Robin A.J. Nicholas

Mycoplasma bovis: disease, diagnosis, and control

Mycoplasma bovis is a major, but often overlooked, pathogen causing respiratory disease, mastitis, and arthritis in cattle. It is found worldwide and has spread into new areas, including Ireland and parts of South America, in the last decade. In Europe, it is responsible for at least a quarter to a third of all calf pneumonia although this may be an underestimate as few laboratories regularly monitor for mycoplasmas. Like all mollicutes, M. bovis is inherently refractory to certain groups of antibiotics because it does not possess a cell wall; furthermore evidence is accumulating that strains of M. bovis are becoming resistant to antibiotics, including tetracycline, tilmicosin and spectinomycin, traditionally used for their control. No vaccines are presently available for the control of M. bovis infections.

Comparison of in vitro activity of danofloxacin, florfenicol, oxytetracycline, spectinomycin and tilmicosin against recent field isolates of Mycoplasma bovis

The minimum inhibitory concentrations (MICs) and minimum mycoplasmacidal concentrations (MMCs) of danofloxacin, florfenicol, oxytetracycline, spectinomycin and tilmicosin against 62 recent British field isolates of Mycoplasma bovis were determined in vitro by a broth microdilution method. The isolates were most susceptible to danofloxacin with MIC90 and MMC90 values of 0.5 μg/ml and 1.0 μg/ml, respectively. They were less susceptible to florfenicol with a MIC90 of 16 μg/ml and MMC90 of 32 μg/ml. Oxytetracycline and spectinomycin had only a limited effect against the majority of isolates tested with MIC50s of 32 μg/ml and 4 μg/ml, respectively and MIC90s of 64 μg/ml and more than 128 μg/ml, respectively. Nearly 20 per cent of the isolates were highly resistant to spectinomycin, and tilmicosin was ineffective, with 92 per cent of the isolates having MIC values of 128 μg/ml or greater. There was no evidence of resistance by M bovis to danofloxacin.

An experimental vaccine for calf pneumonia caused by Mycoplasma bovis: clinical, cultural, serological and pathological findings

Abstract A single dose of vaccine for Mycoplasma bovis pneumonia, inactivated with saponin, was inoculated subcutaneously into 3–4 week-old calves. The calves were challenged 3 weeks later with a virulent strain of M. bovis on two occasions within 24h using the aerosol route. The calves were monitored for clinical signs and serological responses then post mortemed 3 weeks after challenge. The vaccine was shown to be highly immunogenic in calves and did not cause adverse effects. Vaccinated calves showed few clinical signs while all unvaccinated calves developed signs of pneumonia. There was a significant decrease in body weight gain in unvaccinated calves compared to vaccinates and a significant increase in lung lesions and rectal temperatures in unvaccinated calves. The vaccine also reduced the spread of M. bovis to internal organs. In conclusion the M. bovis vaccine produced a significant level of protection against a large virulent challenge.

Improvements in the diagnosis and control of diseases of small ruminants caused by mycoplasmas

Abstract Many mycoplasmas have been isolated from sheep and goats but only a small number have been linked directly to disease. The two most important are Mycoplasma agalactiae, the cause of contagious agalactia (CA), and M. capricolum subsp. capripneumoniae, the cause of contagious caprine pleuropneumonia (CCPP) which between them are responsible for significant economic losses especially in developing countries. Their prevalence is almost certainly underreported as few countries have the facilities for isolating and growing these fastidious organisms. While M. agalactiae grows relatively well in most mycoplasma media, M. capricolum subsp. capripneumoniae requires specalized media and can still take up to 2 weeks to grow. However, advances in polymerase chain reaction (PCR) technology have greatly improved the detection of both mycoplasmas. Better serological tests also enable more rapid and specific detection of antibodies to these mycoplasmas. Eradication of mycoplasmal diseases is best achieved by the slaughter of affected and contact animals but is not always practical, especially in developing countries. Although antibiotic therapy can bring about clinical improvements, it rarely eliminates the organism. The development of resistance to the traditional antibiotics such as the tetracyclines also makes this option increasingly less successful. New vaccines offer the possibility of cheaper and more effective prophylactic measures.

Mycoplasma species and related organisms isolated from ruminants in Britain between 1990 and 2000.

Between 1990 and 2000, more than 1600 mycoplasmas and the related acholeplasmas were identified from ruminant animals by the Mycoplasma Group at the Veterinary Laboratories Agency — Weybridge. Mycoplasma bovis was the most commonly identified pathogen, mostly from pneumonic calves but occasionally from cattle with mastitis and arthritis. Mycoplasma canis was first isolated in Britain in 1995 from pneumonic calves and the number of isolates increased to 18 per cent of the total mycoplasmas isolated from cattle in 1999. The ELISA for antibodies to M bovis detected 1971 positive samples (22 per cent) among 8959 serum samples, mainly from pneumonic cattle. Other mycoplasmas identified included Mycoplasma dispar from the lungs of cattle with respiratory disease, and Mycoplasma bovigenitalium from the reproductive tract of cows with vulvovaginitis and infertility. Mycoplasma bovirhinis and Acholeplasma species were found commonly but are thought to be more opportunistic than pathogenic. In sheep and goats, the majority of Mycoplasma species isolated were identified as Mycoplasma ovipneumoniae from pneumonic sheep, Mycoplasma conjunctivae from sheep with keratoconjunctivitis, and the ubiquitous Mycoplasma arginini.

Vaccination of chickens with chicken-derived Salmonella enteritidis phage type 4 aroA live oral salmonella vaccines

Two strains of Salmonella enteritidis phage type 4 isolated from chickens, SeLA5 and Se267, were virulent in Balb/c mice by intraperitoneal (i.p.) infection. In 18-20-day-old chickens given 10(7) c.f.u. intravenously (i.v.), both strains caused some deaths. One-day-old chicks infected orally with 10(9) c.f.u. of either strain also suffered limited mortality. Strain SeLA5 was the more virulent by the oral route. AroA mutants SeLA5 aroA and Se267 aroA were reduced in i.p. virulence by up to six logs in the Balb/c mouse model, did not kill 18-20-day-old chickens when injected i.v. and did not multiply in the tissues. Oral vaccination of chicks with either 10(9) c.f.u. at one-day-old or 10(5) c.f.u. at seven-day intervals until day 21 with vaccine strains SeLA5 aroA or Se267 aroA conferred significant protection against intravenous challenge with virulent strain Se109 NalR and reduced intestinal shedding following oral challenge. Seroconversion following oral vaccination was not seen with the lower dose regimen and was low with the higher dose. Seroconversion following oral challenge was marked in unvaccinated birds but much lower in vaccinated birds, suggesting that oral vaccination had prevented invasion by the challenge strain.

Differentiation of Mycoplasma species by 16S ribosomal DNA PCR and denaturing gradient gel electrophoresis fingerprinting.

ABSTRACT Denaturing gradient gel electrophoresis (DGGE) of a 16S ribosomal DNA PCR product was used to differentiate 32 mycoplasma species of veterinary significance. Twenty-seven (85%) species could be differentiated by DGGE. This method could enable the rapid identification of many mycoplasma species for which there is no specific PCR available and which are currently identified by using culture and serological tests.

Mycoplasma diseases of ruminants.

Mycoplasma diseases of ruminants , Mycoplasma diseases of ruminants , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Detection of Mycoplasma ovipneumoniae in Pasteurella-vaccinated sheep flocks with respiratory disease in England

SHEEP and goats suffer from a number of serious diseases caused by Mycoplasma species in mainland Europe, in particular contagious agalactia and pleuropneumonias, which lead to significant economic losses as a result of decreases in milk production, morbidity and, occasionally, mortality (Nicholas 2002). In contrast, only two Mycoplasma species have been shown to cause disease in small ruminants in Britain. They are Mycoplasma conjunctivae, which causes a serious but self-limiting keratoconjunctivitis (Baker and oth-

Molecular epidemiological analysis of Mycoplasma bovis isolates from the United Kingdom shows two genetically distinct clusters.

ABSTRACT Mycoplasma bovis is an important veterinary pathogen causing pneumonia, arthritis, and mastitis in infected cattle. We investigated the genetic diversity of 53 isolates collected in the United Kingdom between 1996 and 2002 with pulsed-field gel electrophoresis (PFGE), amplified fragment length polymorphism (AFLP), and random amplified polymorphic DNA (RAPD) analysis. In addition, the influence of variable surface protein (Vsp) profiles on the profiles generated with molecular typing techniques was studied. Both AFLP and RAPD separated the isolates into two distinct groups, but PFGE showed less congruence with the other techniques. There was no clear relationship between the geographic origin or year of isolation of the isolates and the profiles produced. No correlation between Vsp profiles and any of the molecular typing techniques was observed. We propose that RAPD and AFLP provide valuable tools for molecular typing of M. bovis.