The 5-year-old hobby horse developed meningitis – an infection of the meninges, the membranes that surround the brain and spinal cord – the day after undergoing surgery to remove an abscessed upper molar tooth root and sinus surgery to debride and flush her infected sinuses. With prompt diagnosis and treatment, the mare defied the odds and survived, said Lindsey Boone, DVM, PhD, Dipl. ACVS, associate professor of equine surgery and sports medicine at the College of Veterinary Medicine at Auburn University in Alabama.

First an abscess, then a sinus infection…

Left untreated, tooth root abscesses can lead to sinusitis, Boone said. The mare in this study had been diagnosed with a tooth root abscess in an upper cheek tooth (first molar), and the attending veterinarian recommended extraction. However, due to several extenuating circumstances, the extraction was delayed for a year.

“It’s not uncommon for treatment of dental disease to be delayed for a variety of reasons,” she explained.

During the one-year wait, the mare developed an intermittent foul-smelling discharge from the right nostril and was reported to shake her head occasionally. Otherwise, she seemed healthy.

… Then Meningitis

Because the mare’s case had become complicated with the chronic sinus infection, she was sent to Auburn University’s referral hospital for surgery. There, Boone and his colleagues performed diagnostics that confirmed an infection of the infected upper cheek tooth and right sinus, but also identified a sinus infection with a suspected infected upper cheek tooth on the side. left. They removed the affected upper right molar using a device (maxilla). After the extraction, they inserted catheters into the left and right sinuses for lavage (rinsing).

About 24 hours later, the mare developed a racing heartbeat and lost her appetite, Boone said. Veterinarians have postponed removal of the affected upper left cheek tooth until his clinical condition improves.

Two days later, the mare developed a fever, and over the next few days she became stiff in her neck. Her fever rose to nearly 105 degrees F despite treatment with anti-inflammatories and antibiotics, she said. Because fever and stiff neck made Boone suspect meningitis, she and her colleagues performed a lumbar puncture on the horse; the results of the cerebrospinal fluid analysis confirmed his suspicions.

They treated the mare “aggressively,” she said, with broad-spectrum antibiotics that can cross the blood-brain barrier, a protective membrane around the brain that blocks many types of drugs. They prevented further inflammation of the meninges by treating the mare with corticosteroids and anti-inflammatory drugs.

Beat the odds against a deadly disease

The mare’s vets knew her chances of survival were not favorable, Boone said. Previous studies of meningitis in horses after dental or sinus surgery have painted a grim picture: all reported cases have died or been euthanized.

Yet in this case, the mare got away with it, she says. Her fever dropped within 12 hours of targeted therapy. Within a week, she had fully recovered to the point that vets could extract the affected upper molar as planned.

“To our knowledge, this is the only report in the literature of a horse surviving with acquired bacterial meningitis after cheek extraction and sinus surgery,” Boone said. “(We) believe that early recognition of clinical signs, diagnosis and treatment aided survival.”

Other factors related to the type and amount of bacteria that invaded the meninges as well as the overall health of the mare could have resulted in a milder case of meningitis than previously reported cases.

“This horse had no neurological deficits on neurological examination, other than dull mentation, and it can be inferred that this was a mild case of bacterial meningitis,” she said. “But without proper treatment, his clinical signs would have rapidly progressed.”

Meningitis after dental/sinus surgery

It’s unclear why some horses develop bacterial meningitis after dental and/or sinus surgery, Boone said. In complicated cases like this, bacteria from the mouth and sinuses find their way into the meninges either by disrupting the bone plate in the sinus that protects the meninges, or via the bloodstream or cranial nerves, a-t -she explains.

“It’s important to recognize that complications can and do occur with the treatment of complicated dental and sinus disease,” Boone said. Horse. “Although meningitis is rare, veterinarians should be aware of the clinical features associated with meningitis such as post-extraction fever, tachycardia (rapid heartbeat), neck pain, and changes in neurological status. The risk of meningitis is extremely low, but if it does occur it is often fatal to the horse.

The Bottom Line: Dental Care Shouldn’t Wait

A good way to reduce risk is to manage dental disease early, without waiting for it to become more advanced and complex, Boone said.

“What is most important is that dental diseases are recognized early and treated appropriately to resolve,” she said. “It starts with the owner.

“It is imperative that owners recognize that veterinarians should be the professionals who assess their horse’s health and provide preventative health services,” she continued. “Maintaining dental health is vital to the overall health of your horse. This is why an annual to six-monthly dental check-up is recommended and should be performed by your veterinarian – and only your veterinarian.

Homeowners need to understand that delaying the cost of dental care could end up making the situation not only riskier, but much more expensive, she added.

“Resolving chronic dental and sinus disease can be difficult, and sometimes it’s best to make the initial investment, if possible, for a quick and aggressive resolution,” Boone said. “In my opinion, often the ‘cheaper’ treatment just prolongs the disease process because it ‘covers’ it rather than solving the problem at hand, and it makes things more complicated and more expensive to long term.”

Meningitis after tooth extraction and sinus lavage in a horse was published in the Journal of Equine Veterinary Science in 2021.