Cat flu

Cat flu is caused by either a herpesvirus Feline rhinotracheitis virus (FRV) or Feline calicivirus (FCV).

These viruses produce signs of sneezing, nasal (nose) discharge, conjunctivitis (inflammation around eyes) fever, and anorexia (loss of appetite). FRV can also cause more severe ocular (eye) symptoms including corneal ulceration (damage to the surface of the eye) and lead to abortion or still birth in pregnant cats. FCV often produces ulcers in the mouth and may lead to mild pneumonia or inflammation of the joints.

The majority of cats will become carriers of the virus once they have recovered and can have recurrences of the acute (short term, severe) signs especially when stressed or if their immune system becomes depressed. Some cats will develop chronic (long term) milder symptoms such as nasal discharge. Carrier status is generally life long with herpes virus but probably only lasts months with calicivirus. A syndrome of chronic ulceration of the gums and mouth which can become severe is however attributed in some cases to persistent calicvirus infection.

Cats become infected through direct contact with other infected or carrier cats both via airborne virus and fomites (saliva, nasal discharge).

Treatment is symptomatic (relieve symptoms). This includes maintaining hydration, decongestants (pediatric topical phenylephrine 0.25%) and topical anti viral eye drops (trifluridine, idoxuridine). Antibiotics may be given to prevent secondary bacterial infection especially in severely affected cases.

Prevention is based on vaccination programs. Combination modified-live vaccines given subcutaneously (injected under the skin) produce very effective immunity. Kittens should be vaccinated at 8 weeks and again at 12 weeks. Two initial vaccinations 4 weeks apart are required for any cat starting a vaccination program. These are followed by annual booster vaccinations for the life of the cat. Modified- live vaccines do not produce any clinical signs when administered subcutaneously however mild signs of disease can occur if the vaccine is accidentally sprayed at the cat or if they lick spilled vaccine from the skin. The live modified-live vaccines are not suitable for pregnant queens (female cats) and cats with feline immunodeficiency virus or feline leukemia virus Killed vaccines are also available and can be used safely all cats. Intranasal vaccines (sprayed into nose) are also available but tend to be used mainly when treating outbreaks in cattery situation. They have the advantage of being faster at inducing immunity and can override the antibodies passed from the queen to her kittens which normally interferes which vaccines given before 8 weeks of age. Their disadvantages are cost, difficulty of administration and they may produce mild signs of flu.