Detection of Antibody and Antigen for Lassa Virus Nucleoprotein in Monkeys from Southern Nigeria

Lassa fever is a deadly viral haemorrhagic fever caused by Lassa Virus (LASV). Rodents, especially, Mystomys natalensis, are the known reservoirs of LASV and humans are the defined hosts. Monkeys share many illnesses with humans and experimental LASV infections in monkeys are fatal but natural LASV infection of monkeys has not been reported. Serum samples obtained between August 2015 and December 2017 from 62 monkeys belonging to six species in Southern Nigeria were tested for LASV as part of an ongoing surveillance of monkeys in the region for zoonotic pathogens. Commercially available Recombinant LASV (ReLASV) Pan-Lassa enzyme-linked immunosorbent assay (ELISA) test kits (Zalgen Labs, Germantown, MD, USA) were used to detect antibodies (IgG and IgM) and antigen specific for LASV nucleoprotein in the sera. Lassa-fever-specific IgG and IgM, and antigen specific for LASV nucleoprotein were detected in 5/62, 0/62, and 1/62 samples, respectively. The presence of LASV-specific antibodies in the sera suggests natural exposure to the virus, while the presence of LASV antigen may mean that monkeys are carriers of the virus. There is a need to broaden Lassa fever surveillance to include nonhuman primates (NHPs) for their probable role in the epidemiology of the disease. HIGHLIGHTS: • Rodents are the natural reservoirs of Lassa fever virus (LASV) and humans are the defined hosts. • Experimental LASV infections in non-human primates (NHP) are fatal but natural infection of NHP with the virus have not been reported. • We detected antigen and antibody specific for LASV in free-living Monkeys from southern Nigeria which implies that monkeys in the region are naturally exposed to LASV and are probable carriers of the virus.