Response to somatic cell count-based selection for mastitis resistance in a divergent selection experiment in sheep

A divergent selection experiment in sheep was implemented to study the consequences of log-transformed somatic cell score (SCS)-based selection on resistance to natural intramammary infections. Using dams and progeny-tested rams selected for extreme breeding values for SCS, we created 2 groups of ewes with a strong divergence in SCS of approximately 3 genetic standard deviations. A survey of 84 first-lactation ewes of both the High and Low SCS lines indicated favorable responses to SCS-based selection on resistance to both clinical and subclinical mastitis. All clinical cases (n = 5) occurred in the High SCS line. Additionally, the frequency of chronic clinical mastitis,as detected by the presence of parenchymal abscesses, was much greater in the High SCS line (n = 21) than in the Low SCS line (n = 1). According to monthly milk bacterio-logical examinations of udder halves, the prevalence of infection was significantly greater (odds ratio = 3.1) in the High SCS line than in the Low SCS line, with predicted probabilities of 37 and 16%, respectively. The most frequently isolated bacteria responsible for mastitis were staphylococci: Staphylococcus auricularis(42.6% of positive samples), Staphylococcus simulans, Staphylococcus haemoliticus, Staphylococcus xylosus, Staphylococcus chromogenes, Staphylococcus lentus, Staphylococcus warneri, and Staphylococcus aureus. The incidence of positive bacteriology was greater in the High SCS line (39%) than in the Low SCS line (12%)at lambing, indicating that High SCS line ewes were especially susceptible to postpartum subclinical mastitis. Negativation of bacteriological results from one sampling time point to the next was markedly different between lines after weaning (e.g., 41 and 84% in the High and Low SCS lines, respectively). This result was consistent with differences in the duration of infection, which was much greater in the High SCS line compared with the Low SCS line. Finally, ewes from the High SCS line consistently had greater SCS in positive milk samples than did ewes from the Low SCS line (+2.04 SCS, on average), with an especially large difference between lines during the suckling period (+3.42 SCS). Altogether, the preliminary results suggest that the better resistance of Low SCS line ewes, compared with High SCS line ewes, was principally characterized by a better ability to limit infections during the peripartum period, to eliminate infections during lactation, and quantitatively to limit the inflammation process and its clinical consequences

Transcriptomic analysis of milk somatic cells in mastitis resistant and susceptible sheep upon challenge with Staphylococcus epidermidis and Staphylococcus aureus

<p>Abstract</p> <p>Background</p> <p>The existence of a genetic basis for host responses to bacterial intramammary infections has been widely documented, but the underlying mechanisms and the genes are still largely unknown. Previously, two divergent lines of sheep selected for high/low milk somatic cell scores have been shown to be respectively susceptible and resistant to intramammary infections by <it>Staphylococcus spp</it>. Transcriptional profiling with an 15K ovine-specific microarray of the milk somatic cells of susceptible and resistant sheep infected successively by <it>S. epidermidis </it>and <it>S. aureus </it>was performed in order to enhance our understanding of the molecular and cellular events associated with mastitis resistance.</p> <p>Results</p> <p>The bacteriological titre was lower in the resistant than in the susceptible animals in the 48 hours following inoculation, although milk somatic cell concentration was similar. Gene expression was analysed in milk somatic cells, mainly represented by neutrophils, collected 12 hours post-challenge. A high number of differentially expressed genes between the two challenges indicated that more T cells are recruited upon inoculation by <it>S. aureus </it>than <it>S. epidermidis</it>. A total of 52 genes were significantly differentially expressed between the resistant and susceptible animals. Further Gene Ontology analysis indicated that differentially expressed genes were associated with immune and inflammatory responses, leukocyte adhesion, cell migration, and signal transduction. Close biological relationships could be established between most genes using gene network analysis. Furthermore, gene expression suggests that the cell turn-over, as a consequence of apoptosis/granulopoiesis, may be enhanced in the resistant line when compared to the susceptible line.</p> <p>Conclusions</p> <p>Gene profiling in resistant and susceptible lines has provided good candidates for mapping the biological pathways and genes underlying genetically determined resistance and susceptibility towards <it>Staphylococcus </it>infections, and opens new fields for further investigation.</p

Prions in Milk from Ewes Incubating Natural Scrapie

Since prion infectivity had never been reported in milk, dairy products originating from transmissible spongiform encephalopathy (TSE)-affected ruminant flocks currently enter unrestricted into the animal and human food chain. However, a recently published study brought the first evidence of the presence of prions in mammary secretions from scrapie-affected ewes. Here we report the detection of consistent levels of infectivity in colostrum and milk from sheep incubating natural scrapie, several months prior to clinical onset. Additionally, abnormal PrP was detected, by immunohistochemistry and PET blot, in lacteal ducts and mammary acini. This PrPSc accumulation was detected only in ewes harbouring mammary ectopic lymphoid follicles that developed consequent to Maedi lentivirus infection. However, bioassay revealed that prion infectivity was present in milk and colostrum, not only from ewes with such lympho-proliferative chronic mastitis, but also from those displaying lesion-free mammary glands. In milk and colostrum, infectivity could be recovered in the cellular, cream, and casein-whey fractions. In our samples, using a Tg 338 mouse model, the highest per ml infectious titre measured was found to be equivalent to that contained in 6 µg of a posterior brain stem from a terminally scrapie-affected ewe. These findings indicate that both colostrum and milk from small ruminants incubating TSE could contribute to the animal TSE transmission process, either directly or through the presence of milk-derived material in animal feedstuffs. It also raises some concern with regard to the risk to humans of TSE exposure associated with milk products from ovine and other TSE-susceptible dairy species

Reproduction expérimentale des mammites à Mycoplasma agalactiae chez la brebis (activité biologique des surnageants de culture)

TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

Etiologie des mammites cliniques des ovins laitiers dans les Pyrénées-Atlantiques

L étiologie de l ensemble des mammites cliniques ayant donné lieu à des analyses bactériologiques entre 1986 et 1990 et entre 1999 et 2004 a été étudiée à partir des résultats du laboratoire départemental des Pyrénées-Atlantiques. Les données ont rassemblé 422 échantillons issus de 87 élevages de brebis laitières. Près de 51% de ces échantillons ont permis l isolement de staphylocoques, avec 26% de Staphylococcus aureus et 25% de staphylocoques à coagulase négative. Ces derniers, fréquemment isolés, ne peuvent donc être considérés chez les ovins comme des pathogènes mineurs , contrairement aux bovins. Viennent ensuite les streptocoques (4,7%), puis les coliformes (2,1%) et enfin Mannheimia haemolytica (1,2%). De fortes variations d une campagne à l autre ont été soulignées, S. aureus représentant entre 4 et 71% des isolements. Ces résultats sont comparés avec ceux d une étude homologue relative aux mammites cliniques survenues dans le bassin de Roquefort.TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

L'Agalactie Contagieuse des petits ruminants

Nombre de pages de l'ouvrage: 1824 p.National audienc

Enquête séro-épidémiologique sur les principales maladies caprines au Liban

Cette enquête séro-épidémiologique menée au Liban étudie la répartition de six pathologies caprines : la peste des petits ruminants, la pleuropneumonie contagieuse caprine, le syndrome CAEV (arthrite encéphalite caprine virale), la fièvre Q, la paratuberculose caprine, et la brucellose caprine. De manière générale, les régions géographiques les plus touchées sont la Bekaa et le Mont-Liban. Par ailleurs, le mode d'élevage mixte ovin-caprin se traduit pour une majorité d'affections par des séroprévalences supérieures à celles rencontrées lors d'élevages caprins purs'. Malheureusement, l'élevage caprin au Liban subit d'autres contraintes, politiques et économiques, aussi bien importantes que le problème des maladies contagieuses.TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

Mycoplasmoses 0f small ruminants : contagious agalactia syndrome

Contagious Agalactia syndrome is due to four main (sub) species of Mycoplasma causing long-lasting and often silent infections. Symptoms, when they occur, are variable according to Mycoplasma and host species, age and physiological status. At the flock/herd level, the most frequent clinical picture includes a mammary, respiratory, joint and ocular expression which is often incomplete. Bacteriological (and sometimes serological) confirmation of epidemio-clinical suspicions is necessary for definitive diagnosis. Antibiotherapy generally does not allow the cure of infection. Current vaccines are not sufficiently efficients to prevent Contagious Agalactia infection and are not commercialised in France. Validation and application of control plans are variable according to husbandry type and mycoplasma species ; they are effective in the French ovine or caprine districts strictly applying a sanitary policy against M. agalactiae.Le syndrome de l'agalactie contagieuse est dû à quatre mycoplasmes principaux provoquant des infections durables et souvent asymptomatiques. Les symptômes, lorsqu'ils sont exprimés, se manifestent de manière relativement variable en fonction des espèces de mycoplasmes et des espèces-hôtes, de leur âge et de leur stade physiologique. À l'échelon du troupeau, une traduction clinique mammaire, respiratoire, articulaire ou oculaire, souvent incomplète, est la plus fréquente. Le diagnostic doit reposer sur la confirmation bactériologique, voire sérologique, des suspicions épidémio-cliniques. L'antibiothérapie est décevante. Les vaccins actuels, insuffisamment efficaces, ne sont pas commercialisés en France. La validation et l'application des mesures sanitaires dépendent des filières considérées et des agents mycoplasmiques; elles ont fait la preuve de leur efficacité dans les départements appliquant une réglementation locale ovine ou caprine (M. agalactiae)

Contrôle de l'agalactie contagieuse de la brebis (validation de la recherche directe de mycoplasma agalactiae dans le lait de tank)

L'agalactie contagieuse est une des principales maladies affectant les troupeaux ovins laitiers dans les Pyrénées-Atlantiques.Jusqu'à ce jour, sa prophylaxie a été fondée sur un index sérologique, qui par la qualification de chaque troupean ovin du département, a permis une amélioration très nette de la prévalence et de l'insidence annuelles de la maladie.Or l'existence d'une importante catégorie d'animaux, les porteurs sains, parfois excréteurs de Mycoplasma agalactiae dans un troupeau. Notre étude a eu pour but de terminer la validation de la méthode de recherche directe de Mycoplasma agalactiae dans le lait de tank, et d'en explorer les avantages et les limites. Elle a été conduite en collaboration avec l'ESPLD 64, l'ADMA, la DSV et l'ENVT...TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF

Etiologie des mammites cliniques des ovins laitiers dans le bassin de Roquefort

Cette étude analyse rétrospectivement l étiologie des mammites cliniques ovines dans le bassin de Roquefort à partir de l ensemble des résultats d analyses bactériologiques réalisés entre novembre 1998 et juin 2005 dans deux laboratoires. Un total de 239 échantillons de lait, provenant de 111 élevages, ont conduit à 341 isolements. Des résultats négatifs ont été obtenus dans 9,6% des cas. Les staphylocoques ont été les principaux agents isolés : staphylocoques à coagulase négative (SCN) (30,4%) ou S. aureus (28,1%). Aspergillus fumigatus (20%), les Streptococcaceae (12,3%), les entérobactéries (5,9%), Pseudomonas spp. (5,2%) et M. haemolytica (1,5%) arrivent ensuite. Parmi les SCN, epidermidis, xylosus et lentus sont les espèces les plus fréquentes. Les fréquences d isolement apparaissent liées au stade de lactation. A. fumigatus n est isolé qu à la mise bas. Ces résultats sont comparés à ceux d une thèse homologue analysant l étiologie des mammites ovines dans les Pyrénées-Atlantiques.TOULOUSE3-BU Santé-Centrale (315552105) / SudocTOULOUSE-EN Vétérinaire (315552301) / SudocSudocFranceF