Outbreaks of human bubonic plague still occur regularly in Madagascar, with fleas carrying the plague bacterium Yersinia pestis being the main vectors of the disease. While the rat flea is commonly known to spread the plague, a study conducted by medical entomologist Adelaide Miarinjara found that the human flea may also play a secondary role in these outbreaks. Through her investigations, Miarinjara discovered that households with traditional dirt floors covered by plant-fiber mats were more likely to have a higher abundance of human fleas, compared to households with cement or board floors. Keeping animals in the house at night was identified as a secondary risk factor for flea infestations.
The research team’s findings, published in PLoS Neglected Diseases, highlighted the importance of addressing housing conditions in plague-endemic areas of Madagascar to reduce flea infestations. Upgrading flooring in homes and constructing separate sheds for animals at night could help mitigate the risk of flea infestations and improve overall quality of life for residents. Flea infestations not only pose health risks due to the potential spread of diseases but also lead to the overuse of insecticides in households. Improper application of insecticides can result in overexposure to harmful chemicals and contribute to the development of insecticide resistance among fleas.
The study emphasized the need to address poverty-related challenges in housing construction in plague-endemic areas. Resurfacing dirt floors with concrete could have multiple health and quality-of-life benefits, including reducing flea populations, making floors easier to clean of contaminants, and improving overall living conditions. Additionally, the research team, led by Thomas Gillespie, adopts a “one health” approach to epidemics, examining interactions among people, domestic animals, wildlife, and ecosystems to understand the transmission of diseases like the plague.
In Madagascar, plague outbreaks typically originate in rural regions during the rainy season and are associated with agricultural practices, deforestation, and flea infestations. While the rat flea is the primary vector for spreading the plague, the study conducted by Miarinjara’s team focused on the presence of human fleas in households in four different villages. Despite the lower transmission efficiency of the human flea compared to the rat flea, the study found a high prevalence of human fleas in households, along with some rat fleas and fleas from a third species that feeds on cats and dogs.
Ongoing research is exploring the drivers of insecticide resistance among fleas and ways to promote safe and effective insecticide use in households. The study’s co-authors include researchers from various institutions in Madagascar and the United States, with funding provided by the Branco Weiss Society in Science Fellowship and the American Society of Tropical Medicine and Hygiene. By addressing housing conditions, promoting safe insecticide use, and understanding flea dynamics in plague-endemic areas, researchers aim to improve public health outcomes and reduce the impact of flea-borne diseases like bubonic plague in Madagascar.
