What is feline chlamydophila disease?   

Feline chlamydophila disease refers to infection with a type of bacterium called Chlamydophila felis. Many different strains of chlamydia type bacteria exist. In general they are highly species specific - ie, each strain usually infects one or a small number of different animals. The bacterium that infects cats, known as Chlamydophila felis, appears to be highly adapted to the cat and rarely, if ever, causes disease in other animals.

Chlamydophila organisms are very fragile and cannot survive for any significant period of time in the environment. Infection therefore occurs through direct contact between animals.

What disease does C felis cause in cats?
In cats, C felis mainly causes conjunctivitis (infection and inflammation of the delicate membranes or conjunctiva that cover the inner surface of the eyelids and the white part of the eye itself, called the sclera). Clinical signs usually develop within a few days to a week after infection and usually begin as a watery discharge from one or both eyes. Although sometimes only one eye is affected when signs first develop, within a few days both eyes become involved. Due to the discomfort, affected cats may hold their eyelids partially closed. As the disease progresses, severe swelling and reddening of the conjunctiva may be seen and the discharge changes from watery to a thicker yellowish discharge. Although conjunctivitis is the major clinical sign, there may also be mild sneezing and nasal discharge in some affected cats. Occasionally there is a mild fever which can result in lethargy and inappetence but, generally, affected cats remain bright and eat well. If left untreated, the conjunctivitis often persists for six to eight weeks or longer and cats may continue to shed the organism for many months.

Although mainly a cause of conjunctivitis, C felis has also been found in the lungs, gastrointestinal tract and reproductive tract of cats and there is some speculation that it may be a cause of infertility in breeding queens.

Which cats are at risk of infection?
Chlamydophila infection is relatively common in cats and up to 30% of cases of chronic conjunctivitis may be caused by this organism. However, because the organism does not survive in the environment and requires direct contact between cats to spread, disease is much more commonly seen where larger groups of cats are kept together, such as multi-cat households, catteries and shelters.

Although cats of all ages can be infected, disease is seen most commonly in young kittens (5 - 12 weeks old) with persistent or recurrent infection.

Are there other causes of conjunctivitis?
Although chlamydophila infection is a common cause of conjunctivitis in cats, many other causes of conjunctivitis exist. These can range from trauma to the eye, the presence of ocular irritation caused by foreign material in the eyes or hairs rubbing on the surface of the eye, through to other infectious agents. The cat flu viruses (herpesvirus and calicivirus) are common causes of sneezing together with ocular and nasal discharge in cats and they too can cause conjunctivitis. As with chlamydophila, cat flu viruses are more common in kittens and where groups of cats are kept together. Some cats can be infected with both flu viruses and chlamydophila.

How is chlamydophila disease diagnosed?
Because there are other potential causes of conjunctivitis, definitive diagnosis requires demonstration of the presence of the organism. Swabs can be taken from the eyes of affected cats and sent to specialist laboratories where the presence of the organism can be identified (through culture or other special techniques). This is usually a highly reliable way of making a diagnosis.

What is the treatment for affected cats?
Chlamydophila infections respond well to a number of different antibiotics. A group of antibiotics known as tetracyclines have generally been considered the treatment of choice for chlamydophila in cats. Certain other antibiotics may also be effective, but have to be chosen carefully as a number of antibiotics are completely ineffective against the organism. Topical therapy with eye drops or ointment is usually recommended, but this should be combined with systemic (oral) therapy as the organism can be present at sites other than just the eyes. If giving eye drops is difficult, infections will still respond well to oral therapy alone. Generally, treatment is recommended for a period of four weeks and all cats in the household should be treated (irrespective of whether they are showing clinical signs). Care has to be taken treating pregnant cats and young kittens (giving tetracyclines during development of the teeth can lead to their discolouration) and at this time other antibiotics may be used.

Can chlamydophila disease be prevented?
A vaccine exists to protect cats against chlamydophila conjunctivitis. The vaccine does not always prevent infection, but is certainly helpful in preventing severe clinical disease. Its use can be recommended in high risk situations.

Can humans catch infection from cats?
Humans can be infected with chlamydia but the bacterium that infects cats, Chlamydophila felis, is highly adapted to this species. There have been one or two reports that have suggested human conjunctivitis has occurred following contact with a cat harbouring C felis, but the risk appears to be extremely low. Routine hygiene precautions are recommended when handling and treating infected cats (washing hands after stroking or giving medications and avoiding close face-to-face contact until the infection has resolved).

Updated November 2008