Skip to main content
2023 ESA Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Contributed Talk

Session: : Disease And Epidemiology 1

COS 171-4 - CANCELLED - Land use gradients drive spatial variation in Lassa fever host communities in Eastern Sierra Leone.

Wednesday, August 9, 2023
10:45 AM – 11:00 AM PDT
Location: D138
Abstract: The natal multimammate mouse (Mastomys natalensis) is the primary reservoir species of the zoonotic infectious disease, Lassa fever (caused by the Lassa mammarenavirus). This disease is endemic to Sierra Leone with the highest incidence of human infection reported from the Eastern Province, although there is evidence of infection throughout the country. The spatial occurrence and abundance of the rodent host species of Lassa fever is regulated by the human environment and biotic interactions within small mammal communities, little is known about these effects even in highly endemic areas of Lassa fever.

We conducted a rodent trapping study at four village study sites between 2020-2023, comprising 40,152 trap nights to understand how M. natalensis is distributed across a gradient of landuse types and how this may be influenced by the broader small mammal community structure. We conducted a Bayesian multiple species occupancy model, accounting for imperfect detection, to test the hypothesis that M. natalensis were more likely to occur within human dominated landuse types.

We found that M. natalensis occurrence increased along an anthropogenic landuse gradient from less to more human dominated landscapes. We further found that this effect was not replicated across geographic scales. We found that the probability of occurrence in peri-urban settings was lower than in rural settings. Interactions within the small mammal community appeared to be driving this observation, moderating the probability of occurrence of M. natalensis. We propose that the presence of the invasive rodent species, Mus musculus, but not Rattus rattus reduces the probability of occurrence of M. natalensis. This finding may explain prior observations of lower-than-expected human cases of Lassa Fever fever from urban settings in endemic regions. Our study highlights that the spatially heterogeneous distribution of rodent species across landuse gradients can govern the risk to human populations from rodent borne zoonotic diseases and specifically for the risk of Lassa fever outbreaks.