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Protozoan Diseases - LEISHMANIASIS
[Cutaneous leishmaniasis: Chiclero ulcer, espundia, pianbols, uta, and buba (in the Americas); oriental sore, Aleppo boil (in the Old World); Baghdad boil, Delhi boil, Bauru ulcer (in the Middle East). Visceral leishmaniasis: kala-azar]
The causative agents of cutaneous leishmaniasis are Leishmania mexicana and L. brasiliensis in the Americas, and L. tropica in the Old World; and of visceral leishmaniasis, L. donovani, L. infantum, and L. chagasi.
RESERVOIRS AND INCIDENCE:
The geographic distribution of the cutaneous disease is Texas, Mexico, Central and South America, India, Pakistan, the Middle East, southern Russia, the Mediterranean coast and Africa. The distribution of visceral leishmaniasis is poorly reported, but foci probably occur in the Mediterranean basin, the Middle East, India, China, Mexico, Central and South America, and Africa. Wild animals, dogs and humans serve as reservoirs. Domestic dogs may be an important reservoir for humans. Humans are the only known reservoir in India.
Sandfly vectors transmit cutaneous leishmaniasis. Person-to-person, congenital, and blood-borne transmission of visceral leishmaniasis are possible.
DISEASE IN ANIMALS:
L. mexicana causes ulcers of the skin in rodents and other wild animals, usually at the base of the tail. L. braziliensis causes a systemic infection with few skin lesions in wild animals. No skin lesions have been found in dogs. Dogs infected by L. tropica may suffer form cutaneous lesions similar to those found in humans. L. donovani produces visceral lesions in dogs, with enlarged lymph nodes, liver and spleen.
DISEASE IN HUMANS:
In the cutaneous disease, the primary lesion is a painful ulcer or nodule at the site of infection persisting for several months, with residual scarring. Further lesions may develop in skin and mucous membranes. Infiltration by inflammatory cells at the inoculation site supports the growth of the parasite. This progresses into a large area of chronically inflamed granulation tissue. The overlying skin undergoes hyperplasia and then necrosis with spreading ulceration. Metastatic lesions occur with a similar inflammatory reaction. The lesions may heal, become fibrosed or extend indefinitely to produce considerable disfigurement. In the visceral disease, intermittent irregular fever occurs with sweats, enlarged spleen, weight loss and anemia leading to ascites, edema, diarrhea and secondary infections. Dark pigmentation of the skin may occur. There is gross enlargement of liver and spleen. Without treatment, the case fatality rate is 90%.
Definitive diagnosis is achieved by finding the parasite-either the amastigote in stained smears or biopsies, or the motile promastigote in culture. Serologic and skin tests provide only indirect evidence of infection.
Treatment remains inadequate because of drug toxicity, long courses required, and frequent need for hospitalization. The drug of choice is sodium antimony gluconate. Alternative drugs for some forms of infection are amphotericin B and pentamidine.
Use insecticides in house and buildings to control the vector. Eliminate rubbish heaps which are breeding areas for sandflies. Avoid sandfly bites by using insect repellents and protective clothing. Keep dogs indoors after sundown and remove infected dogs.