​Celebration and vigil: On India, kala-azar and trachoma

The furore that accompanies an outbreak of a disease is seldom matched by the triumph over the cause of the disease, with some exceptions. The recent achievement India has struck with kala-azar, bringing it to the brink of elimination as a public health issue, or with eliminating bacterial eye infection trachoma, sits squat in that quarter. India will seek WHO certification for eliminating kala-azar, after it brought down the number of cases to under one in 10,000, for two consecutive years now. It is considered the second deadliest parasitic disease after malaria in India. As per figures by the Union Health Ministry, India registered 595 cases and four deaths in 2023, and 339 cases and one death so far this year. The country must retain this achievement for another year to be eligible for WHO certification. Epidemiology makes the differentiation between elimination and eradication of a disease; with elimination, a nation needs to keep the number of cases under a specified limit, which means it ceases to be a public health problem, whereas with eradication, no further cases can occur. While disease eradication is very challenging, and has been achieved only with smallpox, elimination is no cakewalk. Particularly for diseases that do not have a vaccine. Even modern armamentaria come up short while trying for a vaccine for either kala-azar, or trachoma, making the public health achievement all the more special. Kala-azar is spread by the sandfly which passes on the protozoan parasite, Leishmania donovani, and is present in only one of its forms, visceral leishmaniasis. Trachoma, caused by the bacteria, Chlamydia trachomatis, is the leading infectious cause of blindness in the world. India contributed about 11.5% of the cases of kala-azar globally and in the 1970s, trachoma was responsible for 5% of all blindness in the country.

Kala-azar and trachoma share other commonalities — they are classified under the category ‘neglected tropical disease’, and are caused by conditions of poverty and inadequate sanitation; it was a sustained government-run public health campaign that addressed the disease spread, and its social implications — including income, access to nutrition and health services — that finally managed to crack elimination. However, sustained surveillance, post declaration for trachoma and as India moves towards elimination for kala-azar, is key. While celebration post such a well-fought public health campaign is necessary, complacence will erode all gains, considering the disease remains in the community, below the WHO-recommended radar. Efforts to find better cures and vaccines must not be suspended because of present gains; indeed, the vigil must be eternal, or, until the disease is eradicated.