Porcine astrovirus type 4 (PoAstV4) is a respiratory pathogen that causes a cough in late farrowing and nursery phases, along with tracheal lesions upon necropsy. Because there is limited knowledge on how this pathogen is related to clinical signs associated with the virus in pigs during farrowing and nursery production, Emma Zwart set out to learn more.
Zwart, a student in the Iowa State University College of Veterinary Medicine, conducted this research as part of her experience in the Iowa State University’s SVIP (Swine Veterinary Internship Program) where she was hosted by Swine Vet Center and sponsored by Merck Animal Health.
“Increasing knowledge of sampling strategies allows for enhanced detection of disease, assessment of PAstV4 prevalence in the population, and may improve therapeutic interventions and control of disease,” she says.
She presented the findings of her study that looked at clinical signs of this virus and what sampling techniques may be best for detection and surveillance of this virus at the American Association of Swine Veterinarians annual meeting in San Francisco.
What’s the Best Sampling Method?
Zwart enrolled 36 litters in a sow farm that had recently tested positive for PoAstV4 and had a cough in late farrowing and early nursery. She followed the same group of pigs that were identified in the sow farm to the nursery, which was a total of 8 pens in the nursery. In the sow farm, she sampled each litter three times (4, 11 and 18 days of age) with udder wipes, family oral fluids and nasal swabs of five piglets per litter.
“In the nursery, I sampled each pen 4 times (28, 35, 42 and 49 days of age) with oral fluids and nasal swabs of 10 pigs per pen,” she explains. “Additionally, I compared a cough score based on the room to assess any clinical signs.”
She was able to detect the virus in both the sow farm and nursery with all sample types, but some sample types were better able to detect the virus than others.
“Porcine astrovirus type 4 was best detected by sampling with either udder wipes or family oral fluids in the sow farm, and oral fluids best detected the virus in the nursery,” Zwart says. “This research will be able to help producers who may have a cough in the late farrowing to early nursery phase with sampling techniques and selection for detecting porcine astrovirus type 4.”
This study was limited to studying only one farm, in which PAstV4 prevalence and infection dynamics may differ across farms, she adds. Further research of additional farms during various times of the year should be conducted to validate the findings of this study for differences in prevalence, clinical signs and seasonality.
“Additional research would provide insight into how sampling strategies can improve the early detection and control measures of PAstV4,” she says. “Research should be conducted to assess the isolation success rate using a sampling method to aid in possible vaccination development.”
Zwart was one of 15 students who competed in the oral presentation contest at the AASV annual meeting. Read more here.
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