Leishmaniasis: No Longer Just a Tropical Disease—Now Endemic in the US

For the month of February 2024, Infection Control Today® and ContagionLive® are collaborating on rare infectious diseases for Rare Disease Awareness Month, examining both old and new infectious diseases that health care workers need to know.

Leishmaniasis is a potentially fatal disease caused by a protozoa parasite from over 20 Leishmania species transmitted through the bite of infected sandflies. It presents in 3 main forms: cutaneous, mucocutaneous, and visceral. The symptoms of Leishmaniasis vary from skin lesions to systemic involvement and death.

The disease is endemic in tropical and subtropical regions and affects millions of people worldwide, particularly those in impoverished areas with limited access to health care. However, as Infection Control Today® (ICT®) learned during a conversation with Henry G. Spratt, Jr, MD, it also has been determined to be endemic in the US as well.

Spratt is the senior microbiologist and professor in the Department of Biology, Geology, and Environmental Science at the University of Tennessee at Chattanooga; and a member of ICT’s Editorial Advisory Board.

"Leishmaniasis is caused by a protozoa parasite from over 20 Leishmania species. Over 90 sandfly species are known to transmit Leishmania parasites,” according to WHO. Sand flies that can or may transmit leishmaniasis have been found in 17 states as of 2021. Also, in November 2023, NPR reported on how leishmaniasis is endemic to the US as far north as Ohio, and has been here since at least 2005.

In a 2018 published study, the authors wrote, “Human cutaneous leishmaniasis is endemic in the United States, and, at least regionally, is acquired endemically more frequently than it is via travel. Our data argue in favor of making leishmaniasis a federally reportable disease and may have substantial implications on North American public health initiatives, with climate models predicting the number of citizens exposed to leishmaniasis will double by 2080.”

During Spratt’s discussion with ICT, he said, “Leishmaniasis has been around a long time; it's not like this is a new disease or anything; it tends to be, as noted, mostly in the past as a tropical disease, mainly because the vector, which is a phlebotomine fly, these are little sandflies. They are typically found in warmer climates. And so, there are numerous species of Leishmania that will cause leishmaniasis."

Some of these species are endemic to Southeastern Asia, others in Africa, and in South America. "And then recently, there has been a disturbing discovery that apparently, there is a strain of species Leishmania Mexicana, that is endemic in Texas and part of the panhandle of Oklahoma," Spratt said.

As he explained, climate change is causing some changes in where these sandflies can be found. “There are other socio-economic factors that come into play…particularly in other countries where you get people more crammed into areas where the density of human population used to be lower, but then they'll have animals around them who serve as the reservoirs….In the US, with the strong public health systems that we have, we're seeing this at the beginning of what appears to be a change, that it's shifting from the tropics.”

Spratt advises that if there is “a little fly flying around [you],…. If you start showing any other of the symptoms, life if you run a fever or feel very ill and lethargic, talk to your doctor.”