Researchers have stumbled upon tantalizing evidence of an unknown virus that may be responsible for the persistence of kala-azar or visceral leishmaniasis, a parasite infection that has spawned epidemics and sickened thousands of Indians for over a century.
It’s still early to pointedly blame the virus but its discovery portends a new kind of treatment regime and may aid attempts to eradicate the disease.
Historically, the parasite Leishmania donovani is believed to be responsible for the dreaded infection. People get infected when bitten by an insect called the sandfly, which harbours the disease-causing parasite.
This month, a group of scientists from West Bengal and Uttar Pradesh said that another parasite may be involved. Another parasite called Leptomonas seymouri may also be present, according to Subhajit Biswas, one of the scientists involved in the study.
The researchers inferred this after they found the L seymouri and a virus called Lepsey NLV1 within it in 20 of 22 biological samples of patients who had a residual L donovani infection. They reported their findings in an online version of the peer-reviewed Archives of Virology.
Kala-azar is endemic to the Indian subcontinent in 119 districts in four countries (Bangladesh, Bhutan, India and Nepal). India itself accounts for half the global burden of the disease. If untreated, kala-azar can kill within two years of the onset of the ailment, though the availability of a range of drugs has meant that less than one in 1,000 now succumbs to the disease.
It is also called Visceral Leishmaniasis, Black Fever and Dum Dum Fever. It is the most severe form of leishmaniasis and, without proper diagnosis and treatment, is associated with a high death rate.
Leishmaniasis is a disease caused by protozoan parasites of the Leishmania genus. The life cycle of Leishmania is completed in two hosts, humans and sandflies. The adult female sandfly is a bloodsucker, usually feeding at night on sleeping prey. The parasite migrates to the internal organs such as the liver, spleen (hence “visceral”), and bone marrow, and, if left untreated, will almost always result in the death of the host. Signs and symptoms include fever, weight loss, fatigue, anaemia and substantial swelling of the liver and spleen. Of particular concern, according to the World Health Organization (WHO), is the emerging problem of HIV/VL co-infection.
This disease is the second-largest parasitic killer in the world (after malaria), responsible for an estimated 200,000 to 400,000 infections each year worldwide.