Document Type

Thesis - University Access Only

Award Date

2004

Degree Name

Master of Science (MS)

Department / School

Veterinary and Biomedical Sciences

First Advisor

Eric A. Nelson

Abstract

Porcine Reproductive and Respiratory Syndrome (PRRS) continues to be one of the most significant diseases of swine. The annual cost to the United States swine Vl industry was estimated at 600 million dollars. The syndrome is endemic worldwide in areas of intensive swine production with prevalency rates as high as 96% of market pigs. PRRS has an extremely varied clinical picture and affects all aspects of modem swine production. Symptoms range from dramatic abortion storms in the sow herd, to significant mortality in the nursery, to respiratory complications in the finishing barn, and to mild or no symptoms in the boar herd. Several different virus control and elimination methods are in use and invariably rely on serological testing. A commercially available enzyme linked immunosorbent assay (ELISA; IDEXX HerdChek® PRRS) has become the industry standard for the detection of antibodies against PRRS virus (PRRSV). The need to accurately determine the PRRSV serostatus of herds and individual animals has prompted the development of several follow-up assay methods. Virus isolation (VI), polymerase chain reaction (PCR), and indirect fluorescent antibody (IF A) assays are often used. Each assay has limitations that decrease the utility of the information provided. A highly specific and repeatable blocking ELISA (bELISA) was developed to address those limitations. The bELISA was based on an expressed PRRSV nucleocapsid (N) protein as the antigen and a biotinylated monoclonal antibody. Validation of the bELISA used sera from 316 animals experimentally and naturally infected with North American PRRSV and sera from 3 70 uninfected animals. Receiver operating characteristic (ROC) analysis of the data calculated a diagnostic sensitivity of 97.8% and a diagnostic specificity of 100%. The between-run coefficient of variation of an internal quality control serum was 4.24%. The bELISA would be useful as a follow-up test to the IDEXX ELISA to resolve unexpected positive results in expected negative swine herds. Therefore, serodetection and specificity of the bELISA are very important. The bELISA was able to detect seroconversion as well as the IDEXX ELISA and the indirect fluorescent antibody (IF A) assay; kappa values were 0.94 and 0.96 respectively. A collection of 133 serum samples with unexpected positive IDEXX ELISA results was obtained from 4038 diagnostic samples submitted from expected PRRS negative farms. The bELISA identified 97% of the samples as PRRS seronegative while the IFA identified 100% as seronegative. The bELISA for the detection of antibodies against PRRSV is an accurate, specific, repeatable alternative to current methods used to investigate unexpected positive IDEXX ELISA results.

Library of Congress Subject Headings

Porcine reproductive and respiratory syndrome.
Enzyme-linked immunosorbent assay.
Viral antibodies.
Swine -- Virus diseases.

Publisher

South Dakota State University

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Rights Statement

In Copyright