Kala-azar in India – progress and challenges towards its elimination as a public health problem

Overview

Visceral leishmaniasis is commonly known as kala-azar (KA), a word coined in the late nineteenth century in India, which literally means “black disease”, referring to the greyish or blackish discolouration of the skin during infection, from the Hindi word for black (kala) and the Persian word for disease (azar). The disease is caused by the parasite L. donovani and it remains one of the major eco-epidemiological hotspots of the world. The earliest cases of KA in India can be traced back to 1824–1825, when an outbreak of fever in Jessore (now in Bangladesh), known as jwar-vikar (“fever disease”), that caused approximately 750 000 deaths over 3 years, has since ascribed to KA.

Before dichlorodiphenyltrichloroethane (DDT) became available, periodic outbreaks of KA occurred in the eastern Indian states of Assam, Bihar, Jharkhand and West Bengal and eastern parts of Uttar Pradesh, lasting for about 10 years, with inter-epidemic periods of 10–15 years. The distribution and prevalence of KA changed dramatically after use of indoor residual insecticidal spraying was instituted in all malaria-affected areas under the national malaria eradication programme in 1950. The DDT spray reduced the prevalence of the vector (sand flies also known as Phlebotomus argentipes, vector species in India) to extremely low levels, resulting in substantial decreases in the number of KA cases. A resurgence occurred in the 1970s, however, with gradual spread, after removal of insecticidal pressure, coupled with a relaxed surveillance system and continued occurrence of post-kala-azar dermal leishmaniasis (PKDL), a skin manifestation of KA sequelae and a potential reservoir of disease. In view of the rising trend in KA, a separate KA control programme was started in 1990–1991.