No Longer Restricted to Travelers, Leishmaniasis Spreading in the United States

Jennifer Middleton, MD, MPH
Posted on November 6, 2023

In the United States, leishmaniasis is traditionally thought of as a disease contracted by travelers and military personnel stationed abroad. Endemic leishmaniasis has been reported in Texas since at least 2005, however, and the sand flies that can transmit leishmaniasis have been found as far north as Maryland and Delaware. Recent media reports of “flesh-eating parasites” and increasing rates of leishmaniasis in the United States may bring questions from patients and should also prompt us to further action. As the world’s climate continues to warm (as discussed by Dr. Lin in last week’s Community Blog post), family physicians must learn about and remain vigilant for diseases previously classified as “tropical,” including leishmaniasis.

More than 20 species of the protozoa Leishmania can infect humans via the bite of the female sand fly. Some Leishmania species cause systemic, visceral disease that is almost always fatal without treatment; the cases in Texas are the more common cutaneous form of leishmaniasis. The skin lesions typically present two to eight weeks after being bit by an infected sand fly:

The disease begins as an erythematous papule at the site of the sandfly bite on exposed parts of the body. The papule increases in size and becomes a nodule. It eventually ulcerates and crusts over. The border is usually raised and distinct. There may be multiple lesions, especially when the patient has encountered a nest of sandflies. The ulcer is typically large but painless unless there is secondary bacterial or fungal infection.

Diagnosis can be made in several ways, including cutaneous scraping and punch biopsy. Cutaneous leishmaniasis does not always need to be treated, but its skin lesions can result in scarring. First-line treatment is pentavalent antimony, which can be obtained from the Centers for Disease Control and Prevention (CDC) as well as some military hospitals for infected veterans and active-duty personnel.

Several measures have been evaluated to prevent leishmaniasis. Control of the disease-transmitting sand flies is challenging, though insecticides can help in heavily endemic areas. A vaccine against Leishmania is under development. Identifying and eliminating animal reservoirs, which can include rodents and dogs, can also help. And, advocating for policies and making personal decisions that help to limit climate change can, in the long term, limit the northern migration of sand fleas.

Family physicians can find more information about leishmaniasis at the CDC website, the WHO website, and in an AFP article on “Cutaneous Leishmaniasis: Recognition and Treatment.”