Dermacentor Species Research Articles

Ixodid ticks (Acari: Ixodidae) infesting humans in Tokat Province of Turkey: species diversity and seasonal activity

Ixodid ticks (Acari: Ixodidae) are the major vectors of pathogens threatening animal and human health. Tokat Province, Turkey, is a suitable habitat for extended tick activity with its moderate climate and vegetation. In the present study, we surveyed humans visiting health centers to determine the species diversity, geographical distribution, and seasonal activity of ixodid ticks infesting them. Out of 5,999 adult ticks collected from humans from April to September, 2008, 800 ticks were identified to species, while the remaining were identified to genus according to their distinct morphological characteristics. Hyalomma marginatum, Hyalomma detritum, Rhipicephalus bursa, Rhipicephalus (Boophilus) annulatus, Haemaphysalis punctata, Dermacentor marginatus, and Ixodes laguri were the most prevalent tick species among 24 ixodid tick species infesting humans in the region. One of these tick species, Hyalomma isacii was identified as a new record for the ixodid tick fauna of Turkey. Hyalomma species were the most abundant in summer, while Dermacentor and Ixodes species displayed the lowest frequency. Hyalomma aegyptium infestation was very common on humans in the province. Results indicated that a variety of ixodid tick species infest humans depending on the season in the target area. It is possible that a variety of ixodid tick species may contribute to the spread of tick-borne diseases such as Crimean-Congo haemorrhagic fever virus (CCHFV), which is endemic in the region.

Transport of Ticks by Migratory Passerine Birds to Norway

Ticks can be transported over large distances and across geographical barriers by avian hosts. During the spring migrations of 2003 to 2005, 9,768 passerine birds from 4 bird observatories along the southern coastline of Norway were examined for ticks. Altogether, 713 birds carried a total of 517 larvae and 1,440 nymphs. The highest prevalence of tick infestation was observed in thrushes and dunnock (Prunella modularis). The degree of tick infestation varied during each season, between localities, and from year to year. Blackbirds (Turdus merula) caught in localities with many ticks had greater infestation than those from localities with few or no ticks, suggesting local tick recruitment. A similar study performed during 1965–1970 involving 2 of the bird observatories in the present study found ticks on 4.2% of birds, while we found infestation of 6.9% at the same localities (P < 0.001). With the exception of 10 nymphs and 1 larva, the predominant tick was Ixodes ricinus. Seven nymphs of Hyalomma rufipes and 1 larva of Dermacentor sp. were also found. No species of Dermacentor had previously been found in Norway.

Evaluation of Dermacentor species naturally infected with Rickettsia raoultii

In the present study, we investigated the efficiency of transovarial transmission and intensity of multiplication of three R. raoultii genotypes in four naturally-infected Dermacentor species. We used the method of experimental modelling of a natural cycle of the metamorphosis of vectors (MEMNCMv) that allows the study of the role of tick species as vectors of infectious agents, including rickettsiae.

Field Collection and Genetic Classification of Tick‐borne Rickettsiae and Rickettsiae‐like Pathogens from South Texas: Coxiella burnetii Isolated from Field‐collected Amblyomma cajennense

We are reporting the first known isolation of the Q-fever agent Coxiella burnetii from field-collected cayenne ticks Amblyomma cajennense in North America. Q-fever affects a number of domestic ungulates where it can lead to abortion in sheep and goats. There is far less known about the disease's effects on wild species, primarily because of the tendency of the disease to self resolve and to provide long-term immunity to subsequent infections. The first recovery of C. burnetii in North America was from the tick species Dermacentor andersoni. Since the original isolation C. burnetii has been recovered from five other North American tick species. The currently accepted mode for the majority of human infections is inhalation. The Centers for Disease Control and Prevention, Division of Viral and Rickettsial Diseases, Rickettsial Zoonoses Branch asserts the Q-fever agent as requiring as few as one organism to cause disease via inhalation in susceptible humans. However, with more and more isolations from ticks, evidence linking C. burnetii and ticks is mounting. The true role of tick species as competent vectors is still unconfirmed. Preemptive field collections of possible vector arthropods, hosts, and reservoirs can provide invaluable baseline environmental data that will prove supportive in follow-up studies and abatement efforts.

Detection and Identification of Spotted Fever Group Rickettsiae in Dermacentor Species from Southern California

Detection and Identification of Spotted Fever Group Rickettsiae in Dermacentor Species from Southern California

Detection and Identification of Spotted Fever Group Rickettsiae in &lt;I&gt;Dermacentor&lt;/I&gt; Species from Southern California

Dermacentor occidentalis Marx and Dermacentor variabilis (Say) commonly bite humans in California. These Dermacentor species may play a role in transmitting spotted fever group (SFG) rickettsiae to humans in many parts of the state where Dermacentor andersoni Stiles, a known vector for the etiologic agent of Rocky Mountain spotted fever, Rickettsia rickettsii, is absent. However, the specific rickettsial agents present in these ticks and their current prevalence are poorly understood. In total, 365 D. occidentalis and 10 D. variabilis were collected by flagging vegetation at 16 sites in five counties of southern California. The presence of SFG rickettsial DNA in these ticks was detected with rOmpA and GltA gene polymerase chain reaction (PCR) assays. The rickettsial species were identified by sequencing PCR amplicons. Of 365 D. occidentalis, 90 (24.7%) contained R. rhipicephali DNA, 28 (7.7%) contained DNA of unclassified genotype 364D, two (0.55%) contained R. bellii DNA, and one (0.3%) contained R. rickettsii DNA. Of 10 D. variabilis, four (40%) contained only R. rhipicephali. Four new genotypes of R. rhipicephali were discovered. For the first time, we detected R. rickettsii in D. occidentalis. Our study provides the first molecular data on the prevalence and species identification of SFG rickettsiae circulating in populations of these California ticks. Because neither D. variabilis nor R. rickettsii were abundant, 364D should be evaluated further as a potential cause of human SFG rickettsioses in southern California.

Molecular identification of Anaplasma marginale and rickettsial endosymbionts in blood-sucking flies (Diptera: Tabanidae, Muscidae) and hard ticks (Acari: Ixodidae)

In an attempt to identify the main vector and possible transmission routes of Anaplasma spp. in a region of Hungary with high prevalence of ovine and bovine anaplasmosis, DNA was extracted from 316 haematophagous arthropods (individually or in pools), including 4 species of ixodid ticks, 6 species of tabanid flies and hornflies. Midichloria-like organisms were identified with PCR (amplifying a portion of the 16S rRNA gene) and sequencing from Dermacentor marginatus and Ixodes ricinus. Significantly higher 16S positive D. marginatus individuals were collected in March than in April, suggesting earlier questing of ticks that contain rickettsial agents (thus endosymbionts). Midichloria- and Wolbachia-like organisms were also found in randomly caught horse flies ( Tabanus bovinus and T. tergestinus) as well as hornflies ( Haematobia irritans), respectively, with 97–99% similarity to sequences deposited in the GenBank. Although all ticks were negative in the Anaplasma spp.-specific msp4 PCR, four individuals of T. bovinus collected near to grazing cattle were positive for Anaplasma marginale. The results of the present study provide the first molecular evidence for the potential mechanical vector role of T. bovinus in the transmission of A. marginale, and broaden the range of haematophagous arthropods harbouring Midichloria-like bacteria, for the first time in any Dermacentor or Tabanus species.

Differentiation of three species of ixodid tick, Dermacentor andersoni, D. variabilis and D. albipictus, by PCR-based approaches using markers in ribosomal DNA

Three species of Dermacentor, Dermacentor albipictus, Dermacentor andersoni and Dermacentor variabilis, commonly occur in Canada. D. andersoni and D. variabilis are morphologically similar and are important vectors of human and animal pathogens. A practical polymerase chain reaction (PCR) assay, based on the amplification of part of the second internal transcribed spacer ribosomal DNA (pITS-2 rDNA), was developed to distinguish D. andersoni from D. variabilis. In addition, single-strand conformation polymorphism (SSCP) analysis of the pITS-2 rDNA provided a reliable method of distinguishing specimens of the three species of ixodid tick. PCR and pITS-2 SSCP were also used to determine whether there was hybridization between D. andersoni and D. variabilis at two localities in Saskatchewan where they occur in sympatry. These molecular tools will be useful for the unequivocal identification of D. andersoni and D. variabilis at all life cycle stages, which is essential for studies on their ecology and on the transmission of tick-borne diseases. Also, pITS-2 SSCP may be of potential use for discriminating among the other morphologically similar species within the genus Dermacentor.

Importation of the New World tick species Dermacentor albipictus with a horse from the USA into Germany

Importation of the New World tick species Dermacentor albipictus with a horse from the USA into Germany

Ticks (Ixodidae) on humans in South America

Twenty eight species of Ixodidae have been found on man in South America (21 Amblyomma, 1 Boophilus, 2 Dermacentor, 2 Haemaphysalis, 1 Ixodes and 1 Rhipicephalus species). Most of them are rarely found on man. However, three species frequently parasitize humans in restricted areas of Argentina (A. neumanni reported from 46 localities), Uruguay (A. triste from 21 sites) and Argentina-Brazil (A. parvum from 27 localities). The most widespread ticks are A. cajennense (134 localities in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela), A. ovale (37 localities in Argentina, Brazil, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela) and A. oblongoguttatum (28 sites in Brazil, Colombia, French Guiana, Guyana, Suriname and Venezuela). Amblyomma aureolatum (18 localities in Argentina, Brazil, French Guiana and Paraguay), A. cajennense, and A. triste are vectors of rickettsioses to man in South America. A better understanding of the respective roles of these and other tick species in transmitting pathogens to humans will require further local investigations. Amblyomma ticks should be the main subjects of these studies followed by species of Boophilus, Dermacentor, Haemaphysalis and Rhipicephalus species. In contrast with North America, Europe and Asia, ticks of the genus Ixodes do not appear to be major players in transmitting diseases to human. Indeed, there is only one record of an Ixodes collected while feeding on man for all South America.

Rocky Mountain Spotted Fever from an Unexpected Tick Vector in Arizona

Rocky Mountain spotted fever is a life-threatening, tick-borne disease caused by Rickettsia rickettsii. This disease is rarely reported in Arizona, and the principal vectors, Dermacentor species ticks, are uncommon in the state. From 2002 through 2004, a focus of Rocky Mountain spotted fever was investigated in rural eastern Arizona. We obtained blood and tissue specimens from patients with suspected Rocky Mountain spotted fever and ticks from patients' homesites. Serologic, molecular, immunohistochemical, and culture assays were performed to identify the causative agent. On the basis of specific laboratory criteria, patients were classified as having confirmed or probable Rocky Mountain spotted fever infection. A total of 16 patients with Rocky Mountain spotted fever infection (11 with confirmed and 5 with probable infection) were identified. Of these patients, 13 (81 percent) were children 12 years of age or younger, 15 (94 percent) were hospitalized, and 2 (12 percent) died. Dense populations of Rhipicephalus sanguineus ticks were found on dogs and in the yards of patients' homesites. All patients with confirmed Rocky Mountain spotted fever had contact with tick-infested dogs, and four had a reported history of tick bite preceding the illness. R. rickettsii DNA was detected in nonengorged R. sanguineus ticks collected at one home, and R. rickettsii isolates were cultured from these ticks. This investigation documents the presence of Rocky Mountain spotted fever in eastern Arizona, with common brown dog ticks (R. sanguineus) implicated as a vector of R. rickettsii. The broad distribution of this common tick raises concern about its potential to transmit R. rickettsii in other settings.

Phylogenetic Analysis of theFrancisella-like Endosymbionts ofDermacentorTicks

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.

Molecular cloning, expression and isolation of ferritins from two tick species— Ornithodoros moubata and Ixodes ricinus

Genes encoding ferritins were isolated and cloned from cDNA libraries of hard tick Ixodes ricinus and soft tick Ornithodoros moubata. Both tick ferritins are composed of 172 amino-acid residues and their calculated mass is 19,667.2 Da and 19,974.5 Da for I. ricinus and O. moubata, respectively . The sequences of both proteins are closely related to each other as well as to the ferritin from another tick species Dermacentor variabilis (>84% similarity) . The proteins contain the conserved motifs for ferroxidase center typical for heavy chains of vertebrate ferritins. The stem-loop structure of a putative iron responsive element was found in the 5′ untranslated region of ferritin mRNA of both ticks. Antibodies against fusion ferritin from O. moubata were raised in a rabbit and used to monitor the purification of a small amount of ferritins from both tick species. The authenticity of ferritin purified from O. moubata was confirmed by mass-fingerprinting analysis. In the native state, the tick ferritins are apparently larger (~500 kDa) than horse spleen ferritin (440 kDa). On SDS-PAGE tick ferritins migrate as a single band of about 21 kDa. These results suggest that tick ferritins are homo-oligomers of 24 identical subunits of heavy-chain type. The Northern blot analysis revealed that O. moubata ferritin mRNA level is likely not up-regulated after ingestion of a blood meal.

Geographic distribution of ticks (Acari: Ixodidae) in Michigan, with emphasis on Ixodes scapularis and Borrelia burgdorferi.

A 12-yr (1985-1996) passive survey in Michigan based upon tick submissions from citizens yielded 4,755 ticks of 21 species, 16 of which were probably indigenous in the state. Three species of Dermacentor [most common, D. variabilis Say and D. albipictus (Packard)]; 2 species of Amblyomma [most common, A. americanum (L.)]; and 12 species of Ixodes (most common, I. cookei Packard and I. scapularis Say), as well as Haemaphysalis leporispalustris (Packard), Rhipicephalus sanguineus Latreille, and the soft ticks Ornithodoros kelleyi Cooley & Kohls, and Otobius megnini (Duges) were submitted. New state records were I. kingi Bishopp, I. texanus Banks, I. sculptus Neumann, and I. baergi Cooley & Kohls. Examination of gut smears from dissections of 1,037 ticks of 13 species by indirect immunofluorescent assay, using murine monoclonal H9724 as the primary antibody, revealed that 11 of 175 I. scapularis were infected with Borrelia spp. All positive I. scapularis were from Menominee County in the upper peninsula of the state, which also provided 79.8% of all submitted I. scapularis. Surveys for ticks on 5,449 hunter-killed white-tailed deer were conducted from 1988 to 1990, encompassed deer taken from 65 of the state's 83 counties, and showed that although D. albipictus was distributed widely in the northern part of the state, I. scapularis occurred only on deer taken from southern townships of Menominee County. Of 1,218 canine sera tested for antibodies to B. burgdorferi in 1992 and 1993, 25 of 299 (8.0%) from Menominee County were positive but only 1 of 919 sera submitted from 5 counties in the lower peninsula was positive.

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.

Role of genital sex pheromones inAmblyomma americanum andA. maculatum (Acari: Ixodidae)

Amblyomma americanum and A. maculatum were studied to determine if genital sex pheromones were present, as reported in Dermacentor species. Chemical analysis of methanol extracts of the anterior reproductive tracts (source of the genital sex pheromone) of A. americanum and A. maculatum confirmed the presence of the same fatty acids that act as components of the genital sex pheromone in Dermacentor variabilis and D. andersoni. In both Amblyomma species, removal of the anterior reproductive-tract of fed females eliminated the male copulatory response. For A. americanum, use of anterior reproductive tract extracts made with water, methanol, ether and hexane elicited significant probing and copulatory responses by conspecific males. However, in A. maculatum, use of anterior reproductive-tract extracts made with water, methanol, ether, chloroform:methanol (4:1), hexane and pentane did not restore mating response by males. Treatment with known components of Dermacentor genital sex pheromones elicited weak but significant responses in A. americanum, but did not restore male mating responses in A. maculatum. These results indicate that genital sex pheromones exist in A. americanum and are not restricted to the genus Dermacentor. Characteristics of the Amblyomma genital sex pheromone, however, do differ considerably from those in Dermacentor. No genital sex pheromone was present in A. maculatum.

Cytosystematics of Five North American Dermacentor (Acari: Ixodidae) Species

The karyotypes of five species of Dermacentor ticks found in North America were examined for the presence and location of constitutive heterochromatin (C-bands) and the location of the nucleolar organizing regions (NORs). All specimens examined had 20 autosomes and an XX:XO sex-determining system; the X was the largest element in the karyotype. Except as noted, the autosomes of all species were acrocentric, and heterochromatin was restricted to the centromeric region. The one-host species D. nitens and D. albipictus were distinguished from the three-host species by a lack of additional bands of heterochromatin and by having a subtelocentric X chromosome. However, some individuals of D. albipictus were observed to have acrocentric X chromosomes. D. nitens differed from D. albipictus in having two subtelocentric autosomal pairs (pairs 1 and 8). A single pair of NORs was noted for the one-host species; however, heterochromatin was not associated with the NORs. Among the three-host species, D. occidentalis showed a band of heterochromatin proximal to the centromere in autosomal pairs 1 and 8, and D. andersoni had similar bands in autosomal pairs 1, 3, 7, and 9. D. variabilis displayed heterochromatic bands in autosomal pairs 3, 7, and 9. All three-host species displayed a single pair of NORs, which was associated with the band of heterochromatin on pair 9. Indications of some genetic incompatibility between the two recognized forms of D. albipictus are discussed.

Absence of assembly pheromones in the hard ticks Dermacentor variabilis and Dermacentor andersoni (Acari: Ixodidae).

There was no evidence of response to an assembly pheromone when male and female Dermacentor variabilis (Say) and Dermacentor andersoni Stiles were exposed in petri dish assays to filter paper circles contaminated by other ticks (either conspecific or heterospecific), hexane extracts of ticks, tick feces, or tick excreta. These ticks did not assemble in response to the presence of other living ticks. Significant responses to saline extracts occurred in both species. However, D. variabilis did not respond to conspecific saline extracts of the same sex and D. andersoni males did not respond to conspecific saline extracts of females. D. variabilis males and females responded to filter paper circles contacted by conspecific ticks of the same sex, but not to those contacted by any other types. D. variabilis females also responded to saline controls. Ticks allowed to climb rods of a simulated “meadow” did not cluster in response to the presence of other live ticks or rods previously contaminated by ticks. These results do not support the hypothesis of an assembly pheromone in D. variabilis or D. andersoni . Contrasts between the ecology of the two North American Dermacentor species and those ticks for which assembly pheromones have been reported are discussed.

Arthropod vectors of human disease in the United States

Arthropod vectors of human disease in the United States

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.