Feline Calicivirus: A Common Hazard for Cats 
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The calicivirus in cats causes feline influenza, which can be recognised by symptoms including severe eye discharge.
Feline Calicivirus (FCV) is a widespread concern, particularly in households with multiple cats. Discover what makes Calicivirus dangerous for cats and how you can help a feline that’s been infected.
Table of contents
- How Dangerous is Calicivirus for Cats?
- Symptoms of Calicivirus in Cats: What are the Signs of Infection?
- Common FCV symptoms in cats
- Virulent systemic feline calicivirus disease” (VSFCD)
- How Long is a Cat with Calicivirus Infectious?
- Diagnosis: How is Calicivirus Infection in Cats Detected?
- Treatment: What to Do if Your Cat Has Caliciviruses?
- Causes: How do Cats Contract Feline Caliciviruses?
- Prognosis: Can a Cat Survive Calicivirus?
- Prevention: Protecting Your Cat from Feline Calicivirus
How Dangerous is Calicivirus for Cats?
Feline Calicivirus is an unenveloped, single-stranded RNA virus capable of adapting through spontaneous mutations. As such, numerous virus variants exist, varying in their infectivity.
Caliciviruses play a significant role in cat flu, potentially causing health issues like respiratory problems.
When particularly aggressive virus strains are at play, Calicivirus can be fatal for cats. Therefore, it’s critical to get veterinary care for your cat if you suspect it has the virus.
Which Cats are Often Affected?
FCV infections are common in environments where multiple cats live together, such as animal shelters or breeding stations.
A study notes that nearly half of the cats in German households with multiple cats are infected with Calicivirus. However, not all infected cats show symptoms.
Good to know: Although rare, it’s possible for a free-roaming cat to contract the virus from other wandering cats.
Is Calicivirus in Cats Contagious to Humans?
Caliciviruses are strictly host-specific. There’s no need to worry about contracting Feline Calicivirus as a human. However, you can spread the virus around your home, so it’s essential to maintain good household hygiene.
Symptoms of Calicivirus in Cats: What are the Signs of Infection?
Symptoms usually manifest within two to six days after infection. The clinical signs of a Calicivirus infection depend on various factors such as the virus strain’s infectivity and the individual characteristics of your cat, like its immune status.
Common FCV symptoms in cats
- Lack of appetite
- Fever
- Lethargy
- Sneezing and coughing
- Purulent or serous eye and nasal discharge
- Inflamed blisters and ulcers in the mouth, such as at the base of the tongue
If the virus spreads to other body parts via the bloodstream, additional issues like vomiting and diarrhoea can arise. Cats may also experience joint problems, leading to lameness in severe cases.
Virulent systemic feline calicivirus disease” (VSFCD)
The “virulent systemic feline calicivirus disease” (VSFCD) represents a particularly grave form, with a mortality rate of up to 80%. Vaccinations, unfortunately, do not reliably protect against this type.
How Long is a Cat with Calicivirus Infectious?
The challenging aspect of Feline Calicivirus infection is that some cats show no symptoms despite being infected, making them “asymptomatic carriers.”
Undetected, infected cats can spread the virus for months or even years through secretions, particularly eye discharge and saliva. Reports even mention the possibility of lifelong viral shedding.
When Should I Visit the Vet?
If your cat is lethargic or exhibits the above symptoms, you should consult your vet as a precaution. The sooner you seek expert advice, the quicker you can help your cat and potentially protect other cats in your household from infection.
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Diagnosis: How is Calicivirus Infection in Cats Detected?
Since FCV does not present uniformly, vets may not be able to identify a Calicivirus infection immediately.
Diagnosis may take time and require specific tests. Typically, the vet will collect swab samples from your cat’s eyes and nasal discharge and send them to a specialised laboratory.
Testing with RT-PCR
Real-time PCR (RT-PCR) is a molecular biology technique for detecting viruses. However, since many asymptomatic cats carry Feline Caliciviruses, a positive test result does not necessarily correlate with observed symptoms.
Additionally, the test is not suitable if your cat has been vaccinated against the virus – the result would still be positive.
Ruling Out Other Pathogens
Since cat flu often involves mixed infections with other pathogens, these must also be considered.
Hence, vets typically perform additional blood tests as part of the FCV diagnosis to rule out other potential diseases.
Treatment: What to Do if Your Cat Has Caliciviruses?
Currently, there are no antiviral medications available for Calicivirus in cats, so symptomatic treatment is required. The specific therapy your cat needs depends on the severity of the condition.
Medications to alleviate symptoms often include:
- Eye ointments
- Anti-inflammatories
- Daily nasal flushing with saline
- Antibiotics and immunomodulating drugs as necessary
Additional treatments like inhalation or infusion therapy may be required.
Causes: How do Cats Contract Feline Caliciviruses?
Direct contact with infected cats is the most common cause of FCV infection. Your cat could also become infected by inhaling aerosols.
Once the virus enters the nose, it accumulates in the upper respiratory tract and tonsils after a few days. If it spreads through the blood, it’s referred to as viremia.
How Long Can Caliciviruses Survive?
Feline Calicivirus is very resistant and cannot be inactivated by organic solvents. It can survive about ten days at normal room temperature and in dry environments.
Prognosis: Can a Cat Survive Calicivirus?
Not all cats with Calicivirus show symptoms, and even if they do, it does not necessarily lead to fatality. Severe cases with fatal outcomes are rare.
Often, an improvement is seen after a prolonged phase of shedding the virus. Nevertheless, it’s crucial for your cat to receive veterinary care.
Can a Cat with Calicivirus Live with Other Cats?
When multiple cats live together, there’s a high chance they will repeatedly infect each other with FCV. Therefore, if your cat is sick, it’s important to isolate it until your vet provides further instructions.
Prevention: Protecting Your Cat from Feline Calicivirus
If you have multiple cats, it’s vital to take steps to prevent a Feline Calicivirus infection. Here’s how:
- Hygiene measures: The right hygiene is crucial, as the viruses can survive for long periods and are resistant to certain disinfectants.
- Vaccination: Seek early advice from your vet about vaccinations. They can help prevent severe illness from an early age.
Regularly wash your hands after petting your cats. If one of your cats is diagnosed with FCV, provide it with separate food and water dishes. With preventive measures and support from your vet, it’s possible to manage Calicivirus in cats.
This article from zooplus Magazine is purely informative. If your pet is experiencing discomfort, contact your veterinarian for diagnosis and treatment.
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At the Justus-Liebig-University of Giessen I was extensively trained as a veterinarian and was able to gain experience in various fields such as small animal, large animal and exotic animal medicine as well as pharmacology, pathology and food hygiene. Since then, I have been working not only as a veterinary author, but also on my scientifically driven dissertation. My goal is to better protect animals from pathogenic bacterial organisms in the future. Besides my veterinary knowledge, I also share my own experiences as a happy dog owner and can thus understand and enlighten fears and problems as well as other important questions about animal health.
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