Feline Calicivirus

Information/Facts
Infection
Clinical Signs
Diagnosis
Treatment
Prognosis
Prevention


calicivirus (c)            orangecat (i)           calicivirus (c)

Information/Facts
Feline calicivirus (FCV) belongs to the family Caliciviridae.  Other members of this family include rabbit hemorrhagic disease virus (RHDV), San Miguel sea lion virus (SMSV), and vesicular exanthema virus of swine (VEV).  (8)

FCV is a positive-strand, non-segmented, polyadneylated RNA genome.  Upon transcription to a DNA complement, many reading errors are made that allow the virus to respond rapidly to environmental selection pressures and makes the virus very adaptable.  This has important implications for clinical disease and control of the virus.  (9)

FHV-I is found worldwide and it is likely that most cats will be exposed to infection at some point during their lifetime.  FHV-I is not a zoonotic disease.  (3)

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Infection
FCV is an important and highly prevalent respiratory and oral pathogen of cats.  The virus is shed in secretions of the nose and eyes of infected cats.  Fecal and urinary shedding may also occur, but is probably not of major epidemiologic importance.  Transmission is by direct cat-to-cat contact.  The virus remains infectious in the environment for 1 week, whereby indirect transmission may occur through items in the environment.  (9)

All ages and breeds are susceptible, but disease may be more severe in young kittens and highly susceptible cats (those with other illnesses, not vaccinated, or living in high risk situations).  The highly virulent strains appear to cause more severe disease in older cats.  (3)
 
FCV is associated with a range of clinical syndromes, from inapparent infections to relatively mild oral and upper respiratory tract disease with or without acute lameness.  Recently, highly virulent forms of the virus have emerged associated with a systemic infection that is frequently fatal.  A proportion of FCV infected cats that recover from acute disease remain persistently infected.  (9)

Acutely infected cats shed the virus for 2-3 weeks; however, some shed persistently for periods varying from months to years, and reinfection also commonly occurs.  (3)
                                                                                                                                                                                                                    
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karatecats (i)

Clinical Signs
Clinical signs usually appear 3-4 days after infection.  Some strains cause few or no signs of illness.  Strains of low virulence produce no or only moderate fever, but can produce ulcers of the tongue, hard palate and nose.  Strains of high virulence can cause fever, anorexia, depression, transient lameness, difficulty breathing and sometimes death, especially in neonates.  (8, 10)

                                                                                                                                                                                                                                
    calicimouth
(u)    calicimouth2 (v) calicinose (u)

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Diagnosis
A presumptive diagnosis of FCV is usually made on the basis of the cat's medical history and clinical symptoms. Virus isolated from the cat's nasal or eye secretions can confirm the diagnosis.  A polymerase chain reaction (PCR) assay has been developed, but is rarely used due to strain variation.  (10)
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Treatment
There is no cure for FHV-I, but sick animals can be treated with supportive therapy.  This may include intravenous (IV) fluids and/or feeding tubes for anorexic cats.  It is recommended to minimize stress, keep cats indoors while they are sick, make sure the cat is eating and drinking enough (offer foods that appeal to them), keep the cat's eyes and nose clean and clear of discharge, and use a humidifier or put the cat in a bathroom while the hot shower is running (this helps break up the mucus in the upper airway).  If the cat has ulcers in its mouth, soft food is recommended.
 
Medications may include antibiotic eye ointments to treat secondary bacterial infections in the eye that can cause conjunctivitis, oral antibiotics to prevent or treat secondary bacterial infections, and pain medication for lameness and associated arthritis.  (3, 10)                                             

          eyeointment
(r)                                           softfood (w)                                         ivfluids2 (l)     
                                                                                                                                            
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Prognosis
Usually about a week after infection, recovery is quick.  Unless the cat develops severe pneumonia, prognosis is excellent.  (10)
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Prevention
Vaccination is the best prevention method available for cats.  As FCV is highly prevalent and easily transmitted, and because disease may occasionally be severe, the FCV vaccine should be considered as one of the core vaccines given to cats.  (3)
 
A modified-live vaccine (MLV) and inactivated vaccine for injectables are commercially available.  A MLV for intranasal use is available and effective in some countries.  The vaccines provide reasonable protection against disease, but do not prevent infection, or the potential of the cat to be a carrier of the virus.  (3)
 
An important consideration for FCV vaccines is the question of strain variation.  Several FCV strains are used in commercially available vaccines and most of these strains appear to protect against most isolates but not as well against all, including some of the high virulent isolates.  (3)

The MLV, injectable is most commonly used.  This vaccine is usually combined with the vaccine for Feline Herpesvirus-I.  The following parameters are recommended (3):

Kittens less than 16 weeks of age:
- first vaccination at 6 wks, repeated every 3-4 weeks until 16 wks
- booster 1 year later
- thereafter, no more than once every 3 years

Kittens/cats older than 16 weeks of age:
- 2 doses, 3-4 weeks apart
- booster 1 year later
- thereafter, no more than once every 3 years

In shelters during an outbreak:
- kittens:  at 4 weeks of age, then every 2 weeks to 16 weeks of age
- older kittens/cats: time of admission, repeated in 2 weeks


Pregnant cats:
- use only if necessary (high risk situations) – used the killed-virus vaccine

Cats with FeLV or FIV infections:
- use the killed-virus vaccine                                                                                                                          
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