Reovirus Infection in Cats

Although there is no way for a pet owner to determine which virus (or even if a virus) is the cause of a cat’s symptoms, it is important that you contact your veterinarian if your cat is experiencing diarrhea or signs of a respiratory infection.

A reovirus can be one of several viruses that are members of the Reoviridae group of viruses. These viruses can cause illness in animals and plants, with particular animals or plants being susceptible to particular viruses. In animals, these viruses typically cause either a respiratory infection or intestinal infection and sometimes both. Diarrhea and the accompanying dehydration are the common results of a reovirus infection in cats. Upper respiratory infection may also be present in the same animal.

The symptoms of a reovirus infection are generally mild to moderate in cats that are otherwise healthy. Symptoms will likely be more severe in very young, elderly, or otherwise immunocompromised cats. Symptoms of reovirus infection may include the following: 

• Diarrhea, which may range from mild to severe
• Dehydration, which is the natural result of diarrhea
• Conjunctivitis (inflamed and red eyes)
• Nictitating membrane protrusion, which is the appearance of a cat’s third eyelid that is usually not visible because it generally only closes when the cat’s eyes are closed. This third eyelid may be red and inflamed 
• Coughing, which is rare in cats and therefore always concerning
• Inflammation of nasal mucous membranes accompanied by drainage

Types

There are several types of reoviruses, but the most common are the following:

• Orthoreovirus 
• Orbivirus
• Rotavirus 
• Phytoreovirus

Reovirus infection is caused by one or more of the numerous viruses that are classified together in the Reoviridae group. Cats are usually infected by these viruses in one of the following ways:

• Breathing in airborne particles that are carrying a reovirus
• Ingesting food or water that is contaminated with the feces of an animal that is carrying a reovirus

Although any cat can become infected with a reovirus, the following factors will make a cat much more susceptible to infection:

• Young kittens without fully developed immune systems are more susceptible to becoming ill
• Older cats that have weakened immune systems are at a higher risk
• Cats that suffer from one or more autoimmune diseases have a dangerously high risk factor for viral infection
• Cats that are sick with other viral infections, bacterial infections, injuries, or other illnesses will be more likely to become infected by a reovirus
• Cats that live in large confined populations of cats or other animals such as animal shelters will be at a higher risk

Your veterinarian will begin by listening to your observations and concerns regarding your pet’s health, and, if possible, will likely review your cat’s medical history. The vet will conduct a thorough physical examination to assess your cat’s overall health. In addition, the following diagnostic tests may be administered in an attempt to eliminate some of the numerous types of infections, such as bacteria, parasitic worms, and other viruses, that may be causing your cat’s symptoms:

• Complete blood count
• Blood chemistry 
• Urinalysis
• Fecal sample, which is often the best way to observe the presence of a reovirus

As is the case with many viral infections, there is little that can be done to address the viral cause of the intestinal symptoms in your cat. Antibiotics are not effective against viruses, and thus would only be effective in treating or preventing bacterial infections that may accompany the viral infection. Reovirus infection is generally self-limiting, meaning that it will “run its course.” Treatment, therefore, will attempt to address the accompanying, and possibly dangerous, dehydration that results from persistent diarrhea. This treatment includes the following:

• Increased fluid intake, usually oral, but sometimes intravenously or subcutaneously
• Electrolyte replacement, usually oral but sometimes intravenously or subcutaneously 

The prognosis is generally very good for an otherwise healthy adult cat that is experiencing a reovirus infection. As is often the case with minor viral infections in human beings, hydration and rest are usually the best ways for a cat to recover from a reovirus infection. In the days after your cat has been examined by your veterinarian it is important that you provide plenty of fluids, alone time, and quiet for your cat. Your vet may request a follow-up visit to check on your cat’s progress. If your cat’s symptoms do not get better in an amount of time that has been set by your vet, which is likely from three days to a week, or if your cat’s symptoms leave and then return, contact your veterinarian. Although nothing definitive can be done to prevent viral infection, providing proper nutrition and a clean, healthy, stress-free living environment that is not overcrowded are the best ways to avoid viral infections in the future.