Ontario Animal Health Network (OAHN) Swine Network Quarterly Veterinary Report

Senecavirus A (SVA) Ontario Update

Starting in 2015, Senecavirus A (SVA) has caused intermittent complications with respect to the export of Canadian cull animals to the United States. This disease resembles reportable swine vesicular diseases. This is a national issue and since June 2025 has impacted Ontario cull sow movements.

In July 2025, the APHIS and the USDA removed the export eligibility status for a cull sow assembly in Ontario due to SVA lesions being seen in cull sows sent to a USDA processing facility. These lesions initiated foreign animal disease investigations at this US processing plant. The suspect animal(s) were initially quarantined for individual inspection and further testing. Since the initial site, another 2 Ontario cull sow assembly sites have also had their export eligibility status revoked by APHIS and the USDA for similar reasons. The affected assembly sites accept cull sows from Quebec, the Maritimes and Ontario. Each affected assembly site must action the USDA requirements including emptying each assembly site so that it can be thoroughly cleaned and disinfected before each affected site could regain their export status. The assembly site operators are working closely with veterinarians to develop the required SOP’s, and to begin actioning the USDA listed requirements. This export disruption will have the potential to create significant effects on the eastern Canadian cull sow system.  While the process is started, it is expected to take an undetermined amount of time to action all of the USDA requirements. Similar export issues, related to SVA, have arisen previously in western Canada. It is important to continue inter-provincial industry collaboration on this issue.

Producers and veterinarians involved in export inspections, need to be diligent in checking all animals for SVA type lesions including blisters, ulcers on the snout, ears, face, on the coronary band or between the claws on the feet before shipping them for slaughter, cull markets and or directly for export to the USA.

Porcine Epidemic Diarrhea (PEDV)/ Porcine Deltacoronavirus (PDCoV)

Jessica Fox the manager of Swine Health Ontario (SHO) provided an update on PED and PDCoV cases seen in Q2 of 2025. Jessica reported that for this quarter, there were 9 PDCoV cases and 12 PED cases. For the PDCoV cases, 3 were sow units and the 6 were nursery-finish, all of which were movement-related (not independent outbreaks). For the PED cases, there were 5 sow barn cases and 7 nursery-finish cases, 6 of which were movement-related. Overall, the case load was decreased compared to Q1 2025 and Q4 2024, which is likely a result of the warmer weather combined with increased industry vigilance. Jessica reminds those in the industry to continue to stay mindful about biosecurity to help reduce PED and PDCoV cases.

SHO continues to support elimination as the best strategy for disease control. Practitioners are encouraged to continue to be diligent in testing for coronaviruses in all gastrointestinal cases, as PDCoV can present with minimal clinical signs. Timely diagnosis of these cases can help limit widespread contamination and potential spread to other sites.

Practitioners are also encouraged to promote the use of SHARC by producers to stay aware of current positive sites in their proximity. Please refer any producers interested in enrollment to Jessica Fox Jessica.fox@swinehealthontario.ca. The PED and PDCoV Tracking map is available on the Swine Health Ontario website and shows current and annual cases by county. http://www.swinehealthontario.ca/Disease-Information/PED-PDCoV-Tracking-Map

OAHN Veterinary Clinical Impression Survey Veterinary Comments

Dr. Andrea Patterson provided an overview of the practitioner survey for Q2 2025. There has been excellent participation over the past few quarters, and there were 15 respondents this quarter!

All multisystemic diseases were reported to be stable this quarter. Dr. Patterson commented that there has been a shift in reported circovirus (PCV) prevalence. For the past two years it has been considered “common”, whereas prior to this both PCV2 and PCV3 were consistently reported as “rare”. In terms of respiratory disease, both PRRS and Influenza (IAV) were reported by practitioners to be stable or decreased prevalence for Q2 2025. This would be seasonally low IAV prevalence compared to previous quarters but may be attributed to improved control because of widespread vaccination. One practitioner reported having a case of tracheitis this quarter.

For gastrointestinal diseases, the porcine coronaviruses (PED, PDCoV) were reported to be of increased prevalence in Q2 2025, which has been the case for the past couple of quarters and is confirmed by SHO’s active case counts. One practitioner commented that the main biosecurity link found in some of these positive cases was the presence of contractors in these barns during renovations. From the survey respondants, 33% of practitioners felt that there was an increase in Rotavirus in Q2 2025, which Dr. Andrea speculates may be a result of increased testing due to ongoing coronavirus pressure in Ontario and the increased scour diagnostics that would accompany this. Additionally, 28% felt there was an increase in Salmonella this quarter, which was reflected in the high prevalence of positive cases seen in May 2025 reported by Dr. Bukunmi Odebunmi from OMAFA. A practitioner also commented that they saw an increase in Salmonella cases in both nursery and finishers this quarter. In terms of additional comments, one practitioner reported having a case of Vitamin D toxicosis during this quarter.

Animal Health Laboratory Immediately Notifiable Disease Review

Dr. Bukunmi Odebunmi from OMAFA provided a summary of the Influenza and Salmonella cases received by the AHL during Q2 of 2025.

Influenza A (IAV)

There were 31 positive case submissions for Influenza A in Q2 of 2025. This is higher compared to Q2 of 2024 but reduced from Q2 in 2023 where there were 48 positive submissions. Over half of the positive detections in Q2 2025 were H3N2, and there was one mixed isolation (H3N2 and H1N1 detected in the same sample). Most cases this quarter were from the grow-finish stage. The majority of sequenced submissions in Q2 2025 were of the H3N2 2010.1 clade, which is consistent with the previous quarter. All H1N1 and H1N2 submissions this quarter were of the alpha clade.

Salmonella

During Q2 of 2025, the total positive submissions this quarter was lower than Q2 of 2024 but increased compared to Q1 2025. Most positive submissions this quarter were submitted in the month of May, where about half of these cases were cultured 3+ or 4+. Of all positive cases this quarter, most submissions were isolated from enrichment (IFE). More than half of the submissions in Q2 2025 reported corresponding GI clinical signs. A total of 32% of submissions did not have any GI clinical signs reported in the history.

Most of the positive submissions this quarter were from nursery pigs. The monophasic S. Typhimurium serotype was the most commonly isolated serotype in Q2 2025 in both IFE and non-IFE detections, which is consistent with last quarter and Q2 of 2024.

Laboratory Diagnostic Reports

Animal Health Laboratory (AHL)

Dr. Josepha DeLay from Animal Health Lab provided an update on cases received by the lab during Q2 2025. A total of 1,320 swine cases were submitted to the AHL this quarter. Of these, 73 cases had a pathology component. A good or adequate clinical history was included for (96%) of this quarter’s pathology cases. Age group and premises ID (PID) inclusion rates for Q2 were excellent at 96% and 99%, respectively.  

Cases and pathogens of interest during 2025 Q2 are as follows:

• Influenza case numbers in 2025 Q2 (49 cases) were lower than in the previous 2 quarters (2025 Q1: 68 cases, 2024 Q4: 67 cases) but remain higher than the same quarter in 2024 (21 cases). H3N2 was the dominant subtype in Q2 (59%), with fewer cases involving H1N1 (24%) and H1N2 (17%) subtypes. PRRSV was detected by PCR in 159 cases (132 diagnostic, 27 monitoring), down from 172 positive cases in 2025 Q1 and 196 cases in 2024 Q2. How does this compare to previous quarters? Sow barns are typically <15% of positive submissions (using PCR). This hasn’t changed in the past three quarters (Q4 = 8.3%, Q1 = 12%, Q3 = 10.6%) nor has the percent positivity for sow barns or other age groups. When looking at the data by month, there is a higher case count in sow barns in May (6 vs. 2 in the previous May) with an increased percent positivity (16.2% vs. 7.1%) indicating this change was not due to increased testing. This trend is not present in the other age groups or for other months. Reminder to vets that this information is also displayed on the IAPD dashboards: https://iapd.lsd.uoguelph.ca/
• Actinobacillus suis was isolated from 4 cases during Q2, compared with no cases in 2025 Q1 and 1 case in 2024 Q2. Streptococcus suis was isolated from fewer cases in Q2 (12) than in Q1 (24 cases), but in similar numbers to 2024 Q2 (17 cases).
• Pathogenic Brachyspira spp were not identified in any cases in 2025 Q2.
• More frequent requests for genotyping of E.coli isolates is identifying a broader range of bacterial subtypes. F18-positive isolates were identified in an increased number of cases (18), although only 1 of these isolates (from nursery pigs) also carried the Stx2e toxin gene seen in edema disease. Enteropathogenic E.coli (EPEC) was identified in 1 case, also in nursery pigs.
• The number of Lawsonia intracellularis-positive cases remains at approximately 50% of that in 2024, with positive case numbers similar to those in 2023.
• PCV2 was genotyped from 4 PCR-positive cases, and all were typed as PCV2d.
• Porcine Sapovirus was detected in 16 cases, similar to positive case numbers in 2025 Q1 and 2024 Q2.
• Senecavirus A (SVA) was detected in an environmental sample from 1 case. No clinically affected animals were reported in association with this case.
• Congenital tremors were identified clinically in a sow herd (mainly gilt litters), and histologic lesions in affected piglets supported (but did not confirm) involvement of atypical porcine Pestivirus. Further PCR testing for the virus was not pursued.
• Mycobacterial lymphadenitis was identified in lymph nodes from head condemnations at slaughter. No further testing was carried out due to lack of appropriate tissue samples for the required testing.

Gallant Custom Laboratory (CEVA) Diagnostic Reports

Anna Pietruszkiewicz and Kevin Millsap did not have anything to report from cases submitted to Gallant Labs (CEVA) from Ontario in Q2 2025.

Ontario Slaughter Statistics

Dr. Jordan Buchan provided a summary of federal and provincial slaughter condemnation reports for Q2 of 2025 on behalf of Dr. Christine Pelland.

Federal Slaughter Statistic Summary (Q2 Aggregate)

In total, there were 56,972 fewer animals slaughtered in Q2 2025 compared to Q1 2025, with 77 fewer condemnations. This quarter there was a reduction in condemns due to enteritis (-2.7%), erysipelas (-1.7%), and icterus/jaundice (-1.5%). There was an increase in condemns due to abscesses (+3.3%), anemia (+0.7%), and arthritis (+0.5%). This quarter saw 4,703 fewer hogs with trims compared to last quarter. There was a reduction in trims resulting from “other”, abscess, arthritis, and fractures, and an increase in trims resulting from mammary tissue. Trim weights were stable or reduced for all other categories in Q2 compared to Q1 of 2025.

Provincial Slaughter Statistic Summary

There was an increase in total number of hogs slaughtered in Q2 of 2025 compared to last quarter, with an increase in around 8,000 hogs. This corresponded to a 4% increase in condemnations for the quarter, compared to a 3.3% condemnation rate last quarter (Q1 2025). The majority of condemnations this quarter were attributed to parasitic livers (52.2%), which is consistent with Q1 and Q3 of last year. This quarter there was a reduction in condemnations resulting from inflammatory conditions, abscesses (12.6%, down from 15.4% in Q1), and a 3.2% reduction in condemnations categorized as “Other”. Compared to Q1, there were 189 more whole carcass condemns, and 791 more partial carcass condemns in Q2.

CanSpotASF Surveillance Update

Dr. Christa Arsenault provided an update on the CanSpotASF surveillance submissions. Ontario samples submitted for CanSpotASF testing in 2025 Q2 included:

• Laboratory samples submitted by vets/pathologists: 18
• Provincial Abattoirs: 3
• Federal ON Abattoirs: 40
• Invasive Wild Pigs: 0

All samples tested under the CanSpotASF surveillance program have yielded negative ASF results.

OAHN Projects- Now Accepting Samples!

Dr. Josepha DeLay and Dr. Christa Arsenault provided an overall OAHN swine projects update. Reminder project #1 on PCV-2 and project #2 on Sapovirus are both now open and accepting samples!  Please consider both when completing herd visits and or performing PM exams.

Project #1- The first project aims to assess Porcine Circovirus type 2 (PCV2) prevalence in the Ontario herd, specifically the different PCV2 subtypes. PCV2 PCR-positive samples submitted to AHL are eligible, and this project will sequence these samples to determine subtype. These results will allow for better understanding of the distribution of different PCV2 subtypes within the province. A short survey will accompany these submissions to better understand clinical picture of each case.

Project #2- The second project will focus on the neonatal diarrhea complex and the role of Sapovirus in these cases. Eligible cases will be those with piglets less than 20d of age presenting with a clinical scour and an accompanying Sapovirus PCR-positive result. This project will evaluate these cases by testing for a wide range of pathogens, including: porcine bacteriology enteric panel, Rotavirus PCR, Sapovirus PCR, Coronavirus triplex PCR, fecal flotation, and histopathology. This project aims to allow for better understanding of how Sapovirus contributes to neonatal diarrhea cases, especially amongst other common pathogens.

A detailed summary was sent to all OASV members in July 2025 via email  Any questions can be directed to Dr. Christa Arsenault.

International Disease Topics Of Interest Summary

Dr. Conor Voth has taken over the International Disease Topic of Interest summary for the OAHN Swine Network as Dr. Al Scorgie has made the difficult decision to leave the OAHN Swine Network after 10 years of contributions.  We would like to wish Dr. Scorgie well in his future endeavours and thank him for his contributions to OAHN over the past decade!  We would also like to welcome Dr. Voth to the OAHN Swine Network! 

Dr. Voth reported on some interesting international and domestic disease surveillance reports and new research:

Foot and Mouth Disease (FMD)

South Africa: As of July 31, 2025, South Africa reported 368 new foot and mouth disease (FMD) cases across KwaZulu-Natal, Gauteng, North West, Free State, and Mpumalanga, affecting 59,686 cattle. There are now 236 active outbreaks, up from 183 last month. Since June 2021, FMD serotypes SAT1, SAT2, and SAT3 have caused over 5,200 cases, impacting cattle, sheep, and African buffalo. KwaZulu-Natal remains heavily affected. The persistence of multiple serotypes complicates control efforts, prompting intensified vaccination, surveillance, and quarantine measures. Source: (SHIC Swine Disease Global Surveillance Report, July 2025)

Russia: On May 29, 2025, the World Organisation of Animal Health (WOAH) officially recognized all of Russia as FMD free, granting the final zone “Western Siberia – Urals” FMD-free status with vaccination. This designation enables safe livestock trade and reflects full disease control across Russia, supporting global epizootic stability. Source: (Pig333)

African Swine Fever (ASF)

Germany: On June 14, 2025, the Friedrich Loeffler Institute (FLI) confirmed African swine fever (ASF) in a wild boar found in North Rhine-Westphalia. Genomic analysis revealed that the new North Rhine-Westphalian variant is distinct from previous German strains but closely related to ASF viruses found in Calabria, Italy, first detected in May 2023. The outbreak zone in North Rhine-Westphalia is just 93 miles from Belgium and the Netherlands. Source: (PigWorld, SHIC Swine Disease Global Surveillance Report, July 2025)

Europe: On July 11, 2025, European countries reported 154 outbreaks in domestic pigs, Estonia confirmed its first on-farm outbreak since July 2023, and 16 European countries reported 556 outbreaks in wild boar. In the first half of 2025 Europe recorded an increase in ASF cases in wild boars, with 6892 cases, nearly matching the total for all of 2024 and double the number from the same period last year. Domestic pig cases remain stable. (SHIC Swine Disease Global Surveillance Report, July 2025)

Asia: In June, five countries, India, Sri Lanka, Vietnam, South Korea, and Malaysia, reported new outbreaks of ASF in domestic pigs, and Sri Lanka reported that their outbreak also affected the wild boar population. Vietnam police dissolved a ring selling ASF-affected pork to Hanoi markets and restaurants. The ring used illegal slaughterhouses in North Vietnam to slaughter diseased pigs and sell the pork mixed with pork from healthy pigs to markets and small eateries. Source: (SHIC Swine Disease Global Surveillance Report, July 2025)

Can American Veterinarians and Labs Keep Up with an ASF Outbreak?

This study developed a model simulating ASFV spread over 150 days in a densely populated U.S. swine-producing state to estimate the sampling resources needed for outbreak management. The model predicted a median of 27 outbreaks, requiring over 3,000 barns sampled and up to 84,830 blood samples or 14,195 oral fluid samples collected, depending on the sample type. To prevent sampling delays, between 136 and 367 sample collectors would be needed under median epidemic conditions, but this could rise to over 3,000 in worst-case scenarios.

The study highlighted that sample collector availability is affected by downtime—periods when collectors cannot visit farms due to biosecurity restrictions—which increased the number needed by 28% to 75%. Switching from blood samples to oral fluids reduced collector requirements by up to 75%. Laboratory capacity also emerged as a bottleneck; with a daily processing limit of 1,000 samples, backlog could delay results for months or even years. Redistribution of samples to other labs would be necessary to avoid such delays.

The study emphasizes that current U.S. ASFV response plans, which rely heavily on swine veterinarians for sampling, may be insufficient in a large outbreak. To address this, a certified training program for on-farm personnel aims to increase the pool of qualified sample collectors. These findings inform strategic planning by identifying the scale of manpower and lab resources needed for effective ASFV surveillance and control. The model underscores the importance of flexible, scalable response systems to manage potential ASFV incursions, helping safeguard the U.S. swine industry’s health and economic stability. Source: (Galvis, AJ. A., Estimating sampling and laboratory capacity for a simulated African swine fever outbreak in the United States, Preventive Veterinary Medicine, 239)

New World Screwworm

The New World Screwworm (NWS), a parasitic fly that infests livestock wounds, was largely eradicated from the U.S. and Mexico by the 1980s through a massive sterile insect release program. However, NWS was recently detected again in southern Mexico in late 2024, threatening to re-enter the U.S. This parasite causes severe economic losses, with historical infestations in Texas alone estimated to cost the equivalent of $732 million today.

NWS larvae feed on warm-blooded animals’ flesh, damaging cattle, pigs, and even humans. The parasite thrives in southern climates and poses a particular risk to southern U.S. producers, especially with high feral swine populations acting as potential carriers. Although commercial pigs are mostly indoors, outdoor small-scale operations and show pigs remain vulnerable.

The USDA has responded by suspending imports of live cattle and other livestock from Mexico and plans to enhance sterile fly production capacity. A new sterile fly factory is expected in southern Mexico by 2026, alongside a Texas distribution center to support rapid response.

Producers should monitor animals closely for wounds that fail to heal, visible larvae, foul odors, or behavioral signs like irritability or inappetence. Suspected cases require immediate veterinary attention, quarantine, and larvicide treatment.

The reappearance of NWS may lead to trade restrictions on U.S. pork exports from countries free of the parasite, including major markets like Japan, China, and South Korea. Producers are encouraged to join programs like the Swine Health Improvement Plan or Secure Pork Supply Plan, which provide guidance on biosecurity and outbreak preparedness to help safeguard operations and maintain market access. Source: (Preparing to deal with New World screwworm: The next generation – Clayton Johnson, National Hog Farmer)

Mexico has recently reported 35 human infections, while Costa Rica has seen 56. An 86-year-old woman in Mexico is the first confirmed death associated new world screwworm, as a result of the infection compounding with skin cancer. In Mexico illegal cattle smuggling has been linked to the spread. Source: (2025-08-03 – CEZD Weekly Intelligence Report)

Porcine Respiratory and Reproductive Syndrome Virus (PRRS)

Is PRRSV 1C.5 more airborne than other variants?

The rapid emergence and spread of the porcine reproductive and respiratory syndrome virus (PRRSV) variant 1C.5 (L1C 1-4-4) raised concerns about whether this variant was more transmissible via aerosols compared to other endemic PRRSV strains. Researchers from the University of Minnesota, North Carolina State University, USDA ARS, and Mechanical Engineering collaborated to evaluate differences in aerosol stability, particle size, viral load, and airborne viability among several clinically relevant PRRSV variants, including VR2332 (L5), MN30100 (L9A), L1C.5 1-4-4, L1A 1-7-4, L1F 1-8-4, and Lelystad virus.

Using a rotating drum aerosol system, the team measured decay of viral RNA and viable virus over 120 minutes. They found distinct decay patterns among variants. MN-30100 (L9A) maintained the highest viability across all time points and a broad range of particle sizes (<4.7 μm), while L1C.5 1-4-4 showed viability only immediately after aerosolization and minimally later. This challenges the assumption that more virulent variants have higher aerosol stability.

Further, experimentally infected weaning pigs were used to compare clinical impact, viral shedding, and airborne detection of L1C.5 1-4-4, L1A 1-7-4, and MN-30100 (L9A). Pigs infected with L1C.5 1-4-4 and L1A 1-7-4 showed severe clinical signs including respiratory distress and fever, while MN-30100 induced milder disease. Viremia was highest and most sustained for L1A 1-7-4, with L1C.5 1-4-4 showing strong early viral loads that declined after 15 days. Nasal shedding patterns followed similar trends.

All three variants were detectable in air samples, with L1A 1-7-4 producing the highest and most sustained airborne viral loads. L1C.5 1-4-4’s airborne presence declined after 13 days post-infection. Most airborne virus was found in particles larger than 9 μm.

These findings indicate that airborne transmissibility varies by PRRSV variant and correlates partly with pathogenicity and nasal viral shedding. Considering the low infectious dose of L1C.5 1-4-4, even small amounts of aerosolized virus can lead to infection and spread. The study highlights the need to review and potentially adapt biosecurity measures—such as air filtration—to account for dose-dependent transmission risk posed by emerging variants. Source: (National Hog Farmer)

Astrovirus-4

Confirmation of Astrovirus-4 as a Primary Cause of Tracheitis and Bronchitis in Piglets

A recent study conducted by teams from North Carolina State University, USDA ARS, Iowa State University, and UC Santa Cruz demonstrated that porcine astrovirus 4 (PoAstV4) can directly cause respiratory disease in piglets.

Using caesarean-derived colostrum-deprived piglets experimentally infected with PoAstV4, the researchers observed consistent tracheitis and bronchitis lesions, with the virus detected in respiratory epithelial cells via in situ hybridization. Infected piglets shed PoAstV4 in nasal secretions from two days post-challenge, peaking early and ceasing by day 14, and also shed virus fecally, suggesting possible gastrointestinal involvement. The immune response was robust, with both IgM and IgG antibodies detected and significant lymphocyte infiltration in respiratory tissues.

This study is the first to confirm PoAstV4 as a primary epitheliotropic respiratory pathogen in swine, supporting its role in respiratory disease, especially in cases negative for other common viruses like influenza A virus (IAV). While the experimental lesions were milder than some field cases—likely due to controlled conditions and dose—the findings highlight PoAstV4 as an important differential diagnosis for respiratory signs in young pigs. Source: (SHIC, 2025)

How can you Participate in OAHN?

Look for the 2025 Q3 veterinary clinical impression survey that will come out the first week of Oct via an email through the OASV listserv.

If you are a practicing vet that sees swine in Ontario, please complete this survey when the email reminders are sent out through the OASV listserv.