Trypanosoma evansi causes a trypanosomosis known as ‘surra’. It affects a large number of wild and domesticated animal species in the world. The principal host species varies geographically, but camels are particularly affected. It is an arthropod-borne disease; several species of haematophagous flies, including Tabanids and Stomoxys, are implicated in transferring infection as mechanical vectors. In Brazil, vampire bats are also involved in a unique type of biological transmission. The general clinical signs of T. evansi infection are not sufficiently pathognomonic for diagnosis. Laboratory methods for detecting the parasite are required. In early infection, when the parasitaemia is high, examination of wet blood films, stained blood smears or lymph node materials can reveal the trypanosomes from blood or lymph samples. In more chronic cases, when the parasitaemia is low, examination of thick blood smears, as well as inoculation of laboratory rodents are required. Several primer pairs targeting the subgenus or the species-specific (T. evansi) parasitic DNA sequences are available for diagnosis by polymerase chain reaction (PCR) and DNA probe. Serological tests using specific antibody responses and a variety of antibody detection tests have been introduced for laboratory and field uses. The most relevant are immunofluorescence test (IFAT), enzyme linked immunosorbent assays (ELISA) and card agglutination test (CATT/T. evansi). T. evansi, like other pathogenic trypanosomes induce a generalized immune-suppression of both humoral antibody response and T-cell mediated immune responses. As a result, in the long term, the host's immune responses fail and it succumbs to either the overwhelming parasite load or to secondary infection, consequently leading to occurrence of the trypanosome-induced immunopathology. Keywords: Immune suppression, molecular, parasitological, Serological, Trypanosome evans
