Pork virus on the decline, but favorable weather for disease looms
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WASHINGTON, Sept. 3, 2014 - The disease that has plagued the U.S. pork industry for the last 17 months has slowed its progression, but producers are gearing up for a potential uptick in the winter months.
Porcine Epidemic Diarrhea virus (PEDv), first detected in the U.S. in April 2013, has since spread to 30 states with more than 8,000 positive accessions. Exact numbers of infected hogs are difficult to determine because a positive accession equates to an affected farm, but USDA estimates the June 1 inventory of hogs and pigs was down about 5 percent from a year earlier, at 62.1 million animals.
Steve Meyer, president of Paragon Economics in Adel, Iowa, and a consulting economist for the National Pork Producers Council (NPPC) estimates the disease, which does not affect humans or pork quality, has killed between 8 million and 9 million pigs. He also noted that hog slaughter plants are currently operating at about 81 percent capacity nationwide - a number Meyer called “awfully low” -- at a time when production is usually ramping up.
The highly contagious disease spread quickly after the initial detection but the progression slowed this summer. According to NPPC Chief Veterinarian Liz Wagstrom, that's because the virus prefers lower temperatures provided by the fall, winter, and spring. Last summer, low producer awareness - the disease had never before appeared in North America - contributed to its spread, so lack of steps in biosecurity, steps that producers have now implemented, made up for the unfavorable temperatures for the disease.
“We've learned a lot in the last year, so we're hoping that (producers) will continue to be able to implement what we have learned over the last year and put it into practice,” Wagstrom said in an interview with Agri-Pulse. The biosecurity measures including taking extra steps to clean and disinfect farm equipment and trucks that move pigs to processing plants.
Unfortunately, fall and winter will bring more favorable weather for the spread of the disease. As the industry continues to learn more about the virus, favorable weather for transmission may just be part of the looming problem in the coming months.
It's widely known that PEDv can travel on something such as a shovel, an infected feedstuff, or anything else that comes in direct contact with an infected pig. Now, a recent study published in Veterinary Research found the disease has the potential for airborne transmission, in some cases reaching as far as 10 miles downwind.
Wagstrom said she is aware of studies to determine if the disease can travel on dirt and dust, but is hesitant to give full credence to the theory of airborne transmission.
“If you have enough infected virus on dust particles that could then be either snuffed up or licked up or whatever, there's the potential for those dust particles to have enough infected virus that they could potentially spread the disease,” Wagstrom said. “It's kind of a fine line between airborne transmission and virus being on dust particles that may potentially infect the animal.”
In June, USDA's Animal and Plant Health Inspection Service (APHIS) issued a conditional license to Harrisvaccines Inc. of Ames, Iowa, for a PEDv vaccine. Harrisvaccines was honored for the product at the 2014 World Pork Expo, and sold about 2 million doses via veterinary prescription before the conditional license allowed the company to sell directly to veterinarians and producers. The vaccine is designed to be given to sows so that they will build up antibodies that can be transferred to piglets via suckling.
However, Wagstrom said vaccinating the piglets might not be successful because the nature of PEDv causes the disease to reside in the gut of the pig, not the blood stream.
“It might be a little different for a respiratory disease, but for a disease that's focused on the gut, you're probably not going to have much immunity that lasts after the pig stops nursing,” Wagstrom said. “Because PED lives and attacks in the intestine, the immunity has to be based in the immune cells that line the gut, and you just don't get that . . . from just plain vaccination.”
While it is still unknown how the disease got to the U.S. - Wagstrom said it most closely resembles a virus seen in China - researchers have been swift in educating producers. Grants were made available to land grant researchers, who provided periodic updates on research and eventually published findings on the Pork Checkoff website.
Wagstrom said she hopes that with improvements in biosecurity, producer education, and the possibility of immunities built up in the herd will result in the coming winter months not taking the toll on the hog and pig inventory that was observed last winter.
“We're really out there trying to make sure that producers don't forget to keep their extra caution and extra protocols to try to prevent any introduction,” Wagstrom said.
Since most fatalities due to the virus are among piglets, the long-term damage to the herd may not be as bad as originally thought. There will be some losses in replacement gilts, but Meyer said the industry could quickly rebound from the disease.
“It will have some long-term impact in the fact that we don't have enough replacement gilts out there to grow the sow herd and those kinds of things, but you could solve the lion's share of the production impact (quickly) if you solved the disease tomorrow,” Meyer said.
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