Almost everyone with a pet rabbit has heard about Encephalitozoon cuniculi as a cause of head tilt or cataracts, but not many rabbit owners understand much else about the disease. Encephalitozoon cuniculi, often abbreviated as E. cuniculi or simply EC, is a eukaryotic parasite of mammals, meaning it has a distinct nucleus and other internal structures (organelles) that make it more complex than a bacterium. EC is a microsporidian, a type of organism more closely related to fungi than to protozoans or animals. A distinctive characteristic is that EC lacks functional mitochondria, the energy engine of a cell, because it lives within animal cells and gets its energy from its host cell’s mitochondria.
EC can cause significant disease in some rabbits, but they are not the only mammals that can be infected. Otherwise healthy guinea pigs and mice are important reservoirs of EC and can spread it to rabbits. There are at least three different strains of EC, each of which seems to prefer a different host. EC infection has been documented in many other mammals across the world, including wild mammals, cats, horses and people, but appears to cause severe illness only in immunocompromised hosts.
EC spreads by its infective spores contaminating the environment. The spores are shed in urine and occasionally feces, and from there are easily spread throughout the rabbit’s home environment. EC spores can stay infective for months in cool, humid environments and have been known to survive for at least a month under dry conditions at comfortable room temperatures. Rabbits may acquire the disease from ingesting the spores, inhaling the spores or spores settling on their eyes, and infected does can pass it on to their unborn babies.
For the full article, pick up the 2012 issue of Rabbits USA or click here to buy the issue.