Quantification of Eimeria acervulina in faeces of broilers: Comparison of McMaster oocyst counts from 24 h faecal collections and single droppings to real-time PCR from cloacal swabs

Coccidiosis is an economically important disease in chickens, caused by infection with
Eimeria species parasites. Diagnosis of coccidiosis is frequently based on oocyst enumeration
in pooled faecal samples or litter. In studies on infection dynamics and for monitoring in the
field, samples from individual chickens may be more appropriate as these support the
determination of infection status of individual birds and more accurately reflect oocyst
output at time of sampling. Faecal samples from individual birds can be collected, but the
counting procedure limits the number of samples that can be processed and unequivocal
microscopic differentiation between Eimeria species is very difficult. A test that overcomes
these drawbacks would improve efficiency and quality of the diagnosis.
The aim of this study was to compare two methods for Eimeria oocyst quantification in
samples from individual birds. A real-time PCR that quantifies oocysts in cloacal swabs
(qPCR) and oocyst counts in single droppings were compared to the standard procedure of
oocyst counts in bulked 24 h faeces.
Faecal samples were collected daily from 30 broiler chickens, inoculated with different
doses of Eimeria acervulina. The three techniques produced comparable oocyst counts for
all inoculation doses. Single dropping counts are applicable for small sample sizes and
when a single Eimeria species is used. For larger sample sizes qPCR is preferable as it can be
carried out on samples that have been frozen for storage. Furthermore, qPCR can identify
and quantify different Eimeria species, whichmakes it a valuable diagnostic tool for field or
experimental work.