Cat Flu-Herpesvirus, FCV, or something else?

The term “cat flu” can mean different things to different people- and veterinarians. It covers everything from simple coughing and sneezing to life-threatening mouth ulcers and everything in between. In this article, we are going to help you sift through the confusion, as well as how you can help your cat through these inevitable seasonal changes. We’ve got you and your cats covered!

This is a helpful breakdown from Trudell Animal Health:

“Feline herpesvirus (FHV-1) and feline calicivirus (FCV) are the most common causes of cat flu, accounting for about 90% of upper respiratory infections in cats. Other causes of cat flu include:

• Mycoplasma

• Bordetella

• Feline chlamydiosis

All cats are susceptible to these infections, however they are more common in catteries and shelters where cats are in close quarters with each other, except for FCV. Once a cat is infected, they can spread it to other cats directly (through saliva and nasal/eye secretions), or indirectly with shared food bowls, toys, beds, or even human hands.^”

While the above is true, it’s important to note that Feline Calicivirus (FCV) exists in the gut of about 35% of all cats. It is passed down to kittens from Mom and/or Dad. So while it is contagious, FCV is not easily spread from sneezing alone. This also means it cannot be prevented. It also gets commonly mis-diagnosed as Feline Herpesvirus (FHV-1) in the beginning. FHV-1 IS spread via sneezing, and is frequently seen in persistent, frequent coughing and sneezing. There may be one red eye or swollen eye. While FHV-1 can be dangerous in kittens, it’s not usually too serious. FCV, on the other hand, can be fatal, mostly due to the pain that comes from not being able to eat or drink. Let’s break these down a little more and show you what to look for and what to do about it.

Cat Flu #1: Feline herpesvirus (FHV-1)

Kittens are usually the ones most greatly impacted by FHV-1. Mom can provide immunity to it for the length of time babies are nursing, but that immunity wanes quickly as soon as kittens are taken from mom. Another reason to keep kittens with mom as long as possible!

What to look for: red eye or eyes (conjuctivitis), persistent sneezing, partially closed eye, goopy or wet eye (can be both but usually starts with one). The primary replication sites of FeHV-1 include the nose, throat, eyes, and upper trachea. Replication also takes place in tonsils and mandibular lymph nodes (swelling on the sides of the jaws).

Conventional Treatments: This is really important to understand about Feline Herpesvirus- using corticosteroids to treat it can actually make it worse, according to this NIH study quoted below. Do NOT use steroids to treat this viral infection- this means prednisolone and dexamethasone. They will make the infection spread. Also, the cat or kitten is not contagious when the infection is latent, another word for inactive. So low stress is the absolute best way to keep this virus from becoming activated in your cats and kittens and spreading it around.

Again, it is important to not- do NOT treat herpesvirus infections with steroids of any kind! There are many factors that contribute to the formation of a corneal sequestrum, most often occuring after a prior corneal ulcer or a chronic, nonhealing ulcer. A corneal sequestrum in cats is often associated with feline herpesvirus (FHV-1) infection.

Cats that are treated with topical corticosteroids are at risk of developing corneal ulcers and sequestra from activation of latent feline herpesvirus. Up to 50% of cats that appear clinically normal have feline herpesvirus present in their corneas.

Alternative Treatments: FHV-1 is a lifelong condition, no permanent treatment exists. However, it is possible to keep flare-ups to a minimum, without separating all the cats in a household or expensive drugs that will make it worse. Rebuilding the immune system will help in the long-term, and it can be done. Unfortunately, those who suffer the worst from this virus are often those who have experienced the most stress and least nutritional support. So rebuilding will take some time. Here is what we have found to be most helpful over time to slow the progression and spread of the virus, as well as duration.

Cat Flu #2: Feline Calicivirus (FCV)

While many instances of FCV may look like the image below, FCV does not always manifest by way of massive mouth ulcers. Many times, it shows up as a red mouth or gums- leading to a misdiagnosis of gingivitis or even FHV-1, as discussed above. By the time these mouth ulcers do appear, the cat or kitten is in bad shape, and likely in a lot of pain. For kittens, FCV is especially dangerous, as it is associated with Limping Calici, otherwise knows as '“fading kitten syndrome.” We wrote specifically about Limping Calici here for your reference.

Again, up to 35% of all kittens are born with FCV in their gut, so it is not spread in the same way as FHV, despite what conventional veterinary medicine suggests. If a cat or kitten has FCV in their gut and is put under stress of any kind- it can activate. This means shelters, rescues, spay/neuter, environment changes, poor diet, etc. Because these stressors are easily observed in multi-cat environments, it is assumed FCV is simply spreading. In truth, it is merely activating because of the environment the cat or kitten is living in.

What to look for (any one or more): deep red mouth, dark pink gum line, fever, lethargy, anemia (especially in kittens), darker spots on tongue or mouth

The problem with FCV vaccines- the creation of Virulent Systemic Feline Calicivirus

There is a recently emerging strain, called virulent systemic calicivirus, that causes very serious swelling of the face, ulcerative skin lesions and jaundice (yellowing of the skin and mucous membranes). This strain of calicivirus is very contagious, the risk of death is very high. It is important to note that this highly virulent strain did not exist prior to routine vaccination for FCV within the past 5-8 years. The latest vaccine contains two strains of FCV, which only allows for more mutation. It appears the vaccine is forcing the virus to mutate and become more virulent and aggressive. Please, please consider sparing your cat this vaccine. It may be contributing to truly deadly strains of this already serious virus.

Cat Flu #3-5: Mycoplasma, Bordetella, or Feline Chlamydiosis

These are more rare forms of what comprises the term “cat flu.”
Mycoplasma, otherwise known as feline infectious anemia or or hemobartonellosis (FHM) , is basically where a bacteria attacks the red blood cells. Anemia from this condition develops over time, and may not be readily diagnosed. For this condition, pale gums and jaundice are good indications your cat has a possible blood infection.

Because the organism can sometimes be found in normal cats, the mere detection of M. haemofelis does not confirm a diagnosis of FHM, and other possible causes of the anemia should not be overlooked. Your veterinarian may also recommend an FeLV/FIV test as these conditions are often common with FHM. Unfortunately, FIV and FeLV are more well-known, and diagnosis often stops after one of those tests returns positive. Conventional treatments include antibiotics, but in the case of FeLV or FIV, the antibiotics will not clear the infection due to the depressed immune system. Mycoplasmas are spread by direct contact in air and are not able to survive for long outside the host. As they are a fungus, antifungal agents like coconut oil or MCT oil may be of better long term benefit, as well as Humisol, as we have written about them here.

Bordetella, aka Kennel Cough in dogs and whooping cough in humans, are infections in cats that cause mild sneezing, coughing, nasal and ocular discharge, and fever. However, in rare situations (particularly in young kittens and cats under intense stress like after vaccinations and spay/neuter), the infection may be more serious and end in death. Symptoms often persist for 7 – 10 days. It does transfer between bunnies, dogs, cats, and humans as well.

Again, the most common treatment is Doxycycline, but this gets prescribed for all of everything and has been responsible for creating drug-resistant strains. So it is best to avoid this drug altogether. Antimicrobials could be helpful, as well as FeLife, Angstrom Sulfur and Angstrom Silver, as we have discussed here. These are much safer treatments with a much longer safety record and no dangerous side effects.

Chlamydiosis in cats can be difficult to diagnose as there are many other causes of conjunctivitis and respiratory disease. Cats can develop conjunctivitis, both acute and chronic. Respiratory signs can also develop, but these are less common than with other respiratory pathogens. Interestingly, cats with chlamydia often remain active and eat well. Common symptoms of chlamydia in cats include: eye redness and swelling, squinting, eye discharge, nasal discharge, as well as sneezing. Treatment for this condition would be similar to herpesvirus.

In summary, feline “cat flu” has varying names, as well as severity and duration. Mostly kittens get the worst of it, as they are separated from their moms too early, poor nutrition, and incredible stress of being in new environments. So it gets confusing when an adult cat in our home suddenly shows symptoms of sickness they didn’t seem to have before. So we hope this newsletter helps you sort through all of the seasonal “flu” symptoms as well as how you can help your cat navigate them and feel better again.

What are some of the things you use to help your cats recover from the cat flu? Hit “reply” to this email or leave us a comment or question. We are always looking to learn new ways to help our feline loved ones, and to share them with the community. Until next time, Always Be Curious!