Maternal Protection against Eimeria challenge of CoxAbic® vaccinated chickens
Avner Finger & Amnon
Michael,
ABIC Biological Laboratories TEVA, ISRAEL
Abstract
CoxAbic®, the subunit vaccine was tested for its ability to protect young
broiler chicks by way of Maternal Immunity. Broiler breeder pullets were twice
vaccinated with the vaccine during rearing. Eggs collected from these and from
unvaccinated hens were hatched and groups of the offspring chicks were raised on
litter floor cages. On day 8 after hatch, a simulated natural exposure was
applied by infecting orally 1 chick from every 13 chicks with 50 sporulated
oocysts each of four species of coccidia – E. maxima, acervulina, tenella and
mitis. Groups of chicks were kept on wire floored cages unexposed to coccidia
and served as negative controls. On day 35 groups of the chicks were orally
challenged with one of the four Eimeria species (80,000 oocysts of E. acervulina,
25,000 maxima, 120,000 mitis and 25,000 tenella). Oocysts were counted in the
litter (OPG) after the exposure of the seeder chicks and after challenge. Body
weights were recorded before and after challenge. OPG indicated that the
simulated natural exposure to coccidia resulted in infection of the birds
through cycling parasites. Chicks from vaccinated and unvaccinated dams became
actively immune by way of the exposure as elicited by their resistance to the
challenge at 35 days of age in comparison to the negative control chickens. The
difference between the two groups was expressed in their body weights. There was
a consistent gap of approximately 25% in favor of the CoxAbic ® chicks, which
was recorded after the early exposure through rearing until the end of the trial
at 55 days of age.
The trial showed that maternal immunity protects broiler chicks from the effects
of early exposure to coccidian parasites. This early natural exposure to the
ubiquitous parasite is the way that chicks become actively immune to coccidiosis,
but in birds without the protection of maternal antibodies (or of coccidiostats
in their feed), this early exposure results in a significant and economically
important weight reduction, from which CoxAbic® chicks are spared.