Melarsomine hydrochloride (Cymelarsan®) fails to cure horses with Trypanosoma equiperdum OVI parasites in their cerebrospinal fluid.

The research article is about a study conducted to evaluate the effectiveness of Cymelarsan (melarsomine hydrochloride) in treating horses afflicted with dourine, a sexually transmitted disease caused by Trypanosoma equiperdum. The results showed that, while Cymelarsan could eliminate the parasites from the horses’ blood, it was unsuccessful in eliminating the parasites from their central nervous system.

Study Background and Objective

• The main aim of this research was to ascertain the effectiveness of a drug called melarsomine hydrochloride (also known as Cymelarsan) in curing dourine in horses.
• Dourine is a sexually-transmitted disease in horses, caused by a parasite called Trypanosoma equiperdum, which can severely affect their nervous system.
• Despite the use of Cymelarsan for treating other forms of Trypanosoma infections in animals, its efficacy in dealing with Trypanosoma equiperdum was unknown.

Research Methodology

• The research team utilized eight Welsh pony mares infected with T. equiperdum that showed a presence of parasites in their cerebrospinal fluid.
• The treatment protocol to be evaluated involved administering 0.5 mg/kg of Cymelarsan daily over a span of 7 days.
• Two horses were kept untreated as controls. Three horses received the treatment 36 days post-infection, and the final 3 were treated 16 days post-infection.

Findings

• Following treatment with Cymelarsan, all the horses showed an improvement in terms of parasite clearance from the blood, stabilization of rectal temperature, and an relative enhancement in mean packed cell volume levels.
• However, even after treatment, living parasites were rediscovered in the cerebrospinal fluid of all treated horses, suggesting that Cymelarsan failed to eradicate the parasites from the central nervous system.

Conclusion

• This study indicates the inability of Cymelarsan to completely treat horses infected with Trypanosoma equiperdum as it can’t reach parasites located in the central nervous system.
• As such, the study suggests avoiding the use of Cymelarsan for treating horses suffering from the nervous form of dourine, thus aiding in better informed treatment strategies.