Leishmaniasis is a tropical disease caused by a parasite called Leishmania donovanii. Sand flies of the Phlebotomus family spread these parasites through their bites. The different forms of human leishmaniasis include cutaneous, mucous and visceral leishmaniasis. The parasite affects the skin, the mucous membranes and the immune cells like macrophages throughout the body, resulting in severe damage and even death.
About 0.7 to 1.2 million cases of cutaneous, and 0.2 to 0.4 million cases of visceral leishmaniasis, occur every year. It occurs in patches all over the world, except for Australia and Antarctica. It is also rarer above Mexico.
There are about 20 species of Leishmania, spread by approximately 30 species of sandfly. Each fly transmits a specific parasite. These flies are most active from dusk to dawn, which is therefore the time of maximum transmission.
Cutaneous leishmaniasis is usually localized. However, more serious forms occasionally occur, such as disseminated or diffuse forms. The characteristic skin lesions appear from weeks to months after exposure, starting at the bite site. They start as papules, nodules or depressed ulcers with raised margins. These are usually painless, but secondary infection or joint involvement can cause pain to occur. Finally, a burnt-out atrophic ulcer is left.
Multiple lesions can develop, with satellite lesions around the primary lesion. There is associated lymph node enlargement near the site, often before the ulcers occur. Other symptoms include breathing difficulty, nasal congestion, swallowing problems and ulcers of the mouth, tongue, lips, nose or gums.
Mucous or mucocutaneous leishmaniasis is due to spread from the skin to the mucosa. Proper treatment of the cutaneous form lowers the risk. Also called espundia, the disease may take decades to manifest in this form. Persistent nasal symptoms often present first, but oral and pharyngeal lesions also occur. The ulcers can eat away the mucosa, leading to perforation of the bone between the nose and the throat.
Visceral leishmaniasis takes a highly variable time interval to develop, from 2-8 months. Subclinical forms may become evident disease when the immune function is depressed, such as in AIDS patients. There is marked to enormous enlargement of the spleen. The liver and the bone marrow are also involved. It has an immunosuppressive action.
This form is associated with fever, loss of weight, liver and spleen enlargement, lowered numbers of all cell types (red cells, white cells and platelets), high total protein and low albumin levels. In children, it starts with diarrhea, vomiting, cough and fever. Adults more often have bouts of fever, night sweats, tiredness and loss of appetite. There may also be abdominal discomfort, grey discoloration of the skin and weight loss.
Kala azar or black fever is the name of a severe and advanced form of visceral leishmaniasis. Severe visceral leishmaniasis causes death directly, due to bleeding, or due to complicating infections, especially tuberculosis, caused by immune depression. Death often occurs within 2 years without treatment.
Post-kala azar dermal leishmaniasis or PKDL is the appearance of papules or nodules all over the face after the start of treatment of visceral leishmaniasis.
Complications
- Bleeding from nose, face or throat
- Disfigurement due to facial erosion
- Severe deadly infections because of immunosuppression
Diagnosis and treatment
- Serologic tests such as indirect immunofluorescence antibody test
- PCR test for Leishmania
- Direct agglutination assay
- Biopsy and culture of the following organs as indicated: spleen, bone marrow, liver, lymph nodes, skin
- General tests for serum protein and albumin, complete blood count and serum antibody levels
Treatment of the infection is most commonly with antimony compounds, but includes:
- Antimony-containing compounds, mainly meglumine antimoniate and sodium stibogluconate
- Other drugs:
- Amphotericin
- Ketoconazole
- Miltefosine
- Paromomycin
- Pentamidine
- Plastic surgery if needed to correct facial deformities
- Splenectomy if drug resistance is observed
Prevention
Prevention of sandfly bites is by:
- Use of window screening and mesh netting around beds
- Long-sleeved clothing when working outside
- Use of insect repellent
References