Porcine reproductive and respiratory syndrome virus dissemination across pig production systems in the United States

Manuel Jara, David A. Rasmussen, Cesar A. Corzo, Gustavo Machado

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV) remains widespread in the North American pig population. Despite improvements in virus characterization, it is unclear whether PRRSV infections are a product of viral circulation within production systems (local) or across production systems (external). Here, we examined the local and external dissemination dynamics of PRRSV and the processes facilitating its spread in three production systems. Overall, PRRSV genetic diversity has declined since 2018, while phylodynamic results support frequent external transmission. We found that PRRSV dissemination predominantly occurred mostly through transmission between farms of different production companies for several months, especially from November until May, a timeframe already established as PRRSV season. Although local PRRSV dissemination occurred mainly through regular pig flow (from sow to nursery and then to finisher farms), an important flux of PRRSV dissemination also occurred in the opposite direction, from finisher to sow and nursery farms, highlighting the importance of downstream farms as sources of the virus. Our results also showed that farms with pig densities of 500 to 1,000 pig/km2 and farms located at a range within 0.5 km and 0.7 km from major roads were more likely to be infected by PRRSV, whereas farms at an elevation of 41 to 61 meters and surrounded by denser vegetation were less likely to be infected, indicating their role as dissemination barriers. In conclusion, our results demonstrate that external dissemination was intense, and reinforce the importance of farm proximity on PRRSV spread. Thus, consideration of farm location, geographic characteristics and animal densities across production systems may help to forecast PRRSV collateral dissemination.

Original languageEnglish (US)
Pages (from-to)667-683
Number of pages17
JournalTransboundary and Emerging Diseases
Volume68
Issue number2
Early online dateJul 13 2020
DOIs
StatePublished - Mar 2021

Bibliographical note

Funding Information:
We acknowledge the Department of Population Health and Pathobiology: North Carolina State University provided startup funds for Dr. Machado and CVM for the intramural grant which supported Dr. Jara. This work was also supported by Critical Agricultural Research and Extension 2019-68008-29910 from the USDA National Institute of Food and Agriculture and also by the USDA National Institute of Food and Agriculture, Animal Health project accession number 1021307. The Morrison Swine Health Monitoring Project is a Swine Health Information Center funded project. Authors would like to acknowledge participating systems and veterinarians.

Funding Information:
We acknowledge the Department of Population Health and Pathobiology: North Carolina State University provided startup funds for Dr. Machado and CVM for the intramural grant which supported Dr. Jara. This work was also supported by Critical Agricultural Research and Extension 2019‐68008‐29910 from the USDA National Institute of Food and Agriculture and also by the USDA National Institute of Food and Agriculture, Animal Health project accession number 1021307. The Morrison Swine Health Monitoring Project is a Swine Health Information Center funded project. Authors would like to acknowledge participating systems and veterinarians.

Publisher Copyright:
© 2020 Blackwell Verlag GmbH

Keywords

  • between-farm dissemination
  • molecular epidemiology
  • phylodynamics
  • virus dispersal

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