A better way forward for rabies control in India?

Tamil Nadu, a state in Southern India with a population of 77.9 million people, could improve upon its current rabies control strategy and reduce its human rabies deaths by 90% if it embraced the One Health concept that links the health of animals to the heath of humans more fully.

A new study has demonstrated the risks and costs of the current strategy, which relies on providing vaccination (PEP) to people bitten by dogs and with just 34% of owned dogs vaccinated against rabies. With this approach, over 31,000 individuals are treated with PEP for dog bites annually, (at a cost of $1.68 million), and the model predicted 82 annual human deaths from rabies, numbers that agree well with the reported data from 2014. Clearly, although PEP is provided free, not everyone is able to access it in time to prevent the fatal disease from developing.  However, using local data and modelling, the study suggested a cost-effective way to improve upon it, by incorporating interventions aimed at supporting the health of the stray dog population.

Rabies is a classic example of a One Health disease, where control measures in the dog population can benefit human health. Tamil Nadu has recently established a pioneering One Health committee to facilitate the cross sectoral collaboration needed, and this study will support their efforts to provide the most cost-effective solution to protecting people from rabies.

Starting from their model of the current situation, the authors considered additional strategies involving vaccination only, or vaccination and sterilisation, of between 100,000 and 500,000 dogs per year, out of a total population of 1.65 million dogs. These strategies focused primarily on the stray dog population (estimated at 700,000 dogs). Even targeting this small additional fraction of the total dog population, the impact was dramatic, with human rabies deaths predicted to fall steeply within just 2 to 3 years. Annual human rabies deaths could be reduced to fewer than 10 after five years if 200,000 stray dogs (around 13% of the total dog population) were vaccinated each year, and down to just 6.4 deaths annually if dogs were sterilized as well as vaccinated. Importantly, sterilisation was not predicted to affect the number of dogs, but to reduce turnover in the population. Because of decreased competition for resources, all stray dogs are predicted to live longer when sterilization programs are in effect, and vaccinated animals will comprise an increasing fraction of the total population.

The Animal Welfare Board of India already stipulates that municipalities should vaccinate and sterilize stray dogs, but cost is critical to how widely these recommendations are enacted. Using data already collected on the cost of providing services in a small part of the state, the study estimated state-wide programmatic costs and concluded that several of the interventions, those focussed on vaccination alone, would be a cost-effective (according to WHO standards) way to reduce the toll of the disease in people. The combined vaccination and sterilization of dogs approach, though more effective at controlling rabies, was deemed considerably more expensive and consequently less cost-effective than just vaccinating dogs.

Costs are always the key in rabies control. In the future, it is hoped that injectable canine sterilization methods could realise the benefits of sterilization in a much more cost effective way, but currently the infrastructure required for sterilization operations in shelters is a huge impediment that limits widespread use. Catching dogs on the streets is also relatively costly, and the authors also suggest pilots to see if owners would bring their dogs to vaccination points in sufficient numbers to enable a vaccination team to reach a much higher target for the number of dogs vaccinated. This could also be very cost effective if used alongside vaccination of street dogs.

By providing a detailed analysis of the current and possible future rabies control strategies, the study provides exactly the sort of data that policy makers need to make informed decisions on how best to invest in rabies control efforts.

Although this is a case study for Tamil Nadu, many aspects of the findings should be applicable across India, a country struggling with approximately a third of the global human deaths from rabies. Tamil Nadu has a relatively efficient delivery system for free PEP, but this is not the case everywhere in India. In those areas where PEP is harder to come by, the authors conclude that the benefits of canine vaccination are likely to be even greater, and are the only way to reduce the risk to human lives in the long term.

 

Written by Louise Taylor, based on the paper “One Health approach to cost-effective rabies control in India” published by Fitzpatrick et al. in PNAS in December 2016.