Below are the most common gastrointestinal issue and parasites found in all breeds of cats.  The symptoms of many of these are the same but the treatment protocols may differ, so we always recommend running a feline diarrhea PCR (polymerase chain reaction) panel for exact diagnosis.

Feline Coronavirus (FCoV)
Feline Coronavirus is a common viral infection in cats. It generally causes asymptomatic infection, but can cause mild diarrhea. As yet poorly understood changes in the virus can give rise to mutants that lead to the development of feline infectious peritonitis (FIP). Most cats infected with a FCoV eliminate virus following infection, but some cats may develop a persistent infection.  

Feline Panleukopenia Virus (FPV)
Young and unvaccinated cats are susceptible to feline panleukopenia virus infection. Infection by this virus can result in an acute or peracute systemic and enteric infection characterized by fever, vomiting, diarrhea, anorexia, and malaise. The virus infects bone marrow tissue resulting in severe panleukopenia. FPV infection is frequently fatal in young kittens, but adults are likely to recover.

Campylobacter
Campylobacteriosis is an infection caused by the Campylobacter jejuni bacterium. It is associated with enteritis (inflammation of the small intestine), resulting in diarrhea. Kittens, particularly those under six months of age are most susceptible to infection due to their immature immune systems.

Infection occurs via direct contact with infected animals, contact with contaminated feces, raw meat, especially chicken, water and fomites (inanimate objects such as food bowls, litter trays, door handles). The incubation period is between 2-5 days.

Clostridium
Clostridial is caused by an overgrowth of the bacteria Clostridium in the intestine. Often, the bacteria is acquired from the environment (e.g., flora) or as the result of eating raw, undercooked, or old meat. Other risk factors include:

• Dietary changes
• Abnormally high pH level in the intestine
• Deficiency of antibodies
• Stress to the digestive system

Cryptosporidium
Cryptosporidium is an intestinal parasite that is commonly ingested through contaminated water, food or feces. The resulting diseased condition, cryptosporidiosis, can typically be treated effectively with medications. This disease is no more likely to affect one breed than another, and is commonly seen in kittens.

The most common symptoms of this disease are fever and diarrhea. Cats will also display intolerance for food, or in more serious cases, will suffer from organ disease. Other symptoms include lethargy, and intolerance for exercise.

Giardia
Giardiasis is a medical condition that refers to an intestinal infection caused by the protozoan parasite giardia, and this parasite can also infect animals, including cats. Giardia is the most common intestinal parasite found in humans.

Contamination can be from direct or indirect contact with the infected offspring (cysts), but typically, cats will acquire the infection by ingesting the infectious cysts that are shed by another animal through its feces. The organisms, once ingested, make their way into the intestine, often causing diarrhea. Treatment for this infection is usually performed on an outpatient basis with a good prognosis.

Salmonella
Salmonellosis is an infection found in cats caused by the Salmonella bacteria. Along with causing gastroenteritis and septicemia in cats, salmonellosis is a zoonotic bacterial disease, meaning it can be transmitted to humans.

The severity of the disease will often determine the signs and symptoms that are overtly present in the cats. Symptoms commonly seen in cats with salmonellosis include: fever, shock, lethargy, diarrhea, vomiting, anorexia, weight loss, dehydration, skin disease and mucus in stool.

Toxoplasma gondii
Toxoplasmosis is an infection caused by the Toxoplasma gondii (T. gondii) parasite. It is one of the most common parasitic diseases and is known to affect nearly all warm-blooded animals and humans, but cats are the primary living host. This parasite completes its life cycle in cats, and they are the only mammals in which this parasite is passed through the feces and into the environment as part of the life cycle. However, contact with raw meat and unwashed produce is also a very significant and well known source of human infection.

Both acute and chronic forms of toxoplasmosis exist, where the chronic form is usually a low-grade disease without any clinical symptoms, and the acute form is more symptomatic.

Tritrichomonas
Cats and kittens from shelters and catteries are at higher risk of contracting an intestinal parasite that causes a long-term, foul-smelling diarrhea. The parasite, Tritrichomonas foetus (T. foetus) is a single-celled protozoan that lives in the colon of cats and is shed in the feces.

Younger animals are most likely to have diarrhea as the result of infection. Adult cats may or may not show signs, but can still be carriers of the parasite, passing it into the environment through their feces, and putting uninfected cats at risk of acquiring it. Symptoms may not appear in an infected animal for years after being exposed.

The main symptom is a longstanding bout of loose smelly stools, sometimes mixed with blood or mucus. Cats may have difficulty passing the loose stools and strain to empty the bowels. Stool may leak out of the anus and cause redness and pain around the area.