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Indian visceral leishmaniasis.
Medical expert of the article
Last reviewed: 05.07.2025
[ Epidemiology of Indian visceral leishmaniasis
Kala-azar is an anthroponosis. The source of infection is a sick person in whom the pathogen is present in the skin during the development of post-kala-azar cutaneous leishmanoid. The highest incidence is recorded among children aged 5-9 years. The second most affected group are teenagers.
The vector is the mosquito Phlebotomus (Euphlebotomus) argentipes. In addition to India, kala-azar is found in Bangladesh, Nepal and possibly Pakistan. Visceral leishmaniasis, clinically similar to Indian kala-azar, is common in northeastern China, where the pathogen is carried by Ph. chinensis and Ph. longidudus. Anthroponotic visceral leishmaniasis caused by L. donovani is also found on the African continent - in Kenya, Sudan, Uganda and Ethiopia, where the vector is Ph. martini, and on the Arabian Peninsula - in the southwest of Saudi Arabia and in the mountainous regions of Yemen (vectors are Ph. arabicus and Ph. orientalis).
What causes Indian visceral leishmaniasis?
Indian visceral leishmaniasis is caused by Leishmania donovani, which parasitizes intracellularly in the human body in the amastigote (non-flagellate) stage, and in the carrier's body in the promastigote (flagellate) stage.
Kala-azar (translated from Sanskrit - "black disease") affects adults, and only in 5-6% of cases - children and adolescents. With this type of leishmaniasis, diseases among wild and domestic animals are unknown. The reservoir of the pathogen and the source of infection of mosquitoes is a sick person. Transmission of the pathogen occurs directly from a sick person to a healthy person through a mosquito bite.
Symptoms of Indian Visceral Leishmaniasis
The clinical symptoms of kala-azar are generally similar to those of visceral leishmaniasis, but there are differences of great epidemiological significance. Along with damage to internal organs, it is characterized by the appearance of secondary papules on the skin - leishmanoids with localization of parasites in them, as well as insignificant circulation of leishmania in the skin.
The incubation period for kala-azar (visceral leishmaniasis) is from 20 days to 3-5 months. There are known cases of the incubation period being extended to 2 years. The disease develops slowly. Often, the primary symptoms of Indian visceral leishmaniasis in infected people appear as a result of some provoking factors (infectious disease, pregnancy, etc.). One of the main symptoms of the disease is fever. Most often, the body temperature of patients rises gradually, reaching 38-39 C. Less often, the temperature rises suddenly after chills, the temperature curve is usually undulating. Periods of fever, lasting from several days to a month or more, alternate with periods of remission, occurring at normal temperature. During the same febrile period, the temperature can be constant, subfebrile, remittent.
The skin may acquire a dark color (Indian kala-azar), waxy tint or remain pale. Dark coloring of the skin is explained by hypofunction of the adrenal glands, which is associated with damage to their cortex by leishmania.
As the disease progresses, patients develop cachexia. It is accompanied by petechial or miliary rashes, mainly in the lower extremities, brittle hair with the formation of small focal alopecia areata on the head.
The lymph nodes may be enlarged, but without pronounced periadenitis.
Intracellular parasitism of leishmania causes the development of splenic-hepatic syndrome. The spleen increases significantly in size during the first 3-6 months of the disease; it acquires a dense consistency, its upper border reaches the 7th-6th ribs; the lower edge - to the pelvic cavity. The liver also enlarges. Hepatosplenomegaly is expressed in all patients with visceral leishmaniasis and, with severe emaciation, leads to noticeable dilation of the veins on the abdominal skin.
Changes in the cardiovascular system are manifested in the form of myocardial dystrophy, decreased blood pressure. Significant changes occur in the hematopoietic system, which lead to severe anemia. In this case, leukopenia, aneosinophilia, thrombocytopenia, neutropenia with a shift to the left are observed, ESR is accelerated (up to 92 mm/hour).
In visceral leishmaniasis, changes also affect the respiratory organs, but they are most often caused by complications of the disease caused by pathogenic microflora.
In some countries in hot climate zones (India, Sudan, East Africa, China), 5-10% of patients develop post-kala-azar cutaneous leishmanoids 1-2 years after apparent recovery, which can persist for several years. Cutaneous leishmanoids initially appear as hypopigmented or erythematous spots; later, nodular rashes the size of a lentil are observed. Leishmania may be found in these skin lesions.
Thus, leishmanoids are the sources of infection of sand flies with leishmania, and people themselves, who have cutaneous leishmanoids, serve as reservoirs of kala-azar infection.
Diagnosis of Indian visceral leishmaniasis
The somewhat variable symptoms of Indian visceral leishmaniasis are usually confirmed by leukopenia, high gamma globulin levels in the blood, detectable by paper electrophoresis, and a positive formalin test (the latter is done by adding 1 ml of the patient's serum). In a positive case, the serum becomes thick and opaque 20 minutes after adding formalin.
A complement fixation test can be performed. An immunoluminescent method has also been developed, which is used in early diagnostics before the development of the main symptoms of the disease. L. donovani can be detected in stained preparations from bone marrow, lymph nodes, spleen and liver punctures. Flagellate forms of leishmania can be obtained by sowing infested blood or punctures on special media (NNN-arap) or growing in tissue culture.
Kala-azar must be differentiated from typhoid fever and brucellosis, which are diagnosed by agglutination and blood cultures. Leishmaniasis is differentiated from malaria by examining blood smears. Kala-azar must also be differentiated from schistosomiasis, tuberculosis, leukemia, and reticulosis. Any of these infections may occur along with kala-azar, especially in endemic areas.
Post-kala-azar cutaneous leishmanoids must be differentiated from leprosy, yaws, syphilis, lupus vulgaris, drug hypersensitivity and other dermatoses.
The diagnosis of Indian visceral leishmaniasis and kala-azar, as well as cutaneous leishmaniasis, is based on anamnestic, clinical and laboratory data. The decisive factor is parasitological examination - detection of the pathogen in smears from bone marrow puncture, less often - from lymph nodes. Preparation of smears, fixation, staining and microscopy are similar to those for cutaneous leishmaniasis. As additional diagnostic methods, the immunofluorescence reaction is used.
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Treatment of Indian visceral leishmaniasis
Treatment for Indian visceral leishmaniasis depends on the geographical area in which the disease occurs. In India, the disease is easily cured, while in Sudan and East Africa, it is more resistant.
Specific treatments for visceral leishmaniasis and kala-azar are pentavalent antimonials (meglumine antimanate, sodium stibogluconate). The course lasts 10-20 days, depending on the effectiveness of the therapy. Additional treatments are also widely used: vitamins, antianemic drugs, antibiotics, sulfonamides, etc. Relapses of the disease are possible within 6-10 months, so dispensary observation is carried out for up to 1 year.
Indian visceral leishmaniasis has a favorable prognosis if treatment is started in a timely manner. Acute severe forms without treatment are fatal. In the case of mild forms, spontaneous recovery is possible.
How to prevent Indian visceral leishmaniasis?
Active detection of patients and their timely treatment of Indian visceral leishmaniasis. Mandatory treatment of persons with post-kala-azar cutaneous leishmanoid. Mosquito control: destruction of their breeding sites in populated areas and their environs; maintenance of proper sanitary order in populated areas; treatment of premises with effective insecticides; use of protective curtains and nets treated with insecticides.