Experimentally induced infectious bovine rhinotracheitis virus infection during early pregnancy: effect on the bovine corpus luteum and conceptus

Pairs of heifers were inoculated IV with infectious bovine rhinotracheitis virus on postbreeding days (PBD) 7, 14, 21, or 28, and were euthanatized 13 to 15 days after inoculation. Reproductive tracts were examined for cytopathologic changes (light microscopy), virus (cell culture), and viral antigen (immunohistochemical evaluation). Heifers inoculated on PBD 7 or 14 had mild oophoritis characterized by foci of necrosis and mononuclear cell accumulations in the corpus luteum. Most of these heifers also had a few necrotic follicles in at least one ovary. Heifers inoculated on PBD 21 or 28 did not have corpus luteum lesions, but necrotic follicles were numerous in both ovaries. Viral antigen was observed in all ovarian lesions, and infectious virus was isolated from a few of the affected tissues. The uteri of all heifers inoculated on PBD 21 or 28 and 1 heifer inoculated on PBD 7 contained normal-appearing concepti. The uterus of the other PBD 7 heifer contained a degenerating conceptus that was infected with infectious bovine rhinotracheitis virus, as determined by viral isolation, immunohistochemical evaluation, and electron microscopy. Heifers inoculated on PBD 14 were not pregnant at necropsy, but histologic evidence was found that the postbreeding estrous cycle had been longer than normal, indicating that early embryonic death had occurred.     

Ovarian lesions in heifers exposed to infectious bovine rhinotracheitis virus by non-genital routes on the day after breeding

Twelve heifers were exposed to either a Colorado infectious bovine rhinotracheitis (IBR) virus isolate or an Iowa IBR isolate obtained from a bovine respiratory disease outbreak. All inoculations were made on the day after the heifers had been in estrus and bred by an IBR virus-negative bull. Pairs of heifers were inoculated with each virus isolate intravenously, intramuscularly or exposed by aerosol. The heifers were killed 11-15 days after inoculation and their reproductive tracts and ovaries subjected to virological and pathological study. Virus was isolated from the ovaries of all 4 heifers inoculated intravenously and from 3 of the 4 heifers inoculated intramuscularly, but not from the ovaries of heifers exposed by aerosol. Virus isolations and lesions were, with only 1 exception, confined to the ovary containing the corpus luteum. In ovaries from which IBR virus was isolated, lesions in the corpus luteum ranged from focal necrosis and infiltration of mononuclear cells to diffuse hemorrhage and necrosis. Most of these ovaries also had necrotic follicles and a diffuse mononuclear cell accumulation in the stroma. Lesions were not found in ovaries from which IBR virus was not isolated. It was concluded that lesions are readily induced in the ovaries of post-estrus heifers as a result of hematogenous spread of IBR virus and suggest that the differences in lesion development observed with the 3 routes are related to whether or not a viremia occurred.     

Infertility in heifers inoculated with modified-live bovine herpesvirus-1 vaccinal strains against infectious bovine rhinotracheitis on postbreeding day 14

Heifers were inoculated IV with 1 of 4 modified-live bovine herpesvirus-1 vaccinal strains against infectious bovine rhinotracheitis (2 heifers/strain) on postbreeding day (PBD) 14. The effect of infection on fertility was monitored by plasma progesterone assay at 1- to 3-day intervals from the time of virus exposure until PBD 60. Infertility was detected in 4 of 8 inoculated heifers. In 2 heifers, progesterone concentrations decreased to values indicative of estrus within 10 days after inoculation (PBD 24). The 2 other heifers had evidence of embryonic death on PBD 40 and 42. Two control heifers inoculated with culture medium from noninfected cells maintained their pregnancies.     

Effect of primary and recurrent infections bovine rhinotracheitis virus infection on the bovine ovary

Six heifers were inoculated IV at estrus with the Iowa or Colorado isolates of infectious bovine rhinotracheitis virus (IBRV). Subsequent measurements of plasma progesterone indicated that corpus luteum function was depressed in all heifers. In the 1st estrous cycle after inoculation, progesterone values did not exceed 2 ng/ml in 3 heifers given the Iowa isolate. Although maximal progesterone values were greater than or equal to 2 ng/ml in 3 heifers given the Colorado isolate, values were lower than those in later cycles. Five heifers had maximal diestrual progesterone values greater than or equal to 5 ng/ml within 5 weeks after inoculation, but in the 6th heifer, this amount of progesterone was not present until 8 weeks after inoculation. Three to 5 months after inoculation, all heifers were given 5 daily injections of dexamethasone, 2 heifers each during metestrus, diestrus, or proestrus. Subsequent recrudescence of IBRV was demonstrated in all heifers by the isolation of virus from vaginal or nasal swab samples. The heifers were killed 10 to 17 days after initiation of dexamethasone treatment and their reproductive organs were examined for lesions and IBRV. Lesions were not seen, and IBRV was isolated only from the corpus luteum of a heifer given dexamethasone during diestrus.     

Infection of bovine fetuses at 120 days' gestation with virulent and avirulent strains of bluetongue virus serotype 11.

Bluetongue virus infection in sheep and cattle during fetal development causes neuropathology. Two strains of bluetongue virus serotype 11 designated as UC-2 and UC-8 have different virulence patterns in newborn mice. These viruses have distinctly different electropherotype patterns on polyacrylamide gel electrophoresis indicating a genetic difference in these two viruses of the same serotype. Four bovine fetuses each were inoculated intramuscularly with either UC-2 or UC-8, and one fetus was inoculated with placebo. The inoculation was made intramuscularly through the uterine wall at 120 days' gestation, and the bovine fetuses were recovered by cesarean section 12 or 20 days after inoculation. Fetal blood was collected for virus isolation and serology. Virus was reisolated from brain, blood, lung and liver. Both strains, UC-2 and UC-8, cause severe lesions in the 120 day fetuses. The encephalomalacic lesions occurred earlier and were more severe in fetuses inoculated with UC-8 as compared to those inoculated with UC-2. The subtle differences observed in the fetuses inoculated with the two different strains suggest that there is a difference in pathogenic potential of the two viruses. These differences do not appear to be completely dependent upon the host species.     

Reproductive tract lesions in heifers after intrauterine inoculation with infectious bovine rhinotracheitis virus

Cross-breed heifers given infectious bovine rhinotracheitis virus by intrauterine inoculation 1 day after natural mating with a noninfected bull were killed on postinoculation days 4 to 14. When reproductive organs were examined for gross and microscopic lesions and for virus infection, the most severe uterine lesions were found in the body and caudal portions of the uterine horns of heifers killed between postinoculation days 4 and 9. Primary pathologic features were necrosis, edema, hemorrhage, and a diffuse accumulation of mononuclear cells, mostly lymphocytes; numerous lymphocytes were in mitosis. In cranial parts of uterine horns, the only lesions observed were a few small lymphocytic foci in the endometrial lamina propria. Lesions were not seen in the oviducts. In many heifers, the ovarian corpus luteum (CL) was cystic. In a few of these heifers, the cyst had a necrotic wall that was bordered by a zone of proliferating mononuclear cells. Focal necrosis and lymphoid proliferation were common in the parenchyma of cystic and noncystic CL. Similar necrotizing lesions were sometimes present in non-CL ovarian tissue. Infectious bovine rhinotracheitis virus was most frequently isolated from the uterine body, the internal os of the cervix, and the CL. Isolations were not made from blood samples taken at the time of necropsy. Isolation of virus from the CL correlated with the detection of luteal inflammation by light microscopy, but did not correlate with the presence of cysts. There also was no correlation between cystic CL and the severity of uterine lesions.     

Association between route of inoculation with infectious bovine rhinotracheitis virus and site of recrudescence after dexamethasone treatment

Four calves latently infected with infectious bovine rhinotracheitis virus (IBRV) were used to compare the ease of isolation of virus from neuronal ganglia and from mucosal surfaces. Two calves were slaughtered, and neuronal ganglia (cranial cervical, trigeminal, and 3rd and 4th sacral) were cocultivated on bovine fetal kidney cells. Virus was not isolated. Two calves given dexamethasone for 4 days were slaughtered on the 5th day. Virus was not isolated from cocultivated or macerated neuronal ganglia, but virus was isolated from nasal secretions taken from both calves on the day of slaughter. Eleven calves were inoculated with IBRV via different routes and were treated with dexamethasone 3 to 4 months after inoculation. virus was isolated from the nasal cavities, but not the vaginas of 6 heifers inoculated intranasally, and was isolated from the vaginas, but not the nasal cavities of 2 heifers inoculated intravaginally. Of 3 calves inoculated IV, virus was isolated from the nasal cavities of 3, from the oropharynxes of 2, and from the prepuce of 1.     

The isolation and characterization of a strain of infectious bovine rhinotracheitis virus from stillbirth in swine.

A virus, designated 5089, which was isolated from tissue samples from two stillborn pig fetuses was identified on the basis of its morphology, cytopathology, physiocochemical and serological characteristics as a strain of infectious bovine rhinotracheitis (IBR) virus. Three piglets inoculated intranasally with 5089 virus did not respond serologically and no virus was isolated from their tissues at intervals after inoculation. They showed neither clinical signs nor significant lesions. A colostrum deprived calf which was inoculated intranasally with the same virus developed clinical signs typical of the respiratory form of IBR and the virus was reisolated on several occasions from nasal swabs.     

A Histological Study of the Effects of Enzootic Abortion of Ewes Virus in the Lactating Bovine Mammary Gland

Inoculation of the udders of cows with the virus of enzootic abortion of ewes resulted in a severe acute mastitis. The mastitis was characterized clinically by pyrexia, anorexia, decreased milk production, swelling and marked alteration in the physical quality of the milk. The basic lesion was necrosis of alveolar and duct epithelial cells. Virus particles were demonstrated in all levels of the mammary gland three days after inoculation illustrating the rapid spread of the agent. Cells resembling Reed-Sternberg cells and similar to those seen in experimental mastitis produced by the virus of infectious bovine rhinotracheitis were seen in tissues collected six and nine days after inoculation.     

Necrotic oophoritis in heifers vaccinated intravenously with infectious bovine rhinotracheitis virus vaccine during estrus

Twenty-two Hereford heifers were injected IM with prostaglandin F2 alpha a, 11 days apart to synchronize estrous cycles. Twelve of 14 heifers that had signs of estrus were inoculated IV with 1 of 3 modified-live infectious bovine rhinotracheitis virus vaccines, and 2 were assigned to a nonvaccinated control group. Also, 6 of the 8 anestrous heifers were inoculated IV with 1 of the 3 vaccines on the fourth day after the last prostaglandin injection and the other 2 were assigned to the nonvaccinated group. Vaccine virus was isolated from the blood and nasal and vaginal secretions from the vaccinated heifers on postvaccination days 4, 7, and 9. On postvaccination day 9, all heifers were ovariectomized and ovarian tissues were processed for virus isolation and histologic examination. Vaccine virus was isolation and histologic examination. Vaccine virus was isolated from ovarian tissues of some heifers in each of the vaccine groups. Necrotic oophoritis characterized by multifocal areas of ovarian tissue necrosis, hemorrhage, and mononuclear lymphocytic infiltration was observed. The corpora lutea and surrounding ovarian tissues taken from vaccinated heifers in each group had varying amounts of necrotic and inflammatory change, but the changes appeared to be more severe in 1 group than in the other 2. Virus also was isolated from 2 of the controls; these heifers apparently became infected with vaccine virus that had been excreted from the vaccinated animals.     

Evaluation of the rabbit as a laboratory model for infectious bovine rhinotracheitis virus infection

Experimental infection of rabbits with infectious bovine rhinotracheitis virus (IBRV) produced diverse manifestations of disease which included abortion, conjunctivitis, dermatitis, vulvovaginitis, systemic infection, neonatal death and respiratory tract infection. Each disease syndrome was studied using virus isolation, fluorescent antibody examination and histologic examination. Conjunctivitis, dermatitis and vulvovaginitis lesions were characterized by edema, infiltration of mucosa and submucosa with inflammatory cells and ulceration of epithelium. Systemic infection resulted in severe necrosis of liver and adrenal glands with large numbers of cells containing intranuclear inculsions. Pregnant rabbits aborted within 48 hours following inoculation of IBRV. Virus infection and viral lesions were not demonstrated in aborted fetuses.     

Infectious bovine keratoconjunctivitis II. Antibodies in lacrimal secretions of cattle naturally or experimentally infected with Moraxella bovis.

One or both eyes of 20 calves were inoculated one or more time with variou(s combinations of microorganism (live oor killed Moraxella bovis, infectious bovine rhinotracheitis virus, bovine adenovirus, bovine parainfluenza-3 virus and Mycoplasma bovoculi) by conjunctival instillation or direct inoculation of the conjunctivea or cornea. The eyes of all the calves received natural or artificial ultraviolet irradiation. Neither the adenovirus nor parainfluenza-3 virus became established in the eye or produced keratoconjunctivitis. Both M. bovis and infectious bovine rhinotracheitis virus became established in the bovine eye and produced disease. Subconjunctival or intracorneal inoculation of M. bovis caused a severe disease, simulating natural infectious bovine keratoconjunctivitis. Only the intracorneal inoculation of mycoplasma produced severe keratoconjunctivits. Eyes that on initial exposure to M. bovis became severly inflamed were more resistant to a second or third exposure to M. bovis, presumably by enhanced local defence mechanisms.     

Reaction of goats to infection with infectious bovine rhinotracheitis virus

Intranasal exposure of goats to infectious bovine rhinotracheitis virus resulted in mild respiratory disease and virus reisolation from nasal secretions. No disease was produced in goats exposed to the same virus by the genital or ocular routes. There was serological evidence of contact transmission of infection from infected goats to cattle. Virus recrudescence was not detected in goats treated with dexamethasone two months after virus inoculation.     

In utero infection of swine fetuses with infectious bovine rhinotracheitis virus (bovine herpesvirus-1)

The pathogenesis of infectious bovine rhinotracheitis (IBR) virus (bovine herpesvirus-1) was studied in porcine fetuses after in utero inoculation. Laparotomies were performed on 8 seronegative pregnant sows at 34 to 86 days of gestation, and all fetuses in 1 uterine horn of each sow were exposed to IBR virus via inoculation into the amniotic sacs. Fetuses in the other horn served as controls. Clinical signs of infection were not observed in the sows, except for 2 sows that aborted at postinoculation days (PID) 11 and 15. Fetuses of the remaining 6 sows were collected at slaughter on PID 15 to 28. Fetuses were examined for gross abnormalities, presence of IBR virus in tissues, and the formation of neutralizing antibodies to IBR virus. Of 33 inoculated fetuses from 6 sows, 10 were mummified, 11 were hemorrhagic and/or edematous, and 12 were alive. Necrotic lesions were observed on the skin and in the liver of dead and live fetuses. Virus was recovered from 29 of 33 inoculated fetuses. Infectious bovine rhinotracheitis virus was isolated from fetal skin, liver, lungs, kidney, spleen, stomach contents, brain, amniotic fluid, and placenta. Virus was isolated from 4 of 11 fetuses recovered from 1 aborting sow. Antibodies to IBR virus were not detected in sera from the sows. However, antibodies were detected in 6 of 15 fetuses inoculated at 63 to 86 days of gestation and collected at slaughter at 86 to 112 days of gestation. The youngest fetus with detectable IBR antibody was estimated to be 74 days of gestation by measuring crown-rump length of the fetus.     

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)     

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.     

A Histological Study of the Effects of the Herpesvirus of Infectious Bovine Rhinotracheitis in the Lactating Bovine Mammary Gland

Mastitis was produced in three first calf heifers by inoculation of the udder with the virus of infectious bovine rhinotracheitis. These animals were killed at different times during the course of the disease and tissues were harvested and examined histologically. The basic lesion resulted from the necrotizing effect of the virus upon the epithelial cells of the alveoli and ducts. Eosinophilic intranuclear inclusion bodies were demonstrated in tissues from animals killed at three and six days postinoculation, but not at nine days. Of interest was the presence of a large Reed-Sternberglike cell in tissues of the last two animals killed.     

Antibody responses and virus reisolation in turkeys experimentally infected with an infectious bursal disease isolate

Following the infection of turkey poults with a field isolate of infectious bursal disease virus, antibody levels were examined and reisolation of the virus was attempted. After inoculation at 36 days of age, peak titres in both the inoculated and a contact-exposed group were obtained after 13 days. The titres fell slightly during the next week and then remained level until the experiment was terminated at 91 days of age. Virus was reisolated from faeces from day 3 until day 8 after inoculation in the inoculated group and from day 4 until day 9 in the contact-exposed group. In the inoculated group, virus was recovered from the bursae, spleens and intestines on both days 4 and 6 after inoculation, but the thymuses on day 6 only. No clinical signs were observed.     

Experimental inoculation of cattle with bovine herpesvirus-4: evidence for a lymphoid-associated persistent infection

A strain of bovine herpesvirus-4 isolated from cows with mammary pustular dermatitis was used for experimental inoculation of cattle. This strain is serologically indistinguishable from the group prototype Movar 33/63 and from strain DN-599. Seronegative cattle were inoculated IV or by simultaneous intranasal, IV, intramammary (via teat channel), and intradermal inoculations. All inoculated cattle seroconverted. Clinical signs of disease or lesions were not evident, except for a dermal lesion corresponding with one intradermal inoculation site. Virus was recovered from the dermal lesion and was excreted in the milk for 17 days. Virus was recovered from esophagopharyngeal fluid at 9 and 13 days after inoculation. At different times of euthanasia (2 to 14 months after inoculation), virus was recovered from cocultures with bovine lung cells and/or explant cultures of lymph nodes, spleen, tonsils, and, in one case, kidney. In 2 animals, the virus was recovered repeatedly during 1 year from peripheral blood leukocytes by cocultivation with bovine lung cells. The number of infectious leukocytes, as determined by infectious center assay, ranged from less than 1 to 6 infectious cells/10(7) leukocytes.