In recent years, monoclonal antibodies have been approved to treat some common medical conditions in animals:

• Allergic itch in dogs (Cytopoint, Zoetis)
• Osteoarthritis pain in cats (Solensia, Zoetis)
• Osteoarthritis pain in dogs (Librela, Zoetis)
• Parvovirus infection in dogs (Canine Parvovirus Monoclonal Antibody, Elanco)

 
More monoclonal antibodies are likely to become available for dogs and cats. Monoclonal antibodies are used in humans to treat infections, autoimmune disorders, cancer, and other conditions, and they’re being investigated for similar uses in dogs and cats.
 
How Monoclonal Antibodies Work
Monoclonal antibodies are in a therapy class called biologics, meaning therapies made from living sources like animal cells, plant cells, or microorganisms. Biologics are large molecules that interact with receptors on the outer surfaces of cells; they don’t enter cells. In contrast, most traditional drugs are small molecules that work inside cells.
 
Monoclonal antibodies are similar to the natural antibodies produced by the immune system. When the immune system detects an antigen, different immune cells release lots of different antibodies that tag different sites on that antigen. (An antigen is anything that triggers an immune response.) Once the antibodies have tagged the antigen, other components of the immune system arrive to destroy it.
 
Monoclonal antibodies are cloned in a laboratory from just one antibody made by one type of immune cell (mono means “one”). They tag only a single site on an antigen. Monoclonal antibody therapy can be very precise because it directs the immune response to a narrow target.
 
In addition to tagging invaders like viruses, monoclonal antibodies can be engineered to tag a receptor on an animal’s own cells. The monoclonal antibodies that relieve pain in dogs and cats, for example, block production of a protein that’s partly responsible for the pain sensation.
 
After monoclonal antibodies have activated the immune system, they’re broken down in the body the same way that natural antibodies are. Unlike small-molecule drugs that enter an animal’s cells, they aren’t cleared through the liver or kidneys.
 
Administration
Monoclonal antibodies are given by injection at a veterinary clinic. They can’t be given by mouth because they’re proteins and would be destroyed by digestion. Their effect lasts a few weeks (4-8 weeks for Cytopoint, 4 weeks for Solensia and Librela). These therapies are species specific: monoclonal antibodies for dogs work only for dogs, not for cats.  
 
Benefits
The monoclonal antibodies that are available for dogs and cats generally work well for their approved uses. They are less likely than some traditional drugs to cause adverse effects because they have a narrow target of action and don’t enter cells. Because they are not cleared through the liver or kidneys, they can be safer than other drugs for animals with liver or kidney disease. Injections given every few weeks might be more convenient for pet owners than pills given multiple times a day, especially if their pets resist oral medication.
 
Adverse Effects
Monoclonal antibodies have fewer adverse effects than many traditional drugs. An antibody injection can cause an allergic reaction, although this is rare. Manufacturers might recommend precautions for individual monoclonal antibody products.
 
Image source: https://unsplash.com/photos/a-dog-wearing-a-baseball-glove-E3K7xyAvQ8M

Vestibular disorders cause problems with balance and coordination. Animals with vestibular disorders typically have a head tilt along with stumbling, walking in circles, and possibly vomiting.
 
Vestibular problems that start suddenly can look scary to pet owners. The signs can be mistaken for stroke. Some conditions that cause vestibular problems are serious, even life-threatening; others are relatively minor.
 
One of the most common vestibular disorders in dogs is a benign condition called idiopathic vestibular syndrome (idiopathic means “of unknown cause”). This condition is not serious and gets better on its own with time. Idiopathic vestibular syndrome most often affects senior dogs, so in dogs it’s also known as old dog vestibular disease. Cats can also develop idiopathic vestibular syndrome.
 
Causes
The vestibular system includes the brainstem, cerebellum (part of the brain), inner ear, and nerves that conduct signals between the inner ear and brain. Anything that affects any part of this system can cause vestibular signs.
 
Vestibular disorders are either central (related to the brainstem and cerebellum) or peripheral (related to the inner ear and surrounding nerves). Central vestibular disorders are usually much more worrisome than peripheral vestibular disorders.
 
Idiopathic vestibular syndrome is a peripheral vestibular disorder. The exact cause in dogs isn’t known. Similar conditions in humans are caused by inflammation of the inner ear or surrounding nerves, viral infections, and benign positional vertigo (an inner ear problem). These same causes are possible but not proven in dogs.
 
Some of the other causes of vestibular disease in animals are deep ear infections (common), cancer, drug adverse effects, toxins, systemic disorders like hypothyroidism, meningitis, and other neurologic disorders.
 
Signs
These are the typical signs of a vestibular disorder:

• Head tilted to one side
• Stumbling
• Falling over
• Walking in circles
• Eyeballs flicking rapidly from side to side or up and down
• Vomiting (motion sickness from the rapid eye movements)

 
Idiopathic vestibular syndrome usually affects older dogs and cats. It begins suddenly and then starts to improve within a few days. The signs are most pronounced on the first day and don’t get worse with time. In most animals, the signs disappear after a couple of weeks, although the head tilt can last much longer.
 
Other diseases that affect the vestibular system cause signs of their own. For example, a central vestibular disorder might cause seizures or changes in consciousness. Vestibular signs that get worse with time are a signal that the animal has something other than idiopathic vestibular syndrome.
 
Diagnosis
Idiopathic vestibular syndrome is a diagnosis of exclusion: it’s diagnosed after other possibilities are ruled out. Diagnosis begins with a neurologic examination, eye and ear examinations, baseline bloodwork, and usually a thyroid function test and urinalysis. Depending on the results, the animal might need referral to a veterinary neurologist and advanced tests like magnetic resonance imaging of the head or cerebrospinal fluid analysis. 
 
Treatment
For idiopathic vestibular syndrome, the goal of treatment is to make the patient comfortable until the condition resolves on its own. Most animals receive prescription antinausea medication; some also need appetite stimulants or fluid therapy. Home care includes making sure they can eat and drink and protecting them from falling down steps or bumping into things like furniture corners. Physical therapy and postural maneuvers that are used to help people with vertigo aren’t commonly used in animals.
 
Prognosis
Most animals with idiopathic vestibular syndrome recover completely, although some have a permanent head tilt afterward. Some animals have more vestibular episodes later on. For vestibular signs that aren’t caused by idiopathic vestibular syndrome, the prognosis depends on whether the cause is treatable.
 
Sources

• Mertens AM, Schenk HC, Volk HA. Current definition, diagnosis, and treatment of canine and feline idiopathic vestibular syndrome. Front Vet Sci. 2023;10:1263976. doi:10.3389/fvets.2023.1263976
• Michaels J. Acute vestibular disease in old dogs. MSPCA Angell. Accessed February 1, 2024. https://www.mspca.org/angell_services/acute-vestibular-disease-in-old-dogs/
• Orlandi R, Gutierrez-Quintana R, Carletti B, et al. Clinical signs, MRI findings and outcome in dogs with peripheral vestibular disease: a retrospective study. BMC Vet Res. 2020;16(1):159. doi:10.1186/s12917-020-02366-8

 
Image source: https://unsplash.com/photos/brown-and-black-german-shepherd-Xy7SLX9zuVM