An investigation of disease reservoirs in complex ecosystems: rabies and canine distemper in the Serengeti

Rabies virus (RABV) and canine distemper virus (CDV) have been implicated as the cause of dramatic declines in wildlife populations worldwide and rabies is considered a growing public health problem throughout much of the developing world. In Tanzania, recent severe epidemics of both diseases in Serengeti carnivores have been associated with the large population of domestic dogs (Canis familiaris) living in proximity to the protected areas, but many questions remain about their epidemiology, particularly with respect to the understanding of reservoir infection dynamics and patterns of viral maintenance and transmission in multi-host communities. This study examines all the available evidence for reservoirs of rabies in the Serengeti and presents data on the temporal and spatial dynamics of CDV in domestic and wild carnivores (dogs and lions [Panthera leo]) to help understand long-term patterns of infection in the two populations.Practical difficulties in detecting rabies in areas such as the Serengeti, where surveillance and laboratory confirmation of disease are severely constrained, limit the collection of epidemiological data, a critical step in identifying reservoirs of infection. A novel direct rapid immunohistochemical test (dRIT) as a field test for rabies surveillance was therefore investigated. Preliminary evaluation on frozen and glycerolated field brain samples under field and laboratory conditions showed a sensitivity and specificity equivalent to those of the direct fluorescent antibody (DFA) test, the gold standard in rabies diagnosis. Examination by molecular phylogenies of the genetic characteristics of RABVs isolated from a range of species revealed one single major variant belonging to the group of southern Africa canidassociated viruses (Africa lb), a high degree of genetic relatedness among viruses with no evidence for distinct virus-host associations, and patterns consistent with temporal direction of evolutionary change from dogs to other species. Overall, these analyses point to the domestic dog being responsible for supporting the cycle of a single virus variant in the ecosystem. Rabies incidence data available from the Serengeti (1991-2005) and data on the genetic characteristics of the virus were then used to draw conclusions on reservoirs of infection: domestic dog populations occurring at high densities were the only population essential for persistence, whereas other carnivores contributed to the reservoir as non-maintenance components. Serological and case morbidity/mortality data on CDV indicated that infection patterns in unvaccinated dog and lion populations were consistent with periodic re-introductions with no evidence for persistent infection, re-introduction of infection in vaccinated dog populations coincided with declines in vaccination coverage, but patterns of exposure were not different in vaccinated and unvaccinated populations, and circulation in lions did not appear to occur in the absence of infection in dogs, suggesting that dogs may be the only source of infection. The lack of evidence for long-term persistence in any of the populations suggests that no single population may be capable of independent maintenance, but a network of populations may constitute a maintenance community.Finally, the overall results are discussed in relation to the surveillance of rabies and the design of appropriate control strategies for rabies and CDV for the Serengeti ecosystem and areas of sub-Saharan Africa where both diseases occur. The qualities of the dRIT for rabies surveillance in field conditions and countries with limited diagnostic infrastructures and the potential benefits of its wider application in developing country settings are highlighted. Efforts directed at controlling infection in domestic dogs through mass vaccination programmes are expected to have the most significant impact on reducing or eliminating disease in all the other species. Elimination of CDV in dog populations would also provide definite insights into their role in disease persistence within a potentially complex reservoir system but questions remain about the cost-effectiveness of such an approach as a long-term management strategy for African wild carnivore populations

Invisible and ignored: lifting the lid on the problems of endemic zoonosez

No abstract available

Implementing Pasteur's vision for rabies elimination: the evidence base and the needed policy actions

It has been 129 years since Louis Pasteur's experimental protocol saved the life of a child mauled by a rabid dog, despite incomplete understanding of the etiology or mechanisms by which the miracle cure worked (1). The disease has since been well understood, and highly effective vaccines are available, yet Pasteur's vision for ridding the world of rabies has not been realized. Rabies remains a threat to half the world's population and kills more than 69,000 people each year, most of them children (2). We discuss the basis for this neglect and present evidence supporting the feasibility of eliminating canine-mediated rabies and the required policy actions

The Burden of Rabies in Tanzania and Its Impact on Local\ud Communities

Rabies remains a major public health threat in many parts of the world and is responsible for an estimated 55,000 human deaths annually. The burden of rabies is estimated to be around US$20 million in Africa, with the highest financial expenditure being the cost of post-exposure prophylaxis (PEP). However, these calculations may be substantial underestimates because the costs to households of coping with endemic rabies have not been investigated. We therefore aimed to estimate the household costs, health-seeking behaviour, coping strategies, and outcomes of exposure to rabies in rural and urban communities in Tanzania. Extensive investigative interviews were used to estimate the incidence of human deaths and bite exposures. Questionnaires with bite victims and their families were used to investigate health-seeking behaviour and costs (medical and non-medical costs) associated with exposure to rabies. We calculated that an average patient in rural Tanzania, where most people live on less than US$1 per day, would need to spend over US$100 to complete WHO recommended PEP schedules. High costs and frequent shortages of PEP led to poor compliance with PEP regimens, delays in presentation to health facilities, and increased risk of death. The true costs of obtaining PEP were twice as high as those previously reported from Africa and should be considered in re-evaluations of the burden of rabies

Addressing antimicrobial resistance by improving access and quality of care - A review of the literature from East Africa

Universal access to healthcare, including quality medicines, is a fundamental human right but is still out of reach for many in low- and middle-income countries (LMICs). An existing framework capturing variability of access to healthcare in low-resource settings includes the 5 dimensions: availability, accessibility, affordability, adequacy, and acceptability. This framework encompasses key components, including health infrastructure and means to access it as well as service organisation, costs, and factors that influence users’ satisfaction. However, in reality, the effectiveness of accessed healthcare is measured by the likelihood of a positive outcome. We therefore propose an expansion of this framework to include an additional dimension, “aspects of quality,” incorporating quality, which critically influences the ability of the accessed services to generate optimal health outcomes. Within this framework, we explore literature from East Africa likely relevant to a range of LMIC contexts, mainly focusing on the provision of widely used antimicrobials such as antimalarials and antibiotics. We argue that major inadequacies exist across all 6 dimensions of access and quality of drugs and their provision. While the global focus is on curbing excessive antimicrobial use to tackle the antimicrobial resistance (AMR) crisis, major constraints around access shape patients’ health-seeking decisions leading to potentially problematic practices that might exacerbate the AMR problem. We advocate for a holistic approach to tackling these inadequacies, encompassing all dimensions of access and quality of healthcare in order to improve health outcomes while simultaneously counteracting the AMR crisis

The Blueprint for Rabies Prevention and Control: A Novel Operational Toolkit for Rabies Elimination

Rabies is a prime example of a neglected tropical disease that mostly affects communities suffering from inequitable health care [1]. The false perception that rabies impacts on society are low is due to case under-reporting and limited awareness of the disease burden [2], [3]. Effective tools for elimination of terrestrial rabies are available [4]. While the sustained deployment of these tools has led to some remarkably successful interventions [5], [6], canine rabies continues to claim lives in rabies-endemic countries and areas of re-emergence, where >95% of human deaths occur as a result of bites by rabid domestic dogs [7], [8]. Control programs targeting dogs can effectively reduce the risk of rabies to humans [3], [9]. However, the design and implementation of such programs still pose considerable challenges to local governments, and a lack of easy-to-use guidelines has been identified as an important reason for this

Knowledge, Attitudes and Practices (KAP) about rabies prevention and control: a community survey in Tanzania

BACKGROUND: Despite being entirely preventable,canine rabies still kills 55,000 people/year in developing countries. Information about local beliefs and practices can identify knowledge gaps that may affect prevention practices and lead to unnecessary deaths. METHODOLOGY/PRINCIPAL FINDINGS: We investigated knowledge, attitudes and practices related to rabies and its prevention and control amongst a cross-section of households (n = 5,141)in urban and rural areas of central, southern and northern Tanzania. Over 17% of respondents owned domestic dogs (average of 2.3 dogs/household), >95% had heard about rabies, and >80% knew that rabies is transmitted through dog bites. People who (1)had greater education,(2)originated from areas with a history of rabies interventions,(3)had experienced exposure by a suspect rabid animal,(4)were male and(5)owned dogs were more likely to have greater knowledge about the disease. Around 80% of respondents would seek hospital treatment after a suspect bite, but only 5% were aware of the need for prompt wound cleansing after a bite. Although >65% of respondents knew of dog vaccination as a means to control rabies, only 51% vaccinated their dogs. Determinants of dog vaccination included(1)being a male-headed household,(2)presence of children,(3)low economic status,(4)residing in urban areas,(5)owning livestock,(6)originating from areas with rabies interventions and(7)having purchased a dog. The majority of dog-owning respondents were willing to contribute no more than US$0.31 towards veterinary services. CONCLUSIONS/SIGNIFICANCE: We identified important knowledge gaps related to, and factors influencing the prevention and control of rabies in Tanzania. Increasing knowledge regarding wound washing, seeking post-exposure prophylaxis and the need to vaccinate dogs are likely to result in more effective prevention of rabies; however, greater engagement of the veterinary and medical sectors is also needed to ensure the availability of preventative services

Driving improvements in emerging disease surveillance through locally-relevant capacity strengthening

Emerging infectious diseases (EIDs) threaten the health of people, animals, and crops globally, but our ability to predict their occurrence is limited. Current public health capacity and ability to detect and respond to EIDs is typically weakest in low- and middle-income countries (LMICs). Many known drivers of EID emergence also converge in LMICs. Strengthening capacity for surveillance of diseases of relevance to local populations can provide a mechanism for building the cross-cutting and flexible capacities needed to tackle both the burden of existing diseases and EID threats. A focus on locally relevant diseases in LMICs and the economic, social, and cultural contexts of surveillance can help address existing inequalities in health systems, improve the capacity to detect and contain EIDs, and contribute to broader global goals for development

Rabies control and elimination: a test case for One Health

One Health approaches have already been shown to be successful in controlling rabies in different parts of the world. In this article, the latest in Veterinary Record's series promoting One Health, Sarah Cleaveland and her colleagues at the University of Glasgow discuss why integrated strategies are needed to enhance the cost effectiveness of measures to control and eliminate rabies, particularly in low-income countries

Estimating the size of dog populations in Tanzania to inform rabies control

Estimates of dog population sizes are a prerequisite for delivering effective canine rabies control. However, dog population sizes are generally unknown in most rabies-endemic areas. Several approaches have been used to estimate dog populations but without rigorous evaluation. We compare post-vaccination transects, household surveys, and school-based surveys to determine which most precisely estimates dog population sizes. These methods were implemented across 28 districts in southeast Tanzania, in conjunction with mass dog vaccinations, covering a range of settings, livelihoods, and religious backgrounds. Transects were the most precise method, revealing highly variable patterns of dog ownership, with human/dog ratios ranging from 12.4:1 to 181.3:1 across districts. Both household and school-based surveys generated imprecise and, sometimes, inaccurate estimates, due to small sample sizes in relation to the heterogeneity in patterns of dog ownership. Transect data were subsequently used to develop a predictive model for estimating dog populations in districts lacking transect data. We predicted a dog population of 2,316,000 (95% CI 1,573,000–3,122,000) in Tanzania and an average human/dog ratio of 20.7:1. Our modelling approach has the potential to be applied to predicting dog population sizes in other areas where mass dog vaccinations are planned, given census and livelihood data. Furthermore, we recommend post-vaccination transects as a rapid and effective method to refine dog population estimates across large geographic areas and to guide dog vaccination programmes in settings with mostly free roaming dog populations