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1.
Multiple intranasal experimental Mycoplasma (M.) bovis infection was induced to 22 calves and resulted in clinical manifestations. M. bovis was re-isolated from 17 of 24 lungs which had been altered by pneumonia. Pasteurella haemolytica was the only pathogen isolated from the pathologically affected lung of one of the experimental animals. The haematogenic proliferation phase was successfully identified in 5 of 8 examined calves. Arthritis was not recordable from any of the experimental animals. Interstitial and catarrhal to catarrhal-purulent bronchopneumonias were the most common histological findings. Peribronchial lymphoid cell accumulations occurred frequently, as time passed from onset of infection. Antibodies against M. bovis were detected in blood serum of infected animals by means of film inhibition, as of the 3. week from infection, and by means of indirect haemagglutination, as of the 4. week from infection.  相似文献   

2.
Sixteen 3-week-old calves were intratracheally inoculated with Mycoplasma bovis. Follow-up consisted of regular bronchoalveolar lavages (BALs) and clinical examinations. Animals were slaughtered from 4 to 21 days after inoculation. Counts were made of the mycoplasmas and other bacteria systematically isolated from the BAL liquids and lung lobes after slaughter. On the 6th day, spectinomycin 20mg/kg was given intramuscularly in three repeated doses at 24h intervals to six randomly chosen calves. All animals had developed a persistent M. bovis infection with a maximum BAL count on the 6th day (start of treatment). Co-occuring Pasteurella multocida infection was found in most animals with a maximum rate on the 14th day. The extent of lung surface lesions varied widely (0-64%) but was greater in the later slaughtered calves. Average counts of M. bovis and P. multocida in the BAL liquids were lower in treated calves than in untreated ones but the difference was not statistically significant. However, M. bovis and P. multocida counts in the lungs of the treated group were significantly lower than in the untreated group (p=0.003 and 0.009, respectively).  相似文献   

3.
Mycoplasma (M.) bovis hyperimmune serum was subcutaneously injected to 16 of 26 calves repeatedly intranasally infected with M. bovis, during and/or after experimental infection. Antibody titres between 1:32 and 1:256 were recorded by means of indirect haemagglutination from the calves treated. Transmission of film-inhibitory antibodies failed to work. Neither clinical manifestations nor pathologico-anatomic alterations to the lungs of experimentally infected animals were mitigated by hyperimmune serum treatment. M. bovis, in high germ counts, was re-isolated from nasal swabs, trachea, pulmonary lymph nodes, and inflammatory lung tissue of both treated and untreated calves.  相似文献   

4.
Five of a group of six calves were inoculated with Mycobacterium bovis. Two more uninoculated calves were introduced to the group 84 days later. All the inoculated calves were subsequently shown to be excreting M bovis in nasal mucus. The uninoculated calf in the initial group of six became infected and subsequently excreted M bovis. The two uninoculated calves which were introduced later did not become infected. It was concluded that contact with nasal mucus from the infected cattle resulted in infection of the uninoculated calf and that the density of accommodation of animals excreting M bovis was an important factor in transmission of the disease.  相似文献   

5.
Clinical, bacteriological and serological examination of 35 calves from the age of 5 to 26 days was performed in a Holstein-Friesian dairy herd endemically infected with Mycoplasma bovis. M. bovis was isolated from 48.6% of nasal swabs taken from the calves at the age of 5 days, and from 91.4% of the same calves at the age of 26 days, indicating the gradual spread of infection. The isolation rate of Pasteurella multocida did not change much, and varied from 28.6 to 25.7%. No P. haemolytica could be detected. In addition to M. bovis and P. multocida, the herd was also infected with different viruses (including bovine viral diarrhoea virus, infectious bovine rhinotracheitis virus, bovine adenoviruses, parainfluenza-3 virus, and bovine respiratory syncytial virus) as a large proportion of the sera of newborn calves contained colostral antibodies against these viruses. In most of the newborn calves severe clinical signs (fever, depression, inappetence, hyperventilation, dyspnoea, nasal discharge and coughing) due to M. bovis infection developed. The clinical signs appeared already on the fifth day of life, and their incidence was the highest at the age of 10 to 15 days. Three calves (8.6%) died as a result of severe serofibrinous pneumonia. The surviving calves showed very poor weight gain (ranging from 1.5 to 3.5 kg) during the first two weeks of life.  相似文献   

6.
OBJECTIVE: To determine the efficacy of difloxacin, a novel fluoroquinolone antibiotic, in calves experimentally infected with Mannheimia haemolytica (formerly Pasteurella haemolytica). ANIMALS: Seventy-two 3-month-old Holstein calves. PROCEDURES: Calves were inoculated with M haemolytica intratracheally; after they developed clinical signs of pneumonic pasteurellosis, they were randomly assigned to 1 of 6 groups (n = 12/group). Calves in each group were treated with 10% difloxacin (2.5 or 5 mg/kg of body weight), 5% difloxacin (2.5 or 5 mg/kg), enrofloxacin (5 mg/kg), or saline (0.9% NaCl) solution (control group), once daily for 5 days, and clinical signs were scored daily. On day 15, calves were euthanatized, and the percentage of diseased lung tissue was calculated. Swab specimens of the lungs were submitted for bacterial culture. RESULTS: Mortality rate and percentage of diseased lung tissue were significantly higher and cure rate and average daily gain were significantly lower for control calves, compared with calves in the treatment groups; however, no significant differences were found among treatment groups. Mannheimia haemolytica was isolated from the lungs of 10 control calves and from at least 2 calves in each of the treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that difloxacin and enrofloxacin were equally effective for treatment of calves with experimentally induced pneumonic pasteurellosis. However, treatment of infected calves with difloxacin or enrofloxacin may not eliminate the organism.  相似文献   

7.
Two gnotobiotic calves were treated once with tilmicosin (20 mg kg-1) six hours before they were infected by the intratracheal route with Mycoplasma bovis and Pasteurella haemolytica serotype 1. This treatment prevented colonisation of the lungs by P haemolytica and considerably reduced colonisation by M bovis, and the clinical scores and the extent of pneumonic consolidation, compared with two untreated gnotobiotic calves, both of which had to be killed in extremis for humanitarian reasons within 24 hours of infection. In a second experiment, 10 conventionally reared calves were similarly exposed to infection and, at the onset of clinical disease, five were treated once with tilmicosin (20 mg kg-1). Colonisation by P haemolytica and M bovis, the clinical scores and extent of pneumonic consolidation were suppressed or greatly reduced in the treated compared with the untreated calves, one of which had to be killed in extremis two days after infection. It was concluded that tilmicosin had a beneficial effect.  相似文献   

8.
Five calves from tuberculosis free herds were each inoculated intranasally with 10(6) viable organisms of a field isolate of Mycobacterium bovis. Four of the calves developed acute tuberculosis. ELISAs employing protein and phosphatide extracts of M bovis as antigens were used to monitor the humoral response of the infected calves. Fourteen days after infection there was a dramatic increase in the level of antibodies demonstrated by the phosphatide antigen. This increase coincided with the first appearance of signs of the disease. The results suggest that the phosphatide antigen may be of potential value in detecting a humoral response, if present, in cattle infected with M bovis. The tests employing the protein antigen demonstrated a humoral response in only one of the infected calves and emphasises the importance of antigen selection to detect antibodies in tuberculous animals.  相似文献   

9.
Excretion of Mycobacterium bovis by experimentally infected cattle   总被引：4，自引：0，他引：4  
Three groups, each of five calves, four to seven months old, were inoculated intranasally with different numbers of Mycobacterium bovis. Infection was established readily in the calves which received an inoculum containing either 10(6) or 10(4) colony forming units (cfu). After every infection there was a lag period during which the organisms could not be isolated from specimens of nasal mucus. All the animals excreted M bovis and the time of commencement, quantity and duration of excretion appeared to be related to the inoculation dose. Excretion continued for many weeks, and for two calves excretion became intermittent over many months. All the calves which were given inocula of 92 cfu failed to develop the disease and no immunological responses were detected; however, M bovis was isolated from nasal secretions from one of these animals 100 days after inoculation.  相似文献   

10.
In a blind trial, alternate calves in six consecutive production batches of calves (total 70), on a farm with a high incidence of respiratory and reproductive disease, were allocated to treatment with either valnemulin or a placebo premix added to the milk from four days of age. The calves were weighed at the beginning and end of a 21-day period of medication. Blood samples and nasal swabs were taken and examined for the presence of Mycoplasma and Pasteurella species, and antibodies to viral agents. Clinical condition, rectal temperature, respiratory and other signs and refusals of milk were recorded daily. Dead calves were examined postmortem. The calves medicated with valnemulin gained weight more quickly, had fewer cases of Mycoplasma infection and fewer respiratory signs, and required fewer treatments with antibiotics than those in the placebo group.  相似文献   

11.
The epidemiology, therapy, and prevention of M. bovis infections are briefly reviewed. In a survey begun in 1982, M. bovis was found frequently in the respiratory tract [corrected] of veal calves and beef cattle with respiratory problems. In replacement calves infected with respiratory disease in dairy herds, however, the organism has only been detected since 1986. Respiratory tract specimens collected from calves with respiratory disease were submitted for examination for M. bovis from 1986 to 1991 and originated from 83 herds. Mycoplasma bovis was detected in specimens from 59 of the herds, 20% of which were dairy herds and 80% fattening herds. Arthritis caused by M. bovis was observed in 12 herds until July 1991. Since 1976 when the first mastitis outbreak caused by M. bovis was diagnosed, M. bovis has caused 14 more outbreaks. The number of diseased cattle varied from 1 tot 16 per farm, and clinical signs of mastitis varied from mild to severe. In all instances the infection has been eradicated from the herds. Because M. bovis can cause great losses in intensively reared cattle herds, it is advisable to separate purchased veal calves and beef cattle from dairy cattle to prevent further spread of M. bovis.  相似文献   

12.
Identification of Mycoplasmatales in pneumonic calf lungs   总被引：3，自引：0，他引：3  
Lungs from 153 calves with clinical signs of pneumonia were examined post-mortem (PM) for the presence of mycoplasmas and ureaplasmas during a 38-month period. Sixty-two percent of the cases were submitted during the months when wide fluctuations in climatic conditions occur. Using indirect fluorescent antibody tests (IFAT) and culture, mycoplasmas and/or ureaplasmas were detected in 63% of the lungs examined. Mycoplasma dispar was detected in 39%, M. bovis in 36%, Ureaplasma spp. in 22% and M. bovirhinis in 8.5% of the lungs. Thirty percent of the lungs were infected with more than one species; the most frequent combination was M. bovis, M. dispar and Ureaplasma spp. (10.5%). M. arginini, M. bovigenitalium and acholeplasmas were not cultured. M. dispar was shown to remain viable for up to 15 days PM in apical and cardiac lobes held at 4 degrees C and also was detected by IFAT in the same tissues for 49 days.  相似文献   

13.
When dexamethasone was administered intramuscularly to Hereford calves at the time of inoculation with Eimeria zurnii and E. bovis, there was no apparent effect on the resulting infection. Medication at the time of appearance of the clinical signs caused sufficient aggravation of the disease to result in the death of the animals. Administration of the drug after subsidence of the clinical signs did not cause a clinical relapse, but resulted in prolonged oocyst discharge in the feces. Treatment of uninoculated normal calves with dexamethasone caused a brief period of increased oocyst discharge without clinical signs.  相似文献   

14.
To establish the role of Mycoplasma bovis as an agent of respiratory disease in fattening calves, an epidemiologic study was undertaken. A recently validated commercially available ELISA was used to diagnose M. bovis infection by seroconversion in paired sera obtained for each animal at entry in the fattening herd and at follow-up seven weeks later. Management data as well as relevant clinical and epidemiological variables were prospectively recorded. The overall seroconversion rate observed among the 415 calves in 23 fattening herds on 13 farms was 54.7%. Significant risk factors for seroconversion were the mixing of fattening herds of different age groups (risk ratio RR 1.70, 95% confidence interval (CI) 1.48 to 1.96), and the presence of at least one seropositive animal in the fattening herd (RR: 2.02; CI: 1.69 to 2.40). The proportion of clinical episodes of respiratory disease attributable to M. bovis infection was 50.3%. The average weight gain during the observation period was reduced by 7.6% in seroconverting calves and these animals had about 2 times more antibiotics prescribed by a veterinarian than calves remaining negative for M. bovis throughout follow-up (RR 1.83). Maternal antibodies against M. bovis were detected in 39% of newborn calves born from seronegative cows and had a half-life of 20 days, potentially limiting the usefulness of vaccines against M. bovis in this age group.  相似文献   

15.
A study was conducted to determine whether measured doses of aflatoxin given under different schedules would influence the pathogenesis of Moraxella bovis induced infectious bovine keratoconjunctivitis (IBK). Calves were allotted to 4 groups (groups I-IV) of 9, 9, 9, and 8 calves, respectively. Group I calves were given aflatoxin for 11 consecutive days starting 5 days before their eyes were exposed to M. bovis. Group II calves were given aflatoxin for 5 consecutive days starting 7 days after their eyes were exposed to M. bovis. Group III calves were given aflatoxin for 5 consecutive days starting 21 days after their eyes were exposed to M. bovis. Group IV calves were not given aflatoxin; but their eyes were exposed to M. bovis on the same day as were the eyes of calves in groups I-III; these calves served as controls. Aflatoxin had little if any influence on the pathogenesis of IBK under the conditions of this study. The results did not rule out an exacerbating effect of M bovis infection on aflatoxicosis in calves. Calves with the highest concentration of aflatoxin in their blood had the more severe signs of aflatoxicosis. Possible reasons for the equivocal results are discussed.  相似文献   

16.
The objective of this study was to evaluate the therapeutic efficacy of azithromycin treatment of cryptosporidiosis in naturally infected calves under field conditions. Fifty Holstein calves with cryptosporidiosis infection were divided into 5 groups: 1 group (10 calves) was unmedicated and served as the control group and was given distilled water only, whereas the other groups (10 animals per group) were medicated orally with azithromycin at the doses of 500 (group 1), 1,000 (group 2), 1,500 (group 3), and 2,000 mg (group 4) PO once daily for 7 days. The animals were examined clinically and fecal samples were collected on the 1st (inclusion day), 7th, 14th, and 21st days of the study. Drug efficacy was assessed by evaluating diarrhea, oocyst shedding, and weight gains from days 1 to 21 (4 assessments). Significant differences were observed in reductions of oocyst shedding (P < .05) and the fecal diarrhea incidence (P < .05) in groups 3 and 4 when compared with groups 1 and 2 and the control group. Weight gain of medicated calves was significantly higher than that of the unmedicated calves throughout the study (P < .05). The drug significantly suppressed oocyst shedding and resulted in significant improvements in clinical signs. Therefore, this suppression may have significant effect on the reduction of environmental contamination by cryptosporidial oocysts. From the economic point view, authors suggest that the most effective dose of azithromycin for the treatment of cryptosporidiosis in calves should be at 1,500 mg/d for 7 days.  相似文献   

17.
OBJECTIVE: To evaluate efficacy of florfenicol in an induced model of infectious bovine keratoconjunctivitis, using a blinded randomized, controlled trial. ANIMALS: 48 male Holstein calves, 2 to 4 months old. PROCEDURE: Moraxella bovis infection was induced in all calves. When corneal ulcers developed, each calf was assigned randomly to 1 of 3 treatment groups, using a block design determined by corneal ulcer size (day 0). Calves were treated with florfenicol (20 mg/kg of body weight, IM) on days 0 and 2 (IM group; n = 16). Calves of a second group received a single dose of florfenicol (40 mg/kg, SC) on day 0 (SC group; n = 16). The third group of calves was not treated (control group; n = 16). Corneal ulcers were photographed, and each calf was assessed for 30 days after treatment for 10 clinical signs of infection. Corneal ulcer surface areas were measured, and clinical scores were calculated. Ocular secretions for microbiologic culture were obtained weekly from each eye. RESULTS: A Cox regression model indicated that, after adjustment for initial ulcer size, healing rates were 6.2 and 4.8 times greater in calves of the IM and SC groups, respectively, compared with the control group. Clinical scores and surface area measurements for treatment groups were significantly smaller than those for controls during posttreatment weeks 1 through 4. From day 8 through day 29, M bovis was isolated from ocular secretions of 14 of 16 control calves and 1 of 32 treated calves. CONCLUSIONS AND CLINICAL RELEVANCE: Parenterally administered florfenicol reduces corneal ulcer healing time, lessens clinical severity, and reduces the amount of bacterial shedding from calves infected with M bovis.  相似文献   

18.
Mycoplasma bovis is perceived as an emerging cause of mortality in feedlot beef cattle. This study examined the lesions and infectious agents in naturally occurring M. bovis-associated bronchopneumonia and arthritis and the relationship of this condition with bovine viral diarrhea virus (BVDV) infection. Standardized pathologic, immunohistochemical, and microbiologic investigations were conducted on 99 calves that died or were euthanized within 60 days after arrival in 72 feedlots. Cranioventral bronchopneumonia with multiple foci of caseous necrosis was identified in 54 of 99 calves, including 30 with concurrent fibrinosuppurative bronchopneumonia typical of pneumonic pasteurellosis. Mycoplasma bovis was consistently identified in these lesions by culture and immunohistochemistry, but also commonly in healthy lungs and those with pneumonia of other causes. Focal lesions of coagulation necrosis, typical of pneumonic pasteurellosis, were often infected with both Mannheimia haemolytica and M. bovis. Arthritis was present in 25 of 54 (46%) calves with M. bovis pneumonia, and all calves with arthritis had pneumonia. BVDV infection was more common in calves with lesions of bacterial pneumonia than in those dying of other causes, but BVDV infection was not more common in calves with caseonecrotic bronchopneumonia than those with fibrinosuppurative bronchopneumonia. Retrospective analysis identified cases of M. bovis pneumonia in the early 1980s that had milder lesions than the current cases. The findings suggest that, in at least some calves, M. bovis induces caseonecrotic bronchopneumonia within the lesions of pneumonic pasteurellosis.  相似文献   

19.
Between 1997 and 2000, a total of 150 healthy cattle and 238 animals with respiratory disease were examined for six Mycoplasma species. Attempts were made to detect Mycoplasma canis, Mycoplasma dispar and Ureaplasma diversum in calves with recurrent disease, and all three of these species were identified in calves with recurrent disease and in healthy lungs. In healthy calves, 84 per cent of bronchoalveolar lavage fluids were mycoplasma free; when cultures were positive, Mycoplasma bovirhinis was the only species isolated. Mycoplasmas were isolated from 78 per cent of animals suffering recurrent respiratory disease and from 65 per cent of acute respiratory cases. Mycoplasma bovis was isolated from bronchoalveolar lavages from 35 per cent of calves suffering recurrent respiratory disease, and from 50 per cent of acute cases, and from 20 per cent of pneumonic cases examined postmortem. M bovis was associated with other Mycoplasma species in 44 per cent of cases. M dispar was also isolated from 45.5 per cent of calves suffering recurrent respiratory disease, often in association with M bovis. M canis was identified for the first time in diseased Belgian cattle. Other mycoplasmas, including Mycoplasma arginini, Mycoplasma alkalescens and U diversum, were isolated less frequently. Associations between mycoplasmas and other pathogens were often observed. Among lungs infected with Pasteurella and/or Mannheimia species, more than 50 per cent were mixed infections with M bovis.  相似文献   

20.
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.  相似文献   

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