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Bovine respiratory diseases (BRD) are widespread in veal calf feedlots. Several pathogens are implicated, both viruses and bacteria, one of which, Mycoplasma bovis, is under-researched. This worldwide-distributed bacterium has been shown to be highly resistant in vitro to the main antimicrobials used to treat BRD. Our objective was to monitor the relative prevalence of M. bovis during BRD episodes, its diversity, and its resistance phenotype in relation to antimicrobial use. For this purpose, a two-year longitudinal follow-up of 25 feedlots was organized and 537 nasal swabs were collected on 358 veal calves at their arrival in the lot, at the BRD peak and 4 weeks after collective antimicrobial treatments. The presence of M. bovis was assessed by real-time PCR and culture. The clones isolated were then subtyped (polC subtyping and PFGE analysis), and their susceptibility to five antimicrobials was determined. The course of the disease and the antimicrobials used had no influence on the genetic diversity of the M. bovis strains: The subtype distribution was the same throughout the BRD episode and similar to that already described in France, with a major narrowly-variable subtype circulating, st2. The same conclusion holds for antimicrobial resistance (AMR) phenotypes: All the clones were already multiresistant to the main antimicrobials used (except for fluoroquinolones) prior to any treatments. By contrast, changes of AMR phenotypes could be suspected for Pasteurellaceae in two cases in relation to the treatments registered.

Q fever is a zoonotic abortive disease of ruminants mostly transmitted by inhalation of aerosols contaminated by Coxiella burnetii. Clusters of cases or even epidemics regularly occur in humans but, to date, there is no consensus about the best way to carry out outbreak investigations in order to identify potential farms at risk. Although environmental samples might be useful during such investigations, there are few baseline data on the presence of C. burnetii in the environment of ruminant farms. We thus investigated dust samples from cattle, sheep and goat farm buildings in order to (a) estimate C. burnetii detection frequency and bacterial loads in the environment, and (b) determine whether this environmental contamination is associated with series of abortions attributed to Q fever. We considered 113 herds with a recent abortive episode potentially related (n = 60) or not (n = 53) to C. burnetii. Dust was sampled using a swab cloth and tested by a quantitative PCR method targeting the IS1111 gene. Coxiella burnetii DNA was detected on 9 of 50 cattle farms, 13 of 19 goat farms and 30 of 40 sheep farms. On 16 cloths, bacterial loads were higher than 108 genome equivalents, levels as high as in infectious materials such as placentas and aborted foetuses. Overall, the probability of detecting C. burnetii DNA was higher on small ruminant farms than cattle farms, in herds suspected of Q fever and in large herds. We conclude that swab cloths are a putative indicator of contamination of ruminant farms by C. burnetii.

International audience; Mycoplasma bovis is considered an emerging threat to bovine production in industrialized countries. Its control depends on good husbandry and efficient chemotherapy practices. In France, clinical isolates collected after 2009 showed a drastic loss of susceptibility to most antimicrobials when compared with isolates collected in 1978-1979. The aim of the present study was to analyze the molecular mechanisms underlying the shift toward resistance to macrolides and tetracyclines and to assess whether the clinical origin of the isolates or their molecular subtypes could have influenced their pattern of evolution. We demonstrated that all M. bovis isolates collected as early as 2000 should already be considered resistant to tylosin, tilmicosin, and oxytetracycline, whatever the associated clinical signs. The shift toward resistance happened earlier for oxytetracycline and more progressively for tylosin/tilmicosin. Isolates belonging to the major subtype ST2 (n = 40) showed a homogeneous genotype for resistance, with combined alterations of G 748 A and A 2058 G in the 23S rRNA alleles for tylosin/tilmicosin and of A 965 T and A 967 T in the 16S rRNA alleles for oxytetracycline. The genotypes of ST3 or ST1 isolates (n = 9 and 25, respectively) in the process of becoming resistant were more varied. In recent years, the convergence of both ST2 and ST3 isolates toward the same resistance genotype suggests that the corresponding mutations have been selected for providing an appropriate balance between fitness cost and resistance.

To determine characteristics of natural transmission of Babesia sp. EU1 and B. divergens by adult Ixodes ricinus ticks, we examined tick salivary gland contents. We found that I. ricinus is a competent vector for EU1 and that their sporozoites directly invade erythrocytes. We conclude that EU1 is naturally transmitted by I. ricinus.

International audience; Babesia divergens, a tick-borne protozoan parasite of red blood cells, is the main agent of bovine and human babesiosis in Europe. Very few data are available concerning its life cycle and sexual reproduction inside the tick vector, Ixodes ricinus. The aim of this study was to define some markers of the B. divergens sexual stage. An in silico post-genomic approach was used to analyze genomic, transcriptomic and proteomic data and to select specific sexual stage proteins of the related apicomplexan genus Plasmodium. Three proteins, based on sequence identity between the available genomes of Plasmodium and Babesia spp., were chosen, as members of a highly conserved and apicomplexan sexual stages specific protein family (CCp) potentially involved in adhesive functions. Degenerate primers were used to amplify and clone three B. divergens orthologs (bdccp1, bdccp2, and bdccp3) corresponding to newly identified genes in this parasite. The opportunities offered by such markers to study parasite development in its vector are discussed. (C) 2010 Elsevier B.V. All rights reserved.