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THE LAND — FEBRUARY 5/FEBRUARY 12, 2021
University of Minnesota’s swine influenza research continues
SWINE &U
Winter has arrived and we have seasonal disease concerns — both in the pig barn and with the caretakers. UniversityofMinnesota For the past year we have EXTENSION been immersed in learning all we can about Covid-19, but sows; growing pigs will the usual winter worries on experience severe respirathe pig farm always include tory distress for 7-10 days, swine influenza virus. Swine then return to normal influenza virus can be simply over the next 7-10 days. referred to as the flu, but In the Midwest, 90 perthere’s nothing simple about cent of swine herds conit in the herd. SWINE & U taining growing pigs have Prior to this 2020 season of tested positive for SIV. By Diane DeWitte Covid-19, the 2009 H1N1 While commercial vac(“swine flu”) pandemic was the worst human flu attack since 1918. Because cines exist for swine influenza, many its origins were a reassortment of herds prefer to use an autogenous vachuman, bird and swine flu viruses, cine created specifically for them. much research has occurred in the These custom-made vaccines are forensuing years to better understand flu mulated by using herd-specific antigens from the influenza-infected popuin pigs and people. lation. Influenza in Pigs Swine influenza virus is present in Recent studies on influenza The past seven years have found the most swine herds across the country, and it appears to be a disease many University of Minnesota on the forefarms constantly live with. It’s a respi- front in conducting valuable applied ratory disease which affects all stages research to try to understand influenza of production. Suckling piglets gener- in swine, its control, and how it can be ally have immunity to the disease eradicated. while with the sow. Coughing, pneumoDr. Fabian Chamba Pardo recently nia and fever are the most common published findings of his study of the symptoms. The high temperatures of factors which affect influenza infection SIV can cause abortions in pregnant status of piglets at weaning time. From
University of Minnesota Extension Swine Resources for you Website: extension.umn.edu/swine Swine Extension blog & Newsletter: https://blog-swine.extension.umn.edu Minnesota’s Swine & U Podcasts: https://z.umn.edu/UMNSwineExtensionPodcast UM Extension Swine YouTube channel: https://z.umn.edu/UMNSwineYouTube UM Extension Swine Facebook page: facebook.com/UMNSwine UM College of Veterinary Medicine Swine blog: www.umnswinenews.com Contact the University of Minnesota Extension Swine Educators: Sarah Schieck-Boelke at schi0466@umn.edu Diane DeWitte at stouf002@umn.edu
A common practice on pig farms is to use nurse sows to adopt piglets who fall behind and might otherwise d i e. Transmission of influenza virus from nurse sows to adopted pigs has been reported experimentally. However, until now, studies in actual production farms have not been conducted. The study included a total of 184 sows in three breeding herds in Minnesota and Iowa. All three herds were positive for the swine influenza virus. The researchers collected oral swabs and udder wipes from the sows before the adopted pigs were placed with them, and after weaning. Oral swabs were collected from six piglets in each litter three times during the nursing period and at weaning. Overall, this study showed more sows were found positive at weaning compared to the beginning of the study when using oral swabs. However, no difference was found between the nurse sows and control sows. When looking at udder wipe samples, a higher proportion tested positive in the nurse group compared to the control group at the onset of the study. This difference was not found at the time of weaning. The udder wipe samples also tested positive by virus isolation, showing that nurse sows could serve as a mechanical means of transmission in addition to direct transmission from their own oro-nasal secretions. This study indicates that nurse sows can contribute to the transmission and perpetuation of influenza infections in pigs prior to weaning, particularly during the first week after adoption. (Report from umnswinenews.com, Jan. 26.) Protect people and pigs Although influenza is not a federally reportable or regulated swine disease, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service in conjunction with the American Association of Swine Veterinarians and National Pork Board have collaborated on the establishment of a national swine influenza virus surveillance program. Veterinarians can submit nasal fluid, oral swabs or lung tissue to a local lab to be evaluated. In Minnesota, the University of Minnesota
2011 to 2017, Pardo collected samples at weaning on 83 swine farms in Iowa, Minnesota and South Dakota. These monthly samples were part of a routine surveillance program and yielded these results: Piglets who were raised by sows vaccinated against influenza were less likely to have the disease. Gilts who entered the sow herd and were influenza-positive were associated with positive piglets at weaning. Further details of Dr. Pardo’s study can be found at https://z.umn.edu/ PardoInfluenzaStudy. A robust five-year study of 34 breedto-wean farms by the team at the University of Minnesota’s Veterinary Population Department undertook the three-pronged challenge of estimating the prevalence and seasonality of SIV, investigating the correlation between the prevalence of SIV and weather, and studying the genetic diversity of the SIV on the farms over time. The team found that the prevalence of influenza in herds over five years ranged from 7 percent to 57 percent with a median presence of 28 percent. Herd-level influenza occurrences followed a cyclical pattern with levels increasing during the fall, peaking in December and May, and subsiding in the summer. Researchers were able to correlate the prevalence of herd-level influenza with lower outdoor temperatures and low absolute humidity. The team’s research also showed that over time, there were genetically diverse influenza viruses co-circulating within the herd. (Frontiers in Veterinary Science, October 2017). 2020 influenza research A study by the University of Minnesota Veterinary College’s Torremorell group was recently published in the Preventive Veterinary Medicine Journal. In this publication, Dr. Jorge Garrido-Mantilla et al. evaluated if piglets put together with a nurse sow were more likely to be influenza A (SIA) positive; and conversely, if a nurse sow could become infected when adopting a litter of positive piglets. See SWINE & U, pg. 11
