Rabies control in rural Africa: evaluating strategies for effective domestic dog vaccination

Abstract

Effective vaccination campaigns need to reach a sufficient percentage of the population to eliminate disease and prevent future outbreaks, which for rabies is predicted to be 70%, at a cost that is economically and logistically sustainable. Domestic dog rabies has been increasing across most of sub-Saharan Africa indicating that dog vaccination programmes to date have been inadequate. We compare the effectiveness of a variety of dog vaccination strategies in terms of their cost and coverage in different community settings in rural Tanzania. Central-point (CP) vaccination was extremely effective in agro-pastoralist communities achieving a high coverage (>80%) at a low cost (<US$2/dog) and was robust under various socio-economic, cultural and spatial factors. In pastoralist communities CP vaccination was costly (>US$5/dog) and inadequate (<20% coverage); combined approaches using CP and either house-to-house vaccination or trained community-based animal health workers were most effective with coverage exceeding 70%, although costs were still high (>US$6 and >US$4/dog, respectively). No single vaccination strategy is likely to be effective in all populations and therefore alternative approaches must be deployed under different settings. CP vaccination is cost-effective and efficient for the majority of dog populations in rural Tanzania and potentially elsewhere in sub-Saharan Africa, whereas a combination strategy is necessary in remote pastoralist communities. These results suggest that rabies control is logistically feasible across most of the developing world and that the annual costs of effective vaccination campaigns in Tanzania are likely to be affordable.

Fig. 1

Map of the Serengeti ecological region of northwestern Tanzania showing the location of the study villages in the agro-pastoral and pastoral zones, to the west and east of the Serengeti National Park (SNP), respectively. LGCA = Loliondo Game Control Area; NCA = Ngorongoro Conservation Area.

Fig. 2

Variation in vaccination coverage estimated by household questionnaire survey: (a) vaccination coverage levels achieved in 12 intensively followed up villages and (b) overall vaccination coverage levels achieved in the 6 study districts.

Fig. 3

Vaccination coverage versus distance from the central vaccination point. A logistic regression with binomial errors fitted to the proportional data demonstrates that coverage declines with distance from the central-point (p < 0.0001, gray line). The sample size for each coverage estimate was used to weight the regression; points in the figure are scaled by the log of the sample size. The theoretical target coverage of 70% recommended to control dog rabies is marked with a dashed line. Although there was some evidence for over-dispersion in this data, a logistic regression fitted to binary data for individual dogs, with exact binomial errors, was also highly significant.

Fig. 4

Reasons expressed by dog owners for not bringing dogs for vaccination.