2026 ISU McKean Swine Disease Conference

ISU McKean Swine Disease Conference

doi:10.31274/swinedisease.25833

2026 Proceedings booklet

Gateway Hotel and Iowa State University College of Veterinary Medicine

Conference Center Iowa Pork Industry Center

Ames, Iowa American Association of Swine Veterinarians, District 6

Science with Practice Award

The Science with Practice Award is given in recognition of exemplary integration of the science and the art of veterinary practice to benefit swine productivity and welfare. The award is given annually and is based on the following criteria.

A person who routinely examines pigs and makes recommendations to swine producers regarding pig health and well-being.
A person who integrates current knowledge and scientific understanding into everyday applications.
A person who pursues continuous improvement in knowledge and practices based on scientific methods applied to innovation or field research.
A person who supports current and future swine practitioners through sharing of time, talent, information and expertise.

Recipients

2025 Dr. Patrick Halbur

2019 Drs. Brad and Eileen Thacker

2014 Dr. Steve Henry

Ames, Iowa

Bethesda, Maryland

Abilene, Kansas

2024 Dr. Paul Armbrecht

2018 Dr. David Schmitt

2012 Dr. Hans Rotto

Rockwell City, Iowa

Stuart, Iowa

Ames, Iowa

2023 Dr. Paul Sundberg

2017 Dr. Darwin Reicks

2011 Dr. Howard Hill

Ames, Iowa

St. Peters, Minnesota

Cambridge, Iowa

2022 Dr. Kent Schwartz

2016 Dr. Jeremy Pittman

2010 Dr. Daryl Olsen

Ames, Iowa

Waverly, Virginia

Audubon, Iowa

2021 Dr. Butch Baker

2015 Dr. Mark FitzSimmons

2009 Dr. Craig Rowles

Eddyville, Kentucky

Mapleton, Minnesota

Carroll, Iowa

2020 Dr. Tara Donovan

2008 Dr. Mark Engle

Spring Green, Wisconsin

Hendersonville, Tennessee

The VDPAM Graduate Program recognizes outstanding progress from graduate students by providing the Roy Schultz Graduate Student awards

Elevating the profile of Graduate Students

Roy Schultz Graduate Student Excellence award. $2,500. The eligibility criteria includes: Graduate student status at any University; selected abstract for oral presentation at the ISU Swine Disease Conference; field-applicable research assisting veterinarians making decisions on swine health & productivity; work submitted to peer-review scientific journal. Practitioner’s input would be ‘heavily weighted’ in the selection process.

Roy Schultz Graduate Student Scholarship award. $4,000. The eligibility criteria includes: Graduate students enrolled in the VDPAM graduate program, have had the plan of study & committee established at least 1.5 years ahead of target defense data, GPA ≥ 3.5, have submitted at least one grant proposal, and published at least 1 peer-reviewed manuscript and one proceedings paper at a national or international conference. The rubric will take into account evidence of grantsmanship and scholarship in their CV: number of papers, presentations, proceedings, grants, extension & outreach material.

Travel awards to graduate students presenting orally at a National or International Conference: cost-reimbursable, value up to $1.5K per year split into three $500 awards.

Elevating the profile of the VDPAM Graduate program

VDPAM Graduate Program Marketing award. $2,000. ISU-wide award for staff, undergraduate, professional, or graduate students working on a marketing plan to elevate the profile of the VDPAM Graduate Program, targeting attracting qualified prospective domestic or international students.

Recipients

Roy Schultz Graduate Student Excellence award winners (2025)

Mariamawit Mohammed
Kate Dion
Calvin Ko

Roy Schultz Graduate Student Student Scholarship award winners (2025)

Guilherme Cezar
Berenice Munguia-Ramirez
Peng Li

2026 award winners will be announced during the awards session at the conference.

Roy Schultz Graduate Award Recipients

Roy Schultz Graduate Student

Excellence award winners (2025):

Mariamawit Mohammed
Kate Dion
Calvin Ko

Roy Schultz Graduate Student

Scholarship award winners (2025):

Guilherme Cezar
Berenice Munguia-Ramirez
Peng Li

2026 award winners will be announced during the awards session at the conference.

Porcine reproductive and respiratory syndrome (PRRS) remains one of the most economically significant endemic diseases affecting the United States swine industry, with recent estimates exceeding $1.2 billion annually in losses.1 Despite widespread implementation of herd closure and live-virus exposure strategies, time-to-stability following PRRSV outbreaks has increased substantially in recent years.

Replacement gilts represent a critical population during PRRSV elimination due to their potential to sustain viral circulation and introduce actively shedding animals into breeding herds. Factors including age at exposure, immune maturity, acclimation strategy, population flow, and opportunities for re-exposure may influence PRRSV shedding duration within replacement populations.

Factors Influencing PRRSV Shedding Duration

Immune maturity at exposure likely plays an important role in viral clearance dynamics. Younger gilts may exhibit delayed or less consistent immune responses, potentially contributing to prolonged shedding compared to older, more immunologically mature animals. Consequently, acclimation at older ages, when feasible, may improve immune consistency and reduce shedding duration.3-5

Acclimation design also influences PRRSV persistence within replacement populations. Continuous exposure, repeated viral recirculation, and population commingling may prolong instability and delay viral clearance. Controlled acclimation protocols emphasizing rapid homologous exposure, minimized re-exposure, and strict population flow management are preferred to reduce ongoing viral circulation.

Importantly, PRRSV clearance should not be defined solely by negative serum PCR results. Previous literature has demonstrated prolonged viral persistence within sampling the tonsillar and oropharyngeal tissues despite resolution of detectable viremia, suggesting some animals may continue to pose shedding risk after serum negativity.6

Diagnostic Monitoring Approaches

Diagnostic surveillance remains critical during acclimation and elimination programs. Serum sampling has traditionally been used to evaluate PRRSV status, however, previous studies have demonstrated variation in positivity rates across different sample types, including serum, oral fluids, and tonsil-oral-scrubbing (TOSc), depending on stage of infection and viral persistence.

Selection of sample type should align with the surveillance objective. Serum sampling may be more useful for evaluating viremia and active viral circulation, whereas TOSc or tonsil scraping may better detect prolonged viral persistence within tonsillar tissues after viremia has waned. Oral fluids and TOSc samples may also provide practical population-level surveillance approaches for monitoring ongoing circulation within populations.

PRRSV sequencing additionally remains important to confirm circulation of the expected variant and reduce the risk of introducing heterologous strains into replacement populations or breeding herds.

Discussion

Although no single intervention is likely to eliminate prolonged shedding risk entirely, biologically sound acclimation strategies combined with strict population flow management, adequate post-exposure stabilization time, and structured diagnostic surveillance may improve elimination success and reduce downstream instability risk.

References

Batista, L., Dee, S.A., Rossow, K.D., Deen, J., Pijoan, C. (2002) Assessing the Duration of Persistence and Shedding of Porcine Reproductive and Respiratory Syndrome Virus in a Large Population of Breeding-age Gilts. Can J Vet Res. 66(3),196-200.

Betlach, A.M., Linhares, D., Bisek, C., Yeske, P. (2025) Assessing the Role of Gilt-related Risk Factors for PRRSV Time-to-low-prevalenc. Allen D. Leman Conference.

Holtkamp D, and Osemeke O. (2024) PRRS Now Costs Pork Producers $1.2 Billion per Year. National Hog Farmer, July 30, 2024. https://www.nationalhogfarmer.com/livestock-management/prrs-now-costs-pork-producers-1-2-billion-per-year.

Li, P., Poeta Silva, A., Carnevale de Almeida Moraes, D., Yeske, P., Osemeke, O.H., Magalhaes, E.S., Silva, G., Linhares, D. (2024) Comparison of a Novel Rapid Sampling Method to Serum and Tonsil Scraping to Detect PRRS in Acutely Infected Sows. Prev Vet Med: 106082, 223.

Linhares DCL. (2025) PRRS Outbreak Management Program (POMP) database. Accessed February 6, 2025.

Mainquist-Whigham, C.E., Mauch-Swinford, E.D., Stephenson, E.W., Madigan, J.A., Cross, A.J., Rathje, T., McNeil, B.M. (2025) Risk Factors Associated with Prolonged Infection of Porcine Reproductive and Respiratory Syndrome Virus Determined by Whole-herd Sampling Methods. J Swine Health Prod. 33(3), 90-97.

Gilt Entry At End of Closures

Alyssa Betlach, DVM ^1*, PhD; Laura Dalquist, DVM ¹

¹ Swine Vet Center, St. Peter, Minnesota

^* Corresponding author abetlach@swinevetcenter.com

Betlach, A., Dalquist, L., (2026). Gilt Entry At End of Closures. ISU James D. McKean Swine Disease Conference 2026(1): 25839, 1-2. doi: https://doi.org/10.31274/swinedisease.25839

Introduction/Background

Porcine reproductive and respiratory syndrome virus (PRRSV) has caused substantial economic losses in the swine industry since the 1980s. Holtkamp and Osemeke recently estimated the annual cost of PRRSV to be $1.2 billion in the US.1 Many sow farms aim to eliminate PRRSV when infected; however, the time required to reach herd stability has increased in recent years. According to the PRRSV Outbreak Management Program (POMP) database, the median time to stability has increased from 27 weeks in 2011 to 49 weeks for herds affected by the L1C.5 variant outbreaks.2 For herds in the 90th percentile, time to stability may reach 62 weeks.

Traditionally, farms are loaded with gilts, homogenized to the circulating PRRSV variant, and closed to any new live animal introductions until the herd tests negative. With herd closure periods now extending 49-62 weeks, a sizable gap in gilt entry is common, resulting in additional production loss. With traditional closures, farms often stretch their existing gilt inventory and breed females they would not normally use in order to maintain breed target. These practices lead to reduced sow performance and longevity, farm inefficiencies, and other unintended consequences.

Methods

To eliminate this gilt availability gap, farms have continued to acclimate feeder gilts to PRRS via herd-specific LVI in an off-site location prior to sow farm entry. In this approach, a gilt developer unit (GDU) is secured in an acceptable location off-site from the sow farm, shortly following a new PRRS introduction in the sow farm. The GDU is then populated with gilts ranging from feeder-pig age to nearly breeding eligible, depending on the needs of the recipient sow farm. The GDU site is acclimated to the recipient sow farm’s PRRS LVI and managed appropriately.

Gilts are tested thoroughly prior to monthly movement to the sow farm to ensure no additional PRRSV variants or other pathogens are present in the population. PRRSV sequencing is expected pre-shipment during the first 3-4 monthly deliveries to the sow farm. New feeder gilts are added to the GDU site monthly, with timing managed so that entry occurs shortly after the most recent group of acclimated, select gilts has moved to the sow farm. This allows for the largest window of time between new gilt entry and acclimated gilt departure. All incoming feeder gilts must be acclimated via LVI to the sow farm PRRSV within 48 hours of arrival, with the shortest possible timeframe preferred.

This cycle of entering and acclimating new feeder gilts in the GDU continues until the recipient sow farm has reached predetermined PRRS testing milestones. One common milestone is the completion of one full turn through the farrowing house of PRRSV PCR negative processing fluids (tested by room), followed by PRRSV PCR negative 60-piglet blood samples targeting the most clinically affected piglets across the farrowing house. Once this milestone is reached, no additional feeder gilts are added to the GDU for acclimation. Typically, gilts will continue to flow into the sow farm at their designated age until the acclimated GDU is empty. PRRS negative gilts are then staged at another location and enter the sow farm according to the farm’s typical monthly schedule after the last of the acclimated gilts have entered. Usually, when the first negative gilts enter the farm, the last positive PRRSV result from the sow farm occurred approximately five months earlier.

This approach has allowed the sow farm to make sound breeding decisions and maintain normal culling practices, thereby preserving parity structure throughout the PRRS elimination process. It also removes the need for a PRRS negative breeding project on the backside of a PRRS elimination.

Discussion

The option to continuously expose gilts for a period of time may not be possible for all sow farms. There are a few requirements for this program to be successful:

An off-site GDU location in a good area with solid biosecurity that isn’t likely to be infected with another PRRSV variant or other pathogens.
Strict PRRSV exposure and management protocols must be followed at the GDU.
Timely and thorough testing and PRRSV sequencing of the GDU site to protect the sow farm.
The recipient sow farm undergoing elimination should have an outbreak history that provides adequate time to receive all acclimated gilts into the farm prior to the next outbreak (14 months or more with no outbreaks would be desired).

References

Holtkamp D, and Osemeke O. “PRRS Now Costs Pork Producers $1.2 Billion per Year.” 2024. National Hog Farmer, July 30, 2024. https://www.nationalhogfarmer.com/livestock-management/prrs-now-costs-pork-producers-1-2-billion-per-year.

Linhares DCL. PRRS Outbreak Management Program (POMP) database. 2025. Accessed February 6, 2025.

Can Swine Movement Networks Drive Regional Patterns of PRRSV Genetic Diversity?

Isadora Martins Pinto Coelho ¹, Swaminathan Jayaraman ¹, Michael Zeller ¹, Giovani Trevisan ¹, Douglas Groth ², Kinath Rupasinghe ¹, Tina Peterson ¹, Gustavo S Silva ¹

¹ College of Veterinary Medicine, Department of Veterinary Diagnostic and Production Animal Medicine, Iowa State University, Ames, Iowa

² Carthage Veterinary Service, Carthage, IL

^* Corresponding author isadorac@iastate.edu

Coelho, I.M.P., Jayaraman, S., Zeller, M., Trevisan, G., Groth, D., Rupasinghe, K., Peterson, T., Silva, G.S., (2026). Can Swine Movement Networks Drive Regional Patterns of PRRSV Genetic Diversity?. ISU James D. McKean Swine Disease Conference 2026(1): 25840, 1-4. doi: https://doi.org/10.31274/swinedisease.25840

Introduction/Background

Characterizing PRRSV genetic diversity is important for understanding viral circulation patterns, identifying areas with greater co-circulation of diverse variants, and assessing the risk of new variant introduction. These conditions may promote viral recombination, increase disease pressure, and challenge vaccine effectiveness, ultimately supporting targeted disease surveillance and control strategies across swine-producing regions. Traditional administrative regions (e.g., counties, states) and animal movement-derived communities provide complementary approaches for describing viral diversity and epidemiological connectivity. Movement-derived communities may reveal indirect connections between geographically separated production systems but connected through other channels, e.g., animal movements, highlighting potential pathways for viral circulation and spread that are not captured by traditional regional boundaries. The objective of this study was to characterize PRRSV genetic diversity across counties and animal movement-derived communities within different swine production systems. By comparing diversity patterns across administrative and movement-based spatial frameworks, the study aimed to understand how swine movement connectivity shapes PRRSV diversity across swine-producing regions and identify regions with increased co-circulation of genetically diverse strains.

Methods

Animal movement data, ORF5 PRRSV genetic sequences, and premises metadata from the Porcine Regional Information Management Ecosystem (PRIME), an epidemiological cyberinfrastructure developed at Iowa State University, were analyzed for the 2023-2024 and 2024-2025 PRRSV seasons. PRRSV seasons were defined according to industry convention, running from July 1 through June 30 of the following year. Eligibility criteria included sites from systems with consistent movement data availability throughout the study period. Premise-level movement networks were first constructed using individual premises as nodes to evaluate direct animal movement patterns. County-level movement networks were then constructed by aggregating premises-level movements into county-to-county edges. Community detection was performed using the fast-greedy modularity optimization algorithm applied to undirected weighted networks. Genetic diversity within counties and movement-derived communities was characterized using sequence counts, genetic richness, and Simpson’s diversity index (Simpson, 1949). Genetic richness was defined as the number of distinct PRRSV sublineages identified within each geographic or movement-defined unit and, when variant classification data were available, the number of distinct PRRSV variants detected. Simpson’s diversity index was used to describe the diversity of PRRSV sublineages and variants circulating within each county or movement community. The index ranges from 0 to 1, where values closer to 0 indicate low diversity dominated by a single sublineage or variant, and values closer to 1 indicate higher diversity with multiple sublineages or variants circulating more evenly. The index can also be interpreted as the probability that two randomly selected sequences belong to different sublineages or variants.

Results

Genetic data included 2,032 distinct PRRSV ORF5 sequences from 652 sites. The most frequently identified PRRSV genetic group was L1C.5 (n = 507 sequences), followed by L1D (n = 339), L5A (n = 306), L1A (n = 286), and L1C (n = 235). Additional groups included L5 (n = 131), L1C.2 (n = 123), and L1H (n = 71), while the remaining groups each had fewer than 15 sequences. County-level diversity analysis showed that Southeast, Central, and Northwest Iowa, as well as Western Illinois, had higher Simpson’s diversity values, suggesting a more heterogeneous viral population and potentially multiple sources of introductions of the virus (Figure 1). This is consistent with high animal density, multiple production systems, and high animal movement connectivity. Clusters of higher diversity values were observed, gradually decreasing across neighboring counties.

fig:

Figure 1. Spatial distribution of Simpson’s diversity index for PRRSV sublineages and variants at the county level during the 2023–2024 and 2024–2025 PRRSV seasons.

When evaluated by movement-derived communities, 10 county-based movement communities were identified across the study region (Figure 2). The four communities in Iowa (1, 3, 4, and 8) exhibited high Simpson’s diversity values (>0.75), indicating relatively even circulation of multiple PRRSV variants within highly connected movement regions.

fig:

Figure 2. County-based movement communities identified from the swine movement network during the 2023-2024 and 2024-2025 PRRSV seasons. Numbers inside each community represent Simpson’s diversity index calculated using PRRSV ORF5 sequences from premises

Community 4 showed the highest genetic richness (12), while Communities 1, 3, and 8 also demonstrated elevated diversity despite differences in sequence counts (Table 1). In contrast, Communities 5, 7, and 10 exhibited low diversity values, meaning dominance of a limited number of viral variants. Several counties with low or moderate individual diversity values were part of highly connected movement communities that collectively exhibited high genetic diversity. This suggests that animal movement networks capture epidemiologically relevant links between geographically separated counties that may share PRRSV circulation dynamics despite administrative boundaries.

Table 1. County-based movement communities identified from the swine movement network.

Community	Counties (n)	Sites (n)	Prod Systems (n)	Sequences (n)	Genetic richness	Simpson’s Index
1	34	348	3	413	9	0.79
3	31	168	5	274	10	0.78
8	28	350	4	630	10	0.75
4	25	123	5	240	12	0.75
2	35	214	1	6	4	0.72
6	9	42	3	19	3	0.58
9	15	57	2	18	5	0.57
10	5	11	3	4	2	0.5
7	19	61	1	19	4	0.49
5	18	91	1	1	1	0

The premises-level movement network included 1,452 unique premises, of which 88.4% were growing herds (n = 1,297), 8.2% were breeding herds (n = 120), and 2.4% were gilt development units and isolation sites (n = 35). Community detection using premises as nodes is shown in Figure 3, which depicts communities containing at least 5 premises, yielding 17 distinct movement communities. Colored polygons highlight four communities that included premises from multiple production systems, suggesting broader inter-system connectivity patterns (Communities 3, 5, 6, and 9). Community 3 included 201 premises distributed across four states and three production systems, with 335 sequences and a genetic richness of 12, and a Simpson’s diversity index of 0.80. Community 5 contained 181 premises across three states and two production systems, totaling 228 sequences, a genetic richness of eight, and a Simpson’s diversity index of 0.76. Community 6 included 58 premises distributed across three states and four production systems, with 21 sequences, a genetic richness of four, and a Simpson’s diversity index of 0.62. Community 9 contained 145 premises across four states and three production systems, totaling 285 sequences, a genetic richness of 10, and a Simpson’s diversity index of 0.76. The presence of multiple PRRSV sublineages and variants within highly connected multi-system communities suggests that animal movement connectivity may facilitate the introduction, co-circulation, and maintenance of genetically diverse viral populations across production systems and geographic regions.

fig:

Figure 3. Premise-level movement communities identified using swine movement network analysis during the 2023-2024 and 2024-2025 PRRSV seasons. Each color represents a distinct movement-derived community, totaling 17 identified communities.

Conclusions

These findings highlight the importance of evaluating PRRSV diversity beyond traditional regional boundaries and considering the role of animal movement connectivity in shaping viral circulation patterns. While county-level analyses identified important geographic differences in diversity, movement-derived communities revealed indirect epidemiological connections between counties that would otherwise appear unrelated. This shows that systems and regions are not epidemiologically isolated, and that movements occurring within one production system or county may influence viral circulation across broader connected networks. The integration of movement and genetic data through the PRIME infrastructure provides an important framework for identifying regional transmission patterns and supporting more coordinated regional disease surveillance and control strategies.

References

SIMPSON, E. Measurement of Diversity. Nature 163, 688 (1949). doi: https://doi.org/10.1038/163688a0

Reemergence of New World Screwworm in Mexico: Current Situation and Challenges

Alejandrina Da Silva ^1*, Iván Espinosa ², Roger I. Rodriguez-Vivas ³, Daniel Linhares ¹, Marcelo Almeida ¹, Chris J. Rademacher ¹

¹ VDPAM, Iowa State University College of Veterinary Medicine, Ames, Iowa

² Organización de Porcicultores Mexicanos (OPORMEX), Mexico

³ Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Mexico

^* Corresponding author dasil001@iastate.edu

Da Silva, A., Espinosa, I., Rodriquez-Vivas, R., Linhares, D., Almeida, M., Rademacher, C., (2026). Reemergence of New World Screwworm in Mexico: Current Situation and Challenges. ISU James D. McKean Swine Disease Conference 2026(1): 25841, 1-5. doi: https://doi.org/10.31274/swinedisease.25841

Introduction/Background

The New World Screwworm (NWS), Cochliomyia hominivorax (C. hominivorax), is an obligate parasitic fly that causes myiasis in warm-blooded animals, leading to severe tissue damage, secondary infections, and significant economic losses. Myiasis caused by C. hominivorax is a significant cause of mortality among newborn calves, in addition to directly impacting milk production, fertility, feed conversion rates, and animal weight gain. In other animal species (including humans), the damage caused by infestation is associated with severe health complications and mortality in untreated cases. Following its eradication from Mexico in 1991 and subsequent regional elimination across Central America by 2006, reemergence in Central America beginning in 2023 and subsequent detection in Mexico (late 2024) have raised concern regarding rapid geographic expansion and potential re-establishment. Favorable climatic conditions, host availability, and livestock movement contribute to its spread, representing a major threat to animal health systems.

Methods

Official epidemiological reports, dashboards, and technical bulletins from the Servicio Nacional de Sanidad, Inocuidad y Calidad Agroalimentaria of Mexico (National Service for Agri-Food Health, Safety, and Quality; SENASICA), and the World Animal Health Information System of the World Organization for Animal Health (WOAH-WAHIS) were reviewed. Data regarding cumulative case counts, geographic distribution, affected species, lesion types, and control strategies were compiled to characterize the current epidemiological situation and identify key challenges for containment and eradication efforts. A confirmed NWS case was defined as an animal with myiasis-compatible lesions and confirmation of C. hominivorax larvae through official diagnostic or surveillance reporting systems. For swine-specific analyses, WOAH-WAHIS reports were interpreted at the report-line level, where each report included the number of swine cases and the associated susceptible pig population. Figures and epidemiological visualizations were generated with R using ggplot2 and spatial analysis packages.

Results

As of May 5, 2026, a total of 23,076 cumulative NWS cases had been reported in Mexico since the first detection in November 2024. Reported cases remained concentrated in southern and southeastern states, including Chiapas, Oaxaca, Veracruz, Yucatán, Tabasco, and Campeche, with evidence of progressive geographic spread (Figure 1).

Cattle accounted for most reported cases (65.4%), followed by canines (17.6%), while swine represented a smaller but epidemiologically relevant proportion (6.8%; 1,575 confirmed cases).

Other species collectively accounted for approximately 10.1% of cases (Figure 2).

Despite their lower frequency, swine cases remain relevant due to their association with specific production systems and management-related risk factors. The reduced incidence in pigs is likely linked to intensive production systems, higher biosecurity standards, and continuous monitoring, which may limit exposure. Reported swine cases were predominantly associated with backyard or low-biosecurity production systems.

Across species, infestations were consistently associated with pre-existing lesions. The most frequently reported lesion types included umbilical infections (4,297 cases) and traumatic wounds (4,124 cases), followed by injuries related to barbed wire, fighting, and other causes (Figure 3). These lesions facilitate larval infestation and rapid disease progression characterized by tissue destruction and secondary infection.

Swine-related WOAH-WAHIS reports accumulated between November 24, 2024, and May 5, 2026, were primarily concentrated in southeastern Mexico, particularly in Chiapas, Oaxaca, Veracruz, Yucatán, Tabasco, and Campeche (Figure 4). Most reported swine cases were associated with backyard or low-biosecurity pig production systems, while only one report corresponded to an intensive commercial swine operation in Chiapas. However, because pigs can suffer frequent injuries from traumatic objects, castrations, tail docking, birth injuries, as well as umbilical wounds in newborn piglets, they remain susceptible to NWS myiasis.

As of April 2026, 253 cases of myiasis caused by NWS had been reported in the human population of Mexico. The states with the highest frequency of cases were Chiapas, Oaxaca, and Yucatán. Older patients with diabetes or other immunosuppressive conditions are at higher risk of developing myiasis due to poor circulation, reduced pain perception, and impaired wound healing.

Control efforts have relied on a national regionalization strategy dividing the country into affected, buffer, and free zones, allowing targeted implementation of surveillance, movement control, and intervention measures. Control strategies include activation of the National Animal Health Emergency System (DINESA), enhanced surveillance, active case notification, diagnostic confirmation, movement control and inspection, treatment of affected animals, producer education campaigns, trapping systems, and deployment of sterile insect technique (SIT) as the cornerstone of eradication efforts. In parallel, industry organizations such as the “Organización de Porcicultores Mexicanos (OPORMEX)” have contributed to reinforcing biosecurity practices and communication within the swine sector.

Currently, only one sterile fly production facility exists worldwide, belonging to the Panama-United States Commission for the Eradication and Prevention of Screwworms (COPEG), with a capacity to produce 100 million sterile flies per week. Mexico is expected to establish a sterile fly production facility with a capacity of 100 million flies per week by 2026, and by 2027, the United States will have a production capacity of 300 million flies per week. With this technology and international collaboration, it is hoped that this pest will once again be eradicated in Mexico and Central America.

Conclusions

The reemergence of NWS in Mexico represents a significant sanitary and economic threat. While swine is less frequently affected due to intensive production systems, their involvement highlights the importance of targeted vigilance in backyard and low-biosecurity production systems. Eradication efforts face multiple challenges, including wide geographic dispersion in environmentally suitable regions, continuous animal movement, operational complexity of large-scale sterile insect programs, and the need for sustained coordination among stakeholders.

The implementation of zonal control strategies supports containment efforts but also underscores the difficulty of maintaining disease-free areas under conditions of ongoing case detection. The high volume of field reports and surveillance activities further highlights the operational burden on animal health systems. Strengthening early detection, maintaining high biosecurity standards, and ensuring rapid response capacity—supported by coordinated efforts between authorities and industry groups such as OPORMEX—will be critical to limit spread and support long-term eradication. Selected field cases from Mexico and Central America will also be presented during the oral presentation to highlight operational challenges and mitigation strategies associated with NWS under field conditions.

References

SENASICA. Epidemiological reports, dashboards, and technical bulletins on New World screwworm (2024–2026). Available from: https://www.gob.mx/senasica Accessed May 2026.

Valdez-Espinoza UM, Fadda LA, Marques R, Osorio-Olvera L, Jiménez-García D, Lira-Noriega A. The reemergence of the New World screwworm and its potential distribution in North America. Scientific Reports. 2025; 15:23819. https://doi.org/10.1038/s41598-025-04804-9

World Organization for Animal Health (WOAH). World Animal Health Information System (WAHIS). Available from: https://wahis.woah.org/. Accessed May 2026.

fig:

Using Water Consumption Data To Predict Disease Outbreaks

Haley Schwecke ^1*, Alyssa Betlach ¹

¹ Swine Vet Center, St. Peter, Minnesota

^* Corresponding author hschwecke@swinevetcenter.com

Schwecke, H., Betlach, A., (2026). Using Water Consumption Data To Predict Disease Outbreaks. ISU James D. McKean Swine Disease Conference 2026(1): 25842, 1-2. doi: https://doi.org/10.31274/swinedisease.25842

Introduction/Background

Early recognition and confirmation of disease outbreaks are critical for timely implementation of intervention strategies aimed at reducing associated morbidity, mortality, and production losses in commercial swine systems. Traditional indicators, including clinical signs, mortality, and individual treatments, are often lagging indicators that occur after disease circulation is established within a population. In contrast, changes in water intake may serve as an earlier, leading indicator of health challenges. Water disappearance is routinely monitored through barn controller systems and may serve as a proxy for identifying potential disease breaks within a population. Therefore, the objective of this study was to evaluate changes in water consumption associated with disease outbreaks and characterize the magnitude of water intake reductions observed during confirmed porcine reproductive and respiratory syndrome virus (PRRSV) and influenza outbreaks in commercial wean-to-finish barns.

Materials and Methods

Retrospective production, water consumption, environmental, and health-related data were compiled from commercial wean-to-finish barns at the room level, with the room serving as the observational unit. Data encompassed approximately 55,000 pigs across 23 production turns over a four-year period. Daily water disappearance (gallons/room) was collected from barn controller systems at approximately the same time each day and evaluated relative to days on feed.

A healthy baseline period prior to outbreak recognition was utilized to establish expected water disappearance patterns. Water disappearance trends were assessed using an exponentially weighted moving average (EWMA), with upper and lower monitoring thresholds generated using ±0.5 standard deviations in R. Thresholds were selected to improve sensitivity for identifying biologically meaningful deviations in water disappearance patterns. When reductions in water disappearance below thresholds were identified, associated diagnostic and production-related events (e.g., marketing, pig movements, or equipment issues) were evaluated descriptively. Temporal relationships between water intake reductions and lagging indicators, including individual treatments and mortality, were also assessed. Disease outbreaks were classified based on clinical presentation and laboratory diagnostic confirmation. For confirmed outbreaks, percentage reductions in water intake and time-to-detection relative to other indicators were summarized.

Results

Reductions in water disappearance commonly preceded other indicators, such as mortality and number of daily individual treatments. In representative outbreak events, increases in individual treatments occurred approximately 6 days following reductions in water intake, while increases in mortality occurred approximately 9 days later.

The median reduction in water disappearance associated with confirmed lateral PRRSV outbreaks was 22%, while the median reduction associated with influenza outbreaks was 14%. Overall, findings suggest that approximately a 20% reduction in water intake may serve as a leading indicator of disease outbreaks in commercial wean-to-finish populations.

Discussion and Conclusion

Results from this investigation suggest that reductions in water intake may serve as an early and objective indicator of disease outbreaks in commercial swine systems. Reductions in water disappearance preceded increases in individual treatments and mortality, suggesting water intake monitoring may aid in earlier recognition of health challenges. However, water intake data should be interpreted alongside management and environmental factors that may influence water disappearance patterns. Additional investigation evaluating sensitivity, specificity, positive predictive value, and negative predictive value is needed to further characterize the predictive performance of water intake monitoring for disease outbreak detection. Overall, these findings support the potential utility of water disappearance monitoring as an early surveillance indicator in commercial swine barns.

Lessons Learned in Dealing With IAV-S in Sow Herds

Bob Thompson, DVM, MS ^*; Larry L. Coleman, DVM

^* Corresponding author rwthompsondvmms@gmail.com

Thompson, B., Coleman, L.L., (2026). Lessons Learned in Dealing With IAV-S in Sow Herds. ISU James D. McKean Swine Disease Conference 2026(1): 25843, 1-2. doi: https://doi.org/10.31274/swinedisease.25843

Introduction/Background

Most of my experience in dealing with influenza has been in the breeding stock environment, eliminating the virus from sow herds to create flu negative weaned pigs and ultimately sow herds. My initial experience was in creating a negative genetic nucleus herd for PIC when the Apex GN was stocked in 2008 ¹. Following that, I started working on elimination projects within the PIC multiplication herds ². In all these projects we used the Harris Biologics Replicon technology which subsequently became the Merck Sequivity HA vaccine of today. In one of the projects, when we were having trouble eliminating the virus with the HA vaccine, we added in Zoetis’s FluSure as a heterologous Prime Boost. It helped us increase the maternal antibodies enough to be able to wean PCR negative pigs. ^3, 4 All of the herds I worked with had internal replacements, which makes it harder to maintain the negative status.

Within the past five years Dr. Coleman and I had a persistent H3N2 virus. We were unsuccessful in eliminating the virus with just the HA vaccine. The usual McRebel protocol was utilized, as had been the case in all the previous eliminations. In an effort to push the maternal antibodies higher we added in the Sequivity NA vaccine prefarrow. The NA was enough to make the elimination a success.

Since the success with the NA vaccine, we have used two whole herd vaccinations for two outbreaks in negative herds with H1 human-like viruses. It has been successful in both those cases. I do realize that many times the H1 viruses aren’t very fit for the pig and the viruses may die out on their own. We just did not want to take the chance.

The Pipestone veterinary group has presented several good elimination protocols that you can reference beyond the ones I presented in the early 2000’s ^5, 6.

Lessons Learned

Decide what your goal is with the herd, at the very least, in my opinion, you want to wean a flu negative pig.
For the overall health of the sow herd, influenza vaccination of some sort is important. It can be a commercial or autogenous product.
Dr. Coleman and I prefer to vaccinate gilt replacements with two doses of the HA autogenous vaccine prebreeding.
Boostering the sow herd depends on the influenza status of the weaned pigs. If they are PCR negative in oral fluids, it is not necessary to vaccinate the whole herd.
If weaned pigs are PCR positive then implement a prefarrow booster to improve the maternal antibodies.
I recommend sequencing the IAV-S field virus for both the HA and NA portions to make a decision on which vaccine to use.
Due to the ease of using a genetic sequence, we have chosen the Sequivity HA vaccine for the herd and gilt replacements.
We keep dendograms of the viruses circulating in our herds and design the vaccine from the most current ones circulating.
When the Sequivity NA vaccine became available as an off-the-shelf product, we started using it if the sequence similarity is close to what is in that vaccine.
The data bank isn’t as detailed with the H1 viruses so we have used the NA vaccine when the similarities are not as close as we normally use.
Research has shown influenza viruses circulate more frequently in the Fall and Spring. Many producers have gone to whole herd vaccinations twice a year to have the best immunity in the herd.
Vaccinating gilts as mentioned above and boostering the sows prefarrow is another method of keeping maternal antibodies high.

When there is good herd location and high biosecurity protocols most new viruses enter via employees. I encourage all staff to get an annual influenza booster realizing the vaccine isn’t always closely matched to what may be circulating that year. We also have employees take temperatures daily for screening to reduce new introductions as much as possible. In addition to the references listed below, the Merck Flu Playbook is an excellent resource. The link is included below.

References

Culhane et al. (2019) Efficacy of Prime-boost Vaccination Protocols in Pigs Challenged with Influenza A Viruses. AASV, 164. doi: https://doi.org/10.3390/v12090968

E. Koep (2026) Practitioner Experiences with IAV Elimination: Success and failures AASV Preconference #5

E. McDowell (2024) Practitioner Perspective on Influenza Management AASV Preconference #3

Flu Playbook https://www.merck-animal-health-usa.com/downloads/swine-influenza-protocol-booklet/

Thompson et al. (2009) Creating an SIV Negative Sow Herd. Leman, 59.

Thompson et al. (2016) Elimination of Influenza A Virus in Multiple Breed-to-wean Herds. Leman Conference 2016.

Thompson et al. (2020) A Heterologous Prime Boost Mass Vaccination Protocol for IAV-S Control. AASV 2020, 93.

Experiences With Rota Virus Control

Paul Yeske ¹

¹ Swine Vet Center PA, St. Peter MN, USA

^* Corresponding author pyeske@swinevetcenter.com

Yeske, P., (2026). Experiences With Rota Virus Control. ISU James D. McKean Swine Disease Conference 2026(1): 25844, 1-2. doi: https://doi.org/10.31274/swinedisease.25844

Introduction/Background

Rotavirus is one of the common causes of neonatal enteric disease in suckling pigs. It remains a persistent challenge to production due to its high transmissibility, environmental resilience, and genetic diversity. Infection is most common in piglets less than four weeks of age, where it manifests as acute diarrhea, dehydration, reduced weight gain, and, in severe cases, mortality. It is usually self-resolving in 5-7 days for most pigs.

Materials and Methods

The epidemiology of porcine rotavirus can be complex, involving multiple co-circulating species: primarily rotavirus A, B, and C with frequent mixed infections (of one or more or all three). ^1,2 These viruses are transmitted via the fecal oral route, and their ability to persist in the environment, coupled with continuous shedding from asymptomatic carriers such as sows, facilitates endemic herd circulation. The antigenic heterogeneity among strains can limit cross-protection and presents a major barrier to effective immunological control.

Control strategies focus on prevention through the reduction of viral exposure in the environment and lactogenic immunity.

Lactogenic immunity is the cornerstone of early protection. Consequently, pre-farrowing vaccination of sows is widely implemented to boost maternal antibody titers. ^3,4 However, vaccine efficacy remains inconsistent due to antigenic mismatch between vaccine strains and field isolates and types. Modified live vaccines generally produce stronger and more durable immune responses compared to inactivated vaccines but are only available for Rota A, while next generation vaccines have been very effective in control. Most herds will also include feedback material as well, including piglet scours and intestines from mortalities.

Given these limitations, management and hygiene practices are critical components of rotavirus control. Effective measures include all-in/all-out production systems, rigorous cleaning and disinfection protocols, control of fomites, and minimizing cross-fostering to reduce pathogen transmission between litters especially with clinical signs. Optimizing farrowing house sanitation and ensuring adequate colostrum intake immediately after birth are essential to reducing disease incidence and severity.

Strategies aimed at improving control outcomes include the development of next-generation vaccines with broader antigenic coverage, including multivalent and genotype-matched formulations. Advances in molecular diagnostics and genomic surveillance are enabling better characterization of circulating rotavirus strains, thereby informing vaccine design and epidemiological interventions.

Conclusions and discussion

Effective control of rotavirus in suckling pigs requires a comprehensive and integrated approach that combines maternal immunization, high levels of hygiene, stringent biosecurity, and ongoing surveillance. Addressing the challenges by viral diversity and environmental persistence are essential for reducing the burden of rotavirus-associated disease and improving productivity.

References

Brunner L. (2025) Piglet diarrhea and vaccine efficacy: Observations from the field. Leman Conference Proceedings 2025.

Fu, Z. F., et al. (1990). Transfer of maternal antibody against rotavirus in piglets. Journal of General Virology, 71(10), 2473–2478.

Rossow K. et al. (2012) Rotavirus: Interpretation of diagnostic results. AASV Proceedings 2012, 431-432.

Rybkowska, W., et al. (2025). Prevalence and control strategies of rotavirus in piglets. Pathogens, 14(10), 1055. doi: https://doi.org/10.3390/pathogens14101055

Is That Bad Coccidia or Something Else?

Paul Yeske ^1*

¹ Swine Vet Center St Peter MN USA

^* Corresponding author pyeske@swinevetcenter.com

Yeske, P., (2026). Is That Bad Coccidia or Something Else?. ISU James D. McKean Swine Disease Conference 2026(1): 25845, 1-2. doi: https://doi.org/10.31274/swinedisease.25845

Introduction/Background

Neonatal diarrhea continues to be one of the most significant health challenges in swine production, contributing to substantial economic losses due to reduced growth performance and increased management costs and mortality in severe cases. There are multiple etiological agents that can be involved in pigs over 5-7 days of age. Sapovirus and coccidiosis (Cystoisospora suis) represent two important but distinct causes of enteric disease in suckling piglets. Additional pathogens, including Rotavirus and bacterial agents, like Clostridium and E. coli can also be present, increasing the severity of disease and complicating a diagnosis.

Materials and Methods

Sapovirus is an emerging viral pathogen increasingly recognized in cases of piglet diarrhea ^1,2. Infection typically occurs in piglets between 1 and 4 weeks of age (most predominately 7-14 days and resolving by weaning). Sapovirus is transmitted via the fecal–oral route, often through contaminated environments, maternal shedding, or infected litter/pen mates. Sapovirus primarily targets the small intestine, where it causes villous atrophy and enterocyte dysfunction, resulting in malabsorptive diarrhea. Clinical signs are usually mild to moderate, including soft to watery feces and reduced weight gain. However, co-infections with other enteric pathogens such as rotavirus or enterotoxigenic Escherichia coli can exacerbate disease severity. A key feature of Sapovirus infection is its often subclinical or self-limiting nature, which complicates detection and underestimates its contribution to production losses. Currently, there are new generation prescription vaccines available but no treatments for Sapovirus in pigs, and the immune response following infection is poorly characterized due to the virus’s genetic diversity.

In contrast, coccidiosis in piglets is a well-established parasitic disease caused predominantly by Cystoisospora suis. It affects piglets typically between 5 days and weaning and is characterized by infection of intestinal epithelial cells, particularly in the jejunum and ileum. Following ingestion of sporulated oocysts, the parasite undergoes intracellular replication, leading to destruction of enterocytes, villous atrophy, and inflammation ^3,4. Clinically, coccidiosis presents as pasty to watery, often yellowish diarrhea that may persist for several days and is frequently associated with poor growth and uneven litter performance. Unlike many viral enteric infections, coccidiosis is rarely associated with high mortality but can cause long-term production deficits and reduced weight gain. Environmental contamination plays a critical role in transmission, as oocysts are highly resistant and can persist in farrowing environments despite routine cleaning. Whitewash has been helpful in control along with thorough cleaning.

The epidemiology of these two diseases highlights key contrasts. Sapovirus infections are driven by viral shedding dynamics, rapid transmission, and frequent co-infections, whereas coccidiosis is closely linked to environmental hygiene and the buildup of infective oocysts. Diagnostic differentiation is therefore essential: Sapovirus is typically detected using molecular methods PCR, while coccidiosis is diagnosed through fecal flotation, microscopic identification of oocysts, and PCR. Histopathology can further distinguish the two, revealing viral-induced villous atrophy in Sapovirus infections versus intracellular parasitic stages and epithelial necrosis in coccidiosis.

Control

Strategies also differ substantially between the organisms. For Sapovirus, management focuses on general biosecurity, sanitation, and minimizing co-infections, as well as optimizing colostrum intake. Next generation vaccines have proven to be very effective when matched up with circulating strains. In contrast, coccidiosis can be effectively controlled through targeted prophylactic treatment, most commonly with anticoccidial agents such as toltrazuril administered to piglets during the first days of life. Environmental hygiene is critical for both diseases, but particularly for coccidiosis, where thorough cleaning, drying, and disinfection of farrowing crates are necessary to reduce oocyst survival. Whitewash has been effective means of control on problem farms. Controlling coinfections, including Rotavirus and Clostridium, with vaccination to sows can help reduce the incidence of coccidia as well.

Conclusions and Discussion

In summary, while Sapovirus and coccidiosis both contribute to diarrheal disease in suckling piglets and can clinically look similar in the barn, they differ fundamentally in etiology, pathogenesis, and control. Sapovirus represents a viral, often subclinical infection with vaccination and hygiene as main methods of control, whereas coccidiosis is a parasitic disease with well-defined life cycle dynamics and effective chemoprophylaxis. Integrated herd health programs that incorporate accurate diagnostics, improved hygiene, and pathogen-specific control measures are essential to mitigate the impact of both conditions and enhance piglet health and productivity.

References

Dufkova, L., et al. (2013). Detection and characterization of Sapo viruses in pigs. Veterinary Microbiology, 164(1–2), 144–152. doi: https://doi.org/10.1016/j.vetmic.2009.05.013

Mundt, H. C., et al. (2007). Control of Cystoisospora suis infection in piglets with toltrazuril. Veterinary Parasitology, 146(1–2), 86–95.

Stuart, B. P., et al. (1982). Coccidiosis in swine: Clinical, pathological, and epidemiological observations. Journal of the American Veterinary Medical Association, 181(4), 383–386.

Vlasova, A. N., et al. (2017). SaV infection in swine and its role in enteric disease. Emerging Infectious Diseases, 23(8), 1406–1409.

2026 ISU McKean Swine Disease Conference

Science with Practice Award

Recipients

Elevating the profile of Graduate Students

Elevating the profile of the VDPAM Graduate program

Recipients

Roy Schultz Graduate Student Excellence award winners (2025)

Roy Schultz Graduate Student Student Scholarship award winners (2025)

Roy Schultz Graduate Award Recipients

Roy Schultz Graduate Student

Excellence award winners (2025):

Roy Schultz Graduate Student

Scholarship award winners (2025):

Contents

JUNE 23RD

International Enteric Diseases Workshop

International PRRS Management Workshop

JUNE 24TH

Afternoon Concurrent Session #1: Scientific Track

Afternoon Concurrent Session #2: Applied Cases Track

Harvard-style Citation

Vancouver-style Citation

APA-style Citation

Non Specialist Summary