Observations on the pathogenicity of Alcaligenes faecalis in chickens

A series of trials was conducted in which specific-pathogen-free (SPF) leghorn chicks were exposed to various isolates of Alcaligenes faecalis. Chicks were inoculated with A. faecalis alone or in combination with Newcastle disease/infectious bronchitis (Nc/Br) vaccine, laryngotracheitis vaccine, infectious bursal disease virus, or Mycoplasma gallisepticum. The response was evaluated by morbidity, mortality, airsacculitis, reisolation of A. faecalis, and histopathological lesions of tracheas. Although A. faecalis was recovered up to 42 days postinoculation in some cases, no clinical signs were directly attributed to simple A. faecalis infection. None of the other agents significantly increased the severity of A. faecalis signs or lesions, except that A. faecalis-infected chicks that were given Nc/Br vaccine had prolonged microscopic tracheal lesions. In another trial, the effects of A. faecalis in young SPF leghorns, non-SPF broilers, and turkeys were compared. Broiler-type chicks were more susceptible than leghorns and less susceptible than poults. Consequently, the use of leghorns as a model for studying this infection is questioned.