The Thai Journal of Veterinary Medicine


Avian coccidiosis is a protozoan disease which can be caused by at least 7 species of the genus Eimeria. Species of Eimeria in chicken are distinguished by their distinct morphology and where sites the parasotes are deposited in the small intestine of the infected birds. The criteria for Eimeria species differentiation when the disease occures is sometimes unreliable. Based on 422 base pairs derived from the 3 prime-region of the 18S rRNA gene, containing polymorphic DNA sequences of Eimeria, the technique of PCR-RFLP (Polymerase chain reaction and Restriction fragment length polymorphisms) has been developed to identify species-specific DNA profiles of Eimeria acervulina, E. maxima, E. necatrix and E. tenella. PCR-RFLP can differentiate between Eimeria species containing in the isolate, Eimeria CB38 identifying at least 3 species; E. maxima, E. necatrix and E. tenella. Eimeria CB38 is an isolate from chicken coccidiosis collected from Cholburi, a province of Thailand, which had never been indentified prior to this study. Eimeria in Immucox®(I), the live-attenuated vaccine, were also used as controls in this study. The PCR sensitivity for Eimeria CB38 was at 0.12 oocysts and the PCR-RFLP sensitivity was at 8 oocysts. The molecular diagnosis of the 18S rRNA gene characterization of Eimeria spp. has proven to be useful in identifying at least 4 of the 7 species of chicken Eimeria.

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