Encephalitis in Cats

By Michael Kearley, DVM on Jan. 3, 2023

gray and white cat being examined at the vet

What Is Encephalitis in Cats?

Encephalitis occurs when the brain becomes inflamed; it is a life-threatening condition that must be treated as quickly as possible.

In cats, encephalitis is often caused by an infection either directly to the brain or elsewhere in the body, reaching the brain via the bloodstream or nervous system. As a result, the brain swells, causing pain that often extends to the neck and other parts of the body. Confusion, seizures, and loss of consciousness can occur as damage to the brain worsens.

Encephalitis may occur by itself or with other parts of the nervous system, such as the spinal cord (encephalomyelitis) or the meninges (meningoencephalitis), which are the membranes that cover the brain and spinal cord.

Encephalitis in cats is not very common. It is seen more often in older cats, and there are no specific breeds predisposed to this condition.

Symptoms of Encephalitis in Cats

Your cat may experience vague symptoms that might not be noticeable right away, such as fever, lethargy, or a decreased appetite.

Cats with encephalitis often experience symptoms related to dysfunction of the nervous system, such as:

Generalized weakness and trouble walking
Neck pain
Behavioral changes (e.g., aggression, reclusiveness, depression)
Seizures
Visual deficits such as blindness
Head tilting and circling
Coma
Death

Causes of Encephalitis in Cats

Most cases of encephalitis in cats result from these types of infections:

Viral, such as feline infectious peritonitis (FIP) or rabies
Bacterial, such as Staphylococcus and Bacteroides spp.
Tick-borne, such as Lyme Disease
Parasitic, such as toxoplasmosis, heartworm disease, or roundworm infection
Fungal, such as cryptococcosis

Encephalitis in cats may also simply be caused by an infection spread from another part of the body, such as the ears or sinuses. Bite wounds or other traumatic injuries, foreign bodies, or immune-mediated cases where the body’s immune system attacks itself are other common causes of encephalitis.

How Veterinarians Diagnose Encephalitis in Cats

Your veterinarian usually conducts a physical exam and orders basic bloodwork such as a complete blood cell count (CBC), internal organ function screening, and urinalysis. The results from these tests are not sufficient to diagnose encephalitis, but they can suggest a neurologic condition resulting from an infection or inflammation. Additional tests may include chest x-rays and an abdominal ultrasound to look for other organ involvement and prognostic factors.

Be sure to tell your veterinarian of any recent travel you have been on, as certain diseases are more common in certain parts of the U.S. than others, and it can help narrow down the causes of your cat’s disease. Your vet may also want to know your cat’s vaccination status to make sure she is protected from possible exposure to wild animals and other diseases.

Your veterinarian may refer you to a veterinary neurologist for an MRI and CSF (cerebrospinal fluid) tap, which are done under anesthesia. The MRI takes an image of your cat’s brain, and the CSF tap collects some of the fluid that surrounds the brain and spinal cord to be analyzed for signs of infection and inflammation. The sample may also be cultured to look for infectious organisms.

In rare cases, a biopsy of the brain or a postmortem examination may be the only way to determine the nature of the disease. These cases may also be called “idiopathic” or “immune-mediated” when the cause of the disease is unknown.

Treatment of Encephalitis in Cats

The first step in treating encephalitis in cats is to admit them to the hospital and give them pain medication, antibiotics, IV fluids, nutrition, and anticonvulsants. Once the test results return, treatment is tailored toward the cause:

Antifungal medication such as Itrafungol for fungal infections
Antibiotics such as clindamycin for certain protozoal and bacterial infections
Immunosuppressive drugs such as prednisolone, cyclosporine, or lomustine for immune- mediated encephalitis

Treatment often takes weeks to months, and in some cases, years.

Recovery and Management of Encephalitis in Cats

The prognosis of a cat suffering from encephalitis depends on the cause. Cats with immune-mediated encephalitis have a better prognosis despite needing lifelong treatment, whereas encephalitis caused by rabies will more likely result in death. For some cats, relapses can occur if treatment is weaned or discontinued. Discuss the risks and benefits of future vaccinations with your veterinarian, as relapses can occur after vaccinations.

Cats with encephalitis may also require physical therapy or environmental modifications if permanent damage occurs. Unfortunately, some cats may die or are humanely euthanized despite treatment.

Prevention of Encephalitis in Cats?

There is no guarantee that your cat will not develop encephalitis in their lifetime. However, there are some steps you can take to minimize the risk —keep your cat indoors, vaccinate them, and promptly treat them for any infection, bite, or wound.

Featured Image: iStock/Ivan-balvan