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Chlamydial Conjunctivitis: Introduction |  |
| Etiology and Epidemiology: |
| Different strains of
Chlamydophila (Chlamydia)
psittaci
and
Chlamydia
pecorum
cause significant eye infection in cats, lambs, goats, and guinea pigs. These infections are occasionally transmitted to humans. (See also
intestinal chlamydial infections,
Intestinal Chlamydial Infections: Introduction.) Trachoma and inclusion conjunctivitis in humans are caused by
C
trachomatis
. |
| The disease in cats is also known as
feline pneumonitis, which is largely a misnomer because chlamydiae rarely cause pneumonia in cats. The infection usually involves the eye and mucosa of the upper respiratory tract (rhinitis, sinusitis, pharyngitis). Serologic surveys indicate that 2-12% of cats, depending on age and geographic location, have complement-fixing chlamydial antibodies. |
|
Chlamydial keratoconjunctivitis in lambs and goats can have significant economic impact, particularly in confinement flocks, in which up to 90% can become affected. Concurrently, lambs often have chlamydial polyarthritis (
Chlamydial Polyarthritis-serositis). Also, chlamydial abortions (
Abortion in Goats) have been seen in a goat herd affected simultaneously with chlamydial keratoconjunctivitis.
Chlamydial keratoconjunctivitis has been reported in dogs, cattle, horses, and pigs and can be produced experimentally in these species. |
| Conjunctival chlamydial infections, sometimes asymptomatic, are common in guinea pig herds (see
Eye and Ear Diseases). Conjunctivitis is usually seen in 4- to 8-wk-old animals. Genital infections cause salpingitis and cystitis in female guinea pigs, and urethritis in males. |
|  |
| Clinical Findings: |
|
Signs in cats range from serous to mucopurulent conjunctivitis and rhinitis. Early signs are unilateral, reddened, slightly swollen conjunctivae. The incubation period after exposure to an infected cat is 3-10 days. Bilateral conjunctivitis develops after a few days, and the conjunctivae become hyperemic and chemotic, with prominent follicles on the inside of the third eyelid in more severe cases. The signs are most severe 9-13 days after onset
and then subside over 2-3 wk. Some cats develop, with or without secondary bacterial or mycoplasmal infections, vascular keratitis, pannus, and corneal scarring. In some cats, clinical signs can last for weeks despite treatment, and recurrence is not uncommon. |
| Similar eye lesions occur in sheep and goats. Secondary infections in lambs and goats are also common and, if untreated, can lead to severe complications. |
Lesions:
| Inflammatory reactions in the conjunctivae are prominent, and various cells such as neutrophils, lymphocytes, plasma cells, and macrophages infiltrate early in the disease. These cells, together with conjunctival epithelial cells containing chlamydial inclusions, are found in smears made from conjunctival scrapings. Ulcerative keratitis with resultant penetration of the anterior chamber can also be found in severely affected cats or those with secondary infections. |
| |
| Diagnosis: |
| Diagnosis can be confirmed by demonstration of chlamydial inclusions in exfoliative cytologic preparations or by isolation of the chlamydial organism. Scrapings are prepared by lightly but firmly moving a spatula or sharp teaspoon over the conjunctiva and smearing the scraped material onto a glass slide; the preparation is air-dried and stained. The elementary bodies appear basophilic or purple if stained with Giemsa, and reddish if stained with Gimenez. Scrapings may also be
submitted for isolation of chlamydiae in chicken embryos or cell cultures or for PCR testing. A serologic diagnosis is difficult and requires paired samples taken during the acute and convalescent phases of the disease to compare antibody levels; occasionally, false seronegative results occur. |
| Chlamydial conjunctivitis in cats should be differentiated from herpesvirus and calicivirus infections, and in lambs and goats from mycoplasmal and other bacterial infections (eg, “pinkeye”). |
| |
| Prevention and Treatment: |
| Vaccines are available for chlamydiosis in cats but not for other species. The feline chlamydial vaccine does not completely protect the cat but significantly reduces severity and infection rates. |
| All
C
psittaci
isolates are susceptible to tetracyclines. In cats, ophthalmic ointments that contain tetracycline may be the only therapy necessary. However, in severe or recurring cases, oral or parenteral treatment with tetracyclines is advisable. Cats that are pregnant or have kidney disease should be treated with erythromycin. |
| Systemic rather than ophthalmic treatment with oxytetracycline (20 mg/kg/day) or tylosin starting early in the course of the disease is advisable in lambs and goats. Daily feeding of 150-200 mg of chlortetracycline to affected lambs in feedlots also reduces the incidence of conjunctivitis and polyarthritis. |
| To reduce recurrence, treatment in cats, lambs, and goats should be continued for 7-10 days after clinical signs disappear. |
| |
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