Molecular Survey of Anaplasma Species in Small Ruminants Reveals the Presence of Novel Strains Closely Related to A. phagocytophilum in Tunisia

A survey of Anaplasma species in small ruminants is still lacking in North African countries. In this study, the presence of A. phagocytophilum, A. phagocytophilum-related species, and A. ovis was investigated in a total of 563 healthy small ruminants (303 goats and 260 sheep), from 25 randomly selected flocks sampled in Tunisia. Anaplasma spp. and A. ovis overall infection rates were 95.0% and 93.8% in sheep and 69.6% and 65.3% in goats, respectively. A. phagocytophilum was not detected in any of tested animals. A total of 20 sheep (7.7%) and 144 goats (47.5%) were infected by Anaplasma strains genetically related to A. phagocytophilum. Both in sheep and goats A. ovis prevalence was higher in adults (2 years) than in young (<2 years) subjects (p=0.001 and 0.002 for goats and sheep, respectively). In sheep, A. ovis prevalence was higher in ewes with respect to rams (p=0.010). The A. ovis infection rate was significantly lower in goats of the local breed (p=0.049) and it was higher in goats infested by ticks than in not infested animals (p=0.005). Genetic analysis of the msp4 gene of A. ovis indicated the presence of strains shared by Tunisian sheep and goats. Sequence analysis and phylogenetic studies on the basis of the 16S rRNA gene provided evidence for the circulation of at least two different potentially novel species genetically related to A. phagocytophilum in Tunisian small ruminants. These findings cause concern about specificity of serological tests used for detection of A. phagocytophilum in ruminants and provide additional information for elucidating pathogenesis and molecular epidemiology of A. phagocytophilum and related species.