Leishmaniasis is an infection caused by parasites of the genus leishmania. The zoonotic host are mainly canines and rodents. Sandflies [Phlebotomus spp.] are the main vectors which transmit the disease between animals, from animals to humans and from humans to humans. In Africa, there are two forms of leishmaniasis, visceral and cutaneous.
Visceral Leishmaniasis
Visceral leishmaniasis also known as kala-azar-which is Hindi for black fever [indicating that the skin of some patients turns grey]-is a severe chronic infection of the reticulo-endothelial system which presents with fever, chills, anemia, leucopenia, splenomegaly, weight loss and general debility.
The disease may set in gradually or suddenly. If the onset is gradual, it starts with discomfort in the left hypochondrium as the spleen enlarges-splenomegaly. The disease then runs a chronic course lasting 1-2 years and is associated with chronic fever, hepatosplenomegaly, lymphadenopathy, anemia, and emaciation. In 96% of cases, the patient dies of intercurrent infection if not treated.
Epidemiology : Kala-azar is a disease found in many parts of the world. In Africa, it occurs on the Mediterranean coast and in a belt across the arid and semi-arid areas from Lake Chad in the west to Somalia in the east, excluding the highlands of Ethiopia. The two main foci of the disease are Sudan and eastern Africa. Sporadic cases occur along the Jubba River in Somalia, Karamoja in Uganda and in the Kenyan Rift Valley. In Kenya the main endemic area is in the eastern area is in the eastern part of the country along the Tana, Athi rivers and Baringo county in Rift Valley. In the Sudan, the disease is found in the flood plains of the Nile and its tributaries ; in the early 1990s it caused a large epidemic and thousands of deaths. Without treatment the disease is usually fatal because of intercurrent infections and general wasting.
Prevention and control
Although sandflies are susceptible to insecticides, control of the vector is difficult because the flies breed away from homes. However, in Baringo County of Kenya some measure of control can be achieved with the use of fine insecticide-treated curtains in homes. Destruction of infected dogs and rodents will control the reservoirs. Early diagnosis and treatment can also control the spread of the spread of the disease from human to human.
Cutaneous Leishmaniasis
Cutaneous leishmaniasis is also known as Oriental sore. The disease starts as a small itchy papule, usually on the face, which expands and grow over several weeks to form a single indolent ulcer or multiple ulcers with incubation period of 2-8 weeks. The ulcers[s] may resemble skin tuberculosis of the face [lupus vulgaris]. There may be lymphadenopathy. Rarely, when the lesion infiltrates the skin diffusely, it may resemble lepromatous leprosy. Spontaneous healing starts 2-12 months afterwards. The disease does not spread to involve the viscera.
The disease affects parts of the Sahelian region of West Africa where it is caused by Leishmania tropica major. The zoonotic reservoirs are desert gerbils and dogs and the vectors are phlebotomus papatsi and Phlebotomus sergent. In Eastern Africa, the Ethiopian and Kenyan highlands are affected by the disease caused by Leishmania aethiopia. The zoonotic reservoir is the rock hyrax and the vectors are the high-altitude sandflies Phlebotomus longipes and Phlebotomus pedifer.