Conjunctivitis is a common inflammation of the conjunctiva, the thin mucous membrane lining the inner surface of the eyelids and coating the eyeball. Many cats will experience this condition, often called pink eye, at some point in their lives. The inflammation results in noticeable symptoms such as redness, swelling, and a discharge that can range from clear and watery to thick and dark-colored. When a pet exhibits signs of eye discomfort, owners naturally worry about the cat’s health and potential risks to their own.
Is Feline Conjunctivitis Zoonotic?
Feline conjunctivitis is generally not transmissible to humans because the pathogens involved are highly species-specific. The term “zoonotic” refers to diseases that pass from animals to humans, but the organisms causing cat pink eye are adapted specifically to the feline host. The viral and bacterial agents that commonly affect a cat’s eyes do not easily infect human tissue or cause disease in people.
It is incredibly rare for a human to contract conjunctivitis directly from a cat. There is a specific bacterial exception involving Chlamydophila felis, documented in isolated human cases. This bacterium is an uncommon cause of follicular conjunctivitis in humans who have had direct contact with an infected cat’s ocular secretions. Practicing basic hygiene when caring for a sick cat significantly mitigates this minimal zoonotic risk.
Common Root Causes in Cats
Feline conjunctivitis is most frequently caused by infectious agents, particularly viruses targeting the upper respiratory system. The most common culprit is Feline Herpesvirus-1 (FHV-1), responsible for a large percentage of cases, especially those that are chronic or recurrent. Once infected, FHV-1 remains dormant in the nervous system and can reactivate during times of stress or illness, leading to flare-ups of conjunctivitis.
Bacteria are also a common factor, either as a primary cause or secondary infection following a viral illness. Primary bacterial pathogens include Chlamydophila felis and Mycoplasma, which produce a noticeable yellow or green ocular discharge. These microorganisms are well-adapted to the feline environment, reinforcing why they rarely pose a threat to human health.
Non-infectious causes also contribute significantly to eye irritation in cats. These include environmental irritants like dust, smoke, or airborne chemicals, which can trigger an allergic reaction. Anatomical issues, such as entropion (where the eyelid rolls inward), can cause the lashes to constantly rub against the cornea, leading to chronic inflammation.
Human Conjunctivitis and Cross-Contamination
Conjunctivitis in humans is typically caused by human-specific pathogens, most frequently the highly contagious Adenovirus, or by bacteria like Staphylococci or Streptococci. Allergic conjunctivitis is also common, triggered by environmental factors like pollen or pet dander. The lack of overlap between the common causes in the two species underscores why transmission is not a major concern.
The primary risk of cross-contamination involves poor hygiene practices. This could potentially transfer bacteria or viruses from the cat’s eye to a person’s eye, causing irritation rather than a species-specific infection. Touching an infected cat’s eye discharge and then touching one’s own eye without washing hands can transfer matter that may cause inflammation or introduce secondary bacteria.
When administering eye medication or cleaning discharge, wash your hands thoroughly afterward with soap and water. Avoid sharing towels, bedding, or other materials that have come into contact with the cat’s face. Maintaining good hygiene prevents the accidental transfer of bacteria and reduces the risk of spreading infectious agents to other household pets.
Diagnosis and Treatment for Your Cat
If a cat shows signs of conjunctivitis, a veterinary visit is necessary to determine the underlying cause and ensure the inflammation is not a symptom of a more serious eye condition. The diagnostic process begins with a thorough eye examination, often using an ophthalmoscope. Several specific tests may be performed to pinpoint the issue.
The fluorescein stain test involves applying an orange dye to the eye to detect corneal ulcers or scratches contributing to the irritation. A Schirmer tear test measures the cat’s tear production to rule out conditions like dry eye. To identify the specific infectious agent, a swab of the eye discharge may be taken for cytology or a Polymerase Chain Reaction (PCR) test to look for pathogens like Feline Herpesvirus-1 or Chlamydophila felis.
Treatment is always tailored to the diagnosis. If a bacterial infection is suspected, topical antibiotic eye drops or ointments, such as those containing tetracycline, are prescribed. Cases caused by Feline Herpesvirus-1 may require topical or oral antiviral medications, such as famciclovir, especially in severe or recurrent instances. Anti-inflammatory drugs may also be used to reduce swelling, and any underlying issues like entropion or foreign bodies must be addressed for resolution.