By Nicola Kelly

GENEVA, Feb 7 (Thomson Reuters Foundation) - When aid worker Megan Nobert took up a humanitarian posting in war-torn South Sudan, she knew she would be stepping into the firing line.

She had training to prepare her for gunfire, road ambushes and kidnap. But she did not expect the danger to come from within her own ranks.

"It still scares me to know what has been done to my body without my consent," said the 30-year-old Canadian, wrapping her hands around a mug of warm tea.

"I think about the cocktail of drugs put into my drink and I wonder what the long term impact could be."

Nobert, an international human rights lawyer with expertise in sexual and gender-based assault, had moved to Bentiu, South Sudan, in January 2015 to work on a UN peacekeeping base.

It was there, only a month after arriving, that her drink was spiked with a mixture of potentially lethal substances, including morphine and codeine, she said. She was then raped by her colleague, another international member of staff.

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"Drugs are very common in the humanitarian sector," said Nobert, who moved to Geneva a few months ago to campaign on the issue of sexual violence in the aid sector.

"In South Sudan, for example, it's incredibly easy to walk into a local pharmacy, buy a load of drugs and mix them together into a makeshift date rape drug."

According to the latest statistics gathered by Nobert's campaign group Report the Abuse, 54 percent of incidents of sexual assault and abuse against expatriate aid workers are carried out by their international colleagues.

Catherine Plumridge, a security advisor, said living in close quarters and in often unstable environments can make humanitarian workers more vulnerable to sexual attacks.

"In the field, you don't have a choice. Your world is very limited," she said.

"You live together, you work together, you socialize together. In theory, that should create a stronger community but it seems to be the opposite that's happening."

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Cases like Nobert's are not uncommon. The Headington Institute in California estimates at least one to two percent of aid workers have experienced sexual assault during their humanitarian career.

The beating and gang rape of civilians, including aid workers, in a rampage by South Sudanese government troops at the Hotel Terrain in the capital Juba last July, has thrown light on the dangers, but more needs to be done, officials say.

"We keep appealing but unfortunately these incidents continue to happen," said Babar Baloch, Geneva-based spokesman for the U.N. refugee agency UNHCR.

"Aid workers need the guarantee of their safety. We continue to ask for humanitarian law to be respected."

UNDER-REPORTED

Without proper reporting mechanisms, victims of sexual violence are often unwilling to speak out. Many fear retaliation, with figures from Report the Abuse showing that 24 percent of those who report abuse are attacked again.

"If there was even a rumor of a kidnapping or killing, it was reported," Nobert said. "But if there was a rumor of sexual violence, it was hush-hush."

Attitudes to women in some conservative societies where aid workers operate may make reporting sex attacks more difficult.

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"We have had staff report an incident to law enforcement and they have been prosecuted for adultery or extra-marital sex, or they have been raped again by local law enforcement," said Plumridge, the security adviser.

Male aid workers are even more reluctant to report sexual assaults, she said.

"If men don't have outward signs of being beaten or assaulted, often they don't report because they feel it could be perceived they consented to sex rather than were raped."

Aid workers often stay in one place for just a few weeks or months before moving on to the next crisis, perhaps with a new organization.

Short term postings can contribute to the under-reporting of sexual assaults and may allow perpetrators to strike again, said Lucy Heaven Taylor, a humanitarian recruitment expert.

"If a staff member is moved on or leaves swiftly, you don't have the paper trail that allows you to give an accurate reference to the next organization that person works for."

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Before they are sent off on assignment, especially to areas perceived as high risk, U.N. staff undergo training "needed to manage different scenarios that may take place in the field," said Jens Laerke, a spokesman for the U.N. Office for the Coordination of Humanitarian Affairs (UNOCHA) in Geneva.

"Some of that preparation are real-life simulation exercises; others may be web-based," he told the Thomson Reuters Foundation. "They will get a real sense of how to behave in a variety of different environments."

For rape survivors like Megan Nobert, grappling with trauma and adapting to life in a new city, there is a long way to go before the cycle of sexual violence against aid workers is broken.

"There is a part of me that wonders what I should have worn, should I not have been drinking or dancing? But I'll never get that answer and even if I did, it wouldn't change what happened."

(Editing by Ros Russell; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit http://www.trust.org)