HERPES VIRAL CONJUCTIVITIS (FELINE)
HERPES VIRAL CONJUNCTIVITIS
The conjunctival membranes of the eye are basically the “pink part” under the eyelids and the lining of the eyelids themselves. When they are irritated, they redden and can become itchy, dry, and uncomfortable. The cornea, or clear dome-like covering of the eye can become involved in the inflammation. It can become cloudy or even ulcerated. Tear production can be reduced leading to a chronic dry, uncomfortable eye.
Conjunctivitis in cats is usually of viral origin and usually that means a herpesvirus (feline herpesvirus-1 to be specific) infection. Herpesviruses grow in the tissues of the body that interface with the environment, such as the upper respiratory tissues and conjunctivae. The infection begins with an initial phase which is usually the most severe in terms of symptoms. This phase resolves but the virus itself does not go away; instead, it retreats into the trigeminal ganglion (a neurologic structure in the head) where the patient’s immune system holds it prisoner. In times of stress, the immune system is taxed and the virus is able to escape from the ganglion, traveling out via the nerves exiting the ganglion and leading to return of symptoms. In this way, the infection is permanent but the symptoms of the infections come and go.
BABY KITTENS: A SPECIAL SITUATION
In severe cases, the eye can rupture and become permanently blinded. Treatment is crucial and response to topical therapy is usually dramatic.
Herpes infection typically causes respiratory signs as well: snotty nose, congestion, etc. These signs can result in life-threatening loss of appetite and dehydration in a young kitten, while signs are generally minor in an adult cat whose immune system is mature. Kittens with obvious discomfort should be examined by a veterinarian. Oral antibiotics will most likely be needed and sometimes hospitalization is also necessary for proper supportive care.
Since kittens are so commonly affected with herpes, it is not unusual to find oneself in possession of an adult cat with a history of herpes infection. These individuals will have recurring conjunctivitis in times of stress. Typical signs include squinting slightly in one eye, a noticeable increase in ocular discharge (usually brownish in color), redness of the conjunctivae, or all of the above.
HOW DO WE KNOW IT IS HERPES?
There is only one test that is accurate enough to be worth doing if one wants to know for sure if Herpes is present or not and that is the PCR (“Polymerase Chain Reaction”) test. This is a DNA test that amplifies the presence of viral DNA so that even one single virus can be detected in a sample from a conjunctival swab. The extreme sensitivity of this test has made it somewhat problematic for laboratories to run. Prior to PCR technology, serum antibody levels were run but widespread vaccination against herpes has made these results difficult to interpret. At this point, the clinical presentation of the patient is what leads to the diagnosis of herpes in most cases.
HOW CAN WE TREAT IT?
There are several treatment methods that can be combined in the treatment of feline herpes eye infections:
It should probably be noted that some infections lend themselves to prevention by the vaccination process and others do not. Herpes rather does not. This means that vaccination of healthy cats does not prevent infection for feline herpes; what it does do is lead to less severe signs. Vaccination against feline herpes has been deemed helpful but one should understand that, in this case, the goal is not total prevention of infection but palliation.
CAN HUMANS GET FELINE HERPES? CAN CATS GET HUMAN HERPES?
Happily, humans and cats cannot share their herpes viruses. Feline herpes is contagious among cats only and human herpes is contagious among humans only.
Page last updated: 1/8/10