Evidence for competition between Ixodes scapularis and Dermacentor albipictus feeding concurrently on white-tailed deer

Competition among ticks, and among ectoparasites generally, has rarely been demonstrated. Ixodes scapularis and Dermacentor albipictus are both hard ticks commonly found feeding on deer harvested at Letterkenny Army Depot, in south central Pennsylvania, USA. The two species have contrasting life histories resulting in D. albipictus spending notably more time on the shared host. We hypothesized that this would give D. albipictus an advantage in locating and occupying optimal attachment sites (highly vascularized areas like the head and ears). Ticks were collected from 224 hunter-killed deer in December 2005 and November 2006 to determine if there is evidence of competition for attachment sites when these two species concurrently infest deer. A timed sample (3?min per region) of representative ticks was collected from the head (ears, face and neck regions) and body (axillae regions). Ixodes scapularis was more abundant and prevalent overall than D. albipictus. Dermacentor albipictus was found almost exclusively on the head, whereas I. scapularis was more evenly distributed, but somewhat more abundant on the body than on the head. The proportion of I. scapularis on the head was reduced at high D. albipictus abundances, but I. scapularis abundance did not alter the distribution of D. albipictus. This study supports the hypothesis of competition for preferred attachment sites between these two species of ticks, and suggests that D. albipictus may be competitively dominant over I. scapularis on the head region of concurrently infested white-tailed deer.     

Widespread dispersal of Borrelia burgdorferi-infected ticks collected from songbirds across Canada

Millions of Lyme disease vector ticks are dispersed annually by songbirds across Canada, but often overlooked as the source of infection. For clarity on vector distribution, we sampled 481 ticks (12 species and 3 undetermined ticks) from 211 songbirds (42 species/subspecies) nationwide. Using PCR, 52 (29.5%) of 176 Ixodes ticks tested were positive for the Lyme disease spirochete, Borrelia burgdorferi s.l. Immature blacklegged ticks, Ixodes scapularis , collected from infested songbirds had a B. burgdorferi infection prevalence of 36% (larvae, 48%; nymphs, 31%). Notably, Ixodes affinis is reported in Canada for the first time and, similarly, Ixodes auritulus for the initial time in the Yukon. Firsts for bird-parasitizing ticks include I. scapularis in Quebec and Saskatchewan. We provide the first records of 3 tick species cofeeding on passerines (song sparrow, Swainson's thrush). New host records reveal I. scapularis on the blackpoll warbler and Nashville warbler. We furnish the following first Canadian reports of B. burgdorferi-positive ticks: I. scapularis on chipping sparrow, house wren, indigo bunting; I. auritulus on Bewick's wren; and I. spinipalpis on a Bewick's wren and song sparrow. First records of B. burgdorferi-infected ticks on songbirds include the following: the rabbit-associated tick, Ixodes dentatus, in western Canada; I. scapularis in Quebec, Saskatchewan, northern New Brunswick, northern Ontario; and Ixodes spinipalpis (collected in British Columbia). The presence of B. burgdorferi in Ixodes larvae suggests reservoir competency in 9 passerines (Bewick's wren, common yellowthroat, dark-eyed junco, Oregon junco, red-winged blackbird, song sparrow, Swainson's thrush, swamp sparrow, and white-throated sparrow). We report transstadial transmission (larva to nymph) of B. burgdorferi in I. auritulus. Data suggest a possible 4-tick, i.e., I. angustus, I. auritulus, I. pacificus, and I. spinipalpis, enzootic cycle of B. burgdorferi on Vancouver Island, British Columbia. Our results suggest that songbirds infested with B. burgdorferi-infected ticks have the potential to start new tick populations endemic for Lyme disease. Because songbirds disperse B. burgdorferi-infected ticks outside their anticipated range, health-care providers are advised that people can contract Lyme disease locally without any history of travel.     

Host associations of ticks parasitizing rodents at Borrelia burgdorferi enzootic sites in South Carolina.

A total of 237 rodents was collected in 4 regions of South Carolina from July 1994 through December 1995. Eight species were collected, including cotton mouse, hispid cotton rat, eastern woodrat, marsh rice rat, white-footed mouse, eastern harvest mouse, golden mouse, and black rat. Of the 1,514 ticks recovered from these hosts, Ixodes minor Neumann, including larvae, nymphs, and adults, was the most abundant species, representing 54% of the total. Only immature stages of other tick species were found, including larvae and nymphs of Dermacentor variabilis (Say), Amblyomma maculatum Koch, Ixodes affinis Neumann, and Ixodes scapularis Say. All 5 tick species parasitized cotton mice, cotton rats, and woodrats, which were the most important small mammal hosts for ticks at the localities studied. Rice rats were hosts of A. maculatum, D. variabilis, and L. minor. Amblyomma maculatum was more strongly associated with cotton rats than other rodent species. Ixodes scapularis was most strongly associated with cotton mice, and I. minor was more strongly associated with both woodrats and cotton mice than other species of rodents. Ixodes minor parasitized hosts in the Coastal Zone only, where among spirochete-infected hosts, it was present in significantly greater numbers than other ticks. Furthermore, I. minor was the only tick species that showed a statistically significant positive association with spirochetal infection in rodents. More I. affinis parasitized spirochete-infected hosts than I. scapularis, but fewer than I. minor. The findings discussed herein provide evidence that implicates I. minor as the possible primary enzootic vector of the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt and Brenner in the Coastal Zone of South Carolina. They also indicate that the high level of B. burgdorferi infection in rodents from this region may be a function of the combined involvement of I. minor, I. affinis, and I. scapularis in the enzootic transmission of the spirochete.     

Salivary gland antigens of Ixodes dammini are glycoproteins that have interspecies cross-reactivity.

Serum from rabbits and rats exposed to Ixodes dammini adults and larvae, respectively, contain antibodies to a large number of antigens in salivary gland homogenates from adult ticks that cross react with the antigens of a closely related species, Ixodes scapularis, and significantly with Dermacentor variabilis antigens. The salivary gland antigens of I. dammini are glycoproteins composed of both N- and O-linked carbohydrate chains. The antigenic determinants reside in both the polypeptide and carbohydrate chains.     

Spirochetes in ticks and antibodies to Borrelia burgdorferi in white-tailed deer from Connecticut, New York State, and North Carolina

Ticks were screened for spirochetes and serum samples from white-tailed deer (Odocoileus virginianus) were assayed for antibodies to Borrelia burgdorferi during 1983-1984. Using fluorescein isothiocyanate-labeled rabbit antibodies produced to B. burgdorferi, the etiologic agent of Lyme disease, spirochetes were detected in Ixodes dammini (10.5% of 1,193) and Dermacentor albipictus (0.6% of 157) adults from Connecticut, I. dammini nymphs (49.1% of 108) and adults (64.7% of 99) from Armonk, New York, and in I. scapularis (0.4% of 531) and Amblyomma americanum (3.5% of 173) adults from North Carolina. Infected ticks were either seeking hosts or feeding on deer during the summer and fall. Direct fluorescent antibody staining also revealed spirochetes in two larvae of I. scapularis that emerged from eggs deposited by separate females in the laboratory. Using indirect immunofluorescence tests, antibodies to B. burgdorferi were identified in white-tailed deer living in tick-infested areas of all three states. Aside from minor cross-reactivity, there was no serologic evidence of Treponema or Leptospira infections. Ixodes dammini is a primary vector of B. burgdorferi in northeastern United States, but in North Carolina, other ixodid ticks may transmit this spirochete to humans and wildlife.     

The meadow tick Dermacentor reticulatus in natural foci of tick-borne encephalitis in Udmurtia

In southern Udmurtia, where occur both Dermacentor reticulatus and Ixodes persulcatus, in the years of high abundance of small mammals feeding periods of larvae and nymphs of these ticks coincide completely. The duration of simultaneous parasitism of preimago of the above ixodid species on animals is of epidemiological significance as far as within this period the infection of young stages of D. reticulatus with the virus of tick-borne encephalitis occurs. This is confirmed by the isolation of I strain of the virus from D. reticulatus collected at the state of engorged nymphs on hosts common with I. persulcatus and moulted in the laboratory.     

Relative importance of lizards and mammals as hosts for ixodid ticks in northern California

Lizards and mammals were trapped and examined for ticks from August 1992 to June 1993 in two habitat types, chaparral and woodland-grass, in northern California. Five tick species were collected from mammals (Dermacentor occidentalis, Haemaphysalis leporispalustris, Ixodes pacificus, I. spinipalpis, I. woodi), but only I. pacificus was found on lizards. Dermacentor occidentalis, I. pacificus, and I. woodi occurred in both habitats, whereas H. leporispalustris and I. spinipalpis were found only on animals trapped in chaparral. The tick species most commonly encountered on mammals was D. occidentalis in chaparral and I. pacificus in woodland-grass. Peak infestation of mammals occurred in spring for I. pacificus immatures and H. leporispalustris, summer for D. occidentalis immatures, fall through spring for I. woodi immatures, and fall through winter for I. spinipalpis. The primary aim of the study was to quantify the relative importance of the western fence lizard (Sceloporus occidentalis), which is reservoir-incompetent for Borrelia burgdorferi sensu lato (s.l.), and mammalian B.burgdorferi s.l.-reservoirs as hosts for the immature stages of I. pacificus in spring. The estimated relative utilization by I. pacificus of the western fence lizard versus mammals was 88% for larvae and 99% for nymphs in chaparral in May. When tick infestation data were corrected for a two-fold lower efficiency of field examinations for rodents than for lizards, the western fence lizard still accounted for 78% of larval and 98% of nymphal feedings. In woodland-grass, 46% of 100 I. pacificus larvae and 100% of 52 nymphs recovered from mammals or western fence lizards during May-June were collected from the lizards. However, this may represent an underestimate of the importance of the western fence lizard as a larval host in this habitat because inclement weather during the late May sampling period doubtless resulted in significantly decreased lizard activity. In conclusion, the western fence lizard was more heavily utilized by I. pacificus immatures, especially nymphs, than were rodents. This revised version was published online in July 2006 with corrections to the Cover Date.     

Borrelia sp. in ticks recovered from white-tailed deer in Alabama.

Six hundred sixty-five hunter-killed white-tailed deer (Odocoileus virginianus) from 18 counties in Alabama (USA) were examined for ticks. Most of the collections were made at state-operated wildlife management areas. Four species of ticks (n = 4,527) were recovered: the lone star tick Amblyomma americanum (n = 482); the Gulf Coast tick A. maculatum (n = 11); the winter tick Dermacentor albipictus (n = 1,242); and the black-legged tick Ixodes scapularis (n = 2,792). Fifty-six percent of the ticks (n = 2,555) were examined for Borrelia sp. spirochetes using an immunofluorescent, polyclonal antibody assay. Spirochetes were detected in I. scapularis (five females, seven males) from Barbour, Butler, Coosa, and Lee counties and A. americanum (four males, four nymphs) from Hale, Lee, and Wilcox counties. Area-specific prevalences in ticks were as high as 3.3% for I. scapularis and 3.8% for A. americanum.     

Identification of novel tick salivary gland proteins for vaccine development

Methods currently used to control Ixodes scapularis ticks rely principally on acaricidal applications which suffer from a number of limitations. Recently, host vaccination against ticks has been shown to be a promising alternative tick control method. In tick salivary glands, numerous genes are induced during the feeding process. Many of these newly expressed proteins are secreted in tick saliva and may play a role in modulating host immune responses and pathogen transmission. We have performed suppression subtraction hybridization to identify unique I. scapularis salary gland proteins specifically expressed during engorgement. We have cloned and sequenced ten unique salivary gland-associated cDNAs that are up-regulated during feeding. The protein products of these genes represent potential vaccine candidates for use in the control of ticks and to prevent transmission of tick-borne diseases.     

Infestation of mammals by Ixodes ricinus ticks (Acari: Ixodidae) in south-central Sweden

Infestation by Ixodes ricinus ticks on rodents, hares and cervids was examined at Bogesund, 10 km north of Stockholm, in south-central Sweden during 1991-1994 and on varying hares (Lepus timidus) at Stora Karlso and Gotska Sandon in the Baltic Sea during 1992-1993. At Bogesund, there were great differences between two consecutive years in the number of I. ricinus larvae infesting bank voles (Clethrionomys glareolus). The seasonal pattern of infestation by I. ricinus larvae and nymphs on bank voles was unimodal in 1991, with peaks in June-July and bimodal in 1992, with peaks in June and August. Male bank voles, compared to females and older voles, compared to young voles, harboured greater numbers of I. ricinus ticks. Apodemus mice, compared to bank voles, harboured greater numbers of I. ricinus ticks. Ixodes ricinus larvae engorged on Apodemus mice were heavier than larvae engorged on bank voles and resulted in larger nymphs. However, there was no difference in the proportions of viable nymphs resulting from larvae engorged on mice or voles. The ranges in the numbers of I. ricinus ticks infesting individual hosts were 1-451 for rodents, 16-2374 for hares and 428-2072 for roe deer (Capreolus capreolus). These ranges of tick numbers are estimated to represent potential blood losses from individual hosts of approximately 0.2-65% for rodents, 0.2-13% for hares and 0.3-9.0% for roe deer. Within the populations of all host species examined, the distributions of all stages of I. ricinus were clumped, with most host individuals harbouring few ticks and only a few individuals harbouring many ticks. The data suggest that, even though a small proportion of tick hosts may be severely affected, the direct effects of feeding by I. ricinus are unlikely to play an important role on mammal population dynamics.     

Host usage and seasonal activity patterns of Ixodes kingi and I. sculptus (Acari: Ixodidae) nymphs in a Colorado prairie landscape, with a summary of published North American host records for all life stages.

We examined host usage and seasonal activity patterns of the nymphal stage of the ticks Ixodes kingi and I. sculptus within a prairie rodent community in north-central Colorado. Ixodes kingi was commonly encountered on both northern grasshopper mice (Onychomys leucogaster) and thirteen-lined ground squirrels (Spermophilus tridecemlineatus), whereas I. sculptus frequently infested S. tridecemlineatus but was absent from O. leucogaster. Low numbers of ticks of both species were collected from deer mice (Peromyscus maniculatus) and Ord's kangaroo rats (Dipodomys ordii). Nymphal loads of I. kingi and I. sculptus increased dramatically on commonly infested rodent species from spring (May-June) to summer (July-August). Further, rodents trapped on prairie-dog towns tended to experience increased nymphal loads of I. kingi (O. leucogaster, S. tridecemlineatus) but decreased loads of I. sculptus (S. tridecemlineatus) following plague epizootics among prairie dog populations. A summary of published North American host records revealed that I. kingi has been recorded from humans, domestic animals (cat, dog), 17 species of carnivores, 40 species of rodents, and four species of lagomorphs, and that I. sculptus has been recorded from humans, domestic animals (cat, dog, goat), 13 species of carnivores, 34 species of rodents, and three species of lagomorphs. In accordance with our observations from Colorado, I. kingi commonly has been found to infest heteromyid and murid rodents (such as grasshopper mice), whereas I. sculptus most frequently has been collected from ground-dwelling sciurid rodents, especially Spermophilus ground squirrels. The potential roles of I. kingi and I. sculptus as enzootic vectors of human pathogens, particularly the agents of tularemia (Francisella tularensis), Q fever (Coxiella burnetii), and Colorado tick fever (CTF virus), are discussed.     

Frequent isolation of Francisella tularensis from Dermacentor reticulatus ticks in an enzootic focus of tularaemia

Abstract. A total of 924 questing Dermacentor reticulatus (Fabricius), 504 Ixodes ricinus (L.), sixty Haemaphysalis concinna Koch and 718 mosquitoes (Aedes spp.) were examined in a floodplain forest ecosystem during the 1994-95 outbreak of tularaemia in South Moravia, Czech Republic. Francisella tularensis was not isolated from H.concinna ticks or Aedes spp. mosquitoes, whereas twenty-one isolates were recovered from the other haematophagous arthropods. Dermacentor reticulatus revealed a significantly higher infection rate (2.6%) than I.ricinus (0.2%). This tick species acts as principal vector for tularaemia in the enzootic focus. Monitoring of D.reticulatus for F.tularensis thus seems to be a very efficient approach in the surveillance of tularaemia in the flood-plain forest ecosystems of Europe.     

The ixodid tick species attaching to domestic dogs and cats in Great Britain and Ireland

The species of ixodid ticks, attached to dogs and cats presented to veterinary practices in Great Britain and Ireland were identified. Most host animals carried only one tick species with Ixodes ricinus Linné (Acari: Ixodidae) being the most common, identified on 52% of animals, Ixodes hexagonus Leach (Acari: Ixodidae) the second most common (on 39%) and Ixodes canisuga Johnston (Acari: Ixodidae) the third most common (on 11%). A significantly higher proportion of dogs than cats carried I. ricinus, while I. hexagonus was more frequently carried by cats. One animal carried a single specimen of Haemaphysalis punctata Canestrini & Fanzago (Acari: Ixodidae), one carried a Dermacentor reticulatus Fabricius (Acari: Ixodidae) but none carried Rhipicephalus sanguineus Latreille (Acari: Ixodidae). This indicates that the latter two species, vectors of 'exotic' tick-borne diseases, remain at low densities in Great Britain and Ireland. Retrospective information on exposure of the animals to different habitats and geographic regions was collected by questionnaire and subject to contingency table and logistic regression analysis. Woodlands and moorlands were habitats significantly associated with I. ricinus attachment. Exposure to urban parks was significantly associated with I. hexagonus attachment and exposure to boarding kennels and catteries was significantly associated with I. canisuga attachment. Ixodes hexagonus, rather than I. ricinus, was the ixodid tick species most likely to be encountered by urban populations of dogs and cats and, by inference, possibly also humans. The implications of these findings, for the transmission of tick-borne pathogens to dogs, cats and humans are discussed.     

The occurrence of ixodid ticks on wild mink Mustela visonin England and Wales

Abstract. Four species of ticks found to infest 1391 American mink (Mustela vison) in Britain in five years were, in declining order of frequency, Ixodes hexagonus, Ixodes canisuga, Ixodes ricinus and Ixodes acuminatus. Ixodes hexagonus and I.canisuga occurred on 40% and 2.5% of mink respectively. Infestation rates (the proportion of infested mink) of adult females, nymphs and larvae were similar and tended to be lower in summer. The distribution of infestation size (the number of ticks per host) for adult females describes a negative binomial. The mean infestation size of nymphs varied with the sex of the host and was 5.2 for males and 4.2 for females. Mink are competent hosts for /. hexagonus.     

Infection of Ixodes scapularis ticks with Rickettsia monacensis expressing green fluorescent protein: a model system

Ticks (Acari: Ixodidae) are ubiquitous hosts of rickettsiae (Rickettsiaceae: Rickettsia), obligate intracellular bacteria that occur as a continuum from nonpathogenic arthropod endosymbionts to virulent pathogens of both arthropod vectors and vertebrates. Visualization of rickettsiae in hosts has traditionally been limited to techniques utilizing fixed tissues. We report epifluorescence microscopy observations of unfixed tick tissues infected with a spotted fever group endosymbiont, Rickettsia monacensis, transformed to express green fluorescent protein (GFP). Fluorescent rickettsiae were readily visualized in tick tissues. In adult female, but not male, Ixodes scapularis infected by capillary feeding, R. monacensis disseminated from the gut and infected the salivary glands that are crucial to the role of ticks as vectors. The rickettsiae infected the respiratory tracheal system, a potential dissemination pathway and possible infection reservoir during tick molting. R. monacensis disseminated from the gut of capillary fed I. scapularis nymphs and was transstadially transmitted to adults. Larvae, infected by immersion, transstadially transmitted the rickettsiae to nymphs. Infected female I. scapularis did not transovarially transmit R. monacensis to progeny and the rickettsiae were not horizontally transmitted to a rabbit or hamsters. Survival of infected nymphal and adult I. scapularis did not differ from that of uninfected control ticks. R. monacensis did not disseminate from the gut of capillary fed adult female Amblyomma americanum (L.), or adult Dermacentor variabilis (Say) ticks of either sex. Infection of I. scapularis with R. monacensis expressing GFP provides a model system allowing visualization and study of live rickettsiae in unfixed tissues of an arthropod host.     

Borreliae in Ixodes ricinus ticks feeding on humans

A total of 298 Ixodes ricinus (L.) ticks (Acari: Ixodidae) feeding on humans in the Czech Republic were tested for borreliae (Borrelia burgdorferi sensu lato) by darkfield microscopy between 1997 and 2003. A majority (68%) of the supplied I. ricinus ticks were nymphs, 25% were females and 7% were larvae. Overall, 20% of 74 examined females and 9% of 203 examined nymphs (but none of 21 examined larvae) were infected with borreliae. The proportion of ticks with a high infection load (>100 spirochetes) was 4% in females and 2% in nymphal I. ricinus. During the year, the highest numbers and proportions of infected nymphal and female ticks were taken from humans in June. Detection of borreliae in the ticks feeding on humans might be helpful in the prophylaxis of Lyme borreliosis.     

Infestation of urban populations of the Northern white‐breasted hedgehog,Erinaceus roumanicus,by Ixodes spp. ticks in Poland

Infestation by the nest‐dwelling Ixodes hexagonus Leach and the exophilic Ixodes ricinus (Linnaeus) (Ixodida: Ixodidae) on the Northern white‐breasted hedgehog, Erinaceus roumanicus (Erinaceomorpha: Erinaceidae), was investigated during a 4‐year study in residential areas of the city of Poznań, west‐central Poland. Of 341 hedgehogs, 303 (88.9%) hosted 10 061 Ixodes spp. ticks encompassing all parasitic life stages (larvae, nymphs, females). Ixodes hexagonus accounted for 73% and I. ricinus for 27% of the collected ticks. Male hedgehogs carried significantly higher tick burdens than females. Analyses of seasonal prevalence and abundance of I. hexagonus revealed relatively stable levels of infestation of all parasitic stages, with a modest summer peak in tick abundance noted only on male hosts. By contrast, I. ricinus females and nymphs peaked in spring and declined steadily thereafter in summer and autumn, whereas the less abundant larvae peaked in summer. This is the first longterm study to evaluate the seasonal dynamics of both tick species on populations of wild hedgehogs inhabiting urban residential areas.     

Active surveillance to update county scale distribution of four tick species of medical and veterinary importance in Oklahoma

The incidence of tick‐borne disease continues to increase in humans and companion animals in the United States, yet distribution maps for several tick vectors in Oklahoma, including Dermacentor variabilis, Dermacentor albipictus, Ixodes scapularis, and Amblyomma maculatum, are not available or are outdated. To address this issue, county‐scale tick records from peer‐reviewed literature and passive collections were reviewed for Oklahoma. Additionally, dry ice traps, tick drags, and harvested deer were utilized to actively collect adult ticks throughout the state. Through these methods, D. variabilis, D. albipictus, I. scapularis, and A. maculatum were identified in 88% (68/77), 45.4% (35/77), 66.2% (51/77), and 64.9% (50/77) of the counties in Oklahoma, respectively. Baseline maps were developed for the distribution of D. variabilis and D. albipictus and distribution maps were updated for I. scapularis and A. maculatum. This data confirms that these four species of ticks continue to be widespread within Oklahoma with a western expansion of the range of I. scapularis within the state. These results assist efforts to better understand the epidemiology of the different diseases caused by pathogens transmitted by these tick species within the Great Plains region.