Feline calicivirus (FCV): the complete treatment guide.
Feline calicivirus is one of the most contagious infections cats encounter. It causes painful ulcers on the tongue and palate, and when it turns chronic it leaves a mouth that never quite heals. Here is how to recognise it, how it is diagnosed, what the treatment options are, and how to handle relapses. We ship across the Gulf.
From the first signs to managing relapses, in four parts.
Everything worth knowing about feline calicivirus and its antiviral treatment, in the order you need it.
- 1
Recognise the signs
What happens in the mouth, what happens in the airways, and the severe form that appears rarely.
- 2
Confirm the diagnosis
How calicivirus is separated from other causes of stomatitis and conjunctivitis.
- 3
Start treatment
CaliciX™ and CaliciX™ Max, and where they sit relative to dental extraction.
- 4
Care and relapses
Feeding a cat in oral pain, hygiene in multi-cat homes, and the early signs of relapse.
What feline calicivirus is
Feline calicivirus (FCV) is an extremely contagious RNA virus. It is found worldwide, is one of the leading causes of upper respiratory infection in cats, and is the virus most closely associated with chronic oral inflammation. It spreads through saliva, nasal and ocular discharge, and shared bowls and bedding, so it moves quickly through multi-cat households, shelters and catteries.
- 1
Acute disease
Appears on first infection or when the virus reactivates. Sneezing, nasal discharge, watery eyes, fever, and painful ulcers on the tongue and palate. Most cats recover within a few weeks with supportive care.
- 2
Chronic disease
In some cats the virus persists in the oral mucosa and inflammation continues. It can develop into feline chronic gingivostomatitis (FCGS), with inflammation spread across the gums and mucosa. The pain stops the cat eating and weight starts to fall.
There is a severe form, though it is uncommon.Virulent systemic feline calicivirus (VS-FCV) presents with high fever, swelling of the face and paws, lameness, jaundice and pneumonia, and it moves fast. If this form is suspected, treat it as an emergency.
Signs of feline calicivirus
The signs concentrate in the mouth and the upper airways. Ulcers and drooling are the clearest indicators.
- 1Ulcers on tongue and palate
- 2Drooling
- 3Severely inflamed gums
- 4Bad breath
- 5Approaches the bowl and walks away
- 6Sneezing
- 7Nasal discharge
- 8Conjunctivitis and eye discharge
- 9Fever
- 10Lethargy and weight loss
It is not lack of appetite: it hurts to eat.A cat with an inflamed mouth walks to the bowl, sniffs it, and turns away without touching the food. Tell your veterinarian this, because it changes how the case reads entirely.
How it is diagnosed
Not every case of stomatitis or gingivitis in cats is calicivirus. Diagnosis combines what is seen in the consultation with laboratory work.
- 1
Clinical examination
Where the ulcers sit tells you a great deal. Calicivirus ulcers appear mainly on the tongue, hard palate and lips. On the gums you see diffuse inflammation more than defined ulcers.
- 2
RT-PCR
Detects viral genetic material from an oral swab. Cats without signs can also test positive, so the result is read alongside the clinical picture.
- 3
Virus isolation
Performed in specialist laboratories and reserved for cases that are hard to interpret.
- 4
Ruling out other causes
Feline herpesvirus (FHV-1), periodontal disease, tooth resorption lesions, stomatitis secondary to kidney disease, and the involvement of FIV or FeLV.
Telling it apart from feline herpesvirus (FHV-1).The two look similar but present differently. If ulcers in the mouth dominate, calicivirus is more likely. If the eyes and sneezing dominate, it points to herpesvirus. You can compare against the FHV-1 guide.
The treatment
Treatment works on two fronts: slowing viral replication, and controlling pain and inflammation. Antibiotics address secondary bacterial infection but do nothing to the virus. That distinction causes more confusion than anything else here.
CaliciX™ and CaliciX™ Max
CaliciX™ and CaliciX™ Max contain EIDD-1931, the active metabolite of molnupiravir, in capsules formulated for cats. They are used for feline calicivirus and the associated chronic gingivostomatitis. The earlier treatment starts, the better the expected outcome.
- Not split human tablets: EIDD-1931 formulated for cats.
- Incorporated into viral RNA during replication, accumulating mutations until the virus can no longer multiply.
- Combined with pain relief, antibiotics where there is secondary infection, oral hygiene and nutritional support.
- 1
CaliciX™ 15 mg
The standard strength, for mild to moderate oral disease. Size 3 capsules, small and easy to give whole or with the contents mixed into food.
- 2
CaliciX™ Max 30 mg
The high-dose strength, for severe, refractory or high-viral-load cases, cats that have not responded to the standard dose, and larger cats. Also for chronic gingivostomatitis that remains active after extraction.
Not for pregnant or lactating queens.EIDD-1931 is teratogenic, so neither strength is given to cats that are pregnant, nursing or intended for breeding. Before starting, tell your veterinarian every medication your cat is receiving.
Where dental extraction fits
This is the question we are asked most: if I use an antiviral, can I avoid the extraction?
- 1
Extraction has the strongest evidence today
For feline chronic gingivostomatitis, full-mouth dental extraction remains the best-supported treatment, with remission reported in roughly 60 to 70% of cats. That is higher than any other option, and there would be no sense in hiding it from you.
- 2
And some cats still do not improve
The remaining 30 to 40% continue with inflammation after surgery. Those cats, the ones extraction did not resolve, are exactly where antiviral treatment makes the most sense.
CaliciX™ does not replace extraction.In practice it is used when extraction has not resolved the case, when it helps to reduce inflammation and viral load before surgery, or when surgery is not a viable option. The final decision is one you make with your veterinarian.
How long treatment runs
It depends on severity. Beyond 12 weeks, treatment continues with blood count monitoring.
- MILD
4 to 6 weeks
Early ulceration, juvenile gingivitis, mild viral oral disease.
- MODERATE
6 to 8 weeks
Gingivostomatitis with difficulty eating and drooling, moderate ulceration.
- SEVERE
8 to 12 weeks or more
Severe feline chronic gingivostomatitis, caudal stomatitis, extensive ulceration, marked pain or complete food refusal.
Improvement follows an order.Drooling and pain ease between days 3 and 7, ulcers shrink over 1 to 2 weeks, appetite and weight return over 2 to 3 weeks, and the mucosa finishes healing between weeks 4 and 12. Many owners notice within the first week that the cat is drooling less. Do not stop there: it looks resolved from the outside, but the mucosal inflammation is still present.
Care during treatment, and relapses
Feline calicivirus spreads very easily, so daily hygiene and how you offer food matter as much as the antiviral itself.
- 1
Isolation and hygiene
Separate the cat showing signs and wash your hands between cats. Calicivirus resists many common disinfectants, so bowls and bedding should be disinfected with diluted bleach.
- 2
How to offer food
Soft food, slightly warmed: warmth lifts the aroma and makes eating easier with a sore mouth and a blocked nose. Add more water bowls and set them at a comfortable height.
- 3
Vaccination and prevention
Keep vaccinations current. Calicivirus has many strains and the vaccine does not prevent infection, but it does reduce severity.
- 4
Records and observation
Weigh the cat once a week at the same time. Gently clean eye and nasal discharge, and space out stressful events such as visitors or travel.
Even after a successful first course, 20 to 30% of cats relapse.The early signs are five: drooling returns even mildly, appetite drops slightly, the cat occasionally paws at its mouth, bad breath comes back, and the gums redden again. Getting help at this stage is far more manageable than waiting for the case to worsen.
About feline calicivirus
Does feline calicivirus resolve permanently?+
Most cats get through the acute phase and return to life without signs. That said, there is no way to confirm the virus has left the body entirely, and in some cats it persists. The aim of treatment is to control the signs and keep the cat comfortable.
What should I feed a cat with a painful mouth?+
Soft food, slightly warmed, with a strong aroma works best. Warming lifts the smell, and even a cat with a blocked nose will attempt to eat. Water should always be available.
CaliciX™ or CaliciX™ Max?+
The active ingredient is the same, EIDD-1931. CaliciX™ contains 15 mg per capsule and CaliciX™ Max contains 30 mg. The high dose is reserved for severe or refractory cases, cats that have not responded to the standard dose, and larger cats. If you are unsure, get in touch.
Can a vaccinated cat still catch it?+
Yes, it happens. Calicivirus has many strains and the vaccine does not block infection. What it does is make the illness milder, so it is still worth keeping current.
Will it spread to my other cats?+
Yes. It spreads through sneeze droplets, nasal and ocular discharge, shared bowls and litter trays, and grooming. Cats without signs can also be shedding virus. In multi-cat homes, separate bowls and trays and clean frequently.
Can I or my dog catch it?+
No. Feline calicivirus is specific to cats: it does not infect people, dogs or other species.
Why are antibiotics not enough?+
Because this is a virus, and antibiotics act on bacteria. They are prescribed when there is a secondary bacterial infection in the mouth, but the virus itself needs an antiviral.
After recovery, is the cat still infectious?+
Some cats continue shedding virus for weeks or months, and a few remain long-term carriers. Even once signs have resolved, maintain hygiene measures if the cat lives with others.
If your question is not here, see the FAQ.
If you suspect feline calicivirus
Mouth ulcers, drooling, sneezing or fever: the sooner you act, the better. See your veterinarian first, then talk to us about treatment. We ship across the Gulf.
This page is general information and does not replace veterinary consultation. Diagnosis and the treatment plan are always decided with your veterinarian. Related pages: FIP guide · FHV-1 guide