Brief communications
Acknowledgements. We thank the veterinary laboratory diagnosticians for referral of specimens, D. Nelson, J. Rivera, and R. Smith for technical assistance, and many USDA personnel, especially Drs. D. R. Cassidy, L. M. Siegfried, R. M. Nervig, A. Strating, and J. W. Glosser for assistance and counsel.
References 1. Barwick KW: 1990, Other intermediate filaments. In: Atlas of diagnostic immunohistopathology, ed. True LD, pp. 4.10-4.15. Gower Medical Publishing, New York, NY. 2. Davis AJ, Jenny AL, Miller LD: 1991, Diagnostic characteristics of bovine spongiform encephalopathy. J Vet Diagn Invest 3:266-271. 3. Hartsough GR, Burger D: 1965, Encephalopathy of mink. I. Epizootiologic and clinical observations. J Infect Dis 115:387392. 4. Horrigan JL: 1964, Scrapie in the United States and the scrapie eradication program. In: Report of scrapie seminar, pp. 340360, USDA, ARS, Washington, DC, January 27-30. 5. Luna L, ed.: 1968, Manual of histologic staining methods of
339
the Armed Forces Institute of Pathology, 3rd ed., pp. 203, 224. McGraw-Hill, New York, NY. 6. Wells GAH, Hancock RD, Cooley WA, et al.: 1989, Bovine spongiform encephalopathy: diagnostic significance of vacuolar changes in selected nuclei of the medulla oblongata. Vet Rec 125:521-524. 7. Wells GAH, Scott AC, Johnson CT, et al.: 1987, A novel progressive spongiform encephalopathy in cattle. Vet Rec 121:419420. 8. Wilesmith JW: 1991, Fall in BSE cases forecast. Vet Rec 129: 300-301. 9. Wilesmith JW, Ryan JBM, Atkinson MJ: 1991, Bovine spongiform encephalopathy: epidemiological studies on the origin. Vet Rec 128:199-203. 10. Wilesmith JW, Wells GAH, Cranwell MP, et al.: 1988, Bovine spongiform encephalopathy: epidemiologic studies. Vet Rec 123: 638-644. 11. Williams ES, Young S: 1980, Chronic wasting disease of captive mule deer: a spongiform encephalopathy. J Wild1 Dis 16:8998. 12. Williams ES, Young S: 1982, Spongiform encephalopathy of Rocky Mountain elk. J Wild1 Dis 18:465-471.
J Vet Diagn Invest 4:339-341 (1992)
Simplified characterization of pseudorabies viruses using monoclonal antibody and selective cell culture analyses Jonathan Bruce Katz, John George Landgraf All modified-live pseudorabies virus (PRV) vaccines (VPRV) used in the United States today contain glycoprotein gI (gI) gene deletions and/or deletions in the thymidine kinase (TK) gene (Table 1). 1,5,6,9,10 Typically, wild type pseudorabies viruses (WT-PRV) are both gI and TK positive.1,5,9,10 Companion diagnostic glycoprotein-specific enzyme-linked immunosorbent assay (ELISA) systems are available; these allow serologic differentiation between swine vaccinated with V-PRV and those exposed to WT-PRV.5,6,10 Definitive diagnostic differentiation between V-PRV and WT-PRV viruses themselves is, however, a complex process involving restriction endonuclease analysis (REA), Southern blotting with gene-specific DNA probes, and Western blotting with glycoprotein-specific antibodies.1,3 Differentiating between V-PRV and WT-PRV isolates is important for herd health and for regulatory and forensic purposes. Differentiation is also useful in epidemiologic studies and studies on viral latency and recrudescence and for evaluating the environmental behavior of vaccine viruses.3,4,6 We have developed a simple strategy to determine which isolates are typical WT-PRV and which cannot possibly be so, including atypical WT-PRV , V-PRV, and V-PRV that may have been
From the Diagnostic Virology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, IA 50010. Received for publication on August 22, 1991.
environmentally altered with respect to their gI or TK phenotypes. By grouping PRV isolates in this manner, authentic V-PRV, altered V-PRV, and atypical WT-PRV can be identified for more detailed differential diagnosis. Because all V-PRV are gI negative (gI-), TK negative (TK-), or both gI- and TK-, isolates that are gI and TK positive (gI+, TK+) cannot be V-PRV. Isolates that are (gI- and TK-), (gI- and TK+), and (gI+ and TK-) could theoretically be V-PRV, atypical WT-PRV, or V-PRV/WT-PRV recombinants.2,5 Determination of TK phenotype has been previously described.4,5 A sample of 104-106 plaque forming units (PFU) of each isolate was serially passaged 4 times at 2-3-day intervals in a TK mouse connective tissue cell linef (LMTK-, American Type Culture Collection Certified Cell Line 1.3) in the presence of methotrexate.g TK+ viruses propagated normally in these cells, but TK- viruses were selectively unable to do so. Reference TK+ and TK- PRVs were used as procedural controls. Following serial passage, culture supernatants were titrated for the presence of PRV in Madin Darby bovine kidney (MDBK) cells.4 TK+ viruses maintained viral titer, but TK- viruses were completely eliminated (0 PFU/ 0.1 m1).4,5 TK- results were always reconfirmed. Viral gI status was routinely assessed by examining 50-200 viral plaques in infected MDBK cell monolayers using 2 gI-specific but epitopically noncompetitive monoclonal antibodiesh,7 (MAbs) in an indirect fluorescent antibody test (IFAT) format. Both of these MAbs (7-3 and 8-2) were used separately on each isolate to improve the probability of detecting gI expression.
Downloaded from vdi.sagepub.com by guest on April 6, 2015
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Brief communications
Table 1. Phenotypic characterization of US-licensed modifiedlive pseudorabies virus vaccines.
Other gI-specific MAbsi,j were also found acceptable for assessment of gI status. Ninety-five diagnostic isolates were examined using the TK and gI tests (81 porcine, 8 bovine, 4 ovine, 2 canine). Three reference WT-PRV isolates and all US licensed V-PRVs were also evaluated (Table 2). Among the diagnostic isolates, 88 were TK+ and gI+, 5 were TK+ and gI-, 1 was TK- and gI-, and 1 was TK+ and gI+/- (MAb 7-3+, MAb 8-2-). Isolate Nos. 1-88 were classified as typical WT-PRV. Isolate Nos. 90-94 (TK+, gI-) were determined by REA as different from either of the 2 TK+, gI- V-PRV vaccine strains, indicating that they were either of atypical WT-PRV or alTable 2. Thymidine kinase (TK) and glycoprotein I (gI) classification of 95 diagnostic pseudorabies virus (PRV) isolates and PRV vaccine reference strains.
Figure 1. Hinf and Barn HI restriction endonuclease analyses of 4 atypical bovine origin pseudorabies virus (PRV) isolates. Isolate No. 89 originated in Illinois; isolate Nos. 90-92 originated in Iowa. Isolate No. 32 was a virulent wild type PRV swine isolate used for comparison.
tered V-PRV origin. The 2 atypical porcine isolates (Nos. 93, 94) differed by REA from each other and from the 3 atypical bovine isolates (Nos. 90-92). Isolate Nos. 90, 91, and 92 originated from the same Iowa cattle herd and had REA patterns indistinguishable from each other and from another atypical bovine isolate, No. 89 (TK-, gI-), which originated from Illinois (Fig. 1). Isolate Nos. 90-92 were not eliminated by serial propagation in LMTK- cells but were reduced in titer to approximately 102 PFU/0.1 ml. In contrast, reference TK+ viruses and isolate Nos. 1-88 titered 104-106 PFU/0.1 ml. Isolate Nos. 90-92 were doubly plaque purified, each in quadruplicate, and the resulting 12 viruses reconfirmed phenotypically with uniform results. Isolate No. 95 was TK+ and repeatedly IFAT positive with MAb 7-3 but negative with MAb 8-2. No V-PRV shares this profile (Tables 1, 2). A 27-kg PRV-seronegative pig inoculated intranasally with 102.5 PFU of isolate No. 95 developed severe clinical signs of PRV infection 5 days postinoculation (PI). Using a commercial gI-specific diagnostic ELISA test,k,7 gI+ seroconversion was detected 9 days PI and confirmed 19 days PI, indicating that isolate No. 95 was a virulent but atypical WT-PRV and that its degree of gI alteration did not preclude correct gI-specific serologic diagnosis. The TK-selective cell culture/gI IFAT analytic system correctly classified all US-licensed PRV vaccines as V-PRV. The great majority of current field isolates were TK+ and gI+. The minority with atypical TK and/or gI phenotypes must be studied further to differentiate them into unaltered V-PRV, potentially altered V-PRV, and atypical WT-PRV categories.1 The possibility of multiple strains in an isolate must be considered, and multiple analyses of plaque-purified isolates may be necessary if strain heterogeneity is suspected. No unaltered V-PRV was found in this study. Bovine herpesvirus 1 modified-live vaccines have under-
Downloaded from vdi.sagepub.com by guest on April 6, 2015
Brief communications
gone REA pattern alterations following only 1 passage through the host species.11 Some of the atypical WT-PRV identified in this study may have arisen in a similar manner. The similarities between the REA pattern of No. 89 and those of Nos. 90-92 suggests a possible iatrogenic V-PRV origin for these viruses. There is 1 report from Germany of a bovine origin PRV isolate with a pattern of split MAb reactivity similar to that found with isolate No. 95.8 In that study, the molecular basis of the unusual MAb reactivity was associated with a truncated form of gI.8 The simple phenotypic screening system described here will help identify those unusual isolates requiring further study to determine their possible origins and veterinary diagnostic significance.
Sources and manufacturers a. Boehringer Ingelheim Animal Health, St. Joseph, MO. b. SmithKline Beecham Animal Health, Lincoln, NE. c. The Upjohn Co., Kalamazoo, MI. d. Syntrovet, Lenexa, KS. e. Fermenta Animal Health Co., Kansas City, MO. f. American Type Culture Collection, Rockville, MD. g. Lederle Parenterals, Carolina, PR. h. Dr. N. Pfeiffer, SmithKline Beecham Animal Health, Inc., Lincoln, NE. i. Dr. Q. Tonelli, IDEXX Corp., Westbrook, ME. j. Dr. Tamar Ben-Porat, Vanderbilt University, Nashville, TN. k. ClinEase-PRV, SmithKline Beecham Animal Health, Inc., Lincoln, NE. The use of a particular manufacturer’s product does not constitute an endorsement on behalf of the USDA.
References
341
gene deleted vaccine strains of pseudorabies virus. Am J Vet Res 51:1656-1662. 2. Katz JB: 1990, A dual dominant selection, dual marker gene amplification model for environmental surveillance of recombinant viral vaccines. Res Virol 141:591-596. 3. Katz JB, Henderson LM, Erickson GA: 1990, Recombination in vivo of pseudorabies vaccine strains to produce new virus strains. Vaccine 8:286-288. 4. Katz JB, Middle LA: 1990, Evaluation of thymidine kinase and neomycin phosphotransferase II positive selection systems for recovery of genetically atypical and recombinant DNA vaccine viruses. Biologicals 18:301-304. 5. Kit S: 1990, Genetically engineered vaccines for control of Aujeszky’s disease (pseudorabies). Vaccine 8:420-424. 6. Kit S, Sheppard M, Ichimura H, et al.: 1987, Second generation pseudorabies virus vaccine with deletions in thymidine kinase and glycoprotein genes. Am J Vet Res 48:780-793. 7. Mellencamp MW, Pfeiffer NE, Suitor BT, et al.: 1989, Identification of pseudorabies virus-exposed swine with a gI glycoprotein enzyme-linked immunosorbent assay. J Clin Microbiol 27:2208-2213. 8. Mettenleiter TC, Schreurs C, Thiel HJ, et al.: 1987, Variability of pseudorabies virus glycoprotein I expression. Virology 158: 141-146. 9. Petrovskis EA, Timmins JG, Gierman TM, et al.: 1986, Deletions in vaccine strains of pseudorabies virus and their effect on synthesis of glycoprotein gp63. J Virol 60:1166-1169. 10. Wardley RC, Thomsen DR, Berlinski PJ, et al,: 1991, Immune responses in pigs to Aujeszky’s disease viruses defective in glycoprotein gI or gX. Res Vet Sci 50: 178-184. 11. Whetstone C, Miller J, Bortner D, et al.: 1989, Changes in the restriction endonuclease patterns of four modified-live infectious bovine rhinotracheitis virus (IBRV) vaccines after one passage in host animal. Vaccine 7:527-532.
1. Henderson LM, Katz JB, Erickson GA, et al.: 1990, In vivo and in vitro genetic recombination between conventional and
J Vet Diagn Invest 4:341-343 (1992)
Isolation of bovine herpesvirus 1 from preputial swabs and semen of bulls with balanoposthitis Rudi Weiblen, Luiz Carlos Kreutz, Terezinha Flores Canabarro, Luiz Filipe Schuch, Marlon Cezar Rebelatto Balanoposthitis is a disease of the reproductive tract and may be caused by bovine herpesvirus-1 (BHV-1).7 BHV-1infected animals, including those with nonapparent infection, 1 become lifelong carriers. Latent infection may be sporadically reactivated by natural mechanisms or by corticosteroid therapy.9 In bulls used for semen production, the potential for viral reactivation presents a special problem because semen can be contaminated with large quantities of virus8 From the Departamento de Medicina Veterinaria Preventiva da Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brasil. Received for publication October 31, 1991.
Contaminated semen presents a potential threat to the cattle population because BHV-1 can cause infectious pustular vulvovaginitis, endometritis, salpingitis, shortened estrous cycles, and abortions in susceptible female cattle8 and balanoposthitis in susceptible bulls.7 Because of the potential for bovine herpesvirus dissemination by semen, only seronegative bulls should be used as donors at artificial insemination stations.2 However, seronegativity provides no assurance that semen will be free of BHV-1 virus. Semen may have been contaminated by a primary preputial infection before production of antibodies; seronegative animals carrying latent infection have been reported.4-6 Cell culture inoculation test has been generally used
Downloaded from vdi.sagepub.com by guest on April 6, 2015
Acknowledgements. We thank the veterinary laboratory diagnosticians for referral of specimens, D. Nelson, J. Rivera, and R. Smith for technical assistance, and many USDA personnel, especially Drs. D. R. Cassidy, L. M. Siegfried, R. M. Nervig, A. Strating, and J. W. Glosser for assistance and counsel.
References 1. Barwick KW: 1990, Other intermediate filaments. In: Atlas of diagnostic immunohistopathology, ed. True LD, pp. 4.10-4.15. Gower Medical Publishing, New York, NY. 2. Davis AJ, Jenny AL, Miller LD: 1991, Diagnostic characteristics of bovine spongiform encephalopathy. J Vet Diagn Invest 3:266-271. 3. Hartsough GR, Burger D: 1965, Encephalopathy of mink. I. Epizootiologic and clinical observations. J Infect Dis 115:387392. 4. Horrigan JL: 1964, Scrapie in the United States and the scrapie eradication program. In: Report of scrapie seminar, pp. 340360, USDA, ARS, Washington, DC, January 27-30. 5. Luna L, ed.: 1968, Manual of histologic staining methods of
339
the Armed Forces Institute of Pathology, 3rd ed., pp. 203, 224. McGraw-Hill, New York, NY. 6. Wells GAH, Hancock RD, Cooley WA, et al.: 1989, Bovine spongiform encephalopathy: diagnostic significance of vacuolar changes in selected nuclei of the medulla oblongata. Vet Rec 125:521-524. 7. Wells GAH, Scott AC, Johnson CT, et al.: 1987, A novel progressive spongiform encephalopathy in cattle. Vet Rec 121:419420. 8. Wilesmith JW: 1991, Fall in BSE cases forecast. Vet Rec 129: 300-301. 9. Wilesmith JW, Ryan JBM, Atkinson MJ: 1991, Bovine spongiform encephalopathy: epidemiological studies on the origin. Vet Rec 128:199-203. 10. Wilesmith JW, Wells GAH, Cranwell MP, et al.: 1988, Bovine spongiform encephalopathy: epidemiologic studies. Vet Rec 123: 638-644. 11. Williams ES, Young S: 1980, Chronic wasting disease of captive mule deer: a spongiform encephalopathy. J Wild1 Dis 16:8998. 12. Williams ES, Young S: 1982, Spongiform encephalopathy of Rocky Mountain elk. J Wild1 Dis 18:465-471.
J Vet Diagn Invest 4:339-341 (1992)
Simplified characterization of pseudorabies viruses using monoclonal antibody and selective cell culture analyses Jonathan Bruce Katz, John George Landgraf All modified-live pseudorabies virus (PRV) vaccines (VPRV) used in the United States today contain glycoprotein gI (gI) gene deletions and/or deletions in the thymidine kinase (TK) gene (Table 1). 1,5,6,9,10 Typically, wild type pseudorabies viruses (WT-PRV) are both gI and TK positive.1,5,9,10 Companion diagnostic glycoprotein-specific enzyme-linked immunosorbent assay (ELISA) systems are available; these allow serologic differentiation between swine vaccinated with V-PRV and those exposed to WT-PRV.5,6,10 Definitive diagnostic differentiation between V-PRV and WT-PRV viruses themselves is, however, a complex process involving restriction endonuclease analysis (REA), Southern blotting with gene-specific DNA probes, and Western blotting with glycoprotein-specific antibodies.1,3 Differentiating between V-PRV and WT-PRV isolates is important for herd health and for regulatory and forensic purposes. Differentiation is also useful in epidemiologic studies and studies on viral latency and recrudescence and for evaluating the environmental behavior of vaccine viruses.3,4,6 We have developed a simple strategy to determine which isolates are typical WT-PRV and which cannot possibly be so, including atypical WT-PRV , V-PRV, and V-PRV that may have been
From the Diagnostic Virology Laboratory, National Veterinary Services Laboratories, Animal and Plant Health Inspection Service, US Department of Agriculture, Ames, IA 50010. Received for publication on August 22, 1991.
environmentally altered with respect to their gI or TK phenotypes. By grouping PRV isolates in this manner, authentic V-PRV, altered V-PRV, and atypical WT-PRV can be identified for more detailed differential diagnosis. Because all V-PRV are gI negative (gI-), TK negative (TK-), or both gI- and TK-, isolates that are gI and TK positive (gI+, TK+) cannot be V-PRV. Isolates that are (gI- and TK-), (gI- and TK+), and (gI+ and TK-) could theoretically be V-PRV, atypical WT-PRV, or V-PRV/WT-PRV recombinants.2,5 Determination of TK phenotype has been previously described.4,5 A sample of 104-106 plaque forming units (PFU) of each isolate was serially passaged 4 times at 2-3-day intervals in a TK mouse connective tissue cell linef (LMTK-, American Type Culture Collection Certified Cell Line 1.3) in the presence of methotrexate.g TK+ viruses propagated normally in these cells, but TK- viruses were selectively unable to do so. Reference TK+ and TK- PRVs were used as procedural controls. Following serial passage, culture supernatants were titrated for the presence of PRV in Madin Darby bovine kidney (MDBK) cells.4 TK+ viruses maintained viral titer, but TK- viruses were completely eliminated (0 PFU/ 0.1 m1).4,5 TK- results were always reconfirmed. Viral gI status was routinely assessed by examining 50-200 viral plaques in infected MDBK cell monolayers using 2 gI-specific but epitopically noncompetitive monoclonal antibodiesh,7 (MAbs) in an indirect fluorescent antibody test (IFAT) format. Both of these MAbs (7-3 and 8-2) were used separately on each isolate to improve the probability of detecting gI expression.
Downloaded from vdi.sagepub.com by guest on April 6, 2015
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Table 1. Phenotypic characterization of US-licensed modifiedlive pseudorabies virus vaccines.
Other gI-specific MAbsi,j were also found acceptable for assessment of gI status. Ninety-five diagnostic isolates were examined using the TK and gI tests (81 porcine, 8 bovine, 4 ovine, 2 canine). Three reference WT-PRV isolates and all US licensed V-PRVs were also evaluated (Table 2). Among the diagnostic isolates, 88 were TK+ and gI+, 5 were TK+ and gI-, 1 was TK- and gI-, and 1 was TK+ and gI+/- (MAb 7-3+, MAb 8-2-). Isolate Nos. 1-88 were classified as typical WT-PRV. Isolate Nos. 90-94 (TK+, gI-) were determined by REA as different from either of the 2 TK+, gI- V-PRV vaccine strains, indicating that they were either of atypical WT-PRV or alTable 2. Thymidine kinase (TK) and glycoprotein I (gI) classification of 95 diagnostic pseudorabies virus (PRV) isolates and PRV vaccine reference strains.
Figure 1. Hinf and Barn HI restriction endonuclease analyses of 4 atypical bovine origin pseudorabies virus (PRV) isolates. Isolate No. 89 originated in Illinois; isolate Nos. 90-92 originated in Iowa. Isolate No. 32 was a virulent wild type PRV swine isolate used for comparison.
tered V-PRV origin. The 2 atypical porcine isolates (Nos. 93, 94) differed by REA from each other and from the 3 atypical bovine isolates (Nos. 90-92). Isolate Nos. 90, 91, and 92 originated from the same Iowa cattle herd and had REA patterns indistinguishable from each other and from another atypical bovine isolate, No. 89 (TK-, gI-), which originated from Illinois (Fig. 1). Isolate Nos. 90-92 were not eliminated by serial propagation in LMTK- cells but were reduced in titer to approximately 102 PFU/0.1 ml. In contrast, reference TK+ viruses and isolate Nos. 1-88 titered 104-106 PFU/0.1 ml. Isolate Nos. 90-92 were doubly plaque purified, each in quadruplicate, and the resulting 12 viruses reconfirmed phenotypically with uniform results. Isolate No. 95 was TK+ and repeatedly IFAT positive with MAb 7-3 but negative with MAb 8-2. No V-PRV shares this profile (Tables 1, 2). A 27-kg PRV-seronegative pig inoculated intranasally with 102.5 PFU of isolate No. 95 developed severe clinical signs of PRV infection 5 days postinoculation (PI). Using a commercial gI-specific diagnostic ELISA test,k,7 gI+ seroconversion was detected 9 days PI and confirmed 19 days PI, indicating that isolate No. 95 was a virulent but atypical WT-PRV and that its degree of gI alteration did not preclude correct gI-specific serologic diagnosis. The TK-selective cell culture/gI IFAT analytic system correctly classified all US-licensed PRV vaccines as V-PRV. The great majority of current field isolates were TK+ and gI+. The minority with atypical TK and/or gI phenotypes must be studied further to differentiate them into unaltered V-PRV, potentially altered V-PRV, and atypical WT-PRV categories.1 The possibility of multiple strains in an isolate must be considered, and multiple analyses of plaque-purified isolates may be necessary if strain heterogeneity is suspected. No unaltered V-PRV was found in this study. Bovine herpesvirus 1 modified-live vaccines have under-
Downloaded from vdi.sagepub.com by guest on April 6, 2015
Brief communications
gone REA pattern alterations following only 1 passage through the host species.11 Some of the atypical WT-PRV identified in this study may have arisen in a similar manner. The similarities between the REA pattern of No. 89 and those of Nos. 90-92 suggests a possible iatrogenic V-PRV origin for these viruses. There is 1 report from Germany of a bovine origin PRV isolate with a pattern of split MAb reactivity similar to that found with isolate No. 95.8 In that study, the molecular basis of the unusual MAb reactivity was associated with a truncated form of gI.8 The simple phenotypic screening system described here will help identify those unusual isolates requiring further study to determine their possible origins and veterinary diagnostic significance.
Sources and manufacturers a. Boehringer Ingelheim Animal Health, St. Joseph, MO. b. SmithKline Beecham Animal Health, Lincoln, NE. c. The Upjohn Co., Kalamazoo, MI. d. Syntrovet, Lenexa, KS. e. Fermenta Animal Health Co., Kansas City, MO. f. American Type Culture Collection, Rockville, MD. g. Lederle Parenterals, Carolina, PR. h. Dr. N. Pfeiffer, SmithKline Beecham Animal Health, Inc., Lincoln, NE. i. Dr. Q. Tonelli, IDEXX Corp., Westbrook, ME. j. Dr. Tamar Ben-Porat, Vanderbilt University, Nashville, TN. k. ClinEase-PRV, SmithKline Beecham Animal Health, Inc., Lincoln, NE. The use of a particular manufacturer’s product does not constitute an endorsement on behalf of the USDA.
References
341
gene deleted vaccine strains of pseudorabies virus. Am J Vet Res 51:1656-1662. 2. Katz JB: 1990, A dual dominant selection, dual marker gene amplification model for environmental surveillance of recombinant viral vaccines. Res Virol 141:591-596. 3. Katz JB, Henderson LM, Erickson GA: 1990, Recombination in vivo of pseudorabies vaccine strains to produce new virus strains. Vaccine 8:286-288. 4. Katz JB, Middle LA: 1990, Evaluation of thymidine kinase and neomycin phosphotransferase II positive selection systems for recovery of genetically atypical and recombinant DNA vaccine viruses. Biologicals 18:301-304. 5. Kit S: 1990, Genetically engineered vaccines for control of Aujeszky’s disease (pseudorabies). Vaccine 8:420-424. 6. Kit S, Sheppard M, Ichimura H, et al.: 1987, Second generation pseudorabies virus vaccine with deletions in thymidine kinase and glycoprotein genes. Am J Vet Res 48:780-793. 7. Mellencamp MW, Pfeiffer NE, Suitor BT, et al.: 1989, Identification of pseudorabies virus-exposed swine with a gI glycoprotein enzyme-linked immunosorbent assay. J Clin Microbiol 27:2208-2213. 8. Mettenleiter TC, Schreurs C, Thiel HJ, et al.: 1987, Variability of pseudorabies virus glycoprotein I expression. Virology 158: 141-146. 9. Petrovskis EA, Timmins JG, Gierman TM, et al.: 1986, Deletions in vaccine strains of pseudorabies virus and their effect on synthesis of glycoprotein gp63. J Virol 60:1166-1169. 10. Wardley RC, Thomsen DR, Berlinski PJ, et al,: 1991, Immune responses in pigs to Aujeszky’s disease viruses defective in glycoprotein gI or gX. Res Vet Sci 50: 178-184. 11. Whetstone C, Miller J, Bortner D, et al.: 1989, Changes in the restriction endonuclease patterns of four modified-live infectious bovine rhinotracheitis virus (IBRV) vaccines after one passage in host animal. Vaccine 7:527-532.
1. Henderson LM, Katz JB, Erickson GA, et al.: 1990, In vivo and in vitro genetic recombination between conventional and
J Vet Diagn Invest 4:341-343 (1992)
Isolation of bovine herpesvirus 1 from preputial swabs and semen of bulls with balanoposthitis Rudi Weiblen, Luiz Carlos Kreutz, Terezinha Flores Canabarro, Luiz Filipe Schuch, Marlon Cezar Rebelatto Balanoposthitis is a disease of the reproductive tract and may be caused by bovine herpesvirus-1 (BHV-1).7 BHV-1infected animals, including those with nonapparent infection, 1 become lifelong carriers. Latent infection may be sporadically reactivated by natural mechanisms or by corticosteroid therapy.9 In bulls used for semen production, the potential for viral reactivation presents a special problem because semen can be contaminated with large quantities of virus8 From the Departamento de Medicina Veterinaria Preventiva da Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brasil. Received for publication October 31, 1991.
Contaminated semen presents a potential threat to the cattle population because BHV-1 can cause infectious pustular vulvovaginitis, endometritis, salpingitis, shortened estrous cycles, and abortions in susceptible female cattle8 and balanoposthitis in susceptible bulls.7 Because of the potential for bovine herpesvirus dissemination by semen, only seronegative bulls should be used as donors at artificial insemination stations.2 However, seronegativity provides no assurance that semen will be free of BHV-1 virus. Semen may have been contaminated by a primary preputial infection before production of antibodies; seronegative animals carrying latent infection have been reported.4-6 Cell culture inoculation test has been generally used
Downloaded from vdi.sagepub.com by guest on April 6, 2015
