People infected with a parasitic worm called Wuchereria bancrofti may be more likely to acquire HIV than people who are not infected with the worm, a new Lancet study says.

W bancrofti is a mosquito borne parasitic worm. Worldwide, it causes 90 per cent of lymphatic filariasis cases, a disease commonly known as elephantiasis, which is a neglected tropical disease as defined by the World Health Organisation.

Lymphatic filariasis currently affects 120 million people (mostly in Asia, Africa, the western Pacific, and parts of the Caribbean and South America) and causes abnormal enlargement of limbs, causing pain, severe disability and social stigma, the study pointed out.

“W bancrofti worms live in the lymphatic system of patients, often without symptoms, for years. The long disease duration of W bancrofti infection (around 10 years) creates an ongoing immune response, which we suspect might leave infected persons more susceptible to HIV infection,” explained lead author Inge Kroidl from Medical Centre of University of Munich (LMU) in Germany.

In this study, conducted between 2006 and 2011, the researchers analysed 2,699 people in the Kyela district of Mbeya, southwest Tanzania.

Participants were visited once annually for five years and interviews were conducted to measure behavioural factors involved in HIV acquisition such as sexual activity.

Samples of blood, urine, stool, and sputum were collected to test for HIV and for W bancrofti infection, as well as for Schistosoma haematobium, intestinal helminths, tuberculosis, and malaria.