Coccidiosis is a contagious disease of goats, especially young kids, throughout the world. The disease is caused by one or more of approximately 12 different species of protozoa, called Eimeria, which parasitize and destroy cells lining the intestinal tract of the goat. Sheep are also very susceptible to coccidiosis, but even though the sheep forms may share the same names with goat coccidia, many parasitologists believe that the disease cannot be spread from goats to sheep or from sheep to goats.
An infected goat sheds thousands of microscopic coccidial oocysts in its feces every day. When first passed, the oocysts are harmless to another goat. However, under favorable conditions of warmth and mositure, each oocyst matures (sporulates) in 1 to 3 days to form 8 infective sporozoites. If a young kid swallows the sporulated oocyst, the sporozoites are released and rapidly penetrate the intestinal cells. From here on, the life cycle gets very complicated. The coccidia pass through several periods of multiplication during which large schizonts are formed. The intestinal cell of the goat is destroyed and thousands of small forms called merozoites break out and invade other intestinal cells. Eventually sexual stages are reached and new oocysts are produced. The entire life cycle from oocyst to new oocyst takes 2-3 weeks.
If a young kid is suddenly exposed to many sporulated oocysts, it may become severely ill 1-2 weeks later. It will be off feed, listless, and weak. It may show abdominal pain by crying or getting up again as soon as it lies down. At first, the kid might have a fever, but later the body temperature is normal or even below normal. Diarrhea begins pastey, then becomes watery. The kid may dehydrate rapidly. Contrary to various reports written by people more accustomed to calves than kids, the diarrhea is only rarely bloody. Neither is straining common. Signs often show 2-3 weeks after the kids are weaned, because the lactic acid produced by the digestion of milk helps to inhibit occidia in the nursing kid.
Young kids may be killed quickly by a severe attack of coccidiosis. Others - those initially stronger or less heavily infected - will develop a chronic disease characterized by intermittent diarrhea and poor growth. Tails and hocks are dirty. The kid with chronic coccidiosis cannot digest its feed properly because the intestines have been severely damaged. As a consequence, such a kid will be a potbellied poor-doer for months afterwards. Frequently, such a stunted kid will be too small to breed it's first winter.
Even though coccidiosis is typically a disease of the young growing kid, most adults are mildly infected and continuously shed oocysts which serve to infect young kids. Occasionally an adult goat shows temporary diarrhea when stressed or exposed to a new species of coccidia. This is especially common after the doe has been boarded on another farm for breeding.
Diagnosis of coccidiosis can be based on clinical signs or microscopic fecal exams. Coccidiosis is so common that it should be suspected whenever kids older than about 2 weeks of age are scouring. Sudden dietary changes can also cause diarrhea, but these make the kid more susceptible to coccidiosis. Thus diarrhea that begins with the consumption of too much milk, grain, or lush grass may drag on for days because of coccidiosis. Older kids and adults with diarrhea may have worms rather than coccidiosis, or they may have both problems together. Oocysts can be identified if the feces are mixed with a concentrated sugar solution. The oocysts float to the top, along with larger worm eggs. They are collected and examined with a microscope.
Oocysts may be shed in the feces as early as 10 days after a kid is infected, but often the first attack of diarrhea occurs before oocysts are available to be identified. In these cases, the trained technician can do a direct fecal smear to look for smaller merozoites, which do not float in the sugar solution.
If a kid dies of coccidiosis, post-mortem examination will quickly give the diagnosis. The small intestine will have many irregular raised white areas, often about 1/8 to 1/4 inch in diameter. A smear taken from these white spots will show many coccidial forms if examined under a microscope.