Molecular Detection of Candidatus Anaplasma camelii in Naturally Infected Dromedary Camels (Camelus dromedarius) in Abu Dhabi Emirate, United Arab Emirates, 2019–2023

Simple Summary Camel anaplasmosis is a recent emerging disease with potential zoonotic concerns. There is poor understanding of the epidemiology of anaplasmosis in camels and, in particular of Candidatus Anaplasma camelii, which is detected in several countries including Saudi Arabia, Iran, Kenya, and Morocco. Most studies of anaplasmosis in camels relied on microscopy and serology for diagnosis, and few used molecular approaches. The present work characterizes Anaplasmataceae strains circulating in the Camelus dromedarius reservoir in the United Arab Emirates (UAE) using PCR, sequencing, and phylogenetic analysis for the first time to provide information about the largely neglected disease they cause. Between 2019 to 2023, thirty-five whole-blood samples (35/287 = 12.2%) tested positive for Anaplasmataceae spp. by PCR assay targeting the groEL gene. Of these, only nine positive samples (9/35 = 25.7%) were sequenced using groEL gene primers. A GenBank BLAST analysis revealed that all strains were 100% identical to the Candidatus Anaplasma camelii reference sequence available in the GenBank nucleotide database. Abstract The recent emergence of anaplasmosis in camels has raised global interest in the pathogenicity and zoonotic potential of the pathogen causing it and the role of camels as reservoir hosts. In the United Arab Emirates (UAE), molecular studies and genetic characterization of camel-associated Anaplasma species are limited. This study aimed to characterize molecularly Anaplasmataceae strains circulating in dromedary camels in the UAE. Two hundred eighty-seven whole-blood samples collected from dromedary camels across regions of the Abu Dhabi Emirate were received between 2019 and 2023 at the Abu Dhabi Agriculture and Food Safety Authority (ADAFSA) veterinary laboratories for routine diagnosis of anaplasmosis. The animals were sampled based on field clinical observation by veterinarians and their tentative suspicion of blood parasite infection on the basis of similar clinical symptoms as those caused by blood parasites in ruminants. The samples were screened for Anaplasmataceae by PCR assay targeting the groEL gene. Anaplasmataceae strains were further characterized by sequencing and phylogenetic analysis of the groEL gene. Thirty-five samples (35/287 = 12.2%) tested positive for Anaplasmataceae spp. by PCR assay. Nine positive samples (9/35 = 25.7%) were sequenced using groEL gene primers. GenBank BLAST analysis revealed that all strains were 100% identical to the Candidatus A. camelii reference sequence available in the GenBank nucleotide database. Phylogenetic analysis further indicated that the sequences were close to each other and were located in one cluster with Candidatus A. camelii sequences detected in Saudi Arabia, Morocco, and the UAE. Pairwise alignment showed that the UAE sequences detected in this study were completely identical and shared 100% identity with Candidatus A. camelii from Morocco and Saudi Arabia and 99.5% identity with Candidatus A. camelii from the UAE. This study demonstrates the presence of Candidatus A. camelii in UAE dromedary camels. Further critical investigation of the clinical and economical significance of this pathogen in camels needs to be carried out.