A tropical parasitic disease that causes skin lesions may now be in ... - MD Linx

Leishmaniasis is a skin-affecting, tropical disease that may now be endemic to the United States.

Leishmaniasis is a disease caused by the protozoan parasite Leishmania—historically found in the tropics, subtropics, and parts of southern Europe. Transmission occurs when a female sandfly infected by the parasite then bites a human.^[] 

Leishmaniasis takes different forms: Cutaneous Leishmaniasis (CL), mucocutaneous Leishmaniasis (MCL), and visceral Leishmaniasis (VL).^[]

There are several different Leishmania species, including:

• L. (L.) major, L. infantum, and L. (L.) tropica (found in the Mediterranean, the Middle East, Africa, and India)

• L. (L.) amazonensis, L. (L.) chagasi, L. mexicana L, L. (Viannia.) naiffi, L. (V.) braziliensis, and L. (V.) guyanensis (found in the Americas)

The 'old world' strains "predominantly cause self-limiting ulcers, whereas New World species can be severely destructive and even cause death, mostly in relation to MCL disease," the American Journal of Clinical Dermatology reports. The World Health Organization (WHO) says CL is the most prevalent form of Leishmaniasis, leading to life-long scarring as well as serious disability and stigma.^[][] 

Globally, the total at-risk population is about 350 million people, with an overall prevalence of 12 million cases. Leishmaniasis may go underdiagnosed and thus underreported.^[] 

The US Centers for Disease Control and Prevention (CDC) initially reported that cases in the US (primarily in Texas and Oklahoma) are uncommon. They are typically caused by travelers bringing the disease back home with them. However, Scientific American reports that the disease may now be endemic on home soil (as it is in nearly 100 other countries).^[][] 

Despite its prevalence across the globe, a 2022 clinical review of the disease published by the American Journal of Clinical Dermatology says CL is an "emerging and uncontrolled disease and a neglected tropical disease."^[] 

A 2018 JAMA publication found that cases of CL were mounting in the US Further, research presented at a recent Annual Meeting of the American Society of Tropical Medicine and Hygiene (ASTMH) found that US patients with no international travel history were also infected by the parasite, suggesting that there could be a different, local strain of Leishmania.^[] 

The WHO says that the disease not only has a high impact on human health but also on societies at large due to its high economic burden. In fact, as part of the WHO's 2014 initiative to fight vector-borne diseases like Leishmaniasis, the slogan "small bite, big threat" was conceived.^[]  

Treatment and diagnosis

CL can present with many symptoms, including those not related to the skin (like breathing issues, stuffy or runny nose, and difficulty swallowing), in addition to ulcers and erosion in the mouth, tongue, lips, nose, and gums.^[] 

Shirin Mazumder, MD, an infectious disease physician at Methodist Healthcare in Memphis, TN, says that CL often begins with a "pink-colored papule that can develop into a nodule or plaque. This can progress to a painless ulcer with an indurated border. In some cases, multiple lesions may be present with variable clinical appearance. The skin lesions can change in size and appearance over time. There can be involvement of regional lymph nodes near the skin lesions, which can cause lymphadenopathy."

In fact, the CDC says that the lesions can persist for months or even years and that they can develop well after the disease is contracted. "The lesions typically evolve from papules to nodular plaques to ulcerative lesions, with a raised border and central depression, which can be covered by scab or crust; some lesions persist as nodules," the CDC writes.^[] 

According to Abhay Satoskar, PhD, professor of pathology at The Ohio State University College of Medicine, says a punch biopsy or smear from the lesion will be necessary for parasitological diagnosis. "Determination of species of Leishmania is important and can be done by PCR," he adds. 

"The use of multiple testing modalities is recommended to maximize the likelihood of a diagnostic yield," Dr. Mazumder also notes, recommending that MDs reference the support laboratory at the CDC, which can offer diagnostic services. "Serologies are not particularly helpful as the sensitivity and specificity is variable and it cannot distinguish between a past and present infection."

Brian Labus, PhD, MPH, REHS, assistant professor in the Department of Epidemiology and Biostatistics at the School of Public Health at the University of Nevada Las Vegas, adds that MDs will also need to carefully consider where a patient has been when making a diagnosis. "Knowing the exact travel history and local conditions is important when considering a diagnosis of Leishmaniasis," he says. 

"The risk is higher in people who spend time in rural areas—especially those who are outdoors in the evening," Dr. Labus says. MDs will want to consider patients who are ecotourism or adventure travel enthusiasts (such as those who spend time hiking or camping), patients who work in field research, patients who serve in the military, and patients who volunteer in humanitarian missions.

Dr. Satoskar also adds that MDs should also consider whether a patient has proximity to infected animals (like dogs or hyrax) and if they are immunosuppressed, which he says "can lead to recrudescence of a previous latent infection, which could be asymptomatic." The American Journal of Clinical Dermatology says that there is limited evidence around what works best as far as treatment. They suggest that clinical trials—which would likely have to take place in remote areas—are "poorly designed and/or reported upon." Unsurprisingly, the review's authors suggest that the lack of interest in developing a treatment may be rooted in the idea that it simply will not be profitable, as the disease mainly impacts lower and middle-class countries.^[] 

"To inform clinical practice, we urgently need large trials that can produce the necessary data on the long-term effects of current and promising experimental therapies. The establishment of an international platform has been suggested to improve the quality and standardization of future trials," the authors underscore," the authors of the review note.