Evaluation using latent class models of the diagnostic performances of three ELISA tests commercialized for the serological diagnosis of <i>Coxiella burnetii</i> infection in domestic ruminants

International audienceELISA methods are the diagnostic tools recommended for the serological diagnosis of Coxiella burnetii infection in ruminants but their respective diagnostic performances are difficult to assess because of the absence of a gold standard. This study focused on three commercial ELISA tests with the following objectives (1) assess their sensitivity and specificity in sheep, goats and cattle, (2) assess the between-and within-herd seroprevalence distribution in these species, accounting for diagnostic errors, and (3) estimate optimal sample sizes considering sensitivity and specificity at herd level. We comparatively tested 1413 cattle, 1474 goat and 1432 sheep serum samples collected in France. We analyzed the cross-classified test results with a hierarchical zero-inflated beta-binomial latent class model considering each herd as a population and conditional dependence as a fixed effect. Potential biases and coverage probabilities of the model were assessed by simulation. Conditional dependence for truly seropositive animals was high in all species for two of the three ELISA methods. Specificity estimates were high, ranging from 94.8% [92.1; 97.8] to 99.2% [98.5; 99.7], whereas sensitivity estimates were generally low, ranging from 39.3 [30.7; 47.0] to 90.5% [83.3; 93.8]. Betweenand within-herd seroprevalence estimates varied greatly among geographic areas and herds. Overall, goats showed higher within-herd seroprevalence levels than sheep and cattle. The optimal sample size maximizing both herd sensitivity and herd specificity varied from 3 to at least 20 animals depending on the test and ruminant species. This study provides better interpretation of three widely used commercial ELISA tests and will make it possible to optimize their implementation in future studies. The methodology developed may likewise be applied to other human or animal diseases

Rôle des <em>chlamydiae</em> dans les avortements des ruminants

National audience"Chlamydia abortus est une des principales causes d’avortements infectieux des ovins et des caprins, mais l’impact réel des infections à Chlamydia chez les bovins est mal connu. Les Chlamydia induisent le plus souvent des infections asymptomatiques chez les bovins. Cet article résume les principales connaissances des infections à Chlamydia chez les bovins, ainsi que chez les ovins et les caprins, et compare leurs particularités épidémiologiques et leurs impacts économiques. Il montre que la prévalence des différentes espèces de Chlamydiaceae dans les voies génitales des bovins est très différente de celle des petits ruminants, ce qui pourrait expliquer les différences cliniques observées entre les bovins et les petits ruminants. Les avortements bovins à C. abortus sont rares et C. psittaci serait l’espèce prépondérante.

Nouveautés dans les pratiques de traite des ovins et caprins : monotraite et lactations longues

National audienceLa monotraite en élevages ovins et caprins, et les lactations longues sontdes pratiques de traite courantes en petits ruminants. La monotraite ovine et caprine est souvent pratiquée en supprimant la traite du soir. Laperte de production laitière est d’environ 14 % chez les ovins ; chez les caprins, le stade de lactation l’influence fortement. Chez les primipares, une perte de plus de 24 % est observée si la monotraite est pratiquée en début de lactation, et de 11,2 % en milieu de lactation, sachant que des pertes comparables en début ou en milieu de lactation sont aussirapportées dans la littérature. Chez les ovins comme chez les caprins, ces pertes sont compensées par un gain en organisation, grâce à laréduction du travail d’astreinte. En élevages caprins, les lactations longues sont d’abord un outil de maîtrise de la conduite du troupeau.Son intérêt réside dans l’écrêtement du pic de travail lors des mises baset dans la gestion des carrières de certaines catégories de chèvres enfonction de l’âge, du potentiel laitier et des résultats de reproduction

Vaccination vis-à-vis de la chlamydiose abortive et de la fièvre Q chez les petits ruminants

National audienceCauses majeures d’avortements de fin de gestation en élevages de petits ruminants, la chlamydiose abortive et la fièvre Q présentent de nombreuses similitudes sur le plan clinique, et en termes de réponse à l’infection. Des stratégies vaccinales ont été définies et appliquées sur le terrain depuis plusieurs années. Les vaccins vivants doivent être privilégiés à l’encontre de la chlamydiose abortive tandis qu’en matière de fièvre Q, des vaccins inactivés de phase I sont recommandés pour limiter l’excrétion. Compte tenu de la localisation intracellulaire de Chlamydia abortus et de Coxiella burnetii, l’immunité à médiation cellulaire joue un rôle majeur dans l’élimination de l’agent infectieux et dans la protection des individus vaccinés.Mis en place prioritairement dans les élevages infectés présentant des épisodes abortifs, les protocoles vaccinaux ciblent au premier chef les animaux de renouvellement et doivent être poursuivis plusieurs années en raison de la persistance d’animaux infectés et excréteurs dans les troupeaux, et pour la fièvre Q, en raison du maintien d’une contamination environnementale. Ces stratégies vaccinales doivent s’intégrer à des plans de maîtrise généraux intégrant des mesures sanitaires

Mastitis of dairy small ruminants

Staphylococci are the main aetiological agents of small ruminants intramammary infections (IMI), the more frequent isolates being S. aureus in clinical cases and coagulase negative species in subclinical IMI. The clinical IMI, whose annual incidence is usually lower than 5%, mainly occur at the beginning of machine milking and during the first third of lactation. These features constitute small ruminant peculiarities compared to dairy cattle. Small ruminant mastitis is generally a chronic and contagious infection: the primary sources are mammary and cutaneous carriages, and spreading mainly occurs during milking. Somatic cell counts (SCC) represent a valuable tool for prevalence assessment and screening, but predictive values are better in ewes than in goats. Prevention is most often based on milking machine management, sanitation and annual control, and milking technique optimisation. Elimination mainly relies on culling animals exhibiting clinical, chronic and recurrent IMI, and on drying-off intramammary antibiotherapy; this treatment allows a good efficacy and may be used selectively by targeting infected udders only. Heritability values for lactation mean SCC scores are between 0.11 and 0.15. Effective inclusion of ewe's mastitis resistance in the breeding goal has recently been implemented in France following experimental and large scale estimations of genetic parameters for SCC scores

Mastitis of dairy small ruminants

Staphylococci are the main aetiological agents of small ruminants intramammary infections (IMI), the more frequent isolates being S. aureus in clinical cases and coagulase negative species in subclinical IMI. The clinical IMI, whose annual incidence is usually lower than 5%, mainly occur at the beginning of machine milking and during the first third of lactation. These features constitute small ruminant peculiarities compared to dairy cattle. Small ruminant mastitis is generally a chronic and contagious infection: the primary sources are mammary and cutaneous carriages, and spreading mainly occurs during milking. Somatic cell counts (SCC) represent a valuable tool for prevalence assessment and screening, but predictive values are better in ewes than in goats. Prevention is most often based on milking machine management, sanitation and annual control, and milking technique optimisation. Elimination mainly relies on culling animals exhibiting clinical, chronic and recurrent IMI, and on drying-off intramammary antibiotherapy; this treatment allows a good efficacy and may be used selectively by targeting infected udders only. Heritability values for lactation mean SCC scores are between 0.11 and 0.15. Effective inclusion of ewe's mastitis resistance in the breeding goal has recently been implemented in France following experimental and large scale estimations of genetic parameters for SCC scores

Stability of microbial communities in goat milk during a lactation year: molecular approaches

International audienceThe microbial communities in milks from one herd were evaluated during 1-year of lactation, using molecular methods to evaluate their stability and the effect of breeding conditions on their composition. The diversity of microbial communities was measured using two approaches: molecular identification by 16S and 18S rDNA sequencing of isolates from counting media (two milks), and direct identification using 16S rDNA from clone libraries (six milks). The stability of these communities was evaluated by counting on selective media and by Single Strand Conformation Polymorphism (SSCP) analysis of variable region V3 of the 16S rRNA gene and variable region V4 of the 18S rRNA gene. One hundred and eighteen milk samples taken throughout the year were analyzed. Wide diversity among bacteria and yeasts in the milk was revealed. In addition to species commonly encountered in milk, such as Lactococcus lactis, Lactococcus garvieae, Enterococcus faecalis, Lactobacillus casei, Leuconostoc mesenteroides, Staphylococcus epidermidis, Staphylococcus simulans, Staphylococcus caprae, Staphylococcus equorum, Micrococcus sp., Kocuria sp., Pantoea agglomerans and Pseudomonas putida, sequences were affiliated to other species only described in cheeses, such as Corynebacterium variabile, Arthrobacter sp., Brachybacterium paraconglomeratum, Clostridium sp. and Rothia sp. Several halophilic species atypical in milk were found, belonging to Jeotgalicoccus psychrophilus, Salinicoccus sp., Dietza maris, Exiguobacterium, Ornithinicoccus sp. and Hahella chejuensis. The yeast community was composed of Debaryomyces hansenii, Kluyveromyces lactis, Trichosporon beigelii, Rhodotorula glutinis, Rhodotorula minuta, Candida pararugosa, Candida intermedia, Candida inconspicua, Cryptococcus curvatus and Cryptococcus magnus. The analyses of microbial counts and microbial SSCP profiles both distinguished four groups of milks corresponding to four periods defined by season and feeding regime. The microbial community was stable within each period. Milks from winter were characterized by Lactococcus and Pseudomonas, those from summer by P. agglomerans and Klebsiella and those from autumn by Chryseobacterium indologenes, Acinetobacter baumanii, Staphylococcus, Corynebacteria and yeasts. However, the composition of the community can vary according to factors other than feeding. This study opens new investigation fields in the field of raw milk microbial ecology

Maîtrise de la reproduction des chèvres et insémination

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Place de la maîtrise de la reproduction dans les schémas de sélection en chèvres laitières

National audienceReproductive seasonality observed in all breeds of goats originating from temperate latitudes and in some breeds from subtropical latitudes can now be controlled by artificial changes in photoperiod. Short days stimulate sexual activity, while long days inhibit it. This knowledge has allowed the development of photoperiodic treatments to control sexual activity in goats, in both the buck and doe. In the French intensive milk production system, goat artificial insemination plays an important role in controlling reproduction and, in conjunction with progeny testing, in improving milk production. Most dairy goats are inseminated out of the breeding season with deep frozen semen, after induction of oestrus and ovulation by hormonal treatment. This protocol provides a kidding rate of about 65%. New breeding strategies based on the buck effect associated with artificial insemination are being developed to reduce the use of hormones. With the development of insemination with frozen semen, a classical selection program was set up, including planned mating, progeny testing and the diffusion of proven sires by insemination in herds. Functional traits have become important for efficient breeding schemes in the dairy goat industries. Emphasis on functional traits related to udder morphology and health resulted from the knowledge established during the last decade. New windows have been opened based on new molecular tools allowing the detection and mapping of genes of economic importance in farm animals.La saisonnalité de la reproduction chez les chèvres originaires des latitudes tempérées ou subtropicales peut maintenant être contrôlée par des changements artificiels de la photopériode. Les jours courts stimulent l’activité sexuelle tandis que les jours longs l’inhibent. Ces connaissances ont permis le développement de traitements photopériodiques pour le contrôle de l’activité sexuelle des chèvres et des boucs. En France, l’Insémination Artificielle (IA) des chèvres joue un rôle central pour le contrôle des appariements et l’organisation du schéma de sélection. La plupart des chèvres sont inséminées en dehors de la saison sexuelle avec de la semence cryoconservée, après induction hormonale de l’ovulation seule ou en combinaison avec des traitements photopériodiques. Les taux de fertilité sont en moyenne de 65%. De nouvelles stratégies sont en cours d’expérimentation. Elles sont basées sur l’IA après un effet mâle pour réduire l’utilisation des hormones. Le schéma de sélection s’est développé grâce aux progrès de l’IA. Ce schéma repose sur des plans d’accouplements entre reproducteurs d’élite, le testage sur descendance en fermes et la diffusion des semences de boucs améliorateurs. Après les caractères laitiers, les carac-tères fonctionnels sont désormais pris en compte. Actuellement, l’accent est mis sur la morphologie de la mamelle. La résistance à certaines maladies est à l’étude. Outre cette approche de génétique quantitative, de nouvelles perspectives basées sur une approche moléculaire permettront de détecter des gènes économiquement intéressants pour l’élevage caprin