Cryptosporidiosis in Cats

At a glance

  • About: Cryptosporidiosis is a protozoal infection affecting the small intestine and occasionally the respiratory tract of cats.
  • Transmission: Infection occurs via the fecal-oral route via contaminated water, food, feces, objects or during grooming.
  • Symptoms: Don’t always show in healthy cats, in those who are immunocompromised or kittens, diarrhea, loss of appetite, low-grade fever and dehydration can develop.
  • Treatment: There are no effective medications to kill the parasite, treatment is based on supportive care such as fluid therapy and
    nutritional support.

What is cryptosporidiosis?

Cryptosporidiosis (or crypto) is the name of a protozoal infection affecting the small intestine and sometimes the respiratory tract of affected hosts. It is caused by single-celled parasites of the genus Cryptosporidium which infects a wide variety of vertebrates including cats, dogs, humans, horses, and livestock.

There are over 50 species of Cryptosporidium with have their preferred hosts. While cats (and humans) can be infected with sub-species normally found in other animals, infection tends to be less severe. The natural hosts of the sub-species have been included in bold font.

  • Cryptosporidium felis – Cats and occasionally humans (rare)
  • Cryptosporidium canis – Dogs and occasionally humans (rare)
  • Cryptosporidium parvum – Cattle, sheep, goats, cats, dogs, humans
  • Cryptosporidium hominis – Humans
  • Cryptosporidium meleagridis – Turkeys, parrots and humans
  • Cryptosporidium muris – Rodents, cats, occasionally humans (rare)

Cryptosporidiosis (along with Giardiaisis) are both well known protozoal infections that are common causes of waterborne disease.

It is estimated that up to 15% of cats in the United States have been infected with Cryptosporidium at some point in their lives. Cats from shelters have a higher rate of infection due to often crowded conditions.

Life cycle

Nonsporulated (non-infective) oocysts are passed in the feces of an infected host.

Most oocysts are thick-walled and are infective when they are passed out of the body in the feces, according to the Centers For Disease Control (CDC), it may also be possible that oocysts pass out of the body by respiratory secretions. Each oocyst contains 4 sporozoites in each of 2 sporocysts. The zoites invade the intestinal cells and develop to the schizont stage. The schizonts release more zoites which invade new cells and give rise to the next generation of schizonts. There are 3 generations of schizonts. Zoites released from the last generation of schizonts invade cells and form gametocytes. The male gametocyte releases gametes which fuse with the female gametocytes and form oocysts.

A small number of oocysts are thin-walled and remain within the body which causes re-infection.


Infection occurs via the fecal-oral route. Once the oocysts have become infective in the environment they infect their next host in a number of ways.

  • Drinking contaminated water such as lakes and dams etc., but occasionally the water supply can become contaminated.
  • Eating contaminated food. This may have occurred during preparation (unwashed hands, contaminated food preparation area), during slaughter or infected prey.
  • Exposure to objects (fomites) that have been contaminated with oocysts such as food bowls and litter trays.
  • Ingesting oocysts from the coat during self or mutual grooming.


The incubation period is between 1 – 10 days. Healthy adults are often asymptomatic, however, kittens under six months and immunocompromised cats are typically symptomatic. Symptoms can vary depending on the sub-species.

The most common symptom of cryptosporidiosis is watery diarrhea, other symptoms may include:

  • Anorexia (loss of appetite)
  • Abdominal pain
  • Low-grade fever
  • Lethargy
  • Dehydration, due to diarrhea
  • Weight loss


Diagnosing cryptosporidium can be difficult due to the small size of the oocysts.

Stool samples: A sample of feces is obtained and sent to a specialist laboratory for testing. Cryptosporidium oocysts are detected using the acid-fast stain technique. To increase the chance of an accurate diagnosis, several stool samples may be required.

Serology: To look for the presence of antibodies to Cryptosporidium in a blood sample. Unfortunately, this cannot diagnose a current infection, just that cat has had exposure to the organism at some point in its life.

Enzyme-linked immunofluorescent antibody (ELISA): A stool sample added to a petri dish that contains cryptosporidium antigen. If the stool sample contains antibodies to Cryptosporidium, these will bind together with the antigen in the dish.

Intestinal biopsy: Can reveal the organism as well as damage to the lining of the intestines caused by the organism and the cat’s own immune response.


There are no effective medications to treat cryptosporidiosis in cats. A cat with a healthy immune system will rid itself of the parasite in time.

Some veterinarians may prescribe antiprotozoal drugs to treat immunocompromised cats. These may include Tylosin, Paromomycin, Clindamycin, Azithromycin, and Fenbendazole.

Supportive care may be necessary. This may include nutritional support and IV fluids and electrolytes to treat dehydration and anti-diarrheal medications.

Can I catch cryptosporidium from my cat?

It is possible, yes although it would seem to be reasonably uncommon. As we have already mentioned, most strains of Cryptosporidium are host specific. Drinking contaminated water makes up the majority of human infections. C. parvum is responsible for most cases in humans, or C. hominis, which is specific to humans.

As with cats, a healthy immune system usually fights off the disease relatively quickly, however, it can have devastating effects on the immunocompromised, it is important to keep infected cats away from immunocompromised people.

It is always safer to assume that a cat infected with Cryptosporidium could potentially infect other pets and humans and take the appropriate safety precautions.


Cryptosporidium oocysts can remain in the environment for 2-6 months. The following disinfectants are effective.

  • 3% hydrogen peroxide
  • Virox, Accel – Accelerated hydrogen peroxide


There is no foolproof way of preventing cryptosporidiosis, however, there are ways to reduce your cat’s exposure to the parasite.

  • Always make sure food preparation surfaces are clean when preparing food for you or your cat.
  • Wash your hands before preparing food for your cat.

How can I reduce the chances of catching cryptosporidiosis from my cat?

  • Scoop litter trays daily and empty once a week. Place solids in a plastic bag and dispose of them in the outside garbage. Wear rubber gloves when handling litter trays.
  • Clean and disinfect the floor with a 10% solution of bleach.
  • Always wash your hands after touching your cat.
  • Immunocompromised people should not handle litter trays.
  • Keep litter trays well away from food preparation areas.


  • Julia Wilson, 'Cat World' Founder

    Julia Wilson is the founder of Cat-World, and has researched and written over 1,000 articles about cats. She is a cat expert with over 20 years of experience writing about a wide range of cat topics, with a special interest in cat health, welfare and preventative care. Julia lives in Sydney with her family, four cats and two dogs. Full author bio

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