Immunization trials with an avian chlamydial MOMP gene recombinant adenovirus

Abstract

Avian chlamydiosis (AC) is an infectious disease caused by Chlamydophila psittaci. Named after psittacosis or ornithosis, the bacterium mainly harms domestic and wild birds. Early in the 20th century, it was fashionable to keep parrots as domestic pets. However, many of these birds were affected with ornithosis, leading to sporadic human outbreaks of AC. Hundreds of people died of AC in America, Europe and Africa 1, 2. AC exists in many parts of the world and can infect almost all bird species, including domestic poultry 3. When affected with AC, the mortality rate in infant birds is high, but decreases as birds reach adulthood. Between the 1960’s to 1970’s, the poultry industry in Europe suffered serious losses due to AC 4,5. Not restricted to Europe, AC cases involving duck, dove, chicken, turkey, goose and wild birds have also been reported in China. Indeed a mean positive rate of 10.96% AC has been reported in 18 provinces1. Furthermore, the incidence of AC cases appears to be increasing in some provinces. However, , despite this, no effective vaccine has yet been developed to control the disease. In the current study, specific pathogen free (SPF) chicks were immunized with an avian chlamydial major outer membrane protein (MOMP) gene recombinant adenovirus vector vaccine developed in our laboratory6. The minimal infection dose of the virulent strain, the most effective inoculation route of the vaccine and the minimal effective immunization dose were determined. Vaccine potency, security, protective period, and the conservation period of the vaccine were also examined.