Emerging Diseases - University of Georgia College of Veterinary ...

lymphocytes. Heterophils incorporated proviralDNA and had decreased ability to protectagainst bacterial infections. Studies ofmacrophages are in progress. These heterophiland macrophage results may explain theincreased incidence of secondary infections.Our last objective was to produce antibodies touse as potential therapies and to detect thevirus in tissue samples. These studies arecurrently in progress.Thomas P. Brown, Nancy L. Stedman, Saad M.Gharaibeh, Yong-Baek Kim, and Mary J.Pantin-Veratbrown@arches.uga.eduDifferential diagnosis of infectiouslaryngotracheitis virus by PCRInfectious laryngotracheitis virus (ILTV)is a severe acute respiratory disease ofchickens. ILT outbreaks cause severe financiallosses to the poultry industry; however, thedirect source of these outbreaks is quitedifficult to determine. The wide use ofattenuated vaccines and the homogenousantigenicity of ILTV strains have made itdifficult to understand the epidemiology of thedisease. We have developed a polymerasechain reaction (PCR) and restriction fragmentlength polymorphism (RFLP) assay of theglycoprotein E to easily characterize fieldisolates of ILTV. RFLP analysis of the gEgene showed three different patterns amongvaccine strains and field isolates with enzymesDdeI and PleI. Pattern A was observed for thetissue culture origin (TCO) vaccine as well asfield isolates, whereas pattern B was observeduniquely for field isolates. However, chickenembryo origin (CEO) vaccines showed RFLPpatterns including bands corresponding to bothA and B. This was observed for threecommercially available CEO vaccines and fivefield isolates. The above may indicate that amixed population of viruses may be present insome of these vaccine strains. To determine thepotential of gE PCR-RFLP assay to trace ILTVsources outbreaks, 25 field isolates wereanalyzed. RFLP analysis with DdeI enzymeshowed that 21/25 were TCO-like or A pattern,1/25 was CEO-like or A+B pattern, whereas3/25 isolates have a unique or B pattern. RFLPanalysis with PleI showed 15/25 isolates with aTCO-like or A pattern, 5/25 isolates wereCEO-like or A+B pattern, and 5/25 isolateshad a unique or B pattern. Although most ofthe tested viruses were isolated from unvaccinatedflocks, 88% of the field isolates wereeither TCO-like or CEO-like.Maricarmen Garcíamcgarcia@arches.uga.eduClinical investigation of poultry diseasesThe clinical teaching program is used bylocal poultry companies as a means tocritically evaluate management and diseaseissues on farms that have been designated asproblem farms. Problem farms typically have ahistory of poor performance withoutimmediately obvious reasons. This past year,we investigated three such farms, one each forthree different broiler integrators. All threeinvestigations used methods to evaluate water,litter, air, temperature, and managementfactors. Moreover, disease challenge andresulting pathology were evaluated. In allcases, constructive recommendations weremade and implemented.One particular broiler integrator has beenstruggling to cope with an apparentlysignificant issue of immunosuppression inbroilers. The evidence for immunosuppressionis a high incidence of inclusion body hepatitis,gangrenous dermatitis, and vaccine-inducedrespiratory disease in broilers. This conclusionis supported by the observation of lymphoidorgan atrophy at an early age in broilers. Wehypothesized that infectious bursal diseasevirus (IBDV) was infecting broilers early andthat the offending virus must be antigenicallyunusual to accomplish an early infection. Incooperation with the broiler company, Dr.Daral Jackwood, and Dr. Pedro Villegas, weplaced sentinel birds on 25 broiler farms.IBDVs were isolated from each farm andModern tissue culture techniques are used to study avian viruses in thelaboratory.7