Use of lipopolysaccharide (LPS) as a positive control for the evaluation of immunopotentiating drug candidates in experimental avian colibacillosis models

The aetiologic agent of avian colibacillosis is Escherichia coli. Colibacillosis is a disease that causes mortality and production performance problems in chickens which results in economic losses for the poultry industry. It will be increasingly important for scientists to identify novel solutions that can be implemented which will provide poultry producers with a tool to manage this economically important disease. The purpose of this investigation was to determine whether lipopolysaccharide (LPS) could be used as a positive control to evaluate novel chemistries for immunopotentiator activity in battery or floor-pen avian colibacillosis models in chickens. In the battery study, subcutaneous administration of LPS to one-day-old broiler cockerels caused a significant reduction (P < 0.003) in all parameters of colibacillosis evaluated, i.e. mean air sac lesion scores, per cent air sac lesions, E. coli re-isolation and per cent mortality. However, in the floor-pen study, subcutaneous administration to one-day-old broiler chicks resulted in a numerical, but not statistically significant reduction (P < 0.1) in mortality associated with colibacillosis. These data indicate that LPS can be used as a positive control to evaluate the efficacy of immunopotentiator drug candidates in avian colibacillosis models.