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At least 19 recordsLinked to original sources
PubMed1998

DNA sequence variation in Dermacentor hunteri and estimated phylogenies of Dermacentor spp. (Acari: Ixodidae) in the New World.

The genus Dermacentor is represented by 12 species in the New World. We sequenced a 300-bp portion of the mitochondrial 16S ribosomal DNA gene for 28 individual ticks representing 9 of these species and analyzed their phylogenetic relationships. Maximum parsimony, distance (neighbor-joining), and maximum likelihood were all used to resolve tree topologies. Eleven specimens of Dermacentor hunteri Bishopp representing populations across the tick's entire geographic range showed negligible genetic variation, with only single base-pair differences between each of 5 haplotypes. We found high degrees of bootstrap support (66-86%) for monophyly of the genus, but variable support for monophyly of species within the genus. D. hunteri, D. occidentalis Marx, and D. variabilis (Say) each resolved as a monophyletic taxon (79-99% support). D. andersoni Stiles and D. parumapertus Neumann formed a paraphyletic clade (99% support). D. albipictus Packard showed substantial intraspecific variation and warrants further investigation. D. imitans Warburton was distinct from all other Dermacentor spp. on all trees.

Animals↗
PubMed1998

Optimal sampling and spatial distribution of Ixodes pacificus, Dermacentor occidentalis and Dermacentor variabilis ticks (Acari: Ixodidae).

A common method for sampling tick populations is flagging, which is a method of dragging a white cloth over a plant substrate for a fixed distance along a transect. Flagging over rough physical surfaces or using long subtransect lengths could lead to the underestimation of tick densities. Using estimates of the drop-off rates of adult Ixodes pacificus in flag sampling, optimal sampling schemes (the length and number of subtransects) were examined using the relationships between the tick drop-off rates (c), the tick density and distribution patterns and the roughness of the sampled plant substrate. It was found that the optimal number of subtransects and Lmax, the longest subtransect length which did not significantly underestimate the tick density from c, were affected by the tick density, substrate roughness and tick distribution pattern. This study also showed that the density and distribution of I. pacificus and Dermacentor occidentalis varied greatly over time in the populations sampled, while the Dermacentor variabilis densities were low and showed no significant changes over time. Both I. pacificus and D. occidentalis had clumped distributions along trails and these clumps were aggregated. However, the clump sizes (or individual clump areas) changed significantly over time because of density fluctuation or the movement of ticks. Finally, a positive association between the number of I. pacificus and D. occidentalis adults was observed from 2 m subtransect flag collections in March 1995; no relationship was found in 1994.

Animals↗
PubMed1982

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.

Animals↗
PubMedDate not supplied

Evidence for the reproductive isolation of Dermacentor marginatus and Dermacentor reticulatus (Acari: Ixodidae) ticks based on cross-breeding, morphology and molecular studies.

The species status of Dermacentor marginatus and Dermacentor reticulatus was evaluated by scanning electron microscope (SEM) examination of adult ticks, cross-breeding experiments and molecular biological analysis of eggs derived from transspecific pairings. The SEM investigations including the morphometric quantification of phenotypic features resulted in an unequivocal differentiation of adult D. marginatus and D. reticulatus ticks. The cross-breeding experiments demonstrated that irrespective of whether female ticks of both species were applied with con- or transspecific male ticks or without males to sheep, they engorged and laid eggs. The larvae, however, developed only in eggs which originated from conspecific matings. A nested polymerase chain reaction (PCR) of the second internal transcribed spacer (ITS2) using the DNA of eggs from transspecific pairings and sequencing of the PCR products revealed two different genotypes. The genotypes of eggs originating from D. marginatus and D. reticulatus females of these pairings differed. However, the eggs deposited by D. marginatus always possessed the same two genotypes as did the eggs produced by D. reticulatus. These results argue for a strict reproductive isolation of D. marginatus and D. reticulatus and, therefore, for a separate species status.

Animals↗
PubMed1976

[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.

Animals↗
PubMed1980

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↗
PubMed1981

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↗
PubMed2004

Phylogenetic analysis of the Francisella-like endosymbionts of Dermacentor ticks.

Bacterial endosymbionts with significant homology to Francisella tularensis (gamma-proteobacteria) have been described from at least five species of ticks in three different genera, including two North American Dermacentor species [D. andersoni Stiles and D. variabilis (Say)]. The evolutionary relationships among the Francisella-like endosymbionts (FLE) from different hosts and between FLE and the arthropod-borne pathogen F. tularensis are not known. A 1,169-base fragment of the 16s rDNA and a 713-base fragment of the F. tularensis 17-kDa lipoprotein gene homolog of the FLE of six North American Dermacentor tick species [D. anderson, D. variabilis, D. albipictus (Packard), D. occidentalis Marx, D. hunteri Bishopp, and D. (Anocentor) nitens Neumann] and of Amblyomma maculatum Koch and Ornithodoros porcinus (Murry 1877, sensu Walton 1979) as outgroups, were subjected to phylogenetic analysis. These gene phylogenies were compared with a phylogeny of the same tick species constructed from a 435-base fragment of the tick mitochondrial 16s rDNA. Although the phylogenies of the FLE and their tick hosts are parallel at the genus level, the Dermacentor FLE are unresolved at the species level. The FLE and the Dermacentor ticks show little sign of co-speciation, possibly indicating that the association between these endosymbiont and the Dermacentor ticks is of a relatively recent origin. Several ticks were co-infected, either with two FLE with divergent 17-kDa lipoprotein gene sequences or with FLE and an unidentified species of spotted fever group rickettsia (alpha-proteobacteria). Infection with FLE does not seem to have precluded infection with either a second closely related gamma-proteobacterial symbiont or with a second less closely related alpha-proteobacterial symbiont.

Animals↗
PubMed2004

Immune-responsive lysozymes from hemocytes of the American dog tick, Dermacentor variabilis and an embryonic cell line of the Rocky Mountain wood tick, D. andersoni.

Immune-responsive lysozyme encoding cDNAs were identified from two medically important tick species by an expressed sequence tag approach of D. variabilis hemocytes (Dv Lys) and a D. andersoni embryonic derived cell line, DAE100. Comparative sequence analyses indicated the Dermacentor molecules to be products of orthologous genes and to be most similar to arthropod c-type lysozymes. Northern blotting analyses demonstrated that Dv Lys expression levels were most abundant in tick hemocytes and to a much lesser degree in the midgut while barely detectable in ovary, salivary gland, and Malpighian tubule tissues. Involvement of the Dermacentor c-type lysozymes in innate immunity was demonstrated by Escherichia coli challenges of D. variabilis ticks by injection resulting in a temporal profile of significantly elevated transcript abundances above those of naive controls that was similarly observed of the D. andersoni cells co-cultured with E. coli. In contrast to that reported of the digestive gut lysozyme of the soft tick Ornithodoros moubata, Dv Lys levels were not statistically differentially regulated by blood meal digestion. Additionally, given the differences in tissue distribution, sequence characteristics and phylogenetic placements between the Dermacentor and Ornithodoros lysozymes demonstrates that ticks possess differently adapted c-type lysozymes that are spatially and temporally differentially expressed.

Amino Acid Sequence↗
PubMed2005

A new Francisella (Beggiatiales: Francisellaceae) inquiline within Dermacentor variabilis say (Acari: Ixodidae).

While estimating the prevalence of the Dermacentor variabilis (Say) symbiont (DVS) in dog ticks on Martha's Vineyard, MA, we identified DNA that may represent a heretofore unrecognized Francisella sp. Polymerase chain reaction targeting a portion of the 16S rDNA specific for DVS yielded an amplicon that was only 96.6% similar to that of DVS accessioned in GenBank. Phylogenetic analysis of the 16S and 23S rDNA genes suggests the presence of a distinct bacterium closely related to the other endosymbionts of Dermacentor spp. Fifty-five percent of dog ticks tested from three sites in Massachusetts showed evidence of infection with this new agent, called Dermacentor variabilis francisella (DVF), whereas 100% tested positive for DVS. All larval progeny of dog ticks known to contain DVF also showed evidence of colonization, demonstrating that this agent may be maintained by transovarial transmission. Coinfection of ticks with both Francisella species did not seem to interfere with transmission.

Animals↗
PubMed1994

Identification of spotted fever group rickettsiae isolated from Dermacentor marginatus and Ixodes ricinus ticks collected in Switzerland.

When 155 ticks collected in different regions of Switzerland were tested by the hemolymph test, 10.3% were found to contain spotted fever group rickettsiae. Six rickettsial isolates were made from Dermacentor marginatus ticks and three were made from Ixodes ricinus ticks. The polymerase chain reaction followed by restriction fragment length polymorphism analysis showed that the Dermacentor ticks were infected with Rickettsia length polymorphism analysis showed that the Dermacentor ticks were infected with Rickettsia slovaca and the Ixodes ticks were infected with a spotted fever group rickettsia. Microimmunofluorescence serologic type, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins, and Western blot assay with polyclonal mouse antisera confirmed the results and determined that the Ixodes were infected with R. helvetica, the only previously described Swiss rickettsia. However, an additional new strain that could not be isolated was detected in one I. ricinus by hemolymph test and provisionally characterized by enzymatic restriction of its amplified DNA.

Animals↗
PubMed1988

[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.

Animals↗