Tropical Parasite Invades US, Causing Skin Infections

Imagine a world where a tiny, inconspicuous insect, smaller than a mosquito, is silently invading the U.S. Sand flies, as they are known, typically dwell in warm, rural, and forested areas, and they operate under the shroud of darkness. These stealthy creatures can infiltrate your life even through ordinary mosquito nets, posing a unique threat.

These sand flies are not just a mere nuisance; they've been harboring a potentially deadly secret. In various corners of the globe, they act as vectors for a parasite, a microscopic organism, that gives rise to a devastating condition known as leishmaniasis. Dr. Mary Kamb, a medical epidemiologist at the U.S. Centers for Disease Control and Prevention, explained, "Sometimes you don't even notice that you've been bitten."

Dr. Kamb and her colleagues at the CDC have now uncovered a disturbing trend. They've identified cases of leishmaniasis in patients who swear they haven't ventured beyond U.S. borders. This revelation comes as a genetic analysis of tissue samples was presented at the annual meeting of the American Society of Tropical Medicine and Hygiene.

These patients had one thing in common: leishmaniasis skin infections. These infections typically begin with a small bump, which soon transforms into ulcerous sores. While pain may be absent, these disfiguring sores leave a lasting mark, especially if they appear on one's face. Even more alarming is that this parasite can invade internal organs like the liver, spleen, and bone marrow, a severe form of the disease that can be fatal if left untreated.

Most of the skin samples analyzed were from Texas, the sole U.S. state mandating the reporting of leishmaniasis cases. However, a review published in 2021 suggests that locally acquired infections have also been documented in southeast Oklahoma.

It's noteworthy that around six cases of leishmaniasis skin infections surface in non-travelers within the U.S. annually. This disease is far more prevalent than people realize, earning it a spot on the World Health Organization's list of regularly occurring diseases in the country.

But what makes this situation all the more perplexing is that the sandflies responsible for transmitting the disease have been expanding their territory in recent years. Some varieties of these biting insects have ventured as far north as Delaware, New Jersey, Ohio, and Maryland, possibly paving the way for transmission in previously unaffected regions.

The researchers analyzed over 2,100 skin samples from every corner of the United States, shedding light on the scale of this issue. It was startling to find that nearly half of these samples tested positive for leishmaniasis. Most of these infections could be traced back to international travel, but alarmingly, 86 cases had no travel history. This indicates that a particular strain, Leishmania Mexican, has potentially become endemic in the U.S.

Experts believe rats may be the carriers of this parasite, and when sand flies feed on infected rats, they can transmit the disease to humans. Fortunately, leishmaniasis is not directly contagious among humans.

In the face of this hidden menace, vigilance is key. Bug sprays containing DEET can repel sand flies, and permethrin can eliminate them. If you find an unexplained skin sore following a bug bite that refuses to heal, seeking medical attention is wise, especially if you've spent time outdoors, particularly at night.

Treatment is available, and it's crucial to initiate it early. A month-long regimen of medications can thwart the parasite's progress. While the presence of leishmaniasis may be an unsettling revelation, knowledge and precaution are our best allies in the fight against this elusive enemy. So, the next time you venture into the warm, rural wilderness, arm yourself with awareness, repellent, and vigilance.