L. donovani itself is not usually the direct cause of death in people with kala-azar, however. Pneumonia, tuberculosis, and dysentery are omnipresent in the immuno-depressed regions where leishmaniasis thrives, and, as with AIDS, it is these opportunistic infections that are more likely to kill, flaring up in a host whose immune system has been weakened by the L. donovani infection. Progress of the disease is extremely variable, taking anywhere from one to twenty weeks, but a typical duration for the Sudanese strain of the disease is narrower, between twelve and sixteen weeks.Even with recovery, kala-azar does not always leave its hosts unmarked. Some time after successful treatment—generally a few months with African kala-azar, or as much as several years with the Indian strain—a secondary form of the disease may set in, called post kala-azar dermal leishmaniasis, or PKDL. This condition manifests first as small, measle-like skin lesions on the face, which gradually increase in size and spread over the body. Eventually the lesions may coalesce to form disfiguring, swollen structures resembling leprosy, and occasionally causing blindness if they spread to the eyes. (This disease is not the same as cutaneous leishmaniasis, a milder disease caused by another protozoan of the Leishmania genus which also causes skin lesions.) Cause
Two species of Leishmania are known to give rise to the visceral form of the disease.
Another common name, kala-azar (Hindustani: काला आज़ार (Devanagari) کالا آزار (Nastaleeq) kālā āzār), is derived from kala which means black in Sanskrit, as well as in the languages descended from it, including Assamese, Hindi and Urdu; the word azar means Fever in Persian and Hindustani; as such the disease is named for the darkening of the skin on the extremities and abdomen that is a symptom of the Indian form of the disease. The agent of the disease was also first isolated in India by Scottish doctor William Leishman (who observed the parasite in spleen smears of a soldier who died of the disease in Dumdum, Calcutta, India - hence the name dumdum fever) and Irish physician Charles Donovan, working independently of each other. As they published their discovery almost simultaneously, the species was named for both of them—Leishmania donovani. Today, the name kala-azar is used interchangeably with the scientific name visceral leishmaniasis for the most acute form of the disease caused by L. donovani. The disease is endemic in West Bengal, where it was first discovered, but is seen at its most deadly in north and east Africa. It can also be found throughout the Arab world and southern Europe (where the causative organism is L. infantum), and a slightly different strain of the pathogen, L. chagasi, is responsible for leishmaniasis in the new world.