Comparison
of the onset of an immune response using three oocyst
vaccination strategies
D.G. Richards*, Eimeria Research Project,
Werribee, Australia
*medichick@ava.com.au
EimeriaVAX 4m®
is a 4 species coccidiosis vaccine containing Australian
precocious strains of E acervulina, E maxima, E necatrix
and E tenella administered to 100% birds by individual
eye-drop application from day-old. Aerosol spray is
appealing because it is less time-consuming for mass
application of oocysts. Unfortunately, aerosol is
not as precise. There is no information on whether
the alternative of eye drop vaccination of a percentage
of chickens plus coarse aerosol spraying the remainder
would overcome the reduced accuracy of aerosol. To
investigate this hypothesis, three groups of broilers
were vaccinated at day-old with a) 100% coarse aerosol,
b) 15% individual eye-drop and 85% aerosol and c)
100% individual eye-drop. One group of birds was unvaccinated.
Oocysts per gram of faeces (OPG) were enumerated for
each group at 5, 6, 7, 14, 21, 28, 35, and 42 days
of age. At 11, 20, and 29 days post-infection, birds
were removed and challenged with live oocysts of the
same species in the vaccine. At 6 days post challenge,
intestinal tissues were fixed. Following histological
preparation and staining, tissues were scored for
lesions. Weight gain post challenge was collected.
At 5, 6 and 7 days post vaccination there was a spike
in the OPG from the group vaccinated at day-old by
eye-drop. Following the first challenge at 11 days
of age, comparative analysis of the OPG showed eye-drop
vaccinated chickens always showed the lowest OPG for
each day. This trend was repeated with the histological
analysis. Following the challenge at 20 and 29 days
of age, OPG results indicated that the challenged
groups had the highest oocyst output, the highest
histological lesion scores and the lowest weight gain.
There was no consistent difference between any vaccination
regime.
The results show the immune response by 10 days post
vaccination was sufficient to give the birds vaccinated
by eye-drop some protection from challenge. There
was no difference between any groups by 21 days. It
is concluded there is a delay in the onset of immunity
when administering live coccidiosis vaccines by aerosol
spray. This paper also describes the success of the
in field use of the aerosol and eye-drop technique.