Effect of dual infections of Escherichia coli and pure caecal Eimeria sp. in broiler chickens.

The interactive effect of Escherichia coli and pure caecal Eimeria spp. in broiler chickens was studied. Single and dual orally inoculations were assessed in six groups of 20 chicks each. Neither mortalities nor clinical signs were recorded on inoculated groups or control. There was a significant decrease in body weights in groups infected, either with E. coli or caecal Eimeria spp. or with both pathogens. The total oocyst output and caecal lesion score were high and severe in chicks infected with caecal Eimeria sp. alone or with E. coli prior to caecal Eimeria infection. Low oocyst output and moderate caecal lesion score were noticed in chicks inoculated with E. coli prior to or together with caecal Eimeria infection. The results suggested a synergistic action between E. coli and caecal Eimeria sp. in producing gross lesions. The electrophoretic distribution of serum proteins decreased in all chicks compared with control. The changes in serum protein fractions differed in inoculated groups and all protein components decreased quantitatively compared with controls. It was also shown that E. coli did not always invade the blood stream.