Chlamydiae are obligate intracellular bacteria. They are ubiquitous and found in almost every avian and mammalian species and it has been estimated that up to 20% of the human population is infected with this organism. They are highly infectious, but rarely kill their host. There are three species – Chlamydia trachomatis, C. psittaci and the recently discovered C. pneumoniae;
This is the commonest cause of blindness in the world and is found in the tropics and the Middle East. It is entirely preventable. It commonly occurs in children and is probably spread by direct transmission or possibly by flies. Infection is bilateral and begins in the conjunctiva, with marked inflammation and scarring. Scarring of the upper eyelid causes entropion, leaving the cornea exposed to further damage. The corneal scarring that eventually occurs leads to blindness. The changes in the eye are sometimes accompanied by an upper respiratory tract infection.
Trachoma may also occur as an acute ophthalmic infection in the neonate.
The diagnosis is generally established by:
• The typical clinical picture
• The presence of intracytoplasmic inclusion bodies in conjunctival cells
Tetracycline ointment applied locally each day for 2-3 months is effective, as is systemic therapy with oral tetracycline or sulphonamide. In endemic areas repeated courses of therapy are necessary. Recent data suggest that eradication of the disease may be possible with azithromycin. Once infection has been controlled, surgery may be required for eyelid reconstruction and for treatment of corneal opacities. Community health education with respect to hygiene and earlier case reporting could malce a substantial impact on disease prevalence.
Lymphogranuloma venereum is caused by C. trachomatis serotypes L 1, 2 and 3 Genital infections are also caused by other strains of C. trachomatis. Psittacosis (ornithosis) Although originally thought to be limited to the psittacine birds (parrots, paralceets and macaws), it is now known that the disease is widely spread amongst many species of birds, including pigeons, turkeys, ducks and chickens, hence the broader term ‘ornithosis’. Human infection is zelated to exposure to infected birds and is therefore a true zoonosis. The causative organism, C. psittaci, is excreted in avian secretions; it can be isolated for prolonged periods from birds who have apparently recovered from infection. The organism gains entry to the human host by inhalation.
CLINICAL FEATURES AND TREATMENT
Respiratory infection C. pneumoniae strain TWAR causes relatively mild pneumonias in young adults, clinically resembling Mycoplasma pneumonia. Infection occurs in outbrealcs. Diagnosis can be confirmed by specific IgM serology. Treatment is with erythromycin or tetracycline.