Avian chlamydiosis (psittacosis / ornithosis): diagnosis, prevention and control, and its zoonotic concerns

摘要

Chlamydiosis is a contagious disease of pet birds and poultry, having zoonotic implications caused by a bacterium Chlamydophila psittaci. In domestic and pet birds, Chlamydophila psittaci causes chlamydiosis often referred to as psittacosis or ornithosis or Parrot fever having a significant public health impact. A special feature of Chlamydophila is that it has a biphasic life cycle existing as elementary, reticulate and intermediate bodies. Young birds are generally more susceptible. The organisms are shed in the nasal and ocular secretions. Fecal material or feather dust is resistant to drying and can act as source of infection. Vertical transmission through eggs has been described for ducks and chickens; turkeys and a number of wild birds. Pneumonia is a constant feature and lesions involve multiple organs. A short lived immunity to infection develops. The major outer membrane protein (MOMP) is immunodominant in nature and has a protective role in immunity. Usual diagnosis is based on the isolation of the organism in chicken embryo and cell lines and staining with special stains like Gimenez; Castaneda or Macchiavello's. A wide variety of serological techniques including enzyme linked immunosorbent assay (ELISA); immunofluorescence and immunoperoxidase; agglutination tests are available. The advent of molecular techniques including polymerase chain reaction (PCR); restriction fragment length polymorphism and deoxyribonucleic acid (DNA) sequencing has greatly aided in the diagnosis. Lipopolysaccharide (LPS) and major outer membrane protein (MOMP); OmpA; pmp-gene and D na-K like protein are the main targets for serological as well as molecular detection techniques. Psittacosis in human is a disease of increasing concern and occurs in both sporadic as well as epidemic forms. Psittacines, pigeons and turkeys mainly transmit the disease. Elementary bodies (EB) are major source of human infection. Inactivated vaccines are used generally as there are chances of carrier infection with live vaccines and require multiple administration. Recently, DNA vaccines and ovotransferrin therapy have gained popularity. Strict hygiene and sanitation along with public awareness are essential to prevent the disease. The present review describes the avian chlamydiosis in detail focusing on the etiological agent, the disease and its epidemiology, and the trends in diagnosis, prevention, treatment and control along with its public health concerns.