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Parasitic worms found in a North Korean soldier, critically injured during a desperate defection, highlight nutrition and hygiene problems have plagued the isolated country for decades.

At a briefing Wednesday, lead surgeon Lee Cook-jong displayed photos showing dozens of flesh-colored parasites — including one 10.6 inches long — removed from the wounded soldier's digestive tract during a series of surgeries to save his life.

"In my over 20 year-long career as a surgeon, I have only seen something like this in a textbook," Lee said.

South Korean doctor Lee Cook-Jong speaks about the condition of the defecting soldier. STR / AFP - Getty Images

The parasites, along with kernels of corn in his stomach, may confirm what many experts and previous defectors have described about the food and hygiene situation for many North Koreans.

"Although we do not have solid figures showing health conditions of North Korea, medical experts assume that parasite infection problems and serious health issues have been prevalent in the country," said Choi Min-Ho, a professor at Seoul National University College of Medicine who specializes in parasites.

The soldier's condition was "not surprising at all considering the north’s hygiene and parasite problems," he said.

The soldier was flown by helicopter to hospital Monday after his dramatic escape to South Korea in a hail of bullets fired by North Korean soldiers.

He is believed to be an army staff sergeant in his mid-20s who was stationed in the Joint Security Area in the United Nations truce village of Panmunjom, according to Kim Byung-kee, a lawmaker of South Korea's ruling party, briefed by the National Intelligence Service.

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North Korea has not commented on the defection.

While the contents of the soldier’s stomach don’t necessarily reflect the population as a whole, his status as a soldier — with an elite assignment — suggest he would at least be as well nourished as an average North Korean.

He was shot in his buttocks, armpit, back shoulder and knee among other wounds, according to the hospital where the soldier is being treated.

Parasitic worms were also once common in South Korea 40 to 50 years ago, Lee noted during his briefing, but have all but disappeared as economic conditions greatly improved.

Other doctors have also described removing various types of worms and parasites from North Korean defectors.

Their continued prevalence north of the heavily fortified border that divides the two Koreas could be in part tied to the use of human excrement, often called "night soil."

"Chemical fertilizer was supplied by the state until the 1970s, but from the early 1980s, production started to decrease," said Lee Min-bok, a North Korean agriculture expert who defected to South Korea in 1995. "By the 1990s, the state could not supply it anymore, so farmers started to use a lot of night soil instead."

In 2014, supreme leader Kim Jong Un personally urged farmers to use human faeces, along with animal waste and organic compost, to fertilize their fields.

A lack of livestock, however, made it difficult to find animal waste, said Lee, the agriculture expert.

Even harder to overcome, he said, is the view of night soil as the "best fertilizer in North Korea," despite the risk of worms and parasites.

"Vegetables grown in it are considered more delicious than others," Lee said.

The medical briefing described the wounded soldier as being 5 feet 5 inches and 132 pounds with his stomach containing corn. It's a staple grain that more North Koreans may be relying on in the wake of what the United Nations has called the worst drought since 2001.

Imported corn, which is less preferred but cheaper to obtain than rice, has tended to increase in years when North Koreans are more worried about their seasonal harvests.

Between January and September this year, China exported nearly 49,000 tonnes of corn to North Korea, compared to only 3,125 tonnes in all of 2016, according to data released by Beijing.

Despite the drought and international sanctions over Pyongyang's nuclear program, the cost of corn and rice has remained relatively stable, according to a Reuters analysis of market data collected by the defector-run Daily NK website.

Since the 1990s, when government rations failed to prevent a famine hitting the country, North Koreans have gradually turned to markets and other private means to feed themselves.

The World Food Programme says a quarter of North Korean children 6-59 months old, who attend nurseries that the organization assists, suffer from chronic malnutrition.