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1.
Infection of clinically susceptible ruminants, including domesticated cattle and American bison, with ovine herpesvirus 2 (OvHV-2) can result in the fatal lymphoproliferative and vasculitis syndrome known as malignant catarrhal fever (MCF). A reliable experimental infection model is needed to study the pathogenesis of MCF and to develop effective vaccination strategies to control the disease. An experimental aerosol infection model using sheep, the natural carriers of OvHV-2, has been developed (Taus et al., 2005). Using the protocol and OvHV-2 inoculum established in the previous study, eight calves were nebulized with four different doses of OvHV-2 in nasal secretions from infected sheep. Two control calves were nebulized with nasal secretions from uninfected sheep. Infection status of all calves was monitored using competitive inhibition ELISA, PCR and clinical parameters. Six of eight nebulized calves became infected with OvHV-2. One calf receiving the highest dose of virus developed typical clinical, gross and histological changes of MCF. This study showed that nasal secretions collected from sheep experiencing OvHV-2 shedding episodes were infectious for cattle and capable of inducing MCF. The data also indicate that cattle are relatively resistant to disease following infection. The use of more susceptible species as experimental animal models, such as bison and selected cervid species should be examined.  相似文献   

2.
Twenty-two heifers were infected intranasally with non-cytopathic bovine viral diarrhoea virus (BVDV) between days 74 and 82 of pregnancy. All animals had developed serum antibodies against BVDV 5 weeks later. No clinical effects were seen in the heifers, and they all delivered a live calf. The newborn calves were generally small, appeared unthrifty as typical 'poor doers', and some developed secondary infections with diarrhoea and signs of respiratory disease. Eighteen of the 22 calves were born without antibodies against BVDV and were persistently infected (PI) with the virus. One was weak at birth and died the following day. Four calves were born with serum antibodies against BVDV and with no detectable virus. Three of these showed signs and/or pathological changes indicating disease in the central nervous system. Otherwise, there were no obvious clinical differences between these calves and the PI calves, nor were there any apparent significant differences in blood parameters between these groups. In general, the calves showed low gamma-globulin values and thrombocytopaenia, but moderately increased fibrinogen values and relatively normal lymphocyte numbers.  相似文献   

3.
Malignant catarrhal fever (MCF. corrizza contagiosa) is an invariably fatal communicable disease in cattle, whose causative agent is the ovine herpes virus-2, or the alcelaphine herpes virus-1. In one feed-lot family farm, 34 calves out of 100 became ill at the rate of one to four calves per week, and all of them subsequently died over a period of 4 months. Most of the initial cases were manifested clinically as the head and eye form, but most of the entire clinical spectrum of forms (the respiratory, intestinal and nervous forms) characteristic for MCF were observed as this epidemic progressed. Very few calves died without showing any specific signs of MCF. Pathological examinations revealed characteristic obliterative arteriovasculitis in the brain of calves with nervous signs, typical of MCF. Polymerase chain reaction (PCR) testing revealed 100% homology between the 238 bp hemi-nested PCR fragment and the ovine herpes virus-2 sequences. Based on the clinical signs, epidemiological data, pathological, and histopathological findings, and the PCR results, it was concluded that MCF occurred on the farm. The fact that sheep and goats were housed in close proximity on the same farm reinforced this diagnosis.  相似文献   

4.
Experimental Salmonella typhimurium infection in calves.   总被引：6，自引：0，他引：6  
The paper describes the clinical, bacteriological and pathological findings in experimental Salmonella typhimurium infection in calves. Oral doses of 10(8) and 10(9) organisms produced clinical disease and high mortality; doses ranging from 10(4)--10(7) organisms were less consistent in their action. Jersey calves appeared more susceptible to infection than Friesian calves. The clinical signs in most calves were pyrexia and a characteristic diarrhoea that lasted for up to 11 days; more severe symptoms were seen in the calves that received the higher doses. Following infection, all calves excreted S typhimurium in their faeces, the highest counts being observed in the calves that died. In the calves that survived, counts ranging from 10(2)--10(5)/g faeces occurred continuously for up to a maximum of 20 days and subsequent intermittent excretion occurred in a number of calves. In the calves that died, necrotic enteritis in the ileum and large intestine was the most striking lesion; lesions were uncommon in other organs. The findings are discussed in relation to the pathogenesis, diagnosis and control of the disease.  相似文献   

5.
Fourteen calves, 14 weeks old, fed a low vitamin E and selenium diet based on sodium hydroxide-treated, selenium-deficient barley showed a rapid decline in plasma alpha-tocopherol, a gradual decline in erythrocyte glutathione peroxidase (GSHPX) activity, elevated plasma creatine kinase (CK) activity, teeth grinding and (in three cases) electrocardiographic changes, but no clinical abnormalities after 127 to 137 days. Necropsy of six depleted calves at that stage revealed pale muscles in two animals and mild histopathological lesions of skeletal myopathy in all six calves. Ten control calves were fed a similar diet supplemented with alpha-tocopherol and selenium. Plasma alpha-tocopherol and erythrocyte GSHPX activity remained high in these calves and no clinical abnormalities or evidence of myodegeneration were observed. When protected linseed oil was fed as a source of polyunsaturated fatty acids to the remaining eight depleted calves, rapid elevations in plasma CK activity and linolenic acid associated with a variety of cardiopulmonary and locomotory signs, electrocardiographic changes and myoglobinuria occurred within six to 11 days. Necropsy revealed widespread severe skeletal myodegeneration (eight calves) and myocardial lesions (five calves) with preferential involvement of the left ventricular myocardium. Clinical signs and pathological changes were similar to those reported in field outbreaks of nutritional degenerative myopathy in ruminant cattle and establish the experimental regime as the first successful model for reproduction of this disease.  相似文献   

6.
Experimental production of bovine pneumonic pasteurellosis   总被引：1，自引：0，他引：1  
Pneumonic pasteurellosis has been reproduced in conventional, weaned, Friesian-cross calves using a strain of Pasteurella haemolytica biotype A, serotype 1 (P haemolytica A1) isolated from a pathologically confirmed incident of bovine pneumonic pasteurellosis. The major clinical findings were pyrexia, hyperpnoea, tachypnoea, nasal discharge and reduced appetite. Fibrinous pneumonia was present in the lungs of animals at necropsy on days 2 and 3 after initial infection while by days 9 and 10 after initial infection many of the areas of fibrinous pneumonia were confined by a fibrous capsule forming well defined nodules. During the experiment natural transmission of the infecting strain of P haemolytica A1 occurred in two control calves which developed a condition identical to that in the artificially infected calves. P haemolytica A1 was repeatedly recovered from the nasopharynx of infected calves and at necropsy throughout the upper and lower respiratory tracts. Seroconversion, as measured by indirect haemagglutination, to the organism developed in all infected calves by days 9 and 10 after initial infection. The clinical, microbiological and pathological findings were identical to those seen in field incidents of bovine pneumonic pasteurellosis involving recently housed, weaned, single-suckled calves.  相似文献   

7.
Sheep-associated malignant catarrhal fever (MCF) due to infection with ovine herpesvirus 2 (OvHV-2) is common in commercial herds of American bison ( Bison bison). Inability to propagate OvHV-2 in vitro has been a constraint on experimental studies of the disease. We sought to establish whether nasal secretions from sheep that shed OvHV-2 might induce the disease in bison and to define a minimum challenge dose. Fourteen bison were nebulized with sheep nasal sections containing 10(3)-10(7) OvHV-2 deoxyribonucleic acid (DNA) copies. Most challenged bison (11/14, 78.6%) developed clinical signs at 29-52 days postnebulization (DPN). The mean incubation time was 42.18 (+/-7.33 SD) DPN. Using real-time polymerase chain reaction, we detected OvHV-2 DNA in peripheral blood leukocytes at 21-31 DPN. All bison that developed MCF had antibodies against the MCF group viruses. Gross and histologic lesions were typical of the acute disease. There was no morphologic evidence of a dose-related difference in the severity or distribution of lesions. This is the first successful reproduction of MCF in bison using a nasal route of exposure. Experimentally challenged bison are more susceptible to MCF, compared with experimentally challenged domestic cattle in a previous experiment. Bison are a pertinent ruminant species in which the pathogenesis of the disease can be investigated.  相似文献   

8.
Three experiments have been carried out to verify the effectiveness of an immunomodulator, Baypamun (Bayer AG) in limiting the spread of Bovine herpesvirus-1 (BHV-1), the causal agent of infectious bovine rhinotracheitis (IBR). In the first experiment, four calves infected with BHV-1 developed severe disease whereas four calves given Baypamun simultaneously with the virus had less severe disease. Four other calves in contact with the infected calves became severely ill but another four given Baypamun were only mildly affected. In the second experiment three calves infected with BHV-1, which reacted with typical disease, were allowed to remain in contact with six calves. All six calves were given Baypamun at various times following the exposure to BHV-1 infection and all showed a much reduced reaction with two treated for 4 days developing no clinical disease. Finally, in the third experiment one calf vaccinated one month before the start of the experiment did not develop any signs of disease when housed together with a calf experimentally infected with BHV-1. Of four other calves, vaccinated when the infected calf showed the first signs of disease, only the two given Baypamun in addition to the vaccine, were protected from clinical disease whereas the two given vaccine only developed classical signs of IBR. In the three experiments the virus shedding by the Baypamun-treated calves resulted to be significantly reduced.  相似文献   

9.
The present report describes the clinical, pathological, serological and virological findings in calves from 2 larger Danish beef herds experiencing outbreaks of pneumonia. The calves had been vaccinated with an inactivated bovine respiratory syncytial virus (BRSV) vaccine 2 months prior to the outbreak. The clinical signs comprised nasal discharge, pyrexia, cough and increased respiratory rates. A total of 28 calves died in the 2 herds. The laboratory investigations revealed that BRSV was involved and probably initiated both outbreaks. Furthermore, the serological results suggested that the vaccine induced only sparse levels of antibodies probably due to the presence of maternally derived antibodies at the time of vaccination. Necropsy findings in 5 calves revealed changes typical for infectious pneumonia with involvement of BRSV. In conclusion, vaccination of calves against BRSV in 2 Danish beef herds failed to protect the calves against severe or even fatal BRSV mediated respiratory disease 2 months later.  相似文献   

10.
An in vitro bactericidal assay that used bovine heparinized blood was investigated for its usefulness in detecting differences in the bactericidal immunity of calves against Pasteurella haemolytica serotype 1 (Ph1). Greater than 90% of killing occurred within 30 minutes. The substitution of fetal calf serum for autologous calf plasma caused loss of bactericidal activity of the blood. Decomplemented calf serum also was low in bactericidal activity. The blood bactericidal assay appears to be opsonin antibody-dependent and complement-dependent. The coefficient of variation (CV) that can be expected with this assay was established by use of a group of 8 calves; within-day CV maximum was 0.9, and between-day CV maximum was 2.1. The blood bactericidal assay was used to evaluate 30 calves under typical market stress from 4 farms in eastern Tennessee. All calves had decreased bactericidal activity, as they moved into a feedyard in Texas. The bactericidal activity was reduced among sick calves, based on the severity of clinical signs. Morbidity was highest during the first 14 days in the feedlot. During this period, healthy calves had a decreased bactericidal index (BI) of 4 points, and calves with clinical signs of bovine respiratory tract disease for 3 days had a decreased BI of 8 points. The average reduction in the BI of calves with clinical signs of bovine respiratory tract disease for 6 or more days was 14 points.  相似文献   

11.
OBJECTIVE: To determine whether experimental inoculation with a field strain of epizootic hemorrhagic disease virus serotype-2 (EHDV-2) suspected of causing clinical disease in naturally infected cattle would cause clinical disease in calves. ANIMALS: 8 calves. PROCEDURE: A strain of EHDV-2 isolated from a white-tailed deer that died of hemorrhagic disease was passaged twice in deer and used to inoculate 6 calves SC and ID; the other 2 calves were used as controls. Physical examinations, CBC, lymphocyte blastogenesis assays, and coagulation assays were performed; rectal temperature, interferon production, and serum neutralizing antibody responses were measured; and virus isolation was attempted every other day for 21 days after inoculation and then every fourth day for another 30 days. Calves were euthanatized on postinoculation day 51, and necropsy was performed. RESULTS: Calves inoculated with EHDV-2 became infected, as evidenced by development of viremia and seroconversion. However, the virus did not cause detectable clinical disease, clinicopathologic abnormalities, or gross lesions. Viremia was prolonged despite development of a serum neutralizing antibody response. A white-tailed deer inoculated with the same EHDV-2 strain developed clinical signs of epizootic hemorrhagic disease, demonstrating that the inoculum was virulent. CONCLUSION: Calves experimentally infected with EHDV-2 developed viremia and seroconverted but did not develop detectable clinical disease.  相似文献   

12.
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.  相似文献   

13.
OBJECTIVE: To determine whether a combination viral vaccine containing modified-live bovine herpesvirus-1 (BHV-1) would protect calves from infection with a recent field isolate of BHV-1. DESIGN: Randomized controlled trial. ANIMALS: Sixty 4- to 6-month-old beef calves. PROCEDURE: Calves were inoculated with a placebo 42 and 20 days prior to challenge (group 1; n = 10) or with the combination vaccine 42 and 20 days prior to challenge (group 2; 10), 146 and 126 days prior to challenge (group 3; 10), 117 and 96 days prior to challenge (group 4; 10), 86 and 65 days prior to challenge (group 5; 10), or 126 days prior to challenge (group 6; 10). All calves were challenged with BHV-1 via aerosol. Clinical signs, immune responses, and nasal shedding of virus were monitored for 14 days after challenge. RESULTS: Vaccination elicited increases in BHV-1-specific IgG antibody titers. Challenge with BHV-1 resulted in mild respiratory tract disease in all groups, but vaccinated calves had less severe signs of clinical disease. Extent and duration of nasal BHV-1 shedding following challenge was significantly lower in vaccinated calves than in control calves. In calves that received 2 doses of the vaccine, the degree of protection varied with the interval between the last vaccination and challenge, as evidenced by increases in risk of clinical signs and extent and duration of viral shedding. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that this combination vaccine provided protection from infection with virulent BHV-1 and significantly reduced nasal shedding of the virus for at least 126 days after vaccination.  相似文献   

14.
Calves were inoculated intranasally with 2 X 10(6.2) tissue culture infective doses of infectious bovine rhinotracheitis virus, followed in 7 days by intratracheal inoculations with 1 of 4 challenge doses of pathogenic Pasteurella haemolytica. Severity and duration of the ensuing clinical signs of respiratory tract disease were correlated with the challenge dose of bacteria. Calves given 1 X 10(6) colony-forming units (CFU) of bacteria did not develop reliable clinical evidence of disease, whereas those given 1 X 10(8) CFU or 1 X 10(10) CFU of bacteria developed clinical signs of pneumonic pasteurellosis within 12 to 24 hours of bacterial challenge. Severity of clinical signs was equal at the 10(8) and 10(10) doses of bacteria, but duration of clinical signs was greater in calves given the 10(10) dose. Calves given 1 X 10(12) CFU of bacteria developed relatively severe respiratory tract disease in excess of what was necessary for positive clinical detection. Positive correlations were found between the bacterial challenge dose and the height and duration of increased rectal temperature, amount and duration of increases in ocular and nasal discharges, and the subjective evaluation of depressed attitude and appetite. Correlations were not found between challenge dose and respiratory rate or character, or between challenge dose and complete blood cell count. Convalescent calves were resistant to naturally occurring pneumonic pasteurellosis, which caused severe disease in nontreated calves. Adverse effects of P haemolytica were not observed after the first 4 to 15 days after bacterial administration; however, the bacteria were isolated from nasal secretions of convalescent calves 89 to 116 days after bacterial inoculation.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

15.
The toxicity of Riddell groundsel (Senecio riddellii) gavaged to calves at a known lethal rate was compared with the toxicity of riddelliine and riddelliine N-oxide, the pyrrolizidine alkaloids isolated from the plant, which were fed by intraruminal infusion. Doses of the alkaloids were adjusted to the amount determined to be in the plant and fed individually and in combination. The relative toxicosis in the calves was measured by clinical signs, serum enzyme changes, survival time to morbidity, and histologic changes. Calves fed Senecio riddellii by gavage for 20 consecutive days to provide 45 mg of total pyrrolizidine alkaloids/kg of body weight/d developed clinical signs and serum enzyme changes typical of seneciosis, with 100% morbidity. However, calves receiving riddelliine at 4.5 mg/kg/d for 20 days had neither serum enzyme changes nor clinical signs of pyrrolizidine alkaloidosis. Calves treated with riddelliine N-oxide (40.5 mg/kg/d), and with riddelliine (4.5 mg/kg/d) and riddelliine N-oxide (40.5 mg/kg/d) in combination, had 100% morbidity, although the latter group had fewer liver lesions. These results establish that the N-oxide form of the alkaloid alone is capable of inducing typical Senecio toxicosis in cattle and that the free base level of the plant cannot be considered to be the sole factor in assessing the toxicity of S riddellii.  相似文献   

16.
The pathogenicity of a field strain, 417, of bovine ephemeral fever (BEF) virus for newborn and young calves was investigated. Three colostrum-deprived newborn calves inoculated intravenously developed severe clinical disease and viraemia, and produced long-lasting neutralising antibody. The incubation period in these animals was 10 and 11 days, compared with 5 to 7 days for older calves. Two newborn calves which received colostrum from immune dams and 2 which received colostrum from non-immune dams failed to respond clinically to intravenous inoculation with strain 417. The neutralising antibody response of these calves was of short duration. Four calves, 7 to 8 weeks old and lacking detectable neutralising antibody to BEF virus, or having low levels of antibody, did not develop clinical disease when inoculated intravenously. Four calves 12 to 14 weeks of age and free of detectable neutralising antibody to BEF virus developed clinical disease when inoculated with strain 417.  相似文献   

17.
Transmissibility of Mycoplasma mycoides subsp. mycoides infection from experimentally inoculated goats to other goats and calves was studied. Eight goats and six calves were housed in an 18 m2 room. Six of the goats were inoculated endobronchially with strain D44 isolated from a natural case of polyarthritis in Ontario. These six goats died within a week of Mycoplasma septicemia. The two contact goats or the six calves never showed signs of disease and M. mycoides subsp. mycoides was not recovered from these animals. The contact goats and four calves were killed 25 days after exposure. They were all seronegative, M. mycoides subsp. mycoides was not recovered at necropsy and none had pathomorphological changes attributable to this Mycoplasma. The two remaining calves were inoculated endobronchially with 10(9) CFU of strain D44 and observed for 20 days. They never showed signs of disease and did not have significant lesions at necropsy. Both developed a significant serological response to M. mycoides subsp. mycoides, although this organism was not recovered during the experimental period or at necropsy. This study did not provide evidence for transmission of M. mycoides subsp. mycoides from endobronchially inoculated goats to contact goats or calves and endobronchially inoculated calves did not develop pneumonia. This would suggest that the infection of the goat population in Canada with this pathogen would not be a significant threat to the cattle population.  相似文献   

18.
BACKGROUND: Bovine viral diarrhea virus (BVDV) infection is one of the causes of hemorrhagic diathesis in cattle but there have been limited field studies about that condition. HYPOTHESIS: To identify the cause of hemorrhagic diathesis in calves and describe its clinical findings. ANIMALS: Five calves from a farm with 150 dairy cows. METHODS: Clinical examination of the calves was performed. After blood samples were obtained from 2 calves, whole blood, sera, and leukocyte samples were used for hematologic and hemostatic examinations, neutralization tests, virus isolation, and viral genome sequencing. RESULTS: The calves had moderate pyrexia, dullness, serous or mucous nasal discharge, and petechial and ecchymotic hemorrhages on mucosal surfaces. Severe thrombocytopenia and anemia were identified on hematologic examinations. All calves died within 10 days of the onset of clinical signs. Virologic examinations identified BVDV as the causative agent of the disease. CONCLUSIONS AND CLINICAL IMPORTANCE: This paper identifies a hemorrhagic syndrome-like disease in calves with bovine viral diarrhea and mucosal disease complex in Turkey.  相似文献   

19.
Pseudorabies virus (PRV) was not transmitted horizontally from 3 PRV-infected calves to 2 contact control calves during 4 days of comingling in experiment 1. Although these contact control calves developed clinical signs of pseudorabies when infected intranasally with PRV in experiment 2, they did not transmit PRV to a second pair of contact control calves. However, 1 of 2 pigs comingled with these 4 calves seroconverted. During both experiments, moderate amounts (10(2) to 10(5) TCID50) of PRV were present in the nasal secretions of the infected calves during the contact periods. All infected calves traumatized their nares or periorbital tissue. Infected calves developed a nonsuppurative meningoencephalitis mainly involving the brain stem. Four of the 5 infected calves had nonsuppurative ganglioneuritis and acute lymphoid necrosis of germinal centers. Virus could not be recovered from nasal and tonsillar swab samples from contact-control calves and pigs.  相似文献   

20.
A series of experimental trials on methods of treatment and prevention of shimao zheng fleece-eating) were carried out using various sulphates. The results confirmed the hypothesis that this is a local nutritional and metabolic disease, caused mainly by a sulphur deficiency, that could be prevented or cured with supplementary sulphur in the diet. In field studies, the clinical signs virtually disappeared within 14 days of the animals receiving medicated pellets. Over the same period, the concentrations of sulphur in the blood, liver and spleen returned to normal and the pathological changes in the skin improved. The condition of the controls became worse in each of these respects over this time. However, the pathological changes in the musculature were not alleviated by the treatment.  相似文献   

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