Weathering the storm: Extreme weather events and their association with PED and PRRS occurrence.

Porcine epidemic diarrhea (PED) and Porcine reproductive and respiratory syndrome (PRRS) are viral diseases that continue to challenge the US swine industry. Despite many known risk factors, unusual circumstances associated with their occurrence continues to be poorly explained. We investigated if extreme weather events (flood, heavy rain, high wind and tornadoes, measured at a county-level) are associated with the occurrence of both diseases up to ten weeks after the occurrence of the weather event using a case control study and logistic regression modeling to control for covariates. We obtained weekly farm-level disease occurrence information from the Morrison Swine Health Monitoring Project (MSHMP) and county-level weather events occurrence information from the National Oceanic and Atmospheric Administration (NOAA) storm events database. Our findings indicate that farms in counties exposed to floods had between two to three times higher odds of experiencing a PED outbreak between four to eight weeks after the event than control farms. However, we did not observe significant associations between other weather events and PED or PRRS occurrences. Even though the absolute risk these events pose to swine herds may be small, we suggest that companies should develop biosecurity protocols that consider the impact of extreme weather events in order to mitigate the risks posed to their herds.