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PubMedDate not supplied

[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.

Animals↗
PubMed1990

[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.

Animals↗
PubMed1987

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.

Anaplasma↗
PubMedDate not supplied

[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.

Animals↗
PubMed1977

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↗
PubMedDate not supplied

[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.

Animals↗
PubMed1981

Resistance and cross-resistance of guinea pigs to Dermacentor andersoni Stiles, D. variabilis (Say), Amblyomma americanum (Linnaeus), and Ixodes scapularis Say.

The ability of guinea pigs to acquire resistance to Dermacentor andersoni and Amblyomma americanum was determined by repeatedly infesting separate sets of guinea pigs with tick larvae. Resistance was measured in terms of reduced numbers successfully engorging and reduced weight of those ticks that engorged. An 83% reduction in numbers of larvae engorging and a 64.5% reduction in the weight of engorged larvae were seen between the first and second infestations with D. andersoni. Guinea pigs exhibited considerably less resistance to A. americanum the third time they were exposed to this species than did guinea pigs infested twice with D. andersoni. Feeding success was only 30.8% less than the initial percentage that engorged, and the percentage weight reduction was 35. During the challenge infestations, sizable fluid-filled vesicles formed on ears of the guinea pigs used as hosts for D. andersoni or A. americanum. Cross-resistance was evaluated by dividing D. andersoni-resistant animals into groups and challenging them with D. andersoni D. variabilis, A. americanum, or Ixodes scapularis. Appreciable cross-resistance was apparent between the two Dermacentor species. The weights of the A. americanum and I. scapularis were significantly reduced, but not the number that engorged. When A. americanum-resistant guinea pigs were challenged, they were cross-resistant to D. variabilis but not to D. andersoni. Skin tests on guinea pigs in which extracts of tick salivary glands were used as the antigens did not conclusively reflect the same patterns of cross-reactions noted in the tests of cross-resistance.

Animals↗
PubMed1993

Dermacentor rhinocerinus (Denny 1843) (Acari: Ixodida: ixodidae): redescription of the male, female and nymph and first description of the larva.

Presented is a diagnosis of the male, female and nymph of Dermacentor rhinocerinus, and the 1st description of the larval stage. Adult Dermacentor rhinocerinus parasitize both the black rhinoceros, Diceros bicornis, and the white rhinoceros, Ceratotherium simum. Although various other large mammals have been recorded as hosts for D. rhinocerinus, only the 2 species of rhinoceros are primary hosts for adults in various areas of east, central and southern Africa. Adults collected from vegetation in the Kruger National Park, Transvaal. South Africa were reared on rabbits at the Onderstepoort Veterinary Institute, where larvae were obtained for the 1st time.

Animals↗
PubMed2000

Efficacy of selamectin against experimentally induced tick (Rhipicephalus sanguineus and Dermacentor variabilis) infestations on dogs.

Seven controlled studies were conducted to investigate the efficacy of selamectin against weekly infestations of dogs with Rhipicephalus sanguineus and Dermacentor variabilis. Treatments (selamectin or vehicle alone) were applied topically at weekly, 2-week, or monthly intervals or in a "Monthly Plus" regimen (monthly treatment with an additional treatment at 14 days after the first treatment). Selamectin was supplied in unit dose tubes designed to deliver a minimum dosage of 6mgkg(-1). The studies ranged in duration from 37 to 90 days. Fifty adult ticks (+/-2) were applied approximately weekly, and tick counts were performed 3, 4, and 5 days after each infestation. The efficacy of selamectin was expressed as the percentage reduction in geometric mean tick counts on selamectin-treated dogs compared with those for dogs treated with the vehicle alone (negative-control). In one study, the engorgement of Dermacentor variabilis was assessed by weighing ticks after removal on the fifth day after each infestation. Weekly and 2-week interval treatments with selamectin provided efficacies against R. sanguineus of >89% across the entire study periods, with 100% efficacy being achieved from 21 days after the first dose and thereafter (study duration, 37 days for the weekly regimen and 44 days for the 2-week interval regimen). D. variabilis also was well controlled by the 2-week interval treatment regimen, with >96% efficacy being achieved from 21 days after the first treatment and thereafter until the end of the study (study duration: 90 days). In five of six studies incorporating three treatments at monthly intervals, the percentage reduction in R. sanguineus and D. variabilis counts 5 days after infestation ranged from 90 to 100% in the second and third months after treatment began. In the sixth study, reductions of > or =95% in D. variabilis counts 5 days after infestation were achieved for 2 weeks after each treatment in the second and third months. For the Monthly Plus regimen, from the second treatment (day 14) onwards, selamectin achieved 83-100% reductions in R. sanguineus and D. variabilis counts 3 days after infestation, and 94-100% reductions 5 days after infestation in three of the four studies. In the fourth study, selamectin demonstrated good efficacy against D. variabilis for 2 weeks after each treatment. In all seven studies, the counts from the selamectin-treated dogs were significantly (P< or =0.018) lower than those from the vehicle-treated dogs on 77 of the 80 assessments made 5 days after infestation. Selamectin also significantly (P< or =0.0105) reduced engorgement of female D. variabilis. These studies demonstrated that selamectin, administered topically to the skin in a single spot at a minimum dosage of 6mgkg(-1) at monthly intervals, was effective in the control of experimentally induced R. sanguineus and D. variabilis infestations on dogs.

Administration, Topical↗
PubMed2026

Metagenomic analysis of the midgut microbiome in Dermacentor abaensis ticks at different feeding states.

Ticks are blood-sucking ectoparasites of humans and animals, ranking second only to mosquitoes as vectors of diseases. Dermacentor abaensis is distributed in Sichuan, Qinghai, and Gansu, China. Because D. abaensis harbors several pathogens, it poses a threat to public health and livestock production. However, the midgut microbiota of D. abaensis at distinct feeding states remains poorly characterized. Adult D. abaensis ticks at various feeding states were collected from yaks in Gansu Province, China. Genomic DNA was extracted from midguts and midgut contents of unfed, partially fed, and fully engorged female D. abaensis. A metagenomic sequencing approach was employed to profile the midgut microflora among three groups. A total of 83 phyla, 908 genera, and 1857 species were annotated across the three groups. At the phylum level, Pseudomonadota, Mucoromycota, and Ascomycota were the most abundant. At the species level, common bacterial species such as Klebsiella pneumoniae and Anaplasma phagocytophilum, alongside viruses and eukaryotes, were detected in all three groups. Unique microorganisms were also observed in each group: unfed (n = 305), partially fed (n = 59), and fully engorged (n = 20). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested that the D. abaensis microbiome contains a relatively high abundance of functional genes involved in lipid and amino acid metabolism across the three different feeding states. These findings indicate that while core microbial taxa are shared in the midgut of female D. abaensis, observable trends suggest variations in microbial diversity and composition as blood-feeding progresses. The present study provides a descriptive baseline of the midgut microbial composition of D. abaensis, which may inform future studies on tick biology and the ecology of tick-borne pathogens.

Animals↗
PubMed1980

Dermacentor variabilis: uncomplicated eyelid involvement.

Ocular eyelid infestation of Dermacentor variabilis, the American dog tick, occurred in a 34-year-old man who had been sleeping in an open-floored tent in an Indiana field. The tick was mechanically removed with steady and firm pressure with cilia forceps, with care taken to remove all mouth structures. The involved eyelid area healed rapidly without ocular or systemic complications.

Adult↗
PubMed1995

Dermacentor andersoni: salivary gland proteins suppressing T-lymphocyte responses to concanavalin A in vitro.

Salivary glands obtained from feeding adult female Dermacentor andersoni (Acari:Ixodidae) were fractionated using differential centrifugation, detergents, centrifugal concentrators incorporating filter membranes with various molecular weight cutoffs, and preparative SDS-PAGE. A lymphocyte proliferation assay was used to evaluate the effects of salivary gland fractions on ConA-induced blastogenesis of normal murine splenocytes. Lipid, soluble, and detergent-soluble fractions were found to significantly suppress ConA-induced proliferation of splenocytes. Fractions containing soluble proteins suppressed splenocyte proliferation by ca. 26%. Suppressant activity in these fractions was due to components with molecular weights greater than 30 kDa. This suppression of splenocyte proliferation occurred with as little as 0.25 microgram protein per well. Salivary gland preparative SDS-PAGE fractions containing one or more soluble polypeptides or proteins with molecular weights in the range 36 to 43 kDa significantly suppressed murine splenocyte responses to ConA in vitro.

Animals↗
PubMed2000

Nitric oxide synthase and cGMP activity in the salivary glands of the American dog tick Dermacentor variabilis.

We colocalized nitric oxide synthase (NOS) activity in epithelial cells that surround the salivary gland duct in female Dermacentor variabilis with NADPH diaphorase histochemistry and immunohistochemistry using a polyclonal anti-endothelial NOS. Using size-exclusion chromatography, a fraction with a molecular mass of about 185 kDa that had diaphorase activity was eluted from tick salivary gland homogenate. This fraction converted arginine to citrulline with the production of nitric oxide (NO), which was detected by using electron spin resonance spectroscopy. The complete activity of the diaphorase fraction was dependent on NADPH, FAD, tetrahydrobiopterin, calmodulin, (CaM), and Ca(2+), but was not dependent on dithiothreitol. The arginine analog N(G)-monomethyl-L-arginine inhibited the activity of this fraction. NO and arginine activated soluble guanylate cyclase to produce cGMP in dopamine-stimulated isolated salivary glands. Dopamine-stimulated isolated salivary glands treated with tick saline containing either EDTA, the NOS inhibitor N(G)-nitro-L-arginine methyl ester, or the calcium/CaM binding inhibitor W-7 showed no increase in cGMP. The NO donor sodium nitroprusside significantly increased cGMP levels in unstimulated isolated salivary glands. A possible function for NO in salivation by this ixodid tick is discussed.

Animals↗
PubMed1995

Immunocytochemical mapping of FMRFamide-like peptides in the argasid tick Ornithodoros parkeri and the ixodid tick Dermacentor variabilis.

FMRFamide-like immunoreactivity was studied in the argasid tick Ornithodoros parkeri and the ixodid tick Dermacentor variabilis using immunocytochemistry based on the peroxidase-antiperoxidase method. FMRFamide-like immunoreactive cells are widely distributed in various regions of the tick synganglion including protocerebral, cheliceral, stomodeal, palpal, pedal I-IV, and opisthosomal regions in both species. However, there is one layer of immunoreactive cells located on the dorsal surface of the postoesophageal part of the synganglion that is found only in D. variabilis. Besides the immunoreactivity within the cell body and its axons, the neuropile and the neural lamella (the extracellular sheath of the synganglion) are rich in immunoreactive materials. Some coxal muscles are innervated by the FMRFamide-like immunoreactive processes of the nerve from the pedal ganglion.

Animals↗
PubMed1996

Preliminary studies on the effect of Anaplasma marginale antibodies ingested by Dermacentor andersoni ticks (Acari:Ixodidae) with their blood meal on infections in salivary glands.

The effect of Anaplasma marginale antibodies ingested with the tick blood meal was tested on infected male ticks that were allowed to feed on cattle immunized with the erythrocytic stage of A. marginale. The experiments were done in two trials. Trial 1 was done using splenectomized calves (two calves per treated and control groups) while ticks in trial 2 were fed on intact yearling cattle (four cattle per treated and control groups). The cattle were immunized with purified outer membrane proteins of erythrocyte-derived A. marginale using saponin (trial 1) or monophosphoryl lipid-A-trehalose dicorynomycolate adjuvant (trial 2). The corresponding control cattle received adjuvant only. All cattle were challenged using Dermacentor andersoni males infected as adults that were allowed to feed for 7 days. In trial 1, the ticks were allowed to feed a second time on susceptible calves to test whether exposure of ticks to immunized cattle affected their ability to transmit anaplasmosis. Infections in fed ticks were monitored by determining the infection rates in salivary glands with an A. marginale-specific RNA probe and light microscopy. Vaccine-derived antibodies ingested with the tick blood meal did not appear to affect the development of A. marginale in previously infected ticks. The infection rates in the salivary glands were not significantly different among ticks fed on immunized versus adjuvant control cattle. When the vaccine-exposed ticks in trial 1 were allowed to feed a second time on susceptible calves, the resulting clinical symptoms of anaplasmosis were similar to those of the controls. There was no statistically significant effect of tick exposure to the anti-erythrocytic stage antibody on the development of salivary gland infection or transmission of A. marginale by ticks.

Anaplasma↗
PubMed1994

Localization of insulin-like immunoreactivity in the synganglion of nymphal and adult Dermacentor variabilis (Acari: Ixodidae).

Immunocytochemical staining based on a peroxidase-antiperoxidase method showed neurosecretory cells (NSC) reactive to bovine insulin in five of 18 paraldehyde fuchsin-positive neurosecretory regions (NSR) in the synganglion of unfed adult Dermacentor variabilis. This is the first report of a neuropeptide in an ixodid tick. The insulin-specific immunoreactive cells included the posterior medial group of the protocerebral center, posterior group of dorsal opisthosomal center, anterior lateral group of the dorso-lateral cheliceral center, dorsal group of the frontal stomodeal center, and anterior group of the ventral palpal center. After feeding and mating, females no longer had immunoreactive cells in three of five NSR found in virgin, unfed females. However, two cells of the posterior group in dorsal opisthosomal center and anterior lateral group of the dorso-lateral cheliceral center remained immunoreactive throughout feeding. Fed, mated males continued to display immunoreactive cells in four of five NSR found in the virgin, unfed males. All developmental stages of nymphs examined had insulin-specific immunoreactive cells in two of the five NSR found in unfed adults, including two positively stained cells of the posterior group in dorsal opisthosomal center and anterior group of ventral palpal neurosecretory center.

Animals↗
PubMed1987

Ultrastructural localization of acetylcholinesterase in the synganglion of the tick, Dermacentor variabilis (Say).

Light- and electron-microscopic enzyme cytochemistry was used to localize acetylcholinesterase (AChE) activity in the synganglion (brain) of the tick Dermacentor variabilis. High AChE activity was observed throughout the neuropil as well as adjacent to most neuronal perikarya. Intracellular activity was not observed by light microscopy. By electron microscopy, reaction product was localized at the plasma membrane of glia and neurons. Enzyme activity was not associated with the olfactory globuli neurons. In other types of neurons, small amounts of reaction product were observed in the Golgi apparatus and nuclear envelope. Large neurosecretory neurons contained activity that appeared to be associated with deep invaginations of the plasma membrane as well as intracellular membranes. AChE activity was also associated with processes of both neurons and glia. In most peripheral nerves AChE activity was associated with virtually all axons. Clearly then, AChE is associated with glia and non-cholinergic neurons as well as with presumed cholinergic neurons. The widespread localization and large amounts of AChE in the tick brain exceeds that reported for other invertebrates and vertebrates. As has been suggested for other animals, AChE in the tick brain may have functions in addition to its known role in cholinergic neurotransmission.

Acetylcholinesterase↗
PubMed1987

The development of Amblyomma americanum and Dermacentor variabilis (Acari: Ixodidae) fed on rabbits immunized with tick hemolymph.

The possibility of interfering with the normal function of tick hemolymph using antihemolymph antibodies taken in with the bloodmeal, was investigated. Cell free hemolymph from replete Amblyomma americanum and Dermacentor variabilis ticks was used to immunize rabbits. Immunized rabbits developed high antihemolymph antibody titers (ca. 10(5)) and had no ill side effects. Rabbits were simultaneously infested with larvae, nymphs, and adult ticks. The biological performance of ticks fed on immunized rabbits was virtually identical to that of ticks fed on nonimmunized rabbits. Usually, the mean engorgement weights of nymphs and females and the weights of the egg masses of both species were slightly higher for ticks fed on the nonimmunized rabbits but differences were not significant (P greater than 0.05) due to a large standard deviation. The possibility of deactivating a single hemolymph component with specific antibodies is discussed.

Animals↗