Experimental production of bovine respiratory tract disease with bovine viral diarrhea virus

Five 6-month-old calves were inoculated with bovine viral diarrhea (BVD) virus (n = 3) or Pasteurella haemolytica (n = 2) endobronchially with a fiberoptic bronchoscope. Five additional calves were inoculated sequentially with BVD virus followed by P haemolytica at a 5-day interval. Blood samples were collected daily from the calves for bacterial isolation. Clinical signs of respiratory tract disease in calves were recorded daily. If the calves survived, they were killed for necropsy 3 or 4 days after inoculation with P haemolytica (or 8 days after inoculation with BVD virus). The extent and nature of pulmonary lesions in the calves were determined, and the lower portion of the respiratory tract (lungs and trachea) was examined for both these organisms. The 3 calves, inoculated with BVD virus only, developed mild clinical signs mainly manifested as fever, nasal discharge, and occasional cough. Approximately 2% to 7% of the total lung capacity of these calves was pneumonic. Mild clinical signs and localized lesions involving about 15% of the lung volume developed in the 2 calves exposed to P haemolytica only. However, severe fibrinopurulent bronchopneumonia and pleuritis involving 40% to 75% of lung volume developed in the 5 calves inoculated sequentially with BVD virus and P haemolytica. The possible role BVD virus may have in bovine respiratory tract disease is discussed.     

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.     

牦牛病毒性腹泻/粘膜病的防制研究

20世纪80年代以来，我国牦牛群中陆续发现牛病毒性腹泻／粘膜病(BVD／MD)，血清阳性率在30％～42．4％之间，病死率在30％左右，本研究先后从四川、西藏等地牦牛中分离出病毒，并对其进行各种生物学特征鉴定后，表明该病毒与标准毒属同一种，所不同的是四川牦牛病毒株属非致细胞病变型，即属NCP型。但回归本动物能复制出典型病例。目前尚无国产牛粘膜病疫苗用于生产。本研究依据猪瘟病毒与牛病毒性腹泻／粘膜病病毒具有交叉免疫性的原理，用猪瘟弱毒苗对牦牛病毒性腹泻／粘膜病进行预防，试验证明用猪瘟弱毒苗可以预防牛病毒性腹泻／粘膜病，且安全可靠，具有实用价值。     

Cellular inflammatory response in the lungs of calves exposed to bovine viral diarrhea virus, Mycoplasma bovis, and Pasteurella haemolytica

Three, 5, or 7 days after inoculation with bovine viral diarrhea (BVD) virus (n = 12) or Mycoplasma bovis (n = 12), groups of calves were exposed to aerosols of Pasteurella haemolytica and were euthanatized 4 hours later. Histologic lesions in the lungs and the ratios of neutrophils to alveolar macrophages, collected by bronchoalveolar lavage, were compared with those of clinically healthy calves (n = 8) and calves inoculated with BVD virus only (n = 4), M bovis only (n = 4), or P haemolytica only (n = 2). Inoculation with BVD virus or M bovis did not have a significant (P greater than 0.05) effect on the neutrophil/macrophage ratio in the bronchoalveolar lavage. Aerosol exposure to P haemolytica induced a marked and significant (P less than 0.01) change in the neutrophil/macrophage ratio (from less than 1:9 to greater than 9:1). The reversed neutrophil/macrophage ratio in calves exposed to P haemolytica correlated well with the histologic changes in which small bronchi and bronchioles were plugged with purulent exudate. Inoculation with BVD virus did not induce gross or microscopic lesions in the lungs. Inoculation with M bovis resulted in a severe peribronchial lymphoid hyperplasia with mild exudation of neutrophils and macrophages into the cranioventral parts of the lungs.     

Studies with an unclassified virus isolated from diarrheic calves

A transmissible agent (Breda agent) was isolated from a calf with diarrhea and shown to be infectious by inoculation orally into gnotobiotic and conventionally reared calves. The “Breda” agent had the morphology of a virus and possessed a hemagglutinin. Antigenic studies showed the virus to be antigenically different from bovine coronavirus, parainfluenza 3 virus, bovine rotavirus, bovine parvovirus and bovine pestivirus (BVD). Attempts to culture the virus in cell or organ cultures or in embryonated eggs, were unsuccessful. The virus was either spherical or kidney shaped, with 7–9 nm peplomers on the surface. A few particles possessed coronavirus processes of 17–20 nm, but these were arranged irregularly and were thought to be tissue debris. Three out of eight experimental calves developed severe diarrhea and the lesions in the small and large intestines were similar to those reported for coronavirus. The virus replicated in the jejunal and ileal regions of the small intestine and in the spiral colon, as judged by immunofluorescence. The virus multiplied in all experimental calves and was excreted in the feces; excretion correlating with the onset of diarrhea or a change in the appearance of the feces. There was little or no malabsorption measured by the uptake of D-xylose and the fact that infection of both the crypt and villus epithelial cells was observed, suggests that the pathogenesis may be different from rotavirus and coronavirus. Fourteen of fortyseven calves in the outbreak were infected with the virus, virus was not identified in other farm outbreaks of the disease.     

Reproduction of mucosal disease with cytopathogenic bovine viral diarrhoea virus selected in vitro

Isolates of non-cytopathogenic bovine viral diarrhoea (BVD) virus from 18 persistently infected calves from one herd were compared by using monoclonal antibodies directed against the major viral glycoprotein gp53. All the isolates displayed an almost identical reaction pattern. Based on this antigenic analysis three cytopathogenic BVD and three non-cytopathogenic BVD viruses closely related to the non-cytopathogenic BVD herd isolate were selected. Six of the persistently infected calves were inoculated with a pool of the three closely related cytopathogenic BVD viruses and two with a pool of the three non-cytopathogenic BVD viruses. In addition three animals were infected with one closely related cytopathogenic BVD strain (Indiana) and two animals with the antigenetically different cytopathogenic BVD viral strain A1138/69. Regardless of the inoculation route all the animals superinfected with closely related cytopathogenic BVD viruses developed the characteristic lesions of mucosal disease within 14 days of infection. Animals which were inoculated with non-cytopathogenic BVD viruses which closely resembled the herd isolate, or with cytopathogenic BVD viruses which did not resemble the herd isolate did not develop any signs of disease. However, the latter group produced antibodies to the superinfecting virus.     

Comparison of the pneumopathogenicity of two strains of bovine viral diarrhea virus

The pneumopathogenicity in calves of 2 strains of bovine viral diarrhea (BVD) virus, isolate 2724 (a noncytopathogenic virus) and isolate 72 (a cytopathogenic virus), was compared. All calves were inoculated endobronchially, using fiberoptic bronchoscopy. Two calves were given Pasteurella haemolytica, 2 calves were given the noncytopathogenic BVD virus, and 2 calves were given cytopathogenic BVD virus. Five calves were inoculated sequentially with BVD virus and, 5 days later, with P haemolytica. Two of these calves were inoculated with the noncytopathogenic BVD virus and the other 3 with the cytopathogenic strain. Both BVD virus strains caused marked respiratory tract disease in the calves sequentially inoculated with P haemolytica and also impaired pulmonary clearance of P haemolytica. However, the effect of the cytopathogenic strain was more severe than the noncytopathogenic strain, indicating that strains of BVD virus may vary in their pneumopathogenicity for calves.     

Differentiation of hog cholera and bovine virus diarrhoea viruses in pigs using monoclonal antibodies

Monoclonal antibodies against hog cholera and bovine viral diarrhoea viruses were assayed on organ tissue sections of experimentally infected animals. The animals had been infected simultaneously with both viruses. The antibodies were tested using an indirect immunofluorescence test and an indirect enzyme immunoassay with a biotin/streptavidin/peroxidase detection system. A polyclonal hyperimmune serum was used as a control in direct immunofluorescence tests. Both techniques based on monoclonal antibodies were more sensitive and more specific than the conventional test, the enzyme immunoassay being more sensitive than the immunofluorescence test. Small amounts of BVD viral antigen were demonstrable with monoclonal antibodies in most organ tissues.     

Changes in Distribution and Numbers of CD4+ and CD8+ T‐lymphocytes in Lymphoid Tissues and Intestinal Mucosa in the Early Phase of Experimentally Induced Early Onset Mucosal Disease in Cattle

Mucosal disease (MD), one sequelae of bovine virus diarrhoea virus (BVDV) infection, causes severe lesions in lymphoid tissues and mucosal surfaces. Lesions are associated with the presence of cytopathogenic (cp) BVDV and initially characterized by apoptotic cell death. The objective of this investigation was to determine if this cell death is mediated only by the cp BVDV, which is known to induce apoptosis in cell culture or if immune‐mediated host reactions might also contribute. Early onset MD was experimentally induced in calves by inoculation of persistently viremic calves with a closely related cp BVDV. Calves were euthanized in the early phase of infection between days 5 and 13 post‐inoculation and tissues from tonsils, lymph nodes, Peyer's patches, jejunum and colon were collected. Presence of cp BVDV antigen was correlated with distribution of lymphocyte subpopulations in consecutive cryostat sections. In the lymphoid tissues, cp BVDV antigen was predominantly found in the lymphoid follicles. The increase of infected cells with time post‐inoculation was paralleled by a decrease of B‐lymphocytes and an increase of CD4+ T‐lymphocytes. An increased number of CD8+ T‐lymphocytes was seen in progressed lesions only. In the intestinal mucosa, initially multifocal, later diffuse infection with cp BVDV was accompanied by a multifocal or diffuse increase of CD4+ T‐lymphocytes, respectively. Numbers of IgA+ plasma cells and CD8+ T‐lymphocytes were decreased. The common change observed in lymphoid tissues and mucosa was the increase of CD4+ T‐lymphocytes in sites with lesions. This might indicate a cell‐mediated immune response to the cp BVDV. Besides their helper function to other cells of the immune system, activated CD4+ T‐lymphocytes might also exert cytotoxic activity, induce apoptosis in target cells via Fas/Fas ligand binding and thus contribute to the severity of tissue lesions in MD.     

Spread of Bovine Virus Diarrhoea virus in a herd of heifer calves

Summary

A calf persistently infected and immunotolerant to Bovine Virus Diarrhoea virus (BVD virus) was, on purpose, introduced to a herd of heifer calves over 4 months of age that had been reared as recipients for embryo transplantation.

All calves were brought in contact with the persistently infected animal. In total, 240 calves were involved in this experiment, 22 of which were serologically negative when introduced. These serologically negative animals developed antibodies against BVD virus within 5 months after introduction. At short distances from the persistently infected BVD virus shedder, negative calves seroconverted within 2 months, but at greater distances the moment of seroconversion was unpredictable.

The calves that had undergone a natural infection with BVD virus received embryos after transportation to an allied farm. In total, 14 calves were born after embryo transplantation, all of which were free of BVD virus, in spite of the presence of BVD‐virus on the latter farm.     

Intrauterine infection with bovine virus diarrhoea virus on alpine communal pastures in Switzerland

This study involved 13 calves, one to 50 days of age, born to first calf heifers that had been pastured on one of seven alpine communal pastures in the canton of St. Gallen during the summer of 1995. Of a total of 993 cattle pastured, 61 were pregnant heifers that were negative for bovine virus diarrhoea (BVD) antigen and for BVD antibodies at the start of pasturing. Seroconversion occurred in 26 of these pregnant heifers during the pasture period. Blood samples and skin biopsy specimens of calves born to 13 of these were examined for BVD antigen by antigen-ELISA and by an immunohistochemical technique, respectively. Blood samples were positive for BVD antigen in four calves, questionable in one calf, negative in seven and missing in one prematurely born calf. The four calves that were positive for BVD antigen in the blood were also positive in skin biopsies. Of the seven calves with a negative or missing blood test, six had positive and two had negative skin samples. Based on the combined results of blood and skin testing, 11 of 13 calves were positive for BVD antigen. Of the 11 infected calves, six were normal at birth, four were smaller than normal and one was premature and weak and was euthanized on humane grounds. Of the four small calves, two developed diarrhoea and died within the first month of life. The two calves that were negative for BVD antigen were clinically normal. The results of this study not only demonstrate the occurrence of in-utero infection with BVD virus, but also stress the importance of alpine communal pasturing in the spread of BVD virus. Because the prevention of infection with BVD virus on communal pastures does not seem feasible, it is recommended that all calves born to cows from such pastures be tested for BVD antigen.     

The pathology of concurrent bovine viral diarrhoea and infectious bovine rhinotracheitis virus infection in newborn calves

Concurrent bovine viral diarrhoea (BVD) and systemic infectious bovine rhinotracheitis (IBR) are reported from two neonatal (11 and 15 days old) calves. The diseases occurred sporadically in a large-scale herd which may have been due to the calves' heterogeneous immunobiological status. Gross pathological and histopathological examinations revealed focal interstitial pneumonia with acidophilic intranuclear inclusions in the alveolar epithelial cells and necrotic foci in the liver with a few intranuclear inclusions in the hepatocytes. There were subserous haemorrhages in the forestomachs and intestine, necrotic changes in the rumen, enteritis, lymphocytic necrosis in the Peyer's patches, and fibrinoid necrosis in the wall of some of the neighbouring blood vessels. BVD virus was demonstrated by immunofluorescence (IF), whereas IBR virus by electron microscopy, immunofluorescence and virus isolation.     

Spread of bovine virus diarrhoea virus in a herd of heifer calves.

A calf persistently infected and immunotolerant to Bovine Virus Diarrhoea virus (BVD virus) was, on purpose, introduced to a herd of heifer calves over 4 months of age that had been reared as recipients for embryo transplantation. All calves were brought in contact with the persistently infected animal. In total, 240 calves were involved in this experiment, 22 of which were serologically negative when introduced. These serologically negative animals developed antibodies against BVD virus within 5 months after introduction. At short distances from the persistently infected BVD virus shedder, negative calves seroconverted within 2 months, but at greater distances the moment of seroconversion was unpredictable. The calves that had undergone a natural infection with BVD virus received embryos after transportation to an allied farm. In total, 14 calves were born after embryo transplantation, all of which were free of BVD virus, in spite of the presence of BVD-virus on the latter farm.     

A study of some infectious causes of reproductive disorders in cattle owned by resource-poor farmers in Gauteng Province, South Africa

Two hundred and thirty-nine cattle from Gauteng Province in South Africa were tested for various pathogens causing reproductive diseases includingbovine viral diarrhoea/mucosal disease (BVD/MD) virus, infectious bovine rhinotracheitis/infectious pustular vulvovaginitis (IBR/IPV) virus, Neospora caninum and Brucella abortus usingvarious tests. For BVD/MD virus, 49.37% tested positive, 74.47% for IBR/IPV virus, 8.96% for Neospora caninum and 3.8% for Brucella abortus. The result for Brucella abortus is higher than the national average, possibly due to the small sample size. A high seroprevalence of antibodies to both BVD/MD virus and IBR/IPV virus was evident. These 2 viruses should be considered, in addition to Brucella abortus, when trying to establish causes of abortion in cattle. The clinical significance of Neospora caninum as a cause of abortion in Gauteng needs further investigation. One hundred and forty-three bulls were tested for Campylobacter fetus and Trichomonas fetus, and a low prevalence of 1.4% and 2.1% respectively was found in this study. The clinical implications of these findings are discussed.     

牛病毒性腹泻病毒BVDV-JL株的分离与鉴定

本研究从吉林某牛场表现严重腹泻症状濒死牛的胸腺病料样品中分离一株病毒,该病毒在MDBK细胞中盲传4代无细胞病变产生,而通过RT-PCR和间接免疫荧光试验、微量血清中和试验检测表明该分离病毒株为牛病毒性腹泻病毒(BVDV),并命名为BVDV-JL.将BVDV-JL株F4代细胞培养液(10<'7.13>TCID<,50>/...     

Studies on the pathogenesis of a Chinese strain of bovine parainfluenza virus type 3 infection in Balb/c mice

To date, three genotypes A, B, and C of bovine parainfluenza virus type 3 (BPIV3) have been isolated from cattle and only limited studies on the pathogenesis of the genotype A of BPIV3 infection in calves and laboratory animals have been conducted. The pathogenesis of the genotypes B and C of BPIV3 infection in calves and laboratory animals have not been reported. To alleviate the difficulties associated with sourcing suitable calves for infection studies, the establishment of BPIV3 infection model using laboratory model animals could aid in increasing the knowledge of the pathogenesis of this virus. Therefore thirty Balb/c mice were intranasally inoculated with a Chinese BPIV3 strain SD0835 which was classified as genotype C. Virus replications in mice were demonstrated by using virus isolation and titration, immunofluorescent staining, and immunohistochemistry and had occurred in the respiratory tissues as early as 24h after intranasal inoculation. The results of immunofluorescent staining and IHC implicated that the lungs and tracheas might be the major tissues in which the SD0835 infected and replicated. The histopathologic examinations revealed that alveoli septa thickening and focal cellulose pneumonia were seen in the lungs of experimentally infected mice. The aforementioned results indicated that the SD0835 of the genotype C was pathogenic to Balb/c mice and the mouse infection model could cast light on the genotype C of BPIV3 infection process and pathogenesis.     

Sheep persistently infected with Border disease readily transmit virus to calves seronegative to BVD virus

Bovine viral diarrhea- and Border disease viruses of sheep belong to the highly diverse genus pestivirus of the Flaviviridae. Ruminant pestiviruses may infect a wide range of domestic and wild cloven-hooved mammals (artiodactyla). Due to its economic importance, programs to eradicate bovine viral diarrhea are a high priority in the cattle industry. By contrast, Border disease is not a target of eradication, although the Border disease virus is known to be capable of also infecting cattle. In this work, we compared single dose experimental inoculation of calves with Border disease virus with co-mingling of calves with sheep persistently infected with this virus. As indicated by seroconversion, infection was achieved only in one out of seven calves with a dose of Border disease virus that was previously shown to be successful in calves inoculated with BVD virus. By contrast, all calves kept together with persistently infected sheep readily became infected with Border disease virus. The ease of viral transmission from sheep to cattle and the antigenic similarity of bovine and ovine pestiviruses may become a problem for demonstrating freedom of BVD by serology in the cattle population.     

Changes in distribution and numbers of CD4+ and CD8+ T-lymphocytes in lymphoid tissues and intestinal mucosa in the early phase of experimentally induced early onset mucosal disease in cattle

Mucosal disease (MD), one sequelae of bovine virus diarrhoea virus (BVDV) infection, causes severe lesions in lymphoid tissues and mucosal surfaces. Lesions are associated with the presence of cytopathogenic (cp) BVDV and initially characterized by apoptotic cell death. The objective of this investigation was to determine if this cell death is mediated only by the cp BVDV, which is known to induce apoptosis in cell culture or if immune-mediated host reactions might also contribute. Early onset MD was experimentally induced in calves by inoculation of persistently viremic calves with a closely related cp BVDV. Calves were euthanized in the early phase of infection between days 5 and 13 post-inoculation and tissues from tonsils, lymph nodes, Peyer's patches, jejunum and colon were collected. Presence of cp BVDV antigen was correlated with distribution of lymphocyte subpopulations in consecutive cryostat sections. In the lymphoid tissues, cp BVDV antigen was predominantly found in the lymphoid follicles. The increase of infected cells with time post-inoculation was paralleled by a decrease of B-lymphocytes and an increase of CD4+ T-lymphocytes. An increased number of CD8+ T-lymphocytes was seen in progressed lesions only. In the intestinal mucosa, initially multifocal, later diffuse infection with cp BVDV was accompanied by a multifocal or diffuse increase of CD4+ T-lymphocytes, respectively. Numbers of IgA+ plasma cells and CD8+ T-lymphocytes were decreased. The common change observed in lymphoid tissues and mucosa was the increase of CD4+ T-lymphocytes in sites with lesions. This might indicate a cell-mediated immune response to the cp BVDV. Besides their helper function to other cells of the immune system, activated CD4+ T-lymphocytes might also exert cytotoxic activity, induce apoptosis in target cells via Fas/Fas ligand binding and thus contribute to the severity of tissue lesions in MD.     

Distribution of viral antigen and development of lesions after experimental infection with highly virulent bovine viral diarrhea virus type 2 in calves

OBJECTIVE: To correlate tissue distribution with development of lesions after experimental infection with a virulent strain of noncytopathic bovine viral diarrhea virus (BVDV) type 2 in calves. ANIMALS: Ten 14-day-old and two 2-month-old colostrum-deprived calves. PROCEDURE: Calves were intranasally inoculated with BVDV type-2 strain 1373 from an outbreak of clinically severe bovine viral diarrhea (BVD).Two 14-day-old calves served as noninfected controls. Two calves each were euthanatized on postinoculation days 3, 6, and 12, and 1 each on days 8, 9, 13, and 14. Tissues were collected for immunohistologic and histologic examination. RESULTS: Inoculated calves developed nonspecific clinical signs characterized by high fever and decreased numbers of leukocytes and thrombocytes. Viral antigen was detected focally in lymphoid tissues on day 3. On days 6, 8, 9, 12, and 14, viral antigen became increasingly widespread throughout organs and tissues. Viral antigen in lymphoid tissues was associated with severe depletion of all compartments. Lesions in other tissues were not well correlated with distribution of viral antigen. Depletion of lymphoid tissues was observed in a calf on day 13, but viral antigen had been cleared from most tissues and was detected in vascular walls only. CONCLUSIONS AND CLINICAL RELEVANCE: Infection with a virulent BVDV strain resulted in wide dissemination of viral antigen in host tissues. Severe lymphoid depletion developed in lymphoid tissues, whereas viral antigen was generally not associated with lesions in other tissues. Findings suggest that development of lesions in acute BVD is not solely a function of viral replication and is also attributable to host reaction to infection.     

Thrombocytopenia and hemorrhages in veal calves infected with bovine viral diarrhea virus

The relationship between bovine viral diarrhea virus (BVDV) infection and thrombocytopenia was studied in 18 veal calves experimentally infected with BVDV. All calves were free of BVDV, and 13 calves were free of serum neutralizing antibodies to BVDV before virus inoculation. Calves were inoculated at approximately 10 days of age, and platelet counts were monitored over a period of several weeks. Ten additional calves housed in close proximity were kept as uninoculated controls. A profound decrease in platelet counts by 3 to 11 days after inoculation was seen in all calves that had neutralizing antibody titers less than 1:32 before infection. Severe thrombocytopenia (less than 5,000 platelets/microliter) was seen in 12 calves, 11 of which also developed hemorrhages. Necropsy findings in 3 severely thrombocytopenic calves that died included multiple hemorrhages throughout the body. Calves that recovered had increased platelet counts, and in most instances, a corresponding increase in neutralizing antibody titers to BVDV. At 11 days after inoculation, BVDV was detected on platelets by use of immunofluorescence, but evidence of surface-bound immunoglobulin was not found. The results suggest that a nonimmunoglobulin-mediated method of platelet destruction or sequestration develops as a sequela to BVDV infection.