Enteric coccidiosis, the infestation of the small intestine by the Eimeria spp. parasites, is a common cause of diarrhoea and even death in rabbits.
There are loads of species of Eimeria. If they cause disease they shrink the villi (finger-like projections in the intestine) by destroying the enterocytes (cells that line the villi). This leads to poor absorption from the gut lumen, and also leakage of fluid into the lumen. This results in diarrhoea. Dehydration and electrolyte loss can prove fatal to the rabbit.
The immune system tries to get rid of the parasite. Below we managed to capture the moment a team of macrophages have fused to form a giant cell, which is in the process of ingesting (by phagocytosis) a parasite oocyst.