Chlamydia
From Felipedia
Contents |
Introduction
Feline Chlamydia disease refers to a bacterial disease caused by Chlamydophila felis. Many different strains of Chlamydia type bacteria exist. In general they are highly species-specific - i.e. each strain usually infects one or a small number of different animals. Chlamydophila felis appears to be highly adapted to the cat, although zoonotic infection of humans with C. felis has been reported[1]. Chlamydia organisms are very fragile and cannot survive for any significant period of time in the environment. Infection therefore occurs through direct contact between animals.
Chlamydophila felis is endemic among house cats worldwide, primarily causing inflammation of feline conjunctiva, rhinitis and respiratory problems. C. felis can be recovered from the stomach and reproductive tract. Strains FP Pring and FP Cello have an extrachromosomal plasmid, whereas the FP Baker strain does not. FP Cello produces lethal disease in mice, whereas the FP Baker does not. An attenuated FP Baker strain is used as a live vaccine for cats.
Symptoms
In cats, Chlamydia mainly causes conjunctivitis (infection of the eyelids). 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 (usually the left eye), 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, Chlamydia has also been found in the lungs, gastrointestinal tract and reproductive tract of cats. It is a leading cause of infertility (failure to conceive), repeat heats, metritis/pyometron (infection of the uterus) and can also localise in joints, causing arthritis.
Chlamydia 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. Some cats can be infected with both cat flu and Chlamydia.
Diagnosis
Because Chlamydia can be confused with cat flu, the only way to accurately diagnose this disease is by conjunctival swabs, which are PCR cultured for the bacteria. Because of the difficulty in isolating Chlamydia from swabs taken from the cat, it is better to assume an infection exists and to treat with antibiotics rather than risking spreading the disease.
Treatment
Chlamydia is transmitted between cats by direct contact (including sexual) or by aerosol (sneezing), nasal discharges and from soiled paws (wiping away discharge from eye/nose). In breeding situations, physical transmission by humans is also possible.
Chlamydia 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 Chlamydia 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.
Azithromycin (Zithromax®) is effective against Chlamydia, given at 20mg/kg (80mg stat, once weekly x 4).
Prevention
A vaccine exists to protect cats against Chlamydia 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.
- New Cats - If you are buying a new breeder and you have little knowledge of the breeding cattery or cannot inspect it because it is interstate or distant I would advocate treating the new breeder with a single dose of Zithromax before introducing the cat to your resident population.
- Mating - because of the high incidence of Chlamydia infection in catteries, it is recommended that all cats be medicated with Zithromax immediately post-mating as a single dose to prevent metritis/pyometron.
- Pregnant Queens - It would seem that Chlamydia can exist in cats in a dormant form, and that some resistance is given to kittens by maternal antibodies which fade out at about 2 weeks after birth, which is when many kittens will get sick, develop pneumonia and die. If you have any suspicion your pregnant queen may have, have had, or have been exposed to Chlamydia (this probably includes most queens), I advocate giving a single dose of 20mg/kg of Zithromax on about the 58th day of pregnancy. At this stage there is no risk to the unborn kittens, who may otherwise contract Chlamydia from the queen during birth or soon after.
