Abstract:
The Theileria are apicomplexan parasites transmitted by ticks to vertebrate hosts. Most Theileria species exhibit
some form of host or vector specificity, since under endemic conditions only a limited number of tick species act
as vectors and not all vertebrate hosts are able to maintain a persistent carrier state. Data for Theileria sp.
(buffalo) suggest host specificity for African buffalo (Syncerus caffer). However, T. sp. (buffalo) infections in
cattle co-grazing with African buffalo have been reported in Kenya and schizonts were cultured from these
infected cattle, raising questions regarding host specificity. A Corridor disease outbreak in 2013 on a ranch in
South Africa where cattle co-grazed with Theileria parva and T. sp. (buffalo) infected buffalo presented the
opportunity to investigate the possible carrier-state of T. sp. (buffalo) in cattle using real-time PCR analysis.
Almost all buffalo (n = 19, 95%) were infected with T. sp. (buffalo) and showed CP values (22-20) indicative of
high parasitemia similar to that observed for buffalo in endemic areas. Conversely, only ~14-27% cattle
(n = 69, 100, 96) were positive with CP values (31-40) suggesting low parasitemia and a carrier state epidemiology
different from African buffalo. Long term monitoring of T. sp. (buffalo) positive cattle showed that most
cattle lost their parasitemia or presented fluctuating parasitemia around the PCR assay detection limit. A single
splenectomized animal showed a persistent carrier state. The general trends and epidemiology observed in cattle
infected with T. sp. (buffalo) are similar to that seen for buffalo-adapted T. parva, for which a defined carrier
state in cattle has not yet been proven. The study suggests that cattle may be infected by T. sp. (buffalo) but are
not definitive hosts that play an important part in the epidemiology of this parasite.
