Virus management Long-living virus poses unique challenges for swine researchers and producers
A vaccine developed to fight porcine epidemic diarrhea is ineffective in protecting piglets, says a swine veterinarian.
Dr. Egan Brockhoff of Prairie Swine Health Services told a Feb. 19 meeting of hog producers in Lethbridge that a vaccine developed in the United States by Harrisvaccines may reduce viral shedding but will not keep the disease out of herds.
“Vaccine technology has improved a lot in the last 10 years, but this morning, we’re waking up with no effective vaccine against PED and we will wake up tomorrow with no effective vaccine,” Brockhoff said.
He said the vaccine developer, well-known hog disease specialist Dr. Hank Harris, has told him that at least 800,000 doses of vaccine have been distributed to U.S. hog producers. They have failed to limit the spread of PED in the U.S., where it has infected more than 3,000 hog operations in 24 states and killed millions of piglets.
PED spreads primarily through fecal-oral contact. It destroys the inner lining of piglets’ intestines, making them incapable of digesting and deriving nutrition from their milk and feed. The virus causes diarrhea, vomiting and death from severe dehydration and starvation.
Brockhoff said an enteric oral virus likely needs an enteric oral vaccine to fight it, and no such vaccine exists.
He said he has worked with vaccines in Asia, where PED has been evident since the early 1980s, and those vaccines are not effective either.
Brockhoff said Harrisvaccines has developed two versions of the vaccine and is working on a third.
Producers asked whether measures taken against transmissible gastroenteritis (TGE) might work against PED. Like PED, TGE is an intestinal disease caused by a coronavirus.
However, Brockhoff dispelled the notion.
“PED is slightly different than TGE. TGE, if we close a herd, heavily wash and disinfect the barn, we can walk TGE out, with closure. TGE doesn’t survive near as long in the environment. It doesn’t affect the gut near as long as PED.”
Joel Harris, sales and marketing head for the Iowa-based Harrisvaccines, said earlier this month the company was hopeful that its vaccine would induce an antibody response in older animals.
“The predominant use has been in previously exposed systems or chronically exposed systems,” he said of vaccine application in the U.S.
The Canadian Food Inspection Agency announced earlier this month that it would issue emergency use permits for the vaccine so it could be used in Canadian operations.
CFIA chief veterinary officer Dr. Harpreet Kochhar said “a couple” of import certificates had been issued, but he didn’t know of any Canadian producers who had used it.
PED is fatal to piglets, but older pigs can develop immunity.
Producers who already have the virus in their barns are encouraged to develop a systematic method of exposing all sows, gilts and boars to the virus so that immunity develops.
For those free of PED, strict biosecurity is required to keep the virus out.