TYPE Editorial PUBLISHED 29 November 2023 DOI 10.3389/fvets.2023.1329073 Editorial: Porcine respiratory OPEN ACCESS disease complex: dynamics of polymicrobial infections, EDITED AND REVIEWED BY Michael Kogut, United States Department of Agriculture, United States *CORRESPONDENCE synergistic effects and Natalia Ramos nramos@fcien.edu.uy management strategies RECEIVED 27 October 2023 ACCEPTED 10 November 2023 PUBLISHED 29 November 2023 Natalia Ramos1*, Marina Sibila2,3,4 and Victor Neira5 CITATION 1 Ramos N, Sibila M and Neira V (2023) Editorial: Sección Virología, Instituto de Biología, Facultad de Ciencias, Universidad de la República, Montevideo, Porcine respiratory disease complex: dynamics Uruguay, 2 IRTA, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la UAB, Cerdanyola of polymicrobial infections, synergistic effects del Vallès, Spain, 3 Unitat Mixta d’Investigació IRTA-UAB en Sanitat Animal, Centre de Recerca en Sanitat and management strategies. Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), Cerdanyola del Vallès, Spain, 4 Front. Vet. Sci. 10:1329073. WOAH Collaborating Centre for the Research and Control of Emerging and Re-Emerging Swine doi: 10.3389/fvets.2023.1329073 Diseases in Europe (IRTA-CReSA), Bellaterra, Barcelona, Spain, 5 Departamento de Medicina Preventiva Animal, Facultad de Ciencias Veterinarias y Pecuarias, Universidad de Chile, Santiago, Chile COPYRIGHT © 2023 Ramos, Sibila and Neira. This is an open-access article distributed under the terms KEYWORDS of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction porcine respiratory disease complex, polymicrobial infections, infection interaction in other forums is permitted, provided the dynamics, patterns of co-infection and superinfection, management strategies original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Editorial on the Research Topic Porcine respiratory disease complex: dynamics of polymicrobial infections, synergistic effects and management strategies Porcine respiratory disease complex (PRDC) is a major cause of production losses in the global swine industry. The disease is often multifactorial and polymicrobial, resulting from infection with different combinations of pathogens (including viruses, bacteria, and parasites), in addition to non-infectious factors such as environmental conditions, animal age, population size, management strategies and genetics. Given the complex nature of PRDC and the lack of comprehensive research on the subject, the objectives of this Research Topic were to provide insights into pathogen detection in swine respiratory disease, to identify patterns of co-infection, superinfection and opportunistic pathogens, and to establish monitoring methods and preventive measures. The first study that contributed to the aim of this Research Topic focused on the identification of several pathogens in swine with typical clinical respiratory signs from farms in China, one of the leading pork producing countries (Sun et al.). The authors analyzed 1,307 samples from 269 farms in 17 provinces, screening for the most important viral and bacterial pathogens. Viruses such as porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV-2), and pseudorabies virus (PRV) were detected in tissue samples (lungs, inguinal lymph nodes and tonsils) by PCR. In addition, five common respiratory bacteria [Streptococcus suis, Glaesserella (Haemophilus) parasuis, Pasteurella multocida, Actinobacillus pleuropneumoniae, and Bordetella bronchiseptica] were isolated and identified from nasal swabs, trachea, lung, spleen, brain, and joint fluid samples. The results indicated that PRRSV, PCV2, S. suis and G. parasuis were the most commonly detected pathogens in pigs with PRDC in China. Furthermore, the findings unveiled that co-infections of two or more PRDC-associated pathogens with strong positive Frontiers in Veterinary Science 01 frontiersin.org Ramos et al. 10.3389/fvets.2023.1329073 correlations were common in China. These included double viral load and M. hyopneumoniae laryngeal load, while mitigating infections like PRRSV and G. parasuis, PRRSV and P. multocida, pulmonary and lymphoid lesions. PCV-2 and P. multocida, and also triple infections such as PRRSV- Finally, a review of the dynamics of polymicrobial PCV-2 and G. parasuis and PRRSV-PCV-2 and P. multocida. This infections in PRDCs and related management strategies was study also highlighted the identification of certain pathogens in a valuable contribution to this Research Topic (Assavacheep relation to the age of the animals; for example, PRRSV, PCV2, and Thanawongnuwech). The authors emphasized that new and G. parasuis exhibited the highest detection rates in nursery management strategies have been proposed following the pigs, while P. multocida and A. pleuropneumoniae had the highest introduction of African swine fever (ASF), particularly in Asian detection rates in fattening pigs. countries, and some of these may inadvertently lead to the Another article published in the present topic was centered re-emergence of existing endemic PRDC pathogens, like PRRSV on the identification of viral pathogens in nasal swab from 55 and PCV-2. However, the strict biosecurity measures required cases of respiratory disease outbreaks under the suspicion of swine during the ASF era, such as minimizing pig contact through the influenza A virus (swIAV) in nurseries from Spain and Portugal use of automated feeding systems, artificial intelligence and robotic (Martín-Valls et al.). Notably, the authors conducted screenings farming, may also help to eliminate PRDC from farms. for a wide array of respiratory viruses, including: swIAV, PCV-2, These studies collectively illustrate the diverse array of PRRSV, influenza B (IBV) and D (IDV), swine orthopneumovirus pathogens identifiable in swine respiratory disease and the (SOV), porcine parainfluenza 1 virus (PPIV1), porcine circovirus intricate dynamics of their interactions. More comprehensive 3 and 4 (PCV-3, PCV-4), porcine respiratory coronavirus (PRCV), studies monitoring a wide range of pathogens, both viral and and porcine cytomegalovirus (PCMV). The results indicated that bacterial, are increasingly needed to gain a better understanding PCV-3, PRRSV and PCMV were the most commonly detected of PRDC. In addition, consistency in sample selection and viruses at the herd level (in more than 70% of cases analyzed). analysis of different age groups would be essential to allow more However, IBV, IDV, PCV-4, and PPIV1 were not detected in any accurate comparisons between studies. Definitely, more research case. The study delved deeper into the interaction between different in this area will allow better prevention and control strategies to viral pathogens, identifying thirty-one combination patterns, which be developed. suggested a complex etiology of respiratory disease in pigs. Furthermore, the authors demonstrated that the frequency of a specific pathogen detected in swIAV-positive cases at herd level Author contributions differed from that in swIAV-negative cases. Interestingly, PRCV, SOV and PCMV were more likely to be found in swIAV-positive NR: Writing—original draft, Writing—review & editing. MS: herds. On the other hand, PRRSV exhibited a negative correlation Writing—review & editing. VN: Writing—review & editing. with swIAV and PRCV, but a positive correlation with PCMV. Another noteworthy finding from this work was the identification of the circulation of PRCV, PCMV, SOV and PCV-3 initiated in the Funding 1st weeks of life, indicating a significant role for sows. The author(s) declare that no financial support was received for The third article of this Research Topic was focused on the the research, authorship, and/or publication of this article. detection of PRRSV, one of the most commonly detected viruses in respiratory disease (Osemeke et al.). In this work, the use of oral swabs for PRRSV detection by RT-rtPCR was analyzed and Conflict of interest compared it to serum samples from weaning-age pig litters. The results revealed that while oral swabs represent easy-to-collect and The authors declare that the research was conducted in the non-invasive individual sample, they are less sensitive alternative absence of any commercial or financial relationships that could be for PRRSV surveillance when compared to the serum samples, construed as a potential conflict of interest. which serve as reference. In the context of PRDC control, this Research Topic also included an article on the comparative evaluation of two bivalent Publisher’s note vaccines containing PCV-2 and Mycoplasma hyopneumoniae (Cho et al.), a widely used strategy for preventing clinical respiratory All claims expressed in this article are solely those of the signs on pig farms. One vaccine contained PCV-2a and the other authors and do not necessarily represent those of their affiliated contained PCV-2b. The results obtained showed that both bivalent organizations, or those of the publisher, the editors and the vaccines were viable options for controlling subclinical PCV-2d reviewers. Any product that may be evaluated in this article, or infection and enzootic pneumonia swine farms. Additionally, both claim that may be made by its manufacturer, is not guaranteed or vaccines induced protective immunity by reducing PCV2 blood endorsed by the publisher. Frontiers in Veterinary Science 02 frontiersin.org