S Alghamdi2; A Alagaili1; A Darby3; A Stekolnikov4; J McGarry3; B Makepeace3;
1 Department of Zoology, King Saud University, Saudi Arabia; 2 Uinversity of Liverpool, UK; 3 University of Liverpool, UK; 4 Zoological Institute RAS, Russian Federation
DiscussionBackground: Rodents have become increasingly recognised as hosts of ectoparasites and reservoirs of numerous human diseases including scrub typhus (Orientia spp.), bartonellosis (Bartonella spp.), hantaviruses, Lyme disease (Borrelia burgdorferi complex), and plague (Yersinia pestis). Vector-borne bacterial zoonoses associated with rodents are a particularly large group of diseases that are emerging/re-emerging worldwide. Objectives: This study aimed to define the taxonomic diversity and bacterial microbiome of ectoparasites collected from wild rodents in the ‘Asir Region of southwestern Saudi Arabia, with a main focus on chigger mites (family Trombiculidae), the vectors of scrub typhus.
Methods: Wild rodents were trapped in scrubland across one site on the slopes of the Asir Mountains in 2016 (Al Ous’) and four sites in 2017 (Al Ous’, Al Jarf, Alogl and Wosanib). Rodents were euthanized prior to examination and all ectoparasites were collected and stored in absolute ethanol. A 10% subsample of ectoparasites was selected from each rodent for mounting in Berlese fluid and morphometric examination. Following DNA extraction, the v4 region of bacterial 16S rRNA was amplified by PCR, and amplicons were sequenced on an Illumina MiSeq. Specific PCRs were used to confirm the presence and strain of selected bacterial pathogens and symbionts.
Results: A total of 7,802 ectoparasites were obtained from 74 rodent specimens, comprising 6,135 chigger mites, 119 fleas in one species (Parapulex chephrenis), 770 ticks of at least two species (Haemaphysalis erinacei and Rhipicephalus spp.), 589 lice in two species (Polyplax brachyrrhyncha and Polyplax oxyrrhyncha), and 189 gamasid mites in two species (Laelaps lamborni, Ornithonyssus bacoti). The rodents belonged to three main species: Acomys dimidiatus, Myomys yemeni and Meriones rex. Based on the morphology of the scutum (or dorsal shield), chiggers were assigned to subgenera and provisionally into 17 species, including four putative new species: Neotrombicula sp. n., Microtrombicula aff. machadoi,Schoutedenichia. aff. thracica and Schoutedenichia sp. n. The most abundant chigger species were Ericotrombidium kazeruni, Schoutedenichia aff. geckobia and Ascoschoengastia browni. The site with the highest mean chigger infestation (139) was Al Ous’, and the host species with the greatest mean infestation rate (114) was the Eastern spiny mouse (A. dimidiatus).Ectoparasite-associated bacteria were investigated using a 16S rRNA amplicon sequencing approach. Potentially pathogenic bacteria included Borrelia spp. in chiggers, Bartonella spp. in fleas, and Coxiella spp., Francisella spp. and Anaplasma bovis in ticks. Symbiotic bacteria with putative mutualistic or parasitic phenotypes were present in fleas (Wolbachia and Spiroplasma spp.) and lice (Candidatus Legionella polyplacis).
Conclusion:This is the first survey of rodent ectoparasite diversity and zoonotic bacterial pathogens performed in the ‘Asir Regi