Estimating the global burden of endemic canine rabies

Abstract

Background: Rabies is a notoriously underreported and neglected disease of low-income countries. This study aims to estimate the public health and economic burden of rabies circulating in domestic dog populations, globally and on a country-by-country basis, allowing an objective assessment of how much this preventable disease costs endemic countries.

Methodology/principal findings: We established relationships between rabies mortality and rabies prevention and control measures, which we incorporated into a model framework. We used data derived from extensive literature searches and questionnaires on disease incidence, control interventions and preventative measures within this framework to estimate the disease burden. The burden of rabies impacts on public health sector budgets, local communities and livestock economies, with the highest risk of rabies in the poorest regions of the world. This study estimates that globally canine rabies causes approximately 59,000 (95% Confidence Intervals: 25-159,000) human deaths, over 3.7 million (95% CIs: 1.6-10.4 million) disability-adjusted life years (DALYs) and 8.6 billion USD (95% CIs: 2.9-21.5 billion) economic losses annually. The largest component of the economic burden is due to premature death (55%), followed by direct costs of post-exposure prophylaxis (PEP, 20%) and lost income whilst seeking PEP (15.5%), with only limited costs to the veterinary sector due to dog vaccination (1.5%), and additional costs to communities from livestock losses (6%).

Conclusions/significance: This study demonstrates that investment in dog vaccination, the single most effective way of reducing the disease burden, has been inadequate and that the availability and affordability of PEP needs improving. Collaborative investments by medical and veterinary sectors could dramatically reduce the current large, and unnecessary, burden of rabies on affected communities. Improved surveillance is needed to reduce uncertainty in burden estimates and to monitor the impacts of control efforts.

Fig 1. Model framework used in this study for estimating the global burden of canine rabies.

Probability steps correspond to the probability that a bite is by a rabid animal (RP); that the victim received post-exposure prophylaxis, PEP, (PP); and, in the absence of PEP, that the bite victim developed rabies (DP). Data inputs (Table 1) are shown in red and model outputs in blue. Red arrows show estimated relationships (Fig 2). DALY = Disability-Adjusted Life Year; HDI = Human Development Index. Further details are given in Table 1.

Fig 2. Functional relationships estimated between A) rabies incidence in domestic dogs and average biannual dog vaccination coverage and B) probability of receiving post-exposure prophylaxis (PEP) and the Human Development Index.

Upper inset in A shows the relationship on a log scale and the lower inset shows the relationship between rabies incidence in livestock and vaccination coverage in domestic dogs. Grey shading shows the 95% confidence intervals of the fitted relationships.

Fig 3. The distribution of the global burden of rabies: A) human rabies deaths, B) per capita death rates (per 100,000 persons), and C) expenditure on dog vaccination (per 100,000 persons).

Countries shaded in grey are free from canine rabies.

Fig 4. Model sensitivity to parameter uncertainty.

PEP = post-exposure prophylaxis.

Fig 5. Division of costs associated with rabies, prevention and control across sectors by region.

Inset shows proportional expenditure in different regions. The breakdown of costs by cluster is given in S1 Fig and Table 3 and detailed by country in S1 Table.