Ticks (Acari: Ixodida) infesting humans in the provinces of Kelkit Valley, a Crimean-congo hemorrhagic fever endemic region in Turkey

Ticks are mandatory blood feeding ectoparasites leading transmission of various tick-borne pathogens to human and animals. Since 2002, thousands of human tick bites and numerous Crimean-Congo Hemorrhagic Fever cases have been reported in several provinces in the Kelkit Valley region in Turkey. Despite increased cases of tick bites and tick-borne diseases, no taxonomic information is available about the tick species infesting humans in the region. In the present study, a tick survey on humans was performed to determine the species composition of ticks infesting humans in several provinces of Kelkit Valley. In the survey, 1,460 ticks (721 males, 516 females and 223 nymphs) were collected from tick-infested humans. A total of 19 tick species have been found on humans in the region, including 7 Hyalomma, 2 Argas, 2 Haemaphysalis, 2 Ixodes, Dermacentor and 3 Rhipicephalus species. Infestation of Dermacentor reticulatus on humans was documented for the first time in Turkey.     

Ixodid ticks (Acari: Ixodidae) infesting humans in Tokat Province of Turkey: species diversity and seasonal activity

Ixodid ticks (Acari: Ixodidae) are the major vectors of pathogens threatening animal and human health. Tokat Province, Turkey, is a suitable habitat for extended tick activity with its moderate climate and vegetation. In the present study, we surveyed humans visiting health centers to determine the species diversity, geographical distribution, and seasonal activity of ixodid ticks infesting them. Out of 5,999 adult ticks collected from humans from April to September, 2008, 800 ticks were identified to species, while the remaining were identified to genus according to their distinct morphological characteristics. Hyalomma marginatum, Hyalomma detritum, Rhipicephalus bursa, Rhipicephalus (Boophilus) annulatus, Haemaphysalis punctata, Dermacentor marginatus, and Ixodes laguri were the most prevalent tick species among 24 ixodid tick species infesting humans in the region. One of these tick species, Hyalomma isacii was identified as a new record for the ixodid tick fauna of Turkey. Hyalomma species were the most abundant in summer, while Dermacentor and Ixodes species displayed the lowest frequency. Hyalomma aegyptium infestation was very common on humans in the province. Results indicated that a variety of ixodid tick species infest humans depending on the season in the target area. It is possible that a variety of ixodid tick species may contribute to the spread of tick‐borne diseases such as Crimean‐Congo haemorrhagic fever virus (CCHFV), which is endemic in the region.     

Ticks Feeding on Humans: A Review of Records on Human-Biting Ixodoidea with Special Reference to Pathogen Transmission

In this article, literature records of argasid and ixodid ticks feeding on humans worldwide are provided in view of increased awareness of risks associated with tick bites. Ticks can cause paralyses, toxicoses, allergic reactions and are vectors of a broad range of viral, rickettsial, bacterial and protozoan pathogens. Approximately 12 argasid species (Argas and Ornithodos) are frequently found attached to humans who intrude into tick-infested caves and burrows. Over 20 ixodid tick species are often found on humans exposed to infested vegetation: four of these are Amblyomma species, 7 Dermacentor spp., 3 Haemaphysalis spp., 2 Hyalomma spp. and 6 Ixodes species. Personal protection methods, such as repellents and acaricide-impregnated clothing are advised to minimize contact with infected ticks. Acaricidal control of ixodid ticks is impractical because of their wide distribution in forested areas, but houses infested with soft ticks can be sprayed with acaricidal formulations. Attached ticks should be removed without delay. The best way is to grasp the tick as close to the skin as possible with fine tweezers and pull firmly and steadily without twisting. Finally, despite the fact that most people who are bitten destroy the offending tick in disgust, it is recommended that they preserve specimens in ethanol for taxonomic identification and detection of pathogens by molecular methods.     

Tick survey and detection of Crimean-Congo hemorrhagic fever virus in tick species from a non-endemic area, South Marmara region, Turkey

Crimean-Congo hemorrhagic fever (CCHF) is an increasing health concern in Turkey since 2002. There were also some recent human cases from the South Marmara region of Turkey; thus, a tick survey was performed, and possible vector tick species for the CCHF virus were determined in the region. A total of 740 adult ticks were collected from infested livestock from five locations: Çanakkale-Biga, Bursa-Orhaneli, Bursa-Keles, Bal?kesir and Bilecik. Total of 11 tick species from the genera Hyalomma, Rhipicephalus, Dermacentor, Ixodes and Haemaphysalis were identified. Rhipicephalus ticks were dominant in the region; the most frequently observed tick species was R. turanicus, (53.1 %), and only 15.4 % of the identified ticks were H. marginatum. The occurrence of H. rufipes infestation in the region fort he first time. A total of 73 pools of adult ticks were tested with both an antigen-detecting ELISA and RT real-time PCR (RT rt PCR). The presence of the CCHF virus was demonstrated in 9 (12.3 %) of the tested tick pools. Although seven of the tick pools were positive for the CCHF virus with both of the methods, one pool was positive only with RT rt PCR and the other pool was only positive with the ELISA. Positive results were obtained from ticks collected from cattle, sheep and goats from two locations, Bursa-Orhaneli and Bilecik. The CCHF virus was detected in R. turanicus (n = 3), R. bursa (n = 2), H. marginatum (n = 2) and D. marginatus (n = 2) ticks. The results of this study confirm the presence of the CCHF virus and present preliminary data on the vector tick species in the southern Marmara region of Turkey.     

The medical and veterinary role of Ornithodoros erraticus complex ticks (Acari: Ixodida) on the Iberian Peninsula

Argasid ticks of the Ornithodoros erraticus complex are associated with traditional pig‐farming practices on the Iberian Peninsula and are also found elsewhere in North Africa, West Africa, and western Asia. The ticks associated with pig farming on the Iberian Peninsula are the only biological vectors of African swine fever virus (ASFV) known to occur in Europe, and their ecology makes them an extremely effective reservoir of both ASFV and the Borrelia species which cause tick‐borne relapsing fever (TBRF) in humans. The recent reappearance of ASFV in the European Union, coupled with evidence that Portuguese tick populations continue to harbor Borrelia despite a lack of confirmed human infections, suggest that these populations merit closer attention. In Portugal, a series of surveys over the last twenty‐five years indicates that the number of farm sites with tick infestations has declined and suggest that populations are sensitive to changes in farm management, particularly the use of modern pig housing. Various technologies have been suggested for the control of farm‐associated Ornithodoros ticks and related species but, in our opinion, farm management changes are still the most effective strategy for population control. Furthermore, we suggest that this species could probably be eradicated from Iberian pig farms.     

Modelling the transmission dynamics of Theileria annulata: model structure and validation for the Turkish context

A mathematical model that describes the transmission dynamics of Theileria annulata is proposed that consists of 2 host components: the Hyalomma tick population and a compartmental model of T. annulata infection in the cattle population. The model was parameterized using data describing tick infestation and the infection status of cattle in Turkey from 2006 to 2008. The tick attachment rates are highly seasonal and because of the temporal separation of infectious and susceptible ticks virtually all ticks are infected by carrier cattle, so that annual peaks of disease in cattle do not impact on infection in the Hyalomma tick population. The impact of intervention measures that target the tick population both on the host and in the environment and their impact on the transmission of T. annulata were investigated. Interventions that have a limited 'one-off' impact and interventions that have a more permanent impact were both considered. The results from the model show the importance of targeting ticks during the period when they have left their first host as nymphs but have yet to feed on their second host.     

Ticks on snakes: The ecological correlates of ectoparasite infection in free‐ranging snakes in tropical Australia

Parasites profoundly influence the lives of their hosts, yet the dynamics of host–parasite interactions are poorly understood – especially in reptiles. We examined the ecological correlates of parasitism by ixodid ticks in an assemblage of 10 snake species in tropical Australia. In total, we recorded 3803 ticks on 1841 individual snakes of six species (no ticks were found on the other species). Molecular analyses confirmed the tropical reptile tick (Amblyomma fimbriatum: Ixodidae) to be the most common snake tick at our study site, with inter‐ and intraspecific variation in tick prevalence and intensity. Tick attachment sites were random on most snake species, but both male and female ticks congregated on the heads of the colubrid snake Boiga irregularis and the python Simalia amethistina. In these same species, tick loads were higher on snakes captured in woodland than in rainforest. Females of two python species (Aspidites melanocephalus and S. amethistina) had higher tick loads than did males. In B. irregularis, individuals captured in the dry season had higher tick loads than those captured in the wet season. In most parasitized snake species, larger individuals had greater tick loads. Data from snake recaptures confirmed individual tick burdens frequently varied, with little correlation between tick loads on the same snake at successive captures (except for B. irregularis). Finally, tick intensity was not correlated with (and thus, presumably did not influence) the body condition of any snake species in our study. Use of specific types of refuge sites may strongly influence tick loads on snakes in this system.     

Ixodes philipi (Acari: Ixodidae): phylogenetic status inferred from mitochondrial cytochrome oxidase subunit I gene sequence comparison

Ixodes philipi ticks were collected from the nest burrows of streaked shearwaters, Calonectris luecomelas, on 3 different islands of Japan (Awashima: 38 degrees 45'N, 139 degrees 24'E; Mikurajima: 33 degrees 52'N, 139 degrees 36'E; and Omorijima: 36 degrees 8'N, 133 degrees 10'E). The mitochondrial cytochrome oxidase subunit I (COI) gene sequence was determined for each tick. The COI sequences of 9 other ixodid tick species also were determined, and they were used for taxonomic positioning of I. philipi. A metastriata tick, Amblyomma triguttatum, was used as an outgroup reference for the analysis. Phylogenetic examination indicated that the I. philipi ticks are on the branch with Ixodes turdus and Ixodes acutitarsus weakly, and the bootstrap value of this branching was low. Three different analyses, maximum parsimony, genetic distance, and maximum likelihood, support this conclusion. To further refine this analysis, 2761 base pairs (bp) of sequence, which included the genes for tRNA(Met), NADH dehydrogenase subunit 2 (ND2), tRNA(Trp), tRNA(Cys), tRNA(Tyr), and COI, were determined and compared for 6 I. philipi ticks from the 3 different collection sites. Although a base substitution (T to C in the ND2 gene for an Awashima tick) and 2 transitions (G to A in the COI gene for 1 Omorijima tick) have occurred, the overall sequences were highly conserved. Preserved mitochondrial sequences in the ticks from 3 widely separated locations suggest the possibility of gene flow, which was probably accomplished by migratory seabirds.     

Ticks (Acari: Ixodoidea) in China: Geographical distribution,host diversity,and specificity

Ticks are obligate blood‐sucking ectoparasites, which not only directly damage through bites but also transmit many pathogens. China has a high diversity of tick species, 125 species have been reported, including 111 hard tick and 14 soft tick species. Many of the ticks are important vectors of pathogens, resulting in zoonoses. The dynamics of ticks are affected by both the host and habitat environment. However, systematic studies on the geographical distribution, host diversity, and specificity of ticks are limited in China. To achieve this goal, the relevant available data were summarized and analyzed in this study. Ticks are distributed in all parts of China and Xinjiang has the most records of ticks. The distribution of ticks in adjacent areas is similar, indicating that the habitat environment affects their distribution. Most ticks are widely distributed, whereas some species are endemic to their distributed regions. Ticks are parasitic on mammals, birds, and reptiles, of which mammals are the main host species. Overall, most ticks parasitize different hosts, only a few ticks have strict host specificity, such as ticks that are specifically parasitic on reptiles and bats. In addition, environmental changes and control efforts also influence the dynamics of ticks. These results can better reveal tick biological traits and are valuable for tick control.     

Nuttalliella namaqua: a living fossil and closest relative to the ancestral tick lineage: implications for the evolution of blood-feeding in ticks

Ticks are monophyletic and composed of the hard (Ixodidae) and soft (Argasidae) tick families, as well as the Nuttalliellidae, a family with a single species, Nuttalliella namaqua. Significant biological differences in lifestyle strategies for hard and soft ticks suggest that various blood-feeding adaptations occurred after their divergence. The phylogenetic relationships between the tick families have not yet been resolved due to the lack of molecular data for N. namaqua. This tick possesses a pseudo-scutum and apical gnathostoma as observed for ixodids, has a leathery cuticle similar to argasids and has been considered the evolutionary missing link between the two families. Little knowledge exists with regard to its feeding biology or host preferences. Data on its biology and systematic relationship to the other tick families could therefore be crucial in understanding the evolution of blood-feeding behaviour in ticks. Live specimens were collected and blood meal analysis showed the presence of DNA for girdled lizards from the Cordylid family. Feeding of ticks on lizards showed that engorgement occurred rapidly, similar to argasids, but that blood meal concentration occurs via malpighian excretion of water. Phylogenetic analysis of the 18S nuclear and 16S mitochondrial genes indicate that N. namaqua grouped basal to the main tick families. The data supports the monophyly of all tick families and suggests the evolution of argasid-like blood-feeding behaviour in the ancestral tick lineage. Based on the data and considerations from literature we propose an origin for ticks in the Karoo basin of Gondwanaland during the late Permian. The nuttalliellid family almost became extinct during the End Permian event, leaving N. namaqua as the closest living relative to the ancestral tick lineage and the evolutionary missing link between the tick families.     

The tick fauna of Sulawesi, Indonesia (Acari: Ixodoidea: Argasidae and Ixodidae)

Twenty-six species of ticks are reported from the island of Sulawesi (Celebes), Indonesia. These include two species of soft ticks (Argasidae), Carios batuensis and C. vespertilionis, and the following 24 species of hard ticks (Ixodidae): Amblyomma babirussae, A. breviscutatum, A. cordiferum, A. fimbriatum, A. helvolum, A. testudinarium, A. trimaculatum, A. varanense, Dermacentor atrosignatus, D. steini, Haemaphysalis celebensis, H. hystricis, H. kadarsani, H. papuana, H. psalistos, H. renschi, H. toxopei, H. wellingtoni, Ixodes cordifer, I. granulatus, Rhipicephalus haemaphysaloides, R. (Boophilus) microplus, R. pilans and R. sanguineus. This represents an almost three-fold increase in the number of tick species recorded (9) from Sulawesi since the last available list in 1950. The tick records reported herein represent a culmination of data from specimens in the U.S. National Tick Collection, new records of ticks from endemic tarsiers and associated vertebrates, and literature reviews. Collectively, the tick fauna of Sulawesi shows most affinities with the fauna of southeast Asia but there are distinct faunal elements that show relationships with other Indonesian islands, the Philippines or Australasia, as well as a few tick species with widespread geographical distributions. Some ticks known from Sulawesi have known or potential medical-veterinary significance. These include R. (B.) microplus which is a significant pest of cattle and a vector of the agents of bovine anaplasmosis, I. granulatus which is a vector of Langat virus and Lyme disease spirochetes and has been shown to harbor pathogenic rickettsiae in other parts of its range, and R. sanguineus which is a globally widespread ectoparasite of canines and a vector of canine pathogens and parasites.     

A Rickettsiella bacterium from the hard tick, Ixodes woodi: molecular taxonomy combining multilocus sequence typing (MLST) with significance testing

Hard ticks (Acari: Ixodidae) are known to harbour intracellular bacteria from several phylogenetic groups that can develop both mutualistic and pathogenic relationships to the host. This is of particular importance for public health as tick derived bacteria can potentially be transmitted to mammals, including humans, where e.g. Rickettsia or Coxiella act as severe pathogens. Exact molecular taxonomic identification of tick associated prokaryotes is a necessary prerequisite of the investigation of their relationship to both the tick and possible vertebrate hosts. Previously, an intracellular bacterium had been isolated from a monosexual, parthenogenetically reproducing laboratory colony of females of the hard tick, Ixodes woodi Bishopp, and had preliminarily been characterized as a "Rickettsiella-related bacterium". In the present molecular taxonomic study that is based on phylogenetic reconstruction from both 16 S ribosomal RNA and protein-encoding marker sequences complemented with likelihood-based significance testing, the bacterium from I. woodi has been identified as a strain of the taxonomic species Rickettsiella grylli. It is the first time that a multilocus sequence typing (MLST) approach based on a four genes comprising MLST scheme has been implemented in order to classify a Rickettsiella-like bacterium to this species. The study demonstrated that MLST holds potential for a better resolution of phylogenetic relationships within the genus Rickettsiella, but requires sequence determination from further Rickettsiella-like bacteria in order to complete the current still fragmentary picture of Rickettsiella systematics.     

Occurrence patterns of Afrotropical ticks (Acari: Ixodidae) in the climate space are not correlated with their taxonomic relationships

Foci of tick species occur at large spatial scales. They are intrinsically difficult to detect because the effect of geographical factors affecting conceptual influence of climate gradients. Here we use a large dataset of occurrences of ticks in the Afrotropical region to outline the main associations of those tick species with the climate space. Using a principal components reduction of monthly temperature and rainfall values over the Afrotropical region, we describe and compare the climate spaces of ticks in a gridded climate space. The dendrogram of distances among taxa according to occurrences in the climate niche is used to draw functional groups, or clusters of species with similar occurrences in the climate space, as different from morphologically derived (taxonomical) groups. We aim to further define the drivers of species richness and endemism at such a grid as well as niche similarities (climate space overlap) among species. Groups of species, as defined from morphological traits alone, are uncorrelated with functional clusters. Taxonomically related species occur separately in the climate gradients. Species belonging to the same functional group share more niche among them than with species in other functional groups. However, niche equivalency is also low for species within the same taxonomic cluster. Thus, taxa evolving from the same lineage tend to maximize the occupancy of the climate space and avoid overlaps with other species of the same taxonomic group. Richness values are drawn across the gradient of seasonal variation of temperature, higher values observed in a portion of the climate space with low thermal seasonality. Richness and endemism values are weakly correlated with mean values of temperature and rainfall. The most parsimonious explanation for the different taxonomic groups that exhibit common patterns of climate space subdivision is that they have a shared biogeographic history acting over a group of ancestrally co-distributed organisms.     

Experimental evaluation of birds as disseminators of the cosmopolitan tick Rhipicephalus sanguineus (Acari: Ixodidae)

Rhipicephalus sanguineus is believed to be the most widespread tick species of the world and its dissemination seems to rely on the diffusion of its main host, the dog. Empirical observations indicate that several bird species in urban areas regularly steal dog food. Such circumstances create a chance for R. sanguineus ticks to climb on birds and carry ticks to another site. In this work we evaluated experimentally the likelihood of birds (chicks) to either feed and/or carry R. sanguineus ticks from an infested site to another and to infest a host (rabbit) in the new location. Chicks were not suitable hosts for R. sanguineus ticks. Not a single adult tick engorged on chicks, yield as well as weight of engorged larvae and nymphs were very low and feeding period of these ticks was very long. However, a few larvae and, chiefly, nymphs were delivered to a new location either mechanically or after attachment and engorging total or partially on chicks. A few of these ticks fed successfully on rabbits. Further evidence on the capacity of birds to introduce R. sanguineus into non-infested dog settings should be provided by systematic examination of birds from urban areas, close to tick infested households.     

The role of host behaviour in tick-host interactions: a domestic host-paralysis tick model

The aim of this study was to quantify the infestation densities of Karoo and brown paralysis ticks on sheep and goats and explain it in terms of the etho-ecology of these ticks and their domestic hosts. The Karoo paralysis tick usually quests from a vantage point on the vegetation whereas the brown paralysis tick displays an appetence response from the ground and mainly engages hosts that are prostrate. Both tick species are confined chiefly to hilly areas. Temporal differences in the infestation densities of the hosts within and between tick species were evident. These differences were related to disparities in the spatial distribution of the hosts, their activity patterns and the specific appetence responses of the two tick species. Differential climatological conditions affected the quality of forage in areas with a varied topography and the feeding preferences of hosts influenced tick-host sympatry and hence infestation densities.     

蜱类分类系统的变更

随着分子生物学技术在蜱类研究中的应用,及对蜱类系统发生的深入研究,蜱的分类及命名发生了很大变更。而中国在这一领域的研究还停留在20世纪90年代,分类系统过时。文章对中国曾经采用的蜱类分类系统与现今世界上普遍认可的分类系统进行了详细比较,以期引起注意,从而促进蜱类系统学及其他研究领域的发展。     

Detection of Wolbachia in the tick Ixodes ricinus is due to the presence of the hymenoptera endoparasitoid Ixodiphagus hookeri

The identification of micro-organisms carried by ticks is an important issue for human and animal health. In addition to their role as pathogen vectors, ticks are also the hosts for symbiotic bacteria whose impact on tick biology is poorly known. Among these, the bacterium Wolbachia pipientis has already been reported associated with Ixodes ricinus and other tick species. However, the origins of Wolbachia in ticks and their consequences on tick biology (known to be very diverse in invertebrates, ranging from nutritional symbionts in nematodes to reproductive manipulators in insects) are unknown. Here we report that the endoparasitoid wasp Ixodiphagus hookeri (Hymenoptera, Chalcidoidea, Encyrtidae)--strictly associated with ticks for their development--infested at almost 100% prevalence by a W. pipientis strain belonging to a Wolbachia supergroup that has already been reported as associated with other hymenopteran parasitoids. In a natural population of I. ricinus that suffers high parasitism rates due to I. hookeri, we used specific PCR primers for both hymenopteran and W. pipientis gene fragments to show that all unfed tick nymphs parasitized by I. hookeri also harbored Wolbachia, while unparasitized ticks were Wolbachia-free. We demonstrated experimentally that unfed nymphs obtained from larvae exposed to I. hookeri while gorging on their vertebrate host also harbor Wolbachia. We hypothesize that previous studies that have reported W. pipientis in ticks are due to the cryptic presence of the endoparasitoid wasp I. hookeri. This association has remained hidden until now because parasitoids within ticks cannot be detected until engorgement of the nymphs brings the wasp eggs out of diapause. Finally, we discuss the consequences of this finding for our understanding of the tick microbiome, and their possible role in horizontal gene transfer among pathogenic and symbiotic bacteria.     

Effect of deer density on tick infestation of rodents and the hazard of tick-borne encephalitis. II: population and infection models

Tick-borne encephalitis is an emerging vector-borne zoonotic disease reported in several European and Asiatic countries with complex transmission routes that involve various vertebrate host species other than a tick vector. Understanding and quantifying the contribution of the different hosts involved in the TBE virus cycle is crucial in estimating the threshold conditions for virus emergence and spread. Some hosts, such as rodents, act both as feeding hosts for ticks and reservoirs of the infection. Other species, such as deer, provide important sources of blood for feeding ticks but they do not support TBE virus transmission, acting instead as dead-end (i.e., incompetent) hosts. Here, we introduce an eco-epidemiological model to explore the dynamics of tick populations and TBE virus infection in relation to the density of two key hosts. In particular, our aim is to validate and interpret in a robust theoretical framework the empirical findings regarding the effect of deer density on tick infestation on rodents and thus TBE virus occurrence from selected European foci. Model results show hump-shaped relationships between deer density and both feeding ticks on rodents and the basic reproduction number for TBE virus. This suggests that deer may act as tick amplifiers, but may also divert tick bites from competent hosts, thus diluting pathogen transmission. However, our model shows that the mechanism responsible for the dilution effect is more complex than the simple reduction of tick burden on competent hosts. Indeed, while the number of feeding ticks on rodents may increase with deer density, the proportion of blood meals on competent compared with incompetent hosts may decrease, triggering a decline in infection. As a consequence, using simply the number of ticks per rodent as a predictor of TBE transmission potential could be misleading if competent hosts share habitats with incompetent hosts.     

Ticks (Acari: Ixodidae) infesting the Arabian Camel (Camelus dromedarius) in the Sinai,Egypt with a note on the acaricidal efficacy of Ivermectin

In this study, tick burdens on camels (Camelus dromedarius) were determined in the vicinity of the St. Catherine monastery, Sinai, Egypt. In total 2,545 ticks (1,491 adults and 1,054 nymphs) were collected and identified. Mean tick burdens were relatively heavy and the range in number of ticks per camel was very broad (6–173). Hyalomma dromedarii was the predominant tick species and accounted for 95.6% of the adult ticks. Other ticks found were H. marginatum subspp. and H. anatolicum excavatum. All nymphs collected were Hyalomma spp.In addition, the effect of ivermectin (Ivomec MSD AGVET) on tick burdens, when given subcutaneously at 0.2 mg/kg¹, was evaluated in nine camels in the date-palm plantation of Kibbutz Yahel in the Arava valley, Israel. Initial tick burdens on these camels (half-body tick counts) ranged from 20–105 ticks per camel. Seven camels from the same herd with half-body tick counts ranging from 40–107 ticks per camel were not treated and served as a control group. Ivermectin was not effective against Hyalomma tick infestation in camels under these conditions.