- A rare disease spread by the bite of sandflies could be on the rise in the US.
- Previously associated with traveling to tropical regions like India and Central America, cutaneous leishmaniasis appears to have a foothold in southern states.
- It is known to cause sores and lesions on the skin that can leave lifelong scars if untreated.
A tropical infection that causes skin lesions and disfiguring scars, once known as a “traveler’s disease,” could be right at home in the southern United States.
Cutaneous leishmaniasis is spread through the bite of sandflies carrying a single-celled parasite known as Leishmania, of which there are 30 known varieties that can infect mammals.
Sandflies are tiny, blood-sucking insects about the quarter of the size of a mosquito — so small that they can evade common prophylactics like mosquito nets and window screens. Also like mosquitoes, sandflies are disease-carrying “vectors” that feed on blood from humans and animals.
Cutaneous leishmaniasis is predominantly found in the tropics, India, and Central and South America. In the United States, it has garnered the moniker of a “traveler’s disease,” because those infected with it have been identified after returning from a region where it is more common.
No longer a “traveler’s disease”
But that could be changing. Data shows that infections are showing up in people in the US who indicated they had no travel history, meaning the disease is being spread endemically within the US — a worrisome new finding.
Researchers at the Centers for Disease Control and Prevention (CDC) presented their findings this month at the Annual Meeting of the American Society of Tropical Medicine and Hygiene (ASTMH).
The research has not yet been published in a peer-reviewed journal.
In the study, researchers examined over 2,100 tissue samples collected between 2005-2019 that were submitted to the CDC for presumptive testing for cutaneous leishmaniasis. The samples were collected from all fifty states, as well as Puerto Rico and the US Virgin Islands. The disease was identified in more than 50% (1,222) of the submitted samples.
Curiously, researchers found that some of the samples were submitted from individuals who were identified as “non-travelers,” meaning they hadn’t left the country. In total, 86 samples were identified as coming from non-travelers.
“That’s not a surprise. I think there’s been some preliminary speculation about that in the past,” said Dr. Stanley Deresinksi, a Clinical Professor of Infectious Diseases at Stanford University. Deresinski wasn’t affiliated with the research.
“All sorts of mammals can be the reservoir for these parasites, not just humans, but other animals. So, it’s not terribly surprising that that’s [going to] occur,” he told Healthline.
A genomic fingerprint
Researchers have also found more definitive evidence that these infections were truly endemic and acquired in the U.S.
First, they identified that the samples from non-travelers most often contained Leishmania mexicana, one of the many varieties of the parasite. Then, using DNA testing, researchers found two genotypes, unique genetic signatures, among the samples of Leishmania mexicana.
One of those genetic variations was found in 31% of all samples from non-travelers, but less than 2% from individuals who had traveled outside the country. The finding offers strong evidence that the specific Leishmania mexicana variation is endemic to the United States and spreading among the local population.
Texas appears to be the epicenter. Non-travelers infected with this variation were almost entirely (94%) from Texas.
“We saw that most samples from Texas have this genotype, which is a little different from those outside the US. So that was very interesting. Most of the cases from patients who never reported travel outside of the US had this genomic signature,” said Dr. Marcos de Almeida, PhD, the primary author of the study, and a research molecular biologist for the CDC.
Most cases found in Texas
Texas is currently the only state in the nation that requires national reporting of cases of leishmaniasis, apparently because it is one of the few places in the US where doctors have taken notice.
“This disease isn’t nationally reported. It’s not reported by any state with the exception of Texas. The clinicians in the United States think of it as a tropical disease or subtropical disease, not something you’d expect in somebody living in the United States. So people don’t necessarily think of it when they see these funny skin lesions,” Dr. Mary Kamb, MPH, with the Division of Parasitic Diseases and Malaria at CDC’s National Center for Emerging and Zoonotic Infections, told Healthline. Kamb also worked on the report.
But the disease is likely underreported, according to Deresinski.
“It’s obviously very uncommon,” he said. “Although I think most healthcare workers aren’t really aware of the disease. Globally, the WHO also warns that the disease is underreported.
What is cutaneous leishmaniasis?
Cutaneous leishmaniasis is the most common of the three forms of the disease leishmaniasis. The World Health Organization estimates that there are between 600,000 and one million new cases annually. Once an individual has contracted the Leishmania parasite, lesions or sores can appear on the skin weeks or months after the initial sandfly bite. The sores are capable of leaving disfiguring lifelong scars. However, not all people will have symptoms.
Leishmaniasis can also appear in two other more serious ways: mucosal leishmaniasis and visceral leishmaniasis.
Mucosal leishmaniasis is less common and develops when the infection spreads to the membranes of the nose, mouth, or throat.
Visceral leishmaniasis, also known as kala-azar or black fever, is the most deadly form of the disease. It is fatal in more than 95% of cases if left untreated. Visceral leishmaniasis affects multiple internal organs including the liver, spleen, and bone marrow. Symptoms include swelling of the affected organs, low blood count, and low platelet count.
No vaccines or drugs are currently available to prevent leishmaniasis. There are drug therapies that are used to treat the disease if an infection does occur.
Preventing sandfly bites is the only true preventative measure.
While the risk of leishmaniasis is still very low in the United States, cases do occur from time to time. If you’re in Texas or other southern states (the disease has also been documented in Oklahoma), or are planning to travel to a region where the disease is prominent, you can lower your risk of being bitten by:
- Being aware if you are in a region that sandflies inhabit
- Keeping your skin covered with long clothing
- Using insect repellents on skin and clothing
- Ensuring that your house is properly sealed and screened from insects
The bottom line
Cutaneous leishmaniasis is spread through the bite of sandflies infected with the parasite Leishmania. The disease causes sores and lesions on the skin that can lead to lifelong scarring.
The disease is predominantly found in the tropics, India, and Central and South America.
New research from the CDC indicates that the disease may be present in parts of the southern United States.
What to Know About The Tropical Disease Now Spreading in the U.S.
Source: Pinoy Lang Sakalam
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