In Ethiopia, horses hold an important place with a share of 16% of total livestock cash value and are essential for transportation, in agricultural-,economic- and in social life. Efficient livestock production is prevented by diseases of which T.equiperdum is the most threatening one of all. T.eq., a venereal transmitted disease, is endemic in Ethiopia and is considered the most important health problem threatening equines in most parts of the world. Until recently no accurate diagnostic test was available, and specific knowledge about pathogenesis, host immunity and transmissions is limited. The disease has a long incubation period, and it is unclear when and how the affected animal is transmitting the disease. The project aims to exam the incubation period, infectiveness of disease and possible purification of semen of infected animals. Host immune reaction and predisposition places will be studied so to gain more insights in the disease evolution and to be able to adjust or modify possible treatments in the future