Non-Transforming Theileria Parasites of Ruminants

Abstract

Infection with non-transforming, benign Theileria species is generally characterized by the lack of schizont development in leucocytes and the absence of fatal lymphoproliferation. The occurrence of T. buffeli, T. orientalis or T. sergenti can easily be overlooked owing to the fact that they cause predominantly subclinical infections in endemic areas. It is becoming increasingly apparent, however, that they have a worldwide distribution. Clinical cases have been reported in Japan (Baek et al. 1992a; Minami et al. 1980) and Korea and T. buffeli has been reported in Kenya (Young et al. 1992). In Southern Europe, clinical cases are rare but the infection appears to be prevalent as shown serologically, microscopically and by molecular diagnostic techniques such as the polymerase chain reaction (PCR) (Papadopoulos et al. 1996; Ceci et al. 1997; Savini et al. 1998). A fatal case associated with a mixed infection of two types (see below) has also been reported in Missouri, USA (Chae et al. 1999b) and the parasite could also be detected in the salivary glands of Amblyomma americanum and Dermacentor variabilis ticks infesting cattle. Also in Southern Europe, there have been reports of mixed infections with T. buffeli and T. annulata (Gubbels et al. 1999; Georges et al. 2001).