTRONGYLUS RUBIDUS (NEMATODA). THE EFFECTS OF LEVELS OF INFECTION OF UP TO 150,000 INFECTIVE STAGE LARVAE ON THE GROWING PIG II. BLOOD STUDIES By 1.
J.
LEAN,
1. V.
HERBERT, AND
J.
B.
CASTELINO
Department of Agricultural and Forest Zoology, University College of North Wales, Bangor
SUMMARY
Colostrum-deprived specific pathogen-free (S.P.F.) and conventionally reared animal disease growing pigs were experimentally infected with single doses of up to 150,000 H. rubidus infective larvae. The following haematological indices were studied: mean cell volume, mean cell haemoglobin, mean cell haemoglobin concentration, total iron binding capacity and total white cell counts. No deviations from normal values occurred which suggest blood deficit. Differences between uninfected and control animals were not statistically significant and such slight differences as there were persisted for a very short period of time. INTRODUCTION
The nematodes of the Trichostrongylidae have often been incriminated in effecting blood changes in their host animals, an oligocythaemia being commonly found. The anaemia is induced either by a continual removal of host blood or by the parasite's utilizing some nutritive factor necessary to the host's blood production, or by the parasite's producing conditions in the host under which other organisms can thrive, or as a result of malabsorption or abnormal gut enzyme activity which in turn would affect formed elements of the blood. Recorded data involving infections with the Trichostrongylidae of ruminants shows some extremely varied results, which suggest that the "condition" of animals at time of infection is of importance in relation to the subsequent pathogenesis of infection as demonstrated by the blood. Anaemia has been observed in the field in both young pigs and sows which have also been shown to harbour Hyostrongylus rubidus. Gerber (1968) and Kendall, Thurley & Peirce (1969) found no change in the blood picture when following the course of single experimental infections of up to 4000 larvae. The present experiments are a more extensive study of blood changes, including information on infection in animals of different ages kept on different diets, and infected with single doses of up to 150,000 larvae. The effect of a single reinfestation with 20,000 larvae is also detailed. The animals used in these trials were some of those used in the nutritional studies which have been previously reported * and correspond to
BRITISH VETERINARY JOURNAL, 128,3
Trials I, 3, 4 and S. Reference should be made to Lean, Herbert & Castelino (1972) for full experimental details. MATERIALS AND METHODS
Four groups of Large White and Large 'White cross Landrace conventionally reared minimal disease growing pigs were infected with single doses of H. rubidus larvae. Blood samples were taken from the ear veins of animals in Trial 1 on alternate days, once the day before infection and then following infection for the prepatent period of 20 days. The animals were weaned at patency to avoid possible infection of the sow. Sufficient blood was taken to determine packed cell volume (p.c.v.), and total white cell count (w.b.c.). The animals in Trial 3 were bled weekly for 12 weeks starting one week before infection. Blood was collected by tail snipping. In Trials 4 and S the animals were bled from the anterior vena cava, in Trial 4 at weekly intervals and Trial S on alternate days. Heparin was used as an anticoagulant in this technique and EDTA in the tail snip method. In Trial I, blood was collected directly into heparinized microhaematocrit tubes, and dilution pipettes. P.c.v. was measured on a Hawksley microhaematocrit, total haemoglobin percentage (Hb per cent) by the cyanomethoglobin method in an EEL haemoglobinometer, and total red blood cell (r.b.c.) and w.b.c. were determined on a Coulter electronic counter. Calculation of mean cell volume (m.c.v.), mean cell haemoglobin (m.c.h.), and mean cell haemoglobin concentration (m.c.h.c.) were made as described in Dacie & Lewis (1963). Additionally, serum iron, and total iron binding capacity (t.i.b.c.) were determined on samples taken from Trials 4 and S by a method derived from the work of Neth, Schafer, Dilly & Lack (1963), Lauber (196S) and Bambach (1966) by Schweizerhall Chemicalst. In this method bathophenanthroline disulphonate is used as the colour reagent. RESULTS
In Trial 1 there was an increase in p.c.v. over the first 6 days of the experiment, and the increased levels persisted throughout the infection period. This occurred in both infected and non-infected animals. The mean w.b.c. counts for infected and non-infected animals were similar, with the mean readings for the infected animals being slightly higher throughout the recordings. In Trials 3 and 4, where animals were bled weekly, r.b.c. counts for the noninfected animals tended to be slightly higher than those of the infected animals, whereas w.b.c. counts, Hb per cent and p.c.v. values showed no difference (see Lean, 1969). The observations in Trials were on an alternate day basis (Fig. I) for the first 30 days of a single large infection (150,000) and show no difference between infected and non-infected animals. • See Part I, p. 138. t Unicam Limited, Cambridge.
H. RUBIDUS INFECTION IN THE PIG
%
:~ ~
A.
35 -
Hb%
149
, paint of Infection
-
~._ ';II""~-==i:---===i:-==~-&::::-::::::J.t:--::::::::.e:=-i-~~-:::t..>-oe
B.
14 13 12
.-e_
II
9 8xl0 6 7
'0
C.
r·-·-·-"e=~~_·~·_i_~
:~"O'r:-: o
2
4
= 6
8
10
12
1416
18
20
22
24
26
28
30
Days
Fig.
I.
Group mean blood values of trial 5 animals. A= B= C= D =
o •
Packed cell volume, percentage. Haemoblobin percentage. Red blood cells. White blood cells. 0 Non-infected. • Infected; 150,000 larvae.
Calculations of m.c. v., m.c.h. and m.c.h.c. were made on the data from Trials 2, 3, and 4. No deviation from normal appeared in the derived values to suggest an anaemic condition. Serum iron and t.i. b.c. of serum determinations carried out on trials 4 and 5, revealed no trends in the data which might indicate a blood deficit (see Lean, 1969). DISCUSSION
Baker & Douglas (1966) discussed the alterations which occurred in the erythron during the course of nematode infection, paying special attention to the effects caused by trichostrongyles which infect ruminants. Their report indicated that the effects of different worm infections vary greatly and are related to factors such as age, nutrition, and management of the animal, in addition to the size of infection. Occasional reports of hyostrongylosis refer to symptoms of anaemia in infected animals (Nicholson & Gordon, 1959; Dodd, 1960; Davidson, Murray & Sutherland, 1968). Signs of blood loss such as tarry faeces are also reported and it seems possible that such loss may be brought about either by the mechanical activity or the feeding activity of the worm, for Larsen (1967) has
BRITISH VETERINARY JOURNAL, 128, 3
demonstrated the presence of erythrocytes in the worm's gut, which shows that some blood is ingested even if not utilized. In Trial 1 where the animals were infected at one week of age the recorded data falls within the ranges recognized by other workers as normal. Lie (1968) showed that the p.c.v. was high in piglets at birth, decreased during the first week of life then increased during the next week. Lie's piglets had earth sprinkled with ferrous sulphate as a dietary source of iron, whereas the animals used in these trials were injected at 3 days of age with an iron dextran preparation. The consistently high p.c.v.'s recorded could be a result of this form of iron administration, since the concentration of iron present is directly related to the p.c.v. in the young animal (Kerncamp, 1932). The total white cell count fell within normally recorded ranges (Schalm, 1965), but tended to rise in both groups in the last four days, possibly owing to the effects of weaning. No differences were observed as a result of infection. In Trials 3 and 4 blood values were within the limits recognized in Schalm (1965) for animals of similar age and condition. The counts for Trial 3 tended to be more variable than those of 4, possibly a result of the different sampling methods used, the vena caval (puncture) technique being more efficient than the tail snipping method. There was no difference in the two trials which suggests that the difference in diet had affected the counts. Hacket, Seigneur & Bustad (1957) state that the only trend in haematological indices noticed in two groups of animals on different nutritional levels seemed to be related to season and age. The lowest level of crude protein fed in the present work (13 per cent) would have been adequate for maintenance needs and in Trial 5 the animals, bled on alternate days throughout the larval development period, showed no blood changes, even though larval activity was high at this time. Serum iron was measured in this group and the level remained steady throughout. The values were low but within the range of those recorded in pigs by other workers. Data produced from studies of anaemia following trichostrongylosis in ruminants have indicated that many other factors are involved, besides the worm, in the manifestation of an anaemia as a symptom of the disease (Baker & Douglas, 1966). The pathological changes produced in the stomach wall by H. rubidus have been examined under experimental conditions by a number of authors; these seem to agree that the greater part of the damage caused is mechanical-a result of the burrowing activity of the larvae, and the irritating presence of the worm on the stomach surface. Kendall et al. (1969) suggest that the damage noted in experimental studies could progress to the symptoms recorded from natural infestations. The failure to demonstrate an anaemia in any of the infections reported here might suggest that the levels of infection were too low to bring about significant blood loss due to larval penetration. However, under field conditions the chances of an animal contracting the same level of parasitaemia as recorded here are probably small. On the basis of these findings, therefore, it seems reasonable to suggest that reports of anaemia occurring where H. rubidus is found in the field are due primarily to some other cause, a nutritional deficiency possibly being the main factor. The aetiologies
H. RUBIDUS INFECTION IN THE PIG
of gastrointestinal parasitism and mal- or undernutrition are frequently difficult to differentiate. Amino acids are essential to the erythron production cycle, and a reduction in these may result in the development of an anaemia. Data on ruminant trichostrongylid infections indicate that hypoproteinaemia, especially hypoalbuminaemia, is a common finding in infected animals; in anaemic animals the degree of hypoalbuminaemia is greater than in nonanaemic animals (Cornelius, Baker, Kaneko & Douglas, 1962). Nielsen (1966) measured the turnover rate of radioactive labelled albumin in H. rubidus infected sows, and found that values were essentially normal, similar to those in uninfected sows, but postulated that a high rate of leakage into the stomach might occur when the larvae were active in the mucosa. If such a depletion of amino acids from the body's pool occurs, coupled with a loss of appetite in the animal, it could quickly lead to an anaemic condition. In the present study anaemia was clearly not clinically recognized in the experimental animals, for erythron production was not apparently impaired in any way, either as a result of haemorrhage, or as a result of depletion of the amino acid reserve. At no time were animals disinclined to eat, nor were there detectably significant differences in nutrition parameters. Animals were receiving adequate rations, and a nutrition-infection interaction resulting in blood change did not occur. ACKNOWLEDGEMENT
This work was supported by the Meat and Livestock Commission to whom we offer our sincere thanks. I. J. Lean was a Sir William Roberts postgraduate student and J. B. Castelino a British Commonwealth Scholar. REFERENCES
BAKER, N. F . & DOUGLAS, J. R. (1966). In Biology of Parasites, ed. E. J. L. Soulsby, p. 155. New York: Academic Press. BAMBACH, M. N. (1966). Klin. Wschr.44, 1276. CORNELIUS, C. E ., BAKER, N. F., KANEKO, J.]. & DOUGLAS,]. R. (1962) Am. J. vet. Res. 23, 837· DACIE,]. V. & LEWIS, S. M. (1963). Practical Haematology, 3rd edn. London:]. & A. Churchill. DAVIDSON,]. B., MURRAY, M. & SUTHERLAND, I. H. (1968). Vet. Rec. 83, 582. DODD, D. C. (1960). N.Z. vet. J. 8, 100. GERBER, H. C. (1968). Thesis, Free University, Berlin. RACKET, P. L., SEIGNEUR, L.]. & BUSTAD, L. K. (1957). U.S. Atomic Energy Commissior,. Biology Research Annual Report, p. I 12. KENDALL, S. B., THURLEY, D. C. & PEIRCE, M. A. (1969). J. compo Path. 79, 87· KERNCAMP, H. C. H. (1932). Minnesota Agric. Exp. Stn. Tech. Bull. no. 86. LARSEN, S. (1967) . Acta vet. scand. 8, 347. LAUBER, K. (1965). Z. klim. Chern. 3, 96. LEAN, I.]. (1969). Ph. D. Thesis, University of Wales, Bangor. LEAN, I. j., HERBERT,!.]., & CASTELINO,]. B. (1972). Br. vet. J. 128,000. LIE, H. (1968). Acta vet. scand. 9, 105. NETH, R., SCHAFER, K. H., DILLY, P. & LACK, E. (1963). Klin. Wschr. 41,1087. NICHOLSON, T. B. & GORDON,]. B. (1959). Vet. Rec. 71, 133. NIELSEN, K. (1966). Acta vet. scand. 7, 321. SCHALM, O. W. (1965). Veterinary Hematology. London: Bailliere, Tindall & Cassell.
(Receivedfor publication 20 October 1971)
BRITISH VETERINARY JOURNAL, 128, 3 Etudes sur la pathogenicite de l'infection par Hyostrongylus rubidus (nelDatode). Effets des taux d'infection allant jusqu'li 150.000 larves en phase infectieuse chez Ie cochon en voie de croissance II. Etudes du sang (Lean et al.) ResulDe. On a infecte experimentalement avec des doses uniques allant jusqu'a 150.000 larves infectieuses de H. rubidus des cochons en voie de croissance prives de colostrum, sans, pathogene specifique (S.P.F.) et eleves conventionnellement avec Ie minimum de maladies. Les indices hematologiques suivants ont ete etudies; Ie volume moyen globulaire, l'hemglobine moyenne des globules, la concentration moyenne des globules en hemoglobine, la capacite totale de liaison du fer (T.LB.C.) et Ie compte total de globules blancs. Les differences entre animaux infectes et animaux temoins n'etaient pas significatives statistiquement et des petites differences comme celles-ci persistaient pendant tres peu de temps. Studien fiber die Pathogenese der Infektion IDit Hyostrongylus rubidus (NelDatoda). Der Effekt von Infektion IDit bis zu 150 000 Larven ilD infektiosen StadiulD auf heranwachsende Schweine II. Blutuntersuchungen (Lean et al.) ZusalDlDenfassung. Schweine, die kein Colostrum (S.P.F.) erhalten hatten und in der liblichen Weise als "minimal disease" Schweine aufgezogen worden waren, wurden experimentell mit bis zu ISO 000 infektiosen H. rubidus Larven in einer Einzeldosis infiziert. Die folgenden haematologischen Daten wurden beobachtet: durchschnittliches Zellvolumen, durchschnittlicher Haemoglobingehalt der Zellen, durchschnittliche Haemoglobinkonzentration der Zellen, die totale Eisenabsorptionsfahigkeit (T.LB.C.) und die Gesamtleukozytenmenge. Es fanden sich Abweichungen von den normalen Werten, die auf ein Blutdefizit schliessen lassen. Unterschiede zwischen infizierten und Kontrolltieren waren statistisch nicht signifikant und die vorhandenen geringen Unterschiede hielten nur sehr kurze Zeit an. Estudios sobre la patogenesis de Infecci6n con Hyostrongylus rubidus (nelDatodes). Efectos de los niveles de infecci6n de hasta 150.000 larvas en fase infectiva sobre el cerdo en creciIDiento II. Estudios heIDatol6gicos (Lean et al.) ResUIDen. Cerdos en crecirniento privados de calostrum, libres de pat6genos especificos y criados con metodos convencionaIt-s fueron infectados experimentalmente con dosis (micas de hasta 150.000 larvas infecciosas de H. rubidus. Se estudiaron los siguientes indices hematol6gicos; volumen celular medio, hemoglobin a media en celulas, concentraci6n de hemoglobina media en celula, capacidad total de uni6n del hierro (T.LB.C.) y recuento total de leucocitos. No se presentaron desviaciones de los valores normales que pudiesen sugerir un deficit sanguineo. Los diferencias entre los animales no infectados y los controles no tuvieron ningun significado estadistico y tales diferencias ligeras como las encontradas persistieron solamente por un periodo muy breve de tiempo.