Christophe Chartier

Anthelmintic resistance (AR) in gastrointestinal nematodes is insufficiently studied in cattle in many European regions, including France, where only three studies have been conducted in the north-west. This study evaluated the efficacy of benzimidazoles and avermectins in cattle from a mid-mountain region in central France. Faecal egg count reduction tests (FECRT) were performed in 22 groups of 10–25 calves from 16 dairy or beef farms. Each group received either oral oxfendazole (OFZ, 11 groups) or injectable ivermectin (IVM, 11 groups). Faecal samples were collected in a paired study design before (D ₀ ) and after treatment (D _10-14 for OFZ, D _14-17 for IVM). Individual faecal egg counts (FECs) were determined using the Mini-FLOTAC method, and pooled faecal samples were cultured per group to determine the proportions of Ostertagia and Cooperia larvae using droplet digital PCR. Efficacy classification (resistant, susceptible or inconclusive) was determined for each group according to the WAAVP guidelines, using the fecrt.com web application and the clinical protocol scenario with a grey zone of 90–99%. IVM resistance was detected on 10 of 11 farms, with 33–49% and 51–67% of larvae being Ostertagia and Cooperia after treatment, respectively. The remaining farm had inconclusive results. OFZ resistance was detected on 2 of 11 farms, with 100% and 97% of larvae being Ostertagia after treatment. The remaining 9 farms were classified as susceptible. This study provides valuable local insights into AR, which could help raise awareness among farmers and veterinarians and encourage changes in treatment practices.

In young cattle, bovine respiratory disease (BRD) is a major cause of death and Mannheimia haemolytica is a frequent pathogen. Knowledge of fatal BRD in adult cattle is more limited. We assessed the importance of infectious BRD as a cause of death in adult cattle and determined the associated pathogens. We analyzed data from 737 adult cattle necropsies at the Pathology Unit for Large Animals at Oniris, Nantes, France over a 6 year period (2013–2019). Each carcass was subjected to a complete necropsy. Lungs showing macroscopic lesions were classified into three categories: infectious primary pulmonary (IPP) lesions, thromboembolic pneumonia (TEP) and others (aspiration pneumonia, verminous pneumonia, and local extension of an extra-pulmonary inflammatory process). Half of the lungs with IPP macroscopic lesions were sampled for histology and submitted for polymerase chain reaction. BRD was the second leading cause of death (15.7%) after digestive diseases (32.2%). A strong predominance of IPP lesions (42.3%) and TEP lesions (39.6%) was also demonstrated. In IPP macroscopic lesions, fibrinous, hemorrhagic and/or hecrotic (FHN) bronchopneumonia accounted for 77.6% of macroscopic lesions. Mannheimia haemolytica was significantly associated with FHN bronchopneumonia macroscopic lesions. This study suggests that Mannheimia haemolytica should be included in the differential diagnosis of BRD in adult cattle.

Our objective was to measure the efficacy of ivermectin (IVM) and benzimidazoles (BZ, i.e. fenbendazole and albendazole) in 15 cattle farms in western France and southern Italy. A total of 11 groups were treated with IVM and 11 with BZ. Efficacy was assessed by calculating the percentage of faecal egg count reduction (%FECR) using the pre- and post-treatment arithmetic means. Anthelmintic resistance was considered to be present when the %FECR was <95% and the lower limit of the 95% confidence interval <90%. For IVM, the percentages of FECR ranged from 73% to 100%. Lack of efficacy to IVM was detected in two farms out of four in France, but was not detected in any of the seven farms in Italy. For BZ, the percentages of FECR ranged from 95% to 100%. No case of BZ resistance was detected in the five farms in France and the six farms in Italy.

Faecal egg counts (FEC) and the FEC reduction test (FECRT) for assessing gastrointestinal nematode (GIN) infection and efficacy of anthelmintics are rarely carried out on ruminant farms because of the cost of individual analyses. The use of pooled faecal samples is a promising method to reduce time and costs, but few studies are available for cattle, especially on the evaluation of different pool sizes and FECRT application. A study was conducted to assess FEC strategies based on pooled faecal samples using different pool sizes and to evaluate the pen-side use of a portable FEC-kit for the assessment of FEC on cattle farms. A total of 19 farms representing 29 groups of cattle were investigated in Italy and France. On each farm, individual faecal samples from heifers were collected before (D0) and two weeks after (D14) anthelmintic treatment with ivermectin or benzimidazoles. FEC were determined individually and as pooled samples using the Mini-FLOTAC technique. Four different pool sizes were used: 5 individual samples, 10 individual samples, global and global on-farm. Correlations and agreements between individual and pooled results were estimated with Spearman’s correlation coefficient and Lin’s concordance correlation coefficients, respectively. High correlation and agreement coefficients were found between the mean of individual FEC and the mean of FEC of the different pool sizes when considering all FEC obtained at D0 and D14. However, these parameters were lower for FECR calculation due to a poorer estimate of FEC at D14 from the faecal pools. When using FEC from pooled samples only at D0, higher correlation and agreement coefficients were found between FECR data, the better results being obtained with pools of 5 samples. Interestingly, FEC obtained on pooled samples by the portable FEC-kit on-farm showed high correlation and agreement with FEC obtained on individual samples in the laboratory. This field approach has to be validated on a larger scale to assess its feasibility and reliability. The present study highlights that the pooling strategy and the use of portable FEC-kits on-farm are rapid and cost-effective procedures for the assessment of GIN egg excretion and can be used cautiously for FECR calculation following the administration of anthelmintics in cattle.

Anaplasma ovis is a major cause of small ruminant anaplasmosis, a tick-borne disease mainly affecting small ruminants in tropical and subtropical regions of the world. Due to health and production problems in dairy goat flocks in Corsica, France, and the demonstration of A. ovis infection in some animals, an extensive survey was conducted in the island in spring 2016. The aim of the survey was to determine the prevalence and geographical distribution of A. ovis infections in goats and ticks as well as possible relationships with anaemia and other health indicators. In addition, the genetic diversity of A. ovis was evaluated. Blood and faecal samples were collected in 55 clinically healthy flocks (10 goats per flock) for A. ovis qPCR, haematocrit determination, paratuberculosis ELISA seropositivity and gastrointestinal nematode egg excretion quantification. Ticks were collected, identified and processed for A. ovis DNA detection. A high prevalence of A. ovis DNA detection was found at the individual (52.0%) and flock levels (83.6%) with a within-flock prevalence ranging between 0–100%. Rhipicephalus bursa was the only tick species collected on goats (n = 355) and the detection rate of A. ovis DNA in ticks was 20.3%. Anaplasma ovis DNA prevalence was higher in flocks located at an altitude above 168 m, in goats of Corsican/crossbred breed and in goats > 3 years-old. No relationship was found between A. ovis DNA detection at the individual or flock level and haematocrit, paratuberculosis seropositivity or gastrointestinal parasites. Positive A. ovis goat samples were used for amplification of gltA and msp4 genes for species confirmation and strain identification, respectively. Sequence and phylogenetic analysis of these genes confirmed the detection of A. ovis and allowed identification of six different strains of this pathogen (named Corsica 1-6 (COR1-6). While the msp4 sequence of strain COR1 had 100% identity with strains previously reported, COR2 to 6 were found to be novel strains. The strain COR1 was the most represented, corresponding to 94.6% of the msp4 sequences obtained. The results showed a relatively high genetic diversity of A. ovis associated with high bacterial prevalence in goats.

Chez les ruminants élevés au pâturage, les strongles gastro-intestinaux (SGI) peuvent induire des pertes de production, voire des atteintes cliniques chez les animaux non immuns. Le contrôle de l’infestation repose essentiellement sur les traitements anthelminthiques (AH) administrés fréquemment sans évaluation préalable de la réalité du risque parasitaire. Cette synthèse vise tout d’abord à exposer les principaux risques associés à ce recours insuffisamment raisonné aux AH : apparition de populations de parasites résistants aux AH, écotoxicité pour la microfaune prairiale dégradant les fèces, et installation retardée de l’immunité anti-strongles (notamment chez les bovins). Les stratégies de traitement ciblé-sélectif devraient permettre de maîtriser ces risques tout en prévenant les atteintes cliniques et sécurisant les performances des animaux. Il s’agit de rationaliser les traitements AH en ciblant les troupeaux ou les lots et les périodes à risque, et en sélectionnant les individus les plus parasités ou « souffrant » le plus du parasitisme. Cette synthèse vise donc ensuite à décrire les outils et les indicateurs étudiés pour mettre en œuvre de telles stratégies chez les ruminants. Il s’agit d’indicateurs zootechniques (gain moyen quotidien, parité, niveau de production…), cliniques (FAMACHA©, index de diarrhée…), parasitologiques (coproscopie, niveau d’anticorps anti-SGI…), ou d’indicateurs de conduite (modalité de pâturage), et aussi d’outils informatiques (modélisation du recyclage parasitaire). Leur fiabilité et leur opérationnalité sont variables. La mise en place de telles stratégies nécessitera de dépasser les freins à l’acceptation de ces nouvelles pratiques tant au niveau des éleveurs que des vétérinaires prescripteurs. Cet usage raisonné des AH assurerait une meilleure durabilité du contrôle de l’infestation par les SGI.