Roundworm infections found to increase fertility in women

A study of 986 Bolivian women found that on average, a lifetime infection  with a type of roundworm named Ascarius lumbricoides led to an extra two children in the family. Their paper, published in the journal Science, suggests that the worm is altering the host’s immune system, making it easier to become pregnant — in effect, the parasite increases female fertility. The researchers hope this discovery will lead to “novel fertility enhancing drugs.”

Infection with a species of parasitic worm increases the fertility of women, say scientists. Image via bbc

“The effects are unexpectedly large,” said Prof Aaron Blackwell, one of the researchers for the BBC News website.

For the Tsimane population in Bolivia, the average family has nine children, and about 70% of the population lives with a parasitic worm infection. The paper suggests that an infected woman’s immune system changes during pregnancy, making their body less likely to reject the fetus. On average, these women had two more children during their lifetime.

“We think the effects we see are probably due to these infections altering women’s immune systems, such that they become more or less friendly towards a pregnancy,” said Prof Blackwell.

Blackwell added that while using the worms as a fertility treatment was an “intriguing possibility,” there is much more work to be done before “we would recommend anyone try this.” But it’s not all roses with parasitic worms. The nine year long study also found that while Ascaris lumbricoides increases fertility in infected women, hookworms had the exact opposite effect, with families showing an average of three less children.

Prof. Rick Maizels, specialized in the workings between parasitic worms and the immune system said: “It’s horrifying that the hookworm effects are so profound, half of women by 26 or 28 have yet to fall pregnant and that’s a huge effect on life.”

Prof Maizels suggested the hookworm may also be causing anaemia and leading to infertility that way.

Bacteria and viruses try to overwhelm the immune system by multiplying rapidly. But parasites have a different strategy, growing slowly and suppressing the immune system, which is why they make vaccines less effective in the host and lighten allergies. This also makes the mother’s drowsier immune system less likely to attack fetal tissue, increasing fertility.

However, the mechanism is yet to be fully understood. Prof Allan Pacey reported that drugs had been administered to the women in an attempt to alter their immune system to boost IVF, but without success.

“It is very surprising and intriguing to find that infection with this particular species of roundworm actually enhances fertility,” said Prof Allan Pacey, a fertility scientist at the University of Sheffield.

He added: “Whilst I wouldn’t want to suggest that women try and become infected with roundworms as a way of increasing their fertility, further studies of the immunology of women who do have the parasite could ultimately lead to new and novel fertility enhancing drugs.”

Currently, one third of global population is believed to be infected with similar parasites.

2 thoughts on “Roundworm infections found to increase fertility in women

  1. Metin Gunduz

    Well ,let me make an informative and
    helpful scientific comment on this rather “unusual and obvious statistical
    correlation” in between roundworms and Fertility rates . It may indeed help
    certain category of “infertile women” in the future . Roundworms have separate
    sexes; with immense reproductive capacity.Helminthes
    exhibit a sublime co-evolution with the host’s immune system that has enabled
    them to successfully colonize almost all multicellular species present in every
    geographical environment, including over two billion humans on our planet .
    Among
    the most important cell types during helminthic invasion are granulocytes:
    eosinophils , neutrophils and basophils. Depending on the specific context,
    these leukocytes may have pivotal roles in host protection, immunopathology, or
    facilitation of helminthic
    establishment.

    Human bodies response to helminthic(roundworm) establishment into the lumen of
    the intestines and its effect to the protective Immune system of the host body
    are fundamentally -not so different for the Immune system’s adaptation
    in order to differentiate SELF from NON SELF(Foreign) during
    the Implantation of fertilized human embryo to the mothers uterine mucosa
    from its very early stages(Blastocyst) to eventual placental tissue formation
    and the maintenance of pregnancy until the term ; both(roundworm and human
    embryo ) both result in “facilitated immune balance and adaptation ” in
    between the Immune system of the mother and the “ foreign- NON SELF” tissues of
    the embryo and Roundworm . And the most important factor for the reproductive
    fertility of women is –miscarriages- as we know of , they are the result of
    Chromosomal abnormalities, toxic factors ,trauma ,metabolic abnormalities etc.
    OR simply a “rejection of implantation of (embryo) fetus by the host mother’s
    immune system” . This category of causes the “rejection of implantation of
    embryo) fetus by the mother’s immune system –though exact frequency out of all
    miscarriages is not known- MAY be responsible for the large majority of
    miscarriages that occur early or late stages of pregnancies
    .

    Punch
    line is : The Roundworm establishment into the intestines of reproductive age
    women MAY facilitate and optimize the “adaptation” of mother’s immune system for
    NON SELF –co existence- like future pregnancy and statistically decrease the
    rate of miscarriages dramatically that ultimately results in higher fertility
    rate . This issue was investigated indeed in 2012 by an excellent research ( *
    ) at the link .

    ( * ) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3394172/ Granulocytes in Helminth Infection – Who is
    Calling the Shots?

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