CHLAMYDOPHILA IN A STUD CAT

History

A 12 month old, male entire, Birman cat presented with a 2 week history of mild ocular discharge and reddened conjunctiva. The cat was kept with a small harem (3) of breeding queens but separate from the majority of the cats in the cattery (approximately 30 others). No other cats were reported to be ill or have any ocular signs. All cats were routinely vaccinated for feline calicivirus, panleucopaenia and herpes virus.

Examination

A full clinical examination was undertaken along with an ophthalmic examination as per Appendix 1. All relevant findings are recorded below. Three months previously the cat had been tested negative for FIV/ FeLV (using an ELISA) prior to breeding.

OD: - Moderate seromucoid discharge with periocular crusting

OS: - Mild crusting medially

OU: - Hyperaemic conjunctiva with mild chemosis

- Negative for fluorescein dye retention

- Negative for rose bengal dye retention

STT L = 18mm/minute, R = 20mm/minute

Conjunctival swabs were taken for Chlamydophila felis PCR, FHV PCR and routine bacterial culture and sensitivity.

Ocular examination was otherwise unremarkable

(fig. 28). Figure 28: On presentation.

Diagnosis

Conjunctivitis:

- Bacterial

- Viral

- Irritative

- Allergic

Treatment

Pending results from sampling treatment was started with chlortetracycline ointment (Aureomycin, Fort Dodge) TID OU.

Laboratory Results

Chlamydophila felis antigen (immunodiffusion test) - Positive

FHV - Negative

Routine aerobic and anaerobic culture - no organisms isolated

Follow Up Treatment

Azithromycin (Zithromax, Pfizer) at 20mg/kg PO in a single dose, repeat at 7 days.

Follow Up

Conjunctival swabs were repeated 14 days later for Chlamydophila antigen and were negative. Further swabs were taken 12 months and 24 months later and the cat has remained negative for Chlamydophila antigen with no recurrence of clinical signs.

Discussion

Chlamydophila felis (previously Chlamydia psittaci var. felis) is an obligate intracellular bacteria with gram negative cell walls and is recognised as being a primary cause of conjunctivitis. It is often found in conjunction with FHV although not in this case.

Chlamydophila has an extracellular, infective particle called an elementary body. These enter host cells and develop into larger reticulate bodies which create more elementary bodies that are then released. Natural transmission is by close contact with infected cats and via fomites. Venereal transmission has never been proven. The elementary bodies are relatively fragile, only last a few days in the environment and are easily inactivated by detergents (1).

This stud cat had not been exposed to any cats from other catteries however one of his harem of females had been to another cattery to be served 4 months previously. The female had shown no ocular signs, neither had her kittens, however this was thought to be the most likely route of infection for this cat.

The treatment of choice for Chlamydophila is doxycycline at 10mg/kg SID for a minimum of 3 weeks and up to 6 weeks has been suggested in some cases (1). All in-contact cats must be treated to eradicate the organism. Cats are most likely to be infected when less than 1 year of age however it is postulated that shedding continues in asymptomatic cats thus perpetuating the disease.

Due to the number of cats that would require treatment, their breeding status and the young age of some of the in-contacts the owners were most reluctant to treat the whole cattery with doxycycline. Drawbacks of doxycycline treatment include the long course needed and the frequency of treatment, which often leads to non compliance. Azithromycin has been suggested as a possible treatment for Chlamydophila in cats as it is used effectively as a single dose to treat Chlamydia trachomatis genital infections in humans (3).

Azithromycin is rapidly absorbed and has good bioavailability in the cat. It has a long half-life, good tissue penetration and is well retained within tissue. It also appears to be well tolerated given both orally and intravenously (2). The drug would therefore appear to be a good choice for use against Chlamydophila. It is thought to be bacteriostatic at lower doses and bacteriocidal at higher ones.

Azithromycin has been used to treat Chlamydophila at 10-15mg/kg PO, both with daily dosage and twice weekly dosage but it was not successful in eliminating Chlamydophila at either of those dose regimes (3). Given at 5mg/kg azithromycin failed to reach minimum inhibitory concentrations within the eye however conjunctival tissue should achieve better levels than intraocular tissue but this was not specifically measured (2).

A single dose of azithromycin was used in this case at 20 mg/kg PO. This is a concentration dependent antibiotic with a long elimination time so this could be a useful regime. This regime and dosage is used in the USA and Australia by cattery owners and appealed to my client due to ease of administration (Dr D Richardson, personal communication).

The ease of administration of the regime used allowed all in contact cats to be treated including the kittens with no noted ill effects. None of the treated cats have shown any ocular signs since treatment and there have been no other ocular signs within the remainder of the cattery (although that is run as a closed unit).

Doxycycline, apart from the prolonged administration, has significant complications such as permanent discolouration of the teeth and bones if given to pregnant cats or young kittens, and also oesophageal ulceration/ stricture (4). In young cats it has been suggested to give amoxicillin potentiated with clavulanic acid to suppress the disease and possible shedding, but then to give a course of doxycycline when the teeth have fully developed. Amoxycillin with clavulanic acid does not however eradicate the disease so the cats should be isolated from disease free stock until doxycycline has been given (5).

It should also be noted that doxycycline is a licensed product (Doxyseptin, Vetoquinol) whereas azithromycin is unlicenced for animals. No studies have shown that azithromycin will eradicate the disease and the manufacturer makes no such claims. However this cat appears to have remained free from the disease with no recurrence of clinical signs and no organism found on PCR.

References

1. Sykes JE (2005) Feline Chlamydiosis. Clinical Techniques in Small Animal Practice May: 20(2), 129-134.

2. Hunter RP, Lynch MJ, Ericson JF, Millas WJ, Fletcher AM, Ryan NI, Olson JA (1995) Pharmacokinetics, oral bioavailability and tissue distribution of azithromycin in cats. Journal of Veterinary Pharmacology and Therepeutics. Feb:18 (1), 38-46.

3. Owen WMA, Sturgess CP, Harbour DA, Egan K, Gruffydd-Jones TJ (2003) Efficacy of azithromycin for the treatment of feline chlamydiosis. Journal of Feline Medicine and Surgery. 5, 305-311.

4. German AJ, Cannon MJ, Dye C, Booth MJ, Pearson GR, Reay CA, Gruffydd-Jones TJ (2005) Oesophageal strictures in cats associated with doxycycline therapy. Journal of Feline Medicine and Surgery 7, 33-41.

5. Sturgess CP, Gruffydd-Jones TJ, Harbour DA, Jones RL (2001) Controlled Study of the efficacy of clavulanic acid-potentiated amoxicillin in the treatment of Chlamydia psittaci in cats. The Veterinary Record, vol 149, issue 3, 73-76.