Feline Calicivirus in the Breeding Cattery: Prevention, Recognition and Practical Management

By Dr Miriam Martin – Glitterpaws Burmese & Mandalay

If you've bred cats for any length of time, you'll eventually encounter feline calicivirus (FCV). It's one of the most common infectious diseases affecting cats worldwide and one of the most frustrating. Healthy-looking cats can continue shedding the virus long after they appear to have recovered, allowing infection to quietly spread through a breeding cattery.

After experiencing two separate calicivirus outbreaks in my own cattery just this year having never had it prior to this I found myself diving into the academic literature and speaking with veterinary colleagues to better understand how the virus behaves and how it can be prevented. This article combines current academic veterinary knowledge with the practical lessons I've learnt as both a breeder and a family doctor.

What is Feline Calicivirus?

Feline calicivirus (FCV) is a highly contagious virus that primarily affects the mouth and respiratory tract, although some strains can cause severe systemic disease.

The virus spreads readily through:

• Saliva

• Nasal discharge

• Eye secretions

• Shared food and water bowls

• Litter trays

• Bedding

• Hands, clothing and footwear

• Grooming equipment and carriers

• Direct cat-to-cat contact

Unlike some viruses, calicivirus doesn't require direct contact between cats. Simply moving from one enclosure to another without washing your hands or one cat sneezing through the wire to another cage can be enough to spread infection.

How is it Spread?

Calicivirus is remarkably hardy compared with many respiratory viruses.

Unlike feline herpesvirus, it can survive on contaminated surfaces for one - four weeks, particularly in cool, dry environments. Fortunately, it only remains suspended in the air for 2-3 hours. Transmission occurs mainly through infected secretions and contaminated surfaces (known as fomites).

This means that food bowls, litter trays, bedding, clothing, hands, shoes and carriers all become potential sources of infection.

The incubation period is usually 3–5 days. If exposed cats remain completely healthy after about 7 days, they have probably escaped infection or already possessed protective immunity.

Clinical Signs

Calicivirus can cause anything from mild sniffles to life-threatening disease, particularly in young kittens.

Common signs include:

• Sneezing

• Runny nose

• Watery or sticky eyes

• Conjunctivitis

• Corneal ulcers

• Painful ulcers on the tongue, gums and roof of the mouth

• Fever

• Lethargy

• Reduced appetite

• Dehydration

• Lower respiratory disease including coughing or pneumonia in severe cases

The painful mouth ulcers are often the biggest problem. Many kittens stop eating before they appear seriously ill, and dehydration can develop surprisingly quickly.

Fortunately, most healthy vaccinated adult cats recover within one to two weeks.

Treatment and Supportive Care

There is currently no antiviral treatment for feline calicivirus. Treatment focuses on supporting the cat until its immune system clears the infection.

Supportive care includes:

• Encouraging food intake with warmed, highly palatable foods

• Maintaining hydration

• Cleaning nasal and eye discharge several times daily

• Lubricating eye drops to improve comfort

• Antibiotic eye drops where appropriate to reduce secondary bacterial conjunctivitis, lubricating eyedrops can help relieve symptoms (you can buy polytears or similar over the counter from any pharmacy)

• Pain relief prescribed by your veterinarian

• Antibiotics if secondary bacterial pneumonia or severe bacterial infections develop

Note -antibiotics do not treat the virus itself but can be lifesaving if secondary bacterial infections occur.

Young kittens often require much more intensive supportive care than adult cats.

Why are Kittens so Vulnerable?

Newborn kittens receive maternal antibodies before birth via the placenta and through their mother's first milk (colostrum).

These antibodies provide temporary protection but gradually disappear.

Typically:

• Strong trans-placental maternal protection lasts around 4–6 weeks.

• Milk antibodies may continue providing partial protection for another week or two.

• By approximately 6-7 weeks of age, kittens are increasingly dependent on their own immune system.

Unfortunately, this creates a vulnerable window where maternal antibodies are fading before vaccination has provided full protection.

Carrier Cats and Viral Shedding

One of the reasons calicivirus is so difficult to eliminate is that recovered cats often continue shedding virus after they appear completely healthy.

Many cats continue shedding virus for 70–90 days.

Older studies from the 1970s suggested that up to 40% of cats may become lifelong carriers, although there are surprisingly few modern studies confirming this figure. From discussions with experienced breeders, lifelong shedding anecdotally from other breeders appears to be much less common than those early reports suggested, although it certainly can occur.

If a pregnant queen becomes infected, remember that although she may continue shedding virus after recovery, her kittens initially receive maternal antibodies which usually provide protection for approximately five to six weeks before gradually declining.

Vaccination Strategies

Routine vaccination remains the cornerstone of calicivirus prevention.

For most households and breeding catteries, following your veterinarian's routine vaccination schedule is appropriate.

However, if a pregnant queen is infected vaccine manufacturers recommend an accelerated schedule of: 4, 6, 8, 10 and 12 weeks -separate the mother from the kittens would also be useful to prevent her infecting them, then you could transition to a normal vaccine schedule.

This is expensive but may help protect kittens while their mother is still shedding virus.

For kittens I intend keeping within my breeding programme, I've changed my own vaccination schedule:

I previously vaccinated at 9 and 13 weeks.

Following my outbreaks and review of the literature, I now vaccinate at 9, 13 and 17 weeks.

The vaccination given after 16 weeks is considered the most important because maternal antibodies have usually declined sufficiently to allow the kitten to develop a strong, long-lasting immune response.

I also ensure every adult cat receives their annual booster. Whenever I vaccinate a litter, I review my breeding software to check which adults are due, ensuring no vaccinations are overlooked.

Infection Control and Quarantine

In my opinion, biosecurity is just as important as vaccination.

During an outbreak I always:

• Feed affected cats last.

• Wash hands thoroughly between groups.

• Clean food bowls and litter trays before disinfecting them. (Food and water bowls go through the dishwasher, litter trays are treated with bleach or sodium hypochlorite and detergent and left to drip dry).

• Use disinfectants known to kill feline calicivirus - sodium hypochlorite is cheap and effective or anything recommended by vets.

• Avoid moving kittens around rooms (normally I progress families to bigger rooms over the 10 weeks but during an outbreak everyone stays put).

• Isolate affected cats whenever practical.

Calicivirus is a non-enveloped virus, making it considerably tougher than herpesvirus. Cleaning should always involve two steps:

1. Remove organic material with detergent and water.

2. Apply an appropriate disinfectant with sufficient contact time.

Products containing sodium hypochlorite (bleach) are highly effective when used correctly on clean surfaces. Veterinary disinfectants specifically labelled as effective against feline calicivirus are also excellent choices.

One of the biggest changes I'm attempting to make is quarantining every cat returning from:

• Veterinary clinics

• Cat shows

• Other breeding catteries

for 7 days, even if they appear perfectly healthy.

Because the incubation period is around three to five days, this simple quarantine period gives early infections time to declare themselves before the cat rejoins the breeding colony.

I'm currently planning a purpose-built quarantine area because preventing an outbreak is far easier than controlling one.

What I Learnt from Two Outbreaks

Unfortunately, I've experienced two calicivirus outbreaks in my own cattery.

The first occurred after a queen contracted calicivirus while visiting the veterinary clinic for desexing before retirement. She subsequently infected several older kittens and one of my pregnant queens.

The second outbreak occurred after another cat attended the clinic for her routine annual vaccination. She developed a mild infection and passed it on to two older kittens that had already received vaccinations at 10 and 14 weeks.

Those experiences completely changed how I think about biosecurity.

One lesson that still makes me smile was our solution for kitten vaccinations.

Rather than taking litters into a veterinary waiting room full of potentially infectious cats, we created our own mobile veterinary clinic.

A friend lent us their work van, the veterinarian came outside and performed health checks and vaccinations inside the van instead of us entering the clinic (fortunately he could see our point and was NOT offended!).

It may sound slightly over the top, but it dramatically reduced our concern about exposing young kittens to respiratory pathogens.

If you're considering something similar:

• Clean and disinfect the vehicle thoroughly beforehand.

• Sanitise all equipment and surfaces -especially equipment coming from inside the vet practice such as scales, pens and computer keyboards.

• Wash or sanitise your hands before entering the van, have suitable hand sanitising equipment available.

• Book the first appointment of the day, before potentially infectious patients have visited the clinic.

I also ensure kittens receive their final vaccination at least seven days before desexing, allowing time for immunity to develop before they enter the veterinary hospital environment.

Final Thoughts

After two unfortunate calicivirus outbreaks, my biggest lesson wasn't about vaccines—it was about biosecurity. Note, I don't blame the vet practice, this particular virus is extremely contagious and hard to control and the current vaccines are not fully effective against all strains. I also suspect there's a lot of calici locally making it hard to avoid. But together we work as best as we can to prevent outbreaks.

Vaccination remains one of our most important tools, but quarantine, hygiene and careful management of cats returning from veterinary clinics and cat shows are equally important.

If I could give every breeder one piece of advice, it would be this:

Assume every cat returning home could be incubating calicivirus until you've proven otherwise.

Seven days of quarantine is far easier to manage than three months of viral shedding throughout your cattery.

We can't eliminate every risk in breeding, but we can continually improve our systems and learn from every outbreak. I hope that by sharing both the science and my own experiences, you'll be better prepared than I was.

Disclaimer: This article shares my personal experience as a breeder together with current veterinary knowledge. Every cattery is different, and vaccination schedules and treatment decisions should always be discussed with your own veterinarian.