Systematics, Ecology, and Host Switching: Attributes Affecting Emergence of the Lassa Virus in Rodents across Western Africa

Abstract

Ever since it was established that rodents serve as reservoirs of the zoonotic Lassa virus (LASV), scientists have sought to answer the questions: which populations of rodents carry the virus? How do fluctuations in LASV prevalence and rodent abundance influence Lassa fever outbreaks in humans? What does it take for the virus to adopt additional rodent hosts, proliferating what already are devastating cycles of rodent-to-human transmission? In this review, we examine key aspects of research involving the biology of rodents that affect their role as LASV reservoirs, including phylogeography, demography, virus evolution, and host switching. We discuss how this knowledge can help control Lassa fever and suggest further areas for investigation.

An exploration of the protective effect of rodent species richness on the geographical expansion of Lassa fever in West Africa

“…Fifth, a recent LF risk map from Mylne et al [55] suggested that presence of LF is possible in Senegal and Niger where we excluded in the models. Inclusion of those countries in the model could change our results, although a recent review study [56] did not find the evidences of LF presence in those countries. Sixth, we considered M. natalensis as a major reservoir in this study, but other possible reservoirs such as Rattus rattus and Mus musculus can be included in the follow-up studies [57].…”

Bridging the gap: Using reservoir ecology and human serosurveys to estimate Lassa virus spillover in West Africa

“…Geographic variation in LASV and its primary reservoir may also be responsible for the modest fit of our model. For instance, across West Africa LASV consists of several clades [ 22 ]. If certain clades are better at infecting humans, then our model will tend to underestimate the rate of human infections in regions where such highly-infectious clades occur.…”

“…Though M. natalensis is widely distributed across all of Africa, the species consists of multiple clades that likely differ in their ability to serve as hosts to LASV [ 20 , 21 ]. By limiting the spatial extent of the study region to West Africa we focus on the region occupied by the A-I clade of M. natalensis that is believed to transmit LASV [ 22 ]. Our M. natalensis capture data, as well as all of the LASV survey data, originate from within this region, thus providing a discrete bound on the area of Africa in which the learned relationships of the model apply.…”

Linking Zoonosis Emergence to Farmland Invasion by Fluctuating Herbivores: Common Vole Populations and Tularemia Outbreaks in NW Spain

“…Some rodent species with irruptive population dynamics (i.e., multi-annual "boombust" fluctuations in abundance) can be involved in the disease amplification, spillover and transmission to humans (16,18). The role of native rodent hosts with highly fluctuating population has been critical in the emergence of many zoonoses worldwide, such as hantaviruses (19,20), Lassa virus (21,22), Andes virus (23), Lyme disease and tick-borne encephalitis (24). The challenge goes beyond the identification of a new rodent host but lies in understanding when changes in rodent communities resulting from invasions or range shift can lead to the emergence of novel pathogens in ecosystems, as in the case of Yersinia pestis and invasive Rattus sp.…”