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Could oral vaccines be the answer to India’s rabies problem?

Read time: 4 mins
9 Apr 2019
Could oral vaccines be the answer to India’s rabies problem?

Most Indian cities have a ‘dog problem’—multiplying numbers of free-ranging dogs found scavenging for food in garbage dumps. An obvious consequence of such dumping is the spread of diseases from dogs to humans. Rabies, a preventable viral infection of mammals that spreads to one another through the bite of a rabid animal, is one of them. India witnesses about 20,800 human deaths due to rabies each year—more than a third of global deaths—costing the country USD 2.3 billion. Mass vaccination of dogs is known to result in a rapid decline in the spread of the disease, although it is no small task in a country like ours. Hence, the existing vaccination campaigns do not turn out to be entirely successful.

In a recent study, researchers from The Roslin Institute and The Royal (Dick) School of Veterinary Studies, UK, worked with an international non-profit organisation called Mission Rabies, to study the efficiency of using oral baits, which contain anti-rabies vaccine, to vaccinate free-ranging dogs. Since such oral vaccines are not yet approved for use in India, they conducted the study with dummy packs that acted as placeholders for oral vaccines. The study, conducted in Goa, was funded by the Dogs Trust Worldwide and published in the journal Vaccine X.

“The development of efficient, scalable methods to repeatedly vaccinate a high proportion of the roaming dog population is the only way to avoid the indefinite provision of post-exposure prophylaxis, suffering caused by rabid dog bites and detrimental impact on tourism and agriculture industries in developing countries”, say the authors of the study.

In India, street dogs are vaccinated against rabies either by a small number of local communities, who feed or take care of dogs in the neighbourhood or through mass vaccination drives organised by city councils. These drives involve a team of skilled workers who catch free-roaming dogs using nets, vaccinate them, and then release them. These vaccines are parenteral and administered through a needle prick. However, catching free-roaming dogs in open areas is a challenge as they become cautious of the catching teams and escape, often being left out from vaccination drives.

The researchers of the current study used an oral bait with a dummy container covered with a piece of pigskin and placed in a sachet of commercial dog food. These baits were held out to dogs spotted by a team of two people riding a bike. There was also another team of seven people who followed the catch-vaccinate-release method to vaccinate the dogs. During the two weeks of the study, the researchers measured the efficiency of both these methods in successfully vaccinating the dogs.

The study found that the oral bait approach was more effective than the catch-vaccinate-release (CVR) method as it could access 35 dogs per person per day as compared to 9. Almost 80% of the sighted dogs could be accessed for vaccinating, compared to only 63% by the CVR method. The oral bait method was also cost efficient as it incurred just about a quarter of what the CVR method requires. The researchers estimate that if a two-week nation-wide vaccination campaign is launched, the oral bait method would need only 293,000 staff as against a whopping 1.1 million otherwise required.

However, parenteral vaccinations are not going away, say the researchers. “Parenteral vaccination will continue to be the primary choice for animals that can be readily handled because of the greater control over the certainty of administration and high rates of protection in dogs of different ages and immunocompetence”, they say. On the flip side, oral baits could inconvenience residents if children came in contact with the bait, or if the bait gets picked up by crows, rats or cats.

With our cities growing rapidly, human-dog conflicts are only going to increase and studies like this to counter such attacks and keep the society safe are necessary.

“This study indicates that should oral rabies vaccinations be available, it would likely benefit both operation efficiency and vaccination coverage in the free-roaming dog population and therefore may be of considerable benefit to rabies control activities in Goa and similar settings,'' conclude the researchers.