What is it?There are several types of meningitis in dogs, but the most important is Steroid Responsive Meningitis Arteritis (SRMA). This occurs when the meninges and the blood vessels in the brain become inflamed. It is thought to be an auto-immune disease where the body attacks its own cells, but no specific triggers have been identified. Infectious causes are uncommon in the UK due to routine vaccinations.
Why is it important?SRMA is a painful condition which has a big impact on the dog’s normal behaviour making them depressed and unwilling to exercise or play. It is, however, not contagious and so there is no risk to other dogs or humans. Early, aggressive treatment usually has a good outcome, so seeking veterinary advice early is recommended.
What’s the risk?SRMA typically affects young dogs (8-18 months old) with some breeds, typically medium to large dogs, being overrepresented. Examples include breeds such as Beagles, Boxers, Shorthaired Pointers and Bernese Mountain dogs.
What happens to the dog?Affected dogs tend to be reluctant to move, causing them to walk stiffly and often have a low head carriage due to neck pain. On examination there is spinal pain (usually in the neck) and often hyperaesthesia (exaggerated response to touch) but the rest of their nerve responses and reflexes are usually normal (except in some chronic cases). Many dogs also have a fever and lose their appetite. Some dogs can also have painful swollen joints due to the development of arthritis as part of the disease process.
How do you know what’s going on?
A definite diagnosis of SRMA comes from a spinal fluid (CSF) tap taken under general anaesthetic and analysed in a laboratory. Dogs with SRMA have an increased number of cells in their CSF fluid, in particular inflammatory cells called neutrophils, as well as increased protein levels. Increased protein can also be detected on blood testing, in particular C-reactive protein, however this is not specific for SRMA. Blood tests may also show increased white blood cells, in particular neutrophils. X-rays can be taken to rule out other causes of spinal pain such as fractures.
An abnormal CSF tap along with clinical signs is usually enough to diagnose SRMA but sometimes a CT or MRI scan may be needed to rule out other options, and also to ensure it is safe to take a CSF tap.
What can be done?
Treatment typically involves high dose steroids (prednisolone) which are slowly reduced (tapered) over time (usually 6-9 months). At high doses, steroids can cause stomach upsets and so often gut protectors may be prescribed in the first few months. Unfortunately, steroids have a lot of potential side effects, particularly at higher doses, and dogs will often drink, urinate and eat excessively as well as gain weight, pant and be more lethargic. Despite this, steroids are the preferred treatment for SRMA and the outcome is usually very good, with most patients showing marked improvement within 2-3 days and returning to normal by two weeks.
Cases that are poor to respond to treatment, or relapse whenever steroids are tapered, will generally be monitored with further CSF/blood sampling. These dogs may be given alternative medications such as azathioprine and cyclosporin.
How can I protect my pet?
Around 20% of dogs previously diagnosed with SRMA will relapse once weaned off medication, or during the process. Clinical signs will return and these patients will need to go back on steroids or “take a step back” on their tapering programme to regain control of the disease before beginning to reduce the dose again.
There is no known prevention for SRMA as at present the cause is still unknown.