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Background to the disease
The Wellcome Trust
Current control measures
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Current control measures

There are currently three available methods for the control of tropical theileriosis, all of which have shortcomings which limit their usefulness:


Chemotherapy

Chemotherapy
The theilericidal compound buparvaquone is marketed for therapeutic use and has high efficacy when used in the early stages of the disease, although it is less effective if treatment is delayed. Moreover, animals that recover following treatment often remain unproductive for several months. These limitations are a consequence of extensive destruction of the immune system caused by the disease, which compromises the ability of treated animals to clear residual infection and also increases susceptibility to intercurrent infection. Therapy is expensive, costing US$50-80 per animal, and is not always accessible or affordable by small-holder farmers. Moreover, treatment failure is increasingly being reported and the recent discovery of drug-resistant parasites casts serious doubt on the sustainability of this method of control.


Prevention of tick infestation
Prevention of tick infestation
Control of tropical theileriosis by preventing tick infestation requires more or less continuous application of acaricides during seasons of tick challenge and is therefore expensive and difficult to sustain, particularly for poor livestock keepers. In addition to environmental concerns, continuous use of acaricides is also known to result in selection of acaricide-resistant tick populations.

Vaccination
Vaccination
Live vaccines are currently produced by attenuating parasite-infected leukocytes for virulence by prolonged passage in vitro, and have been used successfully in several countries. However, the requirement for a high level of quality control, the dependence on a cold chain for vaccine distribution and the capacity of the vaccine parasites to establish persistent infections (and hence a perceived need to use locally derived stains for vaccination) makes these vaccines less than ideal. Additionally, it has recently been demonstrated that the carrier state, induced by live vaccination, adds an economic cost to productivity.

These deficiencies in currently available measures for controlling tropical theileriosis emphasise the need for more effective and sustainable control methods. This has allowed a series of objectives to be identified for this project.