Development of a precocious strain of Eimeria tenella
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Date
2001
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Department of Veterinary Parasitology, College of Veterinary and Animal Sciences, Mannuthy
Abstract
Studies on the prevalence of caecal coccidiosis in chicken, by referring to the postmortem registers
maintained at the centre of Excellence in Pathology,
College of Veterinary and Animal Sciences~ Mannuthy
revealed that 48.4 per cent of 550 coccidia positive
viscera was due to Eimeria tenella.
A pure line of
E. tenella was established in the laboratory by single
oocyst isolation technique from a virulent field case of
caecal coccidiosis in chicken. A stabilised strain of
E. tenella was developed by administering a dose of
1.5x103 sporulated pure line E. tenella oocysts per bird
orally to six three to five day old coccidia free White
Leghorn chicks and harvesting the caecal contents at 168
hr pi for 15 cyclic~l passages. For the development of a
precocious strain of E. tenella a dose of 1.5x103
sporulated E. tenella oocysts per bird was administered
orally to six, three to five day old White Leghorn
chicks. The caecal contents were harvested at 136 hr pi
and
the
oocysts
were
allowed to sporulate and subsequently repassaged by applying selection pressure in
increments of one hour reduction at each passage. At the
end of 18 cyclical passages, oocysts obtained at 125 hr pi were designated
E. tenella. as the precocious strain of. A comparative study between the precocious and
stabilised strain of E. tenella revealed the following
observations~
The prepatent period of the precocious strain was
125 hr while that of the stabilised strain was 135 hr.
The oocyst morphology did not reveal any significant
difference between the two strains. The precocious strain
was less pathogenic and produced milder clinical signs
than the stabilised strain. The gross lesions of caeca
were less morbid in the precocious strain infected group.
Weight gain was more in the precocious strain infected
group than in the stabilised strain infected group. The
precocious strain produced less mortality and showed a
drop in oocyst production.
Endogenous study revealed an accelerated growth in
the early stages of the asexual life cycle in the
precocious strain infected group.
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Citation
171865