EXPERIMENTAL ADENOVIRUS PNEUMONIA IN CALVES

A mild interstitial pneumonia with mononuclear cell infiltration was produced in calves following intra-tracheal inoculation of the BIL adenovirus. Viral antigen appeared early in regional lymph node. An interstitial reaction developed early in the lungs, and pneumonic lesions and infective virus were present by the third day after inoculation. Virus spread rapidly trachea, tonsils and nasal mucosa, and was creted from the third to eighth day. Upper and lower respiratory tissues continually harboured virus until the 12th day, when the experiment was terminated. The virus was isolated from the livers of two calves. All tissues yielded low concentrations of virus, and only the lung showed pathological reactions. The reactions were qualitatively similar to known adenovirus pneumonias, but considerably milder, and lacked the characteristic necrotic and proliferative bronchiolar changes.     

OBSERVATIONS OF SW AINSONA GALEGIFOLIA POISONING IN CATTLE IN NORTHERN NEW SOUTH WALES

A mild interstitial pneumonia with mononuclear cell infiltration was produced in calves following intra-tracheal inoculation of the BIL adenovirus. Viral antigen appeared early in the regional lymph node. An interstitial reaction developed early in the lungs, and pneumonic lesions and infective virus were present by the third day after inoculation. Virus spread rapidly to trachea, tonsils and nasal mucosa, and was excreted from the third to eighth day. Upper and lower respiratory tissues continually harboured virus until the 12th day, when the experiment was terminated. The virus was isolated from the livers of two calves. All tissues yielded low concentrations of virus, and only the lung showed pathological reactions. The reactions were qualitatively similar to known adenovirus pneumonias, but considerably milder, and lacked the characteristic necrotic and proliferative bronchiolar changes.     

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 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.     

SYBR Green Ⅰ实时PCR对猪细小病毒体外复制动态分析

根据已经发表的猪细小病毒（PPV）的VP2基因序列,设计2对特异性引物,建立了检测PPV的SYBR GreenⅠ实时PCR方法。该方法最小检出量为12个PPV拷贝。模板稀释度在108范围内呈良好的线性关系,与猪圆环病毒2型、猪繁殖与呼吸综合征病毒、乙型脑炎病毒、猪瘟病毒、伪狂犬病病毒无交叉反应。应用本方法对PPV在体外感染细胞后的复制动态进行了观察,并绘制了病毒的体外增殖曲线。数据换算为每瓶中细胞内、外病毒拷贝数,结果显示细胞外病毒含量在接毒初始的36h逐渐下降,随后开始逐步增加;接毒后84h培养液中的病毒含量（1.739×1010拷贝）逐渐超过细胞内的病毒含量（1.321×1010拷贝）;在接毒后108h培养液中病毒含量达到峰值（7.626×1010拷贝）,随即病毒含量开始快速下降。细胞内病毒粒子在接毒后24h内为对数增长期,然后为缓慢增长期,至接种后72h达到复制峰值（1.425×1010拷贝）,并维持至108h。与病毒复制动态变化相对应的细胞病变是从细胞聚集、开始形成空斑到约80%的细胞病变产生,108h之后随着细胞的大量死亡,细胞内、外病毒数量都开始急剧减少。     

Cell Culture Studies of a Neonatal Calf Diarrhea Virus

The effects of a neonatal calf diarrhea virus on cell cultures were investigated. Bovine embryonic kidney cell cultures were the most satisfactory for production of virus. Cytoplasmic changes detected after inoculation with a high multiplicity of virus were: 1) cytoplasmic vacuoles; 2) some eosinophilic cytoplasmic inclusions; and 3) some degeneration of cells and detachment from the monolayer. Cultures stained with fluorescein-labeled antibody showed cytoplasmic fluorescence as early as four hr after infection with the maximum fluorescence at five days. No cross reactions were observed between the neonatal calf diarrhea virus and reovirus type 1 or type 3 by the fluorescent antibody technique. Plaques were small and were not produced consistently. The optimal adsorption time was one to two hr. The maximum titer was reached at 18 hr, with the cell-associated titer remaining higher than the cell-free titer until that time. An interferon was produced by cultures infected with either ultraviolet-inactivated or untreated virus.     

Pathogenesis of canine parvovirus enteritis: sequential virus distribution and passive immunization studies

After oral inoculation, the sequential distribution of canine parvovirus was studied in 14 nine-week-old seronegative beagle dogs. Two or three dogs were necropsied on days 1 through 6 after inoculation. Tissues were collected for virus isolation, immunofluorescence testing, and light microscopy. Virus was isolated from, and fluorescent cells were seen in the tonsil, retropharyngeal and mesenteric lymph nodes one and two days after inoculation. Virus infection of systemic and intestinal lymphoid tissues occurred as early as three days after inoculation and was associated with viremia. Intestinal epithelial infection was first seen four days after oral inoculation. All dogs were viremic before intestinal epithelial infection was found. Fecal virus excretion first occurred four days after oral virus inoculation. Intestinal virus infection and lesions became progressively more severe between four and six days after inoculation. The severity of intestinal lesions was variable and related to the severity of systemic lymphoid tissue lesions and the magnitude and duration of viremia. Four littermates of virus-infected dogs were passively immunized against canine parvovirus with convalescent canine serum 24 hours after oral virus inoculation. Neither clinical signs, lymphopenia, nor fecal virus excretion occurred in passively immunized dogs. Intestinal epithelial infection was not demonstrable by immunofluorescence testing when passively immunized dogs were necropsied four, five, and six days after virus inoculation.     

Detection of pseudorabies virus antibodies: time of appearance by two serotests

This report describes a time-course comparison of detection of pseudorabies virus antibodies in experimentally infected swine by the virus-neutralization (VN) and indirect hemagglutination tests. Specific antibody titers were observed by the IHA test at 5 days after swine were inoculated, but not until 12 days by the VN test. The predominant immunoglobulin (Ig) class present in the serums of the swine at 5 and 7 days after inoculation was IgM, as determined by sulfhydryl reductions. The VN test lacked sensitivity to early Ig levels (IgM) in these experimentally infected swine, while the indirect hemagglutination test was highly sensitive to these same levels. On the basis of these results, it is possible that the VN test may read early infections as pseudorabies virus negative, due to the low presence of IgG in these samples.     

Serological reactions in sheep and cattle experimentally infected with three Australian isolates of bluetongue virus

Serums from 103 sheep and 24 cattle experimentally infected with one of 3 serotypes of bluetongue virus isolated in Australia were tested for antibody to bluetongue virus in the serum neutralisation test and the agar gel diffusion precipitin test. Antibody to bluetongue virus was first detected by these tests 8 to 10 days after intravenous infection in 4 sheep that were bled daily for serum analysis. The agar gel diffusion test failed to detect antibody in 28% (29/103) of sheep which had seroconverted in the serum neutralisation test. A further 7% (7/103) of sheep serums were negative in both tests 14 to 22 d after infection. Both tests detected antibody to bluetongue virus in all cattle serums by 10 days after detection of viraemia. In comparison with the intravenous route of infection, extended prepatent periods for the commencement of viraemia resulting from intradermal, subcutaneous and intrauterine routes of infection in the cattle caused corresponding delays in the detection of antibody. For example, one cow that was infected by intrauterine inoculation did not become viraemic until 22 d after inoculation and antibody was not detected until 32 d after inoculation.     

Shedding of feline immunodeficiency virus in semen of domestic cats during acute infection

OBJECTIVE: To examine shedding of cell-free and cell-associated feline immunodeficiency virus (FIV) in semen of domestic cats during acute infection. ANIMALS: 7 specific-pathogen-free sexually intact male cats. PROCEDURE: 6 cats were inoculated IV with 5 x 10(6) 50% tissue culture infective doses of FIV-NCSU1, and 1 cat served as an uninfected (control) cat. Infection was confirmed in the 6 cats. Periodically for up to 16 weeks after inoculation, cats were anesthetized and ejaculates obtained by use of electroejaculation. Virus was isolated from filtered seminal plasma and washed seminal cells by co-cultivation with a feline CD4+ T-cell line. Seminal cell lysates were also examined for a 582-base pair segment of FIV gag provirus DNA, using a nested polymerase chain reaction amplification. RESULTS: During the acute phase of FIV infection, virus was evident in semen of 5 inoculated cats. Five cats had virus-positive seminal plasma and 3 had virus-positive cellular constituents during the study. Virus was isolated from 8/22 (36%) seminal plasma samples and 2/17 (18%) seminal cell specimens. Provirus DNA was detected in 5/24 (21%) seminal cell lysates. Cell-free virus was isolated as early as 6 weeks after inoculation, whereas cell-associated virus was isolated as early as 12 weeks after inoculation. Provirus DNA was detected in seminal cells from one cat as early as 1 week after inoculation. CONCLUSIONS AND CLINICAL RELEVANCE: Cell-free and cell-associated FIV are shed in semen of cats early during the course of infection. Samples obtained before seroconversion may contain virus. Virus shedding in ejaculates varies between and within cats during acute infection.     

Experimental rabies in skunks: persistence of virus in denervated muscle at the inoculation site.

Striped skunks (Mephitis mephitis) were inoculated into the denervated abductor digiti quinti muscle with street rabies virus. They were killed at various times after inoculation and several tissues were examined by immunofluorescence and light microscopy. Muscle at the inoculation site was examined electron microscopically. Rabies antigen was detected in muscle fibers first on day 7 and persisted until day 28. Light and electron microscopic lesions at the inoculation site included atrophic and degenerating muscle fibers and a few focal and regional endomysial accumulations of macrophages, lymphocytes and plasma cells. Scattered myocytes contained bodies of matrix, virions and anomalous tubular structures on electron microscopic examination. The results indicate that replication of rabies virus may occur in infected muscle fibers at the inoculation site until 28 days after exposure. This could contribute to variations in the incubation period for the first two to three months after exposure. However, the results do not support the contention that virus is contained in striated muscle cells throughout the long incubation periods.     

Sites of release of airborne foot-and-mouth disease virus from infected pigs

Pigs infected with foot-and-mouth disease virus by different routes of exposure were air-sampled individually, first as 'intact' (I-) pigs and then as 'intubated' (T-) pigs, using an endotracheal tube. Irrespective of the route of infection it was found that during the early stages of disease more virus was recovered from I-pigs than from T-pigs. Most of the virus from I-pigs during incubation and early disease was associated with large and medium sized particles. T-pigs infected by direct or indirect contact excreted a range of particle sizes at this time but T-pigs infected by inoculation only excreted small particles. During advanced disease all sizes of particle were excreted by I- and T-pigs. Greater amount of airborne virus were recovered at this time from I-pigs than T-pigs infected by indirect contact but I-pigs infected by intravenous or intradermal inoculation excreted less infectivity than T-pigs. The results show that the respiratory tract is involved during the early stages of foot-and-mouth disease in pigs infected by either natural or experimental routes of exposure and suggest that upper respiratory infection precedes lower.     

Effect of intratesticular inoculation with Aujeszky's disease virus on genital organs of boars

Ten 8-10-month-old Belgian Landrace boars were intratesticularly inoculated with 500 TCID50 of a virulent Belgian Aujeszky's disease virus (ADV) isolate (75V19) in 0.1 ml volume. One control boar was similarly inoculated with phosphate-buffered saline solution. The genital organs of six inoculated boars were examined by virus isolation and immunofluorescence. In spite of high virus titers, the fluorescence in the testicles remained limited to a few small foci in the interstitial connective tissue and tunica albuginea at or close to the inoculation site. Neither virus replication, necrosis nor inflammatory lesions could be demonstrated in the epithelium of the seminiferous tubules. However, virus replication was regularly demonstrated in the serosa covering testicles, plexus pampiniformis, ductus deferens and tunica vaginalis. Virus was also isolated from the scrotal fluid. It is suggested that the serosa is the primary target tissue for ADV. The other four boars were inoculated to study the effect of ADV on semen. Severe morphologic alteration and lowered sperm cell concentrations were observed during several weeks after inoculation or until slaughter at 47, 53 and 58 days post inoculation. Virus was isolated from semen of only two out of four boars examined at 9 and 10 days post inoculation.     

Development and serial passage of persistent lymphocytosis associated with bovine leukemia virus infection in cattle

Two calves each were inoculated with 1.5 x 10(8) or 5 x 10(9) lymphocytes collected from each one cow which had persistent lymphocytosis (PL) and antibodies to bovine leukemia virus (BLV). A sudden increase in the number of peripheral blood lymphocytes (PBL) was observed 14 and 23 days, respectively, after inoculation and the maximum number reached 29,000 and 52,000/microliters 72 and 57 days after inoculation. Although the degree of PL decreased gradually in these cattle, it continued until 14 and 44 months after inoculation when one animal was sacrificed and the other died of lymphosarcoma. The PL was passaged in cattle by inoculation of a large number of PBL obtained from cattle at the stage of PL (PLL). The degree of PL was severer in cattle inoculated with a larger number of PLL. PL was not caused by inoculation of PBL obtained from either BLV-infected non-PL cattle or cattle free of BLV. The PL was also caused by inoculation of PLL into BLV-infected non-PL cattle. On the other hand, it was not observed after inoculation of a large amount of cell-free virus obtained from short-term cultures of PLL. Antibodies to BLV developed earlier and to higher levels in cattle inoculated with PLL than in those inoculated with cell-free virus. These facts show that infection with BLV was established more effectively by PLL than by cell-free virus, the infection may occur by lymphocyte to lymphocyte interaction and the actual number of infected BLV may have an important role in development of PL.     

Response of cattle persistently infected with bovine virus diarrhoea virus to bovine leukosis virus

Six cattle persistently infected with bovine virus diarrhoea virus (BVDV) and seronegative, and two control, virus negative seropositive cattle were inoculated with lymphocytes infected with bovine leukosis virus (BLV). The two controls produced a normal immune response to BLV, developing antibodies at four and five weeks after inoculation. Two of the six cattle persistently infected with BVDV developed a strong antibody response by six weeks after inoculation with BLV. Four developed a depressed response to BLV, characterised in three by a 'hooking' reaction in the immunodiffusion test which persisted in successive bleedings but was interspersed occasionally by a weak positive reaction. In one of these animals, a series of 'hooking' reactions was followed by a number of negative results. The fourth animal remained serologically negative until 16 weeks after inoculation when a 'hooking' reaction was observed followed by a series of negative results. BLV was isolated from all the cattle persistently infected with BVDV at 42 or 58 weeks after inoculation regardless of whether the serum samples gave negative, 'hooking', weak positive or positive reactions in the immunodiffusion test. BLV was consistently isolated from the nasal secretions of a steer which was BVDV negative but seropositive. The possibility of decreased immune responsiveness to BLV in animals persistently infected with BVDV should be considered when formulating regulations governing the testing of animals for freedom from BLV.     

Duration of protection of calves against rhinovirus challenge exposure by infectious bovine rhinotracheitis virus-induced interferon in nasal secretions

Six calves inoculated intranasally with a vaccinal strain of infectious bovine rhinotracheitis (IBR) virus and 6 control calves were given a placebo. All calves were subsequently challenge exposed (by aerosol) with rhinovirus--3 of the calves from each group at 2 days after they were inoculated with IBR virus or with placebo and the remaining calves at 6 days. Nasal excretion of viruses, interferon (IFN) concentrations in nasal secretions (NS), and neutralizing antibody in sera and NS were determined. All calves given the vaccinal IBR virus subsequently had IFN in their NS. Interferon was detected as early as 1 day, reached maximal titers at 2 to 4 days, and persisted in individual calves for 5 to 10 days after inoculation. Rhinovirus shedding was not detected from IBR virus-inoculated calves whose NS contained both rhinovirus antibody and IFN at the time of challenge exposure; such calves were protected at either 2 or 6 days after IBR virus inoculation. The outcome of rhinovirus challenge exposure of calves whose NS contained IFN, but not rhinovirus antibody, varied with the day of challenge exposure. Rhinovirus excretion was detected from 2 of these calves challenge exposed 2 days after IBR virus inoculation, but was not detected from a calf challenge exposed 6 days after inoculation. However, while IFN was present in NS from the former 2 calves, rhinovirus shedding was markedly reduced as compared with that from control calves without IFN or NS antibody at the time of challenge exposure. Consistent relationship was not observed between the rhinovirus neutralizing antibody titer of calves' sera and NS. The antibody titer of NS more closely correlated with protective immunity to rhinovirus infection than did the serum antibody titer.     

Hog Cholera: V. Demonstration of the Antigen in Swine Tissues by the Fluorescent Antibody Technique

The fluorescent antibody technique was employed to detect hog cholera virus in tissue sections of various organs from experimentally infected swine. The method proved to be highly sensitive and infection could be detected in these animals as early as three days after inoculation with the virus. Best results were obtained when tissues were collected from young animals in advanced disease rather than from sows or from pigs in the early febrile phase. Tonsil, spleen and lymph node were the tissues of choice and were most satisfactory when removed from freshly killed animals rather than from those that had died.     

免疫鸡群感染新城疫强毒后的排毒规律

将经过２次新城疫（ＮＤ）基础免疫的ＳＰＦ鸡,随机分成５组,每组８只,在６０日龄时分别用Ｆ４８Ｅ８、Ｔｅｘａｓ、Ｈｅｒｔ３３ＮＤ强毒和Ｌａｓｏｔａ弱毒经口腔接种０．２５ｍＬ／只,１２ｈ后采取泄殖腔棉拭,利用ＮＤ强毒快速诊断试剂盒进行排毒的动态监测,并在攻毒前期、中期、后期测定各试验组ＳＰＦ鸡的ＨＩ效价。试验第３天开始排毒,２０ｄ结束,其间在６～７ｄ和１１～１３ｄ出现２次排毒高峰。ＨＩ抗体在初期先是降低１个滴度,后期开始升高而且离散度不断增大。