A mysterious “mad snake disease” that causes pythons to tie themselves up in knots may be caused by a rodent virus, scientists believe. The fatal condition, called Inclusion Body Disease (IBD), strikes captive pythons and boa constrictors. Snakes with the disease start to display strange behavioural traits, such as “stargazing” – staring upwards for long periods of time. Other symptoms include appearing drunk and getting into a legless tangle. “They tie themselves in a knot and they can’t get out of it,” said US expert Professor Michael Buchmeier, from the University of California at Irvine. IBD gets its name from inclusions, or pockets of foreign material, found in the cells of affected animals. Although the disease is known to be highly infectious, its cause has been a mystery until now. A team led by Prof Buchmeier investigated an outbreak of IBD among snakes at the Steinhart Aquarium in San Francisco.