Swine veterinarians discover illness classes in COVID-19

When the sow farm managers failed to enforce COVID-19 safety precautions, their employees increasingly ignored these measures, said Dr. Larry Coleman.

Fellow pig vets told him their customers weren’t sure whether they were arranging masks among employees, for example, or needed social distance in break rooms. If they added such measures, compliance by employees depended on leadership in the establishments.

In a presentation on March 2 for the annual meeting of the American Association of Swine Veterinarians, Dr. Coleman, a pig practitioner in Broken Bow, Nebraska, said he had heard repeatedly from veterinarians about their customers’ difficulties in occupying sow farms during the pandemic. And he fears that the instances in which employees failed to comply with measures to protect them and their families could be a warning of future compliance with controls to prevent disease outbreaks in pigs.

“I shudder when I think about pig biosecurity measures because when we use fatigue, we end up losing,” he said.

Outbreaks challenged farms

By mid-March, the Institute of Agricultural Economics at Purdue University estimates that around 500,000 farm workers had developed COVID-19, including people who work in the animal and plant industries. In an article published in the Proceedings of the National Academy of Sciences in December 2020, authors from Columbia University and the University of Chicago estimated that livestock plants have been linked to 236,000 to 310,000 COVID-19 cases and 4,300 to 5,200 deaths .

Before the AASV meeting, Dr. Coleman approached 14 colleagues and in what he described as informal, asked what proportion of their customers had taken certain measures – such as putting on masks or adding hand sanitizing protocols – to protect workers from sowing farms from COVID-19. These vets shared with Dr. Coleman reported that 37% of their customer farms required face masks in the spring of 2020 and 19% in the summer and fall. Around 40% required physical distancing in break rooms in spring, 22% in autumn.

“All of the veterinarians interviewed reported difficulties getting employees to follow safety precautions at work and at home,” he said.

Between Dr. Coleman and his colleagues account for their customers covered by the informal survey, 30 pig production systems with 1.1 million sows, about one sixth of the US breeding herd.

Dr. Paul Yeske, veterinarian for the Swine Vet Center in St. Peter, Minnesota, and Dr. David Bomgaars, President and CEO of RC Family Farms, jointly described control efforts such as staggering shifts and breaks for workers, monitoring employee temperatures, cleaning office surfaces and increasing use of telemedicine.

“When we started hearing about problems across the country, we never imagined – especially in the first month – that slaughter capacity would soon be the biggest challenge many of our producers and veterinarians had ever faced.” Dr. Bomgaars said.

Outbreaks among slaughterhouses workers in the spring of 2020 resulted in operational shutdowns and slowdowns, safeguarding production systems with pigs waiting to be slaughtered. Thousands of pigs have been depopulated on the farms with no place to be found.

Lee Schulz, PhD, associate professor in the Department of Economics at Iowa State University, said the pig backlog peaked in late May or early June, affecting 1.5 to 2 million pigs. The pork industry reduced this backlog by early September.

Dr. Schulz said a report from the U.S. Department of Agriculture this spring could reveal the extent of the depopulation losses. This report was not available at the time of going to press.

Testing, understanding reduce transmission

Kim VanderWaal, PhD, assistant professor of population medicine at the University of Minnesota College of Veterinary Medicine, was working on a model that examined COVID-19 in three slaughterhouses. The results showed that the size of the outbreaks in individual plants was most dependent on the spread of the SARS-CoV-2 virus within the community and the transmission rates within the plant. Although plant managers have little control over infection rates in the community, they can influence transmission rates within the facility by adding physical barriers and implementing other practices to reduce contact.

When tests showed the extent of the infection, the workers changed their behavior and the infection rate decreased.

In her presentation at the AASV meeting, Dr. VanderWaal that in the three slaughterhouses examined in the studies, it could be expected that a typical worker who was infected at the beginning of the pandemic would spread the disease to two to four employees. However, this rate dropped rapidly as the plants put in place safety measures and workers followed infection prevention protocols. In addition, people who were already infected developed protective measures for the immune system.

Antibody tests added later also found far more workers were infected than reported by disease-related testing, although the gap in the one facility that offered internal COVID-19 testing was smaller. These results, according to Dr. VanderWaal, seem to illustrate the effects of asymptomatic transmission and differences in access to tests.

The model also found that running polymerase chain reaction-based tests on all workers every three days could reduce COVID-19 cases by 25% to 40%, while testing every seven days could reduce cases by about 20% and Tests done every two to four weeks were of little benefit.

Dr. Bomgaars also reported that he had worked with public health officials to expand COVID-19 testing among slaughterhouse workers. This helped to build confidence that they could go back to work.

“Plants that continued to harvest near capacity took quick steps to reduce the spread and show they were caring for the staff,” said Dr. Bomgaars.

The pandemic highlighted the importance of understanding people’s attitudes and behaviors, and finding effective ways to reduce the spread of disease. The same concepts apply to get producers to understand and apply effective livestock biosecurity measures to stop the spread of high-impact animal diseases.

Dr. Jack A. Shere, U.S. Department of Agriculture Assistant Administrator for Animal and Phytosanitary Inspection

The disease responses improve

Dr. Jack A. Shere, assistant administrator for the USDA Animal and Phytosanitary Inspection Service, said that containing disease in animals or humans requires a quick, coordinated response. The USDA has planned how to act in the event of an onset of African swine fever, a viral disease that has ravaged pig herds in Asia and Europe (see article).

In response to COVID-19 and the slowdown in pork production, Dr. Shere, members of several ARSP working groups have had discussions on how to find and depopulate marketing channels for pigs if necessary. National Veterinary Stockpile funding for new mobile depopulation and disposal equipment, he said, and federal COVID-19 aid funding helped some pig producers pay for depopulation and carcass disposal.

“The pandemic emphasized the importance of understanding people’s attitudes and behaviors and finding effective ways to reduce the spread of disease,” said Dr. Shere. “The same concepts apply to get producers to understand and apply effective livestock biosecurity measures to stop the spread of high-impact animal diseases.”

States are also making great strides in improving disease testing and adding laboratory equipment that could be used in an ASF or foot and mouth disease outbreak, said Dr. Shere.

“If we can proactively identify and address the remaining gaps, particularly in the areas of implementing biosecurity and validating protocols for mass depopulation and disposal, we can be better prepared for the next threat,” he said.

Dr. VanderWaal said protecting slaughterhouse workers in response to COVID-19 could help protect workers not only from the pandemic but also from seasonal colds and influenza.

“I think some of the additional practices and measures that have been put in place at these plants should help reduce the transmission of other respiratory diseases as well as promote a healthier workforce,” she said.

Dr. Coleman, who himself developed mild COVID-19 in early May 2020 after working closely with an infected employee on a pig farm, sees a need for leadership in responding to diseases on farms, regardless of whether they affect human or animal health. That leadership will determine whether employees see the disease as a threat, he said.

“It’s not so much about making rules, it’s about making sure the leadership gets the message home about what’s really a threat and what’s not – and then trying to control things that are really controllable,” he said.