First molecular detection of Ehrlichia spp. and Theileria spp. closely related to Theileria parva in Hyalomma dromedarii ticks infesting camels in the United Arab Emirates

Abstract

Background and Aim: Tick-borne pathogens pose a growing threat to animal health and livestock production, particularly in arid regions where Hyalomma ticks are abundant. Hyalomma dromedarii, the predominant camel tick in the Middle East and North Africa, has been implicated in the transmission of several bacterial and protozoal pathogens. Despite the economic importance of camels in the United Arab Emirates (UAE), comprehensive surveillance of tick-borne microorganisms in H. dromedarii across the country remains limited. This study investigated the occurrence of Anaplasma, Rickettsia, Ehrlichia, Theileria, and Babesia in H. dromedarii collected from camels in the UAE and characterized the detected pathogens using molecular and phylogenetic analyses. Materials and Methods: A total of 804 camels from 182 farms in Abu Dhabi, Dubai, Sharjah, and Umm Al Quwain were examined between June 2022 and October 2023. One semi-engorged female H. dromedarii tick was selected from each camel whenever available, yielding 671 ticks for molecular analysis. Genomic DNA was extracted and screened using polymerase chain reaction (PCR) assays targeting Anaplasma, Rickettsia, Ehrlichia, Theileria, and Babesia. Positive amplicons were confirmed by Sanger sequencing, and phylogenetic analyses were performed to determine their genetic relationships with previously reported isolates. Results: No evidence of Anaplasma, Rickettsia, or Babesia DNA was detected in the analyzed ticks. In contrast, Theileria and Ehrlichia DNA were detected in 0.60% (4/671) and 0.30% (2/671) of samples, respectively. The detected Ehrlichia represents the first molecular record of this genus in H. dromedarii from the UAE. One Theileria sequence exhibited 98.96% nucleotide similarity to Theileria parva; however, species-specific PCR failed to confirm T. parva, indicating that the detected organism was a closely related Theileria species rather than confirmed T. parva. Phylogenetic analyses showed that the detected Ehrlichia and Theileria sequences clustered with corresponding reference sequences reported previously from other geographical regions. Conclusion: This study provides the first molecular evidence of Ehrlichia in H. dromedarii ticks in the UAE and identifies a Theileria isolate closely related to T. parva. Although pathogen prevalence was low, these findings expand current knowledge of tick-borne microorganisms associated with camel ticks in the UAE and highlight the need for continued molecular surveillance to clarify the epidemiological significance, host-pathogen interactions, and potential veterinary and One Health implications of these microorganisms in the region. Keywords: camel, Ehrlichia, Hyalomma dromedarii, molecular epidemiology, One Health, polymerase chain reaction, Theileria, United Arab Emirates.