American cutaneous mucosal and cutaneous leishmanioses

In the Eastern Hemisphere, cutaneous leishmaniasis is caused by parasites of the L. tropica complex; the disease is often called oriental ulcer. In the Western Hemisphere, this form of the disease is caused by leishmania of the L. mexicana and L. brasiliensis complexes. Some parasites of the L. brasiliensis complex can spread through the lymphatics.

Some people infected with L. aephiopica and some species of the L. mexicana complex develop diffuse cutaneous leishmaniasis; due to specific disturbances in the cellular immune system, amastigotes continue to proliferate and the epidermis does not ulcerate.

Diagnosis and treatment of American cutaneous leishmaniasis are carried out by the same methods and with the same drugs as for Old World cutaneous leishmaniasis.

Worldwide, 90% of all cases of cutaneous and mucocutaneous leishmaniasis occur in Brazil, Peru, Algeria, Saudi Arabia, Syria and Iran.

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New World cutaneous leishmaniasis of the L. mexikana complex

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Reasons

The causative agent of New World cutaneous leishmaniasis is L. mexikana, which includes 5 subspecies of leishmania.

Mexican leishmaniasis occurs in southern Mexico (Yucatan Peninsula), Guatemala and adjacent countries. It is a zoonosis, the natural foci of which are associated with landscapes of humid tropical forests. Most often, one leishmanioma occurs, mainly on the skin of the ear, which heals without complications. However, there are frequent cases (about 40%) of chronic course of the disease with the formation of deep ulcers and destruction of cartilaginous tissue of the ears, nose and larynx.

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Epidemiology

Most forms of this disease are natural focal zoonoses. Rodents, marsupials, and many wild and domestic animals can be sources and reservoirs of pathogens. The main carriers are mosquitoes of the genera Lutzomyia and Psychodopygus, many species of which attack humans in their biotopes during daylight hours, during industrial activities. The disease is widespread mainly in rural areas, and occurs in cities as an exception. The maximum number of cases occurs during the rainy season. Susceptibility is universal (people of all ages, both locals and visitors, get sick). The disease is registered in all Latin American countries (possibly with the exception of Chile), in the southern regions of the United States (Texas).

In Brazil (Amazon basin) L. mexicana amazonensis has been isolated, affecting mainly wild animals (rats, mice, opossums, foxes, pacas) living in forests, on river banks and in swampy areas. Humans are extremely rarely involved in the epidemic process. In case of infection, the disease in humans is very severe, in 30% of cases it is not treatable, in the form of diffuse cutaneous leishmaniasis it leads to disfigurement.

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Pathogenesis and pathological picture

Pathogenesis is similar in many features to that of cutaneous leishmaniasis of the Old World. Deeper skin lesions (down to the hypodermis) and comparatively frequent spread of the pathological process to the mucous membranes (up to the submucous layer) of the nose, mouth, pharynx, larynx, and less frequently to the genitals are noted. Immunity is unstable and weak.

Symptoms

The incubation period lasts from 2-3 weeks to 1-3 months. There are no fundamental differences in the clinical picture of skin lesions in New and Old World leishmaniasis.

At first, ulcers are usually deeper, sometimes accompanied by lymphangitis and lymphadenitis. The most important feature of cutaneous leishmaniasis of the New World is the frequent involvement of mucous membranes in the pathological process. As a rule, mucous membranes are affected 1-2 years after the development of ulcers on the skin. Ulcer-necrotic changes in the mucous membranes lead to deep deformations of the nose, ears, nasal part of the pharynx, respiratory tract, genitals, disfiguring and disabling patients.

Several forms of New World cutaneous leishmaniasis are known.

In Mexico, this disease is called the ulcer of "chicleros" - rubber sap collectors, about 30% of whom fall ill in the first year of work in the forest. The disease usually proceeds in a relatively mild form. Most often, one leishmanioma occurs on open parts of the body accessible to mosquitoes, which heals without complications in a few months. When lesions are localized on the auricle, which is observed in 40% of cases, the disease takes a long chronic course and leads to deformation of the auricle. The mucous membranes are not affected. However, there are isolated cases when deep ulcers form with the destruction of the cartilaginous tissue of the nose.

Pathogens are found in the ulcer only during the first three months of the disease.

Cutaneous leishmaniasis caused by other members of the L. mexicana complex - L. mexicana amazonemis and L. mexicana pifanoi

Cutaneous leishmaniasis caused by other members of the L. mexicana complex, L. mexicana amazonemis and L. mexicana pifanoi, often leads to the development of diffuse cutaneous leishmaniasis. Clinically, it resembles the diffuse cutaneous leishmaniasis of the Old World, is difficult to treat, and is most often recorded in the Dominican Republic

Diagnostics and prevention

Diagnosis and prevention are the same as for Old World cutaneous leishmaniasis.

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