Science page: Evaluation of positive pressure filtration to reduce aerosol transmission of PRRSV during an experimental challenge of farm access points

This is our Friday rubric: every week a new Science Page from the Swine Health Monitoring Project. The previous editions of the science page are available on our website.

Key points from this week edition:

  • Dilute vaccine aerosolization combined with novel environmental sampling techniques allowed for testing of PRRSV aerosol entry into Positive Pressure Filtration (PPF) farm access points.
  • Under the experimental conditions of this study, positive pressure air speeds >1.85m/s resulted in no aerosol transmission.
  • Ensuring adequate positive pressure air speed through steps taken to increase access point pressure can further reduce the risk of aerosol PRRSV transmission on PPF farms.

The full report on positive pressure filtration and PRRSV transmission via aerosols is available.

Detecting Senecavirus A in tissues: development of a new diagnostic test at the University of Minnesota

Summary

In Canada and the USA alike, Senecavirus A is a challenge for producers and veterinarians because of its clinical similarity to Food and Mouth Disease (FMD). Indeed, Senecavirus A, is a causative agent of swine vesicular disease with lesions developing on the snout, around the mouth and on the coronary band of the feet. Therefore, being able to differentiate Senecavirus A infections from FMD rapidly is of utmost importance to be able to take the appropriate measures.

In the past months, several diagnostic tests have been developed at the University of Minnesota to detect antibodies against Senecavirus A. The difference between those tests and the in situ hybridization (ISH) described here is that ISH targets the genetic material included in the viral particle and marks it as a red spot as can be seen on the figure below. This advantage of this method is to be able to locate the virus and gives additional information to researcher wanting to study the behavior of Senecavirus A in the body of the pig.

in situ hybridization senecavirus A pigs
Red dots and clusters represent the presence of SVV mRNA within an erosive lesion on the tongue of a pig © 2017 Resende et al.

Abstract

Seneca Valley virus (SVV) is the causative agent of an emerging vesicular disease in swine, which is clinically indistinguishable from other vesicular diseases such as foot-and-mouth disease. In addition, SVV has been associated with neonatal mortality in piglets. While a commercial SVV qRT-PCR is available, commercial antibodies are lacking to diagnose SVV infections by immunohistochemistry (IHC). Thus, a novel in situ hybridization technique—RNAscope (ISH) was developed to detect SVVRNA in infected tissues. From a total of 78 samples evaluated, 30 were positive by qRT-PCR and ISH-RNA, including vesicular lesions of affected sows, ulcerative lesions in the tongue of piglets and various other tissues with no evidence of histological lesions. Nineteen samples were negative for SVV by qRT-PCR and ISH-RNA. The Ct values of the qRT-PCR from ISH-RNA positive tissues varied from 12.0 to 32.6 (5.12 x 106 to 5.31 RNA copies/g, respectively). The ISH-RNA technique is an important tool in diagnosing and investigating the pathogenesis of SVV and other emerging pathogens.

Link to the full article

Science page: M. hyopneumoniae outbreaks: what you need to know to aid in your investigation

This is our Friday rubric: every week a new Science Page from the Swine Health Monitoring Project. The previous editions of the science page are available on our website.

Key points from this week edition:

Molecular characterization tools such as p146 sequencing for Mycoplasma hyopneumoniae (M. hyopneumoniae) can provide insight towards investigating elimination failures or new introductions within swine herds.

Can biosecurity measures prevent PEDV transmission?

Summary:

Porcine Epidemic Diarrhea virus is highly contagious.

The 2013 Porcine Epidemic Diarrhea virus’ (PEDV) outbreak in the USA taught the swine industry that the virus is highly contagious. This event forced producers and veterinarians to review and upgrade their biosecurity procedures.

Drs. Torremorell, Cheeran, and Goyal from the University of Minnesota evaluated some of these measures and how they can prevent PEDV transmission.

Changing Personal Protective Equipment (PPE) and showering before entering a new room prevented contamination.

Among the measures included in this study were the use and change of PPE as well as showering in and out of a facility. In the low biosecurity setting, personnel went from a room with PEDV positive pig straight to a room with naive pigs, contaminating them after the very first movement. In the medium biosecurity setting, personnel washed their hands and face and change their PPE before being in contact with the naive pigs. In this situation, pigs stayed negative for PEDV but  two personnel hair/face swabs came back positive for viral genetic material. On the contrary, personnel showered before getting in contact with the high biosecurity group. Those pigs as well as all personnel tests remained negative for PEDV during the study.

 

Torremorell PEDV biosecurity 2017

Abstract

Background:

The effectiveness of biosecurity methods to mitigate the transmission of porcine epidemic diarrhea virus (PEDV) via farm personnel or contaminated fomites is poorly understood. This study was undertaken to evaluate the effectiveness of biosecurity procedures directed at minimizing transmission via personnel following different biosecurity protocols using a controlled experimental setting.

Results:
PEDV RNA was detected from rectal swabs of experimentally infected (INF) and sentinel pigs by real-time reverse transcription polymerase chain reactio n (rRT-PCR). Virus shedding in INF pigs peaked at 1 day post infection (dpi) and viral RNA levels remained elevated through 19 dpi. Sentinel pigs in the low biosecurity group (LB) became PEDV positive after the first movement of study personnel from the INF group. However, rectal swabs from pigs in the medium biosecurity (MB) and high biosecurity (HB) groups were negative during the 10 consecutive days of movements and remained negative through 24 days post movement (dpm) when the first trial was terminated. Viral RNA was detected at 1 dpm through 3 dpm from the personal protective equipment (PPE) of LB personnel. In addition, at 1 dpm, 2 hair/face swabs from MB personnel were positive; however, transmission of virus was not detected. All swabs of fomite from the HB study personnel were negative.
Conclusions:
These results indicate that indirect PEDV transmission through contaminated PPE occurs rapidly (within 24 h) under modeled conditions. Biosecurity procedures such as changing PPE, washing expose d skin areas, or taking a shower are recommended for pig production systems and appear to be an effective option for lowering the risk of PEDV transmission between groups of pigs.

Link to the full text

Characterizing Canadian rotavirus A strains and their similarity to a commercial vaccine

Summary:

Rotaviruses A are genetically diverse.

Rotaviruses are responsible for increased mortality in neonatal swine populations. They are different genetically and more studies are needed to characterize their diversity. This is the objective of this study coordinated by Dr. Marthaler’s lab focusing on rotaviruses strains found in Canada.

Viral proteins 7 and 4 are used for rotavirus A classification.

Rotaviruses are classified based on two viral proteins (VP) found on their outer capsid called respectively VP7 and VP4. Those two proteins are also essential to induce an efficient immune response against the virus. This project characterized VP7 and VP4 sequences in 136 Canadian samples and compared them with the strains used in a rotavirus commercial vaccine.

The VP7 (n=32) and partial VP4 (n=25) were analyzed, identifying the G3P[13], G5P[7], G5P[x], G9P[7], G9P[13], G9P[19], and G9P[x] genotypes.
Minimal differences in the antigenic epitopes for the G5, G9, and P[7] strains were identified.
Major differences in the antigenic epitopes of the G3, P[13], and P[19] may question the effectiveness of the ProSystems RCE RVA.

Marthaler rotavirus A Canada 2017

Abstract

Surveillance of Rotavirus A (RVA) infections in North America swine populations are limited and not performed over a significant time period to properly assess the diversity of RVA strains in swine. The VP7 (G) and VP4 (P) genes of 32 Canadian RVA strains, circulating between 2009 and 2015 were sequenced, identifying the G3P[13], G5P[7], G9P[7], G9[13], and G9[19] genotype combinations. The Canadian RVA strains were compared to the RVA strains present in the swine ProSystems RCE rotavirus vaccine. The comparison revealed multiple amino acid differences in the G and P antigenic epitopes, regardless of the G and P genotypes but specifically in the Canadian G3, P[13] and P[19] genotypes. Our study further contributes to the characterization of RVA’s evolution and disease mitigation among swine, which may optimize target vaccine design, thereby minimizing RVA disease in this economically important animal population.

Link to the full article

Science page: Measuring production losses from endemic PRRS in US farms

This is our new Friday rubric: every week a new Science Page from the Swine Health Monitoring Project. The previous editions of the science page are available on our website.

Key points from this week edition

We analyzed performance records from 16 sow farms that were vaccinated with PRRS virus and experienced a PRRS virus infection.

Production dropped until the 6th week post-outbreak with a second decline between the 11th and 18th week post-outbreak.

We calculated an average decrease of 1.92 weaned pigs per sow (min=0.51, max=3.72) per year attributable to changes in farrow rate and prewean mortality.

The full report on production losses from endemic PRRS farms in the US is available.

 

 

Sample and diagnostic types for early detection of Mycoplasma hyopneumoniae

Summary:

Mycoplasma hyopneumoniae is the causative agent enzootic pneumonia, an economically significant disease in pigs. In this study published by Drs. Pieters and Rovira from the University of Minnesota, pigs experimentally inoculated with M.hyopneumoniae were sampled 0, 2, 5, 9, 14, 21, and 28 post-inoculation.

Different sample types were compared:

  • Nasal swabs
  • Laryngeal swabs
  • Tracheobronchal lavages
  • Oral fluids
  • Serum samples

Using different diagnostic tests:

  • PCR
  • ELISA IgG anti M.hyopneumoniae
  • ELISA Ig M anti M.hyopneumoniae
  • ELISA C-reactive protein

Laryngeal swab samples tested by PCR were highly sensitive for detection of Mycoplasma hyopneumoniae in live pigs.
Various commercial ELISA kits for detection of Mycoplasma hyopneumoniae antibodies showed similar sensitivity.
Oral fluids showed a low sensitivity for detection of Mycoplasma hyopneumoniae in experimentally infected pigs.

Pieters Mhyopneumoniae early detection test sample 2017

Abstract

Detection of Mycoplasma hyopneumoniae in live pigs during the early stages of infection is critical for timely implementation of control measures, but is technically challenging. This study compared the sensitivity of various sample types and diagnostic methods for detection of M. hyopneumoniae during the first 28 days after experimental exposure. Twenty-one 8-week old pigs were intra-tracheally inoculated on day 0 with M. hyopneumoniae strain 232. Two age matched pigs were mock inoculated and maintained as negative controls. On post-inoculation days 0, 2, 5, 9, 14, 21 and 28, nasal swabs, laryngeal swabs, tracheobronchial lavage fluid, and blood samples were obtained from each pig and oral fluid samples were obtained from each room in which pigs were housed. Serum samples were assayed by ELISA for IgM and IgG M. hyopneumoniae antibodies and C-reactive protein. All other samples were tested for M. hyopneumoniae DNA by species-specific real-time PCR. Serum antibodies (IgG) to M. hyopneumoniae were detected in challenge-inoculated pigs on days 21 and 28. M. hyopneumoniae DNA was detected in samples from experimentally inoculated pigs beginning at 5 days post-inoculation. Laryngeal swabs at all samplings beginning on day 5 showed the highest sensitivity for M. hyopneumoniae DNA Detection, while oral fluids showed the lowest sensitivity. Although laryngeal swabs are not considered the typical M. hyopneumoniae diagnostic sample, under the conditions of this study laryngeal swabs tested by PCR proved to be a practical and reliable diagnostic sample for M. hyopneumoniae detection in vivo during early-stage infection.

Link to the full-article