Rabies control in rural Tanzania: optimising the design and implementation of domestic dog mass vaccination programmes

Rabies is an ancient zoonotic disease that still persists as significant public health problem affecting largely poor and marginalized people in poor countries of the developing world. The disease is also a cause of substantial wildlife conservation concern and an economic burden to governments where it occurs. However, the disease is grossly under-reported in most developing countries, with the result that the burden of the disease is widely under estimated and rabies perceived to be an insignificant problem. Although human rabies is completely preventable, through vaccination of animal reservoirs and post-exposure prophylaxis (PEP) of people exposed to the virus, no effective large-scale control of rabies has been achieved in sub-Saharan Africa in the past 30 years and information is still needed to optimise and sustain dog vaccination programmes. In Chapter 2, data obtained through a mass domestic dog vaccination campaign in northwest Tanzania are used to investigate strategic factors that influence the design and effectiveness of domestic dog rabies vaccination campaigns in rural Africa. The findings of this study show the feasibility of controlling rabies in a wide range of agro-pastoral socio-economic settings in rural Tanzania through central point based vaccine delivery approach and demonstrate that the use of combined central point and community-based animal-health workers (CAHWs) offers an effective alternative to central point approach as a vaccine delivery strategy in remote and dispersed pastoral communities. In Chapter 3, the economic burden of rabies at the household level is evaluated; the study demonstrates that rabies is a substantial economic concern to households in rural Tanzania, disproportionately affecting households with low socio economic status. It is also shown that dog bite victims with low socio economic status are at higher risk of dying from rabies. The per capita cost for dog vaccination and potential benefits of domestic dog vaccination in agro-pastoral and pastoral communities are estimated in Chapter 4. The per capita cost for central point dog vaccination is estimated as $1.73 and 5.56 in the agro- pastoral and pastoral communities respectively. The study also shows that rabies control through domestic dog vaccination will results in substantial net benefits to the public health sector. In Chapter 5, using both cross sectional and longitudinal data, the impact of multivalent vaccination of domestic dogs against rabies, canine distemper, canine parvo virus and canine hepatitis virus on the demography of the dog population is investigated over two consecutive years, demonstrating a significant increase in survival and dog population growth in vaccinated dogs (vaccination zone) in comparison with unvaccinated (control zone) dog populations in adjacent areas. In Chapter 6 the study demonstrates a substantial decline in incidence of human and animal rabies as a result of dog vaccination. However, despite a decline in reporting of animal rabies cases and human bite injuries from suspected rabid dogs, use of PEP at district hospitals did not decline. In Chapter 7 data from previous chapters are used to parameterise a spatially explicit stochastic model to theoretically explore the optimal design of domestic dog mass vaccination campaigns in rural Tanzania. The results of the model demonstrate that inter-vaccination interval and vaccination coverage are likely to be critical factors in designing domestic dog mass vaccination programmes in rural Tanzania. In Chapter 8 the implications of the findings in previous chapters are discussed to show that rabies control is economically and logistically feasible in Tanzania and a multi sectoral approach to rabies control is proposed as a way forward for the country