Enhanced one Health surveillance approaches to guide the elimination of dog-mediated rabies in Tanzania

Abstract

Rabies causes approximately 59 000 human deaths worldwide annually. A global target of zero human deaths from dog-mediated rabies has been set for 2030, and large-scale control programs are now advocated. However, there is limited surveillance and guidance on how rabies surveillance can be improved to increase the detection of rabid animals or to guide the management of rabies control programmes once elimination has been achieved or when its approached. Challenges to rabies elimination were investigated by undertaking detailed epidemiological studies collecting data from 2010/2011 to 2022; and enhancing surveillance using Integrated Bite Case Management (IBCM) across different settings in Tanzania from 2018 to 2022. In 24 districts, local government health and veterinary workers were trained to collect data through implementing IBCM, comprising risk assessments of bite patients by health workers and investigations of suspected rabid animals by livestock field officers. In addition, contact tracing was used to identify rabid animals, human rabies exposures and deaths, with additional whole-genome sequencing of viruses from rabies positive samples in 13 districts of Lindi and Mtwara region, including Pemba Island. From these data, transmission chains were probabilistically inferred, estimated case detection, quantified the public health burden in terms of numbers of rabies exposures, animal rabies cases, human rabies deaths and evaluated the impact and cost-effectiveness of a One Health approach to rabies surveillance and control. Reporting of bite patients at high risk of rabies exposure increased following the introduction of IBCM. Between 2011 and 2019, 688 probable exposures were identified in Southeast Tanzania, including 47 rabies deaths. Of 549 probable animal rabies cases identified: 303 were domestic dogs (55.2%) and 221 jackals (40.3%). Dog-to-dog transmission accounted for 40.1% of inferred transmission events, and wildlife-to-wildlife transmission accounted for approximately 32.6%, with the remainder from cross-species transmission. On Pemba Island, five transmission chains circulated from 2010. Rabid dogs, human exposures and deaths declined following the introduction and improved implementation of dog vaccination campaigns, and these transmission chains were eliminated by May 2014. In 2016 two introductions of dog rabies cases to the island that seeded re-emergence were identified. The ensuing outbreak was eliminated by October 2018 through reinstated island-wide dog vaccination. While post-exposure vaccines were highly cost-effective ($256 per death averted), their accessibility was limited and only dog vaccination interrupted transmission. A combined One Health approach rapidly eliminated rabies, was highly cost-effective ($1657 per death averted) and saved 20-130 families from rabid dog bites annually. Overall, IBCM greatly improved rabies detection and can be used to monitor the impact of mass dog

ii

vaccinations. In Tanzania domestic dogs appear to be the critical reservoir host of rabies, even in settings with evidence of wildlife transmission. Dog vaccination suppressed rabies in both dog and wildlife populations and reduced both public health and conservation risks. A One Health approach underpinned by dog vaccination and post exposure prophylaxes to animal bite patients is an efficient, cost-effective, equitable and feasible approach to rabies elimination, but needs scaling up across connected populations to sustain the benefits of elimination, as seen on Pemba, and for similar progress to be achieved elsewhere.