FHV is the leading cause of upper respiratory disease in felines and the most common cause of conjunctivitis.
When I was a teen, my part-time job was working on a farm that grew plants and flowers for resale to the public. The family that I worked for had quite an operation with seven greenhouses on a large piece of property and a humble but quite popular flower shop next to their big red farmhouse.
Walking the property were chickens and geese, and of course a growing population of barn cats that patrolled the property like a team of security guards protecting the vulnerable plants from rodent invaders. There were always kittens being born and some would stay to join the ranks, while others would be adopted out to loving families.
I would notice that many of the kittens and some of the adult cats would sometimes get an illness that the farmers would call a “cold in the eye.” They clearly had some type of respiratory infection that sometimes required treatment by the local vet while others would tough it out and survive, and a few would inevitably succumb to the infection. They would cough and sneeze and their eyes and nose would become encrusted with the remnants of what was being discharged by the infection.
It wasn’t until I was an adult that I learned what those farm cats were most likely suffering from was feline herpes virus, commonly called FHV. The fact is, it’s estimated that about 85% of cats have FHV and remain a carrier for life.
But why is it such a problem if it’s so common?
Feline herpes virus (FHV) has the clinical name of feline viral rhinotracheitis (FVR) and is a highly infectious disease caused by feline herpesvirus type-1. Just like other types of herpes virus, this virus is species specific and is only known to cause an infection in domestic and wild species of felines. It can infect any feline at any age and once infected, the cat is a carrier for life. The virus is the leading cause of upper respiratory disease in felines and the most common cause of conjunctivitis. Conjunctivitis is an infection that causes inflammation of the tissues surrounding the eyes including the lids and third eyelid.
FHV is an extremely contagious virus that is spread through direct contact between an infected cat and other cats by way of virus particles being transmitted through saliva, as well as discharge from the eyes and nose of an infected cat. The virus can also be spread when a susceptible cat comes into contact with items that have been contaminated by an infected cat. Items can include food and water bowls, bedding, toys, furniture and even a human’s clothing.
Once infected with the virus, the cat will usually begin to show symptoms within five days as this is the typical incubation period of the virus in a new host. During this incubation period, the newly-infected cat is highly contagious and is usually actively shedding the virus. Once the cat begins to display symptoms, the active infection can last as long as three weeks during which time the cat is still contagious.
After the infection clears, the virus goes into a latent phase, meaning the virus remains in the cat’s system in an inactive form. The cat is then a carrier of the virus but is no longer shedding the virus, and is most likely not spreading it to other cats—although some cats that are asymptomatic can still be actively spreading the virus. However, since the virus is incurable and remains within a cat’s body for life, it is important to note that during periods of stress or illness the virus can be reactivated and symptoms can reoccur. If this reactivation does happen, the cat is actively shedding the virus and becomes a spreader once again, which is why this virus is so widespread and common among feral cat populations.
Another common way in which infection occurs is from mother to kitten. The most vulnerable to infection are young cats and kittens. When a kitten is born to a mother with a latent infection, the physical stress of birth and kitten rearing can cause the virus to reactivate within the mother and she will shed the virus. The fragile, underdeveloped immune systems of the newborn kittens are not strong enough to fight off severe infection which is why the vast majority of street cats become infected at an early age.
There is also a high infection rate among purebred kittens from breeders as well. Once a cattery is infected with FHV, it spreads rather quickly and there can be a high mortality rate among those kittens that are severely infected. Some breeders will even advertise that their cattery is a herpes-free cattery, meaning that they have screened new cats for the virus and have worked hard to avoid it within their breeding program.
Diagnosis of this viral infection can be tricky because the symptoms are similar to several other respiratory infections. Veterinarians will use a combination of the pet’s medical history, clinical signs and physical examination to make the determination of FHV. Some of the symptoms include sneezing, respiratory congestion, discharge from the eyes and nose, frequent blinking and squinting, and conjunctivitis.
The eyes can also develop keratitis, a condition that causes inflammation and infection of the cornea leading to linear ulcerations on the surface of the cornea. These linear ulcerations resemble the lines of a tree branch and can be seen by staining the eye with fluorescein dye and using a light to fluoresce the stain. Any ulcerations will absorb the dye and glow so they’re easily identified. In severe cases or in untreated infections, the ulcerations can cause permanent scaring of the cornea.
FHV is typically treated symptomatically and varies depending on the clinical signs each individual cat is displaying. Respiratory infections are normally treated with antibiotics, while infections of the eye will be treated with topical eye medications. Severe cases may require more aggressive treatments.
While there is no cure for feline herpes virus, most cats respond well to treatment and can live a normal life. Some cats may experience periodic recurrences of the infection during times of stress or illness, but symptoms are typically mild. A diagnosis of FHV can be upsetting and scary but it’s not the end of the world. The key to keeping a cat healthy after an FHV infection is a healthy diet, a low-stress environment and of course lots and lots of affection. ✂️