Feline Herpesvirus

[Boss Bengal]

Feline rhinotracheitis virus (feline herpesvirus type 1 or FHV-1) causes acute respiratory illness known as rhinotracheitis (or feline herpesvirus infection). The virus affects domestic and wild cats worldwide.

Rhinotracheitis is characterized by respiratory symptoms such as sneezing, nasal discharge, rhinitis (inflammation of the nose), and conjunctivitis (inflammation of the membrane lining the eyelid). It also affects the reproductive tract and can cause complications during pregnancy.

Rhinotracheitis is part of the feline upper respiratory infection complex, which is a group of viral and bacterial infections (e.g., calicivirus, chlamydiosis) that cause sneezing and discharge from the eyes and nose. Cats often have two or more of these upper respiratory infections at the same time, and FHV-1 is one of the most common.

Incidence
FHV-1 occurs worldwide. Cats of all ages and breeds are susceptible, although it is more common in the following:

* Kittens, especially those born to infected mothers
* Multicat households, catteries, and pet adoption shelters, especially those with:
o Overcrowding
o Physical (e.g., temperature) or psychological (e.g., introduction of a new cat) stressors
o Poor nutrition
o Poor sanitation
o Poor ventilation
* Pregnant cats that are lactating
* Sick cats (especially sickness associated with a weakened immune system or other respiratory infection)
* Unvaccinated cats

Transmission
FHV-1 is shed through the discharge from an infected cat's eyes, nose, and mouth. Contact with these secretions is a potential mode of transmission. The most common mode of transmission appears to be contact with contaminated objects that an infected cat has touched or sneezed on including cages, food and water bowls, litter trays, pet owner's clothing, and the pet owner's hands.

FHV-1 can be transmitted by direct contact with an infected cat's mouth, nose, or eye discharge. Several days of close contact are necessary for infection to occur.

Sneezing and coughing can spread the virus as far as 4 feet.

Many cats that are infected with FHV-1 never completely get rid of the virus. These cats are known as latent carriers. Even though they may not show symptoms, they harbor the virus in their nerve cells. Latent carriers spread the infection and are a major source of new infections.

Common symptoms of FHV-1 infection include the following:
* Coughing
* Fever (up to 106°F or 41°C)
* Loss of appetite and weight loss (anorexia)
* Runny nose (rhinitis)
* Sneezing attacks
* Runny eyes

Anorexia results from an inability to smell, loss of appetite, fever, and general malaise. It is one of the more severe symptoms of rhinotracheitis and usually requires assisted feeding.

Most cats infected with FHV-1 have runny eyes due to conjunctivitis and/or ulcerative keratitis. Conjunctivitis is an inflammation of the conjunctiva, the thin, transparent membrane that lines the eyelid. The inflammation leads to discharge, swelling, and pain; the cat's eyes may be red and weepy. Conjunctivitis can be caused by a number of underlying conditions.

Ulcerative keratitis is inflammation and ulceration of the cornea, the transparent front portion of the eye that gathers light rays and directs them into the eye. Ulcerations on the cornea can cause a serious threat to an animal's eyesight. In addition to discharge from the eye, signs of corneal ulcers include squinting, turning away from light, obvious discomfort, and pawing at the eyes.

Infection during pregnancy
Though rhinotracheitis primarily affects the upper respiratory tract, it can also cause complications during pregnancy, including

* bacterial pneumonia in young kittens,
* sickly newborn kittens, and
* spontaneous abortion.

Diagnosis
FHV-1 is usually diagnosed on the basis of the cat's medical history and clinical symptoms. Laboratory tests that detect the virus in the cat's nasal or eye secretions can confirm the diagnosis.

Several different tests can identify FHV-1 in eye and nasal secretions.

An immunofluorescent assay of secretions from the nose or conjunctiva (membrane lining the eyelid) uses special proteins labeled with a fluorescent chemical to detect the presence of FHV-1 antibodies (proteins that the immune system makes to fight the virus).

The virus can be isolated with pharyngeal swab samples (the pharynx is the passageway that leads from the nose to the larynx, and from the mouth to the esophagus). Cotton or gauze is used to collect respiratory tract secretions from the pharynx.

Smears from the conjunctiva can be used to detect structures inside the nucleus of a viral-infected cell.

Differential diagnosis
Clinical symptoms are similar to those of other feline upper respiratory infections. Cats with feline calicivirus infection do not sneeze as often and have less eye discharge and inflammation; they are also more likely to have pneumonia. Cats with chlamydiosis have more chronic conjunctivitis (discharge, pain, and swelling of the eye).

Bacterial infections usually do not involve the eyes and nose.

Treatment for an FHV-infected cat involves providing supportive care, including the following:
* Minimize stress (Make sure the room is warm, well ventilated, and well lighted. Some veterinarians recommend that cats are kept 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.
* 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.)

Anorexic cats
Providing adequate nutrition and fluid is essential for the cat's health. Several different methods can be used to feed a cat that is not eating.

Some cats can be hand fed their favorite foods. Forced feeding can be stressful for the cat, and may not always provide adequate nutrition.

Cats that are stressed by force feeding or that aren't getting nutrition from it, can be fed through a tube (a nasoesophageal or nasogastric tube) that goes into the nasal cavity and extends into the far end of the esophagus, or all the way to the stomach. Tube feeding can be done at home and doesn't require hospitalization.

For cats that are unable to absorb nutrients through the GI tract, or that are so debilitated that even tube feeding can't deliver sufficient nutrients, liquid nutrition can be administered intravenously.

Medication
Depending on the symptoms and the occurrence of secondary infections, medications that may be used include the following:
* Oral antibiotics to prevent or to treat secondary bacterial infections
* Eye ointments to treat ulcerative keratitis
* Decongestants (e.g., nasal drops) to decrease nasal discharge
* Interferon to help control chronic infectious nasal discharge in kittens 3 to 8 weeks old

Prognosis
Rhinotracheitis is a fairly mild condition, even in its most severe form, as long as the cat receives adequate fluids and nutrition. It often runs its course in 7 to 10 days without medical intervention. The infection usually lasts longer when secondary bacterial infections develop. Rarely, FHV-1 causes death in young kittens and older cats. Some cats may develop chronic symptoms such as chronic rhinosinusitis (sneezing and nasal discharge).

Prevention
Routine vaccination against FHV-1 can prevent development of severe disease, but it does not always prevent infection. Kittens should be vaccinated at 8 to 10 weeks of age, then at 12 to 14 weeks of age, and then annually.

An infected cat should be isolated to prevent spread of the virus.