Ontario Animal Health Network (OAHN) Swine Network Quarterly Veterinary Report
Disease Surveillance Discussion
Porcine Epidemic Diarrhea (PEDV) / Porcine Deltacoronavirus (PDCoV)
Jessica Fox, Manager at Swine Health Ontario reported the following cases in Q2:
|Date||County Name||Disease Type||Farm Type|
Jessica reported that there has been one additional case in Q3 thus far:
|Date||County Name||Disease Type||Farm Type|
The PED and PDCoV tracking map is available at the Swine Health Ontario website and shows current and annual cases by county: http://www.swinehealthontario.ca/Disease-Information/PED-PDCoV-Tracking-Map
Influenza A (IAV)
All responding veterinarians to the clinical impression survey rated the frequency of IAV as common (67%) and very common (33%). The following Influenza genotypes were identified in 43 submissions in Q2 2022: Subtype H1N1 classical= 5 total with 0 alpha, 5 beta, 0 gamma. Pandemic H1N1= 3. Subtype H3N2= 18 total. Subtype H1N2= 14 .Gallant Laboratories Ontario data indicated that there were no IAV isolates in Q2.
Porcine Respiratory and Reproductive Virus (PRRS)
A total of 84% of responding practitioners ranked the frequency for PRRS as common (67%) and very common (17%). A total of 41% of practitioners indicated that PRRS activity in the breeding herd had increased in Q2 vs Q1. There were three practitioner comments that indicated that the success rate of PRRS elimination projects has been decreasing and in general PRRS elimination projects have been more challenging.
Dr. Christine Pelland commented that some of the elimination challenges can be associated with some strains more than others. The 1-8-4 strains that have been clinically significant and have been a problem. Elimination strategies, in farrow-to-wean barns often use a combination of serum exposure and vaccination at the onset of elimination and then front load with gilts. Increasingly practitioners find that it is taking longer to get to PRRS virus negative processing fluids. The timeline for birth of PRRS virus negative animals post exposure is being pushed out. Previously it was common to find PRRS virus negative pigs at birth starting at 120 days post exposure. It is not uncommon now to find those timelines being pushed out to 150 or 160 days. That extends the whole timeline which historically has involved a 200-day closure. PRRS virus surveillance based on processing fluids can be more variable with several weeks in a row of negatives and then all of a sudden, a positive will pop up and then back to negative on the next test.
When processing fluids are testing negative the more intense McRebel can begin. As the 200-day post closure milestone approaches the pigs may test negative for some time and then a PRRSV positive will show up. Why this virus is sequestered at this late stage of the elimination is not known.
Laboratory Diagnostic Reports
Dr. Tim Pasma summarized findings from the AHL Syndromic Surveillance in Q2:
2022 Q2 was a fairly active influenza season with signals based on both respiratory signs and mortality.
- Week 15 (Apr 10)– based on reported clinical signs (4/5) and mortality (1/5)- H1N1 (3), H1/N1/N2, ELISA (2)
- Week 17 (Apr 24)– based on reported clinical signs (2/3)– H3N2 (2), H1N2 (1)
- Week 26 (Jun 26)- based on reported clinical signs (2/5)- H1 (1), H3N2 (4)
Over the last year H1N2 (36.3%) remains the dominant subtype followed by H3N2 (33%) and H1N1 (23.2%).
Porcine Epidemic Diarrhea Virus (PED)
There had been ongoing detections of PEDV in Q2.
Porcine Deltacoronavirus (PDCoV)
There had been a gradual decline in the number of PDCoV detections in Q2.
There were no syndromic signals to report in Q2.
Animal Health Laboratory Diagnostic Reports
Dr. Josepha DeLay and Dr. Tanya Rossi reported that a total of 99 pathology cases were submitted to the AHL for 2022 Q2 (including cases until June 24, 2022. Please note that cases submitted June 25-30 will be reported with the 2022 Q3 summary). The Q2 swine cases included 91 cases originating from commercial herds of various sizes, 2 meat inspection cases, and 6 pet pig cases. The PID inclusion rate (63% of cases) was down from Q1 at (73% of cases). There is still substantial room for improvement on the reporting of PID information. Age or commodity group was provided for 99% of all cases (97% reported in Q1). Adequate clinical history was provided for 93% of the cases (89% in Q1).
Notable pathogens or disease syndromes detected, and apparent trends identified during 2022 Q2 are as follows:
- Septicemia in 2/1400 recently weaned pigs with gross lesions mimicking swine viral hemorrhagic fever (ASF, CSF – hemorrhagic lymph nodes, myriad renal petechial hemorrhages, myocardial hemorrhage). With CFIA’s permission, PCR testing for these pathogens was carried out at the AHL, and results were negative. Pasteurella multocida was isolated in moderate to large numbers from affected lymph nodes and filtering organs from 1 pig, and S. suis was isolated from the second pig. One pig also had an ulcerate cutaneous lesion on snout mucosa that was histologically compatible with an infarct, presumably associated with sepsis. Senecavirus A was not detected in the lesion by PCR. Further testing was not required by CFIA, based on clinical scenario. Pasteurella multocida septicemia is uncommon in our lab’s experience, but has been previously described in swine, with lesions similar to those identified in these pigs.
- Overall PRRS virus and influenza-positive pathology case numbers were decreased this quarter compared with Q1.
- Acute myopathy in 11/1200 finisher pigs was suspected to result from selenium deficiency and/or ionophore toxicosis, based on microscopic lesions. No new clinical cases developed following change to new feed, although the etiology could not be confirmed based on testing of the original feed. Liver selenium levels in affected pigs were mildly decreased from reference values.
- Nutritional myopathy was confirmed in 2 KuneKune pigs from a small herd, based on low liver selenium levels. Unusually for swine, lesions were most severe in skeletal muscle, with only mild myocardial lesions. We have seen similar lesion distribution with selenium deficiency in other KuneKune pigs.
- Lymph node abscesses with mineralization were identified in head and cervical lymph nodes from market hogs. The lesions are more typical of a generic bacterial etiology, although mycobacterial culture is pending.
- Update from Q1 market hogs with granulomatous lymphadenitis involving head and cervical nodes: Mycobacterial culture and speciation results are compatible with Mycobacterium avium ssp avium in affected nodes.
- The AHL’s annual foreign animal disease exercise, held in April 2022, focused on swine hemorrhagic fever (ASF, CSF).
There was nothing remarkable in Q2 with respect to non-pathology cases.
Gallant Custom Laboratory Diagnostic Reports
Anna Pietruszkiewicz summarized the report on the 15 cases submitted to Gallant Labs from Ontario in Q2 2022. The number of cases was lower than Q2 2021 and Q1 2021 and Q1 2022.
- Strep. suis isolations, Glaeserrela parasuis isolations all declined in Q2.
- E. coli ETEC also declined in Q2.
- There were no Influenza A in swine isolations in Q2.
Federal Slaughter Statistic Summary (Q2 Aggregate)
Dr. Christine Pelland along with assistance to compile the data by Gillian Greeves reported the following:
- Erysipelas condemnations seem to be down for Q2 2022 and that is following the seasonal pattern.
- Abscess condemnations show a slight decrease but that is following a bit of a trend that is seen year over year.
- Enteritis condemnations at 16.3% of condemns is at the highest been over the last number of years. The reason for this is not known and plans are to follow up on this.
- Peritonitis condemnations are quite high and plans were to dig into this a bit further and try to understand this classification is determined.
Trim Demerit Condemnations
- Abscesses in general are always our greatest reason for trims, but it does seem to be reducing in prevalence over time.
Ontario Provincial Slaughter Statistic Summary
Dr. Christine Pelland reported there were no significant changes in the provincial statistics.
CanSpotASF Surveillance Update
Dr. Christa Arsenault provided an update on CanSpotASF activity in Ontario. CanSpotASF is a risk-based early detection testing program that is available at approved Canadian Animal Health Surveillance Network (CAHSN) laboratories, which includes the Animal Health Lab (AHL) in Ontario. The CanSpotASF program is set up with the goal of early detection of ASF. It is to be used when ASF is not a main rule-out diagnosis and where early clinical signs of ASF could be masked by other routinely diagnosed swine endemic viruses in Canada. If ASF is suspected on a farm/premise, the Canadian Food Inspection Agency (CFIA) must be notified immediately.
Approved laboratories that are part of the CAHSN network can now test for ASF. Until the launch of this program these types of cases have not been tested. CanSpotASF testing is targeted at herds with endemic diseases that could mask ASF and therefore delay detection. This program works on the premise that early detection if ASF arrives in Canada will in turn limit the spread of this virus, leading to a faster and more efficient outbreak response. Veterinarians and/or pathologists can initiate ASF rule-out testing for submissions that meet eligibility criteria.
There are many reasons why not all cases that are deemed eligible for CanSpotASF are tested including, but not limited to the following; missing information on submission form e.g. PID and missing tissues required to test for ASF. To increase CanSpotASF submissions, an infographic providing a reminder to take and include the spleen with samples being submitted to the AHL was created and entitled “Make Spleen Routine”. Please download a copy and use this infographic as a visual reminder to indicate this on the lab submission forms for samples that meet the eligibility criteria for CanSpotASF: https://www.oahn.ca/resources/infosheet-make-spleen-routine/
CanSpotASF Testing Summary
|OAHN (Ontario) Period||Number of Eligible Cases||Number of Negative Cases||Number of Positive Cases|
|2022 Quarter 2 (Apr 1-Jun 30)||72||35||0|
International Disease Topics Of Interest Summary
Dr. Al Scorgie provided a summary on some interesting international disease topics of interest for the OAHN Swine network members:
Experimental Infection of Domestic Pigs with a Field Strain of ASF
There were three parts to this trial. The strain of ASF was isolated from an outbreak from July 2021 in the Dominican Republic. This isolate belongs to genotype II and is 99.9% homologous to the Georgia 2007 strain. In the first part of the trial, 5 pigs were inoculated intramuscularly, (IM). In the second part of the trial, five pigs were inoculated oro-nasally (ON). In the third part of the trial, 5 non-infected pigs were co-housed with the IM-inoculated pigs, 24 hours post inoculation. Serial blood, nasal and oral swabs were collected out to 28 days post-inoculation and PCRs, viral titrations and ELISA’s were done. When needed euthanasia was completed for humane reasons. If pigs survived out to 28 days post-inoculation, these pigs were euthanized.
Clinical signs for pigs with IM inoculation included: fever, anorexia and red-purple discoloration of the skin by day 5 pi. Clinical signs of pigs with ON inoculation and IM-contact were more varied. Some showed acute and fatal disease progression quickly, others not until day 12 or 13 post inoculation. Some did not have clinical presentation that was as acute. Three pigs showed no clinical signs except a fever.
The more severe the clinical presentation the higher the viremia titers in blood. For pigs IM-inoculated there were low to moderate virus titers in nasal swabs. For ON-inoculated pigs only one pig had a low level of virus titers in nasal swabs and for IM-contact pigs only two had low levels of virus titers in nasal swabs for 1 day each. No virus was found in oral swabs.
The results show that there is inconsistent production of acute and fatal clinical disease progression of pigs that are not IM-inoculated. All IM-inoculated pigs were euthanized by day 7 post inoculation. Animals that were in contact with IM-inoculated pigs showed a delayed development of symptoms. Researchers estimate that contact pigs were infected 5 to 6 days pi. The findings of no virus in oral swabs were surprising. Three pigs that developed a high level of viremia but did not develop disease had high levels of antibodies. (SHIC, E. Ramirez-Medina et al.)
Italy Confirms First Case of ASF in Domestic Pigs
A case of ASF in domestic swine was confirmed in Italy on May 06th, 2022. Two pigs were infected on a small farm of 8 pigs. This farm was located in a region of Italy that has had 23 cases in wild pigs. (Pig333.com – 2022/06/10)
Superficial Inguinal Lymph Nodes for Screening Dead Pigs for ASF
ASF replicates in a pig’s tonsils and regional lymph nodes after the pig is infected through oro-nasal contact. The virus travels through the blood and lymph systems to secondary lymph nodes within 2-3 days. The spleen is a good organ to test for ASF but the carcass needs to be opened. If the carcass is opened there could be environmental contamination and possibly risk of further spread of ASF. A study was done to examine using superficial inguinal lymph nodes (SILNs) to test for ASF. Five different ASF virus strains were used. Pigs were either inoculated oro-nasally, intramuscularly or through contact with infected pigs. The amount of ASF virus found in the superficial inguinal lymphnode’s was highly correlated with the amount of ASF virus in the spleen. The study showed that superficial inguinal lymph nodes could be used for rapid screening if necropsy is not possible or to avoid opening the carcass. (UMNSwineNews – 2022/05/06)
Spread of ASF In Germany
ASF was confirmed on a farm with 280 sows in Lower Saxony, Germany on July 02, 2022. This farm is 20kms from the border with the Netherlands. The source of the virus is unknown. There are 296 pig farms with approximately 195,000 pigs within a 10km radius of the infected premises. All pig transport in the core zone was stopped. This is the sixth outbreak on a German pig farm since ASF first entered Germany in September 2020. The farm in Lower Saxony is on the other side of the country from where the other cases are and along the border with Poland except for a case in May near the border with France. In May 2022, an outdoor farm in Baden-Wurttemberg, along the border with France tested positive. (Pig Progress – 2022/07/02)
Denmark Develops a National PRRS Control Plan
The plan will require cooperation between the processors, the Danish Veterinary and Food Administration, producers and veterinarians. The goal is to increase the number of PRRS negative farms by mid-2025. The plan includes the following: all suspected cases of PRRS are to be reported, as of July 01, 2022. Any farms of unknown PRRS status or PRRS-positive must report monthly the presence or absence of clinical signs and by the end of 2022 all farms must declare their status with respect to PRRS antibodies. Also, there will be a penalty for pigs processed from PRRS positive farms. Danish Crown, which slaughters 70% of Danish pigs, will start making deductions on January 01, 2023. (Pig333.com – 2022/06/17)
Ontario’s PRRS monitoring continues to be voluntary through the PRRS ARC&E.
Streptococcus equi zooepidemicus
SHIC has reported that outbreaks of Streptococcus equi subspecies zooepidemicus (Strep. zoo) in Ohio and Tennessee in September and October 2019 and an outbreak on a farm in Indiana in February 2021 were caused by different strains. This shows that there is not one strain of the bacteria moving around the country but pockets of different strains of bacteria. Investigations should not look for a common source but treat each outbreak individually. (Farmscape, Bruce Cochrane – 2022/05/17)
Japanese Encephalitis Virus
In a previous OAHN report we wrote about an outbreak Japanese Encephalitis Virus (JEV) in pigs in Australia. JEV is a zoonotic disease and can infect people. As of May 22, 2022, there have been 42 human cases of Japanese Encephalitis (29 confirmed and 13 suspected) and 4 deaths from JEV in Australia.
How can you Participate in OAHN?
Look for the 2022 Q3 veterinary clinical impression survey that will come out the first of Oct via an email through the OASV listserv.
The survey takes less than 10 mins time to complete!