Centers for Disease Control and Prevention have identified dozens of cases of leishmaniasis, all without a history of travel outside the United States, over a 14-year period. A female sand fly (Phlebotomine) biting a human hand, July 8, 2009. Ray Wilson / Alamy

October 21, 2023, 2:47 PM By Aria Bendix According to the Centers for Disease Control and Prevention (CDC), a parasite capable of causing disfiguring skin disease may be endemic in Texas and present in other southern states.

From 2005 to 2019, the CDC identified 1,222 cases of leishmaniasis in the United States, a disease transmitted through the bites of infected female sand flies. The parasite can cause a condition called leishmaniasis, which typically results in the development of skin ulcers that appear several weeks or months after being bitten.

Cases of leishmaniasis in the United States are usually found in people who have traveled outside the country to tropical or subtropical climates, especially in the Middle East, Central Asia, North Africa, and Latin America.

However, the CDC has reported that 86 Leishmania samples were obtained from individuals who had not recently traveled outside the United States.

Researchers also discovered a unique strain of Leishmania that appears to be genetically distinct from travel-related cases, suggesting that it has been locally transmitted within the United States.

"We can't say it's exclusive to Texas, but from the samples sent to the CDC, most were from Texas," said Vitaliano Cama, a senior advisor in the CDC's Parasitic Diseases and Malaria Branch who conducted the study.

CDC researchers presented the data this week at the annual meeting of the American Society of Tropical Medicine and Hygiene in Chicago.

Dr. Mary Kamb, an epidemiologist at the CDC who also participated in the study, stated that the results primarily concern healthcare workers and do not imply a significant risk to the general population.

"We need to raise awareness among doctors, dermatologists, infectious disease doctors, and general practitioners," she said.

According to Kamb, in addition to cases in Texas, the CDC has received isolated reports of local leishmaniasis in Florida, although these cases have not yet been confirmed. Isolated cases have also been identified in Oklahoma and Arizona.

"Our understanding of leishmaniasis acquired in the U.S. is still evolving," said Joshua Lieberman, deputy director of the Clinical Laboratory for Molecular Microbiology at UW Medicine, who was not involved in the study. "I'm not clear whether the true level of new infections is increasing, or we're just getting better at detecting them, or both."

Lieberman noted that leishmaniasis remains rare in the United States.

"For the general public, if you're not traveling to endemic areas, your risk is vanishingly small," Lieberman said.

However, both Lieberman and Kamb emphasized that some cases may go unnoticed without proper surveillance.

Kamb stated that sand flies are found in several southern states, and in many parts of the United States, warm temperatures and wooded areas can support insect populations.

But Texas is the only state that requires healthcare workers to report cases of leishmaniasis to the health department, and there is no national requirement to report the disease to the CDC.

"It would be useful for states outside Texas to consider the possibility of reporting leishmaniasis, but we don't have much data from other states to suggest that this is a problem," Kamb said.

How to Recognize and Treat Leishmaniasis Lieberman stated that nearly all cases of local leishmaniasis in the United States belong to a species called Leishmania mexicana, which causes skin lesions that often begin as small, painless bumps and can develop into ulcers.

According to Lieberman, the lesions often resolve on their own and may not require treatment, although doctors can prescribe local therapy if needed.

The most common form of leishmaniasis causes skin ulcers from the bites of Phlebotomine sand flies. The most common form of leishmaniasis causes skin ulcers from the bites of Phlebotomine sand flies. Mohammed Abdullah / Anadolu Agency via Getty Images The strain identified in the CDC presentation this week is a variety of Leishmania mexicana, which means that cases of the disease should be relatively mild.

According to the World Health Organization, another parasite, Leishmania infantum, can cause a more severe form of leishmaniasis that affects internal organs and results in 20,000 to 30,000 deaths annually worldwide.

Mosquitoes acquire the parasite by feeding on infected dogs, so researchers are concerned about the spread of Leishmania infantum in the United States through imported dogs from other countries.