CONDITION
Chlamydophila Conjunctivitis in Cats
Chlamydophila conjunctivitis in cats is an infection of the tissues around the eye caused by the bacterium *Chlamydia felis*. The infection leads to inflammation of the conjunctiva—the thin membrane lining the eyelids and covering the white of the eye—and typically produces redness, swelling, and discharge that may start clear and later become thicker or coloured. The infection often begins in one eye but tends to become bilateral within a day or two. Owners may notice squinting, a red or swollen appearance around one or both eyes, or discharge that prompts wiping or cleaning. Young cats are most commonly affected, and signs tend to be most pronounced around nine to thirteen days after onset, then gradually ease over the following weeks, though the conjunctivitis can persist if untreated. The condition is distinct from other common causes of feline conjunctivitis, such as herpesvirus or calicivirus. This page explores the signals that may appear, what is happening beneath the surface, how the infection is investigated, and the approaches that exist for managing it.
Why this matters now
Chlamydophila conjunctivitis tends to appear in young cats, most commonly between five weeks and one year of age, with kittens around two to six months particularly susceptible. Maternal immunity derived from colostrum typically wanes at around six to eight weeks, leaving young cats vulnerable to infection during this period. The condition is seen more frequently in multicat households, breeding catteries, and among pedigree cats, where close contact facilitates transmission. Signs may appear three to ten days after exposure to the bacterium.
The infection often begins with signs in one eye, then typically becomes bilateral within a day or two. Conjunctival inflammation and discharge tend to be most pronounced around nine to thirteen days after onset, then gradually ease over the following two to three weeks. In some cats, however, signs can persist for weeks or recur even after the initial phase has settled, and the pattern of resolution varies between individuals.
Signals & patterns
Early signals
Redness around one eye
The conjunctiva—the thin membrane lining the eyelid and covering the white of the eye—may appear pink or red, often beginning in one eye before the other is affected. The change can be subtle at first, with the colour deepening over the first few days.
Clear or watery discharge
A thin, clear discharge may accumulate in the corner of the eye or along the lower lid, prompting the cat to blink more frequently or paw at the area. This early discharge is typically serous rather than thick or coloured.
Mild squinting or narrowing
The affected eye may appear slightly narrower than usual, or the cat may blink more often or hold the eyelid partially closed. This reflects discomfort from the inflamed conjunctival surface.
Swelling of the conjunctiva
The tissue around the eye may appear puffy or thickened, sometimes with a glistening or wet appearance. This swelling, called chemosis, can make the membrane look more prominent than usual.
Later signals
Thicker or coloured discharge
As the infection progresses, the discharge may become thicker, creamy, or yellow-green in colour, requiring more frequent cleaning. This change reflects an accumulation of inflammatory cells and debris.
Protrusion of the third eyelid
The nictitating membrane—a thin fold of tissue in the inner corner of the eye—may become more visible, sometimes extending partway across the eye. In more pronounced cases, small raised bumps (follicles) may appear on the inner surface of this membrane.
Persistent redness in both eyes
By this stage, both eyes are typically affected, with ongoing conjunctival inflammation that may fluctuate in intensity over several weeks. The pattern of redness and discharge can vary from day to day.
Click to read about the biological mechanisms
How this is usually investigated
Diagnosis typically begins with a history of the signs observed and their progression, followed by examination of the eyes and surrounding tissues. The clinical appearance—particularly the pattern of conjunctival inflammation, the nature of the discharge, and whether one or both eyes are affected—can suggest Chlamydophila infection, though other causes of feline conjunctivitis may produce similar signs. Laboratory tests can confirm the presence of *Chlamydia felis* and help distinguish it from viral or other bacterial causes.
Physical examination
Conjunctival swab for polymerase chain reaction (PCR)
Conjunctival cytology
Bacterial culture and sensitivity
Options & trade-offs
Management typically involves addressing the infection itself, supporting comfort during the period of inflammation, and reducing the risk of transmission to other cats in the household. The combination of approaches used tends to be shaped by the severity of signs, the number of cats in the home, and the practical realities of administering treatment. Different households find different strategies workable, and the course of the infection can vary between individuals.
Topical antibiotic therapy
Antibiotic eye drops or ointments containing tetracycline derivatives such as oxytetracycline or chlortetracycline are applied directly to the affected eye several times daily. The treatment is typically continued for three to four weeks, even if signs begin to improve earlier, to reduce the risk of relapse. Topical therapy delivers high concentrations of antibiotic to the conjunctival surface where the bacteria reside.
Trade-offs: Application requires restraint and cooperation from the cat, which can be challenging in some individuals, particularly over a prolonged course. Topical treatment alone may not fully clear the infection from other mucosal sites, such as the gastrointestinal tract, where *Chlamydia felis* can persist.
Systemic antibiotic therapy
Oral antibiotics such as doxycycline are given daily for a period of four to six weeks. Systemic therapy reaches the conjunctiva as well as other potential sites of infection, including the nasal passages and gastrointestinal tract, and may reduce shedding of the organism more effectively than topical treatment alone. Tablets or liquid formulations can be used depending on what is tolerated.
Trade-offs: Doxycycline can cause oesophageal irritation in cats, particularly if tablets lodge in the oesophagus rather than reaching the stomach, so administration with or followed by food or water is often advised. Some cats resist oral dosing, and the extended duration of treatment can be demanding for owners.
Supportive care and environmental management
Gently cleaning discharge from around the eyes with damp cotton wool can reduce crusting and improve comfort. Isolating affected cats from others in the household during the period of active signs may reduce transmission, though *Chlamydia felis* is less contagious than some viral causes of feline conjunctivitis. Environmental cleaning with routine disinfectants can help reduce environmental contamination, though the bacterium does not survive long outside the host.
Trade-offs: Supportive care alone does not address the underlying infection and signs may persist or recur without antimicrobial treatment. Isolation is not always practical in multicat households, and some cats find separation stressful.
Vaccination in multicat settings
A vaccine against *Chlamydia felis* is available and may be considered in households or catteries where the infection recurs or where multiple cats are at risk. Vaccination does not prevent infection but can reduce the severity and duration of clinical signs in vaccinated individuals. It is typically given as part of a combination vaccine and requires booster doses to maintain protection.
Trade-offs: Vaccination does not eliminate the risk of infection or shedding, and vaccinated cats can still develop conjunctivitis, though signs tend to be milder. The vaccine is less widely used than those targeting core feline pathogens and may not be routinely stocked in all practices.
Common misconceptions
"Chlamydophila conjunctivitis will resolve on its own without treatment within a few days."
While some cats may show gradual improvement over several weeks, the infection often persists or recurs without antimicrobial therapy, and signs can continue for much longer than the initial week or two. Untreated cats may also continue to shed the organism, posing a risk to other cats in the household.
"The infection is highly contagious and spreads as readily as feline flu viruses."
*Chlamydia felis* is transmitted primarily through direct contact with ocular or nasal secretions and does not survive well in the environment, so transmission is less efficient than for feline herpesvirus or calicivirus. Infection tends to spread more slowly and close, sustained contact is typically required.
"Once the discharge clears, treatment can be stopped."
The bacterium can persist in the conjunctival tissues even after visible signs have improved, and stopping treatment too early may allow the infection to recur. Extended courses of several weeks are often needed to clear the organism and reduce the likelihood of relapse.
Related conditions
Feline Herpesvirus (FHV-1)
Feline herpesvirus is one of the more common causes of conjunctivitis in cats and can produce signs that overlap with those of Chlamydophila infection, including redness, discharge, and squinting. The two infections may sometimes occur together, and laboratory testing can help distinguish or confirm concurrent disease.
Feline Calicivirus
Feline calicivirus can cause conjunctivitis alongside oral ulceration and upper respiratory signs, and may occasionally be present at the same time as Chlamydophila infection. The pattern of discharge and the presence or absence of oral lesions can help differentiate the two.
Chronic Upper Respiratory Disease in Cats
Chronic upper respiratory disease in cats can follow or accompany recurrent or persistent conjunctivitis, including cases where Chlamydophila infection contributes to ongoing inflammation. Both conditions tend to affect young cats and may appear together in multi-cat environments.
Flea Allergy Dermatitis
Conjunctivitis in cats is sometimes part of a broader pattern of inflammation, and conditions affecting other body systems—such as feline asthma or other allergic responses—may occasionally appear in the same individual, though each has distinct triggers and pathways.
Understanding the typical course of Chlamydophila conjunctivitis can help owners recognise when signs are following an expected pattern and when they may indicate a complication or concurrent condition. Conjunctivitis in cats can have multiple causes, and some cats may be affected by more than one pathogen at the same time. For households with multiple cats, thinking through the practicalities of treatment and isolation early in the course of the condition can make management more workable.
Last reviewed: 12 September 2026 · Dr Alastair Greenway MRCVS