Porcine epidemic diarrhea virus, or PEDV, is a fairly new and serious disease that affects pigs and is frequently deadly in piglets. At this point, it is unknown how a virus enters the herd but Dr. Grant Allison from Iowa indicated he was concerned that flies could transmit it as they replicate in moist conditions that could involve manure. Flies were examined and were positive for PEDV on a PCR test, but that does not mean the virus on the flies is alive but only that it is present. So, you have to show that a positive fly can carry contagious virus and that requires a bioassay as that shows transmission of the virus to live pigs that don’t have the disease.
In the case of porcine epidemic diarrhea virus, the bioassay was positive, indicating flies can transmit the disease. Flies are historically a seasonal problem but infected flies are being found in Iowa in the winter and certainly we have flies in Texas in the winter. Because of this risk, it is developing a year-round pest management program is recommended. Dr. Allison indicates the two options are using a fogger or mister, or use a feed through fly control product which is recommended to decrease exposure of humans to the products in the foggers and misters (this type of product kills the fly larvae in the manure). There are certainly other possible methods of viral transmission, such as feed ingredients, but these are difficult to test before feeding them. Although the feed and trucks that carry the feed are a potential source, the pigs have to eat and trucks must bring the feed. However, fly control can be accomplished at every swine operation and should be a year-round program to decrease transmission of porcine epidemic diarrhea virus. Check with your swine veterinarian for the best method of fly control for your operation or call an agricultural school’s extension veterinarian.