Grad Student Competition
Naturally occurring antibody responses to H5N1 influenza A virus in non-lactating Holstein heifers.
| Date/Time: |
8/28/2026
09:15
|
| Author: |
Rebecca Dorn |
| Clinic: |
South Dakota State University PPVM 2+2 with the University of Minnesota |
| City, State, ZIP: |
Dell Rapids, SD 57022 |
Rebecca Dorn, BS
1
;
Christopher Chase, DVM, PhD
1
;
Corale Dorn, DVM
3
;
Scott Wells, DVM, PhD
4
;
Steve Lawson, PhD
2
;
Eric Nelson, PhD
2
;
Guillermo Castillo, DVM, PhD
5
;
1Professional Program in Veterinary Medicine, South Dakota State University, Brookings SD, 57007
2Animal Disease Research and Diagnostic Laboratory, South Dakota State University, Brookings SD, 57007
3Dells Veterinary Services, Dell Rapids SD, 57022
4College of Veterinary Medicine, University of Minnesota, St. Paul MN, 55108
5Center for Animal Health and Food Safety, University of Minnesota, St. Paul MN, 55108
Introduction:
Since the diagnosis of H5N1 influenza A virus in lactating dairy cows in March 2024, research has focused on lactating dairy cows that show the obvious clinical signs of infection. However, research is lagging to evaluate infection in dairy replacement heifers born around the time of outbreaks in the lactating herd. The objective of this study was to evaluate naturally occurring antibody responses to H5N1 influenza A virus in dairy replacement heifers detected months after the outbreak to evaluate if exposure in utero or post-partum to lactating cows and pasteurized pooled colostrum created detectable serologic responses in non-lactating replacement heifers.
Materials and methods:
The initial diagnosis of H5N1 influenza A virus was confirmed with a PCR test performed from a bulk tank sample on June 7, 2024. For this study, dairy heifers were selected from three different age groups, with approximately 50 animals in each group. Group 1 consisted of heifers born between November 2023 to March 2024 and were moved off site, by May 4, 2024. Group 2 consisted of heifers born in June 2024 to clinically affected dams. These heifers were located at the dairy during the outbreak. Group 3 consisted of heifers born in October 2024 from cows that were clinically affected in June 2024 and less than 125 days of gestation when the dam was clinically ill. The test used to evaluate the antibodies in the heifers was ID Screen Influenza H5 Antibody Competition 3.0 Multi-species test. Serum samples with positive cELISA results and a subset of serum samples with negative cELISA results were challenged with a serum virus neutralization assay with a genotype of B3.13.
Results:
Of the three different cohorts studied, Group 1 was the only group that showed significant serum antibodies to H5 20 months after the outbreak. 90% (9/10) of the confirmed positive and suspect positive heifers were born within 10 days of each other, from February 25 to March 5, 2024. At 20 months post outbreak, 12% of Group 1 were still seropositive or suspect seropositive. One out of 51 heifers in Group 2 were seropositive 15 months after the outbreak. The date of birth of the test-positive heifer was June 2, 2024. Group 3 showed no serum antibodies to H5 20 months after the outbreak. The vast majority (73%) of cELISA-positive heifers showed evidence of virus neutralizing antibody ability, a measure indicating likelihood of protection against future infection.
Significance:
Of the three different dairy heifer cohorts evaluated, heifers born on the dairy 3-6 months and moved offsite a month before outbreak detection and confirmation was the only group with significant serum antibodies to H5 influenza A virus at a time point over 20 months after the outbreak was confirmed. While the time and route of exposure to the virus cannot be definitively confirmed, it is noteworthy that this group of heifers were born within 10 days of each other and not in contact with reported clinically ill cows, their milk, or their colostrum following the confirmation date of the dairy herd’s outbreak. Further, given the lack of serum antibodies in replacement heifers born during and after an outbreak, it is reasonable to consider this population may be at risk of infection if viral exposure would occur in the future.
