ABSTRACT
Five groups of chicks were infected with infectious bronchitis virus IRFIBV32 isolate, 1 10sup4/sup EID50, by eye drop and avian influenza virus H9N2 subtype, 1 10sup9/sup EID50, intranasally. Thirty-six hours after inoculation, one group received 50 mg/kg BW sodium salicylate, another 20 mg/kg doxycycline with 30 mg/kg erythromycin, and another group 12.8 mg/kg the expectorant guaifenesin for 3 days via drinking water. Lastly another group of birds were given the 3 drugs simultaneously at the same doses mentioned above. Infected controls were infected with both viruses but not treated, and normal controls inoculated with sterile saline and not treated. One day before challenge and at the end of experiment, birds were bled and sera tested for IB and AI antibodies by ELISA and H9N2 antigens. After viral challenges clinical signs and lesions were scored and tracheas tested for IBV by RT-PCR. Compared with infected controls, sodium salicylate or antibiotics reduced mortality, tracheal histopathology or symptoms. However, the expectorant guaifenesin given in drinking water, exarcebated signs and histopathology but reduced overall mortality. Treatment with the combined drugs decreased mortality rate and reduced clinical sign scores most compared with other treatments or infected controls.