Diseases of poultry aspergillosis are recorded in many poultry farms, the causes of the disease are the violation of the sanitary and hygienic conditions of hatcheries and poultry houses (unfavorable microclimate, affected feed and litter by microscopic fungi). To prevent the development of infection, it is necessary to control air pollution and equipment in hatcheries; determine the safety indicators of feed and water (the level of their mycological contamination) in poultry houses; monitor the status of feed storage facilities and water supply systems. According to the results of our research, in 15.1% of dead chickens at the age of 3 to 5 days and 6.6% at the age of 7-10 days, according to the results of mycological examination of pathological material, the diagnosis of aspergillosis was established. Aspergillus flavus (47%) Aspergillus fumigatus (34.5%), Aspergillus niger (10%) were isolated from the lungs of dead chickens. Macroscopically revealed edema and hyperemia of the lungs in chickens of 3-5 days of age. The formation of granulomas in the lungs and serous membranes was not detected, which may indicate an acute form of the pathological process. Chickens 7-10 days old showed a strong thickening of the air sacs, lungs with multiple spherical granulomas up to 2 mm in diameter. Spores of fungi entering the lungs cause a local inflammatory reaction - acute pneumonia. Histologically, in chickens of 3-5 days of age, a thickening of the parabronchial wall due to hyperplasia of local lymphoid formations (providing local immunity), signs of the development of interstitial pneumonia were revealed. Pathognomonic signs were found in the parenchyma - the formation of giant multinucleated cells, which is a characteristic sign of mycotic infections in poultry. The fusion of local pulmonary macrophages, histiocytes, into multinucleated cells is a prerequisite for the formation of granulomas, being a specific immune response in birds to the penetration of a pathogen. According to the development of the infectious process, caseous granulomas and fungal hyphae can be detected microscopically in the lungs. According to the results of histological examination, the formation of mycotic granulomas was found in the lung parenchyma in 7-10 days old chickens, which was accompanied by the formation of a zone of coagulation necrosis, in which the fungal hyphae were found. On the periphery, giant multinucleated epithelioid cells are located, the detection of which by histological examination is the basis for suspecting bird infection with microscopic fungi. Microscopic fungi Aspergillus flavus and Aspergillus fumigatus have been found in washes from hatchery ventilation cabinets, and Aspergillus flavus was found in the air from the chick sorting room and in washes from the feed mixer.

Key words: aspergillosis, Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, micromycete, mold fungi, histiocytes, granulomas, phylaids, conidia, hyphae.