Abstract
Background:No outbreak has been reported onTrypanosoma evansiinfection in Malaysia ponies since 1983, and little is known about the interaction betweenT. evansiand ponies in the country. Therefore, an experimental study was designed to evaluate the pathogenicity of a local strain ofT. evansiin the local ponies.Method:For this purpose, four healthy local ponies were inoculated with 102live trypanosomes/kg body weight, whereas two ponies served as negative control. Blood samples and rectal temperature were collected on alternate days from both groups for 54 days. Physical examination comprised visible mucous membrane and any appearance of clinical signs were observed daily. The number of trypanosomes was estimated using the Neubauer haemocytometer method. Complete haemogram measurements were performed immediately using an automated blood cell counter and the data obtained was evaluated using the general linear model as linear regression. All infected ponies were salvaged treated with 7 mg/kg of diminazene diaceturate.Results:The four infected ponies developed parasitaemia on the 4thday post-infection (DPI), whereas the first high mean of parasites count was recorded on the 8thDPI. Parasitaemia was detected at a level that fluctuated throughout the infection period (30 days) in all infected ponies with a mean of 13.5x106 trypanosomes/ml blood on the 30thDPI. Successive peaks of pyrexia were accompanied by the peaks of parasitaemia and the highest temperature (39.4°C) was observed on the 20thDPI. Excessive weakness and a reduction of appetite fluctuated in the infected ponies during the infection and one animal died unexpectedly on the 23rdDPI. The mean values for RBC, PCV, Hb and thrombocyte count were significantly lower in the infected ponies than the control groups. Neutrophil and eosinophil were significantly declined after the onset of parasitaemia, whereas monocyte increased significantly in the infected group.Conclusion:The appearance of clinical signs and changes in haematological parameters suggests that Malaysian local ponies are susceptible toT. evansiinfection. Treatment of the infected ponies with the recommended dosage of diminazene diaceturate was successful in the surviving ponies.
Highlights
The ability of T. evansi to induce a severe surra in different hosts depends mainly on a number of factors, including the virulence of an individual strain, host susceptibility and local epizootiological conditions
No outbreak has been reported on Trypanosoma evansi infection in Malaysia ponies since 1983, and little is known about the interaction between T. evansi and ponies in the country
The four infected ponies developed parasitaemia on the 4th day post-infection (DPI), whereas the first high mean of parasites count was recorded on the 8th DPI
Summary
The ability of T. evansi to induce a severe surra in different hosts depends mainly on a number of factors, including the virulence of an individual strain, host susceptibility and local epizootiological conditions. Dogs and camels are reported to be the most susceptible hosts of T. evansi infection, developing an acute disease characterized by anaemia and high mortality if treatment is not administered [1]. A recent experimental study from India indicated that ponies succumbed to T. evansi infection with death and neurological symptoms [3]. An experimental infection of T. evansi in ponies in Brazil conducted by Marques et al [6] indicated an expression of neurological symptoms on 50% of the animals on the 77th DPI with one case of death on 66th DPI, an indication of chronic stage of the disease. In the present study, the dynamics of T. evansi infection was investigated in experimentally infected Malaysian ponies with emphasis on clinical signs, parasitaemia trend and haematological parameters. An experimental study was designed to evaluate the pathogenicity of a local strain of T. evansi in the local ponies
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