Although donkeys are considered to be more resistant to trypanosomes, they are often seen causing severe clinical disease, particularly anaemia, lethargy and boor body condition, in immuno-compromised animals due to stress from overwork, poor management practices and low quality diets. Studies made by The Donkey Sanctuary in Kenya showed a high prevalence of both tsetse and none tsetse transmitted trypanosomes. T. congolense and T. brucei sp are the most highly prevalent tsetse transmitted trypanosomes while T. vivax is the second most prevalent, next to T. congolense. Infection prevalence of T. vivax as high as 30% were diagnosed in Kenya and Ethiopia using parasitological techniques. These prevalences could have been higher had they been diagnosed using molecular techniques, as it was shown by the study made in Gambia, in which they found an infection prevalence of 87% using PCR.
Dourine is mostly diagnosed in horses from the highland regions in Ethiopia. Recent serological study made in Ethiopia, however, revealed not only in donkeys but across all agro-ecological zones. However, as the CFT does not differentiate between the infection of Dourine and Surra, it is difficult to know the true epidemiology of these diseases among equids where they both exist. Although Surra is reported in donkeys from different countries, it is not reported in donkeys in Ethiopia. However, Surra is endemic in camels in the arid and semi-arid regions of Ethiopia. The recent migration of camels to the mid-lowland areas during the dry season in search of feed might spread the disease among equids in the area.
A recent study made in Gambia by Glasgow University, funded by The Donkey Sanctuary, showed a fatal neurological syndrome among donkeys and horses caused by trypanosomosis. The aetiological agent of this emerging neurological syndrome has been established based on the presence of trypanosomes in the brain of affected animals. However, given the genetic homology between T. evansi, T. brucei brucei and T. equiperdum, it was not possible to confirm which one of these is causing this devastating condition. To solve this mystery and identify the species of trypanosome involved, study on further molecular characterization of cerebral trypanosomosis is underway in Gambia, a project funded by The Donkey Sanctuary.
The infection of trypanosomes in donkeys raises certain questions that need to be addressed. Given the high infection prevalence in the donkey population and associated diseases:
- Are they really carriers/resistant to trypanosomosis?
- The welfare implication of trypanosomosis in donkeys.
- What would be the role of donkeys in the epidemiology of trypanosomosis?
- The impact of exclusion of donkeys in the control of animal trypanosomosis?