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 (). 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) [9
]. 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
]. 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 [17
]. This situation is probably not limited to the capital city in Madagascar and may explain the rabies endemic situation in the island.
Several endemic or (few) introduced carnivorous mammals (Families Viverridae and Herpestidae) are present in Madagascar [18
]. So far, very few suspected animals from these species have been tested. One rabid confirmed human case was bitten by a fossa (Cryptoprocta ferox
) in Ihosy district, in 2007, and the strain obtained from this case was confirmed as a lyssavirus of the species RABV, phylogenetically closely related to those circulating in Malagasy dogs (data not shown). Consequently, the question of a possible vector in the wild terrestrial carnivorous mammals remains unanswered. This question is of importance considering a rabies control programme targeting the eradication of the rabies in the island.
Our extensive survey in bats failed to detect any lyssavirus associated to these mammals. The molecular technique we used to detect lyssaviruses was demonstrated to be sensitive, reproducible, and repeatable [11
]. Furthermore, virus isolation on new-born mice was considered sensitive as we isolated several viruses from the bats specimens, like Ife virus from the Malagasy straw-colored fruit bat (Eidolon dupreanum
) and Dakar bat virus from the Peters's wrinkle-lipped bat (Mormopterus jugularis
) (unpublished data). Low prevalence of active infection (detection of virus) has been observed in North American and European bats colonies (0.1 to 2.9%), especially in clinically normal bats [19
]. Because we sampled clinically normal bats and because our sampling size per site and per species was for the most about 100 animals (except for the site of the followup where we sampled about 750 animals), our negative results in detecting a lyssavirus are consequently not so surprising. Lyssavirus detection was also negative in brains sampled in 1987 and 1988 in Madagascar, from 59 little free-tailed bats (Chaerephon pumilus
]. Interestingly, we got serological evidence that lyssaviruses have circulated among Malagasy bats. The lyssavirus LBV has been isolated from the African straw-colored fruit bat (Eidolon helvum
), the second of the two species in this African genus in various countries of Africa [21
]. We isolated Ife virus and an alphaherpesvirus from the Malagasy straw-colored fruit bat [22
]. These two viral species have also been detected from African straw-colored fruit bat [22
]. Therefore, we highly suspected the presence of LBV in Madagascar. Consequently, postexposure rabies vaccination should be provided after an exposure to Malagasy bats. However, people should keep in mind that rabies vaccine is less efficient against lyssavirus belonging to the phylogroup 2, including LBV [24
We recently showed that a heminested PCR targeting a conserved region of the polymerase genes of lyssaviruses and applied to antemortem or postmortem skin biopsy (a specimen easier to collect than a piece of brain) was a successful procedure to perform rabies diagnostic [11
]. We raised centres for postexposure prophylaxis staffs awareness of the performance of this procedure. Since that period (2008), we received postmortem skin biopsies from rabies-suspected cases, some of them coming far from Antananarivo, like Taolagnaro, on the south coast of the country (data not shown). Rabies infection was confirmed in 5 of these 6 cases. These samples easy to perform and to ship to the laboratory should be more promoted among health care personnel through Madagascar, to have a better idea of the prevalence of rabies in humans. Furthermore, this procedure should be also tested on carnivorous mammals, considering the sampling of skin carrying vibrissae (rich in nerve endings surrounding the base of these hairs). This method could help avoiding contamination of people sampling these animals by rabies virus-containing biological fluids and promote the sampling of rabies-suspected animals.
So far, for economic reasons, there are rabies postexposure prophylaxis centres in only 26 of the 111 administrative districts of Madagascar. We received samples of rabies-suspected cases from only 13 of them, and rabies virus circulation was confirmed in all of them. There is a need to confirm repeatedly its circulation in all of these 26 districts, especially in two islands (Nosy Be and Sainte Marie), where there is no recent report of rabid animals. Sampling should be promoted in the 13 other districts to evaluate the pertinence of these centres.