NAIROBI – New research has found that intestinal worm infections may put women at increased risk of sexually transmitted viral infections (STIs) – a discovery that researchers hope will help health workers to explain why STIs can be more virulent in areas such as sub-Saharan Africa, where worm infections are common.

The study, published in Cell Host and Microbe, discovered that intestinal worm infection can change and increase the likelihood of Herpes simplex virus type 2 (HSV-2) infection, which is the main cause of genital herpes.

The study was conducted by an international team led by researchers from the University of Cape Town (UCT) and in collaboration with the University of Birmingham, University of Bonn, Norwegian University of Science and Technology, University of Liege and the French National Centre for Scientific Research

“We have found that intestinal worm infection can change female reproductive tract (FRT) immunity by causing a worm associated immune response in the FRT, even though the worms never reside there,” said Dr William Horsnell from UCT’s Institute of Infectious Disease and Molecular Medicine, the lead author.

“In particular, we found that worms induced eosinophils in the vagina. These are immune cells associated with anti-worm immunity and can cause allergic disease. Their role in the FRT is not known.”

Horsnell added that if the eosinophils immune cells were “targetted with molecules that can deplete them, we can prevent the increase in pathology”.

“This suggests that this pathology can be targeted and may be prevented or reduced by using existing drugs. The research also shows that eosinophils can have a very important role to play in vaginal immunity. This has never been so strongly demonstrated before,” he added.

More Research Needed

The correlation between STIs and intestinal worm infections is an area of research that has not been given much attention in the past, said Horsnell, despite the fact that the rates of intestinal worm infections in sub-Saharan Africa are “huge,” especially since worm infections in the intestine can change immunity in other parts of the body.

For example, even though researchers would expect 10-20% of study participants to have an active ascaris or hookworm infection, evidence of infection was well over 50%, explained Dr Horsnell.

While UCT has an active vaginal mucosal (mucous membranes of the vagina) immunity unit that looks at microorganisms that influence vaginal immunity, researchers had “never looked at [whether] worm infection may also indirectly influence the vagina,” Horsnell noted in an interview with Health Policy Watch.

Research Benefits

According to the researchers, these findings were very unexpected. “We show that worm infections that never colonise the vagina cause a strong change in the vaginal immunity,” he explained.

Until now, Horsnell maintains, research into STIs has largely neglected the role of worm infections.

“Based on my other work looking at the effect of these infections on tissues not infected, I thought it was time we looked at the effect on STIs,” he said.

Horsnell was hopeful that the discovery would boost efforts to understand how parasitic worm infection indirectly influences the control of sexually transmitted infections.

Intestinal Worm Infections Have Declined, But Still a Concern

Soil-transmitted helminth (worm) infections are among the most common intestinal worm infections worldwide, and affect the poorest and most deprived communities with compromised sanitation, according to Professor Charles Mwandawiro , senior principal research scientist at the Kenya Medical Research Institute (KEMRI).

They are found in all sub-Saharan African countries. Countries with huge worm burdens include Nigeria, Ethiopia, DR Congo and Tanzania.

“These worms are regarded as the main cause of intellectual and physical setbacks, especially in children,” said Mwandawiro, adding that they are associated with reduced cognitive ability, consequently denying children their full potential in life.

Since 2009, KEMRI has been monitoring and evaluating the impact of deworming in 16 countries in Africa, and Mwandawiro maintains that the rates of infections have declined significantly in the last five years from 35% to 12%.

The Institute has been working with the Japan International Cooperation Agency to coordinate de-worming exercises in nine countries in eastern and southern Africa.

“The findings from such activities have achieved wider application on the African continent through the close working relationship with the World Health Organization,” Mwandawiro told Health Policy Watch in an interview.

These intestinal worms include hookworms (Necator americanus and Ancylostoma duodenale), whipworms (trichuris) and roundworms (ascaris ).

Disease resulting from intestinal worms is insidious, says Mwandawiro: “Worms compete with their victims for nutrients and vitamins, thereby causing general ill-health, anaemia and diarrhoea, which can lead to death,” he observes.

Image Credits: UCT.