Clinical study of the disease of calves associated with Mycoplasma bovis infection

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.     

Pneumonia in calves: characterization of the bacterial spectrum and the resistance patterns to antimicrobial drugs

The population under study included young calves with pneumonia (group A, n = 13) and their controls (group B, n = 9), as well as older calves from which the lungs with (group C, n = 90) or without (group D, n = 10) lesions were collected after slaughter. Arcanobacterium pyogenes was the organism most commonly isolated from calves in group A (46%), followed by Haemophilus somnus (23%), Mannheimia haemolytica (15%), Streptococcus suis and Pasteurella multocida (7.7% each). Only S. suis (22%) and P. multocida (11%) were found in group B. P. multocida was isolated from 32% group C calves, H. somnus from 11%, A. pyogenes from 7.8%, M. haemolytica from 2.2% and S. suis from 1.1%. No specific pathogens were isolated in group D. Prevalence of Mycoplasma bovis infection was 69% in group A and 37% in group C. Ninety-eight strains were tested for resistAnce to antibiotics. Resistance to penicillin and ampicillin was present only in M. haemolytica (46%). High percentages of resistant strains were observed for streptomycin (48-100%), tetracycline (15-43%), sulfonamides alone (14-100%) or in combination with trimethoprim (0-100%). Therapeutic approaches to bacterial calf pneumonia in the area under study should be modified according to the isolated bacterial population, the observed antimicrobial resistances and the growing importance of Mycoplasma bovis.     

Safety and efficacy testing of a novel multivalent bovine bacterial respiratory vaccine composed of five bacterins and two immunogens

Bovine bacterial respiratory diseases have been one of the most serious problems due to their high mortality and economic loss in calves. The vaccinations of bovine bacterial respiratory vaccines have been complex because of no multivalent vaccine. In this study, novel multivalent bovine bacterial respiratory vaccine (BRV) was developed and tested for its safety and efficacy. BRV was composed of two immunogens and five bacterins. These were leukotoxoid and bacterin of Mannheimia haemolytica type A, outer membrane protein and bacterin of Pasteurella multocida type A, and bacterins of Haemophilus somnus, Mycoplasma bovis, and Arcanobacterium pyogenes. ELISA antibody titers to five bacterial antigens in vaccinated guinea pigs increased, compared with those in unvaccinated ones. BRV was safe for calves and pregnant cattle in this study. In calves challenged with M. haemolytica and P. multocida, the average daily weight gain and antibody titers of vaccinated calves increased, and respiratory symptoms (P<0.05) and treatment frequency (P<0.01) of vaccinated calves significantly decreased, compared with those of unvaccinated calves. Interestingly, the antibody titers of M. haemolytica leukotoxoid and Mycoplasma bovis were closely related with the reduction of respiratory symptoms. BRV would be an ecomonical measure for the protection against bovine bacterial respiratory diseases.     

Diseases and pathogens associated with mortality in Ontario beef feedlots.

This study determined the prevalence of diseases and pathogens associated with mortality or severe morbidity in 72 Ontario beef feedlots in calves that died or were euthanized within 60 days after arrival. Routine pathologic and microbiologic investigations, as well as immunohistochemical staining for detection of bovine viral diarrhea virus (BVDV) antigen, were performed on 99 calves that died or were euthanized within 60 days after arrival. Major disease conditions identified included fibrinosuppurative bronchopneumonia (49%), caseonecrotic bronchopneumonia or arthritis (or both) caused by Mycoplasma bovis (36%), viral respiratory disease (19%), BVDV-related diseases (21%), Histophilus somni myocarditis (8%), ruminal bloat (2%), and miscellaneous diseases (8%). Viral infections identified were BVDV (35%), bovine respiratory syncytial virus (9%), bovine herpesvirus-1 (6%), parainfluenza-3 virus (3%), and bovine coronavirus (2%). Bacteria isolated from the lungs included M. bovis (82%), Mycoplasma arginini (72%), Ureaplasma diversum (25%), Mannheimia haemolytica (27%), Pasteurella multocida (19%), H. somni (14%), and Arcanobacterium pyogenes (19%). Pneumonia was the most frequent cause of mortality of beef calves during the first 2 months after arrival in feedlots, representing 69% of total deaths. The prevalence of caseonecrotic bronchopneumonia caused by M. bovis was similar to that of fibrinosuppurative bronchopneumonia, and together, these diseases were the most common causes of pneumonia and death. M. bovis pneumonia and polyarthritis has emerged as an important cause of mortality in Ontario beef feedlots.     

Genetic analysis of virulence factors of Mannheimia (Pasteurella) haemolytica A1

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).     

Gelatinolytic matrix metalloproteinases-2 and -9 in tracheobronchial lavage fluid obtained from calves with concurrent infections of Pasteurella multocida and Mycoplasma bovirhinis

OBJECTIVE: To study gelatinolytic matrix metalloproteinases (MMPs) in tracheobronchial lavage fluid (TBLF) obtained from clinically normal calves and calves with Pasteurella multocida infection. SAMPLE POPULATION: Samples of TBLF obtained from 11 calves with clinical signs of respiratory tract disease and growth of P multocida and Mycoplasma spp during culture of TBLF and samples of TBLF from 6 clinically normal calves with no bacterial growth during culture of TBLF. PROCEDURE: MMPs in TBLF were analyzed by use of gelatin zymography. Gelatinases were identified on the basis of molecular weights and inhibition by EDTA. RESULTS: The main gelatinolytic MMPs detected were the proform (90 to 110 kd) and active form (75 to 85 kd) of MMP-9 (gelatinase B) and the proform (67 to 75 kd) and active form (< 65 kd) of MMP-2 (gelatinase A). Increased amounts of active MMP-2 and MMP-9 were detected in TBLF of calves with respiratory tract disease, compared with amounts of active MMP-2 and MMP-9 in TBLF of clinically normal calves. Concurrent infection with Mycoplasma bovirhinis in calves with pneumonia attributable to P multocida was associated with higher concentrations of MMP-9. CONCLUSIONS AND CLINICAL RELEVANCE: The host response to P multocida includes increases in MMP-2 and MMP-9 concentrations in TBLF. Greater amounts of MMPs detected in calves with concurrent M bovirhinis and P multocida infection indicates synergism between these organisms.     

Protection against respiratory disease in calves induced by vaccines containing respiratory syncytial virus, parainfluenza type 3 virus, Mycoplasma bovis and M dispar

A field trial to assess the ability of two vaccines to protect calves against respiratory disease was carried out on a large beef rearing unit in southern England over the two winters of 1983 to 1984 and 1984 to 1985. A quadrivalent vaccine containing the killed antigens of respiratory syncytial virus, parainfluenza virus type 3, Mycoplasma bovis and M dispar or a vaccine containing only the respiratory syncytial virus component were inoculated into 246 and 245 calves, respectively; 245 calves remained as unvaccinated controls. The calves were reared in seven batches and outbreaks of disease occurred in five; significant protection was achieved in the four batches in which disease was associated with respiratory syncytial virus and M bovis infection, together or independently. The death rate from pneumonia was 9 per cent in the control group, 2 per cent in the calves inoculated with the quadrivalent vaccine (P less than 0.001), a protection rate of 77 per cent, and 3 per cent in the calves inoculated with the respiratory syncytial virus vaccine (P less than 0.01), a protection rate of 68 per cent. The proportion of calves receiving treatment for respiratory disease was 38 per cent in the control group, 25 per cent in the calves inoculated with the quadrivalent vaccine (P less than 0.001) and 27 per cent in the calves inoculated with the respiratory syncytial virus vaccine (P less than 0.01). The results show that protection against respiratory disease can be achieved by parenteral vaccination of calves with the appropriate inactivated microorganisms.     

宁夏固原部分地区肉犊牛呼吸道6种病原流行病学调查

[目的]为了掌握宁夏固原地区示范村杨坪村和马沟村的肉犊牛呼吸道疾病的流行情况,[方法]2019年-2021年对2村犊牛呼吸道疾病发病情况进行统计并采用分子生物学技术对采集的犊牛呼吸道鼻拭子样本进行6种病原的鉴定。[结果] 2019年-2021年杨坪村犊牛呼吸系统疾病发病率呈下降趋势,但不同年份间差异不显著(p>0.05);马沟村犊牛呼吸系统疾病发病率呈下降趋势,2021年与2019年相比差异显著(p<0.05)。2019年-2021年,病毒性呼吸道疾病呈下降趋势,而牛支原体和多杀性巴氏杆菌由于没有有效的疫苗预防而呈现较高的阳性率。[结论]本研究揭示了牛支原体和多杀性巴氏杆菌为目前犊牛主要的呼吸道致病病原,做好牛支原体病和多杀性巴氏杆菌病的预防、早期诊断和治疗可有效降低犊牛呼吸道疾病的发病率。     

Isolation of Mycoplasmas from nasal swabs of calves affected with respiratory diseases and antimicrobial susceptibility of their isolates

Nasal swabs of 293 calves were examined for Mycoplasma. The samples were collected from calves affected with respiratory diseases on 71 farms in various parts of Japan between 1996 and 1997. Mycoplasma bovirhinis was isolated from 47 of 293 calves (16.0%). Mycoplasma alkalescens, M. bovis, M. arginini, M. bovigenitalium and Acholeplasma spp. were isolated from 19 (6.5%), seven (2.4%), four (1.4%), four (1.4%) and 18 (6.1%) calves, respectively. Pasteurella multocida and P. haemolytica were isolated from 60% of Mycoplasma-positive calves. However, other bacteria were not isolated from calves. To evaluate the antimicrobial susceptibility of their isolates, 68 M. bovirhinis, 21 M. alkalescens and 10 M. bovis strains were examined for 12 antimicrobial agents. All isolates showed higher susceptibility to tiamulin than to the other drugs used in the study. However, erythromycin had no effect on any of the Mycoplasma strains studied. The field isolates were less susceptible than the type strains to some drugs, such as spiramycin, oxytetracycline and tylosin.     

Pneumonia in calves produced with aerosols of Pasteurella multocida alone and in combination with bovine herpesvirus 1.

Pathological changes in respiratory tracts were studied in 30 calves following exposure to aerosols of Pasteurella multocida or to bovine herpesvirus 1 and P. multocida. Two groups of five calves were exposed to aerosols of one of two types of P. multocida only, which produced lobar pneumonia in one calf of each group. Another five groups of four calves were exposed to aerosols of bovine herpesvirus 1 and four to seven days later to one of the two types or one sub-type of P. multocida. Extensive necropurulent lesions were produced throughout the respiratory tract with each type of P. multocida in all four calves in three groups but none in the remaining two groups. The pathological changes differed from those produced following similar exposures to bovine herpesvirus 1 and P. haemolytica, in that the exudate in air passages and alveoli was more purulent and streaming (oat) cells and large mononuclear eosinophilic granulocytes were absent. This is the first report of experimental respiratory disease in cattle as a result of aerosol exposure to P. multocida alone or in combination with bovine herpesvirus 1.     

Bacterial Identity and Characteristics in Healthy and Unhealthy Respiratory Tracts of Sheep and Calves

Barbour, E.K., Nabbut, N.H., Hamadeh, S.K. and Al-Nakhli, H.M., 1997. Bacterial identity and characteristics in healthy and unhealthy respiratory tracts of sheep and calves. Veterinary Research Communications, 21 (6), 421-430The aim of this study was to compare different bacteriological aspects of the respiratory systems of healthy (H) versus unhealthy (UH) animals with respiratory signs. The prevalence of different bacterial species was determined in the upper and lower respiratory tract of H and UH Najdi sheep, Somali sheep and Holstein calves. The characteristics of Pasteurella spp. isolates, and the biotype of Pasteurella haemolytica were identified in H and UH animals. Eighteen out of 28 (64.3%) of the identified bacterial species in the upper respiratory tract were more prevalent in the nasal cavities of UH Najdi and Somali sheep and Holstein calves with respiratory signs than in apparently healthy animals; four of the most prevalent bacteria in the upper respiratory system of UH sheep were Moraxella spp., Pseudomonas pseudomallei, Erysipelothrix spp., and Pasteurella multocida, while three of the most prevalent bacteria in UH calves were Pasturella haemolytica, Actinomyces spp., and Pseudomonas aeruginosa. The prevalence of six different bacterial species was greater in the lungs of UH animals, namely Actinomyces pyogenes, Erysipelothrix spp., P. haemolytica, Pasteurella ureae, Staphylococcus aureus, and Staphylococcus epidermidis, which could be risk factors in the complexity of the prevalent respiratory diseases of the animals surveyed.Of the biochemical, cytological and colonial characteristics studied in the identified P. haemolytica and P. multocida, two characters were significantly different (p < 0.05) in organisms isolated from UH as compared to those from H animals. These were the higher loss of haemolytic power by the strains of P. haemolytica and the decreased fermentation of trehalose by all the strains of P. multocida recovered from healthy animals.The only biotype of P. haemolytica isolated from H animals was biotype A, while both biotypes A (88.0% of the isolates) and T (12.0% of the isolates) were recovered from UH animals.     

The efficacy of valnemulin (Econor) in the control of disease caused by experimental infection of calves with Mycoplasma bovis

Mycoplasma bovis infection was experimentally induced in groups of six young calves. A further group was uninfected and served as a control. Ten days after infection, medication with either enrofloxacin (Baytril, Bayer) or valnemulin (Econor, Novartis) was instituted via the milk replacer for a further 10 days, after which all calves were killed. Infection resulted in depression, pyrexia, inappetance and prominent respiratory signs. Arthritis occurred in two animals and two (unmedicated) animals died. At post-mortem examination extensive lesions were present in the lungs and M. bovis was re-isolated from infected unmedicated calves' lungs. Medication with either enrofloxacin or valnemulin resulted in a rapid diminution of clinical signs, restoration of appetite and reversal of weight loss. Isolation of Pasteurella multocida from the calves' lungs was suppressed by both medicaments. Valnemulin resulted in a more rapid reduction of clinical scores and eliminated M. bovis from the lungs more effectively than enrofloxacin.     

Prevalence of Pasteurella multocida and other respiratory pathogens in the nasal tract of Scottish calves

The prevalence of Pasteurella multocida, a cause of bovine respiratory disease, was studied in a random sample of beef suckler and dairy farms throughout Scotland, by means of a cross-sectional survey. A total of 637 calves from 68 farms from six geographical regions of Scotland were sampled between February and June 2008. Deep nasal swabs were taken, and samples that were culture-positive for P multocida were confirmed by PCR. Prevalence of P multocida was 17 per cent (105 of 616 calves); 47 per cent of farms had at least one positive animal. A higher prevalence was detected in dairy calves than beef calves (P=0.04). It was found that P multocida was associated with Mycoplasma-like organisms (P=0.06) and bovine parainfluenza type 3 virus (BPI-3) (P=0.04), detected by culture and quantitative PCR of nasal swabs, respectively. Detection of P multocida was not associated with bovine respiratory syncytial virus (BRSV), bovine herpesvirus type 1 (BoHV-1) or bovine viral diarrhoea virus (BVDV). Mycoplasma-like organisms, BPI-3, BRSV, BoHV-1 and BVDV were detected in 58, 17, four, 0 and eight calves, on 25, five, two, 0 and five of the 68 farms, respectively.     

Pathological and microbiological studies on pneumonic lungs from Danish calves

During 1 year, the association between microbiological and pathological findings in 72 lungs from calves submitted to the Danish Veterinary Laboratory for diagnostic purposes was studied. All cases were evaluated pathologically and bacteriologically, whereas only 68 cases were examined for the presence of bovine respiratory syncytial virus (BRSV), parainfluenza-3 virus (PI-3 virus) and bovine coronavirus, 62 cases for bovine viral diarrhoea virus (BVD), 45 cases for bovine adenovirus and 51 cases for mycoplasmas. Based on histopathological examination, the cases were diagnosed as fibrinous and/or necrotizing bronchopneumonia, suppurative bronchopneumonia, embolic pneumonia and others. The diagnoses were based on the dominating and most severe lesions in each lung. Haemophilus somnus, Pasteurella multocida, Actinomyces pyogenes, P. haemolytica and BRSV were the most commonly found bacterial and viral lung pathogens, respectively. Pasteurella spp. and H. somnus were often associated with the more severe fibrinonecrotizing type of bronchopneumonia, whereas BRSV was primarily detected in cases of suppurative bronchopneumonia. Mycoplasma bovis was isolated from one case only, whereas M. dispar, M. bovirhinis and Ureaplasma diversum were present, often concomitantly, in the majority of cases. Aspergillus fumigatus was isolated from one case.     

Changes in the bacterial flora of the upper and lower respiratory tracts and bronchoalveolar lavage differential cell counts in feedlot calves treated for respiratory diseases.

Serial nasopharyngeal swab and bronchoalveolar lavage cultures were used to estimate changes in the bacterial flora of the respiratory tracts of calves during the first month after arrival in the feedlot. Bronchoalveolar lavage (BAL) differential cell counts served to evaluate pulmonary inflammatory changes during this period. Two groups of calves were studied, one consisting of clinically normal controls (n = 60), the other, of cases (n = 59) which received treatment for respiratory disease (penicillin +/- trimethoprimsulfadoxine). A variety of organisms, including Pasteurella multocida, Pasteurella haemolytica, Haemophilus somnus, Mycoplasma bovis and Mycoplasma bovirhinis, were present in the upper and lower airways of both groups during the postarrival period. With the exception of M. bovis, an overall decline in the prevalence of these organisms was observed during the course of the study. In cases, there was a marked decrease in the number of Pasteurella spp. and H. somnus isolates immediately following treatment. For the Pasteurella spp., however, this effect was shortlived as they often appeared to recolonize the respiratory tract within eight days of terminating antimicrobial therapy. Treatment did not appear to affect the frequency of isolating M. bovis. Its prevalence, in both groups of calves, increased to levels approaching 100% during the course of the study. All Pasteurella spp. isolates were tested for susceptibility to several commonly used antimicrobials. Resistance was only evident among P. haemolytica isolated from cases and in every instance this was to a combination of penicillin, ampicillin and tetracycline. Significantly more isolates were resistant after treatment than before. There were BAL differential cell count abnormalities indicative of inflammation in both cases and controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Frequency of occurrence of pneumonia associated agents and their correlation with clinical and pathological-anatomical findings in pigs

The aim of this study was to investigate the incidence and influence of different causative organisms involved in the development of pneumonia and bronchopneumonia in pigs. Bronchoalveolar lavage fluid (BALF) from 339 pigs was examined molecular-biologically and culturally. The evaluation considered the following pathogens: Mycoplasma (M.) hyopneumoniae, Mycoplasma (M.) hyorhinis, PRRSV (US-Type), PRRSV (EU-Type), PCV-2, Influenzavirus Type A, alpha-haemolytic Streptococci, beta-haemolytic Streptococci, Pasteurella (P.) multocida, Bordetella (B.) bronchiseptica, Haemophilus (H.) parasuis and Actinobacillus (A.) pleuropneumoniae. This was followed by a pathological-anatomical examination in 168 pigs. Pathological-anatomical examination was evaluated for possible interstitial pneumonia, catarrhal-purulent bronchopneumonia and pleuritis. alpha-haemolytic Streptococci, PCV-2, H. parasuis, M. hyorhinis, M. hyopneumoniae, B. bronchiseptica, PRRSV (US-Type), P. multocida, PRRSV (EU-Type) and Influenzavirus Type A were evident in descending incidence in the BALF. A. pleuropneumoniae were only isolated culturally in two cases in the BALF. The frequency and semiquantitative detection rate in the bacteriological culture of alpha-haemolytic Steptococci, M. hyopneumoniae, P. multocida and B. bronchiseptica correlated significantly with the ascertained clinical evaluation score and the pathological-anatomical examination score. M. hyorhinis and Influenzavirus Type A only correlated with the severity degree of clinical appearance, while PCV-2 and PRRSV (US-Type) correlated with the frequency of pathological-anatomical changes. The higher the clinical score, the higher was the number of animals ascertained with five or more different pathogens. The more different causal agents were isolated in the BALF of one animal, the higher was the average pathological-anatomical examination score. For the diagnosis of pneumonia, especially when analysing facultative pathogens or secondary pathogens, a useful interpretation of analysis results is only possible in connection with a clinical and pathological evaluation.     

不同牛源多杀性巴氏杆菌HasR基因的克隆及序列分析

为了克隆从患肺炎犊牛和健康犊牛上分离的多杀性巴氏杆菌血红素结合受体(heme acquisition system receptor,HasR)基因并进行序列分析,分别以致犊牛肺炎和健康犊牛携带的多杀性巴氏杆菌DNA为模板,通过PCR反应扩增出血红素结合受体基因的全部序列,PCR产物纯化后克隆到pMD19-T载体上,经菌液PCR和酶切鉴定后进行序列测定。各菌株HasR基因序列比对结果发现,Pm-BS-a、Pm142-x-4、Pm142-x-3、Pm149-x、Pm-BS-d的序列之间亲源关系较近,而Pm149-xby与参考菌株Pm70的同源性较高。健康牛源的多杀性巴氏杆菌与致犊牛肺炎多杀性巴氏杆菌之间HasR基因的同源性非常高,说明致犊牛肺炎多杀性巴氏杆菌是一种条件性致病菌,其引起的犊牛肺炎可能属内源性感染。     

牦牛肺炎病原多杀性巴氏杆菌和殊异支原体的分子鉴定与分析

青海省刚察县某牦牛产业基地牦牛发生咳嗽,鼻孔有分泌物流出,呼吸困难等症状的疾病。为快速确诊发病牛的致病原因,及时防控和治疗,从发病和病死的牦牛中,采集鼻腔拭子和肺脏、胸腔积液,利用PCR方法进行分子鉴定与分析。结果显示:此牛场中引发肺炎的病原是A型多杀性巴氏杆菌和殊异支原体两种病原体混合感染,测序结果显示5个有效样品中鉴定的为完全相同的病原,P.multocida-GC1的Kmt基因与参考序列中国株CP031554/3/2/1同源性在99%以上,M.dispar-GC1与参考序列的16S rRNA基因同源性在97%以上。同时在遗传进化角度再次分析确认了鉴定的P.multocida与中国和俄罗斯的A型多杀性巴氏杆菌聚成一大支;鉴定的M.dispar与殊异支原体聚为一支。结果表明,青海刚察地区牦牛存在感染多杀性巴氏杆菌和殊异支原体的潜在风险,该研究为牦牛呼吸道疾病与肺炎的病原学调查和病原的流行病学调查提供了参考数据。     

Isolation of mycoplasma species from the lower respiratory tract of healthy cattle and cattle with respiratory disease in Belgium

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.     

Naturally occurring Mycoplasma bovis-associated pneumonia and polyarthritis in feedlot beef calves.

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.