That bunny ain't dropping Easter eggs

Years ago, pregnant with my first child and having no veterinary training yet, I acquired a young Nubian goat kid with diarrhea. Fecal testing revealed a protozoan parasite referred to generically as coccidia. A cautious expectant mother, I asked my physician if exposure to goat coccidia was harmful to my unborn baby. When he reported back that goat coccidia (Eimeria spp.) are "host specific" -- meaning goat Eimeria are contagious only to other goats -- I was very relieved.


Flash forward a decade and I find myself, now an animal doctor, doling out this same information to dog owners on a regular basis. Finding microscopic coccidia eggs on an annual fecal float test is not uncommon. Dogs may pass Isospora or Eimeria eggs in their stool, but as with goats these coccidia parasites are "host specific." As I explain this to horrified pet owners, they are relieved to hear it is not contagious to them or their children.

A small sampling of the oodles of eggs
-- coccidia, not Easter -- being passed by two
sick bunnies I saw this month. 

Identifying the presence of coccidia is easy. Now here's where it gets tricky. Remember that coccidia are "host specific." If a dog tests positive for an Isospora-type coccidia it may require treatment because Isospora is a dog coccidia. But if an Eimeria-type coccidia is seen, the dog is simply pooping out the coccidia that a rabbit once pooped out. Quickly differentiating between Isospora from Eimeria based on subtle differences in size or ornamentation takes practice and experience. Nevertheless, seeing as nibbling rabbit poop is a pretty common canine past time, chances are pretty good that many dogs are pooping out a non-canine coccidia.*

Many animals host coccidia without any outward signs of illness. In fact, sickness generally occurs only in very young animals during times of stress. As in my goat kid, coccidiosis may cause severe diarrhea. My yellow Labrador developed screaming diarrhea a few days after we brought him home as a puppy thanks not only to Isospora spp. but also to the stress of leaving his litter. Some of my canine patients--puppy or adult--that test positive for coccidia have unexplained scooting or butt licking without abnormal stools. A short course of treatment for coccidia often relieves all these symptoms.

I recently examined two very young bunnies with diarrhea and lack of appetite. These baby bunnies had been turning up their twitching little noses at hay and pellets for several days, eating nothing but carrots (a treat, not a balanced meal). The day I examined them they had been passing liquid orange stool for several hours. Not having had an occasion to test a pet rabbit's stool before, I was unsure of what I would find. Imagine my surprise when I focused my microscope on the fecal float slide to find hundreds of oval eggs. Coccidia! Eimeria-type no doubt. Treatment with anti-coccidia medication--a teeny tiny portion of the average dog dose--was started immediately, and the owner decided to provide additional nursing care at home.

What fascinates me about this case is not so much identifying rabbit coccidia -- as I explained, we veterinarians see it all the time as an incidental finding on canine fecal floats. It's just that I had never seen so much of it in one place. And never had I paused to think about what the rabbit coccidia might do to the rabbit! The story of these two very sick baby bunnies overwhelmed by coccidia has given this parasite a face and personal meaning to me.


* Cats can be infected with or shed coccidia in their stool as well including various species of Isospora or Eimeria which are not contagious to people.