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Presence of paratuberculosis in dairy cows culled in Tizayuca SummaryBackground: paratuberculosis (PTB) is clinically characterized by diarrhea and progressive weight loss in ruminants, and causes economic losses due to decreased milk production, premature animal disposal, and increased veterinary treatment costs. The presence of PTB has been increasing in milk producing bovine farms in Mexico, yet epidemiology data from specific farms remains scarce. Objective: to determine the proportion of cows positive for Mycobacterium avium subsp. paratuberculosis (Map) among culled cows. Methods: in the present study, 40 culled cows from 25 farms located at the complejo agropecuario industrial de Tizayuca (CAITSA) in Hidalgo (Mexico) were evaluated for PTB presence by histopathological and microbiological studies. Tissue and rectal scraping samples were taken from all cows, and studied for presence of histopathology PTB-compatible lesions. Samples were processed for Map isolation on selective agar culture media; typical Map colonies were confirmed by polymerase chain reaction (PCR). Results: potential PTB infection was found in 25% (10/40) of the animals evaluated by histopathology and acid-fast bacilli (AFB) staining, but