Cat Flu 

When humans get the flu, we normally experience three or four days of ill-health, then usually we recover without long-term consequences. Only in the very young, the elderly and those with other illnesses is human flu really of any concern. Cat flu, is however, a serious illness in cats. Even a mild infection can cause illness for two to three weeks and in many cats with flu, the disease can last for months or years.

Causes

Catflu is caused by one or both of the viruses - feline herpes virus 1 and feline calicivirus. Herpes virus causes upper airways infection in young kittens, sneezing and bronchitis. It can also cause eye infections (conjunctivitis and eosinophilic keratitis). About half the cats presenting with respiratory disease have feline herpesvirus 1 infection, about half have calicivirus infection and a few have Chlamydia psittaci infection. All species of the family Felidae are believed to be susceptible.

Feline herpesvirus 1 causes acute disease of the upper respiratory tract in the first year or so of life. After an incubation period of 24-72 hours, there is a sudden onset of bouts of sneezing, coughing, profuse serous nasal and ocular discharges, frothy salivation, dyspnoea, anorexia, weight loss and fever. Occasionally there may be ulcers on the tongue. Keratitis associated with punctate corneal ulcers is common. In fully susceptible kittens up to 4 weeks old, the extensive rhinotracheitis and an associated bronchopneumonia may be fatal. Clinically the disease caused by herpesvirus is very similar to that by calicivirus. Profuse frothy salivation and corneal ulcers suggest herpes virus infection, whereas ulcers of the tongue, palate and pharynx suggest calicivirus infections. Infections of cats over six months of age is likely to result in mild or subclinical infection. Pregnant queens may abort, although there is no evidence that the virus crosses the placenta and fatally infects foetuses, and virus has not been isolated from aborted foetuses or placenta. Abortion is thought to be secondary to fever and anorexia.

The long term consequences can also be serious as many cats that do recover can have recurring eye infections, sinus infections and ulcers, especially in the gastrointestinal tract and urinary tract (cystitis). Calicivirus cause lameness and fever in young kittens (these can occasionally be seen after vaccination) but more commonly the kittens present with ulcers in the mouth, sneezing and runny noses. Although the viruses can be isolated by taking a nasal/oral swab and testing this at the lab, most vets normally treat symptomatically, assuming both viruses are involved.

Feline herpes viral infection

Symptoms

Cat flu symptoms include sneezing, nasal discharge, conjunctivitis (inflammation of the lining of the eyes), discharge from the eyes, loss of appetite, fever and depression. Occasionally, mouth and eye ulcers and excessive drooling of saliva may be seen. Where death occurs this is usually because of secondary infections, lack of nutrition and dehydration. Cat flu is most commonly seen in situations where cats are kept in large groups such as breeding catteries and rescue centres, although it can also be seen in pet cat households. Vaccination is most important to prevent this disease and it is important to ensure that the queen is fully vaccinated prior to mating to give the kittens the highest protection at birth from maternal antibodies. Although vaccination helps to reduce the risk of cat flu, this disease can still be seen in vaccinated cats.

Ulcers caused by cat flu calicivirus

Treatment

Most kittens with flu are reluctant to eat, so nursing is the most important part of assisting with recovery. Always make sure that the food they are given is warmed (more palatable, and tasty) and that hand-feeding may be required to keep them eating. Bathing the eyes and nose with warm salty water or cold calamine tea will hep stop secondary eye infections. With kittens that have serious sinus infections, placing them in a steamed bathroom will help soften the nasal mucous.           

1. Antibiotics - broad spectrum antibiotics such as Amoxil®, Antirobe®  or Clavulox®. However, Vibravet® is not normally recommended because it causes yellowing of the kitten's teeth, although the drug does cause clinical improvement in symptoms while the kittens are on this medication. Zithromax has shown to resolve symptoms in kittens suffering from flu symptoms. The recommended dose is 80mg orally once or twice a week for 3-6 weeks, or until symptoms resolve.
2. Mucolytics - drugs which soften the mucous such as Mucohex® or Bisolvon® are often used in conjunction with antibiotics, but their effects are variable. Use of mucous softening therapy such as steam therapy does have some benefits anecdotally. Kittens placed in a steaming bathroom while the owner showers have shown to ease breathing in severely dyspnoeic kittens.
3. Eye ointments are commonly used when conjunctivitis is present. Broad-spectrum antibiotic drops such as Chloromycetin or Chloropt improve clinical symptoms associated with conjunctivitis. It is not recommended that eye ointment containing corticosteroids be used as this often exacerbates the infection.  Zivorax®, an anti-viral eye ointment, has been used with some success, but must be applied 6-8 times a day. Kittens that are seriously ill with cat flu require intensive treatment and many that do recover are quite often left with recurring bronchitis.
4. Antiviral therapy - Lysine is commonly used at 100mg per kitten daily (500mg daily for adult cats) until symptoms resolve, which may take up to 4 weeks. NB: It is advisable not to use lysine on pregnant queens.

Carriers

Most cats that recover from cat flu become 'carriers'. Carrier cats usually show no sign of illness themselves but, by shedding virus in their saliva, tears and nasal secretions, are a source of infection to other cats. Kittens that have had herpes virus infection remain carriers for the rest of their life.  

Control

All cats and kittens must be vaccinated against cat flu from an early age (around 6 weeks). Once cat flu is suspected in a kitten, it is strongly advised to quarantine the cat until at least a week after symptoms have disappeared. It is always advisable when selling a kitten to advise the purchaser that the kitten has had cat flu. Although mild doses of cat flu are not normally a problem, if the new owner is considering showing the cat at a cat show, the risk of spread to other cats can be a problem. Because the virus can be spread from nasal discharges and sneezing, isolating the sick cat is important - perhaps housing it in a separate room altogether. The use of disinfectants on the kitten's bowl, bedding, etc is vital. Also, washing of hands and using shoes and aprons in the kitten's room are the best way of stopping spread of the virus from one area of the house to another. Separate food bowls and litter trays must also be considered.

Breeder obligations with 'cat flu' and kittens sold under 'warranty'

Herpes virus normally infects kittens prior to or immediately after birth and kittens usually shows symptoms from birth onward, although many symptoms appear at the 6-14 week age period when maternal immunity begins to wane. Contributing stressors such as weaning, rehousing, air travel, etc., usually exacerbate any subclinical disease and quite often the first symptoms of the disease occur when the kitten is sold to a new owner. The fact that the symptoms appear after sale does not exclude the breeder female cat as the origin of the infection, regardless of her immune or vaccine status. Chronic Herpes virus ‘carrier’ cats are a well recognised phenomenon in catteries and is a problem that is difficult to eradicate. In Victoria (Australia), the usual protocol for kittens that show Herpes infection is for the breeder to recognise the problem as evidence that the virus is present within their cattery and to take necessary sanitation steps to attempt to eradicate or at least minimise the problem in the future. Also, adequate remuneration of out-of-pocket expenses for buyers of infected kittens is a moral requirement if a diagnosis of Herpes viral infection is made by a referral veterinarian. This assumes that the breeder is made aware of the problem by the buyer within an acceptable period after sale (usually up to 4-6 weeks post-purchase). Most breeders sell kittens with a ‘warranty’, covering part or all of any veterinary health expenses that can be attributed to preventable infectious (particularly herpes/calicivirus virus, Chlamydia, FIP) or hereditary diseases.