Corneal ulcers
Conjunctivitis means a reddening (inflammation) of the pink tissue (conjunctiva) around the eyeball itself. There is a difference between inflammation and infection of the conjunctiva. Both are described as conjunctivitis as infection always causes inflammation, but the opposite is not always the case.
The causes of Conjunctivitis vary among different species, so a detailed review of causes of conjunctivitis in different animals is given below.
cats, dogs, rabbits, guinea pigs, exotic animals.
Conjunctivitis in the cat is most commonly associated with signs of Cat Flu, often caused by Cat Herpes Virus (FHV-1) or Chlamydia. Other Possibilities of conjunctivitis in the cat include true primary infections (secondary to scratching/fights/accidents), infections of the tear duct , tear disorders, eyelid disorders or eye-lash problems.
Cat Herpes Virus is similar to human Herpes Simplex that causes "cold sores" around the edges of the lips in people. As in human Herpes Simplex, Cat Herpes Virus will be dormant in nerves, when not causing any disease. Any period of immuno-supression (systemic illnesses, colds, infections, pregnancy, etc.) may spike off a reactivation of the Herpes and cause conjunctivitis.
Possibilities of diagnosis of Cat Herpes Virus include:
Culture: a swab or scraping is taken from the conjunctiva and throat of the cat. A positive culture result is a clear indication of the cat being infected with Cat Herpes Virus.
DNA testing: A swab or scraping is taken from the conjunctiva and sent of to look for DNA (genetic) evidence of active or previous herpes virus infection or chlamydial infection.
In dogs conjunctivitis may be caused by a number of reasons. Tear film disease is by far the most common cause of conjunctivitis in the dog (see this separate page).
Bacterial infections of the conjunctiva usually occur secondary to trauma, tear deficiency or infections of the tear duct. If tear disorders are excluded and the conjunctivitis is not responding to simple antibiotic drops further investigations such are tear duct probing and conjunctival biopsies are indicated.
Allergic conjunctivitis is a poorly recognised disease in the dog. I find many dogs with systemic allergies have signs of ocular irritation as well. Is allergic conjunctivitis is strongly suspected referral to a skin specialist (Dermatologist) is usually the next step.
In rabbits conjunctivitis is most often secondary to an infection of the lacrimal duct, that connects the corner of the eye to the nose. In rabbits this duct is very narrow at certain locations and may block, causing the eye to water, as tears produced then have to drain over the lower eyelid spilling onto the face. In some rabbits this problem is corrected after flushing the lacrimal duct and using topical antibiotics and/or steroids. In other rabbits the problem is linked to swelling of roots of cheek teeth very close to the lacrimal duct. An x-ray may be necessary in order to determine which tooth roots are causing the problem. As a result of the investigation teeth may need to be extracted.
Resent research suggests the roots of the incisors may be damaged during the first months of age due to deficiencies of vitamin D and Calcium in the diet. It is therefore advisable to only feed diets such as Excel Rabbit. Other diets have pellets containing vitamins and minerals. Rabbits may decide not to eat these pellets and thus cause the deficiency.
Conjunctivitis in the rabbit may also be caused by myxomatosis or infections of the upper airways. These conditions can be very dangerous for the rabbit and the conjunctivitis may be the only signs noticed immediately by the owner. Eyelid diseases such as in-rolling eyelids (entropion) may cause secondary corneal irritation and/or conjunctivitis.
In guinea pigs conjunctivitis may be a signs of an infection of the upper airways. Therefore your veterinary surgeon may want to use a systemic antibiotic as well as a topical antibiotic in the treatment of your guinea pig.
It is important not to use straw but only hay as feed. Straw may become lodged in the conjunctiva where it can rub against the cornea resulting in corneal ulcers. If your guinea pig is showing other signs of disease besides the conjunctivitis, your vet may chose to put your pet on a supplement of vitamin C, as sufficient vitamin C is very important for the recovery of your pet.
Some guinea pigs have rolling-in of the eyelids (entropion). Some guinea pigs are born with this defect and the entropion causes corneal and conjunctival irritation. A tear substitute may alleviate signs of ocular discomfort. If the entropion is not corrected naturally as the guinea pig grows an operation can correct the defect.
Conjunctivitis in birds and reptiles may be caused by a number of bacterial and viral pathogens. Most commonly a topical fluoroquilonone antibiotic is used in the first instance and if the disease is not responding, blood testing, bacterial culture and biopsies of the conjunctiva are indicated.
This section of mammaleye.com is written for Owner's of patients under my care and treatment. Others may of cause gain knowledge about eye diseases in pets. Remember that other veterinary ophthalmologists may wish to treat diseases of the eye in a different way than myself.
If you as an owner want further information (scientific) about eye diseases then have a look at www.mammaleye.com/prof.htm or go to pubmed and do a search on Medline - the main resource of scientific information for the whole medical profession.
