Molecular typing of Mycoplasma agalactiae: tracing European-wide genetic diversity and an endemic clonal population

Mycoplasma agalactiae causes chronic infections in small ruminants and remains endemic in many regions of the world, despite intensive and costly eradication programs. In this study, the innate genomic plasticity of M. agalactiae was exploited to design and assess a combination of molecular epidemiological tools to trace the pathogen in different geographic locations and to understand its emergence or re-emergence after eradication campaigns. For this purpose, two collections of M. agalactiae isolates, representing European outbreaks or localized endemic disease in a single region of France, were subjected to RFLP (Restriction Fragment Length Polymorphism) analyses using two sets of DNA probes (distributed across the genome and specific for the vpma gene locus), and a previously described VNTR (Variable Number Tandem Repeats) analysis. A combination of four genome-specific DNA probes and two VNTRs gave the highest discriminative power. Molecular typing revealed that, while isolates from diverse geographical origins fell into clearly different groups, the endemic disease repeatedly observed in the Western Pyrenees region over the past 30 years has been caused by a unique subtype of M. agalactiae. This indicates that the re-emergence of the pathogen after seemingly successful eradication programs is not due to the importation of exotic strains, but to the persistence of local reservoirs of infection.     

Regulation of Oestrus ovis (Diptera: Oestridae) populations in previously exposed and naïve sheep

Larvae of Oestrus ovis (Insecta: Diptera: Oestridae) are common parasites of nasal and sinus cavities of sheep and goats. During larval development, a specific immune reaction is initiated by the host with a humoral local and systemic response and the recruitment of eosinophils and mast cells in the upper airways mucosae. Nevertheless, the roles of these responses in the regulation of O. ovis larvae populations in sheep are not yet known. The aim of this study was to compare the establishment and the development of larvae as well as some inflammatory or immune parameters between different groups of half-sibling sheep: (i) a primed group experimentally infected twice before a challenge infection, (ii and iii) two groups infected once only and previously treated with a long-lasting cortico?d before the challenge (one group) or not (the other group). A fourth group of non-infected animals was added in the experimental design. The larval establishment rate was 23% in the cortico?d treated group compared to about 10% in the two other infected groups. Moreover, the larval development appeared more rapid in the cortico?d treated group than in the two other infected groups suggesting that the inflammatory response is involved in the regulation of O. ovis populations. By contrast, no differences in the establishment rates were shown in the primed group compared to the na?ve group (without cortico?d treatment) despite evidence of higher eosinophilia, serum specific IgG, and immediate hypersensibility to excretory-secretory products of larvae. The specific lymphocyte proliferation was reduced in the primed group compared to the na?ve one suggesting that an immuno-suppression occurs following repetitive O. ovis infections.