Genetic characterization of Anaplasma marginale strains from Tunisia using single and multiple gene typing reveals novel variants with an extensive genetic diversity

Anaplasma marginale, which is responsible for bovine anaplasmosis in tropical and subtropical regions, is a tick-borne obligatory intraerythrocytic bacterium of cattle and wild ruminants. In Tunisia, information about the genetic diversity and the phylogeny of A. marginale strains are limited to the msp4 gene analysis. The purpose of this study is to investigate A. marginale isolates infecting 16 cattle located in different bioclimatic areas of northern Tunisia with single gene analysis and multilocus sequence typing methods on the basis of seven partial genes (dnaA, ftsZ, groEL, lipA, secY, recA and sucB). The single gene analysis confirmed the presence of different and novel heterogenic A. marginale strains infecting cattle from the north of Tunisia. The concatenated sequence analysis showed a phylogeographical resolution at the global level and that most of the Tunisian sequence types (STs) formed a separate cluster from a South African isolate and from all New World isolates and strains. By combining the characteristics of each single locus with those of the multi-loci scheme, these results provide a more detailed understanding on the diversity and the evolution of Tunisian A. marginale strains.