-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.ewe / goat / mastitis / somatic cell count / epizootiology

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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.

A family of abundant surface proteins (Vpmas [variable proteins of Mycoplasma agalactiae]) undergoing phase variation in M. agalactiae has been characterized using monoclonal antibodies and specific polyclonal sera. Two expressed members of 39 kDa (Vpma39) and 34 kDa (Vpma34), which varied in expression between clones of a lineage, shared a common amino-terminal sequence but were immunologically distinct. An aminoterminal oligonucleotide probe identified multiple vpma genes which were clustered within a 14-kb ClaI genomic fragment. Rearrangements were found to have occurred within the vpma locus between clones which correlated with changes in their Vpma phenotype. Two neighboring vpma genes were cloned and sequenced from one M. agalactiae clonal variant expressing Vpma39. The two genes, vpmaX and vpmaY, were orientated divergently and shared highly homologous 5 untranslated regions, 25-amino-acid (aa) lipoprotein leader sequences, and amino-terminal sequences. The vpmaY gene coded for 346 aa and 84% of the open reading frame, comprised of 1.5 units of a large repeat of 186 aa. Although the sequence for an entire second vpmaY repeat was present, it was prematurely terminated by insertion of two nucleotides. The vpmaX gene encoded 221 aa and possessed 102 aa of the 186-aa repeat of vpmaY. Many of the features in common between the vpma genes were also found to be shared by the vsp genes of M. bovis, which also undergo DNA rearrangements concomitant with phenotypic changes. Since M. bovis is the closest phylogenetic relative to M. agalactiae, the vpma and vsp gene families most probably represent homologous systems.

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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 bacteriological 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.

An immunodominant protein, P40, of Mycoplasma agalactiae was analyzed genetically and functionally. The gene encoding P40 was cloned from type strain PG2, sequenced, submitted to point mutagenesis in order to convert mycoplasma-specific TGA Trp codon to the universal TGG Trp codon, and subsequently expressed in Escherichia coli. Nucleotide sequence-derived amino acid sequence comparisons revealed a similarity of P40 to the adhesin P50 of Mycoplasma hominis and to protein P89 of Spiroplasma citri, which is expected to be involved in adhesion. The amino acid sequence of P40 revealed a recognition site for a signal peptidase and strong antigenic and hydrophilic motifs in the C-terminal domain. Triton X-114 phase partitioning confirmed that P40 is a membrane protein. Fab fragments of antibodies directed against recombinant purified P40 significantly inhibited adherence of M. agalactiae strains PG2 to lamb joint synovial cells LSM 192. Sera taken sequentially from sheep infected with PG2 revealed that P40 induced a strong and persistent immune response that gave strong signals on immunoblots containing recombinant P40 even 3 months after infection. The gene encoding P40 was present in a single copy in all of the 26 field strains of M. agalactiae analyzed and was not detected in closely related mycoplasma species. P40 was expressed as a protein with an apparent molecular mass of 37 kDa on sodium dodecyl sulfate-acrylamide gels by all M. agalactiae strains except for serotype C strains, which showed nonsense mutations in their p40 genes.Mycoplasma agalactiae is a major pathogen of goats and sheep. It is found particularly in Mediterranean countries but is also reported from many other areas in the world. M. agalactiae causes contagious agalactia, a syndrome that primarily affects the mammary gland, but it can also affect joints, eyes and, in some cases, the lungs (6, 13). Contagious agalactia rises to a chronic state usually explained by the capacity of mycoplasmas to evade the host immune system. Different strategies are used by mycoplasmas for this purpose, including the phase and/or size variation of the membrane surface proteins, which leads to a constantly changing surface structure and the capacity of some lipoproteins to induce the expression of up-and downmodulating cytokines (32). However, a prerequisite for colonization and infection is adhesion to the host cell (32). Adhesion involves particular proteins named adhesins. In some mycoplasmas, such as Mycoplasma pneumoniae, Mycoplasma genitalium, and Mycoplasma gallisepticum, adhesion results from the action of multiple proteins, leading to the movement and concentration of the adhesins at a specialized structure, the attachment tip organelle (7,20,21,25,35). In Mycoplasma hominis, adhesins are found dispersed over the cell surface and are directly involved in the attachment to the host cell (17, 31). The close contact between mycoplasma and the target cell membrane resulting from this adhesion is thought to favor the transfer or exchange of metabolic component...