Abstract
The multimammate mouse (Mastomys natalensis) is the reservoir for Lassa virus (LASV). Zoonotic transmission occurs when humans are directly or indirectly exposed to fluids of the multimammate mouse, such as urine, saliva, and blood. Housing characteristics and domestic organization affect rodent density in and around households and villages, and are likely to be a risk factor for Lassa fever in humans where the reservoir exists. We use semi-structured interviews (N = 51), a quantitative survey (N = 429), direct observations, and a rodent ecology study to provide new insights into how the organization of domestic spaces brings together humans and rodents and creates pathways for infection in rural settlements in Bo District, Sierra Leone. Rodents were frequently reported inside houses (92.4% of respondents), in which we predominantly trapped M. natalensis (57% of trapped rodents) and Rattus rattus (38% of trapped rodents). Building design and materials provide hiding and nesting places for rodents and lead to close proximity with humans. Patterns of contact are both unintentional and intentional and research participants reported high levels of contact with rodents (34.2% of respondents) and rodent fluids (52.8% of respondents). Rodents are also perceived as a serious threat to food security. These results present detailed knowledge about how humans live with and come into contact with rodents, including the LASV reservoir. Our results argue for further collaborative research in housing and environmental modification such as ceiling construction, food storage, and sanitation as prevention against zoonotic LASV transmission.
Highlights
Lassa fever (LF) is a viral zoonotic illness and a significant cause of morbidity and mortality in countries across West Africa, namely Benin, Guinea, Liberia, Nigeria, and Sierra Leone.[1,2,3] LF is estimated to affect between 250 and 300,000 people and cause between 5,000 and 10,000 fatalities annually across the region,[3] but many cases are likely to go unreported due to a lack of diagnostic facilities.The main reservoir for Lassa virus (LASV) is the multimammate mouse, Mastomys natalensis
Urine may present a particular risk for human infections as M. natalensis can shed LASV in urine at any age[7] and LASV has been shown to be aerosolized under laboratory conditions.[8]
We place our observations into perspective by presenting results from our rodent ecology survey
Summary
Lassa fever (LF) is a viral zoonotic illness and a significant cause of morbidity and mortality in countries across West Africa, namely Benin, Guinea, Liberia, Nigeria, and Sierra Leone.[1,2,3] LF is estimated to affect between 250 and 300,000 people and cause between 5,000 and 10,000 fatalities annually across the region,[3] but many cases are likely to go unreported due to a lack of diagnostic facilities. The main reservoir for Lassa virus (LASV) is the multimammate mouse, Mastomys natalensis. Other rodent reservoirs (Mastomys erythroleucus and Hylomyscus pamfi) have been recently identified[4] but their relative contribution to human infections is unknown. Risk factors for primary (zoonotic) transmission are unclear and possibly linked to housing[10] and hunting and consumption of rodents.[11,12,13]
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