Chlamydiae as agents of human and animal diseases

A brief review is given of the properties, occurrence, and public health significance of chlamydiae in man and animals and of the diagnosis and control of chlamydial infections. Chlamydiae occur naturally in a large number of avian and mammalian species. Man is the primary host of chlamydiae causing trachoma, inclusion conjunctivitis, genito-urinary tract infection, and lymphogranuloma venereum. In animals chlamydial infections have been recognized as a cause of pneumonia, encephalitis, abortion, arthritis, diarrhoea, and conjunctivitis. Chlamydial infections have been recognized in a wide range of avian hosts. Sporadic psittacosis/ornithosis in man is associated with close exposure to birds and may occur as an occupational disease. Transmission studies suggest that mammalian chlamydial strains are not very host-specific and that diseases and even chains of infection may develop in secondary hosts. There are a few well-documented cases of human infection with chlamydiae of mammalian origin. Although various chlamydial isolates have specific antigenic components, no routine test for identifying different serotypes has been generally accepted. Further investigation of the host range of chlamydiae and of their antigenic properties is essential for a more accurate assessment of the potential danger of chlamydia-infected animals to human health. The frequent occurrence of inapparent or latent infections makes it imperative to establish adequate laboratory facilities for the effective surveillance and control of chlamydial infections.