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.

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