In lieu of the Science Page today, we are bringing you our most popular articles on the blog this past year: a publication by Dr. Maria Pieters, head of the MycoLab called Sample and diagnostic types for early detection of Mycoplasma hyopneumoniae.
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:
Using different diagnostic tests:
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.
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.
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.