Interview with an Expert: Herpes Eye Infections in Cats
Recognizing, treating and preventing herpes eye infections in your cat.
Fiona, a Scottish Fold and one of our five cats, has had eye problems since she was a kitten. She was diagnosed with the herpes virus two years ago, and after some treatment was fine for over a year. Recently I noticed that she was blinking and squinting on a regular basis, so I took her back to the vet. We talked through a range of possibilities before the doctor decided that she was again suffering from symptoms caused by the virus.
Thankfully, Fiona is doing very well after a number of weeks on special eye drops. To learn more about this feline condition, I contacted Dr. Daniel J. Biros DVM, DACVO, a board-certified ophthalmologist at Angell Animal Medical Center in Boston. Below is some information he shared about herpes eye infections in cats.
Care.com: What exactly is a herpes virus eye infection, and how prevalent is it in kittens and cats?
Dr. Biros: Feline ocular herpesvirus, or FHV-1, is a very common virus in cats. While it is thought that most cats (over 90 percent) harbor the virus, only a small percentage of cats actually show clinical disease. These cats are usually immunosuppressed from stress or disease, or they may harbor a more virulent strain of the virus.
Care.com: Is it true that pure-bred cats born in catteries are more likely to have these infections?
Dr. Biros: To my knowledge there is no breed predisposition to cats with FHV-1. Catteries often have problems with FHV-1 due to a high level of cat-to-cat contact, thereby creating the greater likelihood of pathogen transmission.
Care.com: What are the symptoms?
Dr. Biros: Clinical signs are variable and may be mild to severe. Mild squinting, runny eyes, and conjunctivitis are mild generalized ocular signs consistent with FHV-1. More severe signs may involve changes in the cornea such as cloudiness or redness. In severe cases there may be vision impairment, a marked increase in tearing, and squinting. Ocular herpes can be very painful and if untreated could lead to vision loss or loss of the eye in the most severe infections. There may also be upper respiratory signs, such as a runny nose, sneezing, or nasal surface ulceration.
Care.com: How is it determined that a cat has the virus?
Dr. Biros: Diagnostic tests are difficult at best to determine if a cat has FHV-1. A fresh and properly prepared sample of the cat's conjunctival or corneal cells may yield evidence of virus based on a molecular screening test called a PCR (polymerase chain reaction). Viral cultures are rarely done and not necessarily practical in a clinical setting. Most cats are treated based on the history and clinical signs. Often if a superficial linear, or dendritic (branching or lightning bolt shaped), corneal ulcer is noted on the clinical examination, there is a high likelihood of FHV-1 being present. Ulcers on the cornea if present are not exclusively linear and may be geographic, covering a variable area of the corneal surface.
Care.com: Once a cat is infected, is the condition ever cured?
Dr. Biros: There is no cure for herpes virus. It can be driven into remission but never cured.
Care.com: We had a cat that was diagnosed with this condition, but at one point the veterinarian was having trouble distinguishing between symptoms of the herpes virus and a possible allergy or bacterial infection. Is there a difference between the symptoms?
Dr. Biros:: Not always. The symptoms are often similar. Chronic ocular surface inflammation from one cause or another can appear very similar. In severe cases, herpes infections may also acquire a bacterial or dry eye component complicating the situation and causing more damage to the ocular surface.
Care.com: What are the treatment options for a herpes virus eye infection, and does treatment have to be long-term?
Dr. Biros: Treatment is usually a combination of medicine to address the virus specifically, medicine to provide lubrication and antibacterial protection, and in some cases, medicine to manage the pain of the outbreak. Usually there is a combination of oral and topical medication. Surgery to repair a damaged eye is indicated only in the most severe cases. Treatment is often long-term, and for most cats is recommended up to two weeks beyond resolution of clinical signs. When to stop or change treatment should be left up to the veterinarian managing the disease.
Care.com: When giving a cat eye drops, is there anything important to know about how to give the drops or keeping the drop bottle clean?
Dr. Biros: Most eye medication is sterile when opened, but once opened the tip of the bottle is likely to get contaminated at some point. Avoiding contact with fingers, the ocular surface or eyelids when applying the medication will reduce the risk of dirtying the tip of the bottle or tube. Often if you can point the cat's nose to the ceiling and then spread the eyelids open it is easier to apply drops. Ointments can be best applied between the inside of the lower eyelid and the ocular surface or on the top of the eye after manually raising the upper eyelid. There is no specific proper way to deliver the medication, often it is whatever works best for a given cat and client.
Care.com: Is the condition contagious between cats, or between cats and humans or other species?
Dr. Biros: None of the common infectious ocular surface diseases in cats can be passed to other species including humans and vice-versa. On the other hand, cats can easily spread FHV-1 to other cats through nasal and ocular secretions, especially during an outbreak.
Care.com: Are there preventive measures that can be taken to either avoid infection in the first place, or recurrence of symptoms after treatment?
Dr. Biros: A low-stress environment, good nutrition and health, and in some cases, some degree of ongoing medication can all contribute to reducing or altogether eliminating outbreaks.
Care.com: Where can cat lovers learn more about this condition?
Dr. Biros: Your primary care veterinarian can provide you with more detailed information on FHV-1. The internet can also be a good resource for additional help on the topic. Specifically, Web sites that are linked to veterinary ophthalmology practices will provide the most helpful tips and information.
It's good to know our little Fiona has a condition that, although life long, can be managed. Hopefully we can avoid any future outbreaks -- but we'll be "keeping an eye on her" for any future symptoms!
Faye Rapoport DesPres writes about pet care issues for Care.com and other publications. She has five cats and a website at ourplacetopaws.com.