Ticks and tick borne diseases

Ticks effect some 800 million cattle and a similar number of sheep, mainly in the tropics, causing weight loss, damaging hides and transmitting serious diseases. The CSIRO Long Pocket group has earned an international reputation for strategic ecological tick research, incorporating development of models that can simulate the population dynamics of the various species. At the same time, the CSIRO Division of Tropical Animal Science has developed models that deal with the epidemiology of babesiosis.
Much of the research has concerned the cattle tick Boophilus microplus. In addition to its native range stretching from Japan through Indonesia to India, this single-host tick infests the Australian tropics and subtropics and has been introduced onto Africa and the Americas. Studies of a three-host species of more temperate zonesHaemaphysalis longicornis have also provided experience with this important class of ticks. These two species are representative of the two classes that cause almost all the serious tick and tick-borne disease problems in developing countries.
The models have increased understanding of tick ecology world-wide, especially in Africa, where joint studies with FAC have shown that the Australian work has application. Trials on different species in different environments there have already applied Australian conclusions with some success. However, continuing progress with ecological problems depends on further development of collaborative research with other countries, using data collected overseas to operate and refine the models in Australia.
This project has regional rather than national scope and covers several African countries south of the Sahara. It has three broad aims. The first is to continue and develop collaborative work in progress in Burundi, Kenya, Zambia and Zimbabwe. Results emerging from that work will support the other two aims: to adapt and apply the Australian models to African ticks and tick-borne diseases; and to provide specific guidelines for experimental trials to implement biological strategies for tick control in the region.
Zimbabwe supports the largest-scale co-operative program, mainly because it can provide suitable research facilities. Also, it contains two of the most serious ticks in AfricaAmblyomma hebraeum in the lowveld areas and Rhipicephalus appendiculatus in the highveldwhich transmit Heartwater and East Coast Fever. As well as measurement of the economic damage these species cause to cattle, the Zimbabwe program includes ecological research in more detail. Designed in collaboration, this research relates to climatic effects on tick survival, host resistance, sterility of hybrids between different tick species and management strategies in relation to environmental conditions.
Ecological studies, field monitoring and an experiment to measure economic damage are under way in Zambia, together with extensive epidemiological studies.
Results of regional studies of tick populations on untreated cattle in Burundi await analysis. Progress with the next phase depends on completing the analysis, to identify the relevant questions to ask.
Kenyan studies on host resistance and acaricide application in controlling R. appendiculatus, now in progress, require the tick models to integrate the information with the other ecological data becoming available.
The group in Australia will model the biological processes to simulate field populations, and then model the interrelations between damage and control in order to design optimal and robust management systems.