Rabies around the World

Customarily, the level of international resources committed to the control of an infectious disease is a response to the associated human morbidity and mortality. For most infectious diseases, these data adequately reflect the deserved public health attention.

It is difficult, however, to estimate the global impact of rabies by using only human mortality data. Because vaccines to prevent human rabies have been available for more than 100 years, most deaths from rabies occur in countries with inadequate public health resources and limited access to preventive treatment. These countries also have few diagnostic facilities and almost no rabies surveillance.

Underreporting is a characteristic of almost every infectious disease in developing countries, and increasing the estimated human mortality does not in itself increase the relative public health importance of rabies. There is, however, one often neglected aspect of rabies that does affect perception of its importance.

Rabies is not, in the natural sense, a disease of humans. Human infection is incidental to the reservoir of disease in wild and domestic animals; therefore, a more accurate projection of the impact of rabies on public health should include an estimate of the extent to which the animal population is affected and the expense involved in preventing transmission of rabies from animals to humans.

An additional figure is needed to complete the global picture of rabies. The best estimates of the impact of rabies on a country and the public health resources available within that country for rabies control are found in data for the number and distribution of cases of rabies in domestic animals. Despite evidence that control of dog rabies through programs of animal vaccination and elimination of stray dogs can reduce the incidence of human rabies, exposure to rabid dogs is still the cause of over 90% of human exposures to rabies and of over 99% of human deaths worldwide.

The cost of these programs prohibits their full implementation in much of the developing world, and in even the most prosperous countries the cost of an effective dog rabies control program is a drain on public health resources. The estimated annual expenditure for rabies prevention in the United States is over US$300 million, most of which is spent on dog vaccinations.

An annual turnover of approximately 25% in the dog population necessitates revaccination of millions of animals each year, and reintroduction of rabies through transport of infected animals from outside a controlled area is always a possibility should control programs lapse. Reservoirs of wildlife rabies, virtually unknown in Asia and tropical regions, are also potential sources of rabies infection for dogs in Europe and North America.