Tropical Parasite May Be Endemic in Texas

A parasitic disease that can cause skin ulcers and is usually spread by the tiny sandfly may now be endemic to the U.S., preliminary findings from CDC researchers suggested.

Genetic sequencing of 2,235 U.S. cutaneous leishmaniasis samples submitted from 2005 to 2019 confirmed the presence of a potentially distinct genotype of the Leishmania mexicana species in non-travelers. The genotype, CCC on the ITS2 locus, was found in 50 cutaneous leishmaniasis samples, and 47 of these were from Texas.

“These findings offer evidence that leishmaniasis may be endemic in the United States and that LMx genotype CCC may be an autochthonous genotype,” Marcos de Almeida, PhD, formerly of the CDC, noted in a study presented at last week’s American Society of Tropical Medicine and Hygiene (ASTMH) annual meeting.

“We found that there were several cases in people who had not traveled outside the United States, which was surprising and allowed for some additional analysis on the molecular characteristics,” study co-authors Mary Kamb, MD, MPH, and Vitaliano Cama, DVM, of the CDC, wrote to MedPage Today in an email.

Notably, the agency could not confirm “with certainty” the spread of leishmaniasis via local sandfly populations.

Cases of cutaneous leishmaniasis, a disease most common to the Americas, the Mediterranean basin, the Middle East, and central Asia, have cropped up in the U.S., but mostly in those who have traveled internationally. Of the 1,222 cutaneous leishmaniasis-positive samples that included travel history, 1,136 were from patients reporting international travel and 86 from non-travelers.

“When patients present with unusual skin conditions, it is helpful to think of leishmaniasis as a possible diagnosis — certainly for travelers, but now we realize we should also be considering this in people who haven’t traveled outside the United States,” Kamb and Cama added.

The Texas Department of State Health Services told MedPage Today in an email that healthcare providers should be aware that leishmaniasis is a reportable disease in the state, and that there have been 38 locally acquired cases reported from 2007 to 2022. Of those acquired in a Texas county, the cases were primarily in central and north Texas.

“If the symptoms are consistent with leishmaniasis, they should consider leishmaniasis as a possibility even if their patient has not traveled outside of the U.S. recently,” Lara M. Anton, a senior press officer, wrote. “Our prevention guidance is the same as it is for all other diseases transmitted by insects — use insect repellent and wear long sleeves and long pants when you are doing outdoor activities.”

Separately, an increase in pet travel and the importation of dogs may be increasing the risk for leishmania infantum, a deadly version of the parasitic disease that affects internal organs and is common in Brazil, East Africa, and India, according to another presentation at the ASTMH meeting by Christine Petersen, DVM, PhD, of the University of Iowa in Iowa City.

Climate change is also spreading its reach. Dogs are the primary reservoir hosts of L. infantum, and though about a million enter U.S. borders every year, it’s estimated that a majority are not adequately screened for infectious diseases.

There are anywhere from 700,000 to a million cases per year of leishmaniasis globally. Female sandflies, which spread the parasites, are tiny in size, and most species feed at dusk and night time.

For the first study, CDC researchers used 2,235 fresh and formalin-fixed tissue samples submitted to the agency’s parasitic diseases reference laboratory from 2005 to 2019. Leishmania species were identified by DNA sequence analysis of the ITS2 locus and genotyped by nucleotide polymorphisms at two positions. Samples included limited patient data on state or territory and travel history. Leishmania was identified in 57% of the samples, and the three most common species were L. panamensis (37%), L. braziliensis (17%), and L. mexicana (13%).

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