Researchers have found that a little-studied variety of threadworm – strongyloides stercoralis – previously thought to be relatively benign is associated with “significant morbidity” in rural Cambodia.

Peter Odermatt, a professor at Basel University in Switzerland who headed the team, said the researchers had been studying the parasitic worms in Cambodia since 2008 and found they are “highly prevalent”.

“About 25 to 50 percent of the rural population is infected,” he said.

Strongyloides stercoralis is a soil-transmitted worm that can replicate within its host, leading to long-lasting and potentially fatal infections, the study says.

Chronic strongyloidiasis stercoralis infection appears to cause both acute gastrointestinal symptoms and urticaria, or hives, says the study, which was published last week in the journal PLOS Neglected Tropical Diseases. The worm also causes subtle long-term health effects through its association with malnutrition.

A total of 3,377 study participants, both infected and noninfected, in Preah Vihear province completed an interview and clinical assessment. Researchers assessed how symptoms improved with an oral dose of a medication called ivermectin.

Odermatt said researchers were able to show that regular treatment with ivermectin can reduce the worm load in the population.

“The effect of the treatment is particularly important if it is combined with water and sanitation interventions and health education,” he said. But “an important drawback” for wide distribution is the high cost of medicine.

Donation programmes exist for other worm treatments, but not for ivermectin, he said. Odermatt suggested the scientific community and health officials are not “convinced” about the toll that the infection takes.

“With our publication, we could show that significant morbidity is associated with threadworm infection,” he said.

Cambodia has done a good job in terms of controlling worm infections, he said. However, the researchers hope that the study will encourage the Ministry of Health and the World Health Organization “to push for ivermectin treatment” for infected, rural populations.

Dr Virak Khieu, head of the Cambodian National Helminth Control programme, said officials were trying to address the matter, but that policy comments were outside his scope.

Vicky Houssiere, communications officer with WHO Cambodia, said the WHO has assisted the government in drafting a plan that includes a control strategy for the worm infections.