Can dog rabies be eliminated in Africa?
More than just vaccine is needed to eliminate dog rabies. Many processes like systemic surveillance and public engagement are also necessary. The following text provides information about components of a One Health disease elimination.
Dog rabies control and elimination by dog mass vaccination is effective, and in this way, dog rabies has been strongly reduced or even eliminated in several countries (Hampson et al. 2007). Yet, its control is stagnating or even re-emerging in many parts of the world, especially in Africa and Asia. Depending on the context, the cross-sector nature of dog rabies involving dogs, other mammals and humans requires a systemic integrated approach when aiming towards elimination. While effective vaccines are available to interrupt dog rabies transmission and protect exposed humans, control and elimination of dog rabies is not merely an operational problem. It is a science challenged by the complexity of the processes involved and by the fundamental properties of the biology of dog rabies.
Components of a science of dog rabies elimination
Social determinants and public engagement
Effective interventions against dog rabies rely on important enabling public conditions. Not only do public or private veterinary services need to be sufficiently staffed in order to be able to cover the area of intervention, but sufficient human and veterinary laboratory capacity with the ability to diagnose dog rabies and possibly even characterise virus isolates is needed. Implementing dog rabies mass vaccination requires sufficient public funds and the managerial capacity to organise and operate vaccination teams. Above all a societal consensus is needed by including all actors in transdisciplinary stakeholder processes (Hirsch Hadorn et al. 2008). Thereby all involved stakeholders contribute to identify priority actions and create trust between the different actors in dog rabies control actions (Schelling et al. 2008).
Systemic surveillance of dog rabies includes adequate diagnostic capacity and an existing disease surveillance system (Kayali et al. 2003). Surveillance of human dog bites in conjunction with dog rabies incidence is important to assess the public health impact and its economic consequences (Cleaveland et al. 2002; Frey et al. 2013). The effects of mass dog vaccination on animal and public health can be assessed when correlating it with sufficiently long time series’ of dog rabies and human dog bite exposure prior to an elimination campaign (Zinsstag et al. 2009). Such data is often missing and makes the evaluation of intervention effectiveness difficult. Dog rabies incidence should be complemented by molecular epidemiological studies characterising the circulating virus strains prior to its elimination (Dürr et al. 2008). The sequencing of virus isolates from newly observed cases after a mass intervention can then inform on possible ongoing transmission or newly introduced strains.
Understanding the disease ecology and dog-human attitudes, practices and behaviours guides the design of interventions with the highest effect. For this purpose, dog ecology studies provide knowledge on dog population composition, numbers and reproduction, which are essential for the planning of effective campaigns (Gsell et al. 2012, Mindekem et al. 2005). Culturally sensitive Knowledge-Attitude-Practice (KAP) studies on dog human relationships are essential because of highly diverse human attitudes towards dogs, ranging from using them as pets to employing them as watchdogs or even to consider them for human food. Human attitudes towards dogs determine the degree of confinement of dogs and the willingness to vaccinate them against rabies (Mindekem et al. 2005).
- Equity effectiveness
The effectiveness of an intervention is the product of the vaccine efficacy times the achieved coverage. The coverage, or proportion of animals effectively reached by mass vaccination, is determined by the vaccine availability, accessibility, affordability, acceptability and adequacy. Furthermore, it depends on the service provider compliance and the adherence to mass vaccination by the animal holder (Obrist et al. 2007).
Understanding the determinants of the effectiveness of an intervention requires a close interdisciplinary collaboration between, amongst others, vaccine biology, health systems research, health economics, social and cultural sciences and animal health. Even if each intervention factor alone has a relatively high performance, they are related to each other in a multiplicative way (Zinsstag 2011). This may lead to very low community effectiveness, even below the threshold to interrupt the transmission of rabies. Yet, a detailed understanding of the intervention factors is critical for achieving a successful intervention (Zinsstag et al. 2011).
Understanding the effectiveness of an intervention is a core element of the science of rabies elimination. Novel quantitative models of intervention effectiveness should allow for identification of the most sensitive effectiveness factors, which need to be harnessed to make an intervention successful. With such a new effectiveness method, we could show that the reason for the low coverage of a small scale dog rabies mass vaccination in Bamako, Mali was mainly due to the lack of information (Muthiani et al. 2015).
From our research on dog rabies elimination in African cities and brucellosis control in Mongolia, we have learned that, above all, the monitoring and evaluation of vaccination coverage is a critical element for the follow up of an effective intervention (Kayali et al. 2003). Often, the basic principles of random sampling proportional to size are not understood, and it does not help if vaccination coverage assessments are only done in vaccinated dogs. A basic epidemiological understanding is essential for a successful implementation of a mass vaccination campaign. Vaccination coverage data, ie the proportion of effectively vaccinated animals, combined with field epidemiological seroprevalence and sequence data of isolated strains can be used to validate the effectiveness of the intervention as predicted by models like the ones cited above (Zinsstag et al. 2005).
Intervention methods should be carefully analysed within a given political and socio-economic context. Cross-sector economic analyses provide a societal perspective which could lead to the sharing of intervention cost between the livestock and public health sector (Zinsstag et al. 2009). To achieve elimination, novel financing instruments should be examined, such as development impact bonds (DIB) that are currently assessed for the elimination of sleeping sickness (Trypanosoma brucei rhodesiense) in Uganda (Welburn in: Zinsstag 2015). In this way, risks are shared between national governments, institutional donors and private investors (Zinsstag et al. 2007). Another precedent is the successful elimination of rinderpest which could be re-invigorated for the elimination of dog rabies.
Mathematical Model Frameworks (optional)
Optionally, mathematical modelling of the transmission dynamics of dog rabies could be used to follow up the effectiveness of interventions. Such models are the backbone to intervention economic analysis and can be used to assess the animal-human interface (Zinsstag et al. 2009). Mathematical models of rabies should be combined with molecular strain characterisation using full sequencing to address the risk of re-introduction into a previously rabies-free zone.
The way forward
Dog rabies elimination is achievable in developing countries. Above all, it requires a societal consensus addressing issues like compensation or intervention types which should not be decided without involving the dog owners. Successful examples of disease elimination show that all actors need to be involved from the start, as all of them play an important role. Specifically the public health and animal health sectors should work as closely together as possible. Regional approaches with support from the Global Alliance for Rabies Control (GARC), for example involving African or Asian regions, analogous to the successful control in Latin America (Hampson et al. 2007), will be needed to address cross border transmission. In this way dog rabies control would probably make a significant practical contribution to create trust and peace building. The proposed science of dog rabies elimination does not stand alone, it can learn from other initiatives, like the science of malaria eradication (Zinsstag 2013). Further orientations could aim to combine, for example, rabies and distemper mass vaccination. We could also think about a locally adapted extended farm package including dog rabies, echinococcosis, brucellosis, anthrax and Foot and Mouth disease. Rabies can be eliminated but we need to work all together in an evidence-based systemic way.
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