Trypanosome infection in dromedary camels in Eastern Ethiopia: Prevalence, relative performance of diagnostic tools and host related risk factors

- We conducted a cross-sectional study on camel trypanosome infection in Eastern Ethiopia.
- Depending on the diagnostic test, positivity rates ranged from 2% to 24%.
- Latent class analysis estimated an overall prevalence of 19%.
- All infections were due to Trypanosoma evansi except one with Trypanosoma vivax.
- Risk factors for infection were poor body condition and age.

A cross-sectional study was conducted in Chifra and Dewe districts of Afar region, Eastern Ethiopia, to determine the prevalence, agreement between diagnostic tests and host related risk factors of trypanosome infection in camel. An overall prevalence of 2%, 24.1%, 21.3%, 9.5% and 7.8% was recorded with respectively Giemsa stained thin blood smear, CATT/T. evansi, RoTat1.2 PCR, 18S PCR and ITS-1PCR in a cohort of 399 animals. Only one T. vivax infection was confirmed by TvPRAC PCR indicating T. evansi as the predominant species affecting camels in the study area. No single animal was positive when tested with T. evansi type B specific EVAB PCR. There was slight agreement between the CATT/T. evansi and the molecular tests. Among the PCR methods, RoTat 1.2 PCR yielded a significantly higher positivity rate compared to 18S PCR and ITS-1 PCR. There was no significant difference in the positivity rate observed in each gender of camels (p > 0.05). The positivity rate was significantly higher in camels with poor body condition and in older animals when tested using the CATT/T.evansi or RoTat 1.2 PCR (p > 0.05). Camels that tested positive with all tests had significantly lower PCV's (p < 0.05). This study provides further evidence that T. evansi is endemic in the Afar region of Ethiopia. The latent class analysis indicated an estimate overall prevalence of 19% (95% CI: 13-28). Moreover, the model indicated low sensitivity of CATT/T. evansi (43%) and the PCR tests (39-53%) but higher specificity of the PCR tests (86-99%) and low specificity of CATT/T. evansi (80%). This study suggests that improved sensitivity and reliability of the tests would help diagnosis of trypanosomosis. Further studies are required to determine the prevalence of clinical disease and losses due to trypanosomosis.