A one-night downtime period prevents the spread of porcine reproductive and respiratory syndrome virus and <i>Mycoplasma hyopneumoniae</i> by personnel and fomites (boots and coveralls)

The practice of restricting personnel entry to swine farms for extended periods of time following contact with other pigs (downtime) is a highly controversial subject throughout the global swine industry. For many years, downtime periods ranging from 48 to 96 hours have been enforced to reduce the risk of pathogen introduction to farms by personnel, despite a lack of data supporting these periods of time. In the literature, Sellers et al1 investigated the ability of people to harbor foot-andmouth disease virus following exposure to infected swine. Results indicated the presence of one positive nasal swab from one person 28 hours post exposure, but not at 48 hours post exposure; however, attempts to replicate these results have not been successful.2 Likewise, Amass et al3 reported the recovery of porcine reproductive and respiratory syndrome virus (PRRSV) RNA from fingernail rinses and nasal swabs 5 and 24 hours, respectively, following contact with infected pigs; however, the viability of PRRSV in these samples was not confirmed and transmission to naive sentinels was not observed. Finally, Otake et al4 recovered infectious PRRSV from the hands, boots, and coveralls of personnel following contact with infected animals and demonstrated transmission to naive sentinels. However, this study also demonstrated that basic sanitary interventions such as showering and changing clothing and footwear could prevent mechanical spread of PRRSV, irrespective of downtime.4 Collectively, these data challenge the value of extended downtime periods; therefore, to better understand this risk, we summarized observations regarding the ability of a 1-night downtime period to prevent the mechanical spread of PRRSV and Mycoplasma hyopneumoniae (M hyo) from infected to susceptible populations by personnel and fomites.