Lassa virus in the host rodent Mastomys natalensis within urban areas of N'Zerekore, Guinea

Abstract

Lassa virus is the causative agent of a dangerous zoonotic disease distributed in West Africa. A primary reservoir host of Lassa virus is Mastomys natalensis. These mice associate closely with humans and are commonly found in villages. Consequently, previous studies of Lassa virus have focused on rural areas. The prevalence of the virus in large cities has not been studied. We conducted a study in N'Zerekore city, which has a population of approximately 300,000 residents. Small mammals were captured during a pilot study in May, and the main study was performed in August 2018. Based on the pilot study, we designed and implemented a stratified random sample to investigate the prevalence of Lassa virus among M. natalensis in N'Zerekore. The total sampling efforts consisted of 45 and 985 trapping nights in May and August, respectively. Samples of rodent tissues were screened for Lassa virus by RT-PCR. In May, we trapped 20 rodents, including 19 M. natalensis. Viral RNA was detected in 18 M. natalensis. In August, 149 small mammals were captured, including 43 M. natalensis. The prevalence of Lassa virus among M. natalensis in N'Zerekore was 23.3% (CI 95%: 11.8-38.6%). Sequencing showed that the isolates belonged to lineage IV. We detected four Lassa virus hotspots located in different parts of the city. The largest Lassa virus hotspot was found in the neighborhood of the central market, which suggests that the virus was originally introduced into the city through the market.