Coccidiosis, also called “bloody diarrhea” (eww!) is one of the few poultry diseases that give most chicken owners trouble, at least once in a while. It’s caused by coccidia, protozoan parasites with a complex life cycle: part of their life is spent inside the chicken and part of it is spent outside. The infographic shows the cycle and the danger points.
Oodles of Oocysts
In short, coccidia “oocysts” (think of them as eggs) are present in the droppings of infected chickens, and these droppings can infect other chickens, and also reinfect the same chicken. This last point is important, since coccidia can’t reproduce indefinitely inside the chicken: if the chicken stops ingesting oocysts, the infection stops.
This means that coccidiosis can be controlled by preventing chickens from coming into contact with their manure. Chicken pens with wire floors are the most common method.
Keeping manure out of feeders and waterers is also important. Properly designed and positioned feeders and waterers stay clean by design, so they don’t have to be cleaned by hand so often.
Sporulate or Bust
But your chickens can’t get coccidiosis from a fresh oocyst lurking in the droppings. The oocyst still in a non-infectious stage of the life cycle. It takes 2-4 days for the oocyst to advance to the next stage, the one that makes it dangerous. This is called “sporulation.” If eaten by a chicken, a single sporulated oocyst can multiply into millions of next-generation oocysts inside that one chicken.
This 2-4 day grace period allows additional methods of coccidiosis control, based on separating the chickens from their manure before the oocysts can sporulate. The most common methods are to remove the litter in the chicken house daily and to use outdoor pasture pens: floorless pens that are moved to a new patch of ground daily.
In addition, the oocysts do poorly on dry floors, so coccidiosis is more of a problem in damp houses than dry ones.
Finally, the microscopic ecosystem that develops in deep litter (litter that’s been in use for more than six months or so, and is at least six inches deep) seems to treat oocysts as a yummy snack, so chickens raised on old deep litter have less coccidiosis than ones on new or shallow litter. (Personally, I haven’t found this protection to be adequate.)
Other Control Methods
Medicated chick starter contains an ingredient that suppresses coccidiosis by killing coccidia or interfering with their reproduction inside the chicken. Such medications can also be added to the drinking water.
The old “milk flush” method deserves a mention here because it doesn’t work. At all.
Doing nothing and letting the disease run its course will result in some chickens becoming stunted or thin, and mortality can be as high as 30% before the disease is overcome, though many of the survivors suffer permanent internal damage to their digestive systems.
How Do Coccidia Reach My Farm?
In my experience, coccidiosis is hard to avoid because the parasite appears like magic, no matter what you do.
About the Infographic
I made the infographic by adding some color and a title to the “Coccidiosis Life Cycle” diagram in Leslie E. Card’s Poultry Production: The Practice and Science of Chickens. This is a very thorough book that no serious poultrykeeper should be without. Unlike more recent books, which tend to be either aimed at factory farming or casual backyarding, books published through the Sixties had the small commercial producers and serious hobbyists in mind. Poultry Production is a gold mine of information and techniques that are still valid for us because the book is an older work. Published in 1961, it dates from a time when all the techniques in use today had already been developed, but when small flocks were still common. This 414-page book was used both as a college textbook and as a reference book for ordinary farmers. I can’t recommend it too highly.