Blood-sucking biter, the sand fly

Sand flies, those minuscule tan flies that are approximately one-fourth the size of a mosquito, predominantly inhabit warm regions, particularly rural and forested areas. It is worth noting that in certain parts of the globe, these inconspicuous creatures serve as vectors, transmitting an infectious disease referred to as leishmaniasis, caused by a single-celled parasite. Characteristically active during nighttime, their diminutive size grants them the ability to permeate even the smallest apertures of ordinary mosquito nets on tents or window screens. Given their potential ability to transmit diseases, it is crucial to remain vigilant and take necessary precautions when residing or sojourning in sand fly-infested regions.

Kamb and her colleagues at the CDC have made a remarkable discovery. They have detected cases of leishmaniasis, a disease usually associated with travel to tropical regions, in patients who claim they have not left the United States. Through genetic analysis, they have confirmed the presence of leishmaniasis in tissue samples collected from these patients. This groundbreaking finding was presented at the prestigious annual meeting of the American Society of Tropical Medicine and Hygiene. The affected individuals all experienced leishmaniasis skin infections characterized by the development of small bumps that eventually transform into painful ulcerous sores, occurring days to weeks after being bitten by a sand fly.

This research sheds light on the possibility of localized transmission and highlights the importance of further investigation to better understand the transmission dynamics of this disease. People infected with this particular parasite may not show any symptoms at all, leading them to believe they are perfectly healthy. However, once symptoms manifest, they often appear as ulcers on the skin, resembling tiny volcanic craters.

These sores usually emerge near the location of a recent bite. Due to the parasite's ability to disable nerves in the skin, these ulcers are typically not painful, although they have a propensity to leave scars and can be disfiguring, particularly if they manifest on a person's face. It is important to be aware of these symptoms and seek medical attention promptly to prevent further complications.

People who are asymptomatic may not experience any symptoms, but in cases where symptoms do arise, they may develop skin ulcers resembling small volcanoes with craters," explained Kamb. These sores typically appear near the area where a recent bite occurred. The parasite responsible for this condition disrupts the nerves in the skin, resulting in generally non-painful sores that have a tendency to leave scars. If these ulcers appear on a person's face, they can be particularly disfiguring.Leishmania is capable of infecting various internal organs, such as the liver, spleen, and bone marrow. This particular form of leishmaniasis, known as visceral leishmaniasis, is generally not thought to be transmitted within the United States, but individuals may encounter the infection when traveling to tropical nations. It is crucial to note that if left untreated, this condition can prove fatal.

Most of the skin samples in the CDC study originated from Texas, the sole US state that mandates doctors to report cases of leishmaniasis.A recent research review, published in 2021, highlights that locally acquired instances of the infection have also been documented in southeast Oklahoma.

According to Dr. Luiz Oliveira, a staff scientist at the National Institutes of Health who has extensively researched the transmission of eishmaniasis from sand flies but was not involved in the current study, approximately six cases of leishmaniasis skin infections are reported annually among individuals who have not traveled outside the United States. The World Health Organization designates this disease as endemic,

indicating its regular occurrence in the country, despite its lack of awareness among the majority of people and doctors.

For the current study, presented at the annual meeting of the American Society of Tropical Medicine and Hygiene in Chicago, researchers carefully examined over 2,100 skin samples submitted to the CDC for confirmatory testing between 2005 and 2019. These samples originated from every state in the United States, including Puerto Rico and the Virgin Islands. Out of the total samples, approximately half, specifically 1,222, yielded positive results. Among the positive samples, the majority, which accounts for 1,136, came from individuals who reported a history of international travel. Contrastingly, 86 positive samples were acquired from patients who had no records of travel.An interesting discovery made by the CDC was that the prevalent species of parasite affecting individuals without a history of travel was a bug known as Leishmania mexicana. Within this particular species, the CDC identified two distinct genotypes, or lineages. One of these genotypes, referred to as CCC, was found in nearly 94% of infected non-travelers. Consequently, it appears that this specific parasite type may have become endemic or locally transmitted within the United States.

Sand flies can be effectively repelled by bug sprays containing DEET, while permethrin can be used to eliminate them. Consequently, it is highly advisable to apply bug spray to camping equipment and clothing to ensure protection.

In case a new skin sore appears a few days after a bug bite and fails to heal, it is wise to seek medical treatment. Additionally, informing your doctor about recent outdoor activities, particularly those conducted during the night, is recommended.

To treat leishmaniasis, a month-long course of medication is typically prescribed. These medications function by inhibiting the parasite, with amphotericin B being one example. This antifungal drug is authorized by the US Food and Drug Administration for the treatment of leishmaniasis.

Dr. Wasserberg expresses satisfaction with the study as awareness of leishmaniasis in the United States is notably low.

"Most doctors, when asked whether leishmania exists in the US, tend to respond with 'no way' or 'What is that?'", he remarked.