A new study may shed some light on why sub-Saharan Africa is
the hardest-hit region in the world when it comes to HIV/AIDS. Researchers say
people who are infected with parasitic worms are much more vulnerable to
infection with HIV, the AIDS virus.
findings are based on a study of monkeys infected with a worm that causes
schistosomiasis. In many countries, parasites released by
freshwater snails penetrate the skin, eventually causing internal organ damage.
Others become trapped in tissue, causing the body's immune system to react. Up
to 300 million people worldwide may be infected with the parasites, according
to the World Health Organization.
One of those studying the link between schistosomiasis
and HIV infection is Dr. Ruth Ruprecht of the Dana-Farber Cancer Institute at
Harvard Medical School. Dr. Agnes Chenine, formerly with Harvard Medical
School, and Evan Secor of the US Centers for Disease Control, joined her in the
Dr. Ruprecht spoke to VOA English to Africa
Service reporter Joe De Capua about the link, which she says has been suspected
in field research for a while. She and her colleagues concluded that "what
really was needed in the field was a primate model for a co-infection."
She explains further. "We were able to ask the
question how much more virus it takes to get a chronic infection in a monkey
that has no parasites compared to a monkey that has parasites? So what we did
was we had two groups of animals. One group had no parasites, completely
healthy, completely normal. The second group of animals had a new, acute
parasite infection. So we continuously took lower and lower virus doses in one
animal after the next until we found a dose of virus that no longer led to
chronic infection. So that gave us the minimal dose of virus that was required
to still achieve infection," she says.
The findings found that viral infection could be
achieved in some animals with parasites using doses 17-fold lower than for
animals with no parasitic infections. She says, "This is not a small
difference. So in other words, a normal monkey can get exposed to a low dose of
virus and not have chronic AIDS virus infection and a monkey that had the
parasites could get exposed to that same low dose of virus but, because of the
parasite infection, it now also became chronically infected with the AIDS
She says the worms caused an imbalance in the
monkeys' immune systems. She says, "It kind of provides a more fertile ground
for the virus to grow in."
Dr. Ruprecht says it's beneficial to not only
treat people with schistosomiasis to help protect them from HIV, but also those
people who already have both parasites and HIV.
"There are data from a group in Israel that
looked at Ethiopian migrants and some of them were HIV-infected. But when they
were treated for their parasite infections, some of the abnormalities in the
immune system subsided and their virus burden actually also decreased," she
However, those findings have not always been
duplicated in other studies in other countries. Dr. Ruprecht has a theory as to
why. She says, "I believe it's difficult in developing countries to come to
clear-cut conclusions because you treat the parasite, but then the people get
re-infected. And it's a chronic cycle of infection and treatment and
Re-infection can occur so easily
because some much of the freshwater may be contaminated with the flukes or