Abstract:
Buffalo-adapted Theileria parva causes 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 of T. parva. The official test is a realtime
hybridization PCR assay that amplifies the V4 hypervariable region of the 18S rRNA gene of T. parva, T. sp. (buffalo)
and T. sp. (bougasvlei). The effect that mixed T. parva and T. sp. (buffalo)-like infections have on accurate T. parva
diagnosis was investigated in this study. In vitro mixed infection simulations indicated PCR signal suppression at 100 to
1000-fold T. sp. (buffalo) excess at low T. parva parasitaemia. Suppression of PCR signal was found in field buffalo with
mixed infections. The T. parva-positive status of these cases was confirmed by selective suppression of T. sp. (buffalo)
amplification using a locked nucleic acid clamp and independent assays based on the p67, p104 and Tpr genes. 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 of T. sp. (buffalo)-like infections can affect future diagnoses
where mixed infections occur, prompting the need for improvements in current diagnostics.
