Cryptosporidium in Cats – Symptoms, Diagnosis & Treatment


Symptoms of cryptosporidium   How do cats become infected?   Life cycle   Diagnosing cryptosporidium   How is it treated?   Can I catch cryptosporidium from my cat?

Cryptosporidium at a glance

  • Cryptosporidium is a protozoal infection affecting the small intestine and occasionally the respiratory tract of cats.
  • Infection occurs via the fecal-oral route via contaminated water, food, 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.
  • There are no effective medications to kill the parasite, treatment is based on supportive care such as fluid therapy and nutritional support.

Cryptosporidium in cats

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 up to 50 sub-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)

Cryptosporidium (along with Giardia) are both well known protozoal infections which 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 of Cryptosporidium 

Nonsporulated (non-infective) oocysts are passed in the feces of an infected host. It usually takes between 3 – 6 days after infection for oocysts to be passed in the feces.

Most oocysts are thick walled and are infective when they are passed out of the body in the feces, according to the CDC, it may also be possible that oocysts pass out of the body by respiratory secretions [2]. 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 causing re-infection.

How do cats become infected with Cryptosporidium?

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. This is usually from untreated water supplies such as lakes, 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), or during slaughter or infected prey.
  • Exposure to objects (fomites) which have been contaminated with oocysts such as food bowls, litter trays.
  • Ingesting oocysts from the coat during self or mutual grooming.

What are the symptoms of cryptosporidiosis in cats?

Healthy adult cats often show no signs of infection or self-limiting symptoms such as mild diarrhea, kittens under six months of age and immunocompromised cats, such as those with Feline Immunodeficiency Virus (FIV) or Feline Leukemia Virus (FeLV) are most often affected and have longer lasting and more severe symptoms and may even die. Symptoms can vary slightly depending on the sub-species. In humans, C. Hominis can also result in vomiting, but this doesn’t appear to be the case for C. Felis and C. Parvum which can infect cats.

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

How is cryptosporidiosis diagnosed?

Diagnosing cryptosporidium can be difficult due to the small size of the oocysts.  Specific tests will need to be carried out to look for the parasite. Tests may include:

Stool samples should be sent to a specialist laboratory for testing. The oocysts of Cryptosporidium are detected using the acid-fast stain technique, which stains the oocysts red. To increase the chance of an accurate diagnosis, several stool samples may be required.

Serology to look for the presence of antibodies to Cryptosporidium, however, all this will show is that the cat has had exposure to the organism at some point in his life, but not if it is current.

Enzyme-linked immunofluorescent antibody (ELISA) is another test using a stool sample which is sent to a laboratory. There it is added to a petri dish which contains cryptosporidium antigen. If the stool sample contains antibodies to Cryptosporidium, these will bind together with the antigen in the dish.

An 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.

FIV and FeLV testing in cats may be carried out in cats who have tested positive to Cryptosporidium which doesn’t resolve on its own quickly.

How is cryptosporidiosis treated?

There are no effective medications to treat cryptosporidiosis in cats. A cat with a healthy immune system will rid themselves 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 cryptosporidiosis 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. The majority of human infections are caused by drinking contaminated water.  Most cases of cryptosporidiosis in humans is caused by C. parvum which has a wide range of hosts or C. hominis, which is host 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. Cats who are infected should be kept 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.

Preventing cryptosporidiosis in cats

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

  • Avoid letting him drink from water outside, such as lakes, dams, streams which could be contaminated.
  • 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?

  • Always handle feces with care. Use rubber gloves when cleaning out litter trays.
  • Solids should be removed at least once a day, placed in a plastic bag and in the garbage outside.
  • Litter trays should be fully emptied and disinfected at least once a week. Clean and disinfect the floor around litter trays also.
  • Always wash your hands after touching your cat.
  • Never let immunocompromised people clean out litter trays.
  • Keep litter trays well away from food preparation areas.