Scientists have investigated trichomoniasis, a sexually transmitted disease caused by the parasite Trichomonas vaginalis, a type of organism called protozoa. Rather than invade human cells, the parasite attaches to the surface and feed on them.

Trichomoniasis is common for all sexually transmitted bacterial diseases together annually affects about 250 million people worldwide. People infected with the parasite are especially vulnerable to sexually transmitted diseases, including HIV, which causes AIDS, and HPV, which is linked to cervical cancer and prostate cancer. In addition, complications of trichomoniasis include miscarriage, premature delivery, low birth weight baby and infertility.

"Trichomoniasis is associated with devastating consequences for women due to inflammation and risks associated with reproductive disease," said Raina Fichorova, Harvard Medical School and Brigham and Women's Hospital in Boston.

Interestingly, over 80 percent of these parasites are, in turn, infected with a virus Trichomonasvirus.

"Unlike the influenza virus, for example, the virus can not spread from one cell to another," explains Max Nibert of Harvard Medical School. "It just spreads between cells when the host is divided."

The virus appears to have no detrimental effect on the parasite and the powerful of this virus has led researchers to suspect that it might actually benefit, in some way, to the parasite. For more information, the researchers infected women Trichomonas and studied how the two versions of the parasite, the virus infected and virus free, affecting human cells grown in the laboratory.

Currently, trichomoniasis is usual with metronidazole. However, when the researchers killed Trichomonas infected with this drug, the parasites found freed dying viruses that inflamed human cells.

The virus, in itself, does not infect human cells, but if aggravated the harmful effects of the parasite. These findings may explain why metronidazole not prevent the harmful effects of trichomoniasis may have on reproduction of women because, in fact, may worsen the box to force the parasite to release harmful viruses.

"Antibiotic treatment may actually worsen the situation by amplification of inflammation," said Fichorova.

Inflammation may also help explain why the parasite makes people more vulnerable to other sexually transmitted diseases (STDs). "Inflammation can destroy or weaken the barriers that protect us from infections," adds Fichorova.

Scientists are not sure whether the virus really helps the parasite somehow. Future research should explore how much of the structure of the virus and its life cycle is more vulnerable to drugs. "To treat this infection safely, we must not only fight against the parasite, but against the virus at the same time." concludes Fichorova

-------------------------------------------------- ------------------------------

You can find more details about the research in the article: “Endobiont Viruses Sensed by the Human Host – Beyond Conventional Antiparasitic Therapy” published in PLOS ONE on November 7, 2012.

Picture: [Public domain], via Wikimedia Commons