Affects: Cats
Cat flu, or feline upper respiratory disease, is a contagious disease complex (can include multiple pathogens) primarily caused by feline herpesvirus type-1 (FHV-1) and feline calicivirus (FVC), with secondary bacterial infections such as Bordetella bronchiseptica and Chlamydia felis sometimes contributing to clinical signs. Other common respiratory pathogens include Mycoplasma felis and Streptococcus zooepidemicus.
Clinical Signs: The viral infection in cats in usually mild, lasting 5-10 days with some cats remaining asymptomatic. More severe cases can last up to 6 weeks. Infected cats can exhibit the following symptoms:
Sneezing
Coughing
Fever (up to 105 °F, 41 °C)
Discharge from the nose or eyes
Transmission And Spread: Cat Flu is spread similarly to the "human flu" including:
Direct contact such as playing, sleeping together, licking, or nuzzling
Airborne droplets through coughing or sneezing which can reach another cat's eyes, nose, or mouth
Contaminated surfaces such as food bowls, bedding, litter, or human hands
Diagnosis: Diagnosis can be unclear due to multiple infections occurring simultaneously. The beginning diagnosis of cat flu is based on typical signs such as sneezing, conjunctivitis, nasal discharge, tearing, drooling, oral ulcers, and difficulty breathing. Feline viral rhinotracheitis (FVR) mainly affects the eyes and nose while calicivirus targets the mouth and lower respiratory tract. Chlamydial infections often cause chronic, mild conjunctivitis.
Examination of Giemsa-stained conjunctival samples can help detect chlamydiae and mycoplasmas. A definitive diagnosis requires identifying the pathogen from samples taken from the mouth, nostrils, or eyes. Diagnosing FVR can be difficult because the virus is shed at irregular intervals and may be present in healthy cats as well as in sick ones.
When symptoms do not subside, veterinarians may run additional tests including chest x-rays, blood tests, or bacterial cultures.
Treatment: Treatment for cat flu is mainly supportive, focusing on relieving symptoms and preventing complications. Antibiotics may be used to control secondary bacterial infections, including Chlamydia felis and Mycoplasma felis. Discharges from the nose and eyes should be cleaned regularly, and saline drops or nebulization can help remove mucus. Antiviral ointments and lysine supplements may be used for eye ulcers caused by FVR. Cats with severe breathing difficulties may require oxygen therapy, fluids for dehydration, or assisted feeding by feeding tube or syringe if they are not eating.
Other common home remedies include exposing the cat to warm, humid air (such as through a humidifier); gentle face washing to remove nasal discharge; and feeding the cat strong-smelling foods (due to the respiratory infections often impacting a cat's sense of smell, and by extension its appetite).
Vaccination: To reduce the spread, veterinarians recommend vaccination of kittens.
These vaccinations are typically risk-based and are usually recommended for cats with increased risk exposure.
Vaccination against cat flu involves intranasal or parenteral vaccines targeting feline viral rhinotracheitis (FVR), feline calicivirus (FCV), and sometimes Chlamydia felis. Kittens older than 9 weeks are typically vaccinated twice, with a 3–4 week interval, and should receive follow-up doses until at least 12 weeks of age. Adult cats generally require revaccination every 1–3 years, with annual boosters recommended for cats at ongoing risk.