By Kaitlyn St. Charles, Carol Cardona, Timothy Goldsmith, Cesar Corzo and Marie Culhane, University of Minnesota

In the United States, animal agriculture is having to make tough decisions about the quickly spreading and far-reaching diseases caused by H5 2.3.4.4b influenza A virus (USDA 2024). There have been substantial organized efforts to control H5 2.3.4.4b IAV in domestic poultry, because it is the cause of highly pathogenic avian influenza with severe illness and high death loss in infected flocks. So, it should be no surprise that efforts need to be made to control virus spread in other species, including humans. 

But what can we do when making decisions to effectively and swiftly control disease spread? We usually prepare in advance. With the current focus on H5 infections, yes, we need to be reactive and keep up H5 IAV surveillance and early detection efforts; however, we cannot afford to abandon our proactive efforts to understand and prepare for the threat of African swine fever because these efforts might help prepare for H5 IAV in pigs too. 

An ASF detection in a pig farm would result in immediate quarantine of the infected farm and the establishment of a Control Area. All farms in a Control Area and farms with epidemiological links to the infected farm would have pig/product movement stopped. Stop movement orders are a big deal for all production phases, particularly for live pigs, but also for semen movements from boar studs to breeding farms.

There are approximately 200 boar studs in the U.S., many of them located near high pig dense areas. Boar studs are kept separate from other swine premises, since geographically isolating boar studs is an effective biosecurity measure to prevent infectious disease spread (Reicks, 2019).  Despite separation, boar studs would likely be included in a Control Area, especially if they were epidemiologically linked via semen to a breeding farm. 

The number of semen movements from boar studs to breeding farms in the U.S. is substantial.  In the U.S., each boar stud houses a mean of 400 boars and a median of 176 boars (range 1-853). Those 176 boars have the reproductive capacity to produce enough semen to service 44,000 sows on a weekly basis. Therefore, efficient and timely movement of both pigs and semen are critical for producers; any disruption in flow severely limits the capacity to maintain animal health and welfare, continuity of business, and domestic markets. But the movements have to be done in a way to minimize risk of disease spread. 

Which brings us to the question—can you have scientifically informed policies that still allow movements from the disease control area when you are trying to eradicate the disease?

Since the goal of a disease eradication program is to eradicate the disease from the animal industry and not the animal industry itself, regulatory agencies would also institute continuity of business permitting in addition to the initial stop movement order. The aim of COB permitting is to enable pigs and pig products, like semen, to move safely out of a Control Area, with each permit requiring specific criteria producers must meet to minimize disease spread risk.

To determine permit criteria, proactive risk assessments involving public-private partnerships are conducted. The University of Minnesota (UMN UDC 2024) has been working under state, federal and industry agreements as public-private partnerships to perform epidemiological studies and conduct a RA that evaluated the risk of spreading ASF via moving boar semen from a Control Area. The RA was conducted using the import risk analysis framework established by the World Organization of Animal Health and in close collaboration with a workgroup consisting of swine genetics companies, animal health regulators, and academics throughout the RA process to produce results that can be readily implementable into U.S. policy.

Entry and exposure assessments were completed using disease pathway analysis and stochastic disease transmission modeling. The public-private workgroup was pivotal in 1) characterizing industry practices to determine disease entry/exposure pathways, 2) assessing feasibility of COB testing implementation and outbreak-specific mitigations, 3) providing data for quantitative models, and 4) evaluating the risk ratings’ acceptability.

The overall descriptive risk rating for boar semen movement from an ASF Control Area was “low” if all COB permit criteria are followed, which swine industry members and government agencies deemed as acceptable risk. Specific RA findings informed discussions and plans regarding the exclusion of semen movements from initial stop movement order and the biosecurity and testing proposals necessary to decrease risk of ASF spread by semen. Collaborative efforts of the public-private partnership allowed for rapid implementation of RA findings into US ASF plans (USDA 2023). 

Working together to assess the risk of spreading ASF via boar semen movements out of a Control Area is an example of effectively utilizing public-private partnerships in a proactive risk based scientific approach, and letting science inform the policies that have an impact on U.S. agriculture.

References

Reicks DL. Effective biosecurity to protect North American studs and clients from emerging infectious disease. Theriogenology. 2019;137:82-87.

University Digital Conservancy (UDC), University of Minnesota (UMN) Twin Cities, College of Veterinary Medicine, Proactive Risk Assessments. Accessed 08 May 2024,

USDA APHIS VS. Highly Pathogenic Avian Influenza (HPAI) Detections in Livestock. Accessed 07 May 2024.

USDA The Foreign Animal Disease Preparedness and Response Plan (FAD PReP)— African Swine Fever Response Plan: The Red Book (July 2023). Accesses 07 May 2024