Assessment of Trypanocidal Drug Resistance on Trypanosoma congolense in Amaya District of South West Shewa, Ethiopia

Abstract

The study was conducted in January to April of 2013 to assess occurrence of diminazene diaceturate and isomethamidum chloride hydrochloride resistant Trypanosoma congolense isolates in Ameya district, Ethiopia. Initial survey was conducted on 51 cattle owners with the help of questionnaires to assess potential risk factors for trypanocidal drug resistance and trypanosomosis prevalence in the study area while the experimental study was carried out at Ambo on 10 calves purchase from Ambo market, tested and placed in Ambo University farm for two months prior to the artificial infection. The animals were divided into two groups {Diminazene diaceturate(Group-I) and Isometamidium chloride(Group-II)} of five calves. The survey result on trypanocidal drug administration revealed that 9 (17.6%) of the respondents self administer the drugs to their animals, 22 (43.1%) by veterinary professionals and the remaining 20(39.2) by other farmers, community health workers (CHWs) or drug smugglers. It also showed that 80.4% of the respondents treated only sick cattle, where as 19.6% treated sick and healthy cattle as well. The interviewees replied that trypanocidal drugs was used by 49% for the last 15-20 years, and 31.4% for the last 25-30 years ,and 13.7 % for the last 5-10 years. In addition drug sell by non professionals, prolonged use of trypanocidal drug (up to 40 years) and use of trypanocidal drugs by farmers might have resulted in under-dosing with any of the three trypanocidal drugs (diminazene diaceturate, isometamidium chloride and homidium bromide). Drug sensitivity revealed that T. congolense developed resistance to both doses of diminazene diaceturate(7% solution) at 3.5 and 7 mg/Kg body weight in Group I ,and to isometamidum chloride hydrochloride(1% solution) at therapeutic doses of 0.5 mg/Kg body weight and double dose of 1.0 mg/Kg body in Group II. There was a 100% relapse following treatment with therapeutic dose of both drugs where as a 60% and 100% relapses recorded following double doses treatment with diminazene diaceturate and isometamidum chloride hydrochloride, respectively. During the 100 days of trial period there was statistically significant difference (P<0.05) in mean packed cell volume (PCV) of the two groups at therapeutic dose of treatment while no significant difference (P>0.05) was observed at double doses. In conclusion, Trypanosoma congolense infection was found to have developed high level of resistance against the tested drugs in the area. Therefore, strict regulation and supervision of trypanocidal drugs usage together with integrated vector control methods are suggested in order to alleviate trypanocidal drug resistance. Furthermore, invention and introduction of new drugs and detailed experimental works are also recommended.