Effect of temperature, relative humidity and medium on the aerosol stability of infectious bovine rhinotracheitis virus.

Aerosols of infectious bovine rhinotracheitis virus were generated with a Devilbiss 40 nebulizer from Eagle's minimum essential medium, nasal secretion from a noninfected calf and nasal secretion from a calf artificially infected with infectious bovine rhinotracheitis virus and aged in a rotating drum at temperatures of 6 degrees C or 32 degrees C and relative humidities of 30% or 90%. The aerosols were sampled at seven minutes after start of spraying, one hour, two hours and three hours with an all glass impinger (AGI-30) and titrated for infectivity in cell cultures. Physical decay was determined by a rhodamine B tracer technique. During spraying (seven minutes from start of spraying), the virus was usually more stable in aerosols of nasal secretion from a noninfected calf and at 90% relative humidity. In nasal secretion from a noninfected calf the virus survived best at 90% relative humidity when the temperature was 6 degrees C and best at 30% relative humidity when the temperature was 32 degrees C. During aging, biological decay was greater at the higher temperature, and at 6 degrees C, the highest decay rates occurred at 30% relative humidity in Eagle's minimum essential medium and at 90% relative humidity in nasal secretion from a noninfected calf. The stability of infectious bovine rhinotracheitis virus infected nasal secretion was not widely different from that in noninfected nasal secretion, although under certain conditions greater survival occurred in the noninfected secretion.     

Methods for detection and frequency of contamination of fetal calf serum with bovine viral diarrhea virus and antibodies against bovine viral diarrhea virus.

Methods used by the National Animal Disease Center to test fetal calf serum for contamination with bovine viral diarrhea virus (BVDV) and antibodies against BVDV are described. Using those methods, virus was isolated from 332 of 1,608 (20.6%) lots of raw fetal calf serum obtained specifically for the Center and 93 of 190 (49%) lots of commercially available fetal calf serum. Virus neutralization and immunoperoxidase staining tests were used to detect antibodies against BVDV in 224 of the 1,608 (13.9%) lots of raw fetal calf serum. Both BVDV and antibodies against BVDV were detected in 50 lots of raw serum. The molecular specificity of antibodies against BVDV was determined by radioimmunoprecipitation. Lots of fetal calf serum that contained BVDV-specific antibodies that did not neutralize virus were identified.     

Sensitivity of seven different types of cell cultures to three serotypes of foot-and-mouth disease virus.

The ability of bovine tongue origin foot-and-mouth disease virus serotypes A, O and C to replicate in seven different types of cell cultures was studied. Primary and secondary calf thyroid cells were equivalent in susceptibility to bovine kidney cell cultures passaged up to five times. Calf thyroid cells lost their susceptibility after two passages. Cryopreserved bovine kidney cell cultures passaged three and four times were equivalent in susceptibility to sensitive calf thyroid and bovine kidney cells. Susceptibility to foot-and-mouth disease virus serotype C was most variable among the cells tested. Lamb testicle and porcine kidney cells were susceptible to foot-and-mouth disease virus while goat and calf testicle and calf lung cells were refractory.     

Infectivity of bovine adenovirus type 5 recovered from a polyarthritic calf with weak calf syndrome.

Bovine adenovirus type 5, isolated from newborn calves with a polyarthritic disease known as "weak calf syndrome" caused a mild, self-limiting illness in susceptible calves. The induced illness was characterized by marked pyrexia and occasionally by mild diarrhea. It was concluded that the virus may contribute to morbidity and mortality associated with the weak calf syndrome by adding to the stress and debilitation caused by cold wet weather and by bovine viral diarrhea (BVD) virus, which has also been isolated from tissues of calves affected with weak calf syndrome.     

Bovine respiratory syncytial virus infection in an ontario cattle herd

Bovine respiratory syncytial virus was recovered from the lung of a six month old calf that died during an outbreak of respiratory disease in a cattle herd in Ontario. Lung tissue removed from the calf at necropsy, performed within two hours of death, was frozen at -70°C prior to virus isolation attempts. Syncytia and intracytoplasmic inclusions were demonstrated both in histological sections of the calf's lung and in stained cell culture preparations infected with the bovine respiratory syncytial virus isolate. Direct fluorescent antibody and virus neutralization tests serologically confirmed the identity of the isolate.     

Associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus, antibodies against bovine viral diarrhea virus, or antibodies against infectious bovine rhinotracheitis virus in calves

OBJECTIVE: To measure associations between health and productivity in cow-calf beef herds and persistent infection with bovine viral diarrhea virus (BVDV), antibodies against BVDV, or antibodies against infectious bovine rhinotracheitis (IBR) virus in calves. ANIMALS: 1,782 calves from 61 beef herds. PROCEDURES: Calf serum samples were analyzed at weaning for antibodies against type 1 and type 2 BVDV and IBR virus. Skin biopsy specimens from 5,704 weaned calves were tested immunohistochemically to identify persistently infected (PI) calves. Herd production records and individual calf treatment and weaning weight records were collected. RESULTS: There was no association between the proportion of calves with antibodies against BVDV or IBR virus and herd prevalence of abortion, stillbirth, calf death, or nonpregnancy. Calf death risk was higher in herds in which a PI calf was detected, and PI calves were more likely to be treated and typically weighed substantially less than herdmates at weaning. Calves with high antibody titers suggesting exposure to BVDV typically weighed less than calves that had no evidence of exposure. CONCLUSIONS AND CLINICAL RELEVANCE: BVDV infection, as indicated by the presence of PI calves and serologic evidence of infection in weaned calves, appeared to have the most substantial effect on productivity because of higher calf death risk and treatment risk and lower calf weaning weight.     

EXPERIMENTAL ENCEPHALOMYOCARDITIS VIRUS INFECTION IN CALVES

Nine calves, were inoculated intravenously with the Innisfail strain of encephalomyocarditis (EMC) virus. Apart from a mild fever, no obvious clinical signs were noted. A low titre viraemia was demonstrated in all 5 calves from which blood was collected, and EMC virus was recovered from the myocardium of 3 of 6 calves at 2, 3 and 6 days after inoculation. Virus was not recovered from the central nervous system. No excretion of EMC virus in urine or faeces was detected in 3 calves. Histopathological lesions were present in brain tissue from only 1 calf, destroyed 14 days after inoculation, and in the heart muscle from another calf, destroyed 7 days after inoculation. Macroscopic lesions were not seen in these organs. Both neutralising and haemagglutination-inhibiting antibodies were produced within one week of infection, reached a peak in 3–4 weeks and persisted undiminished until 9 weeks after inoculation. By nitration on Sephadex G 200, it was shown that the early response was due to IgM type antibodies, and these were replaced by IgG antibody. One calf was inoculated intracerebrally with EMC virus. It developed a flaccid posterior paralysis and was destroyed 6 days later. Virus was recovered from the brain and spinal cord, but no significant histopathological lesions were detected in brain or spinal cord from this calf.     

A paravaccinia virus isolated from cattle.

Isolation of viruses from calves with acute respiratory tract disease were attempted on bovine embryonic lung cell cultures. An isolate obtained from one calf with oral lesions and respiratory disease, designated 44-M-E482, was characterized as a paravaccinia virus on the basis of biological and physical properties. The calf from which the paravaccinia virus 44-M-E482 was isolated did not possess serum neutralizing antibody in its convalescent sera; neither did experimentally inoculated calves possess serum neutralizing antibody to the isolate. However, a low titer of serum neutralizing antibody was produced in one calf after several intravenous injections of the virus. Inoculation of calves with 44-M-E482 into the oral mucosa, skin, nasal cavity and pharynx did not cause any noticeable illness or lesions. The relation of 44-M-E482 to the viruses which cause bovine papular stomatitis and pseudocowpox is discussed.     

An attempt to protect calves against experimental bovine leukosis using allografts

Six calves sensitised by implanting skin from a calf were later inoculated with lymphocytes from the same calf after the calf had been infected with bovine leukosis virus (BLV). Two out of 6 calves challenged did not develop BLV antibodies and BLV was not isolated from these animals, whereas all of the 5 control calves became infected with BLV.     

Reproductive performance of apparently healthy cattle persistently infected with bovine viral diarrhea virus.

A Holstein-Friesian bull and three Holstein-Friesian cows were seronegative for bovine viral diarrhea (BVD) virus but were persistently infected with the virus. Virus was isolated from buffy coat cells and nasal and lacrimal secretions during their lifetime, and they remained free of clinical signs of BVD. The three cows were pregnant when purchased, and they gave birth to full-term calves. One calf lived only a few hours, one calf became ill and died within a few days, and one calf became ill and was euthanatized within a few weeks. One cow was then bred and became pregnant but aborted a 7-month fetus. A second cow was bred approximately 5 months after parturition but did not conceive. The third cow was necropsied 6 weeks after calving, because of loss of weight. Although the bull's semen contained BVD virus when seropositive cows were bred, normal calves were born. When seronegative heifers were bred, they became seropositive to BVD virus within two weeks, with higher titers in six weeks. On heifer conceived after one service but aborted a 6-month fetus. Three others continued to have estrous cycles until their titers rose to 1:128, then they conceived and gave birth to normal calves. Another heifer conceived on the first service, had a titer of 1:128 two weeks after breeding, and gave birth to a normal calf.     

Establishment of an attenuated strain of bovine respiratory syncytial virus for live virus vaccine

To develop a live virus vaccine for the prevention of bovine respiratory syncytial (BRS) virus infection in calves, an attempt was made to produce an attenuated virus. The RS-52 strain of BRS virus, isolated from the nasal secretions of a naturally infected calf, was subjected to serial passages in adult hamster lung established (HAL) cells at 30 degrees C and the attenuated rs-52 strain as a live virus vaccine was established. The rs-52 strain multiplied better at 30 degrees C than at 34 or 37 degrees C in HAL cells. The differences in the highest virus titers of this strain between the culture temperature of 30 degrees C and that of 34 or 37 degrees C were more than 2.25 log TCID50. Colostrum-deprived newborn calves and 2 approximately 4 months old calves inoculated with the rs-52 strain manifested no abnormal clinical sings at all. However, all inoculated calves produced serum neutralization antibody. When the colostrum-deprived newborn calves immunized with the rs-52 strain were challenged with the virulent NMK7 strain of BRS virus, they exhibited no pyrexia or other abnormal clinical signs at all. An attempt was made to recover the virus from nasal secretions of these calves, but in vain. On the other hand, a nonimmunized control colostrum-deprived newborn calf developed slight fever, mild cough, and slight serous nasal discharge after challenge exposure. The virus was recovered from nasal secretions of this calf. From these results, it was considered that the rs-52 strain could be used as an attenuated live virus vaccine for prevention of BRS virus infection.     

Serologic responses of calves to sequential infections with epizootic hemorrhagic disease virus serotypes

Six calves were inoculated with 1 of 2 North American serotypes of epizootic hemorrhagic disease virus (EHDV) and then inoculated with the second serotype 16 weeks later. One calf did not develop an immune response to EHDV after primary inoculation and was removed from the study. Viremia after primary inoculation was transient. Although each infected calf developed a high serum neutralizing antibody titer to EHDV, at no time after inoculation with one or both viruses was antibody detected that neutralized any US serotypes of bluetongue virus. After exposure to both serotypes of EHDV, 4 of 5 calves developed antibodies that cross-reacted with group-specific bluetongue virus antigens.     

Bovine Viral Diarrhea Virus and Escherichia Coli in Neonatal Calf Enteritis

This study was initiated to determine the etiologic and pathogenic significance of an American strain of bovine viral diarrhea (BVD) virus (strain NADL-MD) in enteritis of neonatal calves (calf scours).

Three colostrum-fed calves from dams exposed intravenously to BVD virus at 6, 16 and 25 days prepartum, respectively, had moderate diarrhea persisting until the eighth day of life. The BVD virus was isolated from all 3 calves and persisted up to 93 days in 1 calf, indicating either that BVD was transmitted in utero or via the dam's milk.

Three specific pathogen free (SPF) calves permitted dams' colostrum for the first 4 feedings and then given milk replacer were exposed orally on the day of birth to BVD virus. One calf died of neonatal enteritis 28 hours post-exposure and at necropsy the BVD virus was isolated from several of its organs. The remaining 2 calves had a mild diarrhea persisting to the eighth day of age.

Two calves permitted dams' colostrum ad lib. for 72 hours, and then weaned, were exposed orally to BVD virus. Both calves had a mild persistent diarrhea and BVD virus was isolated from their blood for 56 days post-exposure.

Of 13 SPF, colostrum-deprived calves exposed orally or intranasally at birth to the BVD virus, 4 had severe diarrhea and died of neonatal enteritis from 38 hours to 13 days postexposure. Isolations of BVD virus were made from several of the organs of the calves at necropsy. All of the 9 surviving calves had a moderate to severe diarrhea frequently persisting for 7 to 10 days, and BVD virus was isolated from the survivors up to 103 days postexposure.

Several strains of Escherichia coli were isolated from calves after the second day of life, but were neither pathogenic for mice, nor serologically related to strains of E. coli usually associated with outbreaks of calf scours. Four colostrum-deprived SPF calves were exposed orally at birth to a strain of E. coli isolated from the intestine of the calf with the most acute symptoms and fatal neonatal enteritis. None of the four calves receiving the E. coli had diarrhea. One calf, however, had respiratory distress and died on day 5.

Two SPF colostrum-deprived control calves had neither diarrhea nor respiratory distress.

The above findings support the conclusion that BVD virus should not be overlooked as a primary cause of the neonatal calf enteritis complex.

     

A bovine virus diarrhea calfhood vaccination trial in a persistently infected herd: effects on titres, health and growth.

A controlled calfhood vaccination trial to prevent bovine virus diarrhea was conducted in a 100 head cow-calf operation with a three year history of annual calf losses due to enteric bovine virus diarrhea (persistently infected herd). Approximately 50% of the calves were vaccinated at six, 12 and 24 weeks of age. Paired serum samples and growth data were collected on three occasions for comparison between vaccinates and controls. Three vaccinated calves died of enteric bovine virus diarrhea in the first year of the trial and one nonvaccinated calf died in the second year. Two of the three vaccinated calves had developed bovine virus diarrhea virus neutralization antibody titres of 2048 or greater before developing clinical signs. The control and third vaccinated calf failed to seroconvert before dying of enteric bovine virus diarrhea. Approximately 90% of the vaccinated calves seroconverted compared to approximately 40% of the controls. Paired serum samples collected from 75% of the cows in the spring, summer and fall of each year of the trial, showed persistent high bovine virus diarrhea virus neutralization titres in all samples. Calf vaccination before 12 weeks of age had little effect on seroconversion due to high levels of passive antibody to bovine virus diarrhea. Growth data showed that there was no improvement in weight gain or rate of growth in the vaccinated calves.     

Diagnostic investigation of bovine viral diarrhea infection in a Minnesota dairy herd

Bovine viral diarrhea (BVD) virus infection was diagnosed in neonatal calves with enteritis. Successful diagnostic procedures included direct immunofluorescence of frozen tissue sections, histopathology, and virus isolation. Virus isolation from buffy coats and serum was successful in detecting infected animals, whereas direct immunofluorescence of buffy coat samples was found to be less reliable. Virus was not isolated from any fecal samples. Booster vaccinations and the culling of animals shedding virus resulted in improved calf viability in this herd. It is suggested that procedures for the diagnosis of BVD virus infection should always be included in the diagnosis of neonatal calf enteritis.     

Prevalence of neutralizing antibody to the calf rotavirus in New York cattle.

In March 1973, a modified live virus vaccine was released for sale in the United States for the protection of neonatal calves from infection with calf rotavirus. At that time no published evidence existed that this agent was present in New York or the New England states. Serum neutralizing antibodies for the calf rotavirus (reovirus-like agent of neonatal calf diarrhea) were detected in serum from 108 of 110 dairy cattle in New York State representing 78 different herds. To exclude the possibility that the demonstrated serologic response may have been stimulated by vaccine virus, 36 samples were included that had been collected prior to the date of vaccine release. Neutralizing antibodies were demonstrated in 108 of the 110 sera ranging from titers of 4 to greater than 1024, thereby offering indirect evidence of the ubiquitous nature of calf rotavirus in New York.     

Characteristics of neonatal calf diarrhea virus ribonucleic acid.

The nucleic acids of neonatal calf diarrhea virus were characterized by isopycnic centrifugation in Cs2SO4, electron microscopy, ultraviolet absorbance temperature profiles and polyacrylamide gel electrophoresis. These studies indicated that the neonatal calf diarrhea virus genome consists of 11 segments of double stranded RNA with a total molecular weight of 10.75 million daltons.     

Effect of lymphocytes and broncho-alveolar washing cells on the replication of bovine herpesvirus type 1 in tracheal organ cultures

The daily addition of lymphocytes collected from a calf between 7 and 11 days after experimental infection with bovine herpesvirus type 1 (BHV-1) to bovine fetal tracheal organ cultures after infection with BHV-1 did not inhibit virus replication. The daily addition of normal lymphocytes, together with a low concentration of serum antibody against BHV-1, had a slight viral inhibitory effect which was believed to be due to antibody-dependent cell-mediated cytotoxicity. The addition of broncho-alveolar washing (BAW) cells, collected before infection or 30 days after infection of a calf with BHV-1, together with lymphocyte culture supernatant, to tracheal organ cultures immediately after infection with BHV-1 produced some inhibition of virus replication. Virus replication was markedly inhibited when BAW cells collected from the calf 18 days after infection were used in a similar manner.     

Natural infection of cattle with an atypical 'HoBi'-like pestivirus--implications for BVD control and for the safety of biological products

During a study on Bovine Viral Diarrhoea (BVD) epidemiology in Thailand, a pestivirus was detected in serum from a calf. Comparative nucleotide sequence analysis showed that this virus was closely related to a recently described atypical pestivirus (D32/00_'HoBi') that was first isolated from a batch of foetal calf serum collected in Brazil. The results from virus neutralisation tests performed on sera collected from cattle in the herd of the infected calf, showed that these cattle had markedly higher antibody titres against the atypical pestivirus 'HoBi' than against Bovine Viral Diarrhoea Virus types 1 and 2, or Border Disease Virus. The results also supported, consequently, the results from the molecular analysis, and demonstrated that a 'HoBi'-like pestivirus had been introduced to, and was now circulating in the herd. This study is the first to report a natural infection in cattle with a virus related to this atypical pestivirus, and it suggests that this group of pestiviruses may already be spread in cattle populations. The findings have implications for BVD control and for the biosafety of vaccines and other biological products produced with foetal calf serum. Consequently, these atypical pestiviruses should be included in serological assays, and any diagnostic assay aimed at detection of pestiviruses in biological products or animals should be tested for its ability to detect them.     

牛病毒性腹泻/粘膜病病毒在不同细胞上生长增殖的比较

牛病毒性腹泻／粘膜病病毒（ＢＶＤ／ＭＤ）Ｏｒｅｇｏｎ　Ｃ２４Ｖ弱毒株抗原的制备一直以在犊牛仔细胞上生长为主，为了使该病毒有更广泛的宿主细胞，对该病毒株在犊牛仔细胞上和睾丸细胞上生长增殖情况作了对比，结果证明，该病毒在两种细胞上的增殖情况无差异。