| Leishmaniasis (cutaneous and visceral) |
Kala-azar, Black Fever, Dumdum Fever, Oriental Sore, Tropical Sore, Uta, Chiclero ulcer, Aleppo boi, Pian bois; Espundia Etiology Leishmaniasis results from infection by various species of Leishmania, a proto-zoan parasite of the family Trypanosomatidae (order Kinetoplastida). Approximately 30 species have been described, and at least 20 of these organisms are pathogenic for mammals. The genus Leishmania contains two subgenera, Leishmania and Viannia, which are differentiated by where they multiply in the digestive tract of the insect vector. The classification of Leishmania is complex and, in some cases, controversial; more than one species name may be used for an organism, and some names may eventually be invalidated. Human visceral leishmaniasis is primarily caused by Leishmania donovani (which includes L. archibaldi) and L. infantum/ L. chagasi. L. donovani is anthropo-notic; it is mainly transmitted between people, who act as the reservoir hosts. L. infan-tum is zoonotic. Transmission Leishmania spp. are usually transmitted indirectly between hosts by sand flies of the genera Phlebotomus and Lutzomyia, which are biological vectors. Each species of Leishmania is adapted to transmission in certain species of sandflies. Only the females feed on blood. Sand fly activity occurs when it is humid, and there is no wind or rain. These insects are usually most active at dawn, dusk and during the night, but they will bite if they are disturbed in their hiding places (animal burrows, holes in trees, caves, houses and other relatively cool, humid loca-tions) during the day. They are attracted to light and may enter buildings at night. Transovarial transmission of Leishmania does not seem to occur, and in areas with cold temperatures, the parasite overwinters in mammalian hosts. Other arthropods including ticks (Dermacentor variabilis and Rhipicephalus sanguineus) and canine fleas may also act as mechanical vectors. Where sand flies transmit Leishmania spp., ticks and fleas are probably unimportant in the epidemiology of the disease; however, they might be involved in rare cases of dog-to-dog trans-mission in other locations. Clinical Signs Two forms of leishmaniasis, cutaneous and visceral, are seen in humans. Some texts also distinguish a muco-cutaneous form, while others consider it to be a subset of cutaneous leishmaniasis. The form of the disease and the usual clinical signs vary with the species of Leishmania. Some infections remain asymptomatic. Cutaneous leishmaniasis: Depending on the species of Leishmania, ulcers, smooth nodules, flat plaques or hyperkeratotic wart-like lesions may be seen. Visceral leishmaniasis: The most common symptoms of visceral leishmaniasis are a prolonged undulant fever, weight loss, decreased appetite, signs of anemia, and abdominal distension with spleno-megaly and hepatomegaly. Thrombocytopenia may cause bleeding tendencies, including petechiae or hemorrhages on the mucous membranes, and leukopenia can result in increased susceptibility to other infections. Dogs: signs include lethargy, weight loss, a decreased appetite, anemia, sple-nomegaly and local or generalized lymphadenopathy. Fever can be intermittent, and is absent in many cases. Bleeding disorders including epistaxis, hematuria and melena can also be seen. Treatment Visceral or cutaneous leishmaniasis can usually be cured in immunocompetent individuals. Pentavalent antimonials can be used where the parasites are sensitive to these drugs, but resistance is a major problem in some areas. Other drugs such as allupurinol, amphotericin B or liposomal amphotericin B, and miltefosine may also be used. Most of the drugs used to treat leishmaniasis must be given parenterally. Visceral leishmaniasis in AIDS patients is often resistant to treatment, and many patients relapse. |
