Methods for Estimating the Risk of Rabies Transmission to Humans in the Lake Victoria Zone, Tanzania

Abstract

Canine rabies is endemic in Tanzania probably as a result of low dog vaccination coverage which is set between 10 and 20%. By the use of a model, this study aimed to develop methods for estimating risk of rabies transmission to humans, quantify the risks and make recommendations to minimize them. Data obtained from the Lake Victoria Zone were subjected to analysis by running Monte Carlo simulation using „Simulacion4‟ for 10 000 iterations. The findings suggested that, at a dog vaccination coverage of 10%, the probability of an individual human being dying from rabies following a bite from a rabid dog was 3.76×10^-5. With a human population of 8 509 170 million people found in the Lake zone in 2012, this probability corresponded to an estimated 8921 human dog bite cases and 220 human rabies deaths. This corresponded to an annual bite incidence of 104.8 bites/100 000 and an annual death incidence of 2.6 deaths/100 000 respectively. On the basis of extrapolating these data to the whole country, this probability corresponded to 1163 human rabies deaths per year. At a dog vaccination coverage of 70%, the probability of dying from rabies following a bite from a rabid dog reduced to 1.38×10^-5. The percent risk reduction was ˃60%. Sensitivity analysis showed that post-exposure prophylaxis had a stronger influence on the risk of dying from rabies compared to dog vaccinations. Correlation analysis showed that the correlation of dog vaccinations and the risk of dying from rabies was significant (r²= 0.95, P=0.0000).

Key words: model, vaccination coverage, simulacion, Monte Carlo