First detection of Amblyomma variegatum and molecular finding of Rickettsia africae in Sardinia, Italy

Abstract Here we present the first report, in the Sardinia Island, of an individual of the species Amblyomma variegatum, and the molecular detection of a pathogen, Rickettsia africae, carried by the aforementioned tick. The tick, the second individual of this species reported in Italy (the first one was reported in Sicily by Albanese in 1971) was collected in August 2018 from the inguinal region of an adult female sheep in a farm located near Sassari (North-West Sardinia). The tick was identified as an adult male of A. variegatum under a stereomicroscope using morphological keys. The identification was confirmed by sequencing a fragment of the 12S rRNA gene. The subsequent phylogenetic analysis allow the positioning of the sequence from the collected tick within the cluster of African A. variegatum and, in particular, embedded within the previously identified West African group. We tested the tick for the presence of microorganisms of the genera Ehrlichia, Rickettsia, Anaplasma, Theileria and Babesia, using published PCR protocols. The tick was found positive to Rickettsia and the obtained sequence matched at 100% identity with R. africae. The area where the tick was detected was inspected on multiple occasions, looking for other specimens of A. variegatum, without any results. In the same period another male specimen of A. variegatum was found in Haute Corse in 2019. The authors' hypothesis is that the presence of the A. variegatum specimen is an occasional finding, probably linked to the migrating birds that cross Sardinia and Corsica from Africa during summer. While we agree that the current situation is that of occasional finding, it must be considered that global warming could increase the risk of establishment of colonies of these ticks, that show a strong spreading capability. It is also important to emphasize that this tick species is a proven vector and reservoir of R. africae, an uncommon pathogen in Italy, thus additional monitoring must be performed as the establishment of a stable population in Sardinia could represent a serious public health issue.