Feline Respiratory Complex

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Feline viral rhinotracheitis (FVR) is an upper respiratory or pulmonary infection of cats caused by feline herpesvirus 1, of the family Herpesviridae. It is also commonly referred to as feline influenza, feline coryza, and feline pneumonia but, as these terms describe other very distinct collections of respiratory symptoms, they are misnomers for the condition. Viral respiratory diseases in cats can be serious, especially in catteries and kennels. Causing one-half of the respiratory diseases in cats, FVR is the most important of these diseases and is found worldwide.

 

Feline calicivirus (FCV) is a virus of the family Caliciviridae that causes disease in cats. It is one of the two important viral causes of respiratory infection in cats, the other being feline herpesvirus. FCV can be isolated from about 50% of cats with upper respiratory infections.

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Feline chlamydiosis is an infection caused by a bacterial organism now called Chlamydophila felis or C. felis (an outdated name for this is Chlamydia psittaci (feline strain)). It is an unusual bacterium because it must live and multiply inside the body cells of the cat whereas most bacteria live outside cells. Another outdated term for this infectious disease is Feline Pneumonitis. Although the term pneumonitis implies inflammation of the lungs, in a cat with a C. felis infection most symptoms involve the eyes or the upper respiratory tract (nose or throat).

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How do cats become infected?

 

FVR is transmitted through direct contact only. It replicates in the nasal and nasopharyngeal tissues and the tonsils. Viremia (the presence of the virus in the blood) is rare. The virus is shed in saliva and eye and nasal secretions, and can also be spread by fomites. FVR has a two- to five-day incubation period. The virus is shed for one to three weeks postinfection. Latently infected cats (carriers) will shed FHV-1 intermittently for life, with the virus persisting within the trigeminal ganglion. Stress and use of corticoids precipitate shedding. Most disinfectants, antiseptics and detergents are effective against the virus. Initial signs of FVR include coughing, sneezing, nasal discharge, conjunctivitis, and sometimes fever (up to 106 F) and loss of appetite. These usually resolve within four to seven days, but secondary bacterial infections can cause the persistence of clinical signs for weeks. Frontal sinusitis and empyema can also result.

 

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FHV-1 also has a predilection for corneal epithelium, resulting in corneal ulcers, often pinpoint or dendritic in shape. Other ocular signs of FHV-1 infection include conjunctivitis, keratitis, keratoconjunctivitis sicca (decreased tear production), and corneal ulcers. Infection of the nasolagrimal duct can result in chronic epiphora (excess tearing). Ulcerative skin disease can also result from FHV-1 infection. FHV can also cause abortion in pregnant queens, usually at the sixth week of gestation although this may be due to systemic effects of the infection rather than the virus directly.

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In chronic nasal and sinus disease of cats, FHV may play more of an initiating role than an ongoing cause. Infection at an early age may permanently damage nasal and sinus tissue, causing a disruption of ciliary clearance of mucus and bacteria, and predispose these cats to chronic bacterial infections.

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FCV spreads by direct contact with virus containing droplets from an infected cat and contaminated surfaces such as food and water bowls or bedding. All forms of the infection are caused by FCV. This is a virus that is transmitted through the mucous membranes of the eyes, nose, and lining of the eyelids. Once the virus enters the body, it multiplies mainly in the oral and respiratory tracts and causes the upper respiratory signs listed above. If the virus goes beyond the respiratory tract, it may affect the synovial membranes of the joints, leading to the signs of lameness and arthritis. Very rarely, FCV is able to access other cells and tissues in the body. In this case, the virus attacks vital organs like the liver, pancreas, gastrointestinal tract, and lungs, resulting in all the general symptoms, and also signs of systemic infection like swelling and ulceration of the skin and bleeding from body openings. In very severe cases, the only sign you see will be death.

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Chlamydia felis is spread by close or direct contact with an infected cat, so all cats in the home can become infected. For this reason, if one cat in the home is diagnosed with a C. felis infection, all cats in the household should be treated. Because Chlamydia lives inside cells of the body and is not able to survive for long in the environment, spread of infection relies on direct or close contact with an infected cat. Following infection, the incubation period (the time between infection and development of clinical signs of disease) is between three and ten days.

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How is feline respiratory complex diagnosed?

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Diagnosis of FVR is usually by clinical signs, especially corneal ulceration. Definitive diagnosis can be done by direct immunoflorecence or virus isolation. However, many healthy cats are subclinical carriers of feline herpes virus, so a positive test for FHV-1 does not necessarily indicate that signs of an upper respiratory tract infection are due to FVR. Early in the course of the disease, histological analysis of cells from the tonsils, nasal tissue, or nictitanting membrane (third eyelid) may show inclusion body (a collection of viral particles) within the nucleus of infected cells.

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If you suspect that your cat has FCV, contact your veterinarian. Your doctor will collect a detailed history including when you first noticed the signs and whether your feline friend has been in contact with other cats. Following a thorough physical exam to evaluate your cat's health and check all the body systems, your vet may choose to conduct further tests. A presumptive diagnosis is possible based on the history and physical. Depending on the severity of the illness, your vet may want to take x-rays to check for signs of pneumonia or run bloodwork to check for signs of organ damage. Treatment can be conducted based on the symptoms. For a definitive diagnosis, the doctor can take swabs of the mucous membranes of the eye or mouth and send them to a laboratory for analysis.

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Chlamydiosis can be difficult to diagnose because there are many causes of conjunctivitis and cats may have multiple infections at the same time. The preferred method of diagnosis is by direct isolation of the C. felis organism. This involves taking a swab sample from the conjunctival membrane. The swab is then placed in special transport media and sent to a laboratory where the sample is grown in culture and subsequently identified. Occasionally, the Chlamydophila organisms are visible in stained smears prepared from conjunctival scrapings. Another diagnostic option is testing a blood sample for the presence of C. felis antibodies. This test can be useful in cases where the laboratory culture result is negative or as a general screening test for catteries or multi-cat households where conjunctivitis is a chronic problem. A new PCR-assay (Polymerase Chain Reaction), which is performed on conjunctival scrapings, is becoming more widely available for diagnosis of this infection.

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How is feline respiratory complex is prevented?

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Feline vaccines include a small quantity of killed or modified virus, which enables the body to build immunity towards certain infectious agents. Some pet owners are concerned about the side effects of vaccines, particularly vaccine associated sarcomas. However, newer vaccines don't contain adjuvants that are related to the formation of vaccine associated sarcomas in pets. All cats and kittens are generally administered core vaccines. Non-core vaccines should be administered to those pets at greater risk of contracting specific diseases. Although vaccines protect pets to a great extent, pet owners should always adopt preventive measures to ensure complete protection.

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FVR and FCV vaccines are available as modified live vaccines and killed injectable vaccines. The modified live vaccines provide better protection and are safer for use on healthy pets with strong immune systems. Vaccines may also be administered as intranasal vaccines, which are safely administered in the nose. Vaccines are often administered as combination doses, since feline herpes vaccine may be given along with the feline calicivirus vaccine. Most vaccines require annual booster shots to ensure protection.

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Various vaccines are available and are most useful in breeding catteries or animal shelters where it can be difficult to eliminate the organisms completely. In areas where C. felis is endemic, routine vaccinations may minimize the risk of future outbreaks. Vaccination may also be desirable in Chlamydophila-free colonies and in household pets to provide protection for high-risk situations such as boarding catteries and breeding. This vaccine is considered a "non-core vaccine" and is recommended if your cat is at reasonable risk for contracting the disease. The protection afforded by the vaccine is relatively short, and annual boosters are usually required. Your veterinarian will advise you on the appropriate vaccination choices for your cat, based on the prevalence of this disease in your area.

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