Zoonotic cutaneous leishmaniasis

Zoonotic cutaneous leishmaniasis (synonyms: acute necrotizing, desert rural leishmaniasis, wet cutaneous leishmaniasis, pendin ulcer).

Epidemiology of zoonotic cutaneous leishmaniasis

In a significant part of the range of L. major, the main reservoir of the pathogen is the large sand gerbil (Rhombomys opimus). Natural infection has been established in the red-tailed and midday gerbils, the long-toed ground squirrel and other rodents, as well as hedgehogs and some predatory animals (weasels). The carriers are mosquitoes of several species of the genus Phlebotomus, mainly Ph. papatasi, they become infectious 6-8 days after bloodsucking on rodents.

A person becomes infected through the bite of an infested mosquito. The disease is characterized by a distinct summer seasonality, coinciding with the summer of mosquitoes. The pathogen is found in rural areas, and there is a general susceptibility to it. In endemic areas, the maximum incidence is found in children and visitors, since most of the local population gets sick in childhood and becomes immune. Epidemic outbreaks are possible, sometimes significant. Repeated diseases are extremely rare.

Zoonotic cutaneous leishmaniasis is widespread in the countries of North and West (and possibly other regions) Africa, Asia (India, Pakistan, Iran, Saudi Arabia, the Yemen Arab Republic and most other countries of West Asia), and is also found in Turkmenistan and Uzbekistan.

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What causes zoonotic cutaneous leishmaniasis?

Zoonotic cutaneous leishmaniasis is caused by L. major. It differs from the pathogen of the anthroponotic subtype of cutaneous leishmaniasis by a number of biological and serological features.

Pathogenesis of zoonotic cutaneous leishmaniasis

The pathological picture of zoonotic cutaneous leishmaniasis is close to anthroponotic leishmaniasis, but the formation of ulceration and scarring of primary leishmanioma occurs at an accelerated rate.

Symptoms of zoonotic cutaneous leishmaniasis

The incubation period of zoonotic cutaneous leishmaniasis is on average 2-3 weeks, but can be longer - up to 3 months. The symptoms of zoonotic cutaneous leishmaniasis are almost the same as those of anthroponotic cutaneous leishmaniasis. The formation of primary leishmanioma is similar to the development of granuloma in the anthroponotic variant, but from the very beginning, leishmanioma in zoonotic leishmaniasis is large in size, sometimes resembles a furuncle with an inflammatory reaction of the surrounding tissues, but is slightly painful. After 1-2 weeks, central necrosis of leishmaniamas begins, ulcers of various shapes are formed, up to 10-15 cm in diameter or more with undermined edges, abundant serous-purulent exudate, painful on palpation.

Around the primary leishmanioma, multiple small nodules are often formed - "semination tubercles", which then turn into ulcers and, merging, form ulcer fields. The number of leishmaniomas in rural leishmaniasis can vary (usually 5-10), a case has been described where there were more than 100.

Leishmaniomas are most often localized on exposed parts of the body - lower and upper limbs, face. After 2-4 (sometimes after 5-6) months, epithelialization and scarring of the ulcer begin. From the moment the papule appears to the formation of a scar, no more than 6-7 months occur.

The entire process from the moment a papule or tubercle appears until complete scarring lasts from 2 to 5-6 months, i.e. significantly shorter than with anthropogenic cutaneous leishmaniasis.

Despite the difference in skin lesions in anthropogenic and zoozoic forms of leishmaniasis, it is sometimes difficult to decide on the basis of the clinical picture to which type the observed case belongs.

After the disease, a stable lifelong immunity develops to both zoonotic and anthroponotic forms of cutaneous leishmaniasis. Repeated diseases occur very rarely.

When ulcers are localized on joint folds, as well as multiple lesions, cutaneous leishmaniasis often leads to temporary disability. If extensive infiltrates and ulcers form on the face, especially on the nose and lips, cosmetic defects subsequently form.

Diagnosis of cutaneous leishmaniasis

Diagnosis of cutaneous leishmaniasis is based on anamnestic, clinical and laboratory data. Of great importance is the indication of the patient's stay in an area endemic for leishmaniasis during the transmission season. The diagnosis of "zoonotic cutaneous leishmaniasis" in endemic areas is usually made based on the clinical picture. In non-endemic areas, laboratory tests are necessary to confirm the diagnosis, and the parasitological diagnosis is of decisive importance - detection of the pathogen in the material taken from the patient's skin lesions. Material for microscopic examination is taken from an unbroken tubercle or marginal infiltrate of the ulcer. For this, the infiltrated area of skin after treatment with alcohol is anemized by compression between the thumb and forefinger, an incision is made with the end of a scalpel or scarifier and a tissue scraping is taken from the bottom and walls of the incision. The scraping is spread on a degreased glass slide and dried in the air. The smears are fixed with methyl alcohol for 3-5 min or 96% ethyl alcohol for 30 min, then stained according to Romanovsky (35-40 min) and examined in an immersion oil system (objective - 90, eyepiece - 7). Leishmania (amastigotes) are found in macrophages, as well as outside them in the form of round or oval bodies 3-5 μm long, 1-3 μm wide. The cytoplasm of leishmania is stained gray-blue, the nucleus - red-violet. Next to the nucleus, a kinetoplast is visible - a round rod-shaped formation smaller than the nucleus and more intensely stained.

In zoonotic cutaneous leishmaniasis, the number of leishmania in lesions is higher in the initial stage of the disease; at the healing stage and with specific treatment, they are detected less frequently.

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How to prevent zoonotic cutaneous leishmaniasis?

Anti-epidemic and preventive measures in foci of zoonotic cutaneous leishmaniasis are significantly more complex and less effective than in anthroponotic leishmaniasis, and depend on the structure of the foci, the type of the predominant reservoir of infection, and the state of the natural biocenosis in the area. Zoonotic cutaneous leishmaniasis can be prevented by widely using all methods of extermination of wild desert rodents. The fight against mosquitoes is carried out according to the same principles as in anthroponotic cutaneous leishmaniasis. Vaccinations with a live culture of L. major are carried out. Vaccination is carried out in the autumn-winter season (but not later than 3 months before leaving for an endemic foci of zoonotic cutaneous leishmaniasis); as a result of vaccination, strong, lifelong immunity develops.

A highly effective preventive measure used to be leishmanization - artificial infection ("vaccination") with a virulent strain of L. major. This method was proposed and studied by the Russian parasitologist E.I. Martsinovsky at the beginning of the 20th century. The process developing after "vaccination" is no different from the natural course of zoonotic cutaneous leishmaniasis. The advantage of this method is the formation of only one leishmanioma, localized at the selected vaccinated site. After scarring, the "vaccinated" develops persistent immunity to repeated infections. Similar prevention was carried out in the past in the USSR (tens of thousands of vaccinated), Israel (thousands of vaccinated), Iran (hundreds of thousands of vaccinated). Sometimes (in 1-5%) very large ulcers developed at the vaccination site. After a mass vaccination campaign in Iran, some of those vaccinated (5%) developed ulcers that did not heal for several years and were difficult to treat. Leishmanization is currently practically not used, with the exception of Uzbekistan, where limited vaccinations are carried out.

According to scientists from Turkmenistan, a good effect was achieved after seasonal (July-August) chemoprophylaxis, which was carried out by weekly administration of 0.1 g (one tablet) of the antimalarial drug pyrimethamine (chloridine).

A very effective measure for preventing leishmaniasis is protection from mosquito attacks. For this purpose, in the evening, immediately before sunset and throughout the night, it is advisable to use special mosquito-repellent substances - repellents, as well as a fine-mesh net.

Ukrainian citizens traveling outside the country may become infected with leishmaniasis when visiting neighboring countries during the active season of infection transmission (May - September): Azerbaijan (VL), Armenia (VL), Georgia (VL), South Kazakhstan (VL, ZKL), Kyrgyzstan (VL), Tajikistan (VL, ZKL), Uzbekistan (ZKL, VL). Crimea should be considered endemic for VL, where isolated cases of VL have been registered in the past.

Among the countries of the far abroad, India poses the greatest danger in relation to kala-azar, where tens of thousands of cases of this disease are registered annually. VL can most often be contracted in the countries of the Middle, Near East and North Africa, where, along with visceral, there are foci of the spread of mucocutaneous leishmaniasis.

The main measure of prevention of zoonotic cutaneous leishmaniasis for citizens, even for a short time, traveling to the named regions, is protection from mosquito attacks. In addition, to prevent zoonotic cutaneous leishmaniasis, vaccination with a live culture and chemoprophylaxis with pyrimethamine can be recommended. It should be noted that vaccinations are contraindicated for children under 1 year old, patients with skin or chronic diseases (tuberculosis, diabetes, etc.) and people who have previously suffered from cutaneous leishmaniasis, and pyrimethamine is contraindicated in diseases of the hematopoietic organs, kidneys and pregnancy.