Species*

Canine
Isospora canis
Isospora ohioensis
Isospora neorivolta
Isospora burrowsi

Feline
Isospora felis
Isospora rivolta

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

Overview of Life Cycle

• Canine and feline coccidia undergo a complex developmental cycle at specific locations in their respective hosts. The life cycle of I. felis in the attached PDF serves as an example.

Stages

(Link to PDF Life Cycle Images)

• 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 (sporozoites/merozoites?) in extraintestinal tissues (i.e., mesenteric lymph nodes, liver or spleen
• Zoites (sporozoites/merozoites?) in paratenic (transport hosts) such as mice, rats, hamsters, dogs, cats, opossums, cattle (others?)

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 PDF Prevalence Data 88K)
• 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.
• Isospora 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 Isospora spp. are not known to be of zoonotic significance.

Prepatent Period and Environmental Factors

• See attached PDF file (95K) for 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 (sporozoites/merozoites?) 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 (Link to PDF Diagnosis Images 87K)
• Fecal examination should be performed using centrifugal flotation and an adequate amount of feces.
• 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 toEimeria spp.; therefore these oocysts are referred to as pseudoparasites. These oocysts never reach the two-celled stage typical of Isospora spp. A few two-celled Isospora 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. (Link to PDF Treatment Images 55K)
• Among the newer drugs, ponazuril appears to be effective, according to published research and use testimonials.

Control and Prevention

• In addition to treatment, appropriate sanitation in addition to treatment is helpful in the prevention of spread of coccidiosis in kennels and catteries.
• Oocysts sporulate quickly once in the environment; therefore 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 their 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 Isospora infections in dogs and cats, canine or feline coccidia are not considered zoonotic agents.
• It should be kept in mind that Toxoplasma gondii is a zoonotic agent. Oocysts are passaged in feline feces, but are much smaller than those of Isospora spp (Link to PDF Diagnosis Images 87K)

This information was made available by The Companion Animal Parasite Council. (CAPC)

ABOUT CAPC

The Companion Animal Parasite Council (CAPC) is an independent council of veterinarians and other animal health care professionals established to create guidelines for the optimal control of internal and external parasites that threaten the health of pets and people. It brings together broad expertise in parasitology, internal medicine, public health, veterinary law, private practice, and association leadership.

Initially convened in 2002, CAPC was formed with the express purpose of changing the way veterinary professionals and pet owners approach parasite management. The CAPC advocates best practices for protecting pets from parasitic infections and reducing the risk of zoonotic parasite transmission. The council has four major objectives:

• adoption of practices and procedures to protect pets from infections by parasites;
• adoption of practices and procedures to reduce the risk of transmission of zoonotic (transmittable from animals to humans) parasites from pets to people;
• collaboration among pet owners, veterinarians, and physicians to control infections by parasites; and
• collaboration with other groups that share the common interests of parasite control and animal and human health.