Development of diagnostic and control methodologies for animal trypanosomiasis (Surra) in Papua New Guinea, Indonesia, the Philippines and Australia

Indonesia, Papua New Guinea, Philippines

Dr Simon Reid
Phone: 08 9360 7423
Fax: 08 9310 4144
Email: s.reid@murdoch.edu.au

• Research Institute for Veterinary Science, Indonesia
• Dinas Peternakan, Irian Jaya, Indonesia
• National Agriculture Quarantine and Inspection Authority, Papua New Guinea
• University of Southern Mindanao, Philippines
• Department of Agriculture, Region XI, Philippines
• Balai Penyidikan Penyakit, Sulawesi, Indonesia
• University of Western Sydney, Australia

$600,002

01/01/2001 - 31/12/2003

01/01/2004 - 31/12/2005

Dr Peter Rolfe

The disease of animal trypanosomiasis (or surra) is caused by the protozoan parasite Trypanosoma evansi, transmitted by biting tabanid flies (March flies). The result of infection is an acute or chronic wasting, depending on host susceptibility and the virulence of the parasite strain. Many animals can be afflicted, including livestock and horses. The disease is found in much of the world, including all of the Philippines and Indonesia. Evidence from antibodies in blood samples shows that T. evansi may be present in parts of Irian Jaya. However, it is believed that Australia and Papua New Guinea may no longer be free of this disease.

Recent research has shown that pigs and deer could be efficient reservoir hosts for the parasite. Pigs and two species of wallaby common to Papua New Guinea and northern Australia, are believed to be highly susceptible to infection and suffer acute disease with a high mortality rate. Therefore if the disease is found in PNG or enters Australia, it would have a devastating effect on livestock and probably on many native marsupials.

Before any control programs could be designed, more knowledge was needed about the impact of T. evansi on livestock and the determinants of clinical disease. This would require sensitive and well-validated diagnostics tests, coupled with an understanding of the genetics of virulence in the different strains of T. evansi. To date there were no such effective tests, and drugs used in treatment had not been systematically evaluated.

Both Indonesia and the Philippines wanted to establish control mechanisms to reduce livestock infection and improve productivity. This project therefore involved both countries, along with Papua New Guinea and Australia, building on earlier research into the parasite carried out at James Cook University, Townsville (ACIAR project AS1/1996/150) that demonstrated the inadequacy of existing diagnostic tests.

The project aimed to develop accurate diagnostic tests for this parasitic disease, to establish more effective ways of controlling it, and to transfer this technology to neighbouring countries to improve surveillance and reduce the risk of disease entry to Australia.

The project began with a training workshop in Indonesia to transfer skills to all partner countries. These skills would enhance the capability for surveillance, as well as for further study of the parasite.
The experimental work started with screening trypanocidal drugs for activity against the parasite, looking for the most efficacious and cost-effective compounds for treatment of infection. The scientists tested the pathogenicity of the parasite in rodents and identified strains with high and low virulence which were then studied to determine the genetic differences and to find markers for pathogenicity.
The next stage was to apply molecular techniques to create highly sensitive and specific diagnostic tests for the presence of T. evansi in host blood and tissues.

The project's main scientific achievement is a considerably enhanced capability for effective surveillance of Surra in Irian Jaya, PNG and the Philippines. A network of researchers on T. evansi from Indonesia, the Philippines, Australia, PNG and external agencies such as ILRI is now firmly established.

The successful outcomes were achieved by the transfer of current diagnostic technologies which were then improved by identifying more specific and sensitive tests for serological diagnosis. The scientists developed molecular techniques for low-level detection of organisms in blood samples, identified genetic markers for pathogenicity of T. evansi and tested their usefulness in predicting outbreaks of clinical disease. They also investigated the efficacy of existing trypanocidal drugs for the treatment of T. evansi. The elucidation of the epidemiology of infection with T. evansi in Mindanao and Sulawesi was a significant and important contribution to understanding the disease in Asia. A secondary, vital achievement was development of techniques to collect and send blood and tissue samples to Australia in compliance with Australian quarantine standards.

The research to date suggests there are multiple factors involved in the development of outbreaks of Surra in the Philippines. The severity of outbreaks of Surra in Mindanao could be due in part to genetic differences compared to Indonesian isolates, and preliminary results using the mouse pathogenicity test suggest this. Pathogenic strains of T. evansi were identified in specific areas, indicating that control programs must focus on regions where acute clinical disease is most likely and that the response to notifications of clinical disease must be rapid to prevent death due to infection.

Further technology transfers to participating countries should improve the effectiveness of surveillance for T. evansi. The information gathered can then be incorporated into guidelines on the most cost-effective treatments of infection with T. evansi. This should improve the success of treatment and control programs based on treatment of infected animals.