Mycoplasma bovis pneumonia in cattle

Mycoplasma bovis is an important and emerging cause of respiratory disease and arthritis in feedlot cattle and young dairy and veal calves, and has a variety of other disease manifestations in cattle. M. bovis is certainly capable of causing acute respiratory disease in cattle, yet the attributable fraction has been difficult to estimate. In contrast, M. bovis is more accepted as a cause of chronic bronchopneumonia with caseous and perhaps coagulative necrosis, characterized by persistent infection that seems poorly responsive to many antibiotics. An understanding of the disease has been recently advanced by comparisons of natural and experimentally induced disease, development of molecular diagnostic tools, and understanding some aspects of virulence, yet uncertainties regarding protective immunity, the importance of genotypic diversity, mechanisms of virulence, and the role of co-pathogens have restricted our understanding of pathogenesis and our ability to effectively control the disease. This review critically considers the relationship between M. bovis infection and the various manifestations of the bovine respiratory disease complex, and addresses the pathogenesis, clinical and pathologic sequelae, laboratory diagnosis and control of disease resulting from M. bovis infection in the bovine respiratory tract.     

Pathogenesis of bovine tuberculosis: the role of experimental models of infection

In many countries, test-and-slaughter policies based on tuberculin skin testing have made a significant impact on the control of bovine tuberculosis (caused by infection with Mycobacterium bovis). However, in some countries these policies have not proved as effective and improved disease control strategies are required (including improved diagnostic tests and development of vaccines). The host pathogen interactions in bovine tuberculosis are very complex. While studies of the disease in naturally infected field cases of bovine tuberculosis have provided valuable information, detailed knowledge can also be gained through studies of disease models. A number of studies have developed M. bovis infection models employing a range of routes and challenge doses. An early objective was assessment of vaccine efficiency, and models of infection remain central to current work in this area. Development of the intra-nasal and intra-tracheal models have also advanced our understanding of the kinetics of the immune response. In many of these studies, understanding of pathogenesis has been improved by definition of the cells that respond to infection and those that are instrumental in modulation of host responses. Experimental models of infection have been adapted to study cattle to cattle transmission, modeling one of the fundamental routes of infection. This review provides a historical perspective on the types of experimental models used in over 100 years of research and outlines new opportunities to refine those methods for bovine and human tuberculosis and to contribute to improved diagnostics, advanced understanding of immunology and vaccine design.     

Mycobacterium bovis infection and tuberculosis in cattle

This review considers the possible events that can occur when cattle are exposed to Mycobacterium bovis and, where appropriate, draws on principles accepted for tuberculosis infection in humans and laboratory animal models. Consideration is given to the many complex factors which influence the outcome of challenge with tubercle bacilli. These include features inherent to the mycobacterium, the host and the environment. It is apparent that clinical disease probably occurs only in a relatively small, but undetermined, proportion of cattle that are exposed to Al. bovis. The majority of animals may clear infection or control the bacilli, possibly in a condition of latency. It is concluded that a better understanding of the dynamics of the events following M. bovis exposure and subsequent infection in cattle would be of significant benefit in developing new tools appropriate for disease control and to designing optimal approaches for their application.     

An update on bovine tuberculosis programmes in Latin American and Caribbean countries

Of the approximately 374 million cattle in Latin America and the Caribbean, 70% are held in areas where rates of Mycobacterium bovis infection in cattle are higher than 1%. The remaining 30% are in countries where infection affects less than 1% of cattle, including 62 million in countries where bovine tuberculosis infection is virtually nil. Measures for controlling bovine tuberculosis are partially or extensively applied in most of the countries in the Region. These measures are based on test and slaughter, notification, post-mortem inspection and surveillance in slaughterhouses. A coordinated production, standardization and quality control of purified protein derivatives is urgently required for use in control and eradication campaigns in order to assure reliability of reagents and comparability of data on tuberculin testing within the Region. On the basis of information from Argentina, M. bovis is estimated to cause 2% of all human cases of tuberculosis in the Region. Slaughterhouse and dairy farms workers are most-frequently infected, with infection occurring via the respiratory tract. Various in vitro assays for the diagnosis of bovine tuberculosis have been developed and/or assessed in the Region, and DNA fingerprinting has been applied for a comprehensive understanding of the epidemiology of bovine tuberculosis at the local and regional level.     

Advances in bovine tuberculosis diagnosis and pathogenesis: what policy makers need to know

The mainstay of tuberculosis diagnosis in cattle and deer has been the tuberculin skin test. Recent advances have allowed the incorporation of blood based assays to the diagnostic arsenal for both cattle and deer. Use of defined and specific antigens has allowed for improved specificity of cell mediated assays in both cattle and deer and advances in antibody tests for tuberculosis have potential for use in free-ranging and captive cervid populations. Combined use of blood-based assays with skin testing will require further understanding of the effect of skin testing on the accuracy of blood based assays. Models of experimental infection of cattle have allowed for increased understanding of natural disease pathogenesis. Differences likely exist; however, between cattle and deer in both disease distribution and primary route of inoculation in naturally infected animals.     

Prevalence of bovine tuberculosis in slaughter cattle in Kenya: a postmortem, microbiological and DNA molecular study

A study to determine the presence and prevalence of bovine tuberculosis in slaughter cattle in Kenya was carried out in two abattoirs from July to November 2009. Routine postmortem meat inspection was performed on a subpopulation of 929 cattle selected randomly from among 4,984. Carcases were inspected for gross tuberculous lesions which were then examined for acid-fast bacilli, (AFB), cultured for isolation of mycobacteria and the isolates characterised by DNA molecular analysis. Of the carcases examined, 176 (18.95?%, 95?% CI) had lesions suggestive of tuberculosis. AFB were observed in 63/176 of the lesioned cattle and mycobacteria were isolated from 64 of them. The isolates were identified as Mycobacterium bovis (19/64), Mycobacterium tuberculosis, (2/64) and mycobacteria other than tuberculosis (43/64). The prevalence of M. bovis by molecular analysis was 2.05?% (95?% CI). This study documents for the first time the presence of bovine tuberculosis among slaughter cattle in Kenya. There is therefore a need to formulate and implement control programmes in order to minimise transmission among animals and to humans. Isolation of M. tuberculosis from cattle underscores the risk tuberculous humans pose to animals.     

Pulmonary lesions and Mycobacterium bovis excretion from the respiratory tract of tuberculin reacting cattle

Although it is generally recognised that tuberculous lesions are present in lymph nodes associated with the respiratory tract in approximately 90 per cent of reactors with confirmed infection, lung lesions are found in only 1 to 2 per cent of such cases during abattoir examination. When lung lesions are not detected, it has been claimed that such cattle are non-excretors and thus unimportant in the epidemiology of the disease. In this study the lungs of 55 reactor cattle were sliced into sections approximately 0.5 cm thick. Tuberculous lesions were evident in over 70 per cent of lungs from reactors with concurrent lesions in lymph nodes of the respiratory system. Further, M bovis was isolated from single samples of nasal and, or, tracheal mucus taken at slaughter in 19 per cent of confirmed cases. Several of these reactors had a clear tuberculin test less than six months previously indicating recent infection. This study confirms the continued importance of the infected bovine in the epidemiology and current eradication of bovine tuberculosis. It is suggested that all tuberculous cattle with lesions in respiratory lymph nodes, rather than being regarded as non-excretors, should be considered as possible excretors and thus important sources of infection for other cattle both within and between herds.     

The influence of cattle breed on susceptibility to bovine tuberculosis in Ethiopia

Bovine tuberculosis in domestic livestock such as cattle is an economically important disease with zoonotic potential, particularly in countries with emerging economies. We discuss the findings of recent epidemiological and immunological studies conducted in Ethiopia on host susceptibility differences between native zebu and the exotic Holstein-Friesian cattle that are increasingly part of the Ethiopian National herd, due to the drive to increase milk yields. These findings support the hypothesis that native Zebu cattle are more resistant to bovine tuberculosis. We also summarise the results of experimental infections that support the epidemiological data, and of laboratory experiments that suggest a role for the innate immune response, and in particular interleukin-6, in the outcome of bovine tuberculosis infection.     

Survival rate of airborne Mycobacterium bovis

Despite years of study the principle transmission route of bovine tuberculosis to cattle remains unresolved. The distribution of pathological lesions, which are concentrated in the respiratory system, and the very low dose of Mycobacterium bovis needed to initiate infection from a respiratory tract challenge suggest that the disease is spread by airborne transmission. Critical to the airborne transmission of a pathogenic microorganism is its ability to survive the stresses incurred whilst airborne. This study demonstrates that M. bovis is resistant to the stresses imposed immediately after becoming airborne, 94% surviving the first 10 min after aerosolisation. Once airborne the organism is robust, its viability decreasing with a half-life of approximately 1.5 hours. These findings support the hypothesis that airborne transmission is the principle route of infection for bovine tuberculosis.     

Cattle-to-cattle transmission of bovine tuberculosis

In developed countries, Mycobacterium bovis infection in cattle is now mostly confined to the respiratory system, which reflects transmission and establishment of infection mainly by this route. A single bacillus transported within a droplet nucleus is probably sufficient to establish infection within the bovine lung. Infected cattle should always be considered as potential sources of infection, since studies have demonstrated that a significant proportion of tuberculous cattle excrete M. bovis.In general, the dynamics of M. bovis transmission are poorly understood and the conditions under which a tuberculous animal becomes an effective disseminator of infection are currently not defined although environmental contamination appears to be a less effective method of disease transmission. Field studies indicate a wide spectrum of transmission rates but generally the spread of M. bovis infection is still considered to be a relatively slow process. Slaughter of diseased cattle detected by tuberculin testing and at meat plant inspection has been shown to be an effective policy for tuberculosis eradication, provided there are no other reservoirs of infection and all involved in the cattle industry are committed to a policy of eradication. Epidemiological approaches, particularly case-control studies, seem to provide the best method for quantifying the relative importance of the various sources of M. bovis transmission to cattle and modelling techniques can be used to assist in the design of cost-effective control measures that may lead to tuberculosis eradication.     

Association between infection of the respiratory tract attributable to bovine coronavirus and health and growth performance of cattle in feedlots

OBJECTIVE: To determine the association between respiratory tract infection with bovine coronavirus (BCV), treatment for respiratory tract disease, pulmonary lesions at slaughter, and average daily gain in cattle in feedlots. ANIMALS: 837 calves in feedlots in Ohio and Texas. PROCEDURE: Nasal swab specimens were obtained from cattle at arrival in a feedlot (day 0) and at various times during the initial 28 days after arrival. Specimens were tested for BCV, using an antigen-capture ELISA. Serum samples were obtained at arrival and again 28 days after arrival and tested for antibodies to BCV, using an antibody-detection ELISA. Information was collected regarding treatment for cattle with respiratory tract disease and average daily gain during the feeding period. Pulmonary lesions were evaluated at slaughter. RESULTS: Cattle shedding BCV from the nasal cavity and developing an antibody response against BCV were 1.6 times more likely to require treatment for respiratory tract disease than cattle that did not shed the virus or develop an immune response against BCV. Additionally, cattle that shed BCV from the nasal cavity were 2.2 times more likely to have pulmonary lesions at slaughter than cattle that did not shed the virus. The BCV shedding or seroconversion status did not affect average daily gain. CONCLUSIONS AND CLINICAL RELEVANCE: Bovine coronavirus infects feedlot cattle and is associated with an increased risk for cattle developing respiratory tract disease and pulmonary lesions. Development of appropriate control measures could help reduce the incidence of respiratory tract disease.     

Quantification of the relative efficiency of factory surveillance in the disclosure of tuberculosis lesions in attested Irish cattle

In Ireland, factory surveillance of cattle for gross lesions is an important supplementary method for detecting herds infected with bovine tuberculosis (tb), and in recent years between 27 and 46 per cent of all new herd breakdowns in any year have been detected by this method. The aim of this study was to determine the relative efficiency of factories in detecting lesions among attested cattle slaughtered during 2003 and 2004. National databases were available on animal slaughter, programmes of tuberculin testing for bovine tb and laboratory confirmation of suspected lesions. Factories were ranked according to their submission risk (number of animals submitted with lesions/number of attested animals killed) and confirmation risk (number of animals with laboratory-confirmed lesions/number of animals submitted with lesions), adjusting for the risk profile of the animals slaughtered, including potential confounding factors such as their age and sex, whether they were purchased or homebred, the test history of their herd, the prevalence of bovine tb in the area and the season of slaughter. Approximately 3.7 million cattle were slaughtered in 42 Irish export-licensed factories during the two years. Complete data were available for 2,374,987 animals from 84,510 attested herds in 2845 District Electoral Divisions. Samples from 7398 animals with suspected tb lesions were submitted for laboratory examination; 4767 (64.4 per cent) were positive, 2011 were negative and 620 were inconclusive. The average unadjusted submission risk for all the factories was 22 per 10,000, ranging from 0 to 58 per 10,000. The unadjusted factory confirmation risk (excluding factories that had sent in fewer than 10 lesions) varied between 34.3 per cent and 86.3 per cent. The unadjusted and adjusted submission and confirmation risks were highly correlated, and animal-related factors (including their characteristics and origin) therefore did not contribute to the variations in factory-level submission and confirmation risks.     

The epizootiological significance of positive bacteriological findings on Mycobacterium tuberculosis and Mycobacterium bovis in humans

The relation between the active form of tuberculosis in persons working in agriculture and incidence of tuberculosis in cattle was analyzed in 1974 to 1978, i.e. in the period after the elimination of bovine tuberculosis in Czechoslovakia (in 1968). M. tuberculosis was isolated in 15 cases and M. bovis in four cases of persons employed by the farms on which the Regional Hygienic Station, Brno, was responsible for the microbiological diagnostics of tuberculosis. Direct contact with animals was demonstrated in eight patients; M. tuberculosis was isolated from seven of these patients and M. bovis from one. Seven cattle herds were exposed to spontaneous infection by M. tuberculosis and in one of them tuberculosis was not demonstrated during complex examination. In three herds the examination revealed only a sensitivity of cattle to mammalian tuberculin. In other three herds tuberculosis was detected by allergic tests, patho-anatomic examination and bacteriological examination. M. tuberculosis in cattle was detected in two herds. The occurrence of bovine tuberculosis caused by a cattle tender with a positive finding of M. bovis in sputum was demonstrated in one herd. Virulence for the tested cattle was found in one strain (isolated from a mesenterial lymph node of cattle) of the four strains of M. tuberculosis used for the experimental infection of 17 animals. On the other hand, in three strains of M. tuberculosis, trials with experimental infection demonstrated only allergy to mammalian tuberculin and changes at the sites of subcutaneous inoculation of mycobacteria of regressive nature; these mostly disappeared within 90 days from infection.     

The experience of new European Union Member States concerning the control of bovine tuberculosis

On 1 May 2004, 10 new States joined the European Union, including Cyprus (CY), the Czech Republic (CR), Estonia (ES), Hungary (HU), Latvia (LA), Lithuania (LI), Malta (MA), Poland (PO), Slovakia (SK), and Slovenia (SN). Using OIE and published data, this paper summarises the status of bovine and human tuberculosis in animals in these countries between 1996 and 2003. National control programmes against bovine tuberculosis in cattle have been successful: the current herd incidence of this disease in cattle is currently lower than 0.2%, so all countries meet the OIE requirements for freedom from the disease. Furthermore, two countries have already been officially declared bovine tuberculosis-free EU States: the CR on 31 March 2004 (European Commission Decision No. 2004/320/EC) and SK on 4 March 2005 (Commission Decision No. 2005/179/EC). The last outbreak of bovine tuberculosis was diagnosed in cattle in CY (1928), ES (1986), LA (1989), SK (1993), CR (1995), and MA (2001). However, several issues of concern remain including the potential existence of a wildlife reservoir, the presence of Mycobacterium bovis, M. caprae, and other members of the M. tuberculosis complex (particularly M. tuberculosis or M. microti) in imported domestic or wild animals, and the potential for delayed detection of bovine tuberculosis in those States where annual tuberculin testing is no longer performed on cattle older than 24 months.     

Mycobacterium bovis in the anterior respiratory tracts in the heads of tuberculin-reacting cattle

Twenty-five of 50 randomly selected tuberculin-reacting cattle were confirmed as tuberculous in the laboratory. All 25 cattle had macroscopic lesions in lymph nodes associated with the respiratory tracts but only one had lung lesions. M bovis was isolated from the anterior respiratory tracts in the heads of four of the 25 tuberculous animals and from a nostril lesion found in a fifth. For at least three of these five animals, the intervals between the final tuberculin test and their previously negative tests indicated that infection had established relatively rapidly. Four of them had been tuberculin tested solely because they were animals in contiguous 'at risk' herds. It would appear that although M bovis can be isolated from the anterior respiratory tracts in the heads of tuberculin-reacting cattle, it is unlikely that primary foci of infection exist in regions other than the lungs or associated tissues. The study demonstrates the potential for reactors with lesions to excrete M bovis and the continued importance of infected cattle in the epidemiology and eradication of the disease.     

The prevalence of bovine tuberculosis (Mycobacterium bovis) infections in feral populations of cats (Felis catus), ferrets (Mustela furo) and stoats (Mustela erminea) in Otago and Southland, New Zealand

Twenty-one properties in the Otago region of the South Island of New Zealand were surveyed for the presence of gross lesions due to Mycobacterium bovis infection in feral cats (Felis catus), ferrets (Mustela furo) and stoats (Mustela erminea) during 1993 and 1994. In total, 1293 cats, ferrets, stoats and weasels (Mustela nivalis) were examined for the presence of tuberculous lesions. The properties surveyed were selected according to the history and incidence of bovine tuberculosis infection in their cattle herds. Sixteen infected cattle properties were trapped in areas of Otago that were endemic for bovine tuberculosis and five properties were trapped in non-endemic areas that were considered to be free from tuberculosis infection in the cattle. No tuberculous cats, ferrets, stoats or weasels were found in non-endemic areas, and prevalence rates in the endemic areas were 0.9% for cats (n=215, 0.12相似文献   

Further evaluation of an indirect enzyme-linked immunosorbent assay for the diagnosis of bovine tuberculosis

The sensitivity and specificity of an ELISA for the detection of bovine IgG anti-Mycobacterium bovis antibodies were 73.6% and 94.1%, respectively, as determined in 53 bacteriologically confirmed tuberculous cattle and 101 healthy cattle from a tuberculosis-free area. In addition, the results of ELISA and tuberculin tests in 149 cattle were compared with those of subsequent necropsy studies. Both tests failed to detect 2 animals with tuberculous lesions and positive culture; 3/12 cattle with M. bovis isolation and no lesions, and 2/7 with atypical mycobacterial infection reacted to tuberculin, but none had antibodies; in 128 cattle with neither lesions nor mycobacterial isolation, 6 were tuberculin reactors and 7 others had antibodies. Negative results were obtained by ELISA in 21/22 paratuberculous cattle. Antibodies were not detected in 88.9% to 96.4% of 697 cattle from two tuberculin negative herds of an endemic area. In a herd with proved M. bovis infection, distribution of seropositive animals in tuberculin and non-tuberculin reactors was similar. Antibody responses to cutaneous tuberculin stimuli were observed in 4 experimentally infected cattle, but only in 2/10 healthy controls after repeated PPD stimuli. Nine controls which had either received a single tuberculin dose or none showed no increase in antibody levels. The low sensitivity of this ELISA limits its usefulness as a diagnostic tool for bovine tuberculosis eradication campaigns. However, it could be helpful in epidemiological surveillance if its efficiency to identify infected herds is demonstrated.     

Microbiologic findings in feedlot cattle with acute interstitial pneumonia

OBJECTIVE: To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP ANIMALS: 39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens. PROCEDURES: Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically. RESULTS: Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem.     

Progress in the development of tuberculosis vaccines for cattle and wildlife

Vaccination against bovine tuberculosis is likely to become an important disease control strategy in developing countries, which cannot afford a test and slaughter control programme, or in countries which have a wildlife reservoir of Mycobacterium bovis infection. In the past decade, considerable progress has been made in the development and evaluation of tuberculosis vaccines for cattle and for a range of wildlife maintenance hosts including possums, badgers, deer and African buffaloes. Experimental challenge systems have been established for the different target species and the resulting disease process has mimicked that seen in the field. In cattle, neonatal vaccination with BCG appeared to be more effective than vaccination of 6-month-old calves and in most situations no other vaccine has been shown to be better than BCG. However, prime-boost strategies involving combinations of BCG with a protein or DNA vaccine, to improve on BCG vaccination alone, have produced very encouraging results. Differential diagnostic tests have been developed using mycobacterial antigens that are only present in virulent M. bovis to differentiate between BCG-vaccinated and M. bovis-infected cattle. BCG vaccine has been shown to reduce the spread of tuberculous lesions in a range of wildlife species and a prototype oral bait delivery system has been developed. Prospects for the development of improved vaccines against bovine tuberculosis are promising and vaccination approaches could become very valuable in the control and eradication of bovine tuberculosis.     

Crohn's disease and Mycobacterium avium subsp. paratuberculosis: the need for a study is long overdue

The initial suggestion that Mycobacterium avium subsp. paratuberculosis (Map) might be involved in the pathogenesis of Crohn's disease (CD) was based on the apparent similarity of lesions in the intestine of patients with CD with those present in cattle infected with Map, the etiological agent of Johne's disease (JD). Recent investigations have now revealed the presence of Map or Map DNA in blood or lesions from adults and children with CD. Of special interest, Map has also been found in patients with other diseases as well as healthy subjects. The latter observations indicate all humans are susceptible to infection with Map and that, like with other mycobacterial pathogens such as Mycobacterium tuberculosis, infection does not invariably lead to development of clinical disease but rather development of a persistent latent stage of infection where an immune response controls but does not eliminate the pathogen. Limited information has been obtained on the immune response to Map in healthy subjects and patients with CD. Understanding how Map may be involved in the pathogenesis of CD will require a better understanding of the immune response to Map in one of its common hosts as well as healthy humans and patients with CD.