Histopathological effects of azithromycin on broilers: immune system alterations and apoptotic changes

1. The following reports an in-vivo study to investigate the toxicity profile of the azithromycin drug in broilers.2. Ninety, 1-d-old Hubbard chicks were purchased from Dakahliah Poultry Company, Egypt and, on d 25 of age, were subdivided into three groups. Group 1 (G1, control) received only drinking water, Group 2 (G2, treatment 1) received 50 mg azithromycin/kg body weight (BW) and Group 3 (G3, treatment 2) received 300 mg azithromycin/kg BW. All treatments were administered orally. Immunological, histopathological, and immunohistochemical assays were performed to evaluate the effect of azithromycin on broiler health.3. The weights of bursa of Fabricius and spleen in azithromycin-treated broilers decreased, particularly in G3. A decrease in both the phagocytic activity and index was evident in the treated groups (G2 and G3). Prominent degenerative changes and necrosis of immune organs were observed in treated chicks. Furthermore, strong immunoreactivity to caspase-3 was observed in the G3 group, which indicated elevated apoptosis in immune organs following exposure to a high-dose of azithromycin.4. It was concluded that administering azithromycin in broilers at a dose of 300 mg/kg impaired the immune function, promoted apoptosis and induced many microscopical alterations in different organs.