Sensitivity of Nigerian field isolates of Trypanosoma vivax and Trypanosoma congolense to commonly available trypanocides

ObjectiveTo assess Nigerian field isolates of Trypanosoma congolense (T. congolense) and Trypanosoma vivax (T. vivax) to commonly available trypanocides (isometamidium chloride, homidium chloride and diminazene aceturate).MethodsThirty-six Yankasa sheep of both sexes were used for the study. The sheep were screened for ecto and endoparasites, and acclimatized for 2 weeks before the commencement of the experiment. The animals were randomly divided into six groups of six sheep each. Two groups (A and B) were infected intravenously with phosphate buffer solution dilute infected blood of approximately 2.0×106 of T. vivax and two other groups (E and F) were also infected intravenously with blood containing the same number of T. congolense. The remaining two groups served as uninfected controls. Of the two T. vivax infected groups, one was further divided into three sub-groups of two animals each and each of the sub-groups was treated with different trypanocides 9 days after the establishment of parasitaemia. The same treatment was carried out on the T. congolense infected groups. The other infected groups were left untreated. All the animals were monitored for 8 weeks post infection. Prepatent period of 6 d was recorded for both parasite species.ResultsT. vivax was found to be resistant to homidium chloride but sensitive to diminazene aceturate and isometamidium chloride at the recommended doses. Conversely, T. congolense was found to be resistant to all the three trypanocides used at the recommended doses.ConclusionsAlthough, resistance to trypanocides exists, it was observed to be more prominent with T. congolense than T. vivax infected sheep.