The pathogenicity and molecular characterization of Trypanosoma vivax isolated from tsetse belt, Southern Sudan, in goats and sheep

Abstract

The present work was conducted to study the pathogenicity of T.vivax (DRSS06) isolated from the tsetse belt in South Sudan in goats and sheep. Comparison was also made with regard to levels of parasitaemia, clinical, haematological and biochemical parameters. In addition, gross lesions and histopathological changes were also recorded. Furthermore, the molecular characterization of the isolate of T.vivax (DRSS06) in the study has also been performed. The DRSS06 strain of T.vivax was isolated from tsetse belt, Raga city, South of Sudan. It was found to be highly pathogenic to both goats and sheep with 100% mortality rate in both species. The experimental animals composed of 16 goats, 8 were infected group and 8 as control. In addition, 11 sheep, 8 were infected group and 3 left as control group. The prepatent period was found to be a mean of 4.6+ 0.2 days in goats and 4.4+ 0.25 days in sheep. By the end of the study, there was a significant increase in pulse (p>0.01) and respiratory rates (p>0.01) in both species as compared to control groups. Moreover, the haematological changes in Hb, PCV and RBC were decreased significantly (p>0.01) in both species compared to control groups. The body temperature was significantly high (p>0.01) in the two infected groups and correlated with the high parasitaemia which fluctuated within a constant level without remission throughout the study period. However, parasitaemia is significantly higher in sheep compared to goats (p>0.05). The type of anaemia recorded in this study in infected goats was classified as macrocytic hypochromic in the second week and microcytic hypochromic at weeks 5, and 7 while in infected sheep it was normocytic normochromic at the early and microcytic hypochromic at the last vii week. The most important clinical signs exhibited were emaciation, pale mucous membranes, convulsions, torticollis, weakness, conjunctivitis, ear oedema, recumbency and high mortality rate. The outstanding gross lesions noticed were fluids in body cavities, gelatinous substances, adhesion, fragile liver, flabby heart and haemosidrosis in the kidneys. The histopathological changes observed were infiltration of lymphocytes and macrophages throughout the organs. Haemosidrosis and necrosis were shown in the liver and kidney. The brain and intestine were congested. Serum total proteins in infected goats and sheep decreased significantly (p>0.01) compared to control groups. Glucose levels dropped significantly (p>0.01) in both goats and sheep compared to control groups. Serum iron levels in infected goats decreased significantly (p>0.01) at weeks 1, 4, 5 and 7 and in sheep at wk 5 compared to control groups. Contrastingly, the infected sheep showed a significant increase in Fe at week 2 (p>0.01) compared to control group. Sodium levels decreased significantly (p>0.01) between week one and three in the infected goats and sheep compared to control groups. Potassium was decreased significantly (p>0.01) between week one and three in both species and increased significantly (p>0.01) at week 5 in goats and week 4 in sheep compared to control groups. Calcium and phosphorus levels decreased significantly (p>0.01) in goats and sheep compared to control groups. Serum urea levels in infected goats and sheep decreased significantly (p>0.01) at wk 4 in goats and wk 2 and 4 in sheep as compared with the controls. Serum creatinine in infected goats and sheep decreased significantly (p>0.01) compared with the controls. There were significant increase (p>0.01) of bilirubin values in the infected goats and sheep at wk 2 and one respectively compared to control groups. However, no signs of icterus were observed. Serum ALT in goats and sheep decreased significantly (p>0.01) compared to control groups. In contrast, significant increase (p>0.01) of AST levels were noticed in infected goats at wk 5 and in sheep at wk 4 as compared with the 8 controls. However, AST decreased significantly (p>0.01) at wk 7 in goats and wk 3 and 5 in sheep compared to control groups. Infected goats and sheep showed significant (p>0.05) decreased levels of ALP at wk 5 in goats and wks 2 and 5 in sheep compared with the controls. Nonetheless, in the infected goats a significance (p>0.05) increase at wk 7 was shown compared to control group. The life expectancy in goats was 42±14.6 days and in sheep was 33.9 ±7.4 days. It is significantly (p>0.05) higher in goats than in sheep. Thus, sheep seemed to be highly susceptible to DRSS06 strain of T.vivax than goats. In the present study, two isolates of T.vivax DRSS06 and T.vivax ILRAD Nigerian strain, West Africa were compared using random amplified polymorphic DAN (RAPD). No genetic similarity between them was found. It is concluded that the DRSS06 strain of T.vivax is highly pathogenic to both goats and sheep. In addition, the pathogenesis of the disease in the two species showed many changes