Lassa fever

Lassa fever is a deadly hemorrhagic disease, killing several thousand people in West Africa every year. It is also among the foremost causes of deafness and is responsible for 20% maternal mortality and 90% fetal loss during pregnancies.The rodent Mastomys natalensis has been implicated as the natural reservoir of the Lassa virus.This project seeks, employing mainly molecular methods, to assess the risk of rodent-to-human transmission by determining prevalence of the Lassa virus in rodent populations across various spatial and temporal scales within Nigeria.

Beginning from January 2011, 857 small mammals have been sampled from localities spanning various ecological zones and habitats across Nigeria. L- and S-gene RT-PCR screening of these small mammals is in progress.

Mastomys natalensis from the Edo state area have already tested positive with a prevalence as high as 38% in Eguare-Egoro village during the dry season of 2011.In Ekpoma city, also within Edo state, in collaboration with public health personnel from the Irrua State Teaching Hospital, a comparison of rodent occurrence between case and non-case houses is being carried out (casehouses being where a confirmed case of Lassa fever has occurred). RT-PCR testing of Mastomys natalensis captured during the dry season of 2012 in this urban area revealed 8.3% positive, coming from a case house. Results obtained so far from this project already set the stage for the next phase of investigations, which involve the molecular epidemiology of primary transmission in Edo state, guided by hospital-documented cases of Lassa fever. This will enable direct comparison of genetic virus sequences obtained from humans to those from rodents which will, among various things, help trace the origin of rodent-to-human infection and patterns of virus spread during Lassa epidemics.