Isolation and characterization of encephalitic bovine herpesvirus type 1 isolates from cattle in North America

Jean M. d’Offay From the Department of Veterinary Parasitology, Microbiology and Public Health, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078 (d’Offay, Fulton), and from the Texas Veterinary Medical Diagnostic Laboratory, Amarillo, TX 79116 (Mock).

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Richard E. Mock From the Department of Veterinary Parasitology, Microbiology and Public Health, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078 (d’Offay, Fulton), and from the Texas Veterinary Medical Diagnostic Laboratory, Amarillo, TX 79116 (Mock).

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Robert W. Fulton From the Department of Veterinary Parasitology, Microbiology and Public Health, College of Veterinary Medicine, Oklahoma State University, Stillwater, OK 74078 (d’Offay, Fulton), and from the Texas Veterinary Medical Diagnostic Laboratory, Amarillo, TX 79116 (Mock).

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Summary

Nine cns bovine herpesvirus type 1 (bhv-1) isolates, recovered from bovine brain samples submitted to the Texas Veterinary Medical Diagnostic Laboratories from 1974-1989, were compared by analyzing their dna restriction endonuclease (re) fragment migration pattern. Seven had pattern similar to that of the respiratory bhv-1 Cooper strain. The remaining 2 isolates, however, had variant patterns, similar to that of each other, but completely different from patterns for the other 7. The re patterns of these 2 variants were similar to published re patterns for 2 encephalitic or neuropathogenic bhv-1 strains — the Australian N-569 strain and the Argentine A-663 strain. One of the Texas encephalitic variants (No. 30326) was isolated from the cns of a calf that died during an epizootic of encephalitis in 1974. The other, designated TX-89, was isolated in 1989 from the cns of a 7-month-old feedlot steer with acute fatal encephalitis. Microscopic lesions of encephalitis with neuronal degeneration and intranuclear inclusions were observed for 3 of the 9 isolates, the 2 variant isolates (No. 30326 and TX-89), and a respiratory isolate. The remaining 6 cns isolates, all respiratory subtypes, were recovered from cattle that did not have clinical cns disease or gross or microscopic cns lesions; in 5 of these cattle, virus was recovered from at least 1 other organ (lungs) besides the cns. We conclude that the cns of calves can be naturally infected with 2 distinct bhv-1 subtypes, the respiratory and the encephalitic, and that the encephalitic subtype (subtype 3 or bhv-1.3) has been present in Texas cattle since at least 1974.

Summary

Nine cns bovine herpesvirus type 1 (bhv-1) isolates, recovered from bovine brain samples submitted to the Texas Veterinary Medical Diagnostic Laboratories from 1974-1989, were compared by analyzing their dna restriction endonuclease (re) fragment migration pattern. Seven had pattern similar to that of the respiratory bhv-1 Cooper strain. The remaining 2 isolates, however, had variant patterns, similar to that of each other, but completely different from patterns for the other 7. The re patterns of these 2 variants were similar to published re patterns for 2 encephalitic or neuropathogenic bhv-1 strains — the Australian N-569 strain and the Argentine A-663 strain. One of the Texas encephalitic variants (No. 30326) was isolated from the cns of a calf that died during an epizootic of encephalitis in 1974. The other, designated TX-89, was isolated in 1989 from the cns of a 7-month-old feedlot steer with acute fatal encephalitis. Microscopic lesions of encephalitis with neuronal degeneration and intranuclear inclusions were observed for 3 of the 9 isolates, the 2 variant isolates (No. 30326 and TX-89), and a respiratory isolate. The remaining 6 cns isolates, all respiratory subtypes, were recovered from cattle that did not have clinical cns disease or gross or microscopic cns lesions; in 5 of these cattle, virus was recovered from at least 1 other organ (lungs) besides the cns. We conclude that the cns of calves can be naturally infected with 2 distinct bhv-1 subtypes, the respiratory and the encephalitic, and that the encephalitic subtype (subtype 3 or bhv-1.3) has been present in Texas cattle since at least 1974.

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