Molecular characterization of six Hyalomma species using mitochondrial markers

Mitochondrial genetic markers based phylogenetic analyses of Hyalomma dromedarii Koch, 1844 (Acari: Ixodidae)

The hard tick Hyalomma dromedarii, a vector for numerous animal and human pathogens, was investigated for genetic diversity using the mitochondrial cytochrome C oxidase subunit I (cox I) and 16S ribosomal RNA (16S rRNA) genes. Hyalomma dromedarii sequences (n = 11 cox I; n = 7 16S rRNA) were deposited in GenBank (LC761179-89, LC761173-78, LC654692), showing 99.52-100 % (cox I) and 98.15-100 % (16S rRNA) similarity to existing GenBank sequences. Phylogenetic analysis revealed monophyletic clades for H. dromedarii sequences from this study and GenBank. Haplotype network analysis identified 34 and 11 haplotypes for the cox I and 16S rRNA genes, respectively, displaying stellate configurations. The overall cox I dataset showed very low nucleotide diversity (0.0019 ± 0.0002) and high haplotype diversity (0.535 ± 0.052). In contrast, the 16S rRNA gene dataset displayed low nucleotide (0.00211 ± 0.00071) and haplotype (0.351 ± 0.079) diversities. Neutrality tests showed significant negative values (Tajima's D, Fu and Li's D, and Fu and Li's F), indicating recent population expansion or selective sweep. Pairwise FST values (-0.00942 to 0.02007 for cox I; -0.04878 to 0 for 16S rRNA) suggested non-significant genetic differentiation between populations, supported by high gene flow (Nm) values. This study provided novel insights into H. dromedarii population genetics, revealing recent expansion, weak population differentiation, and high gene flow. These findings have implications for understanding the tick's evolutionary history and epidemiological significance.

Hyalomma aegyptium: Observed global distribution, imported specimens, preferred hosts and vector competence

The tortoise tick Hyalomma aegyptium (Linnaeus, 1758) is a three-host tick, predominantly infesting land tortoises of the genus Testudo. A database was compiled, resulting in 557 H. aegyptium georeferenced locations in the Palearctic. This dataset covers the entire range of H. aegyptium for the first time. Thus, the natural distribution area of H. aegyptium extends from Morocco in northwestern Africa to Kyrgyzstan in Central Asia between 10° W-73° E and 28-46° N, which is shown in an overview map and four detailed maps covering North Africa, the Balkans, the Near East, and the Middle East. In addition, documented findings on land tortoises that have been exported worldwide as popular pets give an impression of the occurrence of H. aegyptium outside its natural distribution. The host species is known from 424 mapped H. aegyptium locations, which can be ranked as follows: 92.9% Testudo spp., 4.0% mammals (mainly hedgehogs and hares), 1.7% humans, 0.9% lizards and 0.5% birds. If only tortoise hosts are considered, these are 92.6% Testudo graeca, 3.8% Testudo hermanni, 2.8% Testudo horsfieldii and 0.8% Testudo marginata. It is striking that no infestation with H. aegyptium has been detected on Testudo kleinmanni in their natural habitat, but it was detected on imported specimens in Malta and the USA. Although numerous tick-borne pathogens have been detected in H. aegyptium, vector competence, i.e. the experimentally proved transmission of pathogens from the vector to the host, could only be demonstrated for three pathogens. These are the two blood parasites Hemolivia mauritanica and Hepatozoon kisrae as well as Coxiella burnetii, the causative agent of Q fever.

Identification of ticks and tick-borne pathogens of wildlife necropsy cases submitted to the SANBI National Zoological Gardens, South Africa

Ticks are arachnid blood-feeding parasites, which infest livestock, wildlife, and humans, transmitting medically and veterinary significant pathogens. Their biodiversity and distribution in wild animals remains complex. This study analysed archived tick samples (n = 48) from the South African Biodiversity Institute (SANBI) Wildlife Biobank utilizing morphology and genetic analyses of the 16S rRNA and COI (DNA barcoding) mitochondrial genes to identify ticks collected among 13 vertebratesavian, reptilian, and mammalian host species. The specimens came from nine localities including nature reserves and captive facilities (zoological garden) in South Africa, Namibia, and Botswana. These ticks were also assessed for associated pathogens with the reverse line blot (RLB) hybridization assay. Seven tick genera, Amblyomma, Hyalomma, Haemaphysalis, Ixodes, Rhipicephalus, Rhipicentor, and Otobius were identified, with Amblyomma being the most prevalent (22.9 %) in our sample set. Obtained sequences were 95-100 % similar to published records of tick species collected from wild and domestic animals, as well as those collected from vegetation, from different southern African areas. However, tick specimens (n = 3) identified morphologically as Hyalomma truncatum, Rhipicephalus e. evertsi, and R. simus, were, on a molecularly level, more closely related to their sister taxa (H. glabrum, R. e. mimeticus, and R. gertrudae, respectively) suggesting a need for taxonomic verification. With the RLB hybridization assay, six samples reacted with the Ehrlichia/Anaplasma genus-specific probe, while two reacted with the Theileria/Babesia genus-specific probe. Sequencing of the RLB amplicons targeting the 18S rRNA gene (n = 2) indicated 100 % similarity to Hepatozoon fitzsimonsi, while one was closely related to He. ingwe with 99.39 % similarity. The results show that wildlife harbour different tick species, and pathogen detection identified novel genotypes, indicating wildlife as potential pathogens reservoirs. This study enhances our understanding of tick biodiversity, distribution and highlights wildlife's role in harbouring diverse tick species and novel pathogens.

Intra- and interspecific variation of Amblyomma ticks from southern Africa

BACKGROUND

Amblyomma spp. ticks, known for their long mouthparts, bright ornate appearance and aggressive hunting behaviour, are vectors of a number of important pathogens. In southern Africa, 17 Amblyomma spp. are currently documented. Of these species, Amblyomma hebraeum and Amblyomma variegatum have been well studied due to their wide geographical range and their status as competent vectors of pathogens that are of veterinary and medical importance. Studies on other Amblyomma spp. in southern Africa have been neglected, fostering ongoing debates on the validity of certain species such as Amblyomma pomposum. This study investigated the inter- and intra-species variation of Amblyomma ticks collected in southern Africa, focusing on resolving the dispute about A. pomposum and A. variegatum being distinct species.

METHODS

Four Amblyomma tick species were collected from Angola, Mozambique, South Africa, Zambia and Zimbabwe, and were identified morphologically as Amblyomma eburneum (208), A. hebraeum (4758), A. pomposum (191) and A. variegatum (2577) using identification keys. Gene amplification targeting the 12S and 16S rRNA, cytochrome oxidase I, cytochrome B and internal transcribed spacer-2 genes was conducted for 204 ticks, for which varying success was achieved during amplification for each of the markers. Maximum likelihood analyses were performed in IQ-TREE.

RESULTS

The phylogenetic topologies and ABGD analyses of each individual gene clustered A. pomposum within the A. variegatum clade, while clearly separating A. eburneum and A. hebraeum from all other species. None of the genetic markers indicated intraspecific structuring on the basis of geographical origin, despite great distances between sampling sites.

CONCLUSION

Our study concludes that there is insufficient molecular evidence to differentiate A. pomposum and A. variegatum from each other. We highlight the need for whole mitochondrial genome sequencing of these two species to resolve the ongoing controversies. Furthermore, we propose mating and hybrid viability studies between the two species to confirm their reproductive isolation.

Population structure and haplotype network analyses of Hyalomma anatolicum based on the large subunit ribosomal RNA (16S rRNA) gene

Hyalomma anatolicum, an Anatolian hard tick is a well-recognized vector involved in the transmission of various pathogens to animals and humans. The present study elucidated the population structure and haplotype network of H. anatolicum based on the mitochondrial large subunit ribosomal RNA (16S rRNA) gene sequence. The population structure and haplotype network analysis of 75 sequences archived in the GenBank, including the 15 sequences generated herein, yielded 24 haplotypes. Haplotype 1 (Hap_1) was the predominant haplotype consisting of 45 sequences from India, China, Pakistan, Turkey, Egypt, Iraq, and Tajikistan. The complete haplotype network exhibited a stellate conformation, highlighting a recent population expansion. The overall dataset, together with the sequences corresponding to India, China, and Pakistan, showed a high haplotype (0.638 ± 0.065, 0.671 ± 0.103, 0.753 ± 0.099, and 0.854 ± 0.061, respectively) and low nucleotide (0.00407 ± 0.00090, 0.00525 ± 0.00196, 0.00680 ± 0.00233, and 0.00453 ± 0.00056, respectively) diversity, further emphasized a recent population expansion. The neutrality indices including Tajima's D, Fu and Li's D, and Fu and Li's F for the complete dataset (- 2.661, - 6.008, and - 5.649, respectively) as well as for the sequences from India (- 2.223, - 3.414, and - 3.567, respectively) were negative, suggesting deviation from neutrality and a recent population expansion. The present study provided novel insights into the population structure and haplotype networks of H. anatolicum based on the mitochondrial 16S rRNA gene, and the different tests inferred a low genetic differentiation and suggested a recent population expansion of this economically important tick species.

Genetic diversity of Hyalomma marginatum in Tunisia is not influenced by the bio-climate

Ticks are important ectoparasites responsible for the transmission of several pathogens with significant medical, veterinary, and economic impacts. Climate and social changes have generated substantial changes in ticks' distribution, abundance, and activity patterns, including ticks belonging to the Hyalomma marginatum species. Knowledge on the genetic structure and dynamics of H. marginatum populations might contribute to a better understanding of their current and future evolution under the effects of anthropogenic factors and eco-climatic changes. In the present study, we investigated the genetic structure and phylogenetic distribution of H. marginatum across three bioclimatic regions in Tunisia using two mitochondrial markers (16S and 12S rRNA). The molecular investigations were based on 47 adult H. marginatum ticks collected from humid, upper semi-arid, and sub-humid regions of Tunisia. Our results revealed a genetic diversity of 0.278% and 0.809% using the 16S and 12S markers, respectively. The low genetic diversity that we observed raises the hypothesis of a bottleneck event occasioned by a reduction in the size of the tick population under the effects of environmental factors and/or human activities. This hypothesis is supported by the population's demographic history analysis, which revealed a clear deviation from neutrality and supports the occurrence of a bottleneck event followed by a demographic expansion. The fact that most 16S and 12S variability was present in the ticks from the humid bioclimatic zone may suggest that those ticks represent the ancestral population. Overall, the analysis has shown that the phylogenetic clusters do not correspond to the bioclimatic zones.

Pathogens in ticks collected in Israel: I. Bacteria and protozoa in Hyalomma aegyptium and Hyalomma dromedarii collected from tortoises and camels

Ticks were collected from 30 Greek tortoise (Testudo graeca), and 10 Arabian camels (dromedary) (Camelus dromedarius) in Israel. All those collected from Greek tortoises belonged to Hyalomma aegyptium, while all specimens collected from the camels belonged to Hyalomma dromedarii. Out of 84 specimens of H. aegyptium, 31 pools were examined by PCR, while from 75 H. dromedarii specimens nine pools were studied. Out of 31 pools of H. aegyptium 26 were positive for pathogens or endosymbiont; 14 for one, 11 for two and one for three pathogens. Out of nine pools prepared from H. dromedarii, seven were positive for pathogens (two for C. burnetii and five for Leishmania infantum). In H. aegyptium, Rickettsia africae, Rickettsia aeschlimannii, Rickettsia endosymbiont, Coxiella burnetii, Hemolivia mauritanica, Babesia microti, Theileria sp., and Leishmania infantum was detected, while in H. dromedarii C. burnetii and L. infantum were found. None of the ticks were positive for Anaplasma/Ehrlichia, Listeria monocytogenes, Bartonella spp., Hepatozoon spp. and Toxoplasma gondii. H Rickettsia endosymbionts, C. burnetii, B. microti, Theileria sp. and L. infantum are reported for the first time in H. aegyptium, and C. burnetii and L. infantum for the first time in H. dromedarii.

Phylogeography of Hyalomma (Euhyalomma) lusitanicum (Acarina, Parasitiformes, Ixodidae) in Andalusia based on mitochondrial cytochrome oxidase I gene

The genetic population structure relationships of Hyalomma (Euhyalomma) lusitanicum in Andalusia (the south of the Iberian Peninsula) were examined using mtDNA sequence data from 887 bp of cytochrome oxidase subunit I (COI) gene. The sequence for the COI region was determined for 84 individuals collected in several localities of Andalusia, and 10 for other localities (i.e., five from Toledo, central Iberian Peninsula, four from Sicily (Italy) and one from Canary Island). Seventeen haplotypes were detected, including 27 polymorphic sites. The number of amino acid substitutions per site from mean diversity calculations for the entire population was 0.017. AMOVA analysis revealed a low gene flow that characterises the genetic population structure of this species in South Iberian Peninsula, with a haplotype diversity (h) value of 0.815. No geographically induced differentiation was observed, and separate evolutionary units were not detected. Our results indicate low genetic diversity across the geographical range of H. lusitanicum tick in Andalusia. Our data do not show any genetic discontinuity between the tick populations studied, including specimens from Canary Island and Sicily (Italy).

A molecular phylogenetic investigation of tick species in Eastern and Southeastern Anatolia

Understanding the local tick species composition is crucial for overcoming the diseases they transmit. A comprehensive survey integrating molecular identification was conducted in the eastern and southeastern parts of Turkey, where tick surveys have previously been neglected. A total of 596 specimens belonging to four tick genera were collected from 27 localities in Turkey during the summers of 2019 and 2020. Seventy-seven representative individuals were chosen for molecular analysis. Nine distinct species, Rhipicephalus bursa, Rhipicephalus turanicus, Rhipicephalus rossicus, Hyalomma asiaticum, Hyalomma excavatum, Hyalomma marginatum, Hyalomma aegyptium, Haemaphysalis sulcata, and Dermacentor marginatus were identified. The presence of R. rossicus was demonstrated for the first time in Turkey. Two lineages of R. turanicus were identified, and representatives of both lineages were recorded. Our Hyalomma phylogenetic tree was consistent with previous findings from Turkey; however, new sympatric areas for Hy. marginatum and Hy. excavatum and Hy. marginatum and Hy. asiaticum were recorded. Two haplotypes (Haemaphysalis sp. and Dermacentor sp.) could not be identified using morphological and molecular methods. In addition to making a valuable contribution to the molecular database of ticks in the Middle East, this study will also stimulate comparative studies on the genetic structure, ecology, and vector competence of different populations of these species in Turkey as well as in other parts of the world.

Prevalence and molecular characterization of ticks and tick-borne pathogens of one-humped camels (Camelus dromedarius) in Nigeria

Background

Ticks are hematophagous arthropods responsible for maintenance and transmission of several pathogens of veterinary and medical importance. Current knowledge on species diversity and pathogens transmitted by ticks infesting camels in Nigeria is limited. Therefore, the aim of this study was to unravel the status of ticks and tick-borne pathogens of camels in Nigeria.

Methods

Blood samples (n = 176) and adult ticks (n = 593) were collected from one-humped camels (Camelus dromedarius) of both sexes in three locations (Kano, Jigawa and Sokoto states) in north-western Nigeria and screened for the presence of Rickettsia spp., Babesia spp., Anaplasma marginale, Anaplasma spp. and Coxiella-like organisms using molecular techniques. All ticks were identified to species level using a combination of morphological and molecular methods.

Results

Ticks comprised the three genera Hyalomma, Amblyomma and Rhipicephalus. Hyalomma dromedarii was the most frequently detected tick species (n = 465; 78.4%) while Amblyomma variegatum (n = 1; 0.2%) and Rhipicephalus evertsi evertsi (n = 1; 0.2%) were less frequent. Other tick species included H. truncatum (n = 87; 14.7%), H. rufipes (n = 19; 3.2%), H. impeltatum (n = 18; 3.0%) and H. impressum (n = 2; 0.3%). The minimum infection rates of tick-borne pathogens in 231 tick pools included Rickettsia aeschlimannii (n = 51; 8.6%); Babesia species, (n = 4; 0.7%) comprising of B. occultans (n = 2), B. caballi (n = 1) and Babesia sp. (n = 1); Coxiella burnetii (n = 17; 2.9%); and endosymbionts in ticks (n = 62; 10.5%). We detected DNA of “Candidatus Anaplasma camelli” in 40.3% of the blood samples of camels. Other tick-borne pathogens including Anaplasma marginale were not detected. Analysis of risk factors associated with both tick infestation and infection with Anaplasma spp. in the blood indicated that age and body condition scores of the camels were significant (P < 0.05) risk factors while gender was not.

Conclusions

This study reports low to moderate prevalence rates of selected tick-borne pathogens associated with camels and their ticks in north-western Nigeria. The presence of zoonotic R. aeschlimannii emphasizes the need for a concerted tick control programme in Nigeria.