Sulfaquinoxaline Toxicosis in a Juvenile Broiler Breeder Flock.

A flock of 50,000 28-day-old broiler breeder chickens experienced an elevated mortality event. Chickens from that flock, five pullets and six cockerels, were submitted for diagnostic investigation. Necropsy revealed bacterial septicemia with fibrinous polyserositis in the majority of the birds while two cockerels had coccidial typhlitis. Because sulfadimethoxine was not available at the time, sulfaquinoxaline (SQ) was prescribed at label dosage with water treatment for 2 days, followed by 3 days of no medication, followed by 2 days of medication. The mortality rose dramatically 9 days after the last treatment. Lesions at that time consisted of skin discoloration, subcutaneous petechiation, and enlarged pale kidneys. Mortality remained elevated for 14 days. Analysis of blood, kidney, and liver revealed elevated levels of SQ. Recalculation of dosage, water consumption, amount of drug administered, remaining drug stock, and concentration of supplied SQ were analyzed and determined to be as predicted.