THE EFFECTIVENESS OF A TARGETED RE-TREATMENT PROGRAMME IN REDUCING THE PREVALENCE OF TRYPANOSOMIASIS IN CATTLE IN UGANDA

Louise Hamill, Richard Selby, Christine Amongi Acup, Beatrix von Wissmann, Kim Picozzi, Susan Welburn

Research output: Other contribution

Abstract

Human African trypanosomiasis (HAT), also known as sleeping sickness, is a fatal parasitic disease, caused by two very similar sub species of trypanosome, Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense, both of which are transmitted to humans via an insect vector, the tsetse fly (Bruce, 1895). They occur in Sub Saharan Africa, T. b. gambiense occurring in West and Central areas and T. b. rhodesiense occurring in the east. Untreated both parasites are 100% fatal, T. b. rhodesiense in around 6 months, while T. b. gambiense has a chronic disease progression, causing death in 2 – 10 years. The picture is complicated by the fact T. b. rhodesiense is able to infect cattle without causing any clinical disease, and it is now widely accepted these animals constitute a major reservoir of disease for humans (Fevre et al., 2001). In Uganda, the northward movement of infected cattle has lead to new out breaks of sleeping sickness in previously disease free areas, posing a serious public health risk. The drugs currently available to treat human disease have many side effects, and are difficult to administer in resource poor settings. The drugs available for treating animals are safe, effective, cheap and easy to administer in the field.

The “Stamp Out Sleeping Sickness (SOS)” programme aims to halt northward spread of T. b. rhodesiense sleeping sickness in Uganda by mass trypanocidal treatment of the cattle reservoir. These drugs are not only effective against the sleeping sickness parasites, but also against the similar parasites Trypanosoma vivax and Trypanosoma congolense. These parasites cause African Animal Trypanosomiasis (AAT), and so there is the potential to improve both human and animal health. AAT causes serious economic losses, estimated to be as much as US $4.5 billion per year (Budd, 1999). SOS Phase 1 targeted the most northerly of the districts newly affected by this parasite, and a successful overall reduction in T. b. rhodesiense was achieved. However post treatment monitoring revealed a cluster of villages in which this parasite remained present. Subsequently, re-treatment of these high risk areas was proposed.

This study aims to assess the impact of the SOS re-treatment intervention on the prevalence of T. vivax, T. b. brucei and T. b. rhodesiense by analysing cattle blood samples from 20 villages within the re-treatment area. Cattle from these villages were sampled immediately before and 6 months post re-treatment. Samples were subjected to PCR based methods for the detection of parasite DNA.

The re-treatment programme was successful in reducing the overall prevalence of trypanosomiasis in the targeted area. A significant drop was observed between the baseline (31.8%) and 6 month (18.2%) sampling (P=0.0001). T. b brucei, T. b. rhodesiense and T. vivax were all detected, and the prevalence of each individual species dropped significantly. T. b. rhodesiense was present in 15 of the 20 villages sampled at baseline. 6 months after treatment the number of affected villages had greatly reduced from 15 to just 7. With the exception of one village, which was negative at baseline, all of the other villages which were positive at 6 months were also positive at the baseline sampling. Therefore, the re-treatment has cleared T. b. rhodesiense from 9 of the original 15 positive villages. The geographical distribution of T. b. rhodesiense in the retreatment area has reduced, but persists in two discrete clusters. Due to this continued presence of T. b. rhodesiense in the cattle reservoir further treatments may be needed to stop the resurgence and geographic spread of human disease.

Original languageEnglish
TypePoster presentation at the Houses of Parilement, SET for Britain 2010
Publication statusPublished - 8 Mar 2010

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