Prevalence of respiratory pathogens in diseased, non-vaccinated, routinely medicated veal calves

The prevalence of respiratory pathogens in diseased veal calves was determined in 24 respiratory disease outbreaks in 15 herds in Belgium. Bacteria were cultured from nasopharyngeal swabs and seroconversion against viruses and Mycoplasma bovis was determined on paired sera. At the individual calf level, Mycoplasma species, Mannheimia haemolytica and Pasteurella multocida, were isolated from 70.5 per cent, 21.5 per cent and 26.0 per cent of swabs, respectively. At the herd level, the presence of M bovis could be confirmed in 84.6 per cent of the herds examined. Seroconversion against bovine viral diarrhoea virus (BVDV) was present in 71.4 per cent of herds, parainfluenzavirus type 3 in 53.3 per cent, bovine respiratory syncytial virus in 40.0 per cent, bovine adenovirus type 3 in 46.7 per cent, bovine coronavirus in 30.0 per cent, and bovine herpesvirus type 1 in 26.7 per cent. At postmortem examination, Mycoplasma species could be cultured from 61.9 per cent of pneumonic lungs (n=21). Sixty per cent of calves tested were positive for BVDV (n=20), and 20.0 per cent were positive for bovine respiratory syncytial virus (n=16).     

Serological survey to determine the occurrence of respiratory Mycoplasma infections in the Polish cattle population

Mycoplasma bovis and Mycoplasma mycoides subspecies mycoides small colony (MmmSC) are causes of bovine mycoplasmosis and contagious bovine pleuropneumonia (CBPP), respectively, and are responsible for serious economic losses in cattle around the world. CBPP was last reported in Poland in 1939 but bovine mycoplasmosis is believed to be endemic. A survey of 3670 serum samples for antibodies to M bovis and MmmSC from 361 herds in 16 Polish provinces Poland between 2007 and 2010 found no evidence of CBPP. The seroprevalence of M bovis, however, appeared high with 76.7 per cent of samples giving a positive reaction in the ELISA test, which did not appear to reflect the clinical disease status of the cattle. Adjusting the sensitivity of the test reduced the prevalence to 28.2 per cent and reflects the levels reported in other European countries.     

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.     

Isolation of Mycoplasma bovis from bovine clinical mastitis cases in Northern Greece

Mycoplasma bovis was detected in 18/219 (8.2%) quarter milk samples collected from cases of bovine clinical mastitis in Northern Greece between November 1997 and March 1999. The cases occurred in 2/37 (5.4%) of the herds examined. The micro-organism was isolated from bulk milk samples (BTS) from the two positive herds but was not isolated from 111 composite milk samples collected from clinically healthy cows from all 37 herds. Isolates were identified as M. bovis by polymerase chain reaction (PCR) assay. Other micro-organisms were also isolated from the M. bovis positive samples. The M. bovis-positive cows had all been imported into Greece from other European countries.     

Effect of skin testing and segregation on the prevalence of bovine tuberculosis, and molecular typing of Mycobacterium bovis, in Ethiopia

In 2002, the prevalence of bovine tuberculosis (tb) among 500 cattle on Holeta Farm, near Addis Ababa, Ethiopia, was 48 per cent, and the farm was divided into positive and negative herds. After three consecutive rounds of skin testing and segregation of skin test-positive and -negative animals, the prevalence of bovine tb was reduced from 14 per cent to 1 per cent in the negative herd in a year. Spoligotyping of 41 isolates from 17 cows gave an identical and unique spoligotype pattern, which can be represented as the binary number 1100000101111110111111100010000000000100000, where 1 indicates the presence of a spacer and 0 represents a loss. This spoligotype pattern had not previously been reported on the Mycobacterium bovis spoligotype database, and it was therefore designated SB1176, Ethiopian M bovis strain 1 (EMbs1). The variable number tandem repeat (VNTR) profile of the strain was 5254(*)33.1, which differed from the VNTR profile of strains reported in Great Britain.     

Increased prevalence of Mycoplasma bovis in the Netherlands.

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.     

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.     

An evaluation of the gamma interferon test for detecting bovine tuberculosis in cattle 8 to 28 days after tuberculin skin testing

The gamma interferon (IFN -gamma) test was evaluated for its ability to diagnose bovine tuberculosis in cattle that 8 to 28 days previously had a positive caudal fold skin test. The sensitivity of the test was determined in a group of 163 Mycobacterium bovis -infected cattle from 21 herds. The specificity was estimated in a group of 213 cattle which had reacted to a caudal fold test, but were from 82 herds that had no evidence of infection with M bovis. The sensitivity and specificity of the IFN -gamma test was 85 and 93 per cent respectively. No significant differences in the sensitivity and specificity of the test were observed between blood samples that were cultured on the day of collection and those cultured the day after collection. These findings support the use of the IFN -gamma test as a practical serial test that can be used to complement the caudal fold skin test.     

Within herd comparison of teat dipping and dry cow therapy with only selective dry cow therapy in six herds

A within herd comparison of teat dipping and dry cow therapy (full treatment) with only selective dry cow therapy (partial treatment) was carried out in six commercial dairy herds for a two year period. In four herds, the incidence of clinical mastitis was 2 to 12 per cent higher in the partial treatment group. In another herd, in which the pattern of clinical mastitis isolates was unusual in that minor pathogens were isolated from 30 per cent of mastitis cases, the incidence was 43 per cent higher in the partial treatment group. In the remaining herd the incidence was 10 percent higher in the full treatment group. Streptococcus uberis mastitis was more common in the partial treatment groups of five herds; coliform mastitis was more common in the full treatment groups of two herds and similar in both groups in the other herds. High rates of coliform mastitis were associated with poor herd environmental conditions but this was not true for Strep uberis mastitis. Rates of staphylococcus aureus and Strep dysgalactiae mastitis were low in all herds. The level of major pathogen infection in cows completing the trial in all herds increased in the partial treatment group from 5 per cent of quarters at the start to 12 per cent at the finish of the trial. In the full treatment group, however, there was only a small increase in this level. In contrast, levels of Corynebacterium bovis infection increased by 17 per cent in both treatment groups. Continued use of teat dipping and dry cow therapy was associated with a higher rate of coliform mastitis in two of the three herds where there were poor standards of hygiene and husbandry.     

Costs to farmers of a tuberculosis breakdown

An on-farm survey of 151 cattle farmers who had experienced a bovine tuberculosis (Mycobacterium bovis) breakdown on their farms was undertaken in 2003 to assess the costs associated with the breakdown. In 90 per cent of cases the cost was estimated to be less than 18,513 pounds sterling for dairy herds and less than 11,462 pounds sterling for beef herds, but with a range from 229 pounds sterling to 103,817 pounds sterling. The main cost was the slaughter of reactor cattle. For the majority of the farmers, the compensation payments seemed to meet most of the costs of their breakdowns, although a majority was still left with net losses.     

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.     

Blood culture and stimulation conditions for the diagnosis of tuberculosis in cervids by the Cervigam assay

Mitogen- and antigen-induced interferon-gamma (IFN-gamma) responses of peripheral blood leucocytes from cervids were evaluated by a commercial whole-blood assay. The assay was applied to Mycobacterium bovis-infected white-tailed deer and reindeer, M bovis BCG-vaccinated white-tailed deer and elk, and unvaccinated, uninfected white-tailed deer, fallow deer, elk and reindeer. The responses of the M bovis-infected white-tailed deer to pokeweed mitogen (PWM) varied with time and between individuals. The responses of the M bovis-infected reindeer to PWM and M bovis purified protein derivative (PPD) were positively associated. Samples from tuberculosis-free captive herds in various parts of the USA were also evaluated. Four per cent of fallow deer, 20 per cent of elk, 44 per cent of white-tailed deer, and 91 per cent of reindeer had responses to PWM exceeding 0.25 Delta optical density, that is, PWM stimulation minus no stimulation. The specificity of the responses to M bovis PPD and a Mycobacterium tuberculosis complex-specific antigen rESAT-6:CFP-10, excluding animals not responding to PWM, ranged from 78 per cent to 100 per cent and was dependent upon the species and the positive response cut-off value. The results show that the commercial assay is valid for the detection of TB in reindeer; however, further development of the assay will be required before it is used in surveillance programmes for white-tailed deer, fallow deer, and elk.     

Geographical association between the genotype of bovine tuberculosis in found dead badgers and in cattle herds

In a survey, 457 badgers that had been found dead in Wales were postmortem-examined, and samples were examined by histology and by extended culture (for up to 12 weeks). Mycobacterium bovis was cultured from 55 badgers (12.0 per cent), and the histology typical of M bovis infection was seen in a further six (1.3 per cent). The prevalence in badgers in each of 10 geographical areas varied between 0 and 26 per cent (P<0.001), and was associated with the incidence of confirmed M bovis infection in cattle herds in the same areas (P<0.01). In northern Wales, bTB was rare in both hosts. An infected badger was 12.3 times more likely to be within 5 km of a confirmed cattle bTB breakdown than an uninfected badger. The M bovis isolates from badgers belonged to one of four genotypes defined by spoligotype and variable number tandem repeat type. These genotypes were also found in 290 concurrent confirmed herd breakdowns, and tended to be similar to the genotypes in badgers in the same geographical areas. When badgers and cattle no more than 30 km apart were compared, the genotype diversity was greater in cattle than in badgers (P=0.016), suggesting that the movement of cattle plays a greater part in the spatial distribution of M bovis than the movement of badgers.     

Associations between the prevalence of Mollicutes and Mycoplasma bovis and health and performance in stocker calves

A longitudinal cross-sectional time-series study was carried out to determine the prevalence of nasal mycoplasma carriage, serostatus and seroconversion, and to evaluate the associations between these parameters and health and performance in weaned beef calves during a 42-day feeding period. Nasal swabs and serum were collected on days 0 (arrival), 10, 42 and at the first incidence of bovine respiratory disease complex. The samples were evaluated for Mollicutes (by culture), Mycoplasma bovis (by PCR) and serum antibody to M. bovis. On day 0, 90.4 per cent of the calves were Mollicutes nasal culture-positive. The seroprevalence of M. bovis was 26.6 per cent on day 0 and 98.2 per cent by day 42 (P<0.05). Seroconversion to M. bovis between days 0 and 42 was significantly associated (P=0.04) with lower weight gain. Weight gain was greater in calves that were PCR-negative for M. bovis on day 10 (P=0.01). The percentage of calves seropositive to M. bovis increased throughout the study, indicating exposure and an immunological response to the organism. Although associations with health outcomes were not identified, seroconversion to M. bovis was associated with a decreased rate of weight gain during the study period.     

A field study of Mycoplasma bovis infection in cattle

After an outbreak of mastitis in cattle caused by Mycoplasma bovis a study was made in 5 herds with recent cases (principal herds) and in 4 control herds. In the principal herds, M. bovis was isolated from milk samples, nasal swabs, and from one vaginal swab. M. bovis was also isolated from nasal swabs of calves in 2 of the 4 control herds, whereas all milk samples and vaginal swabs from the control herds were negative. Evaluation of serum antibody titres to M. bovis among non-mastitic animals of 3 principal herds and 1 control herd showed no difference in distribution of the titre values, which generally were low. However, cows excreting M. bovis in the milk had high antibody titres. The way of introduction to the herds and the spread of the infection within the herds could not be established by the study, which was supplemented by a DNA restriction fragment analysis of a number of M. bovis isolates.     

Risk of bovine tuberculosis for cattle sold out from herds during 2005 in Ireland

A retrospective cohort study was conducted to determine the risk of bovine tuberculosis (TB) among animals sold out from herds that were free to trade animals during the year 2005 according to their bovine TB testing history during the year 2005. The present study sample comprised of 338,960 animals, of which 124,360 animals were sold out from herds that were restricted from trading at some stage during 2005 (bovine TB 'exposed') and 214,600 animals that were sold from herds which did not have their trading status withdrawn in 2005 (bovine TB 'non-exposed'). The overall risk of a diagnosis of bovine TB during the two-year period after the animals were sold out was 0.69 per cent. The odds of bovine TB were 1.91 higher for animals sold out from bovine TB 'exposed' herds compared with animals sold out from bovine TB 'non-exposed' herds (OR 95 per cent CI: 1.76 to 2.07, P<0.0001). Ten per cent of animals identified during field surveillance with bovine TB did so less than two months after being sold out in 2005, and similarly, 10 per cent of the animals classified as bovine TB positive by finding a bovine TB lesion at slaughter did so within 25 days (or less) of being sold out in 2005.     

Fluorescence polarization assay for the detection of antibodies to Mycobacterium bovis in bovine sera

The performance of a fluorescence polarization assay (FPA) that detects antibodies to Mycobacterium bovis in bovine sera is described. The FPA reported here is a direct binding primary screening assay using a small polypeptide derived from the M. bovis MPB70 protein. A secondary inhibition assay confirms suspect or presumed positive samples. Specificity studies involved five different veterinary laboratories testing 4461 presumed negative bovine samples. FPA specificity was 99.9%. The FPA was used to identify herd status as either M. bovis infected or non-infected. Herd surveillance studies (nine herds) were performed in Mexico and South Africa. The FPA had a specificity of 100% (two negative herds), and correctly identified six of seven infected herds. Finally, sera from 105 slaughter animals that had gross lesions in lymph nodes similar to those seen with bovine tuberculosis were tested by the FPA. Thin sections from the associated formalin-fixed paraffin-embedded samples of lymph nodes were stained using hematoxylin and eosin (H&E) for morphologic examination and using the Ziehl-Neelsen (ZN) method for detection of acid-fast bacilli. Of the 105 animals, 78 were classified as TB suspect based on lesion morphology, 21 were positive by ZN, 9 were positive by FPA and 13 were positive by PCR for the tuberculosis group of Mycobacterium. Among the 21 ZN positives, 11 (52.4%) were PCR positive. Among the 9 FPA positives, 8 (88.9%) were PCR positive. For the 13 PCR positives, 8 (61.5%) were FPA positive and 11 (84.6%) were ZN positives. These results show that use of the FPA for detection of M. bovis infection of cattle has value for bovine disease surveillance programs.     

Assessment of diagnostic tools for eradication of bovine tuberculosis in cattle co-infected with Mycobacterium bovis and M. avium subsp. paratuberculosis

The intradermal tuberculin (IDTB) test and the interferon-gamma (IFN-gamma) assay are used worldwide for detection of bovine tuberculosis in cattle, but little is known about the effect of co-infecting agents on the performance of these diagnostic tests. This report describes a field trial conducted in a cattle herd with dual infection (bovine tuberculosis and paratuberculosis) during 3.5 years. It has been based on a strategic approach encompassing serial parallel testing (comparative IDTB test, the IFN-gamma assay and serology of paratuberculosis) that was repeated 8 times over the period, and segregation of animals into two herds. The IDTB test detected 65.2% and the IFN-gamma test detected 69.6% of the Mycobacterium bovis culture-positive cattle. However, the IDTB test performed better during the first part of the trial, while the IFN-gamma test was the only method that detected infected animals during the following three samplings. The number of false positive reactors with the IDTB and/or the IFN-gamma tests was remarkably high compared to other reports, and could be caused by cross-reactivity with M. avium subsp. paratuberculosis. Also, the M. bovis isolates from cattle and wildlife from the same property were characterised using molecular techniques to disclose an epidemiological link. The IDTB test may not be appropriate to eradicate bovine tuberculosis in herds with dual mycobacterial infections. This report highlights the need to use several diagnostic techniques for the accurate detection of M. bovis infected animals in these herds.     

Mycoplasma agalactiae subsp. bovis in pneumonia and arthritis of the bovine.

The pneumonic lungs of 42 cattle from 26 feedlots were examined for the presence of mycoplasma, pathogenic bacteria and viruses. Four animals representative of two lots failed to yield mycoplasma. One of these yielded the virus of infectious bovine rhinotracheitis and Pasteurella hemolytica, the other yielded only P. P. multocida. Nine animals in eight lots yielded Mycoplasma sp.: five of these were M. bovirhinis, two were M. arginini and two were untypable. All of these animals yielded one or more of P. hemolytica, P. multiocida, infectious bovine rhinotracheitis virus or bovine virus diarrhea virus. Twenty-five of 29 animals in 16 lots yieled M. agalactiae subsp. bovis from lung tissues. The same organism was recovered from the arthritic joints of 12 of these animals. Eight of the 25 animals yielded no other pathogen and all of these had not received any treatment. Nine of the 25 M. agalactiae subsp. bovis positive animals also yielded one or more of P. hemolytica, P. multocida, Corynebacterium pyogenes or infectious bovine rhinotracheitis virus. Bacteriological and virological studies were not completed for the remaining eight of the 25 positive animals. In five lots of cattle which had not received medication for pneumonia and for arthritis only M. agalactiae subsp. bovis was recovered. Twenty-five grossly normal lungs obtained from normal cattle at the time of slaughter were cultured and all were negative. The possible role of M. agalactiae subsp. bovis in pneumonia and arthritis was discussed.     

An outbreak of Mycobacterium bovis infection in fallow deer (Dama dama)

In an outbreak of Mycobacterium bovis infection in fallow deer in South Australia, 3 herds related by recent movement of deer were infected. From these 3 infected herds, 47 of 51 animals were tuberculosis at necropsy. A range of lesions was seen most of which differed from classical bovine tuberculosis in that pus was a white liquid, fibrous encapsulation was not marked and calcification was rare. Histopathology was of classical tuberculosis. M. bovis was cultured from lesions and M. avium-intracellulare was cultured from one deer with no visible lesions. The source of M. bovis infection has not been determined.