Wednesday, September 20, 2017

Health Spotlight: Feline Uveitis

Photo: Staci Machado

Health Spotlight: Feline Uveitis

A recent Facebook post to the CatCentric group devoted to healthy cats described the poster's cat's diagnosis as lymphocytic plasmacytic uveitis. The kitty is pictured above. She couldn't find anything on this condition and asked for help, so here's what I discovered upon researching it.

What is Uveitis?

Uveitis is a medical term for inflammation of the middle layer of the eyeball, which is known as the uvea. This portion of the eye contains a large number of blood vessels that nourish your cat's eyes. Uveitis is not a disease in and of itself, but a condition that can be symptomatic of injury or any number of diseases or other conditions.

Some cats who develop uveitis also develop glaucoma due to an imbalance of normal fluids (vitreous humor) inside the eyeball. The fluids are unable to drain as they usually would because of the inflammation, so they build up and create pressure in the eye.

What Causes Feline Uveitis?

Many things can cause the middle layer of the eyeball to become swollen. Several factors can increase a cat's likelihood of developing this condition:

  • Bodily infections, commonly of the lungs or central nervous system
  • Viruses, such as FHV-1, FeLV, or FIV
  • In cats under 2 years of age, feline infectious peritonitis (FIP)
  • Parasites, such as Toxoplasma gondii or Bartonella
  • Systemic inflammatory diseases, such as inflammatory bowel disease
  • Tumors or cancers
  • Allergies or immune system deficiencies
  • Living with smokers
  • Injury to the eye (uncommon cause) or corneal ulcers
  • Fungal infection (rare)

In most cases, the uveitis is caused by an infection of some type. The diagnosis given to the cat pictured above, "lymphocytic plasmacytic uveitis," indicated that the veterinarian was unable to identify the cause of the condition. Lymphocytes and plasmacytes are two types of white blood cells that are essential to the body's immune system. When the cause of uveitis is uncertain (idiopathic), lymphocytic plasmacytic uveitis is the diagnosis commonly used to describe it.

Many kittens in wild colonies or overcrowded conditions are exposed to FHV, the feline herpesvirus-1. This is a different type of herpes virus than the one that affects humans, and it is not transferrable between cats and humans. FHV often manifests in the eyes, respiratory and gastrointestinal tracts. Cats affected by FHV tend to sneeze a lot, have runny eyes, conjunctivitis (pink eyelids), and possibly have ulcers on the eyes, among many other symptoms. The uveitis is a secondary condition to the FHV infection. As with the type of herpes virus that infects humans, this one also remains dormant in the cat's system and may flare up again in times of stress.

FIV, the feline immunodeficiency virus, may be an underlying cause of uveitis in cats 5 years or older. These tend to be milder cases of uveitis, and you may not notice it until the secondary glaucoma develops. These cats' eyes may sometimes appear to have a cataract. In many cases, the uveitis will appear several months to years before the cat tests positive for the virus. FIV is controllable (although not curable at this time), and is no longer the fatal diagnosis it used to be; it can be managed and cats can live many happy years with it now.

The feline leukemia virus, FeLV, is a retrovirus that affects only about 2.3% of all cats. One of its effects is to cause a buildup of protein deposits in the middle coating of the eye, which shows up as the discoloration associated with uveitis.

Most kittens are exposed to the feline calicivirus and will show respiratory symptoms. They may develop corneal ulcers as a result. This can cause them to experience some uveitis. While cats of any age may get this virus, it is more common in kittens.

In cats with full-blown FIP, several of the kitty's organs (kidneys, liver, spleen, lungs) and even the central nervous system are affected by the disease. The uveitis is only one component to the infection that is wracking the entire bodies of these poor cats. Although research continues on a cure or vaccine for FIP, it is often still a fatal diagnosis as of this writing.

When caused by Toxoplasma gondii, or toxoplasmosis, the cat may have a pulmonary (lung) or central nervous system infection in addition to the uveitis. In these cats, the uveitis may be ongoing and the cat's immune system may become suppressed.

Older cats may develop uveitis when an underlying cause cannot be determined. This is especially true for cats who have had a problem with uveitis in the past. This may affect one or both eyes, and often leads to glaucoma.

Lens luxation (displacement of the lens) is a condition that is rare, but more common among Siamese cats, especially aging ones. Uveitis may occur secondary to this condition.

Hyphaema is when blood cells accumulate in the front chamber of the eye. It is similar to uveitis, but has its own set of causes and symptoms.

Some cats with uveitis have tested positive for infection from Bartonella, a bacteria that causes what is commonly called "cat-scratch fever" when transmitted to humans. This type of bacteria lives in the lining of the blood vessels and is often spread by contact with flea feces. Cats may not show symptoms of infection from it other than mild fever, swollen glands, and slight muscle aches, so you may be completely unaware that your cat has this when you see symptoms of uveitis.

What are the Symptoms of Uveitis in Cats?

If your cat is experiencing uveitis, you may notice the following symptoms:

  • The cat's eye color may change (see photo above) due to fluid accumulation
  • The eye may appear red or swollen
  • The affected eye may produce a lot of tears
  • Kitty may squint or show sensitivity to bright light
  • The cat's pupil size and shape may change

Uveitis can be a painful condition. The tearing and squinting are indicative of pain. The cat's eye color may change all over, as in the photo above, or it may appear that a dark cloud is covering a portion of the eye. The discoloration comes from fluid building up in the eye, and is usually darker than the iris's natural color.

When your veterinarian examines the cat's eye internally, there may be several indicators that are not apparent by mere observation. When the vet shines a light into the cat's eye, the beam may scatter due to increased protein and inflammatory cells in the natural fluid within the eyeball (the aqueous humour). There may be nodular lesions or excess small blood vessels on the eye's iris. The blood vessels of the retina may be inflamed. These can only be seen with equipment in a vet's office that you do not likely have at home.

How is Feline Uveitis Treated?

This is not something you can treat by yourself at home. Take your cat to a veterinarian for a proper medical diagnosis and treatment. Rapid treatment of uveitis can save your cat's eyesight. If left untreated, it can result in blindness in the affected eye.

Corticosteroids can reduce inflammation and pain of the condition, and are still the most common treatment for uveitis. These may include prednisolone or dexamethasone. You will need to apply the medicine, usually as an ointment, to your cat's affected eye multiple times per day at first, slowing to only once or twice daily as the condition responds to treatment.

In severe cases, your vet may administer a corticosteroid underneath the surface of the cat's eye. This should only be done in rare instances when the swelling has affected the back portion of the eye, and the condition is not caused by an infection.

If the cat has a fungal infection that has affected the internal organs, kitty's prognosis is not good, although treatment with imidazole therapy has been documented. Luckily, fungal infections in cats are rare.

Depending on the cause, the underlying infection, disease, or condition must be treated to decrease the likelihood that the uveitis will reoccur. This may involve referral to a veterinarian specializing in feline oncology or rheumatology. In cases of FIP or FIV, there is no specific treatment currently available. For Bartonella, azithromycin has been used successfully.

While human uveitis can sometimes be treated by dilating the pupils to reduce inflammation, constriction of the feline pupil is not usually a problem in cats suffering from uveitis, so this is not a treatment used by veterinarians.

Is There Any Way to Prevent Feline Uveitis?

Not all the diseases that can cause uveitis are preventable. Sometimes, cats are exposed to pathogens before we take them in. If you adopt a new kitten or cat, have your veterinarian check out the kitty and give it a clean bill of health prior to introducing it to your other cats.

Cancer can occur in even the healthiest of cats. If the uveitis occurs as a side effect of a type of cancer, only your veterinary oncologist can help with treatment. There is no known prevention for cancer at this time.

Keeping your cat healthy and kitty's environment flea-free is the best defense against many of the diseases that may cause uveitis. Feeding quality food and supplementing with a good probiotic will support your cat's immune system and keep the body strong.

Treat your cat for fleas and vacuum often to keep your home free of fleas and ticks that may bring diseases like bartonellosis.

If you do see any discoloration in your cat's eye(s), seek a veterinarian's opinion first. With such a myriad range of causes, it's important to have proper testing done to see if anything can be done for the underlying condition causing it.

Sources: "Feline uveitis: aqueous flare intensity excellent clinical monitor" by Johnny D. Hoskins, DVM, PhD, DACVIM, Veterinary News dvm 360, September 1, 2005; "What is Uveitis?" by Kierstan Boyd and reviewed by Robert H. Janigian Jr. M.D., American Academy of Ophthalmology, March 1, 2017; "Cat Scratch Fever in Cats", Pet MD; "Anterior uveitis", Vetbook, "Feline Calicivirus Infection in Cats", Pet MD.


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