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

This research article describes a study conducted on horses in Ethiopia to understand the prevalence of dourine, a serious equine disease. The study used a combination of clinical observations, parasitological analysis, serological tests, and DNA-based techniques to assess the horses. Interestingly, they found trypanosome DNA in the blood of horses that showed disease symptoms but didn’t have detectable parasites in their fluids.

Study Location and Initial Inquiry

• The research was carried out in the Bale province of the Ethiopian highlands, specifically focusing on horses.
• The preliminary step of the study included a rapid questionnaire analysis, indicating that dourine, locally known as “Dirressa”, is a significant health concern for horses in this region.

Investigation and Findings

• A total of 121 horses suspected of having dourine were examined using various methods including clinical observation, parasitological examination, serological investigation, and DNA-based techniques.
• Common clinical symptoms noted among the horses were incoordination of hindlegs, swelling of external genitalia, and emaciation.
• Parasitological analysis included the haematocrit centrifugation technique (HCT), a method used to detect trypanosomes (the pathogens responsible for dourine). Interestingly, no trypanosomes were detected in the horses’ blood, genital washes, or tissue fluids.

DNA Detection and Conclusion

• Despite the lack of directly observable parasites, DNA testing showed a different result. Trypanosome-specific DNA products were amplified using Polymerase Chain Reaction (PCR) and discovered through DNA probe hybridization in the blood samples of 29 horses. All of these horses were serologically positive for dourine.
• The positive PCR results had a significant correlation with the symptom of external genitalia swelling.
• The presence of trypanosome DNA gives compelling evidence to affirm that dourine is highly prevalent in this area, even if the causative parasites were undetectable by conventional parasitological methods.
• The PCR assay in this study thus provides a sensitive tool for diagnosing active infections in endemic areas such as this one, especially where usage of trypanocidal drugs is common.