MixedTheileriainfections in free-ranging buffalo herds: implications for diagnosingTheileria parvainfections in Cape buffalo (Syncerus caffer)

Abstract

SUMMARYBuffalo-adaptedTheileria parvacauses Corridor disease in cattle. Strict control measures therefore apply to the movement of buffalo in South Africa and include mandatory testing of buffalo for the presence ofT. parva. The official test is a real-time hybridization PCR assay that amplifies the V4 hypervariable region of the 18S rRNA gene ofT. parva, T.sp. (buffalo) andT.sp. (bougasvlei). The effect that mixedT. parvaandT.sp. (buffalo)-like infections have on accurateT. parvadiagnosis was investigated in this study.In vitromixed infection simulations indicated PCR signal suppression at 100 to 1000-foldT.sp. (buffalo) excess at lowT. parvaparasitaemia. Suppression of PCR signal was found in field buffalo with mixed infections. TheT. parva-positive status of these cases was confirmed by selective suppression ofT.sp. (buffalo) amplification using a locked nucleic acid clamp and independent assays based on the p67, p104 andTprgenes. The incidence of mixed infections in the Corridor disease endemic region of South Africa is significant, while the prevalence in buffalo outside the endemic area is currently low. A predicted increase ofT.sp. (buffalo)-like infections can affect future diagnoses where mixed infections occur, prompting the need for improvements in current diagnostics.