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

Novel Influenza A- H3N2 Cluster 2010.1 Update

On the 2023 Q vet survey, there were 93 % of practitioners ranking the frequency for IAV as common (43%) or very common (50%). There were 62% of practitioners that indicated that IAV activity was increased when compared to the previous quarter.

Dr. Hannah Golightly (OMAFRA) commented that the number of positive IAV submissions has been relatively stable over the last three Q4 periods. In Q4 2023, H3N2 detections were appreciably greater than any other subtype combined for each month of the quarter. This is a trend that has been ongoing since May 2023, and is markedly different than the last 2 years, where H3N2 detections only accounted for 20% and 28% of all positive cases in Q4 of 2021 and 2022, respectively. The majority of H3N2 detections in Q4 2023 were cluster 2010.1, most of which were detected in grow-finish herds.

Figure 1. Submissions positive for influenza (not including ELISA tests) in swine by subtype and submission month, Ontario, October 2021 to December 2023.
Most positive submissions in Q4 2023 (October-December) involve subtype H3N2. Figure 1 also shows counts of partial, mixed and inconclusive subtypes isolated from Ontario swine herds.
(see legend above graph).

Salmonella Surveillance

Dr. Golightly reported that the number of Salmonella positive submissions in this quarter comparable to last year, with 24 positive submissions in Q4 2022 and 23 positives in Q4 2023. When considering culture level, just over half of the detections in Q4 2023 were isolated from enrichment, followed by detections with level 3+ growth. About 60% of Q4 submissions where Salmonella was detected had GI clinical signs (scours, diarrhea), reported in the submission history provided, which was consistent  with the detections in Q2 and Q3 2023. Salmonella Typhimurium and the monophasic Typhimurium variant serotypes consistently accounted for a large proportion of detections during Q4 2023. Please note that serotyping data for December 2023 was not available at the time of analysis. Salmonella Worthington was also detected in 5 submissions (from 5 different premises) during this period, which did not align with serotypes reported in Q4 2022. Majority of the Salmonella positive submissions came from nurseries, and a mix of different serotypes were found within each herd type.

OAHN Veterinary Clinical Impression Survey Veterinary Comments

In addition to providing their insight on the frequency of a list of diseases for the herds where they are the vet of record, a number of practitioners graciously take the time to provide short comments about disease activity in their practice. We are limited on what we can include on the final report, but we are appreciative of the observations by the vets with “boots on the ground”.

The comments from practitioners from Q4 included: One case Edema Disease; one case A suis in a sow herd; more Strep suis cases that are difficult to control; H3N2 outbreaks in H3N2 naïve herds are clinically relevant; submitting more trachea and finding more tracheitis; increased coccidiosis as producers adjust prevention programs in the face of tough economics; more Ascarids and wondering if related to increased loose sow housing; prolapse issues in sows too high; pesky PRRSV issues; PCV2 ; Sapovirus detection often found with Rotavirus; more “skinny” sows; Salmonella.

Porcine Circovirus Type II (PCV2)

There were 62% of practitioners that indicated that PCV2 activity was increased when compared to the previous quarter. This is a very notable increase from previous quarters and previous years. Usually there about 21% to 29% of practitioners that would rank clinical PCV2 as being “common” but in Q4 this number jumped to 64%. The cause for this perceived increase is unknown. In the past veterinarians have commented that sporadic cases of clinical PCVD2 has been related to vaccine storage or administration errors, fractionated dosages or changes in vaccine timing. Sow herd instability with increased shedding by sows and the subsequent increased infectious pressure can also set off increased clinical disease. Another possibility is that increasing PRRS challenges are undermining some of the PCV2 control. In the past most of these issues have been resolved. Since 2006 when PCV2 vaccines became available the control of PCV2 has been nothing less than remarkable even as the virus has slowly been evolving. Many in the industry are wondering if “the other shoe will drop” and we lose some of the control provided by the current vaccines. Too early to tell on this but we will certainly keep an eye on this one.

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

Jessica Fox, Manager at Swine Health Ontario (SHO) reported that the overall incidence of PED and PDCoV in Q4 was low. The following cases were reported in Q4 2023. The practitioner involved suggested that these cases were likely associated with lapses in biosecurity.

Dec. 27, 2023  Lambton  PED  Finisher

Dec. 29, 2023  Oxford  PED  Finisher

Jessica also reported that there were 8 additional cases in Q1 2024 thus far. Three cases where PED was detected initially infecting the sow herd and then the virus moved to two other related barns. With PDCoV there were also three cases that were detected in a farrowing unit and also infected two other barns in the downstream flow.

Jan.  03, 2024  Waterloo  PED  Nursery

Jan.  03, 2024  Waterloo  PED  Farrow-to-wean

Jan.  03, 2024  Perth  PED      Farrow-to-wean

Jan. 15, 2024  Oxford  PED  Farrow-to-finish

Jan. 18, 2024  Wellington  PDCoV  Finisher

Jan. 18, 2024  Haldimand  PDCoV  Farrow-to-wean

Jan.  22, 2024  Elgin  PDCoV  Nursery

Jan.  26, 2024  Middlesex  PDCoV  Nursery

All cases are pursuing elimination. Some of these cases were identified on a traceback from a positive test at a processing plant. This testing by processors continues to be extremely helpful. SHO has sent out a notice to the industry as reminder of the importance of following biosecurity protocols. 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

Laboratory Diagnostic Reports

Animal Health Laboratory (AHL)- Pathology Cases  

Drs. Josepha DeLay and Tim Pasma provided an update on AHL activity in Q4 2023. A total of 1250 swine cases, representing all test types, were submitted to the AHL during 2023 Q4. Of these, 100 cases had a pathology component (gross post-mortem and / or histopathology) and originated from commercial herds.   Six (6) additional Q4 pathology cases were from pet pigs. A total of 19 pet pig cases were submitted in 2023.

For pathology cases, the PID inclusion rate continues to increase (93% – highest rate over the past 3 years).  Age or commodity group was provided for 100% of cases and adequate clinical history was provided for 97% of casesThese efforts by swine practitioners are very much appreciated. Inclusion of history and commodity group has a significant impact on the interpretation of pathology and other test results by diagnosticians and helps to produce the most useful answers possible for vets and producers. Thank You!!!  Detection of most pathogens and disease conditions remained stable during Q4, with no significant trends identified. PRRSV- and influenza A virus-positive case numbers remained stable compared with Q3.

Interesting cases diagnosed at the AHL during 2023 Q4 are as follows:

  • Tracheitis continues to be diagnosed more frequently than in previous quarters and years (16 cases in Q4) and this is mainly due to the increased frequency tracheal samples being included for histopathology. Submission of fresh tracheal samples for ancillary testing would be very helpful. Most cases were from nursery and grow-finish pigs. The cases included erosive tracheitis (7 cases) and necrohemorrhagic tracheitis (4 cases).
  • Glaesserella australis was isolated from 1 case with concurrent pathology although the lesions in this case were not typical of those described with this pathogen or of bacterial pneumonia in general. G.australis was previously isolated in Q1 2023 but unfortunately there was no concurrent histology test for the Q1 case.
  • Porcine sapovirus has been diagnosed more frequently since the adoption of in-house testing at AHL in Fall 2023. Sapovirus was detected in 12 / 22 cases tested in Q4 with Ct ≤23 in 10/12 cases. There were 7 cases ≤10 days old, 1 case in 21-day old pigs and 1 case in nursery pigs. Concurrent GI pathogens were detected in 9/10 cases with rotavirus (8 cases) and Isospora suis (1 case).
  • Streptococcus equi ssp zooepidemicus was isolated from 1 case but this isolate was SzM gene-negative.
  • Pathology diagnosis of septicemia based on histologic lesions was mildly increased.
  • PCVAD pathology diagnoses were mildly increased.
  • Parasitic pneumonia due to larval ascarid migration was diagnosed in 1 herd and this was attributed to increased stocking density in an older facility.
  • Abortion cases include PCV2 (1 case), PCV3 (2 cases). Cause of abortion undetermined (idiopathic) in 50% of cases.
  • B. hyodysenteriae or B.hampsonii cases were not detected.
  • Lawsonia intracellularis-positive cases were mildly increased.
  • Mycoplasma hyopneumoniae-positive cases were mild increased compared to Q2 and Q3 but similar to Q1 numbers.
  • Mycoplasma suis (hemotropic mycoplasma) detection was increase (the increase was associated with increased testing / monitoring in 1 herd.

Gallant Custom Laboratory (CEVA) Diagnostic Reports

Kevin Millsap and Anna Pietruszkiewicz reported on the highlights of the 4 cases submitted to Gallant Labs from Ontario in Q4 2023. Influenza cases included 3 cases of H3N2 and 1 case of H1N2 in Q4 2023.

Ontario Slaughter Statistics

Federal Slaughter Statistic Summary (Q4 Aggregate)

Dr. Christine Pelland reported that due to some technical issues the aggregate federal slaughter statistics were not available for Q4. This data will be available in the future.

Provincial Slaughter Statistic Summary

Dr. Christine Pelland reminded the group that due to the earlier date of this OAHN swine network meeting, December (the last month of data) in Q4 was not available. The initial analysis for Q4 includes the months of October and November and the December data will be added once it is available.

Complete Carcass Condemnations

  • Abscess and peritonitis continue to be the most common causes of carcass condemnations in 2023.
  • For the months of October and November the share of carcass condemnations due to abscess increased by 6.8%. There are no obvious explanations for this increase.

 Partial Portion Carcass Condemnations

  • Parasitic livers continue to be the predominant cause of partial portion condemnations and represent 59 to 79% of total portion condemnations in 2023. Q4 parasitic livers increased by about 6% over Q3.

International Disease Topics Of Interest Summary

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

African Swine Fever (ASF): 2023 year in review

Six countries reported ASF for the first time in 2023: Bosnia and Herzegovina, Croatia, Kosovo, Sweden, Singapore, and Bangladesh. Five countries reported a resurgence of ASF after periods of no cases being reported or cases of ASF appeared in regions of the country that were previously unaffected: Lithuania, Greece, Italy, Mongolia, and the Philippines. (SHIC Swine Disease Global Surveillance Report, 12/05/23-01/01/24)

Belgium: China announced the lifting of its’ ban on pig and pork imports from Belgium. The ban was put in place when ASF was detected in Belgium in September of 2018. In November of 2020, Belgium was declared to be free of ASF. The country had gone over 12 months without detecting a case of ASF in wild boars. Belgium never had a case of ASF in domestic pigs. The Belgium Prime Minister met with the Chinese President and that same day China announced a ban on the importation of pigs, pork and wild boar products from Bangladesh. (The Pig Site,1/19/24).

Sweden: The outbreak of ASF in Sweden that began Sept. 2023 may soon be ending. To date, Sweden has had 62 cases of ASF, all in wild boars. Although there were cases as recent as November 24, 2023, the positive cases in November appear to be from carcasses of wild boars that died in September. When Sweden identified the first case of ASF, a control zone of 100 km² was fenced off with a secondary surrounding fenced off area. Authorities believe most of the wild boars in the control zone have died but culling in the control zone continues. There are few areas in the rest of Sweden with wild boars. Although the source of ASF in Sweden has not been identified there is suspicion that the ASF came from a garbage dump that is close to the epicentre of the outbreak. Up until 15 years ago there were almost no wild boars in the area, but the population of wild boar has grown since then because of the garbage dump.

Authorities feel that there are a number of different reasons that the eradication of ASF is successful. The control zone was fenced in quickly. Hundreds of hunters quickly volunteered to test carcasses. The area had a limited wild boar population and was surrounded by boreal forest which does not favour wild boars. The area is currently covered in snow so more positive cases may be identified in the spring. If no new cases are found from wild boars dying after September, then Sweden could be declared free of ASF by next fall. (Pig Progress,01/10/24).

Sardinia, Italy: Sardinia reported its’ first case of ASF Genotype II in September 2023 in domestic pigs. Historically, Sardinia was endemic for ASF genotype I. Sardinia was in the final stages of eradication of ASF Genotype I with three ASF control regions in Sardinia. Fortunately, the first case of ASF Genotype II was quickly identified because of the control measures already in place. An extensive epidemiological investigation found that the producer where the first case of ASF Genotype II was found was also working in a butcher shop. Waste from the shop was fed to his pigs. Further investigation traced some of the pork that was sold in the butcher shop back to farms on the Italian mainland that had broken with ASF. This ASF contaminated pork made its’ way through the production system despite recalls. Italy reported its’ first case of ASF Genotype II in wild boars in January 2022 and the first case in domestic pigs in August 2023. (The Long Jumping of ASF: First Genotype II Notification Sardinia Italy, Viruses 12/23/23).

Italy: Mislabeled vegan snacks from China were found to contain pork that tested positive for ASF. (CEZD,01/15/24). Yikes!

Montenegro: Montenegro reported its’ first case of ASF on January 12th, 2024. Two wild boars tested positive. These boars were found near the border with Bosnia and Herzegovina. Bosnia and Herzegovina is positive for ASF.

Porcine Reproductive and Respiratory Syndrome (PRRS)

L1C.5 (L1C variant)1-4-4: The most frequent wild type PRRSV detected in the U.S. in 2023 were: L1C.5 (L1C variant)1-4-4, L1A 1-7-4 and L1H 1-8-4.  In 2023, L1C.5 (L1C variant)1-4-4 was detected in 13 states located in the Midwest and some neighbouring states. Since the emergence of L1C.5 (L1C variant)1-4-4 in 2020, this strain has been found in 17 states. (SDRS #71, 01/02/24).

Alternative Sampling for PRRS in Endemic PRRSV Infected Breeding Herds: Researchers looked at different methods of detecting PRRSV in weaning pigs in endemically affected breeding herds. Three methods were evaluated: serum, family-oral-fluids (FOF) and udder wipes (UW). In the study four batches with 30 litters per batch were tested. Blood samples were collected from included litters. Samples were pooled 3:1 and 5:1. The researchers found there was good correlation between sera and FOFs, but UWs were poor at detecting PRRSV. When FOFs were pooled 3:1 there were 7 out of 9 positive samples that were misclassified as negative. When pooled 5:1 there were 8 out of 9 positive samples that were misclassified as negative. The study concluded that FOF are a good alternative to blood but need to be analyzed individually (no pooling). UW are not suitable for sampling for PRRSV. (UMN Swine News 12/08/23).

Air filtration: A study was done to evaluate the effect of different levels of biosecurity in reducing the incidence of PRRSV in a large commercial production company in the US Midwest. The study took place from 2009 to 2020. The average annual incidence of PRRS in the breeding herds was 33% with a range of 20% to 50%. A second part of the study took place over 1 year from July 2021 to June 2023. Breeding herds were classified as Next Generation Biosecurity (NGB Complete) when all biosecurity protocols and including air filtration were in place. NGB Incomplete breeding herds had implemented all next generation biosecurity protocols with the exception of air filtration.  There were 56 breeding herds that were NGB Complete and 20 breeding herds that were NGB Incomplete. The PRRS incidence risk in NGB Complete was 8.9% versus 40% in NGB Incomplete. (ASSV News 01/17/24).

Influenza A Virus (IAV)

UMN Studies on Influenza: Over the last 10 years the University of Minnesota has done a number of studies trying to understand influenza. This is a brief summary of some of those studies:

  • 2023, farm workers vaccinating and weaning 3-week-old pigs can contribute to the spread of IAV on swine farms.
  • Study by Dr. Pardo from 2011-2017 found that pigs raised by vaccinated sows were less likely to have the disease. Gilts entering the herd and who were IAV positive were more likely to have pigs positive at weaning.
  • A study of 34 breed-to-wean farms over 5 years found that the prevalence of influenza ranged from 7% to 57%, with a median of 28%. There was a cyclical pattern with peak infection rates in December and May correlated with low temperatures and low humidity.
  • A 2020 study by Dr. Garrido-Mantilla of 184 sows from 3 breeding herds found that on udder wipes a higher percentage of nurse sows than control sows were positive for IAV. Nurse sows can contribute to transmission and perpetuation of influenza prior to weaning. (Swine web.com,01/24/24).

Are swine exhibitions worth the risk of spreading Influenza?: Swine exhibitions can be a high risk for the zoonotic transmission of IAV. Pigs and people are often comingled for extended periods of time. In the U.S.A., the majority of zoonotic transmissions of IAV are linked to swine exhibits. A study was carried out to look at the value of the exhibition swine industry in the U.S. and possibly help make more informed decisions on mitigation strategies. The study found in 2018 that the direct economic impact of the exhibition swine industry was $1.2 billion. Cancelling the exhibition swine industry would cause a loss of $357.1 million. The study concluded that the focus should be on finding better mitigation strategies. (Prev Vet Med, 2024, Brophy et al.).

Astrovirus Type 4

SHIC is funding a study to investigate the pathogenesis of Porcine Astrovirus type 4, (PoAstV4). Previous studies have found PoAstV4 in respiratory tract lesions but the contribution of PoAstV4 to clinical disease is not well understood. The new study will try to determine if PoAstV4 is a primary cause of disease, examine the course of the disease and try to develop methods of accurate detection. The study will be done with high health caesarian derived pigs that will not have colostral antibodies to protect against PoastV4. Another study funded by SHIC in 2022 looked at the presence of PoAstV4 in lesions consistent with viral infection of airways. That study found PoAstV4 in 85 out of 117 samples. (AASV News Archive,01/17/24).

OAHN Project Update: Porcine Hemagglutinating Encephalomyelitis Virus 

Dr. Tim Blackwell provided a status update on a new OAHN project that is focused on Porcine Haemagglutinating Encephalomyelitis virus (PHEV). This is a virus that has been present in Ontario for some time. There are currently some suspicions that PHEV may be involved as an etiological agent of hemorrhagic tracheitis and bronchitis. Thus far the data to support this connection is not very strong. In addition, there are lots of other candidate viruses that have been suggested as etiological agents for the clinical signs and pathologic lesions associated with tracheitis. In its simplest form, the project would look at the prevalence of PHEV in laboratory submissions to the AHL and this would include cases with or without complaints of respiratory disease. If we start to see suspicious associations of PHEV PCR tests with low Ct values and clinical signs and tracheitis pathology, then we may send some of those tissues to Iowa for in situ hybridization testing to see if we can identify the PHEV within the affected tissues within the respiratory tract. Currently the project is going through the costing process and that will inform the potential scope of the project.

How can you Participate in OAHN?

Look for the 2024 Q1 veterinary clinical impression survey that will come out the first week of April 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.

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