Feline Corona Virus Infection

Feline Corona Virus Infection
Dr. Ed Mapes
Stonebridge Animal Hospital
McKinney, Tx.

Organisms in the Corona virus family cause illness in an array of animals – from pigs to dogs to cats. Corona infection of cats, depending on the strain of the virus involved, can range from non-symptomatic to diseases that are fatal in some patients. We have noted an up tick in positive cases at this hospital in recent months.

Cats are most commonly infected with Feline Corona Virus (FeCoV) by ingesting the feces of another cat that is infected and shedding the virus. The virus is very infectious, and is often seen in multi-cat households or catteries where the vast majority of cats are exposed and infected.

After entering the cat’s digestive system, the virus is engulfed by white blood cells known as monocytes, which are a normal part of the body’s immune defense mechanism. Whether an actual disease arises at this point depends on several variables including the virulence of the FeCoV strain and the immune capabilities of the infected individual. Some cats’ immune systems apparently conquer the virus particles and prevent any disease from resulting. These cats can be carriers of the virus though, and serve as reservoirs of infection for other cats.

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Figure 1 Pathway of possible outcomes after exposure to Feline Corona Virus

Figure 1 illustrates the various outcomes following exposure in cats. Roughly 3 % are wholly resistant to the virus and never show disease symptoms. About 65% develop short term symptoms of a mild nature, but control the virus thereafter. Other patients are unable to suppress the virus, and become persistently infected – with intermittent bouts of symptoms. These cats are the most likely to shed the virus to others. Up to 10% of infected individuals develop full blown cases of the severe, possibly fatal disease. Some cats never display symptoms if disease; in others the first evidence of infection can appear as mild upper respiratory signs or diarrhea ranging from mild to severe.

Cats either exposed to a particularly powerful virus or with immune systems unable to fight off the invaders may develop very serious disease, known as Feline Infectious Peritonitis (FIP). In these cases, the monocytes’ immune reaction causes inflammation of the blood vessel walls (vasculitis). The monocytes – which are able to initiate powerful immune reactions – are then able to leave the blood stream and invade other tissues.

FIP can present in two forms, with differing symptoms. The so-called “wet form” develops over several weeks’ time. Cats exhibit weight loss, reduced appetite, fever, and weakness. Advanced cases feature the accumulation of fluid in the abdominal cavity as a result of the body’s immune reaction against the virus. The fluid is thick, rather clear, straw-colored, and contains high levels of various proteins. Elevated levels of a particular type of protein (gammaglobulins) are usually seen in the bloodstream as well.

Symptoms seen in the “dry form” of FIP vary depending on the organ system affected. They can include neurological signs such as loss of balance and seizures. The eyes may exhibit inflammation, thickening of the iris, and the formation of material in the anterior chamber or cornea.

We diagnose the presence of FeCoV with specific blood tests. Further testing is done to demonstrate actual disease caused by the virus. Unfortunately, treatment in severe cases is often unsuccessful. It is based on the administration of glucocorticoids to diminish the immune reactions, along with antibiotics. A newer concept of therapy includes the administration of feline interferon, but the results are equivocal at this point in time.

We recommend that cats in multi-cat households be tested for presence of the virus, and observed carefully for any signs of disease. Since the majority of cases only involve mild and/or transient signs of disease, the practice of culling infected cats is no longer recommended as a matter of course. A vaccine that was touted as a preventative for FeCoV infection has not proved to be effective, and is not currently recommended.

Dr. Ed Mapes is a 1980 graduate of Michigan State University and previously owned two hospitals in Michigan. He now practices at the Animal Medical Center in McKinney. Please visit http://offshorevoyager.com/dredmapes.html

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