Parasitic worms bored into our bodies, steal our nutrients, and sup on our blood, but their effects are not all harmful. A new study of people living in the Amazon suggests that certain intestinal worms increase the number of babies women give birth to.
"This is a very original study," said Rick Maizels parasite immunologist from the University of Edinburgh, who was not connected to the research. "I think this will spark many more inquiries" about the impact of breeding worms.
More than 1 billion people are infected with intestinal worms, mainly in tropical areas with poor sanitation. One of the most common is the giant roundworm Ascaris lumbricoides , which can reach 36 centimeters (14 inches) in length. roundworms giants reside in the small intestine and the sliding of a portion of food from their host. Other worms, such as hookworm Ancylostoma duodenale and Necator americanus , are tiny vampires. They puncture the lining of the intestine and drink the blood of their host.
For all their bad habits and icky, parasites have much in common with a fetus in the womb. The immune system provides a parasite and a fetus as intruders, so both need strategies to support what researchers called immune tolerance. Parasites can cause some of the same immune changes that occur during pregnancy example for the stimulation of regulatory T cells that mater immune attacks.
Because of these similarities, human biologist Aaron Blackwell of the University of California, Santa Barbara, and colleagues wondered whether parasitic infections could open the way to pregnancy. The researchers attempted to answer the question by analyzing data on Tsimane people living in the Amazon rainforest of Bolivia.
The approximately 16,000 Tsimane survive mainly by hunting, fishing and the cultivation of plants such as rice and plantains. Their homeland is first parasitic country. About 15% to 20% of them are home Ascaris , and 56% of them carry hookworms. Infected women in the study were generally not aware they were playing the host of parasites, says Blackwell.
The only health effects researchers were able to detect in almost 1,000 women were Tsimane in individuals carrying hookworms. They had a slightly lower body mass index and lower levels of the protein hemoglobin that carries oxygen in the blood. Hookworms were also detrimental to fertility. They increased the age at which women first gave birth Tsimane and stretched the amount of time between pregnancies. As a result, the team calculated a woman with hookworm would three fewer children in his life than would a woman devoid of parasites. For Tsimane women overall, however, fertility is not a problem because they give birth to an average of nine children.
In contrast, the giant roundworm Ascaris was a godsend for reproduction. It shortened the time between pregnancies and reduces the age at which women give birth first. A woman infected with Ascaris would average two other children in his life than would a free woman parasites, the researchers report online today in Science . "It is somewhat intuitive-cons," says Blackwell.
By tweaking the immune system, Ascaris to reduce inflammation and therefore could promote the design and implementation of the embryo in the womb, the team speculates. Hookworms, however, are not as good for inhibiting inflammation, and suck their blood and nutrients fly could overwhelm the benefits of reproduction they provide, the researchers suggest. Blackwell and her colleagues are currently analyzing women's blood samples to determine which cells and immune molecules to change.
other studies have shown that living bacteria in our body are essential for pregnancy, reproductive immunologist notes Gil Mor at Yale School of Medicine. But the idea that "the worms can affect reproduction, even improving reproduction is quite surprising," said -he. The study highlights the fact that "the state of the immune system is of crucial importance for successful reproduction," says Norbert Gleicher, a reproductive immunologist at Rockefeller University in New York.
Because immune changes triggered by parasites can remove allergy, asthma and autoimmune diseases, several clinical trials have tested whether people infected with worms soothes the symptoms of these conditions. Researchers suspect that Ascaris will never become a treatment of infertility, however. "I would never give my patients that parasite," says Mor. But the results could still lead to new therapies, said Gleicher. "If this [finding] is true, we could develop an immunization that produces the same kind of immune response as does the roundworm infection."
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