Ixodid Species Research Articles

First molecular and functional characterisation of ferritin 2 proteins from Ornithodoros argasid ticks

Ferritins are iron-binding proteins that play critical functions in iron metabolism. Tick ferritins are essential in blood feeding, reproduction, iron transport, and protection of ticks from the iron-mediated oxidative stress during blood feeding and digestion. In ixodids, ferritin 2 (Fer2) is responsible for iron transport into peripheral tissues, it is critically involved in tick reproduction and has been identified as a good candidate antigen to be included in anti-tick vaccines. In argasids, information on the molecular and functional characteristics of ferritins is almost nonexistent. Given the potential of ixodid Fer2 as a vaccine target, the aim of the current study was to characterise the Fer2 orthologues in Ornithodoros erraticus (OEFer2) and O. moubata (OMFer2), including functional analyses by RNAi gene knockdown and the assessment of the protective efficacy of recombinant Fer2 protein in an animal vaccination trials. Characterisation and analysis of the OMFer2 and OEFer2 amino acid sequences showed high similarity to each other, and high similarity to the Fer2 sequences of ixodid species as well, confirming that Fer2 is highly conserved between both tick families and suggesting a similar function in the physiology of both argasid and ixodid ticks. Fer2 gene knockdown in O. moubata reduced egg hatchability rate and the subsequent number of emerging nymphs-1 up to 71%. Conversely, Fer2 gene knockdown in O. erraticus did not affect the treated ticks even though the Fer2 mRNA expression level was reduced by 90%. The recombinant form of O. moubata Fer2 (tOMFer2) was highly immunogenic and induced strong humoral responses when administered to rabbits formulated with Montanide adjuvant. The protective effect of the anti-tOMFer2 response was limited. While in O. erraticus, we did not observe any protective effect, in O. moubata it induced a significant reduction in oviposition without affecting the other parameters analysed. Accordingly, Fer2 seems to be involved in O. moubata embryogenesis. This study provides the first data on the molecular and functional characterisation of Fer2 in soft tick species and paves the way for further studies aimed at unveiling the functional aspects of Fer2 in soft ticks and confirming its potential as a vaccine candidate antigen.

Babesia and Theileria Identification in Adult Ixodid Ticks from Tapada Nature Reserve, Portugal.

This study, conducted in a nature reserve in southern Portugal, investigated the frequency and diversity of tick-borne piroplasms in six species of adult ixodid ticks removed from 71 fallow deer (Dama dama) and 12 red deer (Cervus elaphus), collected over the period 2012–2019. The majority of 520 ticks were Ixodes ricinus (78.5%), followed by Rhipicephalus sanguineus sensu lato, Hyalomma lusitanicum, Haemaphysalis punctata, Dermacentor marginatus, and Ixodes hexagonus. The R. sanguineus ticks collected from the deer were clearly exophilic, in contrast to the endophilic species usually associated with dogs. Four tick-borne piroplasms, including Theileria spp., and the zoonotic species, Babesia divergens and Babesia microti, were detected. B. divergens 18S rDNA, identical to that of the bovine reference strain U16370 and to certain strains from red deer, was detected in I. ricinus ticks removed from fallow deer. The sporadic detection of infections in ticks removed from the same individual hosts suggests that the piroplasms were present in the ticks rather than the hosts. Theileria sp. OT3 was found in I. ricinus and, along with T. capreoli, was also detected in some of the other tick species. The natural vector and pathogenic significance of this piroplasm are unknown.

ФАУНА ИКСОДОВЫХ КЛЕЩЕЙ – ПЕРЕНОСЧИКОВ ПИРОПЛАЗМИДОЗОВ И ЗОНАЛЬНЫЕ ОСОБЕННОСТИ ИХ ЭКОЛОГИИ

The North-Caucasian region, in terms of natural and climatic characteristics is the most favorable for the development of ixodid ticks - carriers of pathogens of blood-parasitic diseases of farm animals. In the conditions of various natural-geographical zones of Dagestan 22 species of ixodid ticks belonging to 8 genera and two families were identified on domestic animals. When ticks, parasitizing onwild animals are counted, their number increases to 32 species included in 9 genera, which is about 50% of all species, of tick fauna in our republic. Areas of ixodid activation and sites of animal infection coincide with the optimal landscape-geographical distribution zones with a high abundance and infection of the genus Hyalomma. Within the boundaries of the foci of ixodids, three typological belts are distinguished: - plain, foothill and mountainous regions of Dagestan, in which populations of the main carriers of pyroplasmidosis, H. scupense live (Schulze, 1918); I. ricinus (Linnaeus, 1758); B. annulatus (Say, 1821); H. p. plumbeum (Panz, 1795); H. a. anatolicum (Koch, 1944). The ixodid species begins to show activity at an average monthly temperature +10.5 ° C, an average monthly precipitation 47 mm, with a day length of 12 hours. The peak of parasitizing on hosts is observed at an average monthly air temperature +12.2 °C, an average monthly precipitation 60 mm, at the length of the day 14 hours. Autumn activation is recorded at an ambient temperature +15 °C, an average monthly precipitation 62 mm, with a day length 13 hours.

INFLUENCE OF NATURAL FACTORS ON THE NUMBER OF IXODIC TICKS OF THE GENUS DERMACENTOR IN TYUMEN REGION

At present, the ixodofauna of the Tyumen region is represented by six species of ixodid ticks – these are Ixodes persulcatus Schulze, 1930; Dermacentor reticulatus Fabricius, 1794 (D. pictus, Hermann, 1804); D. marginatus Sulz, 1776; I. apronophorus P. Sch., 1924; I. (Exopalpiger) trianguliceps Bir., 1895 and I. (Ceratixodes) plumbeus, Kirsch., 1936. Three species of ixodid ticks parasitize cattle: I. persulcatus, D. reticulatus, D. marginatus. The remaining three species of ticks, Ixodes apronophorus, Ixodes strianguliceps, and Ixodes plumbeus, belong to the nest-like parasitic type and therefore are less dangerous parasites for large mammals. The most widespread ticks of the genus Ixodes and Dermacentor in the context of all natural-geographical zones of the region are ticks of the genus Dermacentor, their dominance index was 54.8%. As a result of observation, it was noted that the temperature and humidity of the air affect the activity of ixodid ticks of the genus Dermacentor in nature. Thus, the peak of ixodid activity in the spring period fell on days when the air temperature reached values from 16 oC to 26 oC, and in autumn from 15 oC to 21 oC, while lower and higher humidity indices had a depressing effect on ixodid mites of the genus Dermacentor.

Transmissible parasitic zoonoses of the Kaluga Region

the purpose of the research is monitoring population and species composition of common blood-sucking ectoparasites of the Kaluga Region, mosquitoes and ixodid ticks, and parasitic zoonoses, in the circulation of which they are involved.Materials and methods. The records were made in all districts of the Kaluga Region and in the city of Kaluga. We studied open meadow-field and forest-shrub stations, closed meadow-field and near-water stations, and settlement stations. The species was identified using the atlases of ixodid ticks by I. M. Ganiev, A. A. Aliverdiev (1968) and V. N. Shevkoplyas (2008), and the guidance of R. M. Gornostaeva (1999). The situation with transmissible parasitic zoonoses in the Kaluga Region was assessed based on the analysis of information from open sources of the Hygienic and Epidemiological Center of the Kaluga Region and the Veterinary Committee under the Government of the Kaluga Region.Results and discussion. There are two species of ixodid ticks in the Kaluga region: Ixodes ricinus and Dermacentor reticulatus. The abundance index of ixodid ticks of the species I. ricinus is 16.8±1.32 individuals per 1 flag-hour in forest biotopes, and 11.6±1.12 individuals per 1 flag-hour in meadow biotopes, and the abundance index of D. reticulatus is 10,8±1.14 and 15.9±1.30 individuals per 1 flag-hour, respectively. Three mosquito species prevail, namely, Stegomya communis, S. vexans, and Culex pipiens. The maximum number was 8 thousand per 1 m3. During the study period, the causative agent of infectious tick-borne borreliosis was found on average in 10.6% of ixodid ticks collected from humans and in 13.2% of ticks collected in natural biotopes. The causative agent of human granulocytic anaplasmosis was isolated on average in 3.1% of ixodid ticks collected from humans and 6.4% of those collected in natural biotopes. Infection rate for I. ricinus ticks infected with pathogen of infectious tick-borne borreliosis was 16.9%, and D. reticulatus 12.3%.

SPREADING OF DERMACENTOR RETICULATUS TICKS IN UKRAINE

Currently Ixodid ticks are one of many components of natural biocenoses and Ixodidticks urbocenoses in Ukraine. Among the few species of Ixodid ticks that attack notonly animals, but also humans, one of the most widespread is Dermacentor reticulatus.Anymore, there are still a plenty of unknown facts about Dermacentor reticulatusspreading within Ukraine and, particular, in its western parts. Thus, the study of the prevalence of ticks of the Dermacentor reticulatus spicies in different geographic zones,their ecological characteristics, and biological patterns, epidemiological and medicalsignificance remains a significant topic for research.Objective. To study Dermacentor reticulatus ticks spreading on the territory of Ukraine,determine their ecological characteristics and epidemiological significance, to detect thepresence of ticks as components of humans and animals’ natural focal diseases.Material and methods. The main materials and tools, used for catching, preserving andidentifying ticks were tweezers, magnifiers, dissecting needles, white flag tissue, 70%alcohol, test tubes. Using the SEO - IMAGLAB optoelectronic system ticks were identified.Results. Research of Ixodid ticks has conducted in the "Laboratory for Diagnosis ofDiseases Transmitted by Tick Bites" of the Sector of Experimental and Clinical Researchof I.Ya. Horbachevsky Ternopil National Medical University, Ministry of Health ofUkraine since May 2017.An important issue of the study was not only to carry out identification of the ticks’ speciescomposition and their life forms, but also to investigate the biology and epidemiology ofspecies that attack humans and animals and are able to transmit pathogens of infectiousdiseases.During the period from May 2017 until November 2019 447 specimens of D. reticulatusticks have been identified in the laboratory, 287 of which are females and 160 males,collected in 74 localities from 10 regions of Ukraine.74 detected cases of ticks on animals, humans and grass were recorded. The maininhabitants, on which adults of both sexes were found, were 4 species of animals: dogs -34 cases, cows - 16, cats - 4, horses - 3, humans - 15 cases. In 2 cases, ticks were assignedto the "flag".Ticks from 21 localities were analyzed with the help of PCR, using a PCR amplifier. Thefact of tick infection with pathogens was established in 5 cases: 4 - Borelia burgdorferis.l, 1 - Anaplasma phagocytophilum and 1 - mixinfection of B. burgdorferi with A.phagocytophilum.We have created an interactive map based on medical GIS, which contains all the dataobtained. It has been found that the locations of D. reticulatus ticks are located in theinterval: the maximum northern point 510 44' 54'' n. lat. (Volyn region) and the mostsouthern point 450 03' 05'' n. lat. (Autonomous Republic of Crimea). The most westernpoint within Ukraine was found at 220 42' 49'' e.lat. (Transcarpathian region) and themost eastern point – at 380 64' 80'' e. lat. (Donetsk region.).Conclusion. A tick of the D. reticulatus species was found in 74 localities from 10 regionsof Ukraine. A study of the D. reticulatus tick spreading in the southern regions has shownthat this species occurs in 311 locations out of 640 samples. Most often, it is spread inhumid biotopes near the water reservoirs and in urbanized biocenoses, in which rodentsare common and where pets and people often enter. The main inhabitants of the D.reticulatus ticks were dogs, cows, horses, cats and humans. Studies of the epidemiologicalcondition of ticks have shown that they are often carriers of Borelia burgdorferi s.l. andAnaplasma phagocytophilum.

Ixodidae (Acari: Ixodoidea): descriptions and redescriptions of all known species from 1758 to December 31, 2019.

References to the descriptions and redescriptions of the 742 species of Ixodidae published from 1758 to December 31, 2019 are compiled, with the goal of enabling tick taxonomists to readily access this diffuse and often confusing literature. Additionally, data resulting from this effort are critically analyzed to demonstrate the problems attending correct identification of several tick species that are of medical, veterinary and/or evolutionary importance, and to highlight the need for new or enhanced diagnostic techniques. Recent morphological and molecular studies indicate that some ixodid species names represent more than one taxon; therefore, it is expected that new species will be described in the near future, based partly on material already deposited in museums around the world.

Features of Fauna and Ecology of Ixodid Ticks Parasitizing in the Central Part of the East European Plain

The purpose of the research is finding out features of fauna and ecology of ixodid ticks parasitizing in the Non-Black Earth Region of the central part of the East European Plain, which inhabit the Kaluga Region. Materials and methods. Ixodid ticks were collected and recorded according to generally accepted methods in all districts of the Kaluga Region and the city of Kaluga in 2009–2019 during their activity (in the spring from the melting of snow and until late autumn before the snow cover formation). A total of 11,282 ticks were collected in 412 flag-hours, of which 7,421 (65.7%) were collected from vegetation and 3,861 (34.3%) from animals. We studied open meadow and field areas, forest and shrub areas, closed meadow and field areas, and wetland stations and settlements. The species was identified using the Atlas of ixodid ticks by Ganiev and Aliverdiev (1968) and the Atlas by Shevkoplyas (2008). Results and discussion. There are two species of ixodid ticks in the Kaluga Region, Ixodes ricinus and Dermacentоr reticulatus. The number of D. reticulatus slightly exceeds (by 6%) I. ricinus, 53 and 46% respectively, which is explained by the even distribution of forest and meadow (pasture) biotopes in the Region. The abundance index of I. ricinus was 16.8±1.32 individuals per 1 flag-hour in forest biotopes, and 11.6±1.12 individuals per 1 flag-hour in meadow biotopes. The abundance index of D. reticulatus was 10.8±1.14 individuals per 1 flag-hour in forest biotopes, and 15.9±1.30 individuals per 1 flag-hour in meadow biotopes.

О НАХОЖДЕНИИ КЛЕЩЕЙ RHIPICEPHALUS ANNULATUS (SAY, 1821) (ACARI, IXODIDAE) НА ТЕРРИТОРИИ КЫЗЫЛОРДИНСКОЙ ОБЛАСТИ И ИХ ЭПИЗООТОЛОГИЧЕСКОЕ ЗНАЧЕНИЕ

Recently, there has been a change in the border of the ranges of ixodid ticks in the Kyzylorda region, respectively also the spread of various infections carried by them. The collected material on the fauna and distribution of ixodid ticks indicates an increase in the number of new species of ixodid ticks in this area. As a result of an epizootological survey of settlements in the southeastern part of the Kyzylorda region the Rhipicephalus annulatus ticks, carriers of pathogens of cattle pyroplamosis, were discovered for the first time in this region. As a result of an epizootological survey of settlements in the southeastern part of the Kyzylorda region in the fall of 2019 in two villages of the Zhanakorgan region, for the first time, several specimens of ticks were found on cattle, identified as Rhipicephalus annulatus - carriers of the pathogens of cattle pyroplamosis. In 2020, during repeated examinations of the same settlements, similar ticks were found at all stages of development. In the study by the method of enzyme-linked immunosorbent assay (ELISA) from ticks of this species, the antigen of the Crimea-Congo hemorrhagic fever virus was detected.

Lethal Effects of a Silica Gel + Pyrethrins (Drione) on Amblyomma americanum (Ixodida: Ixodidae) Larvae and Nymphs.

Ixodids (hard ticks) ingest blood from host animals, and they can transmit pathogenic organisms that induce medical and veterinary diseases. As resistance to synthetic conventional acaricides becomes more common, alternative tactics are coming under heightened scrutiny. Laboratory bioassays were used to assess the efficacy of CimeXa, a commercially available silica gel desiccant dust product, and Drione, a commercial product containing silica gel + pyrethrins and a synergist, piperonyl butoxide, against lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), larvae and nymphs. Both life stages were completely killed by CimeXa by 24 h, and Drione caused total larval mortality within 1 h when they were briefly immersed in the dusts and when they crawled across dust-treated substrate; nymphs were completely killed by 4 h after the same kinds of exposure. Mortality of A. americanum larvae and nymphs occurred after the pests crawled across dried aqueous suspensions of the products, but this was not as efficient and fast-acting as when the immature life stages were exposed to dry dusts. Further, dried aqueous suspensions of Drione were not substantially more lethal than dried aqueous suspensions of CimeXa. CimeXa and Drione will provide prophylactic control on vegetation and animals for as long as the silica gel remains without being physically removed. Both of the dust-based products will likely also be effective against other problematic ixodid species. Advantages and disadvantages, and potential uses, of desiccant dust-based acaricides are discussed.

ECTOPARASITES OF A STEPPE LEMMING LAGURUS LAGURUS PALLAS, 1773 IN THE SOUTH TRANS-URAL REGION (KURGAN OBLAST) IN CONNECTION WITH THE NATURAL FOCI OF TULAREMIA

Steppe lemming of the South Trans-Ural region is a rare species of open spaces. To the north, its distribution is limited to the subzone of herb-bunchgrass steppes and the southern strip of the forest-steppe subzone. The presented work summarizes the material, which gives the full species composition of the parasitic arthropods of this rodent, and gives quantitative characteristics of ectoparasites. In total 155 individuals and one nest of steppe lemming were examined for ectoparasites. There are 808 parasitic arthropods of 20 species, including 14 species of gamasid mites, 2 species of ixodid ticks and 4 species (subspecies) of fleas. According to the number of individuals of ectoparasites feeding on the steppe lemming, the dominance of gamasid mites is strongly pronounced, both prevailing multi-host species and specific, typical for other rodents (gray and red-backed voles, northern mole vole, Eurasian water vole, northern birch mouse). The contribution of ixodid ticks and fleas to the parasitofauna of the steppe lemming is small. Steppe lemming can be involved in circulation of a causative agent of tularemia in the South Trans-Ural region, but as an additional carrier in maintenance of a foci in biotopes, where it contacts the habitats of the Eurasian water vole.

Tick-borne encephalitis in the Far East focal region of the Eurasian continent

The analysis of the activity of natural foci of tick-borne encephalitis (TBE) in the Far Eastern Federal District (Primorsky and Khabarovsk Territories, the Jewish Autonomous and Amur Regions), represented by a single Sikhote-Alin focal region was performed. Endemic territories of China, Korea, Japan are adjacent to this focal region. In the last decade the decrease of the infection rate in ixodid ticks and the morbidity of TBE compared to the 1990s was observed. Data on the infection rates in ixodid ticks based on ELISA, PCR and TBEV isolation are often discrepant. Active circulation of TBEV that involved dominant and less significant species of ixodid ticks and mouse-like rodents has been demonstrated since 1952 in China, since the 1990s in Japan and since 2011 in South Korea. The circulation of TBEV strains of the Far Eastern subtype was determined in all these territories. The exception was 7 strains isolated in South Korea, which appeared to be the European subtype based on the results of molecular genetic analysis. Two new strains of TBEV from the organs of wild rodents Marmota himalayana were isolated in 2017 in the territories of previously unknown natural foci in the Tien Shan, China. The genetic divergence of these strains from three TBEV subtypes allowed us to establish the existance of a new Himalayan TBEV subtype (Him-TBEV), which, according to the authors, has been "hidden" for hundreds of years. One can also speculate the processes of emergence of new TBEV subtypes The most complete picture of the Far Eastern population of TBEV was obtained in the last decade of the twentieth century, which served as the basis and impetus for the study and comparative analysis of the differences in numerous strains of TBEV isolated on the territory of the Eurasian continent.

Effects of Silica-Based CimeXa and Drione Dusts Against Lone Star Tick (Ixodida: Ixodidae) on Cattle.

Ixodid ticks vector pathogens of humans, livestock, and wildlife, and occur in tropical and temperate regions worldwide. We used the lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), as a model for other ixodid species, including the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae). We assessed the lethality of CimeXa, an inert silica-based desiccant dust, and Drione, a silica-based desiccant dust with pyrethrin and piperonyl butoxide (PBO), against A. americanum larvae and nymphs on calves. CimeXa was highly lethal to larvae released onto shaved calf skin 72-96 h previously, and moderately toxic to nymphs. It did not affect immature life stages treated after they began feeding because desiccation was offset by ingestion of blood. Being inert, CimeXa can protect cattle from infestation before feeding occurs for a potentially indefinite period of time. Drione killed immatures within 24 h when released on treated skin and when applied to feeding ixodids because of the pyrethrin and PBO (PBO will also reduce resistance to pyrethrin if it develops). When CimeXa was applied to calves with the hair intact, ≈90% and ≈70% of A. americanum larvae and nymphs, respectively, were killed within 24 h and Drione killed 100% of each life stage. Drione also prevented and drastically reduced egg production and hatching. While CimeXa protects against infestation by immatures, Drione will also control ticks that are feeding. When pyrethrin and PBO in Drione eventually degrade, the silica aerogel carrier can continue to protect against infestation indefinitely.

Epidemiological study of ticks collected from the northern tamandua (Tamandua mexicana) and a literature review of ticks of Myrmecophagidae anteaters

The family Myrmecophagidae contains three anteater species: Tamandua mexicana (Saussure, 1860), Tamandua tetradactyla (Linnaeus, 1758) and Myrmecophaga tridactyla (Linnaeus, 1758). These American anteater species currently face many conservation threats, among which road traffic accidents stand out. Parasitic studies on this family are scarce, and some of them include records of ectoparasites. Specifically for northern tamandua (T. mexicana), there is a lack of studies at population level. The objectives of the present research were to carry out an epidemiological study of tick species and its abundance on road-killed northern anteater specimens and, moreover, to perform a literature review of ticks collected from anteaters of Myrmecophagidae family. Five tick species were identified, including four Amblyomma spp. and Rhipicephalus sanguineus sensu lato, on 23 road-killed anteaters. Tick infestation prevalence was 43% (10/23), with a median tick infestation intensity of 3.5 per anteater (interquartile range 1–13.7). The bibliographic review highlighted the existence of twenty-nine ixodid species recorded on the three anteater species from 14 countries, mainly Brazil. The most common tick species on the Myrmecophagidae family are Amblyomma nodosum, A. calcaratum, A. cajennense sensu lato and A. auricularium. Some of these ixodids were also described as vectors of pathogens. Further studies are needed to evaluate the impact of ticks on anteater fitness, and to assess the role of these mammals as reservoirs of vector-borne diseases.

Efficacy of Novaluron + Pyriproxyfen (Tekko Pro) Insect Growth Regulators Against Amblyomma americanum (Acari: Ixodidae), Rhipicephalus (Boophilus) annulatus, Rhipicephalus (Boophilus) microplus, and Rhipicephalus sanguineus.

Ixodids are globally distributed pests that transmit many disease agents. Increasing resistance to conventional acaricides raises the need for alternative tactics. Novaluron and pyriproxyfen are insect growth regulators (IGRs) that have variable potencies against acarines. We conducted in vitro and in vivo experiments to assess novaluron + pyriproxyfen (marketed as Tekko Pro) against four ixodid species. Laboratory assays on the brown dog tick, Rhipicephalus sanguineus (Latreille) (Ixodida: Ixodidae), and the lone star tick, Amblyomma americanum (L.) (Ixodida: Ixodidae), reduced metabolic activity in larvae and nymphs. Concentrations of novaluron + pyriproxyfen dried on filter paper impeded molting of larval R. sanguineus (less effective against nymphs). Molting A. americanum larvae were reduced by >95% using 4 and 8 µg/cm2 eliminated molting; nymphal molting was reduced but not halted even at 16 µg/cm2. On calves, novaluron + pyriproxyfen stopped larval A. americanum metabolic function 1 d post-treatment and larvae did not molt. When larvae were released 30 d after treatment, metabolic activity was reduced by 95% and molting was reduced by 94%. Southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Canestrini) (Ixodida: Ixodidae), larvae released 1 d after treatment on calves were 99% prevented from reaching adulthood. The treatment did not interfere with larval development when larvae were released 52 d after treatment. The cattle fever tick, Rhipicephalus (Boophilus) annulatus (Say) (Ixodida: Ixodidae), failed to reach adulthood when larvae were released on calves a day after treatment (residual activity was not assessed for R. annulatus). These IGRs, and possibly others, offer an alternative to conventional acaricides for ixodid control on cattle.

Relationships of Salinity, Relative Humidity, Mud Flat Fiddler Crabs, Ants, and Sea Ox-Eye Daisy With Ixodid Distribution and Egg Survival on the South Texas Coastal Plains.

The South Texas coastal plains are mostly dominated by mesquite-thorn scrub from the Mexican border to cattle ranches extending north from Willacy Co. A wildlife corridor on the plains, composed of natural habitat, supports hosts of many ixodid species. Occasional wind (not lunar) tides and infrequent storm surges inundate coastal plain areas with hypersaline water from the Lower Laguna Madre, creating large areas of saline soil. Laboratory and field experiments and observations were used to identify relationships between salinity and other abiotic and biotic factors that influence ixodid distribution. Exposure of lone star tick, Amblyomma americanum (L.), and Rhipicephalus microplus (Canestrini) eggs to hypersaline water is lethal. Although intermittent hypersaline flooding kills ixodid eggs, saline soil was not particularly toxic. When relative humidity is relatively low, desiccation causes high egg mortality on dry soil, regardless of salinity. Substantial year-round populations of mud flat fiddler crabs, Uca rapax (Smith) (Decopoda: Ocypodidae), occur on saline soil and eliminated ≈80% of A. americanum egg masses overnight. On saline and low-salinity soils predatory formicids, including the red imported fire ant, Solenopsis invicta (Buren), were indifferent to the eggs. Saline soils were dominated by the sea ox-eye daisy, Borrichia frutescens (L.) DC, and its color allowed production of a GIS-based map. At least 24.4% of the wildlife corridor supports heavy stands of B. frutescens which is indicative of high U. rapax populations. Ixodid populations were negligible on heavy B. frutescens stands because of associated salt water toxicity, desiccation, and predation by U. rapax on eggs.

Nymphal engorgement weight predicts sex of adult Amblyomma americanum, Amblyomma maculatum, Dermacentor andersoni, Dermacentor variabilis, and Rhipicephalus sanguineus ticks.

The engorgement weights of laboratory-raised nymphs of five common ticks in the USA, Amblyomma americanum, Amblyomma maculatum, Dermacentor andersoni, Dermacentor variabilis, and Rhipicephalus sanguineus, experimentally fed to repletion on an adult sheep (Ovis aries) were evaluated to determine the sex of molted adult ticks. Length of feeding period of nymphs, molting success and durations, and sex ratios between tick species were also compared. Individual replete nymphs were weighed and allowed to molt to adults in a humidity chamber. Length of feeding duration was different by species (F4,7785 = 1963.79; P < 0.0001); R. sanguineus nymphs became replete fastest, followed by A. americanum, D. variabilis, A. maculatum, and D. andersoni. Significant difference in molting success was not detected. The mean body weight of engorged nymphs of A. americanum (t = 32.3; df = 662), A. maculatum (t = - 9.70; df = 255), D. variabilis (t = 15.7; df = 751), and R. sanguineus (t = 5.17; df = 560; all P < 0.0001) molting into females was greater than that of nymphs molting into males, whereas heavier D. andersoni engorged nymphs became males (t = 8.71; df = 480; P < 0.0001). Amblyomma maculatum nymphs that molted to females fed to repletion faster (t = 3.33; df = 265; P ≤ 0.001) than nymphs that molted to males and a higher proportion (χ2 = 48.4; df = 1, P < 0.0001) of A. maculatum and D. andersoni (χ2 = 8.19; df = 1, P = 0.004) molted to females than males. Our study demonstrated biological and behavioral differences in and between engorging nymphs of five ixodid species. These findings may aid in studies evaluating the role of tick sex in transmission of tick-borne pathogens.

Lethal Effects of Silica Gel-Based CimeXa and Kaolin-Based Surround Dusts Against Ixodid (Acari: Ixodidae) Eggs, Larvae, and Nymphs

As tick resistance to conventional acaricides becomes more common, alternative control tactics are gaining attention. Insecticidal dusts CimeXa and Surround, based on silica gel and kaolin, respectively, were assessed against Amblyomma americanum (L.) (Ixodida: Ixodidae) eggs, larvae, and nymphs in the laboratory. Coverage by the dry dusts, particularly CimeXa, was strongly lethal to larvae and to a lesser extent to nymphs. Larval mortality was also high when larvae crawled across thin layers of CimeXa and, to a lesser extent, Surround dusts. CimeXa was more lethal to nymphs that crawled across a thin layer than Surround. Larval mortality after crawling on dried aqueous suspensions of the dusts for 30 min and for 48 h caused moderate mortality (<80%) regardless of a 10-fold difference in concentration; nymphal mortality was negligible. In a field experiment, CimeXa dust strongly reduced numbers of Gulf coast tick, Amblyomma maculatum (Koch) (Ixodida: Ixodidae), larvae and nymphs by 24 h. Possible application of CimeXa to control other species of ixodid ticks is discussed as well as advantages and disadvantages of using dusts for tick control under field conditions.

History of the species range of ixodid ticks, vectors of pathogens with natural nidality (Acari, Ixodidae), as a prerequisite of their intraspecific biodiversity

Morphological, taxonomic, and some ecological aspects of intraspecific biodiversity of five ixodid species transmitting pathogens with natural nidality, with extensive ranges of different types are examined. Causal relations of ixodid intraspecific biodiversity with the origin of the species ranges are considered.

Pictorial Key for Identification of Immature Stages of Common Ixodid Ticks Found in Pastures in Oklahoma

Abstract. Many species of ixodid ticks in the United States are parasitic on cattle and pose a threat to veterinary and public health for those engaged in occupations in pasturelands. While encountered often, nymphs and larvae of the most common tick species can be difficult to identify, yet research associated with tick ecology and epidemiology of tick-borne infection requires proper identification. High-quality images were prepared of the larval and nymphal stages of the most common species of ticks in Oklahoma pastures: larvae of the lone star tick, Amblyomma americanum (Linnaeus), Gulf coast tick, Amblyomma maculatum Koch, winter tick, Dermacentor albipictus (Packard), American dog tick, Dermacentor variabilis (Say), blacklegged tick, Ixodes scapularis Say, and brown dog tick, Rhipicephalus sanguineus (Latrielle); and nymphs of A. americanum, A. maculatum, D. variabilis, I. scapularis, and R. sanguineus. A dichotomous key and pictorial guide for each life stage were prepared.