One Health surveillance of Lassa fever in Oyo State, Nigeri

Information from the abstract

Introduction: Lassa fever (LF) is a severe viral haemorrhagic disease caused by Lassa virus (LASV) and remains endemic in Nigeria, where it is associated with recurrent outbreaks, substantial morbidity, and high mortality. The persistence of LF is driven by weak surveillance systems, limited diagnostic capacity, poor health-seeking behaviour, and complex interactions at the human–rodent–environment interface. In endemic settings, these factors contribute to under-detection of cases and sustained transmission. This study adopted a One Health-informed approach to assess the sero-molecular prevalence of LASV in humans, evaluate viral detection in rodents recovered following bait-based deratization activities and examine the influence of meteorological factors on LF occurrence in Oyo State, Nigeria. Methods: Between January 2022 and April 2023, a cross-sectional study was conducted across selected high-risk LGAs in Oyo State. Blood samples (n = 289) were collected from febrile patients and screened for LASV using RT-qPCR and IgM/IgG ELISA. Rodents (n=30) were recovered in Iwajowa LGA, they were morphologically identified and tested for LASV using RT-qPCR. Meteorological data were obtained from the Nigerian Meteorological Agency to evaluate associations between climatic variables and LF occurrence. Data were analysed using descriptive statistics and bivariate correlation analysis. Results: The overall LASV seroprevalence was 11.1% (32/289), comprising IgM positivity in 9.7%, IgG positivity in 4.8%, and dual IgM/IgG positivity in 3.5% of participants; three samples (1.0%) were confirmed positive by RT-qPCR. All recovered rodents tested negative for LASV RNA. Notably, no Mastomys species were recovered, while Rattus rattus, Mus musculus, and Cricetomys gambianus predominated. Correlation analysis showed a significant positive association between LF occurrence and temperature (r = 0.69, p < 0.05), and significant negative associations with rainfall (r = –0.63, p < 0.05) and humidity (r = –0.78, p < 0.05). Conclusion: This study provides evidence of recent LASV exposure and limited molecular confirmation of active infection among suspected Lassa fever cases in Oyo State and underscores the importance of a One Health framework in understanding disease dynamics across human, animal, and environmental interfaces. The findings highlight the need to strengthen diagnostic capacity, improve surveillance and rodent control strategies, and integrate meteorological data into predictive early warning systems to enhance outbreak preparedness in endemic settings.

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Related topics: Viral Infections and Outbreaks Research · Vaccine Coverage and Hesitancy · Zoonotic diseases and public health