M E S '9 8 - University of Georgia College of Veterinary Medicine

10respiratory problem in a broiler operation.Modification of the vaccination programbrought the problem under control. The estimatedannual saving is more than $100,000.The PCR technique has permitted generationof more useful and timely informationthan classical diagnostic techniques for infectiousbronchitis and mycoplasmas. Researchcontinues and new PCR tests will be applied todiagnostics as applications are developed.Diagnostic Services Laboratory activity isrepresented by 5,107 accessions, 20,481 bacterialprocedures, 979 antimicrobial susceptibilities,56,832 enzyme-linked immunoadsorbentassay (ELISA), 17,632 infectious bronchitishemagglutination-inhibition (IBV-HI) tests,22,000 histopathology slides, 248 diagnosticPCR tests, and 579 necropsies.Stephan G. Thayer, R. Kenny Page, George N.Rowland, Thomas P. Brown, Jean E. Sander,John R. Glisson, Stanley H. Kleven, PedroVillegas, Stanley A. Vezeysthayer@arches.uga.eduIsolation, Identification, and Control ofAvian VirusesSeveral molecular techniques, includingpolymerase chain reaction (PCR), reverse transcriptase-polymerasechain reaction (RT-PCR),restriction fragment length polymorphism(RFLP), and in situ hybridization, were used toanalyze important sequences of the nucleicacid of field strains of infectious bursal diseasevirus (IBDV). One strain from Georgia wassimilar in sequence to Delaware E variantstrain, a second strain was similar to the GLSstrain also reported from the Delmarva area,and a third strain was similar to the pathogenicclassic standard strain. The results obtainedwere similar with all the molecular techniquesevaluated. Analysis of portions of the viralDr. Pedro Villegas examines a tissue culture for lesions associated with infectionof avian viruses.nucleic acid indicated that the genetic variationobserved among the IBDV isolates are due tonatural genetic drift rather than to selectivepressures.Four pathogenic adenoviruses isolatedfrom field cases associated with inclusion bodyhepatitis were classified as group E adenovirus,using restriction patterns of extractedviral DNA generated by the restriction endonucleasesBamHI and HindIII. These results confirmedthe pathogenicity of the isolates.A rapid method to identify strains ofinfectious bronchitis virus (IBV) has beendeveloped. Using neuraminidase to treat theallantoic fluid obtained from chicken embryos,a hemagglutination reaction indicates the presenceof the IBV. The method had a 98% correlationwhen compared with RT-PCR, which isconsiderably more expensive.Pedro VillegasPedrov@arches.uga.eduLarge Molecular Weight Plasmid Role inthe Pathogenesis of Avian E. coliFinancial losses due to colibacillosis costthe poultry industry hundreds of millions ofdollars annually. Virulence traits of bacterialorganisms are encoded by specific genes locatedon the bacterial chromosome or on largemolecular weight (MW) plasmids. Escherichiacoli strain V-1 (V-1 wt ) is a well characterized,pathogenic avian strain isolated from a broilerchicken with colisepticemia, which containsseveral plasmids, two of which are high MWplasmids.We are looking for a genetic marker (designatedepv) that indicates the putative virulencegene located on the virulence plasmid,pWT3 (of E. coli strain V-1), and we want todetermine what this virulence factor contributesto the mechanism of pathogenicity inavian disease. The organisms to be testedinclude E. coli strain V-1 wt , E. coli strain V-1 wt restored with the virulence gene, andappropriate positive and negative controls. Theability of the organisms to kill chicken embryonatedeggs will be used as a measure of virulencefor the organisms tested. Twelve-day-oldchicken embryos will be inoculated withapproximately 10 2 colony forming units(CFUs) of the appropriate isolate, which isdeposited into the allantoic fluid. In anotherprocedure, 10 2 CFUs will be inoculated intothe yolk sac of six-day-old embryos. Embryoswill be candled daily. The number of deathswill be recorded, and tissues will be taken forreisolation and histopathology. Previous statisticalanalysis has shown us the EmbryoLethality Assay performed with 20 embryos/group repeated at least three times is sufficientsampling for statistical analysis. Once the epvgene is delineated, we want to compare themechanism(s) of pathogenicity between thewild-type organism and the wild-type organ-