Serological evidence of natural exposure to rabies in rural populations in Gabon

Abstract

Rabies is one of the oldest known zoonotic diseases, with dogs being the main reservoir for 99% of the cases of human rabies. However, wild animals may also be rabies vectors. In most cases, contact with a rabid animal results in rabies without pre- or post-exposure prophylaxis, and the disease is nearly always fatal. Nevertheless, a few studies have documented cases of rabies-specific antibodies detection in people with no history of vaccination, suggesting that individuals can be in contact with the virus without developing fatal rabies. To further investigate this possibility of non-lethal human rabies exposure, we carried out a retrospective serological analysis, using both immunoassays (ELISA) and seroneutralization assays (RFFIT), on 430 sera collected between 2005 and 2008 from rural unvaccinated Gabonese populations in the Estuaire and Ogooué-Ivindo provinces. Eleven (11) samples (2.5%) were positive for rabies-specific antibodies using both techniques: 1 in Estuaire and 10 in Ogooué-Ivindo. One of three positive people from the Ogooué-Ivindo province, resampled in early 2023, was still positive for rabies-specific antibodies, suggesting that some degree of immunity can be maintained over many years. Our results also show a marginally significant higher prevalence among hunters. This study demonstrates that rabies circulates actively in Gabon and some unvaccinated individuals living in rural environments can be exposed to the virus and survive, with the development of a significant and specific humoral response that can persist for more than 15 years. This passive seroprevalence survey underlines the need to establish a national surveillance system of rabies in both humans and animals in urban and rural areas, and to enhance access to pre- and post-exposure prophylaxis.