Reduction of Chlamydophila-felis-associated signs by roxithromycin treatment regimen in cats showing doxycycline intolerance

Chlamydophila felis (C. felis) causes chronic conjunctivitis in cats, and is frequently treated with tetracyclines. However, tetracyclines may cause gastrointestinal side effects, such as vomiting, loss of appetite, diarrhoea, and increased liver enzyme activity in some pets. We evaluated the effect of a four-week treatment regimen with roxithromycin - RXM (Rulid® Sanofi-Aventis, France) in 14 cats with conjunctivitis that tested C. felis-positive, and exhibited doxycycline intolerance. The treatment was given for four weeks. Assessment of clinical disease was performed on Day 0 and Day 56. Changes in severity of clinical signs were assessed on a three-step scale (increased, decreased, or no changes) every week of the therapy (Days 7, 14, 21, and 28). Additionally, conjunctival swabs were collected on Days 0 and 56 from each animal, and the C. felis-count was assessed through amplification of the ompA gene by real-time PCR with fluorogenic probes and normalisation to the feline DNA signal. Animals receiving RXM improved regarding the ophtalmological parameters related to manifestation of conjunctivitis, severity of ocular discharge and nasal discharge and breathing patterns (P ≤ 0.05). A visible improvement in relation to these parameters was already observed after two weeks of RXM administration. C. felis-counts decreased in nine cats that were given RXM, but in the other five C. felis was not eliminated. Interestingly, however, aggravation of symptoms was not observed in these five animals. Further studies are needed to fully confirm that a reduction of clinical signs and pathogen counts under conditions of natural infection can be attributed to RXM treatment, since there was no control group that received placebo or another drug in this study. The present results also indicate that in some cases 28 days of RXM administration will not be sufficient to eliminate infection.