Characterization of cryptic field isolates of Eimeria spp. from chickens.
Wayne G. Woods and D. Grant Richards*
Eimeria Pty Ltd, 250 Princes Highway, Werribee, VIC, 3030. Australia.
*medichick@ava.com.au
The identification of variants of
Eimeria species has important implications in discovering emerging strains not
covered by current vaccines. It was therefore important, in Australia, to
determine if local strains reflected overseas trends in this regard.
We have been studying the species composition of coccidiosis outbreaks in
Australian chickens. The technique we employ involves the isolation of DNA from
faecal oocysts and a PCR/electrophoresis analysis of the ITS-2 region of the
parasite genome. All previously analysed strains, encompassing the seven known
species of chicken Eimeria, are present species-specific banding patterns, with
only minor variation in band positions between strains.
From the analysis of field samples, we have obtained isolates that represent two
novel banding patterns. Pure isolates of these two cryptic taxa were obtained
first by passage of mixed-species oocysts through hyperimmunized birds, and then
isolation and amplification of single oocysts. The isolates were then
characterized by biometrics, macro- and microscopic gut lesions, prepatent
period, reproductive index and genetic sequencing. This poster details the
isolation, characterization, and taxonomic affiliation of these two taxa.