LONDON (Reuters) - Two of every five South African students say they have been raped, according to a study published on Tuesday suggesting sexual abuse of boys is endemic in the country’s schools.

The survey published in BioMed Central’s International Journal for Equity in Health showed that adult women most frequently assaulted the boys, followed closely by other schoolchildren.

“This study uncovers endemic sexual abuse of male children that was suspected but hitherto only poorly documented,” Neil Andersson and Ari Ho-Foster of The Centre for Tropical Disease Research in Johannesburg wrote.

The findings underscore the need to raise awareness about the rape of male children and they urged further efforts to prevent sexual violence in South Africa, the researchers said.

This is especially important because South Africa already has one of the highest rape rates in the world, and other studies have shown that people who sexually abuse children were often the target of such violence when young, they added.

Another problem is that the prevalence of rape is hampering efforts to combat AIDS in a country at the epicenter of the global pandemic.

“There is increasing recognition of links between sexual abuse and high-risk attitudes to sexual violence and HIV risk,” the researchers wrote. “Sexually abused children are also more likely to engage in HIV high-risk behavior.”

The survey carried out in 1,200 schools across the country asked 127,000 boys aged between 10 and 19 if they had ever been sexually abused and, if so, by whom.

Forty-four percent of the 18-year-olds said they had been forced to have sex in their lives and half reported consensual sex.

About a third said they had been abused by males, 41 percent by females and 27 percent said they had been raped by both males and females. The study did not look at the number of girls who were raped.

Abuse by fellow males was more common in rural areas while attacks by women happened mainly in cities, the study found. There was also a big disparity between provinces with Limpopo -- among the poorest -- showing the highest abuse rates and Western Cape the lowest.

This type of study based entirely on the response of participants has limitations because there are no ways to verify whether people exaggerate or withhold information, the researchers acknowledged.

Even so, the researchers say they constructed their anonymous survey to cut down on these pitfalls and the findings may actually underestimate the sexual violence.

“We think it is an underestimate for boys because there is no merit for them to report that they have been sexually abused,” Andersson said in a telephone interview.