Cost-description of a pilot parenteral vaccination campaign against rabies in dogs in N'Djaména, Chad.

In the discussion about policies and strategies for rabies prevention in developing countries, intervention costs arise as a major issue. In a pilot mass vaccination campaign against rabies in N'Djaména, Chad, 3000 dogs were vaccinated. We assessed vaccination coverage and cost, showing the cost per dog vaccinated for the public sector and for society. An extrapolation to city level calculated the approximate cost of vaccinating all 23 600 dogs in N'Djaména. In the pilot mass campaign with 3000 dogs the average cost per dog was 1.69 euro. to the public and the full societal cost was 2.45 euro. If all 23 600 dogs in N'Djaména were vaccinated, the average cost would fall to 1.16 euro to the public and 1.93 euro to society. Private sector costs account for 31% of the cost to vaccinate 3000 dogs, and 40% of the cost to vaccinate 23 600 dogs. Mass dog vaccination could be a comparatively cheap and ethical way to both control the disease in animals and prevent human cases and exposure, especially in developing countries. The cost-effectiveness of dog vaccination compared with treating victims of dog bites for prevention of human rabies should be further assessed and documented.

[Impact of canine demography on rabies transmission in N'djamena, Chad]. / La démographie canine et son importance pour la transmission de la rage humaine à N'djaména.

A transversal study using the clustering technique was carried out in 600 households to estimate dog-population density in the city of N'Djamena and evaluate the knowledge of the inhabitants concerning the risk of rabies. Dog-population density as estimated by negative binomial modelling was 0.03 dogs per person. The dog population estimated taking into account the extrapolated human population for 2001 was at 23 575 dogs (95% confidence interval, 14579-37921 dogs). Three-fourths of inhabitants reported that they had heard of rabies. Most respondents knew some rabies symptoms such as frothing at the mouth, restlessness, and aggressivity. In case of dog-bite injury many respondents said that they would seek care in medical facilities, e.g., health-care centers, hospitals and veterinary clinics, but some said they would also use traditional remedies, witch-doctor services, and self-medication. More than half of the respondents believed that symptomatic rabies could be cured. Because of confinement and feeding needs stray dogs are common. The canine vaccination rate is low (19%) for various reasons including limited financial resources, absence of transportation, unavailability of vaccination facilities, ignorance and negligence. Since access to health care after exposure can be difficult, mass vaccination of dogs is the recommended strategy to control rabies in cities like N'Djamena. Cooperation of all those involved in rabies control is necessary to promote the education and awareness action necessary to promote canine vaccination and reporting of exposure cases to competent authorities.

Incidence of canine rabies in N'Djaména, Chad.

This work describes for the first time the incidence risk of passively reported canine rabies, and quantifies reported human exposure in N'Djaména (the capital of Chad). To diagnose rabies, we used a direct immunofluorescent-antibody test (IFAT). From January 2001 to March 2002, we were brought 34 rabies cases in dogs and three cases in cats. Canine cases were geographically clustered. The annual incidence risk of canine rabies was 1.4 (95% CI: 1.2, 1.7) per 1000 unvaccinated dogs. Most of the rabid dogs were owned-although free-roaming and not vaccinated against rabies. Most showed increased aggressiveness and attacked people without being provoked. Eighty-one persons were exposed to rabid dogs and four persons to rabid cats (mostly children<15 years old). Most of the exposed persons were neighbours or family members of the animal owner. Most exposures were transdermal bites, but nearly half of all exposed persons did not apply any first wound care or only applied a traditional treatment. In N'Djaména, humans are often exposed to canine rabies but do not use the full-course post-exposure treatment and wound care is insufficient. Most rabid dogs would be accessible to parenteral vaccination. Pilot vaccination campaigns are needed to determine the success of dog mass vaccination in N'Djaména as a way to prevent animal and human rabies.

Coverage of pilot parenteral vaccination campaign against canine rabies in N'Djaména, Chad.

Canine rabies, and thus human exposure to rabies, can be controlled through mass vaccination of the animal reservoir if dog owners are willing to cooperate. Inaccessible, ownerless dogs, however, reduce the vaccination coverage achieved in parenteral campaigns. This study aimed to estimate the vaccination coverage in dogs in three study zones of N'Djaména, Chad, after a pilot free parenteral mass vaccination campaign against rabies. We used a capture-mark-recapture approach for population estimates, with a Bayesian, Markov chain, Monte Carlo method to estimate the total number of owned dogs, and the ratio of ownerless to owned dogs to calculate vaccination coverage. When we took into account ownerless dogs, the vaccination coverage in the dog populations was 87% (95% confidence interval (CI), 84-89%) in study zone I, 71% (95% CI, 64-76%) in zone II, and 64% (95% CI, 58-71%) in zone III. The proportions of ownerless dogs to owned dogs were 1.1% (95% CI, 0-3.1%), 7.6% (95% CI, 0.7-16.5%), and 10.6% (95% CI, 1.6-19.1%) in the three study zones, respectively. Vaccination coverage in the three populations of owned dogs was 88% (95% CI, 84-92%) in zone I, 76% (95% CI, 71-81%) in zone II, and 70% (95% CI, 66-76%) in zone III. Participation of dog owners in the free campaign was high, and the number of inaccessible ownerless dogs was low. High levels of vaccination coverage could be achieved with parenteral mass vaccination. Regular parenteral vaccination campaigns to cover all of N'Djaména should be considered as an ethical way of preventing human rabies when post-exposure treatment is of limited availability and high in cost.