Diversité génétique d’Anaplasma Phagocytophilum, agent de l’anaplasmose granulocytaire, conséquences épidemiologiques et implications pour le contrôle en France

Anaplasma phagocytophilum is a tick-borne bacterium and the etiologic agent of granulocytic anaplasmosis, an emerging disease that affects a wide range of mammals. In this paper, we present the recent knowledge gained from studies on the genetic diversity of this pathogen in France. Multilocus sequence analysis (MLSA) was used to characterize the genetic diversity of A. phagocytophilum in populations of French cattle, horses, dogs, and roe deer. MLSA was based on nine loci (ankA, msp4, groESL, typA, pled, gyrA, recG, polA, and an intergenic region). Phylogenic analysis revealed three genetic clusters of bacterial variants in domesticated animals. The two principal clusters included 98% of the bacterial genotypes found in cattle, which were only distantly related to those in roe deer. One cluster comprised only cattle genotypes, while the second contained genotypes from cattle, horses, and dogs. The third contained all roe deer genotypes and three cattle genotypes. These results suggest that roe deer do not contribute to the spread of A. phagocytophilum in cattle in France. A Multiple-Locus Variable number tandem repeat (VNTR) Analysis typing technique was developed for A. phagocytophilum. Five VNTRs were selected based on the HZ human-derived strain genome, and were tested on the Webster human-derived strain and on 123 DNA samples. This study confirmed that A. phagocytophilum from roe deer or domestic ruminants belong to two different clusters, while A. phagocytophilum from red deer and domestic ruminants locate within the same cluster, questioning the respective roles of roe vs red deer as reservoir hosts for domestic ruminant strains in Europe. The molecular techniques recently developed have great potential to provide detailed information on A. phagocytophilum isolates,improving both epidemiological and phylogenic investigations, thereby helping in the development of relevant prevention and control measures.