Rodent control to fight Lassa fever: Evaluation and lessons learned from a 4-year study in Upper Guinea

Abstract

Lassa fever is a viral haemorrhagic fever caused by an arenavirus. The disease is endemic in West African countries, including Guinea. The rodents Mastomys natalensis and Mastomys erythroleucus have been identified as Lassa virus reservoirs in Guinea. In the absence of a vaccine, rodent control and human behavioural changes are the only options to prevent Lassa fever in highly endemic areas. We performed a 4 year intervention based on chemical rodent control, utilizing anticoagulant rodenticides in 3 villages and evaluating the rodent abundance before and after treatment. Three additional villages were investigated as controls. Analyses to assess the effectiveness of the intervention, bait consumption and rodent dynamics were performed. Anthropological investigations accompanied the intervention to integrate local understandings of human–rodent cohabitation and rodent control intervention. Patterns of bait consumption showed a peak at days 5–7 and no consumption at days 28–30. There was no difference between Bromadiolone and Difenacoum bait consumption. The main rodent species found in the houses was M. natalensis. The abundance of M. natalensis, as measured by the trapping success, varied between 3.6 and 16.7% before treatment and decreased significantly to 1–2% after treatment. Individuals in treated villages welcomed the intervention and trapping because mice are generally regarded as a nuisance. Immediate benefits from controlling rodents included protection of food and belongings. Before the intervention, local awareness of Lassa fever was non-existent. Despite their appreciation for the intervention, local individuals noted its limits and the need for complementary actions. Our results demonstrate that chemical treatment provides an effective tool to control local rodent populations and can serve as part of an effective, holistic approach combining rodent trapping, use of local rodenticides, environmental hygiene, house repairs and rodent-proof storage. These actions should be developed in collaboration with local stakeholders and communities.

Efficacy of Management and Monitoring Methods to Prevent Post-Harvest Losses Caused by Rodents

“…With respect to rodent management methods we found that the main rodent pests in village households were Rattus rattus, followed by Mus musculus, and Bandicota bengalensis. This is in line with findings from Bangladesh [46], India [47], Pakistan [48], and Myanmar [9,18], where R. rattus and B. bengalensis were also found to be the main rodent pests. During the dry season, fewer rodents were trapped (n = 89) than during the wet season (n = 121), which agrees with what is known about these rodent species' breeding and population dynamics [34].…”

Systematics, Ecology, and Host Switching: Attributes Affecting Emergence of the Lassa Virus in Rodents across Western Africa

“…Hence, how possible is it to significantly reduce levels of rodent infestation inside and around human houses? Recently, the authors of a four-year study in Guinea observed that for rodent control using chemical bait to be effective in the long term, it has to be combined with general environmental hygiene, coordinated across whole villages instead of select addresses, continuous through time (as Mastomys populations can recover within a few months), and enhanced by a higher quality of domestic amenities (e.g., rodent-proof walls, roofs, and food storage) [23].…”

Biodefense Implications of New-World Hantaviruses

“…By culling or isolating rodents through said techniques, rodent controls help to minimize human-rodent contact and ultimately transmission. This is exemplified by other rodent-borne Bunyaviruses such as the Arenavirus Lassa Virus which experienced a reduction in seroprevalence proportional to reductions in its North-West African reservoirs (Mastomys natalensis, Mastomys erythroleucus, Hylomyscus pamfi) through the use of rodenticides and urban proofing that targeted rodent and human food stocks and housing (Mari Saez et al, 2018). However, complete seroprevalence reduction of Lassa Virus relied upon an 80% reduction in rodent population densities indoors and in peridomestic environments to avoid lateral viral transmission which becomes labor and resource intensive and may not be feasible in developing countries or those affected by war (Mariën et al, 2019).…”