Background: Cryptosporidiosis is an important zoonotic protozoan disease caused by Cryptosporidium species. In poultry, various species such as Cryptosporidium baileyi, C. galli, C. meleagridis, and C. avium have been reported. These organisms are capable of infecting the gastrointestinal and respiratory tracts, and transmission occurs via environmentally resistant oocysts. Infected birds may exhibit clinical signs such as diarrhea, lethargy, and respiratory disturbances. This study aimed to investigate the presence of Cryptosporidium spp. in broiler chickens in Mashhad County using parasitological and histopathological methods. Methods: A total of 300 broiler chicken carcasses were examined. Impression smears were prepared from the bursa of Fabricius, cloaca, trachea, and intestine, and stained using the modified Ziehl–Neelsen technique to detect oocysts. For histopathological evaluation, tissue samples were fixed in 10% neutral buffered formalin, processed routinely, and stained with hematoxylin and eosin (H&E). Results: Among the examined samples, only one was definitively identified as positive for Cryptosporidium oocysts, while two were considered suspected cases; however, these lacked the definitive morphological features required for confirmation. Histopathological examination of the studied tissues revealed no evidence of Cryptosporidium infection or characteristic lesions such as epithelial hyperplasia or inflammatory infiltration. Conclusion: The findings indicate a low prevalence of Cryptosporidium spp. in broiler chickens in Mashhad. This underscores the importance of maintaining proper hygienic and management practices in poultry farms to minimize the risk of cryptosporidiosis.

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