Abstract:
Serological surveys have confirmed Anaplasma marginale and Anaplasma phagocytophilum infections in
dromedary camels, but molecular surveys and genetic characterisation of camel-associated Anaplasma
species are lacking. In this study, we detected tick-borne Anaplasmataceae in 30 of 100 (30%) healthy
dromedary camels screened using a combined 16S rRNA–groEL PCR-sequencing approach. Nucleotide
sequencing confirmed Anaplasmataceae genome presence in 28 of the 33 16S rRNA PCR-positive samples,
with two additional positive samples, for which 16S rRNA sequence data were ambiguous, being
identified by groEL gene characterisation. Phylogenetic analyses of a 1289 nt segment of the 16S rRNA
gene confirmed the presence of a unique Ehrlichia lineage and a discrete Anaplasma lineage, comprising
three variants, occurring at an overall prevalence of 4% and 26%, respectively. Genetic characterisation of
an aligned 559 nt groEL gene region revealed the camel-associated Anaplasma and Ehrlichia lineages to be
novel and most closely related to Anaplasma platys and Ehrlichia canis. Based on the confirmed
monophyly, minimum pairwise genetic distances between each novel lineage and its closest sister taxon,
and the inability to isolate the bacteria, we propose that Candidatus status be assigned to each. This
first
genetic characterisation of Anaplasmataceae from naturally infected, asymptomatic dromedary camels in
Saudi Arabia confirms the presence of two novel lineages that are phylogenetically linked to two
pathogenic canid species of increasing zoonotic concern.
