Detection of trypanosome DNA in serologically positive but aparasitaemic horses suspected of dourine in Ethiopia.

A field study of horses was conducted in the province of Bale, Ethiopian highlands. A rapid questionnaire analysis indicated that dourine, known as "Dirressa", is a major health problem of equines in this area. A total of 121 horses suspected of dourine were examined by use of clinical, parasitological, serological and DNA based techniques. Incoordination of hindlegs (76%), swelling of external genitalia (48.8%) and emaciation (39.7%) were the most common clinical signs observed. Using the haematocrit centrifugation technique (HCT), no trypanosomes were detected in blood, genital washes or tissue fluids. By contrast, trypanosome specific DNA products were amplified by PCR and subsequently detected by DNA probe hybridization in blood samples of 29 horses (29/104), all serologically positive by CFT and/or ELISA. Positive PCR results were significantly associated with swelling of external genitalia (P< 0.05). There is strong evidence, although there was no direct detection of T. equiperdum, that dourine is highly prevalent in the area, a finding which is in accordance with earlier reports. It is concluded, that this PCR assay provides a very sensitive tool in the diagnosis of active infections of dourine in endemic areas where trypanocidal drug use is common.