Berlin: People infected with a common parasitic worm may be twice as likely to acquire HIV than people who are not infected with it, a new study has claimed. W bancrofti causes most cases of lymphatic filariasis or elephantiasis in sub-Saharan Africa.
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, leading to pain, severe disability and social stigma.
The findings by researchers from University of Munich (LMU) in Germany add a strong argument for tackling this neglected disease, which not only causes morbidity, but may also increase the risk of HIV infection.
Lymphatic filariasis affect one in four people in Tanzania, and has long been suspected to be one of the factors driving the HIV epidemic in sub-Saharan Africa, but previous studies have focused on individuals who are already co-infected with both HIV and parasitic worms.
W bancrofti is a mosquito borne parasitic worm (helminth). Worldwide, it causes 90 per cent of lymphatic filariasis cases, a disease commonly known as elephantiasis, which is a neglected tropical disease.
In the study, conducted between 2006 and 2011, 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.
Participants with lymphatic filariasis were twice as likely to become infected with HIV as those without lymphatic filariasis, researchers said.
Overall, there were 1.91 new HIV infections per 100 person-years in patients with lymphatic filariasis, versus 0.80 new HIV infections per 100 person-years in patients without lymphatic filariasis, they said. Of 1,055 HIV-negative patients with lymphatic filariasis, 32 contracted HIV within 3 years, and the effect of lymphatic filariasis was highest among adolescents and young adults, appearing to more than triple the relative risk of HIV acquisition in 14-25-year-olds.
"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," said Inge Kroidl from LMU.
Prevention of W bancrofti infection currently focuses on using mosquito nets and other repellents, as well as treatment with antifilarial drugs such as diethylcarbamazine, albendazole, or ivermectin, researchers said.
The findings were published in The Lancet journal.
