Leishmaniasis in Emergency Medicine 

Leishmaniasis is a disease caused by the protozoa of the Leishmania species, which is transmitted by the bite of a female sandfly. Leishmaniasis can be classified in several ways (eg, by geography or taxonomy), but clinically, it can present itself in various ways. Therefore, it is more easily classified as cutaneous, mucocutaneous, and visceral leishmaniasis.

A lesion due to leishmaniasis is shown below.

The typical lesions of cutaneous leishmaniasis were described as early as 900 BC and have been referred to as the "Balkan sore" in the Balkans, the "Delhi boil" in India, the "Baghdad boil" in Iraq, and "saldana" in Afghanistan.

Leishmaniae spend part of their life cycle in the gut of the sandfly, but their life cycle is completed in a vertebrate host.

Within the sandfly gut, the protozoa are carried as extracellular promastigotes. Over the course of 4-25 days, these parasites multiply in the gut and migrate toward the pharynx. As the leishmaniae replicate, they create a blockage in the fly's esophagus. The feeding sandfly then clears out its esophagus by expelling leishmaniae into the skin of the host, from where they pass into the blood and tissues of the human host. Promastigotes are phagocytosed into macrophages of the reticuloendothelial system, where they shed their flagella and become amastigotes that multiply by binary fission. When the infected cells rupture, the infection spreads to other macrophages and is carried throughout the body. Temperature is an important factor that helps determine the localization of leishmanial lesions. Species causing visceral leishmaniasis are able to grow at core temperatures, while those responsible for cutaneous leishmaniasis grow best at lower temperatures.

Although the Leishmania species differ clinically and biologically, their characteristics overlap and each clinical syndrome can be produced by multiple species of Leishmania.

In cutaneous leishmaniasis, the hallmark of the disease is skin lesions, which can spontaneously heal in 2-10 months.

In mucocutaneous leishmaniasis, mucosal ulcerations usually develop by metastasis from disseminated protozoa rather than by local spread. Secondary infection plays a prominent role in the size and persistence of ulcers. Ulcer progression is slow and steady.

Typically, visceral leishmaniasis incubates for weeks to months before becoming clinically apparent. The disease can be subacute, acute, or chronic, and can manifest in patients who are immunocompromised years after they have left endemic regions.

Frequency

United States

Leishmaniasis is rare in the United States but has been reported in areas bordering Mexico such as rural southern Texas. Most of the cases found in the United States are acquired elsewhere such as in travelers to Latin America. More than 500 cases of leishmaniasis were diagnosed over an 18-month period in soldiers returning to the United States from the Middle East, especially from Iraq. A large portion of these was identified as cutaneous leishmaniasis.^[1]

International

The Centers for Disease Control and Prevention (CDC) estimates that approximately 1.5 million new cases of cutaneous leishmaniasis and 500,000 cases of visceral leishmaniasis occur worldwide each year. Mucocutaneous leishmaniasis is less common. The prevalence of the disease is increasing, with estimates of 12 million people currently infected worldwide. Once thought of only as a disease affecting rural areas, the disease remains common in the face of increasing urbanization.

Incidence is highest in tropical and subtropical regions where conditions are favorable for sandflies. Most cases of cutaneous leishmaniasis are seen in Afghanistan, Brazil, Iran, Iraq, Peru, and Saudi Arabia, while visceral leishmaniasis is most common in Bangladesh, Brazil, India, Nepal, and Sudan.

Leishmaniasis is found in some parts of 88 countries within Central America, South America, Africa, India, the Middle East, Asia, southern Europe, and the Mediterranean.

Australia and the South Pacific are not considered regions where leishmaniasis is present as an endemic illness.

Mortality/Morbidity

Poor nutrition, infection, and other stresses predispose patients to increased morbidity and mortality rates. Conditions such as complex emergencies, mass migration, and famine accelerate the development of the disease. Leishmaniasis is responsible for an estimated more than 80,000 deaths annually.

Co-infection with HIV is also increasingly recognized as an emerging threat. HIV has been implicated in cases of visceral leishmaniasis in areas previously untouched by this form of the disease. For example, visceral leishmaniasis has appeared in southern Europe among intravenous drug users.

• Untreated cutaneous leishmaniasis can progress to disseminated mucocutaneous leishmaniasis, and death can occur from secondary infection.
• Visceral leishmaniasis is progressive. Mortality rates in untreated cases range from 75-95% or as high as 100% within 2 years in developing countries.
• Of great importance is the social burden placed by the morbidity of the disease, which can cause severe deformities and disfigurement and lead to social isolation.

Sex

Males are more commonly infected than females, most likely because of their increased exposure to sandflies. Visceral leishmaniasis, in particular, has been shown to be twice as common in males than in females.

Age

A fatal type of visceral leishmaniasis, which is found along the Mediterranean, specifically affects infants. Although occurrence is proportional to sandfly exposure, children younger than 15 years represent a large proportion of cases in endemic areas.

• Untreated visceral leishmaniasis in a pregnant mother can also have consequences on the fetus or result in congenital visceral leishmaniasis.
• Certain types of visceral leishmaniasis affect certain pediatric age groups more than others (eg, visceral leishmaniasis in the Mediterranean Basin caused by Leishmania infantum mainly affects children aged 1-4 y).