The distribution in Oregon of Ixodes pacificus, Dermacentor andersoni, and Dermacentor occidentalis with a note on Dermacentor variabilis (Acarina: Ixodidae).
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Quinone inhibition of sex pheromone activity in the ticks Dermacentor andersoni Stiles and Dermacentor variabilis (Say).
Disruption of sex pheromone activity in female Rocky Mountain wood ticks, Dermacentor andersoni Stiles, and American dog ticks, Dermacentor variabilis (Say), was achieved by treatment with the quinones para-benzoquinone and menadione. The most effective treatments were those administered by inoculation to unfed, mature, adult females prior to feeding. Inoculation of p-benzoquinone was also effective when administered to feeding ticks, from 2 to 5 days after they had attached, though not to the same extent as when it was given to unfed ticks. Decreases in sex pheromone activity were also observed with D. andersoni females, but not D. variabilis females, allowed to feed on rabbits receiving menadione daily by oral administration. Histochemical studies and electron microscopy revealed loss of neutral lipid secretory droplets in the pheromone glands, but no damage to gland structure, following treatment with p-benzoquinone. Elemental analysis revealed more than four times as much chlorine in pheromone glands of p-benzoquinone-treated D. variabilis females than in pheromone glands from control specimens. An extract of partially fed D. variabilis females treated with p-benzoquinone before feeding contained much more 2,6-dichlorophenol than an extract of untreated, partially fed females. Evidently, the quinone affects the neutral lipid component of the female sex pheromone gland, disrupting secretion and release of pheromone to the external body surface.
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[Prevalence of the ticks Dermacentor marginatus (Sulzer, 1776) and Dermacentor reticulatus (Fabricius, 1794) and their importance as vectors of diseases in Germany (author's transl)].
From a systematical study of German ticks resulted the occurrence of two tick species of the genus Dermacentor. D. marginatus is found to be widely spread in Southern Germany. Adults of the tick feed mainly on sheep. D. reticulatus is first described from Germany where the tick occurs endemic in a limited forest area on red deer. The two tick species are known from neighbouring countries of Germany in transmitting virus, rickettsiae, bacteriae and protozoa but are not yet well studied in Germany. Geiographical distribution and seasonal occurrence of D. marginatus indicates the role of the tick in the epidemiology of Q fever in Germany.
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Ultrastructure of ANaplasma marginale Theiler in Dermacentor andersoni Stiles and Dermacentor variabilis (Say).
Cattle were inoculated with a Virginia isolate of Anaplasma marginale Theiler and served as an infective source for laboratory-reared Dermacentor andersoni Stiles and D variabilis (Say) nymphs. Anaplasma marginale was demonstrated by electron microscopy in gut tissues of replete nymphal ticks and in unfed, incubated, and feeding adult ticks that were exposed to the organism as nymphs when they fed on an infected cow. The A marginale organism in replete nymphs and adult feeding ticks were morphologically similar to A marginale described previously from infected bovine erythrocytes. Colonies of A marginale were demonstrated by light and electron microscopy in midgut epithelial cells of unfed adult D andersoni and D variabilis that had been incubated at 37 C for 3 days. Anaplasma marginale organisms in colonies were very pleomorphic. Small electron-dense particles were demonstrated in all infected tick stages studied, but were most evident in colonies from incubated, unfed ticks. They may represent a reproductive form of A marginale.
Anaplasma↗
Transmission of Anaplasma marginale Theiler by Dermacentor andersoni Stiles and Dermacentor variabilis (Say).
Cattle were inoculated with a Virginia isolate of Anaplasma marginale Theiler and served as an infective source for laboratory-reared Dermacentor andersoni Stiles and D variabilis (Say) nymphs. Following a molt and subsequent feeding of adult ticks on susceptible cows, transstadial transmission of A marginale occurred from cattle with parasitemias ranging from undetectable (in a carrier cow) to a peak of 27% (in an acutely ill cow). Homogenates of gut tissue from unfed, incubated, and feeding adult ticks that were infected as nymphs were all infective; however, the prepatent period varied according to treatment of ticks after they had molted to the adult stage. Prepatent periods of infections in calves resulting from injection of homogenated tissue from unfed adult ticks was 29 and 34 days longer than the prepatent periods that developed in calves exposed to homogenated tissue from ticks that were feeding or incubated at 37 C for 3 days. Transovarial transmission did not occur when F1 larvae, hatched from eggs produced by female ticks known to be infective, fed on susceptible cattle.
Anaplasmosis↗
Dermacentor variabilis and Dermacentor andersoni: genital sex pheromones.
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Acetone↗
Absence of assembly pheromones in the hard ticks Dermacentor variabilis and Dermacentor andersoni (Acari: Ixodidae).
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[The discovery of Dermacentor reticulatus (Ixodida, Ixodidae) in the East German districts of Leipzig and Halle].
A report on findings of Dermacentor reticulatus, a very rare tick species in the GDR, in 3 localities situated in the heath region of Düben and Dahlen (GDR districts of Leipzig and Halle). Three adults of Dermacentor reticulatus ticks were caught by brushing over the vegetation with a flag in one of 235 places in May and September 1987. On the other hand, a total of 2,877 Ixodes ricinus ticks was found in all places. In the same year, from the same area, we also found 2 adults of Dermacentor reticulatus on a man's clothing and on a horse.
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Neurosecretory system of the American Dog Tick, Dermacentor variabilis (Acari: Ixodidae). ii. Distribution of secretory cell types, axonal pathways and putative neurohemal-neuroendocrine associations; comparative histological and anatomical implications.
Histological observations using specialized techniques reveal neurosecretory cells in 18 centers throughout the rind (cortex) of the central nerve mass or synganglion of Dermacentor variabilis. Many cells contribute to complicated networks of neurosecretory pathways and tracts in pre- and post-esophageal portions of the synganglion. The four types of neurohemal-neuroendocrine associations found in Dermacentor resemble structures found in soft ticks (Argasidae) and in other Arachnida, but are more diverse than those described from any other single species. Neurosecretory terminals are distributed diffusely and in two concentrated associations within the perineurium of the synganglion and major peripheral nerves. Terminals are also distributed in the perineurial layers of lateral segmental organs which lie in the general hemocoel at the level of the pedal nerves. A retrocerebral organ complex surrounds the esophagus at its junction with the midgut. The complex includes dorsal and ventro-lateral lobes (containing neurosecretory terminals and intrinsic secretory cells1 and the proventricular (neurohemal) plexus. This plexus seems to be a modified (concentrated) cardioglial association. Cardioglial associations are also formed by the neurosecretory innervation of vascular walls of the dorsal aorta and circulatory sinuses which envelope the synganglion and major peripheral nerves. Inferential considerations of neurosecretory and endocrine interactions in the Acari are based on these anatomical and histological data which also provide the basis for evolutionary considerations of anatomical relationships and specializations in the neurosecretory systems of other Arachnida.
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Basophils in skin reactions of mast cell-deficient mice infested with Dermacentor variabilis.
Acquired resistance to ticks in guinea pigs has been found to be associated with basophil-rich skin reactions. Mice, which are generally believed to possess few, if any basophils, also acquire resistance following repeated tick infestations and this has been found to be associated with increased numbers of dermal mast cells. Mast cell-deficient W/Wv mice have, however, also been shown capable of acquiring resistance after two infestations with Dermacentor variabilis larvae. In the studies described here, we have examined, with the electron microscope, skin reactions in W/Wv and +/+ mice undergoing their third infestation with Dermacentor variabilis. Basophils, along with neutrophils and eosinophils, were identified using established criteria. The possibility that basophils contribute to various pathogenetic mechanisms in these and other strains of mice is discussed.
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Tick infection rates with Borrelia: Ixodes ricinus versus Haemaphysalis concinna and Dermacentor reticulatus in two locations in eastern Germany.
Unfed nymphal Ixodes ricinus, Haemaphysalis concinna, and adult Dermacentor reticulatus were collected in two locations of Saxony in July and September 1991 by flagging. In July, the abundance of nymphal I. ricinus was about 2-3 times higher than that of nymphal H. concinna, a time of the year when nymphs of both species are reported to have a seasonal peak of activity. No D. reticulatus were flagged concurrently. In September, host-seeking activity of nymphal I. ricinus was again quite high as was that of adult D. reticulatus but only low numbers of nymphal H. concinna were collected. The flagged ticks were individually examined for Borrelia by an indirect immunofluorescence assay (I. ricinus: n = 414; H. concinna: n = 96; D. reticulatus: n = 116). The prevalence of Borrelia (probably B. burgdorferi) in I. ricinus varied from 12.1% to 21.0%. No borreliae were found in H. concinna. Of the examined D. reticulatus from one site (n = 97) 11.3% contained either B. burgdorferi or a related Borrelia. This may be the first finding of Borrelia in an Eurasian Dermacentor species.
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The effect of female body size on male mounting behaviour in Dermacentor variabilis and D. andersoni.
This study was undertaken to determine if body size of female ticks was an important factor in eliciting the mating behaviour of Dermacentor variabilis and D. andersoni males. Dummy female ticks (DFTs) representing varying sizes of feeding females were prepared from plastic beads. Size of DFT was shown to be important in determining both the time spent by males in contact with DFTs and the extent of male mating response released. Dermacentor variabilis males preferred the smaller-sized DFT, whereas D.andersoni males preferred the larger sizes. Males of both species were able to discriminate between size of DFT only when mounting sex pheromone (MSP) was present. Size of the DFT was more important than the composition of the MSP extract in determining the time males spent in contact with DFTs. Males of both species were sensitive to variations in concentration of extract, and spent 2-6 times longer in contact with DFTs when the concentration was optimal than when it was not. No significant difference in the male's mating response was seen in response to variation in concentration of heterospecific extract. Male mating response, i.e. the behaviour of the male as it progresses through the initial contact, climbing onto the dorsal surface and turning onto the venter, was shown not to be dependent upon how long the male spent in contact with the DFT. Male D. andersoni had a much lower mating response to DFTs than D. variabilis males, suggesting that some further stimulus may be required.
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[One of the developmental dead ends or a method of dispersal of the pasture tick Dermacentor marginatus].
Accumulation of pasture ticks Dermacentor marginatus has been discovered in the wool of sheep, 5-6 cm from the skin surface, the temperature in those sites being permanent 18-20 degrees C. The ticks died either in the course or following ovipositor. It may be assumed that this was followed by the appearance of larvae from oocysts. It is suggested that the above phenomenon is one of the deadlines in Dermacentor marginatus development or one of the unusual ways of their larvae habitation on pastures.
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[Ixodes ricinus, Haemaphysalis concinna and Dermacentor reticulatus (Ixodida, Ixodidae) in the East German district of Leipzig].
Haemaphysalis concinna and Dermacentor reticulatus mostly occur in narrow-limited humid biotopes of certain landscapes, whereas Ixodes ricinus--as wellknown--occurs more or less occupying the whole territory in kind of a mosaic; in regard of epidemiological questions at least, such a distribution may be resumed for Ixodes ricinus. Haemaphysalis concinna nearly regularly may be found in certain biotopes. Considering the possible role of Haemaphysalis concinna and Dermacentor reticulatus as vectors and reservoirs of transmissive agents special attention is paid to the transmitting of tick-borne borreliosis.
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Persistence of colonies of Anaplasma marginale in overwintering Dermacentor variabilis.
Dermacentor variabilis were infected as nymphs with Anaplasma marginale by allowing the ticks to feed on a single infected donor calf. Two weeks after molting to the adult stage, the ticks were allotted into 1 of 3 groups and were allowed to overwinter at room temperature (25 C) in the laboratory (group 1), cold storage (4.5 C) in the laboratory (group 2), or outdoors in leaf litter (group 3). Persistence of A marginale was assessed by determining density of colonies (number of colonies/0.1 mm2 of gut tissue examined) in tick gut specimens at 3, 5, 7, 9, and 12 months after molting to the adult stage. Colonies of A marginale were found in all groups at every density evaluation period. Highest colony densities were observed uniformly in specimens collected at month 7 (May); densities decreased at month 9 and were lowest at month 12. Statistical analysis indicated that ticks subjected to cold storage and to outdoor conditions had similar colony densities of A marginale; the density curve in these 2 groups indicated significant quadratic effects over time, with peak densities in May. Mean colony density in ticks kept at room temperature fit a different quadratic equation. The morphologic data indicated that A marginale overwinters in Dermacentor variabilis, and that increasing numbers of organisms are found from January to May.
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[Evaluation of the apron as a taxonomic trait in ixodid ticks of the genus Dermacentor Koch (Ixodoidea, Ixodidae)].
Study of the apron in 9 species of the genus Dermacentor from the fauna of the USSR has revealed differencies in its structure. The subgenus Dermacentor (s. str.) differs from two other subgenera both in the shape of the apron itself and in the shape of the postgenital sclerite and setae of perigenital area. Close species within each of two other subgenera differ in apron proportion, shape and size of denticles along its hind edge, and sometimes in their number. Inspite of the statistically reliable interspecific differences in apron structure a wide range of individual variability of some details and geographical specificity of samples from various places of the area were observed in species with a vast area.
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Bovine anaplasmosis transmission studies conducted under controlled natural exposure in a Dermacentor andersoni = (venustus) indigenous area of eastern Oregon.
In Anaplasma marginale transmission studies conducted on the high semi-arid range of eastern Oregon during the 1974 and 1975 vector season, A marginale-susceptible calves (principals) were maintained on 2 raised tick-proof platforms. Anaplasmosis-susceptible control calves of approximately the same age and latent-infected cows grazed the area surrounding the platforms. One latent-infected steer spent the entire 1975 vector season on a platform with the principals. The 28 principals did not develop anaplasmosis, whereas 15 of 30 (50%) controls became infected. The disease was not transmitted from the latent-infected cattle to the principals exposed only to flying hematophagous insects, whereas 50% of the controls exposed to the Rocky Mountain wood tick Dermacentor andersoni) = (venustus) developed the disease. Dermacentor andersoni appears to be the principal vector on this range.
Anaplasmosis↗
[Diagnosis of subgenera of the genus Dermacentor Koch by the larva and nymph and new data on the distribution of the subgenus Asiacentor (Ixodidae)].
On the basis of parallel study of natural and cultivated preimaginal phases of the genus Dermacentor differential diagnoses of three palaearctic subgenera were worked out: Asiacentor Filippova et Panova , 1974, Serdjukovia Dias , 1963 and Dermacentor (s. str.) 1844. The diagnoses are also based on peculiarities of chaetotaxy and other characters of small sizes. On the basis of identification of species of the subgenus Asiacentor on immature phases new sites of their distribution were found out: D. pavlovskyi : in the Issyk - Kul hollow, in the foothills from the side of Terskey - Alatau ridge; D. montanus: in Gissarsky ridge in the environs of Lake Iskander - Kul . Remoteness of these cites from the distribution borders known earlier point to ecological and geografical differential peculiarities of the subgenus and its species.
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