Efficacy of Coccivac against field isolates of chicken
Eimeria
Steve
H. Fitz-Coy
Schering-Plough Animal Health, Union NJ
steve.fitz-coy@spcorp.com
This report
includes a series of tests to compare the antigenicity
of coccidia isolated from recent field samples against
those in Coccivac. Based on the data, the antigens
in Coccivac provided good protection against field
isolates.
The objective of the study was to determine the incidence
of field strains of Eimeria that show differences
in antigenic properties from those antigens in the
Coccivac vaccine. Field isolates collected from 60
broiler and breeder pullet farms across the USA. The
chickens (n=70/group) were inoculated per os with
one dose of Coccivac-B or Coccivac-D during the first
week of life. Inoculated birds were placed into floor
pens on clean wood shavings, then grown to approximately
35 days of age. Following immunization, birds were
tagged and placed into assigned treatment groups.
Attempts were not made to purify the inocula, but
to standardize the E. maxima level to 100,000 sporulated
oocysts per bird. Birds from the immunized group and
their un-immunized hatch-mates were challenged with
inocula of field isolates. The un-immunized hatch-mates
served as the positive controls. Birds kept in the
challenge phase between 144 to 156 hr, the following
processes were followed: euthanasia, necropsy and
intestines examined grossly for coccidial lesions
using a 0 to 4 scoring system. Mucosal scrapings taken
from the duodenal loop, jejunum, ileum and ceca were
then placed on microscope slides for microscopic evaluations.
Microscopic evaluation (scored 0 to 4) was made using
a compound light microscope. Severity of infection
(0 = no parasite, 1 = 1 to 10 per field, 2 = 11 to
20 per field, 3 = 21 to 40 per field and 4 = >
50 per field for E. maxima).
Birds immunized with Coccivac and challenged with
field isolates demonstrated substantial immunity as
determined by the level of parasitism in the immunized
birds vs the non-immunized groups for E. acervulina,
E. tenella and E. maxima. The average level of protection
provided by Coccivac against the three predominant
species of field isolates of Eimeria (E. acervulina,
E. maxima and E. tenella) were: 97%, 86% and 91%,
respectively.
