Detecção molecular de agentes do Complexo de Doenças Respiratórias em suínos abatidos na Ilha do Maranhão

Abstract

Swine farming represents a sector of agribusiness with significant growth. However, bacterial and viral respiratory diseases pose a major sanitary challenge, directly impacting the economic gains of the activity. Thus, this study aimed to evaluate the occurrence of agents associated with the porcine respiratory disease complex (PRDC) in pigs slaughtered on Maranhão Island, Maranhão state, Brazil. A total of 150 lung samples from pigs, collected between 2019 and 2021 from various locations on the island—comprising one abattoir certified by the State Inspection System (65 samples) and six non-inspected slaughter points (85 samples)—were analyzed. These samples had been previously tested for Mycoplasma hyopneumoniae, with 44 confirmed positives. DNA extraction was performed using the Wizard Genomic DNA Purification Kit (Promega®), followed by detection of porcine circovirus type 2 (PCV2) via qPCR, and Actinobacillus pleuropneumoniae and Glaesserella parasuis via conventional PCR (cPCR). PCV2 was detected in 66.95% (n = 81) of samples, G. parasuis in 4.9% (n = 6), and no samples were positive for A. pleuropneumoniae. Coinfection between PCV2 and M. hyopneumoniae was identified in 35.8% (n = 48) of samples, while PCV2 and G. parasuis coinfection occurred in 2.4% (n = 3). Only one sample showed coinfection with G. parasuis and M. hyopneumoniae, and one exhibited coinfection with all three pathogens (PCV2–M. hyopneumoniae–G. parasuis). These findings confirm the presence of two etiological agents of the porcine respiratory disease complex, PCV2 and G. parasuis, alongside coinfections with M. hyopneumoniae. The high PCV2 positivity rate indicates widespread dissemination of this agent among slaughtered animals on Maranhão Island. Nevertheless, given the extensive clandestine animal movement in the state, its asymptomatic presence in additional municipalities cannot be ruled out, underscoring the critical need for epidemiological diagnostics. Understanding the dynamics of pathogen dissemination and persistence in herds is essential for mitigating the economic impacts of respiratory diseases in swine production.