Doctors have said the worms are making it more difficult to treat the soldier, who was shot five times during his escape
Doctors have said a North Korean soldier who defected to the South earlier this week is 'riddled with parasites', providing a rare insight into people's health in the secretive state.
The North Korean soldier made the dangerous crossing between the two countries on Monday, and was immediately taken to hospital after being shot five times during his escape.
He is still said to be in a critical condition.
In comments to journalists quoted by the AFP news agency, doctor Lee Cook-Jong said: "Vital signs including his pulse are returning to stability.
"We're paying close attention to prevent possible complications".
However, he also stressed that parasites had made treatment more difficult.
He noted that "an enormous number of parasites" such as roundworms had been found in the soldier's small intestine - including one worm that was 27 cm long.
Dr Lee added: "I've never seen anything like this in my 20 years as a physician."
Parasites can enter the body in a number of ways - such as insect bites - but it is believed that many people in North Korea are likely to be infected as a result of contaminated food.
BBC reports that human faeces are still used as fertilisers in North Korea.
According to the broadcaster, "if these faeces are untreated and fertilise vegetables that are later eaten uncooked, the parasites get into the mouth and then the intestines of the person."
The charity Médecins Sans Frontières says North Korean health facilities are not regularly maintained, and the country lacks medical equipment and supplies
Officials have said that the defecting soldier made the crossing at the Panmunjom peace village at the Joint Security Area - the heavily guarded section of the Demilitarised Zone (DMZ) where troops from the North & South face each other.
The defected soldier approached the border in a vehicle, but was forced to complete the perilous crossing on foot after a wheel came loose.
North Korean soldiers are then believed to have fired around 40 rounds in a bid to stop him.
He is said to have been hit five times - twice in the shoulder, twice in the abdomen and once in his thigh.
South Korean soldiers crawled towards the soldier after the incident, and managed to successfully drag him over to their side of the border.