Meningitis is a neurological condition that occurs in many species – including dogs! There are many causes of meningitis in dogs and this article will cover the most common cause, along with how to recognise this condition and how it can be managed.
What is meningitis?
The term meningitis means ‘inflammation of the meninges.’ Anatomically, the meninges consist of 3 membrane layers surrounding the brain and spinal cord and they exist in all mammals (including humans!). They have an extremely important role to protect the central nervous system. I often think of the meninges as bubble wrap, encasing and cushioning something extremely fragile!
What are the causes of meningitis in dogs?
The most common cause of meningitis in dogs is immune-mediated inflammatory disease; however, the process by which this occurs is very complex and also not fully understood. This type of meningitis is usually termed ‘steroid responsive meningitis-arteritis,’ also known as SRMA. This article will focus mainly on SRMA, as this is more commonly seen and diagnosed in practices compared to other causes of meningitis. SRMA patients experience inflammation of the meninges and artery walls.
SRMA is most commonly seen in younger dogs, usually under 2 years of age. The condition can still occur in older patients but this is quite a rarity. This type of meningitis is also over represented in certain breeds including Beagles, Boxers and Weimeraners. However, it is not contagious to other dogs as it is not infectious.
To briefly touch on other causes of meningitis in dogs, this can include bacterial, viruses, fungal infections and parasitic diseases. Bacterial causes of meningitis can occur secondary to another condition including ear infections where the bacteria spreads to the meninges via systemic spread.
Are there any clinical signs?
So, how will you know that your dog has meningitis? Below lists the most common clinical signs that your dog may show if they have meningitis (this list is not exhaustive):
- Spinal and/or neck pain – your dog may stand in an abnormal posture and may appear hunched which can be a classical sign of spinal pain. Dogs that are experiencing neck pain may be reluctant to move their head and show cervical rigidity. When the Vet examines them they may react painfully to any form of neck manipulation.
- High temperature/fever (pyrexia)
- Reluctance to move and/or muscle stiffness
- Lethargy and weakness
In SRMA patients, neurological deficits and loss of limb co-ordination is not commonly seen. Furthermore, SRMA is usually an acute (sudden onset) condition, but more chronic (slower-developing) forms can sometimes occur.
If untreated, in more advanced meningitis cases clinical signs may be more severe and may include more general neurological abnormalities, paralysis, seizures and blindness. If you see any of the above clinical signs in your dog, contact your local Vet immediately.
How is it diagnosed?
Often, your Vet may suspect meningitis is occurring based on your dog’s clinical signs and clinical history. Unfortunately, diagnosing meningitis is not always very straightforward.
Diagnosis is made using a variety of diagnostic tests including bloods and radiographs to rule out other causes of spinal/neck pain including orthopaedic issues such as spinal injuries or vertebral fractures. Depending on the practice, your Vet may advise referral to a hospital for further investigations including CSF analysis (cerebro-spinal fluid). CSF analysis is of high importance in the diagnosis of suspected meningitis cases. This sample is taken under general anaesthesia and it will then be sent to the lab for analysis. The presence of inflammatory cells within the CSF sample supports the diagnosis of SRMA. In SRMA cases there is negative bacterial growth identified in the samples submitted.
How is meningitis treated?
As SRMA is immune-mediated and not caused by an infection, antibiotics therefore play absolutely no role in the treatment and management of this condition.
The treatment plan for SRMA is given away by its name. This condition is treated with steroids (glucocorticoids), which aim to reduce inflammation of the meninges. Your Vet will start your dog on a high immunosuppressive dose of steroids and you will usually see a very quick improvement in your dog. The prognosis for SRMA patients is good and 80-100% of SRMA patients respond to the initial treatment (Jones, 2021).
The steroid course can last for weeks to months and across this time period, your Vet will steadily reduce their dose and will regularly reassess your dog. It is vital that the steroids are not stopped suddenly and that the dose is tapered at a gradual pace, your Vet will guide you on this. Steroids especially when used in high doses may result in some side effects for your canine friend. These side effects include increased appetite, weight gain, increased thirst and increased urination.
It is very important to understand that once your dog has experienced SRMA once, they have a 20-30% chance of relapsing again in the future and unfortunately it is impossible to predict when and if this will happen (Bierdermann et al, 2015).
What if it’s a different type of meningitis?
The treatment of bacterial meningitis is dependent on the bacterial organism present and therefore the antibiotic is usually based on the culture and sensitivity results. Additionally, bacterial meningitis is more serious for your dog and can result in a worse prognosis. Early intervention and support is essential in these cases. Depending on the severity of the meningitis, some dogs may require intensive support and hospitalisation.
So why not antibiotics?
I hope that this article has answered the question, ‘why don’t dogs with meningitis get antibiotics?’: SRMA is the most common cause of canine meningitis, but it is not caused by bacteria, so is not treated with antibiotics. Thankfully, following an SRMA diagnosis the prognosis is often very good, although relapses may occur. If your dog does have bacterial meningitis, then of course antibiotics will be used: but this is much, much rarer than in people.