Swine influenza is a respiratory infectious disease in pigs caused by Orthomyxoviridae influenza virus A. As a multihost pathogen, the virus can infect humans, birds, and pigs and has pandemic potential due to rapid mutation rate. This study investigated the seroprevalence of influenza A antibodies in pigs in Chungbuk Province to overview its temporal and spatial distribution. From March to November 2021, blood samples collected for swine fever and foot-and-mouth disease antibody tests from swine farms located in Cheongju, Jincheon, Jeungpyeong, and Goesan within the jurisdiction of the Chungbuk Animal Health Laboratory were used. Blood samples from both sows and growing pigs were collected. Additionally, three farms participating in the Expendable Disease Guidance Support Project were chosen to investigate the seroprevalence status by parity of sows and age of piglets. A total of 468 sows and 1,519 growing-finishing pigs were employed in this study. The results showed that Jincheon had the highest seropositivity rate, suggesting that more effort should be made in biosecurity to prevent mechanical transmission, given the close proximity of farms. The analysis of antibody levels in farms targeted by the Expendable Disease Guidance Support Project could suggest that once the virus enters a farm, it spreads throughout the entire pig population regardless of age. Farms that were positive in the first half of the year remained positive in 86% of cases in the second half, suggesting continuous infection within the farm unless depopulation or all-in-all-out practices are implemented. Moreover, 67% of farms that were negative in the first half remained negative in the second half, and farms managed by the same person showed identical antibody change patterns, indicating that the swine influenza virus can be transmitted by humans or vehicles. The results highlight the need for further analysis of biosecurity systems and geographical risk factors.

Swine atrophic rhinitis is a respiratory disease that causes nasal turbinate loss and septal deformation due to Bordetella bronchiseptica and Pasteurella multocida. Turbinate loss facilitates pathogens to infect lungs, which leads to various respiratory diseases and productivity reduction. In this study, descriptive analysis was implemented for atrophic rhinitis and pneumonia. From 6 pig farms shipped to slaughterhouses in Chungbuk province, 20 heads and 20 lungs were collected by each farm from March 2020 to September 2020. Their atrophic rhinitis lesions and lung lesions were scored and blood samples were also collected to test the seroprevalence of several respiratory diseases. Pasteurella multocida from nasal swab was cultured and antibiotic resistance tests were performed. Correlation between atrophic rhinitis scores and lung lesion scores was not found. Abdominal nasal lesions were more severe than dorsal lesions. Differences in lung lesion scores were relatively small between lobes. The score of pneumonia was higher in castrated pigs than in female pigs. There was no relationship between lesion score and seroprevalence of respiratory diseases. Antibiotic resistance levels for Pasteurella multocida differed by farm, and several antibiotics were not effective. The results of this study imply that antimicrobial susceptibility tests are highly recommended before administration.