Seasonal dynamics, spatial distribution and genetic analysis of Anaplasma species infecting small ruminants from Northern Tunisia.

To date, there have been no reports on seasonal variations of Anaplasma spp. in South Mediterranean small ruminants. In this longitudinal field study, single and mixed Anaplasma spp. infections in small ruminants from five different governorates belonging to three bioclimatic zones from the North of Tunisia were evaluated according to seasons. A total of 1685 blood small ruminant samples were collected in spring (355 sheep and 241 goats), summer (249 sheep and 202 goats), autumn (236 sheep and 186 goats) and winter (132 sheep and 84 goats). Molecular survey of A. ovis and A. bovis showed that average prevalence rates were 35.6% (minimum 30.7% in spring and maximum 43.6% in autumn) and 7.4% (minimum 0.9% in spring and maximum 18.1% in summer), respectively, in sheep, and 46% (minimum 21.7% in summer and maximum 65.5% in winter) and 10.1% (minimum 2.2% in autumn and maximum 23.8% in summer), respectively, in goats. A. phagocytophilum was not detected in all investigated animals. The infection profiles of A. ovis and A. bovis show that anaplasmosis caused by A. ovis is endemic in small ruminants from all investigated bioclimatic areas during the four seasons but conversely, A. bovis infection is highly intensified only in the summer. A. ovis and A. bovis infections were validated by sequencing. The comparison of the 16S rRNA sequences of A. bovis variants showed 100% identity between Tunisian variants isolated from goats, sheep and cattle. The analysis of A. ovis msp4 sequences revealed two different genetic variants previously described in Italy. This is the first survey outlining seasonal dynamics of Anaplasma spp. infections in Tunisian small ruminants. This situation should to be taken into account if anaplasmosis control programs in these domesticated animals are envisaged.