Chlamydiosis

Chlamydial pathogens cause a wide-range of infections and disease, known as chlamydioses, in humans, other mammals and birds. The causative organisms are Gram-negative obligate intracellular bacteria that undergo a unique biphasic developmental cycle involving the infectious elementary body and the metabolically-active, non-infectious reticulate body. At least two species, Chlamydophila psittaci and Chlamydophila abortus, are recognized as causes of zoonotic infections in humans worldwide, mainly affecting persons exposed to infected psittacine and other birds, especially ducks, turkeys, and pigeons, and less commonly to animals, particularly sheep. Outbreaks occur amongst aviary workers, poultry processing workers, and veterinarians. Infection is transmitted through inhalation of infected aerosols contaminated by avian droppings, nasal discharges, or products of ovine gestation or abortion. Person to person transmission is rare. Control strategies have met with variable success depending on the degree of compliance or enforcement of legislation. In the United Kingdom control is secondary, resulting from protection of national poultry flocks by preventing the importation of Newcastle disease virus using quarantine measures. Improved standards of husbandry, transport conditions, and chemoprophylaxis are useful for controlling reactivation of latent avian chlamydial infection. Vaccination has had limited effect in controlling ovine infection. Improved education of persons in occupational risk groups and the requirement for notification may encourage a more energetic approach to its control.