Date Published: August 21, 2011
Publisher: SAGE-Hindawi Access to Research
Author(s): Jean-Marc Reynes, Soa Fy Andriamandimby, Girard Marcelin Razafitrimo, Josette Razainirina, Elisabeth Marie Jeanmaire, Hervé Bourhy, Jean-Michel Heraud.
Background. Rabies virus (RABV) has circulated in Madagascar at least since the 19th century. Objectives. To assess the circulation of lyssavirus in the island from 2005 to 2010. Materials and Methods. Animal (including bats) and human samples were tested for RABV and other lyssavirus using antigen, ribonucleic acid (RNA), and antibodies detection and virus isolation. Results. Half of the 437 domestic or tame wild terrestrial mammal brains tested were found RABV antigen positive, including 54% of the 341 dogs tested. This percentage ranged from 26% to 75% across the period. Nine of the 10 suspected human cases tested were laboratory confirmed. RABV circulation was confirmed in 34 of the 38 districts sampled. No lyssavirus RNA was detected in 1983 bats specimens. Nevertheless, antibodies against Lagos bat virus were detected in the sera of 12 among 50 Eidolon dupreanum specimens sampled. Conclusion. More than a century after the introduction of the vaccine, rabies still remains endemic in Madagascar.
Rabies is a zoonotic disease caused by 11 viral species belonging to the genus Lyssavirus (Rhabdoviridae family), including the rabies virus (RABV), the most common [1–3]. These viruses are responsible for a meningoencephalomyelitis in mammals. Transmission of the viruses to a healthy mammal occurs mainly through bite or scratch by an infected mammal (the saliva is the infectious material). Bats are considered as the natural hosts of 10 of these viral species. However, dogs are the main source of infection in humans. It is estimated that 55,000 deaths per year worldwide are due to rabies infection with about 56% of which occur in Asia and 44% in Africa. In Africa and Asia, these deaths are responsible for 1.74 million disability-adjusted life years (DALYs) lost each year . There is no effective treatment when the disease is declared. However, there is an effective treatment against RABV and closed related lyssaviruses when applied as soon as possible after exposure. It prevents the onset of symptom and death and consists of local treatment of the wound, administration of rabies immunoglobulin (if indicated), and vaccinations against rabies .
Despite the introduction a century ago of the rabies vaccine in Madagascar, the recurrent positive laboratory diagnostic of rabies in dogs suggests that this zoonotic disease remains endemic in the island (Figure 1). The percentage of dogs detected infected by RABV along the 2005–2010 period (54%; 185/341) was in the same range of the one observed during the 1959–1991 period (57%; 1416/2475) . Dogs remain probably the principal vectors of RABV in the island. RABV strains associated to dogs in Madagascar were shown to belong to the cosmopolitan lineage [15, 16]. There was an evidence of RABV circulation in Antananarivo, the capital city. Antananarivo had, in 2007-2008, a density of dogs higher than many other urban areas in Africa, and the dog population was unrestricted and inadequately vaccinated against rabies, this characteristic favouring probably the dissemination of the virus . This situation is probably not limited to the capital city in Madagascar and may explain the rabies endemic situation in the island.
More than a century after the introduction of the vaccine against rabies in Madagascar, rabies remains endemic in the island. So far, preventing human rabies through dog rabies control and eventual elimination has been limited to local initiative. Madagascar, like other countries, is facing numerous public health issues. Because of the low incomes of the country and the lack of epidemiological data, this disease has not been prioritized, and a control program could not reasonably start. However, Madagascar is an island, and the elimination of rabies and its sustainability should be facilitated by the limited risk of introduction of rabid animals Therefore, the collection of such data (human and animal surveillance, dog ecology study, animal bites, etc.) should be promoted at first on pilot scale in order to validate the tools used. Afterward, data collection should be expanded to the rest of the country, while a pilot rabies control program (canine vaccination, canine population management, human postexposure prophylaxis, education, information, etc.) should start on pilot sites and then extended to the rest of the country.