Porcine reproductive and respiratory syndrome (PRRS) is one of the most economically important diseases of swine, with losses due to poor reproductive performance and high piglet and growing pig mortality. Transmission of porcine reproductive and respiratory syndrome virus (PRRSV) may occur by both direct and indirect routes; the latter includes exposure to PRRSV-contaminated fomites, aerosols, and arthropod vectors. This review has collected available data on the ex-vivo environmental stability and persistence of PRRSV in an effort to highlight important sources of the virus and to determine the role of environmental conditions on the stability of the virus, especially temperature. The ex-vivo settings include fomites (solid, porous, and liquid fomites), insects, people, and pork meat, as well as the role of environmental conditions on the stability of the virus, especially temperature.

Porcine reproductive and respiratory syndrome virus (PRRSV) causes significant economic losses in the global swine industry, partly because current vaccination strategies offer limited protection against heterologous viral strains. Since modified medium-chain fatty acids (mMCFA) offer enhanced structural stability and antimicrobial properties compared with unmodified MCFA, we evaluated a proprietary mMCFA blend (D-Strike, Devenish Nutrition) against PRRSV in vitro and in vivo. In vitro efficacy was assessed using TCID₅₀ assays on MARC-145 cells and a viability qPCR (V-qPCR). At 1:1000, 1:2000, and 1:5000 dilutions, the mMCFA inactivated >4 logs (99.99%) of the virus within 5 min of exposure. The results of V-qPCR were also compatible with those obtained by cell culture assays. For the in vivo study, 40 weaned male piglets were assigned to four dietary treatments: negative control (group A), PRRSV-challenge control (group B), 0.2% D-Strike (group C), and 0.4% D-Strike (group D). Pigs in groups B, C, and D were challenged intranasally with virulent PRRSV. The results demonstrated that dietary mMCFA reduced clinical signs, attenuated a febrile response, and decreased the severity of lung lesions. Some responses appeared more pronounced at the 0.4% inclusion level than at 0.2%, although a formal dose–response analysis was not statistically significant for most outcome measures. The sera from the 0.4% D-Strike group showed 65% lower PRRSV than the positive control, although this difference was not statistically significant. In addition, this group had 0% mortality as compared to 20% in the positive control group. Feed efficiency also improved in D-Strike-fed pigs. These findings indicate that mMCFA shows promise as a feed additive for mitigating PRRSV infection, although the in vivo antiviral effects require confirmation in larger studies.