Norwegian Infectious Disease Specialists Have New Theory On HIV In Africa 118
mdsolar (1045926) writes in about a Norwegian team who believe they have an explanation about the unique distribution of HIV in Africa. "While around the world a vast majority of AIDS victims are men, Africa has long been the glaring exception: Nearly 60 percent are women. And while there are many theories, no one has been able to prove one. In a modest public health clinic behind a gas station here in South Africa's rural KwaZulu/Natal Province, a team of Norwegian infectious disease specialists think they may have found a new explanation. It is far too soon to say whether they are right. But even skeptics say the explanation is biologically plausible. And if it is proved correct, a low-cost solution has the potential to prevent thousands of infections every year. The Norwegian team believes that African women are more vulnerable to H.I.V. because of a chronic, undiagnosed parasitic disease: genital schistosomiasis (pronounced shis-to-so-MY-a-sis), often nicknamed 'schisto.' The disease, also known as bilharzia and snail fever, is caused by parasitic worms picked up in infested river water. It is marked by fragile sores in the far reaches of the vaginal canal that may serve as entry points for H.I.V., the virus that causes AIDS. Dr. Eyrun F. Kjetland, who leads the Otimati team, says that it is more common than syphilis or herpes, which can also open the way for H.I.V."
Re:Schistosomiasis (Score:5, Informative)
When DNA is replicated in most life-forms, there are extensive proofreading mechanisms which identify replication errors, cut them out of the DNA, and then re-copy those sections.
In contrast, HIV does not extensively proofread new DNA during viral replication. That means that copy errors are quite likely, and over time lead to a heterogeneous population of mutant viruses in an infected person.
Like other viruses, HIV has evolved a balance between correct and incorrect DNA replication which keeps the virus deadly while still evading the immune system.
Re:Reasonable, no smoking gun. (Score:5, Informative)
These authors aren't the only ones to have identified a link between schistosomiasis and HIV, see this 2011 paper [plosntds.org] in PLoS NTD for example.
It seems pretty obvious that any source of genital sores is going to increase the risk of HIV transmission, especially considering that this is the entire basis of increased infection rates for individuals engaging in anal sex.
Still, the link to HIV should only slightly increase our desire to deal with schistosomiasis, because schisto is already the second-most socio-economically devastating illness in the world (after malaria). It causes liver and kidney damage, diarrhea, and vascular disease. It is associated with bladder and colorectal cancers, increases metastasis of other cancer (including breast cancer), impairs mental and physical development in children, and leads to reduced cognitive function and work ability in adults. Further, only one drug is widely used to treat the disease (praziquantel, aka PZQ), and resistance has begun to be observed. 200 million people are believed to require treatment, and more than 600 million are at risk of infection.
Disclaimer: I develop automated drug screening methods against NTD, including schistosomiasis
Re:Reasonable, no smoking gun. (Score:5, Informative)
Thought I would also mention how bizarre the schistosoma (genus) parasites actually are (more details can be found e.g. on wikipedia).
The eggs are deposited into water by infected humans, and infect certain snails. The snails later release a larval stage which has a tail, but no functional digestive system. These penetrate the skin of a human host, losing their tails in the process. The next larval stage is a few micrometers in size and has a sucker; it can now eat. They typically migrate to the lungs, where they will mature for about 1 week, living off the blood of the host.
As they mature into adult parasites, which are up to ~10 mM in size and visible to the naked eye, they migrate again, often to the liver or intestine. If possible, they will also find mates. The female parasite lives in a canal formed of by the male flatworm's body rolling up. The breeding pairs are monogamous and individual parasites may live for decades. During this time, the pair will reproduce continually, producing up to thousands of eggs per week (depending on species).
The eggs are deposited into the infected person's feces, where they find their way back into the water supply, but about half of the eggs become trapped in the body. These eggs mature normally, releasing many antigens which contribute to an active immune response which leads to most of the symptoms of the diseases.
The parasites are highly evolved to fit their human hosts, to the extent that they depend on human enzymes in order to complete certain essential metabolic pathways. They also have genes which are highly similar to human genes, which may help the parasite evade the immune system (such genes could have evolved or been acquired through horizontal gene transfer).
Re:Okay. The West's problem with AIDS is exclusive (Score:5, Informative)