title: Fluctuation of abundance and Lassa virus prevalence in Mastomys natalensis in Guinea, West Africa.
abstract: Based on empiric surveillance data, the incidence of human Lassa fever (LF) cases in Guinea and other West African countries has been reported to increase during the dry season compared to the rainy season. To investigate possible links with the ecology of the rodent reservoir of the virus, we conducted a 2-year longitudinal survey of Mastomys natalensis in a region of high human Lassa virus (LASV) seropositivity in Guinea. Standardized rodent trapping with similar trapping efforts between seasons was performed in three villages and 53.5% (601/1123) of the animals were identified as M. natalensis using morphometric and molecular criteria. Mean trapping success (TS) of M. natalensis was always higher inside houses than in proximal cultivations. In the dry season, mean TS increased 2-fold inside houses and decreased up to 10-fold outside (p < 0.0001), suggesting aggregation of rodents inside houses due to restricted food supply. 14.5% (80/553) of M. natalensis were tested positive for Lassa virus by reverse transcription-polymerase chain reaction (RT-PCR; range, 5%-30%) and prevalence of the virus was two to three times higher in rodents captured in the rainy season than in the dry season (p < 0.05). Inside houses, however, the LASV prevalence fluctuated nonsignificantly with season. These data suggest that in Guinea the risk of LASV transmission from rodents to humans is present both in the rainy and the dry season, reflected by the occurrence of LF cases throughout the year. In the dry season, however, the increased risk of humans encountering Mastomys and their excreta inside of houses may result in an increase of human Lassa fever cases.
authors.affiliation: Department of Systematics and Evolution, Museum National d'Histoire Naturelle, Paris, France. ecalvet@club-internet.fr
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Fichet-Calvet
authors.forename: Emilie
authors.initials: E
authors.lastname: Lecompte
authors.forename: Lamine
authors.initials: L
authors.lastname: Koivogui
authors.forename: Barré
authors.initials: B
authors.lastname: Soropogui
authors.forename: Amadou
authors.initials: A
authors.lastname: Doré
authors.forename: Fodé
authors.initials: F
authors.lastname: Kourouma
authors.forename: Oumar
authors.initials: O
authors.lastname: Sylla
authors.forename: Stéphane
authors.initials: S
authors.lastname: Daffis
authors.forename: Kékoura
authors.initials: K
authors.lastname: Koulémou
authors.forename: Jan
authors.initials: J
authors.lastname: Ter Meulen
mesh_terms: D000818:Animals; D004197:Disease Reservoirs / Q000662:veterinary / Q000821:virology; D016701:Guinea / Q000453:epidemiology; D006801:Humans; D007835:Lassa Fever / Q000453:epidemiology / Q000635:transmission* / Q000662:veterinary*; D007836:Lassa virus / Q000302:isolation & purification*; D051189:Murinae / Q000821:virology*; D015995:Prevalence; D011891:Rain; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012376:Rodent Diseases / Q000453:epidemiology / Q000635:transmission*; D012621:Seasons; D015047:Zoonoses