The Development of a Non-Infectious Carrier State in Chickens Infected with Mycoplasma Gallisepticum

Abstract

SUMMARY A correlation was sought between the duration of infection, infectivity, agglutinin production and respiratory tract histopathology in Rhode Island Red chickens experimentally infected with M. gallisepticum by infra-orbital sinus inoculation. Ten out of fourteen susceptible chickens became infected with M. gallisepticum after 4 weeks contact with six primaries inoculated 12 weeks previously; two out of fourteen further chickens developed infection after 7 weeks contact with six primaries infected 24 weeks previously; but none of fourteen birds developed infection after 12 weeks contact with six primaries infected 36 weeks previously. M. gallisepticum was isolated from the upper respiratory tracts of four out of six, two out of six and three out of six primaries at each stage of the experiment respectively. The blood of the primaries contained agglutinins throughout the experiment. The histopathology of the upper respiratory tracts of both primaries and contacts is described. It is concluded that the prolonged presence of M. gallisepticum agglutinins in a chicken flock can be associated with a non-infectious carrier state.