A comparison of the virulence of three strains of infectious bovine rhinotracheitis virus

The virulence of three strains of infectious bovine rhinotracheitis (IBR) virus was compared in six-month-old Ayrshire-cross calves. The strains were an isolate from a recent severe outbreak of IBR in Scotland (Strichen strain), the prototype British strain (Oxford strain) and a North American isolate (Colorado strain). The Colorado and Strichen strains produced the characteristic clinical signs and pathological lesions of severe IBR three to four days post infection (p.i.). The Strichen strain was slightly more virulent, possibly as a result of its having been passaged fewer times in tissue culture. In contrast, the Oxford strain produced a mild clinical response with minimal pathological lesions. Virus was recovered from nasal swabs for a longer period from the calves infected with the Strichen strain (up to 13 days p.i.) and Colorado strain (up to 12 days p.i.) than from the animals infected with the Oxford strain (up to 10 days p.i.). These findings support the suggestion that the recent epidemic of severe IBR in Britain had resulted from the importation of a “new” strain of virus.     

Enhancement of infectious bovine keratoconjunctivitis by modified-live infectious bovine rhinotracheitis virus vaccine

The effects of a modified-live infectious bovine rhinotracheitis virus vaccine (administered ocularly or intranasally) on experimentally induced infectious bovine keratoconjunctivitis were evaluated. The modified-live infectious bovine rhinotracheitis virus vaccine was administered to 13 male Holstein calves (intranasally in 4 and ocularly in 9; day 0). Five calves were not vaccinated and served as controls. Calves were examined daily and, starting on day 4, Moraxella bovis was administered ocularly to all 18 calves once daily for 4 days. The eyes of all calves were assigned a clinical score, and the ocular secretions were evaluated for presence of infectious bovine rhinotracheitis virus and M bovis daily until day 19. The severity of the ocular lesions was estimated by scoring the lesions clinically and by determining the protein concentration, myeloperoxidase activity, and WBC count in the tears. By day 5, conjunctivitis, chemosis, and epiphora were observed in all of the calves vaccinated ocularly. The calves vaccinated intranasally developed conjunctival plaques, but did not develop chemosis or photophobia. All of the calves developed keratitis after inoculation with M bovis. The median lesion scores were greater in both groups of vaccinated calves than in the controls. Corneal perforations developed exclusively in the vaccinated calves. The frequency of M bovis isolation from ocular secretions was significantly (P less than 0.05) greater in the vaccinated calves than in the controls. The tears from the intranasally vaccinated calves contained the highest myeloperoxidase activity and WBC count. The mean protein concentration in the tears of vaccinated calves was not significantly different from that in tears of controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of infectious bovine rhinotracheitis virus in Tanzania

Summary Infectious bovine rhinotracheitis (IBR) virus was identified for the first time in Tanzania. The virus isolations were made from cattle affected with respiratory diseases. Concurrent infection with foot-and-mouth disease was observed and enhanced the severity of the illness.

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Sumario El virus de la rinotraqueitis infecciosa de los bovinos (I.B.R.) ha sido identificado por primera vez en Tanzania. Los aislamientos de virus fueron hechos de bovinos afectados con enfermedades respiratorias. Se observó infección concurrente con fiebre aftosa y este hecho exacerbaba la severidad de la enfermedad.

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Résumé Ce virus a été isolé pour la première fois en Tanzanie, à partir de bétail atteint d'affections respiratoires. Cette maladie a sévi concurremment avec la fièvre aphteuse, ce qui explique sa sévérité.

     

Reactivation of infectious bovine rhinotracheitis virus by transport

Transport was studied as a cause of reactivation of infectious bovine rhinotracheitis virus (Bovine herpesvirus-1; BHV-1) in heifers vaccinated 2-6 months before transport, using a double dose of the thermosensitive (ts) vaccine strain (Tracherine). Eight out of 19 animals showed ts strain re-excretion over a period of 1-3 days, beginning, in 5 out of the 8 heifers, the day after transport. In 14 other heifers, only sera were examined by sero-neutralisation: only 1 out of these 14 animals showed a rise in BHV-1 neutralising antibodies. Transport can therefore be considered as a stimulus of BHV-1 reactivation.     

Survival of infectious bovine rhinotracheitis virus in stored bovine semen

No loss in the titre of infectious bovine rhinotracheitis virus was found during storage in semen at –196°C for 1 year.     

Comparative studies of strains of infectious bovine rhinotracheitis virus isolated from latently infected calves

Three strains (479 C, 778 TL, 982 LE) of infectious bovine rhinotracheitis (IBR) virus isolated from latently infected calves were compared with the prototype strain of IBR virus (LA strain) in studies which included restriction endonuclease analysis, experimental infection, and reciprocal cross protection tests in cattle. From the restriction endonuclease analysis it appeared that the 3 "latent" viruses were derived from the same isolate, and that it differed slightly from the LA strain. However, latency does not seem to have affected the pathogenicity or the immunogenicity of the virus. This is demonstrated by the identical clinical and virologic response of calves subjected to experimental infection with the various strains under study, and by the finding that when the LA strain and a "latent" strain (982 LE) were tested in cross protection tests in cattle, they proved to be mutually protective.     

新疆阿克苏地区牛传染性鼻气管炎病毒与牛副流感病毒3型感染的检测

为调查阿克苏地区是否存在牛传染性鼻气管炎病毒(IBRV)与牛副流感病毒3型(BPIV-3)的感染,从阿克苏两个规模化奶牛场采集1月龄以内可疑发病犊牛鼻液样品18份,采用双抗体夹心ELISA方法检测两种病毒的抗原,PCR方法检测牛传染性鼻气管炎病毒gD基因,RT-PCR方法检测牛副流感病毒3型的gM基因。结果表明,ELISA方法检测IBRV和BPIV-3的感染率分别为22.22%和0%;PCR方法检测IBRV的感染率为72.22%;RT-PCR检测BPIV-3的感染率为44.44%;同时患有两种病毒的检出率为22.22%。说明在阿克苏地区存在IBRV与BPIV-3的感染,且存在两种病毒的双重感染。     

Nitrogen metabolism of calves inoculated with bovine adenovirus-3 or with infectious bovine rhinotracheitis virus

Beef calves were inoculated with bovine adenovirus-3 or infectious bovine rhinotracheitis virus. After inoculation, plasma fibrinogen increased, serum phosphorus decreased, and nitrogen and phosphorus digestibility decreased compared with preinoculation values. Urinary N excretion increased when calves developed rectal temperatures greater than 39.7 C. Results indicated that clinical infection of calves with infectious bovine rhinotracheitis virus increases urinary N excretion and reduces N and phosphorus balance, and that clinical and subclinical infections with either virus reduce dietary N digestibility.     

Enhancement of infectious bovine rhinotracheitis virus replication with corticosterone

Infectious bovine rhinotrachetis virus (IBRV) progeny was increased ten to 12 fold in bovine turbinate (BT) cells treated with 10^?3 M corticosterone acetate (CCA) as demonstrated by plaque assay. Autoradiographic studies demonstrated an increased binding of ³H-corticosterone (³H-CS) in IBRV infected cells and the fractionation of labelled cells revealed 78–80% of the total hormone associated with the cytoplasmic components. Incorporation of ³H-uridine and ³H-valine precursors into cells treated with the hormone demonstrated up to 16-fold increase in RNA and protein synthesis which was inhibited by the addition of actinomycin D. The data suggest that increased rate of macromolecular synthesis in IBRV infected cells treated with the corticosteroid may result in the enhancement of virus production.     

Experimental infectious bovine rhinotracheitis virus infections of English ferrets (Mustela putorius furo L).

Intranasal and intraperitoneal exposure of English ferrets (Mustela putorius furo L) to infectious bovine rhinotracheitis virus caused acute and chronic infections of the respiratory tract. The clinical syndrome was characterized by sneezing, coughing, and anorexia from postexposure days (PED) 3 to 7. Mucopurulent exudate was observed in the posterior nares and pharyngeal area of ferrets euthanatized on PED 4 and 8. The virus was readily recovered from the turbinates, respiratory tract epithelium of the pharynx, retropharyngeal lymph nodes, trachea, lungs, and spleen of animals euthanatized on PED 4, but only from the respiratory tract epithelium of the pharynx in ferrets euthanatized on PED 8 and 12. Results of histopathologic studies revealed an acute suppurative pharyngitis in animals euthanatized on PED 4 and 8. Recrudescence of chronic infection could be elicited by daily intraperitoneal injections of 4.0 mg of dexamethasone. However, daily administration of 2.0 mg of dexamethasone intraperitoneally did not cause more severe clinical disease. Results of serologic studies revealed serum antibody profiles comparable with those expected in experimentally exposed cattle.