Evaluating the impact of targeting livestock for the prevention of human and animal trypanosomiasis, at village level, in districts newly affected with T. b. rhodesiense in Uganda

Abstract

Background: Uganda has suffered from a series of epidemics of Human African Trypanosomiasis (HAT), a tsetsetransmitted disease, also known as sleeping sickness. The area affected by acute Trypanosoma brucei rhodesienseHAT (rHAT) has been expanding, driven by importation of infected cattle into regions previously free of the disease.These regions are also affected by African Animal Trypanosomiasis (AAT) demanding a strategy for integrateddisease control.Methods: In 2008, the Public Private Partnership, Stamp Out Sleeping Sickness (SOS) administered a single dose oftrypanocide to 31 486 head of cattle in 29 parishes in Dokolo and Kaberamaido districts. This study examines theimpact of this intervention on the prevalence of rHAT and AAT trypanosomes in cattle from villages that had (HAT+ve) or had not (HAT-ve) experienced a recent case of rHAT. Cattle herds from 20 villages were sampled and screenedby PCR, pre-intervention and 6-months post-intervention, for the presence or absence of: Trypanosoma brucei s.l.;human infective T. b. rhodesiense; Trypanosoma vivax; and Trypanosoma congolense savannah.Results: Post-intervention, there was a significant decrease in the prevalence of T. brucei s.l. and the human infectivesub-species T. b. rhodesiense in village cattle across all 20 villages. The prevalence of T. b. rhodesiense was reduced from2.4% to 0.74% (P<0.0001), with the intervention showing greater impact in HAT-ve villages. The number of villagescontaining cattle harbouring human infective parasites decreased from 15/20 to 8/20, with T. b. rhodesiense infectionmainly persisting within cattle in HAT+ve villages (six/eight). The proportion of T. brucei s.l. infections identified ashuman infective T. b. rhodesiense decreased after the intervention from 8.3% (95% CI= 11.1-5.9%) to 4.1% (95% CI = 6.8-2.3%). Villages that had experienced a recent human case (HAT+ve villages) showed a significantly higher prevalencefor AAT both pre-and post-intervention. For AAT the prevalence of T. vivax was significantly reduced from 5.9% to 0.05% post-intervention while the prevalence of T. congolense increased from 8.0% to 12.2%. Conclusions: The intervention resulted in a significant decrease in the prevalence of T. brucei s.l., human infectiveT. b. rhodesiense and T. vivax infection in village cattle herds. The proportion of T. brucei s.l. that were human infective,decreased from 1:12 T. brucei s.l. infections before the intervention to 1:33 post-intervention. It is clearly more difficult toeliminate T. b. rhodesiense from cattle in villages that have experienced a human case. Evidence of elevated levels ofAAT in livestock within village herds is a useful indicator of risk for rHAT in Uganda. Integrated veterinary andmedical surveillance is key to successful control of zoonotic rHAT.