Clinical manifestation of experimental trypanosoma evansi infection in the dromedary camel and the effect of treatment on haematological, biochemical and serological values

Abstract

With the growing awareness of the unique role the camel plays in agriculture and environmental preservation, increasing attention is being focused on improving its productivity and health status, so as to improve and diversify the production capacity of the marginal lands. Information on individual parameters of the camel's haematological and biochemical values is largely inadequate. Because the haematological and biochemical profiles can be useful aids in diagnosis of certain diseases, the norm for these parameters need to be established. Trypanosoma evatisi (T. evnnsi) is one of the most economically important diseases of the camel and there is need to study this disease in detail. This study was carried out with the aim of elucidating some of the haematological and biochemical parameters in normal and T.evansi infected camels. Haematologicaland biochemical values in healthy dromedary camels were determined in eleven camels for a period of 4 weeks. These values correlated well with those established in other countries. Nine camels were artificially infected with T. evensi isolated from a naturally infected camel and passaged through mice. Two camels were used as non-infected controls. Four camels (Group A) were allowed to run with disease throughout the study period, while 5 camels (Group B) were treated with Cymelarsan at the recommended therapeutic dose of O.25mg/kg body weight by deep intramuscular injection at the onset of the clinical disease. Three out of 4 camels in group A died of the disease, while all camels in group B survived to the end of the experiment. The clinical signs manifested by the infected camels included inappetance, dullness, enlarged superficial lymph nodes, excessive bilateral lacrimation, ventral oedema, poor hair coat and emaciation. Pyrexia coincided or closely followed parasitaemia crises. Post mortem examination revealed excessive peritoneal and pericardial fluids, haemorrhages in the gastrointestinal tract (especially in the abomasum and small intestines), froth in trachea and lungs, congested meninges and kidneys and oedematous brain. Following infection PCY,RBCand HBlevels dropped rapidly in the first 3 weeks in all the infected animals. In group A camels, PCY, RBC and Hb levels continued to decline until they died or the study was terminated, while in the treated camels these parameters levelled off 4 weeks after treatment and started recovering. There was an increase in some enzyme activity notably AP, AST, CKand LDHafter infection even though there was no statistical significant difference in some of the enzyme changes when compared to the non-infected controls. Parasites disappeared f'rom peripheral circulation within 24 hours after treatment and were no longer detectable to the end of the study. Circulating antigens which were detected 2 weeks after infection were cleared within 10 weeks following treatment. In the 4 non-treated camels, antigens remained detectable throughout the study period. Thus, in this study baseline data of some haematological and biochemical values of the Kenya dromedary has been established. A comprehensive clinical picture of T. evansi infection in the dromedary camel has been recorded. The study has further demonstrated that T.evansi infection in camels is fatal, especially when no therapeutic intervention occurs and that the disease can manifest itself as an acute syndrome with camels dying within the first few weeks of infection. The disease causes changes in haematological and biochemical values. Cymelarsan, as used in this study, elicits complete cure in camels infected with T. evensi. Antigen-detection ELISA (Ag-ELISA) has been shown to be a more efficient assay in assessing the patent state of infection in infected camels and in evaluating the success of therapeutic intervention than the antibody-detection (Ab-ELISA)test.