Coccidia
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Coccidia are microscopic, spore-forming, single-celled parasites belonging to the apicomplexan class Conoidasida.<ref name=UTS>The Taxonomicon & Systema Naturae (Website database). Taxon: Genus Cryptosporidium. Universal Taxonomic Services, Amsterdam, The Netherlands (2000).</ref> Coccidian parasites infect the intestinal tracts of animals<ref name=iziko>Biodiversity explorer: Apicomplexa (apicomplexans, sporozoans). Iziko Museums of Cape Town.</ref>, and are the largest group of apicomplexan protozoa.
Coccidia are obligate, intracellular parasites, which means that they must live and reproduce within an animal cell.
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[edit] Coccidiosis (disease caused by coccidian infection)
Coccidiosis is a parasitic disease of the intestinal tract of animals, caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces, or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic; however, young or immuno-compromised animals may suffer severe symptoms, including death.
While coccidian organisms can infect a wide variety of animals, including humans and livestock, they are usually species-specific. One well-known exception is toxoplasmosis, caused by Toxoplasma gondii.
[edit] Coccidia in dogs
People often first encounter coccidia when they acquire a young puppy who is infected. The infectious organisms are canine-specific and are not contagious to humans (compare to zoonotic diseases).
Young puppies are frequently infected with coccidia and often develop active Coccidiosis -- even puppies obtained from diligent professional breeders. Infected puppies almost always have received the parasite from their mother's feces. Typically, healthy adult animals shedding the parasite's oocysts in their feces will be asymptomatic due to their developed immune systems. However, undeveloped immune systems make puppies more susceptible. Further, stressors such as new owners, travel, weather changes, and unsanitary conditions are believed to activate infections in susceptible animals.
Symptoms in young dogs are universal: at some point around 2-3 months of age, an infected dog develops persistently loose stools. This diarrhea procedes to stool containing liquid, thick mucus, and light colored fecal matter. As the infection progresses, spots of blood may become apparent in the stool, and sudden bowel movements may surprise both dog and owner alike. Coccidia infection is so common that any pup under 4 months old with these symptoms can almost surely be assumed to have coccidiosis.
Fortunately, the treatment is inexpensive, extremely effective, and routine. A veterinarian can easily diagnose the disease through low-powered microscopic examination of an affected dog's feces, which usually will be replete with oocysts. One of many easily administered and inexpensive drugs will be prescribed, and, in the course of just a few days, an infection will be eliminated or perhaps reduced to such a level that the dog's immune system can make its own progress against the infection. Even when an infection has progressed sufficiently that blood is present in feces, permanent damage to the gastrointestinal system is rare, and the dog will most likely make a complete recovery without long-lasting negative effects.
If one dog of a litter has coccidiosis, then most certainly all dogs at a breeder's kennels have active coccidia infections. Breeders should be notified if a newly-acquired pup is discovered to be infected with coccidia. Breeders can take steps to eradicate the organism from their kennels, including applying medications in bulk to an entire facility.
[edit] Genera and species that cause coccidiosis
- Genus Isospora is the most common cause of intestinal coccidiosis in dogs and cats and is usually what is meant by coccidiosis. Species of Isospora are species specific, meaning they only infects one type of species. Species that infect dogs include I. canis, I. ohioensis, I. burrowsi, and I. neorivolta. Species that infect cats include I. felis and I. rivolta. The most common symptom is diarrhea. Sulfonamides are the most common treatment. <ref name=Ettinger_1995>Ettinger, Stephen J.;Feldman, Edward C. (1995). Textbook of Veterinary Internal Medicine, 4th ed., W.B. Saunders Company. ISBN 0-7216-6795-3.</ref>
- Genus Cryptosporidium contains two species known to cause cryptosporidiosis, C. parvum and C. muris. Cattle are most commonly affected by Cryptosporidium, and their feces are a common source of infection for other mammals including humans. Infection occurs most commonly in individuals that are immunocompromised, e.g. dogs with canine distemper, cats with feline leukemia virus infection, and humans with AIDS. Very young puppies and kittens can also become infected with Cryptosporidium, but the infection is usually eliminated without treatment.<ref name=Ettinger_1995/>
- Genus Hammondia is transmitted by ingestion of cysts found in the tissue of grazing animals and rodents. Dogs and cats are the definitive hosts, with the species H. heydorni infecting dogs and the species H. hammondi and H. pardalis infecting cats. Hammondia usually does not cause disease.<ref name=Ettinger_1995/>
- Genus Besnoitia infect cats that ingest cysts found in the tissue of rodents and opossum, but usually does not cause disease.<ref name=Ettinger_1995/>
- Genus Sarcocystis infect carnivores that ingest cysts from various intermediate hosts. It is possible for Sarcocystis to cause disease in dogs and cats.<ref name=Ettinger_1995/>
- Genus Toxoplasma has one important species, Toxoplasma gondii. Cats are the definitive host, but all mammals and some fish, reptiles, and amphibians can be intermediate hosts. Therefore, only cat feces will hold infective oocysts, but infection through ingestion of cysts can occur with the tissue of any intermediate host. Toxoplasmosis occurs in humans in mainly immunocompromised individuals, but the fetus is at risk in pregnant women who ingest either contaminated meat or cat feces. Symptoms in cats include fever, weight loss, diarrhea, vomiting, uveitis, and central nervous system signs. Disease in dogs includes a rapidly progressive form seen in dogs also infected with distemper, and a neurological form causing paralysis, tremors, and seizures. Dogs and cats are usually treated with clindamycin.<ref name=Ettinger_1995/>
- Genus Neospora has one important species, Neospora caninum, that affects dogs in a manner similar to toxoplasmosis. Neosporosis is difficult to treat.<ref name=Ettinger_1995/>
- Genus Hepatozoon contains one species that causes hepatozoonosis in dogs and cats, Hepatozoon canis. Animals become infected by ingesting an infected Rhipicephalus sanguineus, also known as the brown dog tick. Symptoms include fever, weight loss, and pain of the spine and limbs.
The most common medications used to treat coccidian infections are in the sulphonamide family. Although unusual, sulphonamides can damage the tear glands in some dogs, causing keratoconjunctivitis sicca, or "dry eye", which may have a life-long impact. Some veterinarians recommend measuring tear production prior to sulphonamide administration, and at various intervals after administration. Other veterinarians will simply avoid using sulphonamides, instead choosing another product effective against coccidia.
Left untreated, the infection may clear of its own accord, or in some cases may continue to ravage an animal and cause permanent damage or, occasionally, death.
[edit] References
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[edit] See also
[edit] External links
- Mar Vista Animal Medical Center.
- The Coccidia of the World, Donald W. Duszynski, Steve J. Upton, Lee Couch, Feb. 21, 2004.
- Life Cycle EIMERIA, Andreas Weck-Heimann, 1996-2005
- FarmingUK, Information about Coccidiosis
- Poultry Youth Association, Article on Coccidiosis in the Poultry Industry
- Lillehoj, Hyun S. (October 1996). "Two Strategies for Protecting Poultry From Coccidia". Agricultural Research magazine (October 1996). Describes using live-parasite vaccine versus a monoclonal antibody to block the sporozoite from invading a host's cell.de:Kokzidien
