Virulent isolates kill rabbits. Mosquitoes or fleas act as mechanical vectors. Gelatinous proliferative nodules all over the body but especially the eye-margins and may be fatal within 48 hours.

In the field 5- to 10-year cycles are described in which isolates of changed virulence appear.

Attenuated vaccines are used for farmed/pet rabbits in the UK – do not inject yourself.