a larger role than previously thought. Researchers in Madagascar wanted to understand why some homes in rural areas are infested with fleas, which can increase the risk of plague transmission. By studying the behavior and feeding patterns of both rat fleas and human fleas, they found that the human flea is more common in these homes and may be contributing to the spread of the disease.
The researchers recommend implementing insecticide-based flea control measures in homes and communities to reduce the flea populations and ultimately decrease the risk of plague transmission. By targeting both rat fleas and human fleas, they hope to prevent future outbreaks of bubonic plague in rural Madagascar.
In her role as a medical entomologist, Adelaide Miarinjara played a part in investigating plague outbreaks in rural Madagascar. She discovered that many households were infested with human fleas. Miarinjara, who is originally from the island nation off the east coast of Africa, is currently working as a postdoctoral fellow at Emory University and collaborating with the Pasteur Institute in Madagascar.
She noticed a significant difference in the number of fleas in different households within the same village. “We have observed huge variability in the number of fleas in different households in the same village,” she says. “We might collect three or five fleas in one house and hundreds of them in another house.”
To solve the mystery of this variability, Miarinjara led a study.
PLoS Neglected Diseases published a study conducted by Miarinjara’s team, which found that human fleas are more abundant in households with traditional dirt floors covered by a plant-fiber mat compared to those with cement or board floors. Another contributing factor to the flea infestation was the practice of keeping animals in the house at night.
“Flea larvae require a specific level of humidity to survive, and the dirt covered by the plant-fiber mat may provide the ideal moisture for their thriving,” Miarinjara explained.
Miarinjara hopes that organizations aiming to improve living conditions in plague-endemic areas of Madagascar will prioritize the upgrade of household flooring to mitigate the risk of flea infestations.
g The issue of flea infestation in homes is a serious one, which can increase the risk of contracting diseases and significantly impact the quality of life. According to Miarinjara, the constant biting can be extremely irritating and can lead to sleep deprivation. In an effort to combat the problem, 80% of households are resorting to the overuse of insecticides. Unfortunately, many people are purchasing liquid insecticides that are being repackaged in unlabeled containers, without any instructions for proper application. In addition to this, households are also taking measures such as replacing flooring and constructing separate sheds for animals in an attempt to minimize the infestation.
These products are typically found and purchased at small, outdoor markets.
Incorrect usage of pesticides poses a health hazard to individuals who could potentially be exposed to an excessive amount of these chemicals. According to Miarinjara, “Excessive use of these chemicals can also be perilous as certain fleas are becoming resistant to insecticides, which are the primary tools for dealing with outbreaks of plague.” “The research has identified that poverty related to housing construction is a major challenge,” says Thomas Gillespie, senior author of the study and professor and chair of Emory’s Department of Environmental Sciences. “Replacing dirt floors in homes with concrete could address a variety of health and quality-of-life concerns.Yes, this includes using the environment in novel ways to control pests – for example, by releasing sterilized male insects, or by mixing fungal spores with flea blood to kill them. Additionally, their research has shown that maintaining a clean living environment can have a big impact on reducing flea populations in homes and making floors easier to clean of contaminants like fecal matter brought in from the outside.”
The Gillespie lab is a leader in the “one health” approach to epidemics, which involves studying how people, domestic animals, wildlife, and ecosystems interact to understand how diseases spread between species.
The plague has been a problem for humans for thousands of years and has continued to persist over time. Fortunately, the discovery and use of antibiotics has made it possible to effectively treat the plague, turning it into a thing of the past for much of the world.
< rnthe rat flea, or Xenopsylla cheopis, can transmit enough bacteria to infect someone with plague, unlike other flea species that have evolved to prefer the blood of one animal over another but may feed on a variety of organisms if they are hungry enough. In Madagascar, plague returns regularly to claim new victims, with cases typically originating in the rural rice-growing region of the central Highlands during the rainy season. Outbreaks there are associated with agriculture, deforestation, the black rat, and fleas.The human flea, Pulex irritans, is capable of transmitting bacteria, making it a less effective carrier of plague but still a concern. In this study, researchers gathered fleas from 126 households in four different villages in rural Madagascar. These homes typically have multiple levels, with the bottom level often used to house livestock and the upper levels used for sleeping, cooking, and eating. Fleas were collected overnight on the second floor of the homes using simple traps – a lit candle set in a dish of soapy water, as the fleas are attracted to the flickering light.
When fleas jump into the dish, they often drown.
The researchers carefully removed each drowned flea with tweezers, allowed them to dry on absorbent paper, and then placed them in test tubes for further identification and analysis in the laboratory.
The findings indicated that approximately 95% of the species found in homes were human fleas, occasionally mixed with a small number of rat fleas and some from a third species that prefers to feed on cats and dogs. Similar results were obtained from collections conducted in both the dry and rainy seasons.
“We are now delving deeper into the use of insecticides in homes,” Miarinjara explains. “We want to investigate the impact of insecticide use on the flea populations.”The researchers are focused on understanding the reasons behind insecticide resistance in fleas and are working on ways to assist people in using insecticides more safely and effectively. The study’s co-authors include Annick Reveloson, a PhD student at the University of Antananarivo in Madagascar; Stephen Mugel, a current Emory PhD student who will graduate in May; Nick An, a recent graduate from Emory’s BS/MPH program; Andry Andriamiadanarivo, a technician at Centre ValBio in Madagascar; and Minoarisoa Rajerison, Rindra Randremanana, and Romain Girod, research scientists at the Pasteur Institute in Madagascar. The research received funding from the Branco Weiss Society in Sci.The study was supported by the National Science Foundation, the National Institutes of Health Fogarty International Center, the John E. Fogarty International Center, the Burroughs Wellcome Fund, the RAPIDD program of the Science & Technology Directorate, and the Defense Threat Reduction Agency.
