- Email: [email protected]
On Experimental Transmission of Ostertagia Ostertagi (Stiles, 1892) Ransom, 1907, to Sheep
Br. vet.
:J.
(1971), 1117; xlviii ·
ON · EXPERIMENTAL TRANSMISSION OF OSTER.TAGIA OSTERTAG/ (STILES, 1892) RANSOM, 1907, to SHEEP . BY .
v. s.
PANDEY
. Faculty of.Vet.e'rinary Medicine,. Brussels, Bi:Igi~m ' ·. . .. . ~
-
SUMMARY
Lambs were administered heavy doses of infective larvae of Ostertagia ostertagi. Those autopsied 29 days aft¢r infection had some worms while others autOpsied at the 57th day had no . woriris. The \rulval flap was absen..t 'in female worms and eggs were not detected in :the .faeces of the lambs; The sheep is considered to be an unsuitable host for 0. ostertagi. INTRODUCTION
Ostertagia ostertagi is a conunon stomach worm of cattle in temperate regions and the reports of its development in sheep are very contradictory. Porter (I 953), in a cross transmission experiment, could not find 0. ostertagi in sheep although they established well in calves. Herlich & Stewart (I954) reported that 0. ostertagi could be maintained in lambs as immature worms for a short time. Herlich (I 958) found low numbers of 0. ostertagi in three out of five lambs infected experimentally and Dikmans & Kates (I 955) obtained only two worms from a lamb fed with 5330 infective larvae of 0. ostertagi. The present communication records attempts to infect four lambs with 0. ostertagi with a view to clarifying the existing confusion. MATERIALS AND METHODS
Four lambs born and reared under worm-free conditions in the laboratory were used. The infective larvae of 0. ostertagi were obtained by culturing the faeces from a calf carrying a pure infection. Freshly harvested infective larvae were administered to lambs through a stomach tube. The faeces were regularly examined by a salt flotation technique. On autopsy the abomasum was examined for any nodules and then artificially digested by peptic digestion technique. All the worms from stomach washings and digestion fluid were counted and fixed for subsequent examination. RESULTS
Details of the experimental lambs and results are presented in Table · I. No eggs were found in the faeces of the lambs. The examination of female worms showed complete absence of the vulval flap, except in few females
EXPERIMEN'l'AL TRANSMISSION OF 0. OSTERTAG/ TO SHEEP
lxix
which possessed very rudimentary protrusions. However, a few segmented eggs were observed in the uteri of some female worms. TABLE
1
DATA ON EXPERIMENTAL INFECTION OF LAMBS WITH
Lamb No.
1 2 3 4
Age (months)
Weight (kg)
Dose of irifective larvae
2 2
21 15
150,000
r ·s
II
2
15
75,000 75,000
Ostertagia ostertagi
Days of autopsy after administration of larvae
No. of worms recovered
Percentage establishment
29 29 57 57
66o
0"44
940 0 0
rso,ooo
o·62
0 0
DISCUSSION
This experiment indicates that 0. ostertagi may establish in lambs but in relatively insignificant numbers. The absence of worms in lambs autopsied 57 days after infection may be explained in two ways: either these lambs were refractory to infection or the worms might have established in the beginning which were thrown off later on. Since both the lambs examined on 29th day contained worms, the second proposition seems to be more feasible. The absence of vulval flaps in females and eggs in faeces indicates that the presence of worms in an unsuitable host somehow interfered with normal development and normal ovijection. The pinpoint nodules in the abomasum observed by Herlich (1958) were not present in the two lambs harbouring the worms. It seems quite evident that 0. ostertagi is completely harmless to sheep. Even if some worms are established, they may not contaminate the pasture owing to lack of their egg-laying capacity. This phenomenon can be usefully utilized in farm management where cattle and sheep are reared together on the same farm. The sheep can safely be run on a pasture contaminated by 0. ostertagi. A double advantage will be that the sheep will clean the pasture of infective larvae of 0. ostertagi on which the cattle may be run later safely. ACKNOWLEDGEMENT
I am grateful to Profes~or Dr L. Pouplard, Faculty of Veterinary Medicine, Brussels, for providing the facilities for this work. REFERENCES
DnwANs, G. & KATES, K. C. (1955). Proc. helminth Soc. Wash. 22, 42. H. (1958). Trans. Am. microsc. Soc. 77, 373· HERLICH, H. & STEWART, T. B. (1954) Proc. helminth Soc. Wash. 21, 121. PoRTER, A. D. (1953). Am.]. vet. Res. 14o 550. HERLICH,
:J.
(1971), 1117; xlviii ·
ON · EXPERIMENTAL TRANSMISSION OF OSTER.TAGIA OSTERTAG/ (STILES, 1892) RANSOM, 1907, to SHEEP . BY .
v. s.
PANDEY
. Faculty of.Vet.e'rinary Medicine,. Brussels, Bi:Igi~m ' ·. . .. . ~
-
SUMMARY
Lambs were administered heavy doses of infective larvae of Ostertagia ostertagi. Those autopsied 29 days aft¢r infection had some worms while others autOpsied at the 57th day had no . woriris. The \rulval flap was absen..t 'in female worms and eggs were not detected in :the .faeces of the lambs; The sheep is considered to be an unsuitable host for 0. ostertagi. INTRODUCTION
Ostertagia ostertagi is a conunon stomach worm of cattle in temperate regions and the reports of its development in sheep are very contradictory. Porter (I 953), in a cross transmission experiment, could not find 0. ostertagi in sheep although they established well in calves. Herlich & Stewart (I954) reported that 0. ostertagi could be maintained in lambs as immature worms for a short time. Herlich (I 958) found low numbers of 0. ostertagi in three out of five lambs infected experimentally and Dikmans & Kates (I 955) obtained only two worms from a lamb fed with 5330 infective larvae of 0. ostertagi. The present communication records attempts to infect four lambs with 0. ostertagi with a view to clarifying the existing confusion. MATERIALS AND METHODS
Four lambs born and reared under worm-free conditions in the laboratory were used. The infective larvae of 0. ostertagi were obtained by culturing the faeces from a calf carrying a pure infection. Freshly harvested infective larvae were administered to lambs through a stomach tube. The faeces were regularly examined by a salt flotation technique. On autopsy the abomasum was examined for any nodules and then artificially digested by peptic digestion technique. All the worms from stomach washings and digestion fluid were counted and fixed for subsequent examination. RESULTS
Details of the experimental lambs and results are presented in Table · I. No eggs were found in the faeces of the lambs. The examination of female worms showed complete absence of the vulval flap, except in few females
EXPERIMEN'l'AL TRANSMISSION OF 0. OSTERTAG/ TO SHEEP
lxix
which possessed very rudimentary protrusions. However, a few segmented eggs were observed in the uteri of some female worms. TABLE
1
DATA ON EXPERIMENTAL INFECTION OF LAMBS WITH
Lamb No.
1 2 3 4
Age (months)
Weight (kg)
Dose of irifective larvae
2 2
21 15
150,000
r ·s
II
2
15
75,000 75,000
Ostertagia ostertagi
Days of autopsy after administration of larvae
No. of worms recovered
Percentage establishment
29 29 57 57
66o
0"44
940 0 0
rso,ooo
o·62
0 0
DISCUSSION
This experiment indicates that 0. ostertagi may establish in lambs but in relatively insignificant numbers. The absence of worms in lambs autopsied 57 days after infection may be explained in two ways: either these lambs were refractory to infection or the worms might have established in the beginning which were thrown off later on. Since both the lambs examined on 29th day contained worms, the second proposition seems to be more feasible. The absence of vulval flaps in females and eggs in faeces indicates that the presence of worms in an unsuitable host somehow interfered with normal development and normal ovijection. The pinpoint nodules in the abomasum observed by Herlich (1958) were not present in the two lambs harbouring the worms. It seems quite evident that 0. ostertagi is completely harmless to sheep. Even if some worms are established, they may not contaminate the pasture owing to lack of their egg-laying capacity. This phenomenon can be usefully utilized in farm management where cattle and sheep are reared together on the same farm. The sheep can safely be run on a pasture contaminated by 0. ostertagi. A double advantage will be that the sheep will clean the pasture of infective larvae of 0. ostertagi on which the cattle may be run later safely. ACKNOWLEDGEMENT
I am grateful to Profes~or Dr L. Pouplard, Faculty of Veterinary Medicine, Brussels, for providing the facilities for this work. REFERENCES
DnwANs, G. & KATES, K. C. (1955). Proc. helminth Soc. Wash. 22, 42. H. (1958). Trans. Am. microsc. Soc. 77, 373· HERLICH, H. & STEWART, T. B. (1954) Proc. helminth Soc. Wash. 21, 121. PoRTER, A. D. (1953). Am.]. vet. Res. 14o 550. HERLICH,