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

3 New OAHN Swine Projects

The OAHN swine network recently received approvals for three research projects. The network is very excited to get these projects underway and to contribute meaningful findings to the industry. Dr. Christa Arsenault provided the group with an overview of all three projects and their objectives.

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.

Project #3- The final project will assess the current parasitic burden on Ontario Swine farms. Both provincial and federal abattoirs have reported a high frequency of parasitic livers (attributed to ascarids), and this project will strive to better understand this recent increase. Pen-based fecal samples from sows and finishing pigs will be collected and submitted for fecal flotation, and a brief survey will collect information on current deworming practices in enrolled herds. This will quantify the load of parasites on farms, as well as the deworming protocols currently being used in the field, to give more context to these high condemnations.

More information will be provided to Ontario swine veterinarians on the details of these projects including an overview of all project requirements at the OASV AGM meeting planned for the evening of June 19, 2025, after the Ontario Pork Congress in Stratford.  For those that cannot attend this meeting in person project summaries will be disseminated to all OASV members through the email listserv.  Any questions can be directed to Dr. Christa Arsenault

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 Q1 of 2025. Jessica reported that this quarter has been the worst quarter seen since 2014, with 20 reported PED cases and 18 reported PDCoV cases. Most of these cases occurred in January (at the start of the quarter). As part of SHO’s ongoing goal to spread awareness to reduce transmission of these viruses, SHO leadership team members have been meeting with various industry sectors to discuss the importance of ongoing biosecurity, including pork producers, feed companies, transporters, and packing plants. At the start of Q2, SHO sent out a memo to remind industry members of the risks of PED/PDCoV movement associated with manure spreading. Jessica reported that 21 previously detected cases resumed negative PED/PDCoV status in Q1.  SHO’s reporting website is constantly being updated. Moving forward, SHO continues to urge industry stakeholders to remain as vigilant as possible in the face of these viruses, as new detections continue to be reported in Q2.

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 Q1 2025, which had a very high level of participation with a total of 14 respondents.

Of note, 50-60% of respondents noted an increase in PED and PDCoV cases this quarter, which is consistent with reports from SHO describing this quarter as especially challenging. 13% of practitioners felt there was an increase in hemorrhagic bowel disease this quarter, which is a notable increase compared to the last quarter. 33% also felt there was an increase in Rotavirus prevalence in Q1 of 2025. Dr. Patterson suggests that these perceived increases in gastrointestinal diseases could potentially be a result of increased surveillance and diagnostics in response to the uptick in PED/PDCoV cases this quarter.

During this quarter, practitioners also noted an increase in PCV2 cases, with additional comments describing challenges with PCV2 type D specifically. This increase has been consistent over the past couple of quarters, and the results from this survey indicate that it remains a relevant challenge. In terms of respiratory diseases, 40-50% of practitioners responding to the survey noted an increase in PRRS and influenza. Multiple practitioners made comments this quarter in regards to seeing edema disease challenges. One practitioner noted an irregular presentation where respiratory signs were the only clinical signs present.

Animal Health Laboratory Immediately Notifiable Disease Review

Dr. Hannah Golightly from OMAFA provided a summary on Salmonella submissions received by the AHL during Q1 of 2025.

Salmonella

During Q1 of 2025, there was a decreasing trend of Salmonella detections from month to month across the quarter. This trend was similar in Q1 of 2024. Overall, there were less positive submissions each month this quarter, and more of those detections came from cultures that were not isolated from enrichment (IFE). Half of the positive Salmonella submissions this quarter reported a history of gastrointestinal clinical signs. In terms of serotypes, the monophasic Salmonella Typhimurium continues to be the most commonly isolated serotype, both for IFE and non-IFE submissions. The majority of Salmonella-positive submissions were from nursery pig samples.

Laboratory Diagnostic Reports

Dr. Josepha DeLay from Animal Health Lab provided an update on cases received by the lab during Q1 2025. A total of 1,395 swine cases were submitted to the AHL this quarter. Of these, 81 cases had a pathology component. A good or adequate clinical history was included for (98%) of this quarter’s pathology cases. Age group and PID inclusion rates for Q1 were also 98%, which was appreciated.

Cases and pathogens of interest during 2025 Q1 are as follows:

• Influenza case numbers in 2025 Q1 (68 cases) remained similar to the increased number in the previous quarter (2024 Q4: 67 cases), but much higher than the same quarter in 2024 (17 cases). The subtype distribution in 2025 Q1 was approximately equal among H1N1, H3N2, and H1N2 viruses, which differs from H3N2 dominance in other recent quarters.
• Of the 18 PCV2 PCR-positive cases in 2025 Q1, genotyping was requested for 5 cases. PCV2 type D was detected in 3/5 cases, and PCV2 type B was detected in 1/5 cases. Results were inclusive in 1 case.
• Actinobacillus pleuropneumoniae was isolated in 1 case during this quarter. No information was provided regarding the clinical scenario or age group affected.
• Brachyspira hyodysenteriae was detected by PCR in a rectal swab from 1 group of grower / finisher pigs with mucohemorrhagic diarrhea.
• Porcine astrovirus 4 (PoAstV4) was detected by PCR in lung samples from nursery pigs with bacterial pneumonia and concurrent mild necrotizing bronchiolitis. The viral load was very low (Ct 28.5-31.2) and the clinical significance of PoAstV4 detection is unclear in this case. Influenza A virus, PHEV, and porcine parainfluenza virus 1 were not detected by PCR in lung samples from this group.

Gallant Custom Laboratory (CEVA) Diagnostic Reports

Anna Pietruszkiewicz and Kevin Millsap reported on 3 cases submitted to Gallant Labs (CEVA) from Ontario in Q1 2025 in Ontario. These were all influenza (IAV) cases and were isolated and identified as H1N2.

Ontario Slaughter Statistics

Dr. Christine Pelland provided a summary of federal and provincial slaughter condemnation reports for Q1 of 2025.

Federal Slaughter Statistic Summary (Q4 Aggregate)

In Q1 2025, compared to last quarter (Q4 2024) there were 32,289 more hogs slaughtered, with 500 fewer total condemnations. Compared to last quarter, there was a reduction in condemns as a result of abscesses, peritonitis, enteritis, icterus/jaundice, and erysipelas. However, there was an increase in condemns due to moribund and septicemia. This quarter there was a reduction in trims in mammary tissue and skin diseases, but increased trims in the “other” category, abscess, and arthritis. It was noted that provincial plants are currently trying to decrease the number of condemnations in the “other” category, in hopes that this will allow for better understanding of these condemns moving forward.

Provincial Slaughter Statistic Summary

Only condemnation data from January and February were provided for this quarter. Of this data, there were more total condemns in January compared to those in February. The top 5 most common condemns in provincial abattoirs this quarter were as follows: parasitic liver, inflammatory condition, abscess, arthritis, and “other”.

CanSpotASF Surveillance Update

Dr. Christa Arsenault provided an update on the CanSpotASF surveillance submissions. Ontario samples submitted for CanSpotASF testing in 2025 Q1 included:

• Laboratory samples submitted by vets/pathologists: 24
• Provincial Abattoirs: 17
• Federal ON Abattoirs: 31
• Invasive Wild Pigs: 1

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

OAHN Project Update- Porcine Hemagglutinating and Encephalomyelitis Virus (PHEV)

Dr. Josepha DeLay provided an overall project summary on the porcine hemagglutinating and encephalomyelitis virus (PHEV) project within Ontario swine herds. PHEV is a virus that has been implicated as a respiratory pathogen, specifically in severe hemorrhagic tracheitis cases. Although not common, when it causes disease, it is typically very severe in the grow-finish stage of production. The pathogenesis is not entirely known, but ultimately severe inflammatory exudate ends up occluding the trachea, which causes airflow into the respiratory tract to become turbulent, resulting in even further respiratory damage. Case reports out of Iowa have implicated PHEV and PoAst4 in respiratory disease, specifically for targeting large airways (trachea and bronchi).

For this project, samples were tested from swine submission cases that included fresh lung and/or trachea, and that also submitted sections for histopathology (so histologic lesions could be visualized). PHEV PCR-positive cases were then sent for PHEV in situ hybridization (ISH) at Iowa State in order to visualize the viral nucleic acids associated with the lesions. This project ran for a year (April 2024 to 2025), with 5 participating clinics and 136 total cases. The majority of cases were from nursery and grow-finish pigs. Overall, there were not many positive cases, and Ct values were generally very high, indicating very low viral load. Additionally, the histologic lesions did not seem to correlate well with Ct values or PHEV PCR positivity. This was the case for ISH results as well, as many PHEV PCR-positive cases were ISH negative. In conclusion, PHEV is present in low prevalence in growing pigs in Ontario and can be identified in trachea and/or lung. It will colonize these tissues, but not necessarily cause disease. More cases are needed to be able to definitively conclude its role, but it may be involved in the porcine respiratory disease complex, in addition to other pathogens such as influenza.

International Disease Topics Of Interest Summary

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

Foot and Mouth Disease (FMD)

Germany: In mid-March, Germany was declared free of FMD after there were no further FMD outbreaks and no FMD detected in the surveillance and control zones, after the initial outbreak of FMD reported in a small herd of water buffalo, (14 animals), on January 10th, 2025.  This herd was located near Berlin in an area with few farms which made control easier. The source of the FMDV is unknown. One of the challenges in Germany at this time is the outbreak Bluetongue virus. Bluetongue virus can cause lesions that are similar to the lesions caused by FMD. Germany has reported over 15,000 cases of Bluetongue since May 2024. Source: (Pig333.com, March 17th,2025)

Hungary: On March 06th, 2025, Hungary confirmed a case of FMD on a cattle farm, with 1600 cattle. The farm started showing clinical signs on March 03rd, 2025. By mid-April, Hungary had confirmed a total of 5 cases of FMD. Cases are detected in the same county that has previously had four FMD outbreaks. The strain of FMDV in Hungary is different from the strain of FMDV that was detected in Germany and there is no link to the FMD outbreak in Germany. The affected farm in Germany was 765 kms from the affected farms in Hungary. Hungary has not had FMD for over 50 years. Source: (CEZD Weekly Intelligence Report April 14th -20th 2025 and Pig333.com, March 17th,2025)

Slovakia: On March 20th, 2025, Slovakia reported an outbreak of FMD on 3 cattle farms in the district of Trnavsky in southwest part of the country. A fourth outbreak on a cattle farm in the same area was reported on March 24th. The farms are located within 10 kms of the border with Hungary and 35 kms from the first reported outbreak of FMD reported in Hungary. Germany has sent 10,000 doses of FMD vaccine to Slovakia. Source: (Pig Progress)

UK: Authorities in the UK realized that although a ban on the import of meat and meat byproducts from Germany had been put in place, these products were still entering the country. A gap was identified where trucks entering the country cross the border first and then enter a custom inspection station. Some trucks were not entering the station.

Porcine Respiratory and Reproductive Syndrome (PRRS)

Genotyping of PRRSV at the Animal Health Lab (AHL): In the past, genetic characterization of PRRSV type 2 was done through open reading frame 5, (ORF 5). An RFLP, restriction fragment length polymorphism analysis was done on ORF 5. There has been a refinement of PRRSV lineage-based classification which subdivides PRRSV into 11 lineages, (L1-L11) and 21 sub-lineages based on the ORF 5 sequences. Recently, AHL analyzed 1,777 PRRSV from samples from 2015-2024. There were 6 lineages identified: L1, L2, L4, L5, L7 and L8). L1 was the most common lineage found, 80.08% of the samples and L5 with 17.73% of the samples. The next most common lineage was L8 with 1.69% of the samples. L2, L4 and l7 were infrequent. Lineages L3, L6, L9, L10 and L11 were not detected.  There were 9 sub-lineages found: L1B, L1C, L1D, L1E, L1F, L1H, L5A, L8A and L8C however 525 sequences of the L1 lineage could not be definitively classified.

Some of the RFLP patterns such as 2-5-2 were all in the L5A sub-lineage and 1-8-4 was all in the L1H sub-lineage but other RFLPs such as 1-1-1 was in 4 sub-lineages and 1-1-2 was in 5 sub-lineages. Source: (Davor Ojkic, AHL Newsletter 2025;29(1):18).

Can PRRSV percolate through soil into groundwater?: A group at the University of Minnesota recently completed a study to determine if PRRSV could percolate through soil. The study was done because in the fall when PRRS breaks usually increase there is manure spreading. Could PRRSV enter the groundwater and be a risk to farms? The researchers used 3 different PRRS strains: L1A 1-7-4, L1C.5 1-4-4, L1G 1-26-2. Thirteen different soil types from Minnesota were tested. Also, the viruses were percolated through different amounts of soil. The researchers found that the different strains of PRRSV could percolate through the soil although there were differences among the strains on how much soil the PRRSV could percolate through. For example, the L1G 1-26-2 strain was able to percolate through more of the samples. Also, all the strains could percolate through all the soil types. The researchers commented that this is an initial study, and further work needs to be done. The amount of soil the viruses were run through was small. There could be virus dilution, in the field there could be multiple layers of soil layers and further study has to be done on infecting pigs with contaminated groundwater. Source: (Joaquin et al. Comparative Adsorption of Porcine Reproductive and Respiratory Syndrome Virus Strains to Minnesota Soils, Viruses 2025, 17, 58).

Korea: Researchers at the Chung-Ang University have been studying how PRRSV affects the immune mechanism in the lungs of pigs infected with PRRS. Jun-Mo Kim and his team analyzed protein-coding RNA transcripts from single cells and fluid from the lungs of PRRS infected pigs. The pigs were infected with PRRS strains of different virulence. The study found that high virulence strains of PRRS caused early, severe lung damage and a change in the immune balance due to a significant decrease in macrophages. While PRRS strains of intermediate virulence had delayed lung damage and fewer alterations in the immune balance. The researchers also noted that there were more M2-like protective anti-inflammatory macrophages in the lungs of pigs infected with the intermediate virulent PRRS strains. Although fewer than 5% of macrophages are infected by PRRS the researchers concluded that PRRS infected cells from the lungs of pigs infected with the high virulent strains, released micro-RNAs that caused cell death in “bystander” cells. Dr. Kim hopes the results of the study will lead to therapeutic strategies that can mitigate the severe lung damage. Source: (Jennifer Shike, Pork, February 24th,2025).

Highly Pathogenic Avian Influenza (HPAI):

USDA: The USDA confirmed cases of HPAI 2.3.4. 4b genotype D1.1 in lactating dairy cattle in Navada and Arizona in January and February this year, respectively, through silo samples collected under the National Milk Testing Strategy.  Until these detections, all previous cattle isolations in the U.S. were of the B3.13 genotype.  Whole genome sequencing supports the D1.1 detections in Navada and Arizona resulted from separate wild bird to cattle spillover events, with three independent spillovers identified to date. Sources: Nevada link, Arizona link

Avian Influenza Vaccine

The USDA has given conditional approval for a killed avian influenza vaccine made by Zoetis. A conditional license means the vaccine can be used for a finite period and to meet an emergency condition or other special circumstances. Zoetis first started working on HPAI vaccines when there was an outbreak in Southeast Asia in 2001-2002. When the new strain of HPAI was identified in the US in 2022, Zoetis began to update the previous avian influenza vaccine. From 2022 more than 100 million birds have been infected with HPAI in the US. A number of organizations including the National Turkey Federation, United Egg Producers, International Dairy Foods Association and National Milk Producers Federation support the development of HPAI vaccines for use in dairy cows, turkeys and egg-laying hens.  There are some organizations such as the Congressional and Senate Chicken Caucuses and the National Chicken Council that are concerned the U.S. will lose export markets as most US trading partners do not recognize countries as free from HPAI that vaccinate. Source: (Elzabeth Doughman, Watt Poultry, February 15th,2025).

PED and PDCoV

Categorization of PED and PDCoV PCR Detections: SDRS, (Swine Disease Reporting System), has added a new category for PEDV and PDCoV PCR detections. The new category is facilities. The facility category includes samples taken from: truck washes, vehicles and processing plants. The other categories are adult/sow and wean-to-market. In February for PEDV the positivity rate of facility testing was 8.59%, (11 of 128 samples were positive), a decrease from January positivity rate of 23.84%, (36 of 151 samples were positive).  For PDCoV the positivity rate was 5.47% vs a January positivity rate of 11.26%. For adult/sow the positivity rate for PEDV was 7.39% and 2.02% for PDCoV in February similar to the January rate. For wean-to-market the positivity rate for PEDV was 13.22% and for PDCoV the positivity rate was 7.68% for February similar to the January rate. Source: (SDRS Report #85 (March 04, 2024).

PED Transmission- Nasal to Intestinal Mucosa: Dr. Sue Burlatschenko brought this article to OAHN this quarter to discuss an alternative route of PED transmission.

This paper discusses the nasal mucosa as a “gateway for pathogens” into the GI tract via the intranasal route. In swine, dendritic cells are distributed in the nasal mucosa, where they capture antigens and migrate to the lymph nodes to present them to T cells. Interestingly enough, these submucosal dendritic cells can evade antiviral immune responses at the epithelial barrier, allowing these viruses to be disseminated in the submucosa through increased cells, and then go to lymph nodes, and further transfer to T lymphocytes. This study reports that dendritic cells show a certain susceptibility to PED virus, and following the above pathway, allow PED-infected T cells to migrate to the small intestine to then cause disease. Two groups of pigs were infected with PED – one intranasally and one orally. The orally-infected pigs developed traditional clinical signs within 46hr. The intranasally-infected pigs developed clinical signs in about 60hr, including the associated pathology (IFA positive in their small intestines), and PED virus was identified within T cells 24hr post-inoculation. This study shows that aerosolized PED virus can effectively infect pigs via the intranasal route. Source: (Nature Communications, Y Li et al, Sept 19, 2018.

How can you Participate in OAHN?

Look for the 2025 Q2 veterinary clinical impression survey that will come out the first week of July 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.