This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
Antimicrobial resistance has been a preoccupying topic for the past few years. We talked before about what the definition of antibiotic resistance is and how it can be interpreted in two different manners. This week, Dr. Alvarez from the STEMMA lab is reporting the trends in antimicrobial susceptibility observed in strains of Streptococcus suis and Pasteurella multocida isolated at the Minnesota Veterinary Diagnostic Laboratory over the past 10 years. S. suis and P. multocida are common swine pathogens that can cause severe economic losses. Knowing which antibiotics are more likely to be efficient against those bacteria can help in tackling the disease faster.
Key Points:
MN-VDL data was analyzed to study antibiotic susceptibility in clinical isolates of Pasteurella multocida and Streptococcus suis from 2006 to 2016.
Isolates were highly susceptible to Ampicillin, Ceftiofur, Enrofloxacin and Florfenicol throughout the study period.
There were no changes in antibiotic susceptibility against the antibiotics tested routinely across the study period.
The Veterinary Diagnostic Laboratory’s mission is to protect and promote animal and human health through early detection and monitoring of animal diseases.
The 2016 report was published last month and we are compiling here the highlights related to swine. We can also read the full 2016 UMN VDL report.
In April 2016, the VDL welcomed its new director Dr. Jerry Torrison.
More than 50% of the procedures in the VDL were related to the porcine species last year.
A new multiplex PCR test that combines Porcine Epidemic Diarrhea Virus (PEDv), Porcine Deltacoronavirus (PDCoV) and Transmissible Gastroenteritis Virus (TGEV) into one assay was implemented into the Molecular Diagnostic clinical testing schedule effective October 31st, 2016. The new assay provides clients with timely, quality results for all three viruses at the same time. The VDL ran 40,131 PEDv and PDCoV Multiplex Real Time PCR tests and 5,238 Triplex (PEDv/TGE/PDCoV) RT-PCR tests.
Additionally, the Serology lab conducted intensive testing in collaboration with Zoetis for validation of PED antibody test kit which they are planning to release on the market soon.
Seneca Valley Virus PCR was validated and is part of routine testing. 3,205 Senecavirus A EZ Real time RT-PCR tests were run. An ELISA test for antibodies to Seneca Valley Virus in pigs is also available.
The IHC lab participated in the 2016 AAVLD/NVSL Program for Inter-laboratory Comparison, and scored 100% in its detection of Porcine Circovirus type 2 in the test samples provided.
Today, we are very pleased to report that a new indirect ELISA to identify Senecavirus A antibodies has been validated at the University of Minnesota and is now available for our Veterinary Diagnostic Laboratory clients. This ELISA targets specifically antibodies against Viral Protein 2 (VP2) and has a sensitivity of 94.2% and a specificity of 89.7%. The test does not cross react with antibodies against Foot-and-Mouth Disease allowing for a quick differentiation between a Senecavirus A outbreak and a costly foreign animal disease.
Fig 1: Different ELISA types (Source: nptel.ac.in)
Abstract
Background: Senecavirus A (SVA), a member of the family Picornaviridae, genus Senecavirus, is a recently identified single-stranded RNA virus closely related to members of the Cardiovirus genus. SVA was originally identified as a cell culture contaminant and was not associated with disease until 2007 when it was first observed in pigs with Idiopathic Vesicular Disease (IVD). Vesicular disease is sporadically observed in swine, is not debilitating, but is significant due to its resemblance to foreign animal diseases, such as foot-and-mouth disease (FMD), whose presence would be economically devastating to the United States. IVD disrupts swine production until foreign animal diseases can be ruled out. Identification and characterization of SVA as a cause of IVD will help to quickly rule out infection by foreign animal diseases.
Methods: We have developed and characterized an indirect ELISA assay to specifically identify serum antibodies to SVA. Viral protein 1, 2 and 3 (VP1, VP2, VP3) were expressed, isolated, and purified from E. coli and used to coat plates for an indirect ELISA. Sera from pigs with and without IVD symptoms as well as a time course following animals from an infected farm, were analyzed to determine the antibody responses to VP1, VP2, and VP3.
Results: Antibody responses to VP2 were higher than VP1 and VP3 and showed high affinity binding on an avidity ELISA. ROC analysis of the SVA VP2 ELISA showed a sensitivity of 94.2% and a specificity of 89.7%. Compared to IFA, the quantitative ELISA showed an 89% agreement in negative samples and positive samples from 4–60 days after appearance of clinical signs. Immune sera positive for FMDV, encephalomyocarditis virus, and porcine epidemic diarrhea virus antibodies did not cross-react.
Conclusions: A simple ELISA based on detection of antibodies to SVA VP2 will help to differentially diagnose IVD due to SVA and rule out the presence of economically devastating foreign animal diseases.
