AETIOLOGY AND PATHOGENESIS

Feline coryza syndrome has similarities with kennel cough in dogs and in fact both are “umbrella” diseases in which several viruses and bacteria play a role.

The four main pathogens involved are:

• Bordetella bronchiseptica

Bordetella bronchiseptica, a bacterium that is also implicated in canine kennel cough and can be transmitted to cats via this route. It is rarely the primary cause of coryza. It causes rhinitis and also bronchitis, which can develop into pneumonia.

B. Bronchiseptica is highly contagious and asymptomatic animals can be long-term carriers. It can also be reactivated. Note that the disease it causes is zoonotic, meaning it can be transmitted to humans and may pose a risk to immunocompromised individuals.

• Feline calicivirus

Feline calicivirus (FCV) accounts for about 40% of reported coryza cases. Both hypovirulent and hypervirulent antigenic variants exist. Transmission is direct, via the airways. The virus preferentially lodges in the nasal epithelium, ocular conjunctiva, tongue and palate, where it takes hold and causes areas of necrosis or ulceration. In severe cases, following viremia (where the virus spreads throughout the body via the bloodstream), FCV may result in arthritis or pulmonary alveolitis. Chronic infections are possible, with persistent, lifelong viral shedding in 15-20% of infected cats.

A form of systemic infection with hypervirulent calicivirus is also found. This particularly aggressive and contagious mutant calicivirus causes viral haemorrhagic fever with oedema of the face and limbs, necrosis of the skin, paw pads and nose, icterus (jaundice), shortness of breath and sometimes sudden death. Mortality can be as high as 67%. Conventional vaccination is currently ineffective in the case of the mutant variant.

• Chlamydophila felis

Chlamydophila felis accounts for some 30% of coryza cases. It is an intracellular bacterium with a tropism for the ocular (typical purulent conjunctivitis), nasal and bronchial conjunctiva. Transmission occurs through close direct contact. A chronic carrier state is possible because the bacterium may act as a commensal host.

• Herpesvirus

Feline herpesvirus type 1 (FHV-1) accounts for 40% of coryza cases. It is the causative agent of potentially severe infectious feline viral rhinotracheitis. In fact, its tropism for the upper respiratory tract (ocular and nasal conjunctiva, oropharynx, trachea), the bronchi, bronchioles and neurons makes it a potentially dangerous virus, since it can cause encephalitis and pneumonia.

Like many herpesviruses, it can remain in a latent state in neuronal ganglia, especially the trigeminal ganglion, in which case it is undetectable. All it takes to reactivate it is a drop in immunity, corticosteroid administration, stress or another disease, leading to infection and viral shedding. It is highly contagious and is transmitted through close direct contact, for example between a mother and her kitten.

CLINICAL SYMPTOMS

Feline coryza typically presents with runny nose and eyes, sneezing, conjunctivitis, fever and anorexia.

Some symptoms are more pronounced, depending on the main causative agent. Superinfections are not uncommon and can lead to deep lung involvement, worsening the condition. Superinfections with the following have been reported:

• Bordetella associated with coughing, swelling of the submandibular lymph nodes and crackles on auscultation;
• Calicivirus, which presents in the form of painful tongue ulcers, halitosis and glossitis;
• Chlamydophila, which mainly causes persistent conjunctivitis;
• Herpesvirus, the most common symptoms of which are recurrent conjunctivitis and keratitis.

DIAGNOSIS

Coryza is much more common and serious in cats sharing close quarters, such as animal shelters and breeding facilities, in animals living in a precarious situation and in young cats not protected by vaccination or maternal antibodies.

Oropharyngeal or conjunctival swabs are used to identify the causative agents.

TREATMENT

Treatment is palliative and is primarily intended to prevent bacterial superinfection by administering specific antibiotics for an extended period of time. Efforts must also be made to alleviate fever and the severe pain caused by ulcers, both of which lead to prolonged anorexia.

Sometimes affected cats need to be admitted and put on a drip. It may be necessary to place a nasogastric or oesophagostomy feeding tube to provide nutrition as quickly as possible. If a cat is not eating, it cannot make antibodies and risks developing hepatic lipidosis, commonly known as fatty liver.

Aerosol or inhalation therapy can be highly effective, particularly with Respi Miloa™, which clears the airways and gives the animal a boost. A cat that has lost its sense of smell due to a congested nose stops eating and becomes debilitated.

To provide additional support, Immune Supp™ is the ideal choice to stimulate a cat’s natural defences.

Remember that sick animals must be isolated and quarantined, observing strict hygiene procedures, as all pathogens are extremely contagious.

PREVENTION

Various broad-spectrum vaccines are available to prevent coryza or at least reduce the severity of the symptoms. Please note, however, that vaccination does not provide 100% protection against infection and, most importantly, does not prevent recurrence of viral shedding.

Dr Isabelle de Grand Ry
DMV | GPCert In Small Animals Surgery
Vet Center l’ETOIL
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