Comparative experimental studies on Trypanosoma isolates in mice and response to diminazene aceturate and isometamidium chloride treatment

The current study was undertaken from December 2015 to May 2016 with the aim of determining and comparing the pathogenicity and response to diminazene aceturate (DA) and isometamidium chloride (ISM) treatment in experimentally infected mice with trypanosome isolates from Jawi and Birsheleko areas of northwest Ethiopia. A total of 42 mice were used for the experiment. These mice were randomly assigned in to 7 groups of 6 mice per group. Three of the groups (Group 1, 4 and 5) were inoculated with trypanosome isolated from Jawi and three other groups (Group-2, 6 and 7) were inoculated with trypanosome isolated from Birsheleko and the remaining one group (Group 3) was negative control. Each experimental mice were received 0.3 ml of positive blood at the 10(5) parasites/ml from donor animals intraperitoneally while negative control group were received 0.3 ml sterile water. The mice were clinically observed daily during the study period. Parameters including level of parasitaemia, body weight, PCV and hemoglobin value were recorded once per week for ten consecutive weeks post infection. Trypanocidal treatment was given on day 21 post infection when peak parasitaemia was detected in groups (Group 4-DA-Jawi, 5-ISM-Jawi, 6-DA-BRSH and 7-ISM-BRSH). The treatment doses for DA was at 28 mg/kg and for ISM at 4 mg/kg. In all experimental groups during study period when the mice showed severe clinical signs and at the end of the experiment they were euthanized with 70% ethanol for gross and histopathological examinations. The parameters measured during the study period revealed markers leading to pathological changes in all infected groups. Parasitaemia were detected early in the Jawi isolate infected groups compared to the Birsheleko groups. All infected mice showed clear clinical manifestation of depression, weight loss, reduction in feed intake and huddled together in the corner of the cage. Significant (P < 0.05) reduction was observed in the mean PCV and hemoglobin value of s infected mice compared to the negative control. The mean PCV values of Birsheleko isolate infected group was significantly (P < 0.05) lower than Jawi isolate infected group. This study showed that treatment with either DA or ISM were unable to clear parasitaemia indicating the presence of drug resistance problems for both isolates. Relative improvement in clinical and pathological changes was observed as compared with untreated infected groups. Gross and histopathological lesions were observed in infected groups. In conclusion, the current study suggests the presence of strain difference in virulence between isolates and the drugs unable to cure infections indicating the presence of resistance problems necessitate further molecular characterization of the strains and drug resistance detection in the natural host.