AlthoughBabesia divergensis the the principal confirmed zoonoticBabesia sp. in Europe, there are gaps in our knowledge of its biology and transmission by the tickIxodes ricinus. In order to reproduce the part of the parasite cycle that occurs in the vector, anin vitroanimal skin feeding technique on blood containingin vitrocultivatedB. divergenswas developed. Parasite DNA was detected in all samples of salivary glands of nymphs and adults that had fed on parasitized blood as larvae and nymphs, respectively, indicating acquisition as well as a transtadial persistence ofB. divergens. PCR performed on eggs and larvae produced by females that had fed on parasitized blood demonstrated the existence of a transovarial transmission of the parasite. GorgingB. divergensinfected larvae on non-infected gerbils showed persistance of the parasite over moulting into the resulting nymphs. These results indicate that the parasitic stages infective for the vector (i.e. the sexual stages) can be producedin vitro. To our knowledge, this is the first report of artificial feeding ofI. ricinusvia membrane as well asin vitrotransmission ofB. divergensto its vector. The opportunities offered by the use of such a transmission model of a pathogen byI. ricinusare discussed.

Mycoplasma bovis is considered a major contributor to respiratory diseases in young cattle. Resistant M. bovis isolates have increasingly been reported worldwide due to extensive use of antimicrobials to treat bovine pneumonia. The frequency of isolates resistant to fluoroquinolones varies considerably from one country to another. The MICs of isolates collected in France have only increased from “very low” to “low.” The present study was conducted to investigate whether alterations in the quinolone resistance-determining regions (QRDRs) could account for this slight modification in susceptibility. No correlation between QRDR alterations and increased MICs was evidenced in clinical isolates. In addition, all clinical isolates were subtyped, and the tendencies of the different sequence types to develop resistance through mutations in QRDRs under selective pressure in vitro were examined. In vitro , 3 hot spots for mutations in QRDRs (position 83 in GyrA and positions 80 and 84 in ParC) were associated with a high level of resistance when cumulated. We showed that the point mutations in the QRDRs observed in vitro were different (in location and selection rapidity) between the different subtypes. Our in vitro observations were corroborated by the recent detection of a clinical isolate highly resistant to fluoroquinolones (MIC ≥ 16 μg/ml) and belonging to the subtype which easily accumulates QRDR alterations in vitro . The current increased prevalence of this subtype in clinical isolates highlights the urgent need to control fluoroquinolone usage in veterinary medicine.

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.

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.

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.