Investigation of rodent reservoirs of emerging pathogens in Côte d'Ivoire, West Africa

Background: One of the main health problems in West Africa remains upsurge of emerging pathogens. Ebola virus disease outbreak occurred in 2014 in Liberia, Guinea and Sierra Leone, Monkeypox virus in Nigeria in 2017 and most recently Lassa virus in Nigeria, Togo and Benin in 2018.  These pathogens have animal reservoirs as vectors for transmission. Proper investigation of the pathogens in their rodent vectors could help  reduce and manage their emergence and spread. Methodology: This study was conducted with an approval from the Côte d’Ivoire Bioethics Community. Small mammal trappings were carried out in  9 sites within three zones namely, peri-urban, peri-rural and protected areas. Liver, lung and kidney tissues from trapped small mammals were  sampled in accordance with the recommended conditions of biosafety and bioethics. The organs were transported in liquid nitrogen to the  laboratory. Molecular tests were used to detect pathogens. Orthopoxviruses and Monkeypox virus were detected in the organs by PCR using  consensus primers targeting the virus surface membrane haemagglutinin (HA) genes, while Leptospira species were detected by PCR using primers  targeting the rrs and lfb1 genes. Results: Out of 4930 night-traps, 256 (5.19%) small mammals were trapped including Crocidura, Rattus, Lophuromys, Praomys, Mus and Mastomys.  Leptospira species were detected in 6 genera from 7 study sites and the infected small mammals accounted for 13.3%. Leptospira sp was detected  mainly in the rodent vector genera Rattus (32.3%), Lophuromys (29.0%), and Praomys (16.1%). Three species of Leptospira were detected and  Leptospira interrogans was the most common frequent species (74.2%). Monkeypox virus was not detected from studied small mammals. Conclusion: The initial data from our investigation indicates the presence of Leptospira sp in rodent vectors, Rattus, Lophuromys and Praomys,  which are the potential small mammalian reservoirs of this pathogen in Cote d’Ivoire.