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 from around two months to one year of age, with kittens of two to six months at highest risk. Maternally derived antibody from colostrum protects most kittens through the first one to two months, and susceptibility rises as that protection fades. 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.
Mild sneezing, nasal discharge, or a dip in appetite
Some cats show a small amount of sneezing or a thin nasal discharge alongside the eye signs, together with a short-lived reduction in appetite or energy and sometimes a mild fever. These accompanying signs are usually much less pronounced than the eye involvement and are not the dominant feature of the illness.
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 ointment containing chlortetracycline is applied directly to the affected eye several times daily. Where topical treatment is used, it is generally continued for the same period as a systemic course, four weeks and at least two weeks after the signs have settled, because shorter systemic courses have been followed by relapse. The UK-authorised chlortetracycline eye ointment is licensed for bacterial conjunctivitis over a five-day course, so its use against *Chlamydia felis*, and over a course of this length, falls outside that licence and is prescribed under the veterinary medicines cascade. Oxytetracycline eye preparations are sometimes described, but none is UK-authorised for cats. 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, and a controlled trial found that topical treatment used on its own cleared clinical signs and the organism more slowly than a systemic course.
Systemic antibiotic therapy
Oral antibiotics such as doxycycline are given daily for four weeks, and for at least two weeks after the signs have settled. Doxycycline tablets are authorised in cats in the UK, and at least one datasheet lists respiratory infection caused by *Chlamydophila felis* (the older name for *Chlamydia felis*) with a recommended course of at least 28 days. 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.
Trade-offs: A controlled trial found that cats treated with systemic doxycycline cleared clinical signs and the organism itself faster than cats treated with topical therapy alone, which is reflected in guidance from feline infectious disease bodies built around a systemic course. 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. Doxycycline is generally avoided in pregnant or nursing queens because of potential effects on developing or nursing kittens; amoxicillin-clavulanate is an alternative in that situation and in very young kittens, although its use for this infection is off-licence under the cascade, and the full four-week course matters, as shorter courses have been followed by relapse. 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
*Chlamydia felis* causes mainly conjunctivitis, with at most mild and short-lived nasal signs in some cats, and it is not established as a driver of chronic upper respiratory disease. Chronic upper respiratory disease in cats is more often linked to other causes, such as lasting damage from an earlier viral infection, though the two conditions can affect the same young, multicat populations and be considered together when signs overlap.
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. A cornea that looks cloudy or ulcerated, or an eye held tightly closed as if painful, sits outside the conjunctival pattern typically seen with Chlamydophila alone and points to involvement of the cornea itself, with feline herpesvirus among the causes investigated. A cat that stays quiet, off its food or feverish for more than a day or two, or that is getting worse rather than better, also sits outside the mild and short-lived malaise seen with Chlamydophila alone, and raises the possibility of a concurrent or different cause. 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. Transmission to people is rare. The few published cases describe a follicular conjunctivitis that lasted for weeks in people in close contact with an infected cat, most of whom had a normal immune system; the organism spreads through contact with eye discharge, and hand-washing after such contact is the usual precaution described.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS