Epidemiologic studies related to eradication of pseudorabies infection in swine

摘要

The dissertation is composed of four chapters. Four epidemiologic questions arose during the course of a pilot program for the elimination of pseudorabies from herds of swine in Marshall County, Iowa. Corresponding parts of this dissertation attempt to answer these questions;A new serological test, the latex agglutination (LA) test, for pseudorabies virus (PRV)-specific antibodies became available in 1986. A comparative study of this test with other routinely used tests for pseudorabies antibodies was needed and undertaken. Results indicated that the LA test was more sensitive than either the enzyme-linked immunosorbant assay (ELISA) or the serum virus neutralization (SVN) test in detecting vaccine-induced antibodies. The LA test detected antibodies sooner than the ELISA and the SVN test in unvaccinated pigs after challenge with virulent PRV. The specificities of the three tests were found to be near 100%. It was concluded that the LA test should be considered to be a good alternative to the SVN test or the ELISA for detection of PRV-specific antibodies;The survival of PRV in an aerosol was studied under five environmental conditions of temperature and relative humidity (RH). Information on PRV survival was needed in order to begin to assess the possibilities of long distance transmission of PRV through the air. Results indicated that, in aerosol, PRV decayed at half-lives of from 17 to 44 minutes depending on the temperature and RH conditions;The effect of vaccination on the rate of PRV latency and PRV reactivation subsequent to challenge with virulent PRV was studied. Pseudorabies vaccines were used as aids in efforts to rid infected herds of swine of the infection. Vaccination controls clinical disease but vaccinated swine may become latently infected when they are exposed to virulent PRV and subsequently reactivate and shed the virus. Based on results of the study, it was concluded that vaccination against PRV infection had little or no effect on virus latency rate following exposure to virulent PRV nor on the reactivation of subsequent shedding of the virus;A computer-assisted record-keeping system was needed to collect and manipulate data related to PRV control. A system of programs were developed and collectively called Pseudorabies Reporting and Information System Management (PRISM). The system was easy to use and learn, was written in the Dbase III+ programming language, and appears in the dissertation. It was speculated that the data collected in PRISM would be useful tools for studying future epidemiologic questions related to pseudorabies.