Meningitis is the term used to describe an inflammation of the meninges, the protective outer membranes that cover the spinal cord, and central nervous system. “Meningoencephalitis” is the term used to describe an inflammation of the brain and its lining. Meningitis is a serious disease and requires diagnosis and treatment as soon as possible. Meningitis can occur from several potential causes, both infectious and non-infectious.
What are the types of meningitis?
Infectious meningitis can be caused by a number of infections, including those of bacterial, viral, fungal, and protozoal (parasitic) origin. The infection usually begins elsewhere in the body and spreads to the central nervous system via the sinuses, the inner ear, the vertebrae, or traumatic injuries such as a bite wound. Toxins or autoimmune diseases that weaken the animal’s natural ability to fight infections may be the cause as well. Infectious meningitis can occur in any age or breed of dog. Meningitis in cats is rare, with the most common cause being feline infectious peritonitis (FIP). Cryptococcosis (fungal) and toxoplasmosis (parasitic) infections have also been found in cats.
Meningitis may also be non-infectious in nature, caused by an immune-mediated inflammatory response, in which the body’s immune system attacks its own tissues. The non-infectious forms, also known as “meningoencephalitis of unknown origin (MUO),” can be broken down into several specific types, some connected to a specific breed of dog.
- Steroid-responsive meningitis-arteritis (SRMA) is a systemic immune‐mediated condition affecting the meninges and associated arteries. Also known as “steroid responsive meningitis arteritis,” it is the most common type of meningitis in dogs. It typically affects medium to large breed dogs 6-18 months of age. Breeds predisposed to this condition are Bernese Mountain dog, Border collie, Boxer, English Springer spaniel, Jack Russell terrier, Nova Scotia duck tolling retriever, Weimaraner, and Whippet.
- Granulomatous meningoencephalitis (GME)is characterized by granulomatous lesions (vascularized tissue) within the brain and/or spinal cord. GME can occur in any age and breed of dog, but most commonly in middle aged, female, small-breed dogs. (But my young, male, Doberman was diagnosed with this.)
- Necrotizing meningoencephalitis (NME) is a rapidly progressive, fatal inflammatory brain disorder affecting young toy breed dogs such as Pugs, Maltese, Chihuahua, Shih Tzu, Pekingese, and Papillon.
- Necrotizing leukoencephalitis is fatal and causes intense necrotizing (tissue death) lesions in the brain stem and cerebellum. This type can be seen in any age, but most often in young, small breeds such as the Yorkshire terrier and French Bulldog.
- Idiopathic eosinophilic meningoencephalitis causes inflammation of the brain, spinal cord, and their membranes due to abnormally high numbers of eosinophils, a type of white blood cell, in the cerebrospinal fluid. Young, large breed males such as Golden Retrievers and Rottweilers are predisposed.
- Greyhound Encephalitis is a fatal meningoencephalitis with lesions usually occurring within the anterior (front) of the cerebrum.
- Other forms of meningitis can be traced to parasitic infections (German Shepherds) and fungal infections (American Cocker Spaniel).
What are the signs and symptoms of meningitis?
Signs and symptoms vary among dogs and cats. The most common clinical signs of meningitis include:
- Loss of appetite
- Decreased blood pressure
- Neck or back pain, resulting in stiffness and having trouble when walking
- Muscle spasms in the neck, back, or legs
- Inability to track objects with the eyes, and changes in the optic nerve upon examination
A dog or cat with meningoencephalitis may show neurologic signs including seizures, depression, balance problems, blindness, pacing, circling, paralysis, and loss of consciousness.
How is meningitis diagnosed?
Early diagnosis and treatment can mean the difference between life and death when an animal is suffering with meningitis. Meningitis is often misdiagnosed as the flu, resulting in a delay in treatment. As testing progresses, your veterinarian may refer you to a veterinary neurologist. Diagnostic procedures include:
- A thorough physical examination by a veterinarian.
- Baseline blood testing that includes a complete blood cell count (CBC), serum biochemistry profile, and urinalysis.
- Depending on the result of the baseline bloodwork, specific blood tests that identify infectious causes of meningitis should be performed.
- Magnetic resonance imaging (MRI) or computerized tomography (CT) is an important diagnostic tool. These tests are performed under general anesthesia. Changes in the structure of the nervous system and surrounding tissues are observed to determine the location and cause of the meningitis.
- A cerebrospinal fluid (CSF) tap is performed to collect a small amount of spinal fluid, which is analyzed for the presence of abnormal cells or organisms. The collection process can be risky as it involves inserting a needle between the vertebrae in the neck or lower back. Because of the risks, an MRI or CT is preferred in many circumstances.
How is meningitis treated?
The treatment of meningitis depends on the underlying cause. For example, bacterial and protozoal infections are typically treated with antibiotics. Fluid collected during a spinal (CSF) tap can undergo culture and sensitivity testing to determine which antibiotics are most effective against the bacteria that are present. Steroid-responsive meningitis is treated with steroidal medications. The patient is initially started on a relatively high dose of steroid, with the dose tapered over the first several weeks of treatment. Viral meningitis does not have a medical cure and is treated with supportive care.
There are side effects associated with these treatments. The side effects of steroidal medications such as prednisone include increased thirst and urination, increased appetite, and increased susceptibility to infection. These drugs suppress the immune system, resulting in the animal being susceptible to other infections. Side effects of drugs used to reduce brain swelling (cytosine arabinoside, cyclosporine, azathioprine, leflunomide and procarbazine) include gastrointestinal upset, lack of appetite, nausea, vomiting, diarrhea, kidney and liver toxicity, as well as blood effects such as low red and white blood cell count, and low platelets.
Regardless of the cause, there are supportive measures that can be employed in the treatment of meningitis.
- Intravenous fluids to reverse or prevent dehydration
- Medications to decrease brain swelling
- Pain medications to alleviate discomfort
- Antiepileptic drugs if the animal experiences seizures
- Bed rest and care to conserve energy and allow the body to fight the disease and heal
Incorporating adjutant holistic therapies can be very beneficial in reducing symptoms of meningitis, and in some cases, can shorten the course of the disease. From a Traditional Chinese Veterinary Medicine (TCVM) perspective, inflammation signals heat in the body. Meningitis is considered a “warm” disease which causes fever and depletes the Yin (cool, liquid) energy in the body. The goal with TCVM treatment of meningitis is to clear the heat. Chinese herbs that reduce inflammation and have antibacterial and antiviral qualities can assist in the management of the disease. Acupuncture treatment can not only help the root cause of meningitis but can also deal with the symptoms many animals experience. Ozone therapy decreases inflammation, activates the immune system by stimulating cytokine production, and inactivates bacteria, fungi, and viruses.
Supporting the immune system is critical in the treatment of meningitis. Probiotics, mushrooms, adaptogens, antioxidants, and products containing gut-supporting herbs can be added to a species-appropriate whole-food diet for maximum benefit.
The prognosis for meningitis depends upon the underlying cause. While there is no cure for the various forms of meningitis, management of symptoms is possible in many cases. Infectious meningitis, although rare, can cause death, especially if not diagnosed in its early stages. Meningitis that responds to steroids can have a better prognosis; however, long-term use of steroids can permanently alter the immune system. Unfortunately, certain forms of meningitis, such as those that are necrotizing, are fatal. Overall, the prognosis for meningitis is guarded, even with aggressive treatment. Being familiar with the symptoms of meningitis, especially if your pet has been sick is crucial for his or her chances of survival.