DX was a prion disease developed from a bad batch of ground-up sheep that was fed to InGen’s carnivorous dinosaurs and featured in The Lost World. By the time Ian Malcolm, Eddie Carr and Jack Thorne had arrived at Isla Sorna, the disease had infected many of the dinosaurs and disrupted InGen’s progress in cloning the animals. It was most easily noticeable amongst the Procompsognathus population, causing them to act in a similar way to a rabid animal. Because of the disease, the animals had to be released from the laboratories into the wilds of Isla Sorna until they reached a juvenile stage and could be moved to the park on Isla Nublar.
The protagonists first discovered that a phenomena known as DX was disrupting dinosaur production while they were searching for Richard Levine in the laboratory. They came across several emails* that had been printed on paper, one of which identified DX. It read:
INGEN PRODUCTION UPDATE 12/18/88
From: H. Wu
To: All Personnel
Subject: DX: TAG AND RELEASE
Live births will be fitted with the new Grumbach field tags at the earliest viable interval. Formula or other feeding within the laboratory confines will no longer be done. The release program is now fully operational and tracking networks are activated to monitor.
This indicated that, due to DX , dinosaurs were being left in the wild, until they were old enough for Jurassic Park. Ian Malcolm and Sarah Harding were the first of the team to figure out what was happening; InGen didn’t know what to feed the dinosaurs when they were hatchlings, so they gave the carnivores sheep protein extract. Zoos do not use sheep extract, as it is very easily infected with diseases. DX was caused by prions, the simplest disease-causing entities known. They are so basic that they cannot invade a body, they have to be digested. When digested by certain animals they cause a disease to occur (mad-cow disease, sheep get scrapie, kuru in humans) and dinosaurs develop DX. InGen had almost cured Isla Sorna of it, but it began to spread between dinosaurs when the procomsognathids began eating the feces of infected animals, causing them to become infected with the disease. They were in turn eaten by Velociraptors, which then passed it on to herbivores that escaped after being bitten, hence why animals on Isla Sorna died relatively young. DX seems to have very little effect on humans and takes at least a week to develop in us.
*The Lost World: Jurassic Park – Page 150.