Pathogenesis of Experimental Schistosoma Bovis in Goats AtDifferent Levels of Infection

Abstract

Schistosoma bovis is an important veterinary and economical problem in the Sudan and other African, Mediterranean and Middle Eastern countries. Schistosomiasis causes severe outbreaks associated with high mortality rates among cattle, sheep and goats. Experimental; work on schistosomiasis involved the establishment of the complete life cycle of the parasite under laboratory conditions. An active breeding colony of the suitable snail host was established to provide a steady supply of cercariae for goats’ infection. The effect of experimental Schistosoma bovis infection on the clinical and pathological alternations was investigated in male goats (10-12month old). Twenty goats were divided into four groups A, B C and D. body weight and haemogram were measured for every week of experiment. Each animal in group A, B and C was infected with 500, 2000 and 5000 Schistosoma bovis cercariae percutaneously respectively. Animals in group D were kept as uninfected control. Serum and faecal samples were collected after infection. The experimental goats were slaughtered by the end f the experiment (27 weeks after infection) for worm recovery and tissue egg count. The representative tissue portions wee fixed and processed routinely for histopathology. Infected goats developed clinical signs of illness 6 to 8 weeks for group A, B and C xiii respectively. These included inappetance, dull appearance, general weakness and sunken eyes. The appearance of symptoms coincided with the start of oviposition and passage of schistosome eggs in faeces. The results obtained showed significant decrease between the infected groups in body weights, haemoglobin concentration, total RBC counts and albumin values whereas total WBC counts, total protein and globulin showed no significant increase. Faecal egg counts, worm recovery and tissue egg counts showed significant changes associated with the level of infection. The main histopathological findings in the livers of infected animals were granuloma formation and hepatocelular swelling and vacuolation. Ova granuloma were also noticed in the lung, lymph node and intestine. Glomerulo-inertial nephritis was observed in the kidneys. Haemosiderin pigment was deposited in the spleen. In the heart, myocarditis was observed. These lesions were frequently encountered in tissue of animals of group C followed by group B and were scarcely detected in tissues of group A.