Leishmaniasis is a group of diseases caused by a protozoan parasite from the genus Leishmania. This parasitic infection is transmitted to humans through the bite of an infected female phlebotomine sandfly. The sandfly acts as the vector, picking up the parasite from an infected host and passing it to the next host during a blood meal. Since there is no widely available human vaccine, prevention relies on breaking this transmission cycle. This involves targeting the vector, minimizing human exposure, and controlling the sources of infection.
Actions to Protect Yourself from Sandfly Bites
Protecting exposed skin is the most direct way to prevent sandfly bites and subsequent infection. Insect repellents approved by the Environmental Protection Agency (EPA) are effective tools for personal protection. Repellents containing DEET (N,N-diethyl-meta-toluamide) are effective, with concentrations between 10% and 35% providing adequate protection. Picaridin is another strong option comparable in efficacy to DEET, and it is odorless and does not damage plastics or synthetic fabrics.
When spending time in endemic areas, wearing protective clothing is important. Opting for long-sleeved shirts, long pants, and socks minimizes exposed skin. Tucking shirts into pants and pant cuffs into socks or boots creates a physical barrier that prevents the small insects from crawling beneath the fabric. Applying the insecticide permethrin directly to clothing, but never to skin, provides an additional layer of chemical defense that can last through several washings.
Behavioral adjustments are also an effective form of prevention. Sandflies are generally most active from dusk until dawn, meaning outdoor activity during these hours should be minimized whenever possible. For sleeping, using an insecticide-treated bed net (ITN) is recommended, especially in unscreened or non-air-conditioned dwellings. Since sandflies are much smaller than mosquitoes, nets must have a fine mesh to be protective.
Reducing Sandfly Habitats Around the Home
Controlling the sandfly population around the home involves both physical and chemical interventions. Environmental management aims to reduce the places where sandflies rest and breed, such as debris, leaf litter, and animal waste. Simple actions like clearing vegetation, removing trash, and cleaning up animal shelters near residences disrupt the sandflies’ preferred microhabitats.
Sandflies often utilize cracks, crevices, and rodent burrows as resting and breeding sites. Sealing cracks in walls, floors, and foundations of homes helps prevent their entry and reduces indoor resting sites. In high-risk areas, authorized vector control programs may employ indoor residual spraying (IRS). This involves applying a long-lasting insecticide to the interior walls, creating a chemical barrier that kills adult sandflies resting on the treated surfaces.
Newer methods, such as Attractive Toxic Sugar Baits (ATSBs), are also being explored for sandfly control in some areas. This technique uses a sugary bait mixed with a low-dose insecticide to attract and kill sandflies that feed on it. The successful implementation of these environmental and chemical controls requires a community-wide effort to reduce the overall density of the insect vector.
Controlling Infection Sources (Reservoirs)
Controlling the source of the parasite, known as the reservoir, is a key component of leishmaniasis prevention. For zoonotic forms maintained in animals, the domestic dog is the primary reservoir for Leishmania infantum, which causes visceral leishmaniasis. Control measures targeting dogs include using insecticide-impregnated collars, often containing deltamethrin, which provides a high level of protection against sandfly bites.
Screening and treating infected dogs is another strategy, although treating canine leishmaniasis is not always curative and can be difficult. In some areas, culling infected dogs has been implemented, but this approach remains controversial and its effectiveness at a community level is often debated. Effective control requires a coordinated effort, especially in regions where the disease is maintained in both domestic and wild animal populations.
Humans can also serve as the reservoir for some forms of leishmaniasis, particularly the anthroponotic types. Prompt diagnosis and effective treatment of infected individuals reduces the pool of infection. People who develop post-kala-azar dermal leishmaniasis (PKDL) after treatment for the visceral form may have skin lesions containing the parasite, making them a potential source of infection. Therefore, early case detection and management are necessary to prevent further transmission.