Key events 2012

The highly variable diversity of strains of 2 major bacteria involved in respiratory diseases in young cattle suggests different origins of infection. For Mannheimia haemolytica several clones (pulsotypes) were found during episodes of infectious bronchopneumonia (IPB) at the beginning of fattening. In contrast, for Mycoplasma bovis only one clone was present during high prevalence episodes. These results provide a better understanding of the transmission dynamics of these agents and will ultimately allow better adaptation of IPB control measures.

Decreases in reproductive performance and milk production associated with infection of a dairy cattle herd with Bluetongue virus serotype 8 (BTV-8) are significant and last for several weeks. Marked degradations in performance have also been found in herds located in infected areas but not reported by the surveillance system. This shows that the impact of the epizootic was much greater than the effects described in the notified herds. A secondary effect of vaccination on fertility has been identified but is very limited compared to the effects of the infection.

Several publications have reported the presence of the intracellular bacterium Wolbachia - known to be an obligate symbiote in some nematodes or a reproductive manipulator in some insects - in some ticks. Our investigations have shown that the presence of Wolbachia in the tick Ixodes ricinus is in fact due to the cryptic presence of an endoparasitoid hymenoptera that develops inside the mite.

In Flavobacterium psychrophilum isolated from rainbow trout in France, the level of genetic variability was much lower for clinical isolates than for isolates from asymptomatic carriers. Recombination is a major determinant of this diversity, and an epidemic-like population structure has been demonstrated. For this study, two methods of typing similar levels of discrimination were used (MLST and PFGE).