China Animal Husbandry and Veterinary Medicine ›› 2023, Vol. 50 ›› Issue (6): 2439-2449.doi: 10.16431/j.cnki.1671-7236.2023.06.028

• Preventive Veterinary Medicine • Previous Articles     Next Articles

Epidemiological Investigation of Common Respiratory Bacterial Pathogens in Large-scale Pig Farms

CAO Qi1, JIN Qing1, YUAN Yi1, FENG Yixue1, KONG Danni1, CHEN Xianghong1, WU Bin2, SONG Wenbo1,2, TANG Xibiao1   

  1. 1. Wuhan Keqian Biological Co., Ltd., Wuhan 430223, China;
    2. College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China
  • Received:2022-11-16 Online:2023-06-05 Published:2023-05-30

Abstract: 【Objective】 The purpose of the test was to understand the infection status of the main bacterial pathogens responsible for porcine respiratory disease complex (PRDC) in large-scale pig farms in China.【Method】 A total of 2 204 samples of lungs, trachea and secretions, spleens and lymph nodes were collected from 647 large-scale pig farms with clinically obvious respiratory symptoms in 26 provinces, cities and autonomous regions of China in 2021.The sample was inoculated into the plate for purification and culture, and then bacteria were identified by morphological observation, Gram staining and PCR identification.In addition, serotype analysis, mixed infection analysis and drug sensitivity test were carried out on isolated Streptococcus suis (SS), Haemophilus parasuis (Hps), Pasteurella multocida (Pm), Bordetella bronchiseptica (Bb) and Actinobacillus pleuropneumoniae (APP).【Result】 The results showed that 647 strains of pathogenic bacteria were isolated and identified.The isolation rate of pathogenic bacteria was 29.35% (647/2 204), including 306 strains of SS (13.88%), 137 strains of Hps (6.22%), 86 strains of Pm (3.90%), 74 strains of Bb (3.35%) and 44 strains of APP (2.00%), respectively.The isolated SS, Hps and APP were chosen to do serotyping tests.The results showed that the major SS was serotype 2, the major Hps was serotype 5, 13 and 4, the major APP was serotype 1.The results of multiple infections showed that the single pathogen infected 407 pig farms, 214 strains of SS, 82 strains of Hps, 38 strains of Pm, 47 strains of Bb and 26 strains of APP were isolated.There were 70 double-mixed infected pig farms, mainly SS+Hps (22 pig farms) and SS+Pm (18 pig farms).There were 6 triple-mixed infected pig farms, mainly SS+Hps+Pm (2 pig farms) and SS+Hps+APP (2 pig farms).The results of drug sensitivity test showed that the isolated bacteria showed different degrees of resistance to 19 kinds of antimicrobial agents, and all the isolated bacteria were resistant to doxycycline and lincomycin, among which Bb showed severe multiple resistance.【Conclusion】 A total of 647 strains of porcine respiratory bacteria pathogens were isolated.SS was mainly serotype 2, Hps was mainly serotype 5, 13 and 4, and APP was mainly serotype 1.The type of multiple infections among different pathogens was complicated, and SS+Hps was the most common type of mixed infection.In this study, different pathogenic bacteria showed different degrees of resistance to 19 kinds of antibiotics.These data could provide a foundation for monitoring epidemiological patterns of bacterial diseases in large-scale pig farms in China, as well as provide reference basis for prevention and control.

Key words: porcine respiratory disease complex (PRDC); serotypes; multiple infection; drug sensitivity test

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