• Current Advice on Parasite Control:

    Intestinal Parasites - Coccidia

    Last reviewed and edited Apr 2013

  • Species


    Cystoisospora canis
    Cystoisospora ohioensis
    Cystoisospora neorivolta
    Cystoisospora burrowsi

    Cystoisospora felis
    Cystoisospora rivolta

    *Canine and feline Cystoisospora spp. are sometimes referred to as Isospora.

  • Overview of Life Cycle

    (Link to PDF Life Cycle Image)

    • Nonsporulated (noninfective) oocysts in feces
    • Sporulated (infective) oocysts in the environment
    • Schizonts (asexual stages) in the small and/or large intestine
    • Gametes (sexual stages) in the small and/or large intestine
    • Zoites, which may be sporozoites ormerozoites, are found in extraintestinal tissues (i.e., mesenteric lymph nodes, liver, or spleen) of definitive host as well as in paratenic (transport hosts) such as mice, rats, hamsters, and other vertebrates.
  • Disease

    • Coccidiosis causes diarrhea with weight loss, dehydration, and (rarely) hemorrhage
    • Severely affected animals may present with anorexia, vomiting, and depression. Death is a potential outcome.
    • Dogs and cats may shed oocysts in feces but remain asymptomatic.
    • Intercurrent disease(s), infectious or iatrogenic immunosuppression, or the stresses of environmental changes (i.e., shipment to pet stores or relocation to pet owners) may exacerbate coccidiosis.
  • Prevalence

    • Coccidial infections are common in dogs and cats.
    • Published surveys indicate that coccidia are present in from 3% to 38% of dogs and 3% to 36% of cats in North America. (Link to image of Prevalence Data)
    • Young animals are more likely than older animals to become infected with coccidia.
  • Host Associations and Transmission Between Hosts

    • Canine and feline coccidia are acquired by ingestion of sporulated oocysts from contaminated environments.
    • Coccidiosis is also transmitted to dogs and cats by ingestion of transport hosts (predation) containing extraintestinal stages.
    • Cystoisospora spp. are rigidly host-specific. Canine coccidia will not infect felines leading to passage of oocysts in feces. The same is true for feline coccidia.
    • Canine and feline Cystoisospora spp. are not known to be of zoonotic significance.
  • Prepatent Period and Environmental Factors

    • Click here to see details of prepatent and patent periods.
    • Development of oocysts to infective sporulated oocysts (sporulation) does not occur above 40° C or below 20° C.
    • Sporulation occurs rapidly (<16 hours) at temperatures between 30° C and 37° C.
    • Sporulated oocysts are resistant to adverse environmental conditions and can survive as long as one year in moist, protected environments if they are not exposed to freezing or extremely high temperatures.
  • Site of Infection and Pathogenesis

    • Developmental stages reside in either cells lining the intestinal villus (enterocytes) or cells within the lamina propria of the villus.
    • Maturation and emergence of asexual and sexual stages from infected cells causes cell lysis. This damage can be especially severe when caused by species that develop within cells in the lamina propria.
    • Zoites also are found in extraintestinal tissues (i.e., mesenteric lymph nodes, liver, or spleen) of definitive or paratenic hosts. These resting or latent stages are not thought to cause clinical disease.
  • Diagnosis

    • Diagnosis of canine and feline coccidiosis is based on signalment, history, and clinical signs, and the structure of oocysts present in feces (Click here to see Diagnosis Images)
    • Fecal examination should be performed using centrifugal flotation and an adequate amount of feces. (Click here to see Fecal Examination Procedures.)
    • Several genera of coccidia-like organisms may be present in canine and feline feces. It is important to differentiate them on the basis of size, state of sporulation, and presence/absence of oocysts or sporocysts.
    • The presence of oocysts in feces is not, in itself, adequate proof that coccidiosis is the cause of accompanying clinical signs.
    • Oocysts of Eimeria spp. are sometimes observed in canine and feline fecal samples. Dogs and cats are not hosts to Eimeria spp.; therefore these oocysts are referred to as pseudoparasites. These oocysts never reach the two-celled stage typical of Cystoisospora spp. A few two-celled Cystoisospora oocysts are often observed, even in fresh fecal samples. Additionally, oocysts of many Eimeria spp. often have oocyst wall ornamentations called micropyles or micropyle caps.
  • Treatment

    • Sulfadimethoxine is the only drug that is label approved for treatment of enteritis associated with coccidiosis.
    • Numerous additional drugs and drug combinations have been used with some success. (See below)
    • Among the newer drugs, ponazuril appears to be effective, according to published research and user testimonials.


    Treatment of Coccidiosis of Dogs and Cats

    Sulfadimethoxine 50-60 mg/kg daily for 5-20 days (D.C)
    Sulfaguanidine 150 or 200 mg/kg daily for 6 days (D,C); 100-200 mg/kg every 8 hours for 5 days (D,C)
    Furazolidone 8-20 mg/kg once or twice daily for 5 days (D,C)
    Trimethoprim/Sulfonamide Dose/length depends on sulfa; 30-60 mg/kg trimethoprim daily for 6 days in animals ≥ 4 kg; or 15-30 mg/kg trimethoprim for 6 days in animals ≤ 4 kg
    Sulfadimethoxine/Ormetoprim 55 mg/kg of sulfadimethoxine and 11 mg/kg of ormetaprim for 7-23 days (D)
    Quinacrine 10 mg/kg daily for 5 days (C)
    Amprolium 300 to 400 mg (total) for 5 days (D); 110-200 mg (total) daily for 7-12 days (D); 60-100 mg/kg (total) daily for 7 days (C); 1.5 tbsp (23 cc)/gal (sole water source) not to exceed 10 days (D)
    Amprolium/Sulfadimethoxine 150 mg/kg of amprolium and 25 mg/kg of sulfadimethoxine for 14 days (D)
    Toltrazuril 10-30 mg/kg daily for 1-3 days (D)
    Diclazuril 25 mg/kg daily for 1 day (C)
    Ponazuril 20 mg/kg daily for 1-3 days (D,C)


  • Control and Prevention

    • In addition to treatment, appropriate sanitation is helpful in preventing spread of coccidiosis in kennels and catteries.
    • Oocysts sporulate quickly once in the environment; daily removal of feces can aid in the prevention of coccidiosis.
    • After they are infective, oocysts are resistant to most commonly used disinfectants. Infective oocysts can survive for many months in the environment.
    • Disinfectants containing high concentrations of ammonia can destroy oocysts, but harmful odors and the necessity of removing animals from runs or cages during treatment limit their use.
    • Steam and pressure washing may help to dislodge feces from kennel and cage surfaces.
    • Painting or sealing kennel floors will help prevent adherence of feces to these surfaces and will aid in cleaning.
    • Treatment of all in-contact animals, including bitches and queens, may also be beneficial in controlling coccidiosis in kennels and catteries.
    • Prevention of predation should be emphasized to prevent infection via paratenic hosts.
  • Public Health Considerations

    • Because humans are not susceptible to Cystoisospora infections in dogs and cats, canine or feline coccidia are not considered zoonotic agents.
    • Oocysts of Topxoplasma gondii, which is zoonotic, are passed in feline feces, but are much smaller than those of Cystoisospora spp. (click here to see Diagnosis Images)
  • Selected References

    • Dubey JP, Lindsay DS, Lappin MR. 2009. Toxoplasmosis and other intestinal coccidial infections in cats and dogs. Vet Clin Small Anim. 39:1009-1034.
    • Gates MC, Nolan TJ. 2009. Endoparasite prevalence and recurrence across different age groups of dogs and cats. Veterinary Parasitology. 166: 153-158.
    • Lappin MR. 2005. Enteric protozoal diseases. Vet Clin Small Anim. 35: 81-88.