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

Abstract

S U M M A R YBuffalo-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.

A review of Theileria diagnostics and epidemiology

“…It also implies that the specific parasitaemia range of a species may determine its practical LOD. As such, >95% of the T. parva population in African buffalo have parasitaemias >0.00001%, which is well above the determined detection limit (Pienaar et al., 2011a). The same holds for T. sp.…”

“…Sensitivity of the RLB is severely affected by the fact that universal primers are used and these are depleted by the predominant species present, thereby suppressing the signal from less abundant template (Pienaar et al., 2011a). The sensitivity of the hybridisation assay for T. parva (Sibeko et al., 2008) is similarly affected by the presence of T. sp.…”

Geographic distribution of Theileria sp. (buffalo) and Theileria sp. (bougasvlei) in Cape buffalo (Syncerus caffer) in southern Africa: implications for speciation

“…Theileria sp. (buffalo) was found in African buffalo in Uganda, Kenya and southern Africa, with no substantive reports that cattle can be infected (Oura et al 2004(Oura et al , 2011Pienaar et al 2011a). Theileria sp.…”

“…(buffalo) and T. sp. (bougasvlei) was subsequently shown to be present in buffalo from southern Africa, to be apathogenic and has not yet been found in cattle (Allsopp et al 1999;Oura et al 2004Oura et al , 2011Mans et al 2011a;Pienaar et al 2011a). Theileria sp.…”

An Overview of Disease-Free Buffalo Breeding Projects with Reference to the Different Systems Used in South Africa

“…The brown ear ticks Rhipicephalus appendiculatus, R. duttoni and R. zambeziensis are considered to be the main vectors of T. parva, which causes East Coast fever, CD and January disease in cattle [17,18]. CD results when buffalo derived T. parva is transmitted via ticks from buffalo to cattle, which results in mortality, although evidence has shown that cattle that survive this infection then go on to become immune to it [19][20][21][22]. Indeed, Yusufmia et al (2010) [23] found evidence that suggests that cattle may also be subclinical carriers of T. parva.…”