Meningitis in Cats

What is meningitis?

Meningitis is an inflammation of the protective membranes covering the brain and spinal cord (meninges). The central nervous system (CNS) comprises the meninges, the brain, and the spinal cord. Any of these can become inflamed if the brain is affected it is known as encephalitis if the spinal cord is affected it is myelitis. One of a combination can become affected.

• Brain and meninges = meningoencephalitis.
• Meninges and spinal cord = meningomyelitis.
• Brain, meninges, spinal cord = meningoencephalomyelitis.

Meningitis is not a disease itself, rather a symptom of an underlying disorder that has resulted in the meninges become inflamed or infected. It is an extremely painful and potentially fatal condition that requires urgent medical attention.

Any cat can develop meningitis however it is seen most often in older cats and immunocompromised cats. The condition can be chronic (slow and progressive) or acute (sudden onset).

Causes

There are several possible causes that may be infectious or non-infectious. The most common cause is due to viral, fungal or protozoal infection and less commonly, bacterial.

Infectious meningitis:

• Cryptococcosis, histoplasmosis, and blastomycosis are fungal which in healthy cats usually remain localised. In immunocompromised cats, it can disseminate (spread) to other parts of the body including the brain.
• Toxoplasmosis is a protozoan infection in cats that usually produces no signs, immunocompromised cats may develop the disease.
• Feline infectious peritonitis (FIP) is an almost always fatal viral disease. In most cats, the coronavirus is self-limiting, however, in some cases, it mutates into a lethal form. Feline immunodeficiency virus (the feline equivalent of HIV in people) and rabies can also cause meningitis in cats.
• While rare, bacterial meningitis can occur when a nearby infection spreads to the brain, this may be from a localised infection of the eyes, ears or nasal cavity, bacteria in the blood usually from a heart valve (endocarditis) or urinary tract infection or direct inoculation via a penetrating bite wound. Bacterial may be caused by tularemia, staphylococci, Pasteurella spp, Nocardia spp.

Non-infectious meningitis:

• Certain medications (NSAID’s, antibiotics (amoxicillin, sulfamethoxazole), immunosuppressive medications, Ranitidine)
  
• Tumours
• Immune-mediated disorders
• Idiopathic (unknown cause)

Clinical signs

It is often hard to determine if a cat is sick as they are so good at hiding signs of pain and discomfort, so it is up to us to keep a diligent eye on them and look for changes in behaviour as well as other clues.

Symptoms can range from generalised to CNS type and may include:

• Lethargy
• Loss of appetite
• Vomiting
• Intermittent fever

As CNS symptoms progress, your cat may experience the following:

• Cervical rigidity (neck stiffness)
• Photophobia (sensitivity to light)
• Ataxia (wobbly gait)
• Disorientation/confusion
• Hyperesthesia (rolling skin)
• Sensitivity to touch
• Paralysis
• Seizures
• Coma

Diagnosis

Your veterinarian will perform a complete physical and neurological examination of your cat and obtain a medical history from you including the onset of symptoms, any medications or toxins your cat may have ingested, underlying medical conditions. He will need to perform some diagnostic tests to determine if your cat has meningitis as well as find the underlying cause.

Tests:

• Baseline tests: Biochemical profile, complete blood count, and urinalysis to evaluate organ function. If an infection is present, there may be an increase in white blood cells, low white blood cells may occur in cats with FIV or FIP. Anemia may also be present in cats with FIP. Bacteria may be present in urine samples if your cat has a urinary tract infection.
• Imaging studies: CT or MRI of the brain may reveal inflammation or other abnormalities such as lesions, bleeding or tumours.
• Cerebrospinal fluid tap (CSF): This test involves obtaining a sample of the fluid from the subarachnoid space which surrounds the spinal cord and brain. The fluid is then sent to a laboratory for culture and evaluation.
• Echocardiogram: Ultrasound of the heart to evaluate the heart valves for signs of infection.
• Antibody tests: A blood test to detect antibodies to Toxoplasma gondii, feline infectious peritonitis or feline immunodeficiency virus. Many cats have had exposure to the coronavirus which is responsible for FIP and T. gondii, so a positive test isn’t always necessarily proof a cat has FIP.
• Fecal tests: Fecal samples will be analysed for the presence of T. gondii oocysts. Most cats with toxoplasmosis show few symptoms of infection when cats do become sick it is usually due to an underlying disorder that has weakened the immune system such as feline leukemia virus or feline immunodeficiency virus.
• PCR or ELISA tests: If FIP is suspected in addition to blood tests to look for antibodies, your veterinarian may also take a sample of the fluid in the abdomen for evaluation as well as specialised tests to detect the virus in the blood
• Cytology: Microscopic evaluation of nasal or ocular discharges.

Treatment

The goal of treatment is to manage symptoms and address the underlying condition, which may include:

• Broad-spectrum antibiotics will be prescribed to treat bacterial infections and toxoplasmosis.
• Fungal infections will be treated with anti-fungal medications.
• Corticosteroids will be prescribed to control inflammation.
• Anti-seizure medications will be administered if necessary.
• Cats with meningitis are usually extremely sick, and supportive care is vital. This may include fluids to treat dehydration, nutritional support, and analgesics to relieve pain.

Other outcomes:

• FIP is almost always incurable although there have been recent advancements with this heartbreaking disease.
• Rabies is incurable and euthanasia is sadly the only outcome.

Home care

• Administer medications as prescribed.
• Rest is vital while your cat recovers. Keep your cat indoors and in a calm, quiet environment.
• Contact your veterinarian if your cat’s symptoms become worse.

Prognosis

Prognosis depends on the cause of meningitis, if it is viral or fungal, the prognosis is poor, bacterial infections have a slightly more favourable outcome.

Prevention

Prompt medical treatment of eye or nasal infections and penetrating head wounds can reduce the chances of bacteria spreading to the brain.

• Desex cats to reduce their risks of contracting FIV.
• Keep cats indoors in areas where rabies, fungal infections, and ticks are present.
• A healthy cat has a stronger immune system, which can help him avoid the spread of infection to the brain.