On the spermatophore of ixodid ticks

Structure and formation of the spermatophore and the extrusion of its contents in ixodid ticks were studied. The structure of the ectospermatophore resembles that of argasid ticks, whereas that of the endospermatophore differs completely; it is composed of several organelles which are absent in argasids.The chemical nature of the components of the spermatophore was studied by histochemical methods. The male forms the spermatophore by ejaculating the components in a definite order. The components of the ectospermatophore are deposited one into another—while those of the endospermatophore one on top of the other and are linked together in a chain. The last component to be ejected is a plug that closes the endospermatophore.During extrusion of the endospermatophore all of the components burst out of the ectospermatophore. The endospermatophore sheath evaginates and forms the capsule into which the sperm is inserted. Each capsule has two tube-like appendices.     

Ethanol inactivation of orthonairoviruses in ixodid ticks

Experimental and Applied Acarology - Ixodid ticks represent vectors and reservoirs for a broad range of zoonotic pathogens. Collected ticks from field studies are therefore usually stored in...     

Salivary glands in ixodid ticks: control and mechanism of secretion

The salivary glands are vital to the biological success of ixodid ticks and the major route for pathogen transmission. Important functions include the absorption of water vapor from unsaturated air by free-living ticks, excretion of excess fluid for blood meal concentration, and the secretion of bioactive protein and lipid compounds during tick feeding. Fluid secretion is controlled by nerves. Dopamine is the neurotransmitter at the neuroeffector junction regulating secretion via adenylate cyclase and an increase in cellular cAMP. Dopamine also affects the release of arachidonic acid which is subsequently converted to prostaglandins. Prostaglandin E(2) (PGE(2)) is secreted at extremely high levels into tick saliva for export to the host where it impacts the host physiology. Additionally, PGE(2) has an autocrine or paracrine role within the salivary gland itself where it interacts with a PGE(2) receptor to induce secretion (exocytosis) of bioactive saliva proteins via a phosphoinositide signalling pathway and an increase in cellular Ca(2+). Regulation of fluid secretion has been extensively studied, but little is known about the mechanism of fluid secretion. Continuing advances in tick salivary gland physiology will be made as key regulatory and secretory gland proteins are purified and/or their genes cloned and sequenced.     

Variation in genome size of argasid and ixodid ticks

The suborder Ixodida includes many tick species of medical and veterinary importance, but little is known about the genomic characteristics of these ticks. We report the first study to determine genome size in two species of Argasidae (soft ticks) and seven species of Ixodidae (hard ticks) using flow cytometry analysis of fluorescent stained nuclei. Our results indicate a large haploid genome size (1C>1000 Mbp) for all Ixodida with a mean of 1281 Mbp (1.31+/-0.07 pg) for the Argasidae and 2671 Mbp (2.73+/-0.04 pg) for the Ixodidae. The haploid genome size of Ixodes scapularis was determined to be 2262 Mbp. We observed inter- and intra-familial variation in genome size as well as variation between strains of the same species. We explore the implications of these results for tick genome evolution and tick genomics research.     

Distribution and phenology of ixodid ticks in southern Zambia

Distribution data for epidemiologically important ticks (Acari: Ixodidae) in the Southern Province of Zambia, one of the main cattle areas of the country, are presented. Boophilus microplus (Canestrini) was not recorded in southern Zambia, whereas Boophilus decoloratus (Koch) is present throughout the area. New distribution patterns for less economically important ixodid ticks are also discussed. Southern Zambia is a transition zone because it is the most northern area in Africa where mixed Rhipicephalus appendiculatus Neumann and Rhipicephalus zambeziensis Walker, Norval & Corwin populations were reported. Although a second generation of adult R. appendiculatus/R. zamnbeziensis was encountered, simulations indicated that this phenomenon is very rare in southern Zambia, mainly because of the colder temperatures during the early dry season and lower rainfall. These simulations were supported by a development trial under experimental conditions. Tick body size measurements showed that southern Zambian ticks are larger than eastern Zambian R. appendiculatus. It is hypothesized that body size is related to diapausing intensity in this species. The epidemiological consequences are that a different approach to control Theileria parva (Theiler) (Piroplasmida: Theileriidae) and other tick-borne diseases is needed in southern Zambia, compared to the one adopted in eastern Zambia.     

The coevolution of ixodid ticks and terrestrial vertebrates

Paleontologic and zoogeographic data speak in favour of Mesozoic origin of ixodid ticks. The absence of strict restrictions for the feeding on unusual species of hosts has caused the domination of polyphagy and oligophagy over monophagy among ixodid ticks. The same peculiarities of ixodid ecology are responsible for a restricted part or absence of phylogenetic parallelism with hosts in their evolution. Primary food relations with reptiles are, apparently, preserved only in the genus Aponomma and in many species of Amblyomma while hosts for most species of other genera are mammals and, to a lesser extent, birds. The number of potential hosts in these species can be much greater than that of real ones. Restrictions in the distribution of some species are connected rather with direct effect of unfavourable environmental factors on their nonparasitic stages of the life cycle than with the absence of suitable hosts. During the evolution of natural landscapes and at a shorter stages under the influence of successions or anthropogenic factors ixodids easily adapt themselves to feeding on new species of hosts. So the differentiation of primary and secondary hosts of these parasites is rather difficult.     

Neural control of salivary glands in ixodid ticks

Studies of tick salivary glands (SGs) and their components have produced a number of interesting discoveries over the last four decades. However, the precise neural and physiological mechanisms controlling SG secretion remain enigmatic. Major studies of SG control have identified and characterized many pharmacological and biological compounds that activate salivary secretion, including dopamine (DA), octopamine, γ-aminobutyric acid (GABA), ergot alkaloids, pilocarpine (PC), and their pharmacological relatives. Specifically, DA has shown the most robust activities in various tick species, and its effect on downstream actions in the SGs has been extensively studied. Our recent work on a SG dopamine receptor has aided new interpretations of previous pharmacological studies and provided new concepts for SG control mechanisms. Furthermore, our recent studies have suggested that multiple neuropeptides are involved in SG control. Myoinhibitory peptide (MIP) and SIFamide have been identified in the neural projections reaching the basal cells of acini types II and III. Pigment-dispersing factor (PDF)-immunoreactive neural projections reach type II acini, and RFamide- and tachykinin-immunoreactive projections reach the SG ducts, but the chemical nature of the latter three immunoreactive substances are unidentified yet. Here, we briefly review previous pharmacological studies and provide a revised summary of SG control mechanisms in ticks.     

Prevalence of ixodid ticks on cattle in Mazandaran province, Iran

A survey was carried out to investigate the prevalence of hard tick species (Acari: Ixodidae) on cattle in Mazandaran province, Iran. A total of 953 ticks were collected from 86 infested cattle during activating seasons of ticks during 2004-2005. Nine species were identified: Boophilus annulatus (51.3%), Rhipicephalus bursa (16.8%), Haemaphysalis punctata (6.3%), Ixodes ricinus (6.8%), Hyalomma marginatum (12.5%), Hyalomma anatolicum excavatum (5.2%), Hyalomma asiaticum (0.6%), Hyalomma detritum (0.2 %), and Dermacentor spp. (0.1%). The results show that Boophilus annulatus, Rhipicephalus bursa, and Hyalomma species are dominant tick species in the surveyed area.     

Shifts in the distribution of ixodid ticks parasitizing cattle in Zimbabwe

In an attempt to update information on the ecological distribution of ixodid ticks (Ixodida: Ixodidae) in Zimbabwe, a cross‐sectional survey was carried out between September 2013 and May 2015 at 322 dip tanks. A total of 15 tick species were collected, namely: Amblyomma hebraeum Koch (65.2%, n = 210/322), Amblyomma variegatum Fabricius (14.9%, n = 48/322), Hyalomma rufipes Koch (62.4%, n = 201/322), Hyalomma truncatum Koch (37.9%, n = 122/322), Rhipicephalus appendiculatus Neumann (60.6%, n = 195/322), Rhipicephalus compositus Neumann (0.3%, n = 1/322,), Rhipicephalus decoloratus Koch (61.8%, n = 199/322), Rhipicephalus evertsi evertsi Neumann (65.2%, n = 210/322), Rhipicephalus lunulatus Neumann (4%, n = 13/322), Rhipicephalus microplus Canestrini (32%, n = 103/322), Rhipicephalus near punctatus Walker and Horak (7.1%, n = 23/322), Rhipicephalus simus Koch (5.6%, n = 18/322) and Rhipicephalus cf. turanicus Pomerantsev (3.4%, n = 11/322). Compared with previous surveys, changes in the distribution of A. hebraeum, A. variegatum and R. microplus were recorded. The distributions of other tick species have largely remained unchanged. Factors which might have influenced these changes and the possible impacts on the epidemiology of tick‐borne diseases are discussed.     

Observations on the ixodid ticks associated with domestic ungulate animals in Jordan

Abstract

Fourteen species and subspecies of ixodid ticks, representing four genera, were collected from native sheep, goats, camels and cattle in Jordan. Haemaphysalis otophila was the most common species (48.1%) with Rhipicephalus sanguineus (15.3%), Boophilus kohlsi (14.4%) and Haemaphysalis sulcatus (11.6%) representing other common species among the 9,545 specimens examined.     

Preliminary studies on virus and spirochete accumulation in the cement plug of ixodid ticks

We provide evidence that tick-borne encephalitis virus and Borrelia burgdorferi s.l. are accumulated in the cement plug in the host skin within the first few hours after tick attachment. Extirpation of the tick without the cement plug, even very soon after the attachment, did not prevent the transmission by Ixodes ricinus, Ixodes persulcatus or Dermacentor reticulatus to mice. This was within 1 hour in the case of the TBE virus and after 20–22 h of attachment, in the case of Borrelia and I. persulcatus. The epidemiological significance of these findings is discussed.     

A review of the types of parasite-host relations in ixodid ticks

In the first type of mutual relationships the ixodid ticks expose an evident pathogenicity to vertebrate hosts (tick toxicoses) and in the second type the hosts expose a resistance on a base of organism immune system activisation in a response to blood sucking. In the third type of relationships an interaction between the ticks and hosts have a dynamic character (tolerability of host). The first type of relationships leading to a selective elimination of hosts according to our opinion means a comparatively youth of relationships. The third type represent ancient and long term relationships. The second type probably having been widely spread in a historical past occupies an intermediate position. Depending upon areal the ticks of the same type expose different degree of the pathogenicity. Even an acquired resistance of the host does exist in natural conditions, it is a transient phenomenon.     

Phenology of ixodid ticks of the genus Dermacentor in the Central Ciscaucasia

In Stavropol Territory, ixodid ticks of the genus Dermacentor are represented by three species: D. marginatus, D. reticulatus, and D. niveus. D. marginatus is the most widespread species, constituting 14.8% of all the ticks in the region; D. reticulatus and D. niveus are found less frequently, constituting 2.8% and 0.01%, respectively. D. marginatus and D. reticulatus are spread mostly in the forest-steppe and steppe zones of Stavropol Territory. D. niveus is represented by solitary specimens in arid and semidesert zones. The main hosts of adult D. marginatus in Stavropol Territory are cattle (88.4%) and sheep and goats (5.3%). The hosts of D. reticulatus are also cattle (72.3%) and sheep and goats (4%). D. marginatus activates at an average monthly temperature of +2.07°C and average monthly rainfall of 47.2 mm. The peak of parasitizing on hosts was observed at an average monthly temperature of +7.8°C and average monthly rainfall of 56.2 mm. The autumnal activation was recorded at an average monthly temperature of +15.3°C and average monthly rainfall of 58.2 mm.     

The action of carbon dioxide gas in high concentrations on ixodid ticks

The ticks Ixodes persulcatus, Dermacentor reticulatus, D. marginatus were affected by 50, 70, 80 and 90% CO2 at 18 to 26 degrees. The higher the gas concentration and the lower the temperature, the quicker and the deeper was anesthesia. Additional tests have shown that response to CO2 depends on the water balance level determining the position of atrial valves. The response of some individuals to CO2 can change depending on the tick state during the experiment.     

Influence of biotope on the distribution and peak activity of questing ixodid ticks in Hungary

Abstract In order to update the occurrence of hard tick species in Hungary, 3442 questing ticks were collected from the vegetation by the dragging/flagging method in 37 different places in the country, between March and June of 2007. Ixodes ricinus (L.) turned out to be ubiquitous. Dermacentor marginatus (Schulzer) was absent from sampling sites in the southwestern part of the country, but in most places was concomitant and contemporaneous with Dermacentor reticulatus (Fabricius). These two species, as well as I. ricinus, occurred up to an altitude of 900–1000 m a.s.l. Haemaphysalis inermis (Birula) and Haemaphysalis concinna (Koch) were not confined to any parts of the country, unlike Haemaphysalis punctata (Canestrini & Fanzago) which was found in only one region. The local prevalence of the latter species was also significantly lower than those of the former two in the same habitat (fringes of meadows, paths in forests). Dermacentor spp. and H. inermis were represented only by adults. In most species females were collected more frequently than males, except in H. concinna and H. punctata. Temporal differences between the peak activity of I. ricinus and Dermacentor spp. on dry pastures appeared to equalize on meadows in mountain forests, and a similar phenomenon was observed for the three Haemaphysalis spp. when collected along forest paths with fresh, green vegetation.     

Ticks in the ecotone: the impact of agri-environment field margins on the presence and intensity of Ixodes ricinus ticks (Acari: Ixodidae) in farmland in southern England

The present study aimed to assess whether agri-environment field margins provide a habitat for the sheep/deer tick Ixodes ricinus. Field studies were conducted in arable farmland in southern England in both extant and newly constructed field margins. The presence and intensity (i.e. the mean number of nymphs per transect, excluding zeros) of questing nymphs and adult I. ricinus were compared between field margins with three adjacent habitats: woodland, hedgerow and arable land. The presence and intensity of ticks within a field margin was also compared between three ecozones: the ecotone, the margin and the crop. It was found that field margins do support I. ricinus, although the intensity of ticks was associated with field margins with adjacent woodland, with a higher tick intensity along the ecotonal ecozone, compared with the rest of the margin or the crop edge. The presence of a hedge also increased the likelihood of finding questing nymphs in a field margin compared with a margin adjacent to arable land. This effect, however, was less pronounced than in field margins with adjacent woodland. The provision of footpaths within the margin (at least 1–2 m from the ecotone), or on the edge of the crop where paths run next to woodland known to be an important tick habitat, could be promoted to minimize tick exposure. In addition, based on the results of the present study, raising awareness that walking alongside woodlands also constitutes a tick risk could be promoted.     

Habitat and occurrence of ixodid ticks in the Liguria region,northwest Italy

Questing ticks were collected during monthly dragging sessions (March–August 2011) in three provinces of the Liguria region, north-western Italy, to evaluate the species occurrence, spatial distribution and relative abundance. A total of 1,464 specimens were collected in 94 dragging sites. Ixodes ricinus was the most abundant species (81.3 % of collected ticks), followed by Haemaphysalis punctata (10.9 %), Dermacentor marginatus (5.5 %), Ixodes frontalis (1.3 %), and Rhipicephalus spp. (0.9 %). Ixodes frontalis is reported for the first time in Liguria. An aggregation of I. ricinus positive sites was observed in inland areas characterized by dense forests dominated by deciduous trees (Castanetum and Fagetum phytoclimatic zones), especially in the west of the region where the differences in the Normalized Difference Vegetation Index (NDVI) were higher between inland and coastal sites. Negative binomial regression for repeated measures was used to model the associations of NDVI and season with counts of host-seeking I. ricinus nymphs. The NDVI was a good predictor of I. ricinus nymphs abundance, and confirmed its utility in discriminating habitat suitability for this vector in north-western coastal Italy, where dry habitat conditions may limit the distribution of this species.