Int. J. Adv. Res. Biol.Sci. 1(8): (2014): 74–85 74 International Journal of Advanced Research in Biological Sciences ISSN : 2348-8069 www.ijarbs.com Research Article Pathological investigation of avian Aspergillosis in commercial broiler chicken at Chittagong district Shirin Sultana 1* , S. M. Harun-ur-Rashid 1 , Md. Nazrul Islam 1 and Md. Zulfekar Ali 2 1 Department of Pathology and Parasitology, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur, Bangladesh 2 Department of Microbiology, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur, Bangladesh *Corresponding author: shirin_vet@yahoo.com Abstract The present study was carried out to investigate the pathology of avian aspergillosis in commercial broiler chickens at Chittagong district. A total of 912 sick and dead chickens were collected from 20 commercial broiler farms and diagnosed for avian aspergillosis on the basis of clinical signs, symptoms and postmortem findings. The suspected birds were collected for necropsy examination and mycological culture. Gross lesions of multiple hard creamy to yellow colored, circumscribe plaques throughout the lungs surface and consolidated lung with necrotic areas were observed. Microscopically, the typical nodules consisted of caseous necrotic center were present. Identified the Aspergillus spp according to their color of colony growth on Potato Dextrose Agar media. The overall incidence of avian aspergillosis was found 6.14%. Among five Upazilla, significantly (p<0.007) higher and lower incidence was found in Patenga and Sitakunda that were 9.25% and 3.43% respectively. It was observed that highest incidence (8.22%) in rainy and lowest (3.16%) in winter but moderate (5.16%) in summer season. The disease was significantly (p<0.050) higher (8.27%) in age between 6-10 days and lower (4.11%) in age between 0-5 days. It was also found that incidence of avian aspergillosis was significantly (p<0.042) higher in flocks reared on sawdust litter (7.69%) as compared to rice husk litter (3. 46%). Keywords: Aspergillus , Incidence, Litter Introduction Poultry farming is emerging as a strong agro-based industry from the backyard poultry rearing system to commercial intensive rearing systems during the last two decades in Bangladesh. This rapid growth of poultry industry to supplement their income with the fast development of poultry industry, the occurrence of diseases has increased many folds which remain the major problem affecting its economy as a results disease play a vital role to better understand the status and pattern of diseases (Islam et al., 2003; Saleque et al., 2003 and Uddin et al., 2011). Aspergillosis is the most common fungal disease of the avian respiratory systems, it is an infectious, non- contagious fungal disease caused by species in the ubiquitous opportunistic saprophytic genus Aspergillus, in particular Aspergillus fumigatus (Richard, 1991; Barnes and Denning, 1993). This mycosis was described many years ago, but continues to be a major cause of mortality in captive birds and, less frequently, in free-living birds. Although aspergillosis is predominantly a disease of the respiratory tract, all organs can be involved. It is believed that impaired immunity and the inhalation of