Tick Ixodes Scapularis Say Research Articles

Patterns and Ecological Mechanisms of Tick-Borne Disease Exposure Risk in Acadia National Park, Mount Desert Island, Maine, United States.

National parks are unique and significant vector-borne pathogen transmission settings, engaging over 300 million people in outdoor recreation per year. In this study, we integrated vector surveys and ecological habitat feature data in spatial models to characterize tick-borne disease exposure risk in Acadia National Park (ANP), Maine. To determine the broad-scale patterns of blacklegged tick Ixodes scapularis Say (Acari: Ixodidae) densities in ANP, we conducted host-seeking tick collections at 114 sites across the park over two years. Using these tick survey data and geospatial landscape feature data (i.e., land cover, elevation, forest patch size, and aspect) we developed a random forest model of nymphal tick density. We found that host-seeking tick density varies significantly across the park and is particularly high in areas characterized by deciduous forest cover and relatively low elevation. To explore potential fine-scale ecological drivers of tick density spatial patterns, we quantified microclimate conditions, host activity, and vegetation characteristics at a subset of 19 sites. We identified significant differences in microclimate conditions but not host activity or vegetation metrics across broad-scale landscape feature classes. Mean temperature and mean humidity were correlated to nymphal densities and therefore may provide a mechanistic link between landscape features and blacklegged tick densities. Finally, we detected multiple tick-borne pathogens in both ticks and small mammals sampled in ANP, including Borrelia burgdorferi, Babesia microti, and Anaplasma phagocytophilum. Our findings demonstrate the value of using ecological metrics to estimate vector-borne disease exposure risk and provide insight into habitat characteristics that may drive tick-borne disease exposure risk.

Practical Guide to Trapping Peromyscus leucopus (Rodentia: Cricetidae) and Peromyscus maniculatus for Vector and Vector-Borne Pathogen Surveillance and Ecology.

Arthropods pests are most frequently associated with both plants and vertebrate animals. Ticks, in particular the blacklegged ticks Ixodes scapularis Say and Ixodes pacificus Cooley & Kohls (Acari: Ixodidae), are associated with wildlife hosts and are the primary vectors of Lyme disease, the most frequently reported vector-borne disease in the United States. Immature blacklegged ticks in the eastern United States frequently use small mammals from the genus Peromyscus as hosts. These mice are competent reservoirs for Borrelia burgdorferi, the causative agent of Lyme disease, as well as other tick-borne pathogens. To conduct surveillance on immature ticks and pathogen circulation in hosts, capture and handling of these small mammals is required. While protocols for rearing and pest surveillance on plants are common, there are very few protocols aimed at entomologists to conduct research on vertebrate–arthropod relationships. The goal of this manuscript is to provide a practical template for trapping Peromyscus spp. for vector and vector-borne pathogen surveillance and ecology for professionals that may not have a background in wildlife research. Important considerations are highlighted when targeting P. leucopus Rafinesque and P. maniculatus Wagner. Specifically, for tick and tick-borne disease-related projects, materials that may be required are suggested and references and other resources for researchers beginning a trapping study are provided.

Assessing Effectiveness of Recommended Residential Yard Management Measures Against Ticks.

Public health authorities recommend a range of nonchemical measures to control blacklegged ticks Ixodes scapularis Say, 1821 (Ixodida: Ixodidae) in residential yards. Here we enumerate these recommendations and assess their relationship to larval tick abundance in 143 yards in Dutchess County, New York, an area with high Lyme disease incidence. We examined the relationship between larval tick abundance and eight property features related to recommendations from public health agencies: presence or absence of outdoor cats, wood piles, trash, stone walls, wood chip barriers separating lawn from adjacent forest, bird feeders, fencing, and prevalence of Japanese barberry (Berberis thunbergii DC [Ranunculales: Berberidaceae]). We assessed abundance of larval ticks using two methods, flagging for questing ticks and visual examination of ticks on white-footed mice Peromyscus leucopus Rafinesque, 1818 (Rodentia: Cricetidae). More questing larvae were found in yards where trash or stone walls were present. These effects were less pronounced as forest area increased within the yard. Counts of larvae per mouse were lower in properties with >75% of the yard fenced than in properties with less fencing. We find partial support for recommendations regarding trash, stone walls, and fencing. We did not detect effects of outdoor cats, bird feeders, barriers, wood piles, or Japanese barberry. There was low statistical power to detect effects of ground barriers (gravel, mulch, or woodchip), which were present in only two properties.

Comment on Qu et al. 2016.

Qu et al. (2016) claim to have identified members of the three major families of chemoreceptors known in arthropods in a whole-body transcriptome of the storage mite Tyrophagus putrescentiae Schrank. Unfortunately, I believe their analysis is seriously flawed. The Odorant Receptor (OR) family in insects is a relatively recent evolutionary innovation derived from a lineage of the more ancient and diverse Gustatory Receptor (GR) family within the insect chemoreceptor superfamily (Robertson et al. 2003, Benton 2015), and appears to have evolved within the insect lineage (Missbach et al. 2014). It has not previously been detected in arthropods beyond insects for which a whole genome sequence is available, thus the OR family is not present in the genomes of the crustacean Daphnia pulex (Penalva-Arana et al. 2009), the centipede Strigamia maritima Leach (Chipman et al. 2014), the black-legged tick Ixodes scapularis Say (Gulia-Nuss et al. 2016), or the predatory mite Metaseiulus occidentalis Nesbitt (Hoy et al. 2016). Members of the OR family are also not present in numerous published transcriptomes from noninsect arthropods (e.g., Misof et al. 2014). The authors’ claim to have identified this gene family in …

What Do We Need to Know About Disease Ecology to Prevent Lyme Disease in the Northeastern United States?: Table 1.

Lyme disease is the most commonly reported vector-borne disease in the United States, with the majority of cases occurring in the Northeast. It has now been three decades since the etiological agent of the disease in North America, the spirochete Borrelia burgdorferi, and its primary North American vectors, the ticks Ixodes scapularis Say and I. pacificus Cooley & Kohls, were identified. Great strides have been made in our understanding of the ecology of the vectors and disease agent, and this knowledge has been used to design a wide range of prevention and control strategies. However, despite these advances, the number of Lyme disease cases have steadily increased. In this article, we assess potential reasons for the continued lack of success in prevention and control of Lyme disease in the northeastern United States, and identify conceptual areas where additional knowledge could be used to improve Lyme disease prevention and control strategies. Some of these areas include: 1) identifying critical host infestation rates required to maintain enzootic transmission of B. burgdorferi, 2) understanding how habitat diversity and forest fragmentation impacts acarological risk of exposure to B. burgdorferi and the ability of interventions to reduce risk, 3) quantifying the epidemiological outcomes of interventions focusing on ticks or vertebrate reservoirs, and 4) refining knowledge of how human behavior influences Lyme disease risk and identifying barriers to the adoption of personal protective measures and environmental tick management.

Forest and Surface Water As Predictors ofBorrelia burgdorferiand Its VectorIxodes scapularis(Acari: Ixodidae) in Indiana

The objective of this study was to assess whether the distribution of Borrelia burgdorferi, the causative agent of Lyme disease, and its vector tick Ixodes scapularis Say (Acari: Ixodidae) across Indiana is influenced by large-scale landscape features, specifically the proportion of forest within the surrounding landscape and the distance to water features such as lakes and major streams. Hunter-killed deer were checked for ticks in designated check-stations in the opening firearm hunting season between 2005 and 2007. Hunting locations for ≈3,600 deer were used in ArcGIS (ESRI, Redlands, CA) to examine the influence of forest and water features in the surrounding area on the occurrence of the tick and bacteria. In total, 82 of the 92 (89%) Indiana counties were sampled from 2005 to 2007. The proportion of tick-infested deer was 13.6, 15.8, and 25.5% in these years, respectively. There was a significant nonlinear response for I. scapularis to forest cover in 1 yr that indicated a greater probability of this tick presence at intermediate levels of forest area. Infested does were harvested in significantly more forested areas than bucks. No significant correlation was found neither between levels of forest area and B. burgdorferi nor between water bodies and both organisms.

Forest and Surface Water As Predictors of <I>Borrelia burgdorferi</I> and Its Vector <I>Ixodes scapularis</I> (Acari: Ixodidae) in Indiana

The objective of this study was to assess whether the distribution of Borrelia burgdorferi, the causative agent of Lyme disease, and its vector tick Ixodes scapularis Say (Acari: Ixodidae) across Indiana is influenced by large-scale landscape features, specifically the proportion of forest within the surrounding landscape and the distance to water features such as lakes and major streams. Hunter-killed deer were checked for ticks in designated check-stations in the opening firearm hunting season between 2005 and 2007. Hunting locations for approximately 3,600 deer were used in ArcGIS (ESRI, Redlands, CA) to examine the influence of forest and water features in the surrounding area on the occurrence of the tick and bacteria. In total, 82 of the 92 (89%) Indiana counties were sampled from 2005 to 2007. The proportion of tick-infested deer was 13.6, 15.8, and 25.5% in these years, respectively. There was a significant nonlinear response for I. scapularis to forest cover in 1 yr that indicated a greater probability of this tick presence at intermediate levels of forest area. Infested does were harvested in significantly more forested areas than bucks. No significant correlation was found neither between levels of forest area and B. burgdorferi nor between water bodies and both organisms.

<I>Ixodes scapularis</I> Ticks Collected by Passive Surveillance in Canada: Analysis of Geographic Distribution and Infection with Lyme Borreliosis Agent <I>Borrelia burgdorferi</I>

Passive surveillance for the occurrence of the tick Ixodes scapularis Say (1821) and their infection with the Lyme borreliosis spirochaetes Borrelia burgdorferi s.l. has taken place in Canada since early 1990. Ticks have been submitted from members of the public, veterinarians, and medical practitioners to provincial, federal, and university laboratories for identification, and the data have been collated and B. burgdorferi detected at the National Microbiology Laboratory. The locations of collection of 2,319 submitted I. scapularis were mapped, and we investigated potential risk factors for I. scapularis occurrence (in Quebec as a case study) by using regression analysis and spatial statistics. Ticks were submitted from all provinces east of Alberta, most from areas where resident I. scapularis populations are unknown. Most were adult ticks and were collected in spring and autumn. In southern Québec, risk factors for tick occurrence were lower latitude and remote-sensed indices for land cover with woodland. B. burgdorferi infection, identified by conventional and molecular methods, was detected in 12.5% of 1,816 ticks, including 10.1% of the 256 ticks that were collected from humans and tested. Our study suggests that B. burgdorferi-infected I. scapularis can be found over a wide geographic range in Canada, although most may be adventitious ticks carried from endemic areas in the United States and Canada by migrating birds. The risk of Lyme borreliosis in Canada may therefore be mostly low but more geographically widespread than previously suspected.

ECTOPARASITES AND OTHER EPIFAUNISTIC ARTHROPODS OF SYMPATRIC COTTON MICE AND GOLDEN MICE: COMPARISONS AND IMPLICATIONS FOR VECTOR-BORNE ZOONOTIC DISEASES

Ectoparasite and epifaunistic arthropod biodiversity and infestation parameters were compared between 2 sympatric small rodent species, the cotton mouse (Peromyscus gossypinus (Le Conte)) and golden mouse (Ochrotomys nuttalli (Harlan)), in southern Georgia from 1992 to 2003. Because the cotton mouse is known to be a reservoir of more vector-borne zoonotic pathogens than the golden mouse, we hypothesized that it would be parasitized by more ectoparasites that are known to be vectors of these pathogens. Cotton mice (n = 202) were parasitized by 19 species of arthropods, whereas golden mice (n = 46) were parasitized by 12 species. Eleven species of arthropods were recovered from both host species, whereas 7 were recorded only from cotton mice, and 1 species only from golden mice. Infestation prevalences (percent of mice parasitized) were significantly higher for 1 species of arthropod (the tropical rat mite Ornithonyssus bacoti (Hirst)) infesting cotton mice and for 4 species (the flea Peromyscopsylla scotti Fox and the mites Glycyphagus hypudaei Koch, Androlaelaps casalis (Berlese), and Androlaelaps fahrenholzi (Berlese)) infesting golden mice. Mean intensities (mean per infested mouse) were significantly higher for 2 species (the flea Orchopeas leucopus (Baker) and the blacklegged tick Ixodes scapularis Say) infesting cotton mice and for 2 species (G. hypudaei and A. fahrenholzi) infesting golden mice. Ectoparasites that are known to be vectors of zoonotic pathogens were significantly more common on cotton mice than on golden mice. These ectoparasites included the rhopalopsyllid flea Polygenis gwyni (Fox), a vector of the agent of murine typhus; I. scapularis, the principal vector of the agents of Lyme borreliosis, human granulocytic ehrlichiosis, and human babesiosis; and O. bacoti, a laboratory vector of several zoonotic pathogens. However, 2 species of ixodid ticks that can transmit zoonotic pathogens were recovered from both host species. These were the American dog tick Dermacentor variabilis (Say), the principal vector of the agent of Rocky Mountain spotted fever in eastern North America, and Ixodes minor Neumann, an enzootic vector of the agent of Lyme borreliosis. Overall, the cotton mouse was parasitized by significantly more ectoparasites that are known to be vectors of zoonotic pathogens than was the golden mouse. These data support the hypothesis that the cotton mouse has greater epidemiological importance for zoonotic vector-borne pathogen transmission than does the golden mouse.

Investigation of relationships between temperature and developmental rates of tick Ixodes scapularis (Acari: Ixodidae) in the laboratory and field.

Relationships between temperature and preoviposition, preeclosion, and premolt developmental periods for the tick Ixodes scapularis Say were investigated by holding field-collected ticks in the laboratory at temperatures of 0 to 32 degrees C at constant daylength. The duration of these developmental periods decreased significantly with increasing temperature. Host of origin, prior storage at 4 degrees C, and season of collection of the ticks were also significantly associated with variations in the duration of the preoviposition period. For each developmental stage, the effect of temperature on development rate was best described as a power relationship. Laboratory-derived relationships were used to predict dates for molting, oviposition, and eclosion of engorged larvae and nymphs, engorged adult females and egg masses, respectively, placed in the field during 1989-1992. Predicted dates for oviposition by adult females, eclosion of eggs, and molting of engorged larvae were within 2 wk of the observed dates, and field-observed seasonal activity of questing larvae and nymphs also was predicted well by laboratory data. Molting of engorged nymphs and seasonal activity of questing adult ticks were, however, poorly predicted. Our findings suggest that duration of development in the field, of larvae from engorged adult females, and of nymphs from engorged larvae, may be explained largely by temperature effects alone, whereas emergence of adult I. scapularis from engorged nymphs may depend on temperature-independent diapause phenomena. The significance of these findings for understanding current and future distributions of I. scapularis, and of the pathogens it transmits, is discussed.

Reduced abundance of Ixodes scapularis (Acari: Ixodidae) and the tick parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) with reduction of white-tailed deer.

The principal vector for the pathogens of Lyme disease, human granulocytic ehrlichiosis, and human babesiosis is the tick Ixodes scapularis Say. A chalcid wasp, Ixodiphagus hookeri, in the family Encyrtidae parasitizes populations of the tick on several islands or other geographically isolated sites in New England with high densities of these ticks and white-tailed deer (Odocoileus virginianus), the principal host for adult I. scapularis. Deer densities were reduced at a forested tract in Bridgeport and the Bluff Point Coastal Reserve in Groton, Connecticut, from levels exceeding 90 animals per km2 in 1992 (Bridgeport) and 1994 (Bluff Point) to 17 and 10 animals per km2, respectively, by fall 2001. Tick densities declined with sustained reductions in the population of white-tailed deer. Similarly, prevalence of tick parasitism by Ixodes hookeri declined at both sites from 30 to 25% to <1.0% and was significantly correlated with previous year's deer density at both sites (r(s) = 0.933 and r(s) = 0.867, P < or = 0.0001) and with nymphal tick densities at Bridgeport (r(s) = 0.867, P < or = 0.0001), but was not as well correlated with tick densities in Groton. The virtual disappearance of I. hookeri in this study corresponds with a lack of I. hookeri in mainland I. scapularis at comparable deer and tick densities, suggesting that there is a threshold deer density of approximatley 10-20/km2, with corresponding tick densities necessary for I. hookeri to successfully parasitize I. scapularis.

A mathematical model of the ecology of Lyme disease

A mathematical model of enzootic Lyme-disease transmission in a natural focus is presented. This model is based on the life history of the vector tick Ixodes scapularis Say and the primary reservoir host Peromyscus leucopus. Using this model, the threshold condition for the disease to be able to invade a nonenzootic region is determined as a function of the various possible transmission chains operating throughout the year. These expressions show that the transmission chain in which ticks acquire the disease from mice in the fall and transmit it back to mice as nymphs in the spring is the most important chain (contributing approximately 87% of the elasticity of the threshold for the parameter choices examined). Equilibrium disease levels were examined under the assumption of a constant tick population; these levels were determined as a function of tick and mouse density, the vertical transmission rate, the infectivity of mice, and the survivorship parameters of the ticks and of the tick-host contact rates. Vertical transmission has a disproportionately large effect, since unfed infected larval ticks have two opportunities to feed on mice, rather than only one opportunity (as for a newly infected unfed nymph). Finally, a global sensitivity analysis based on Latin hypercube sampling is performed, in which is shown the importance of quantifying the natural history of infection in mice, and of elucidating the contribution of other hosts for I. scapularis than mice.

A mathematical model of the ecology of Lyme disease

A mathematical model of enzootic Lyme-disease transmission in a natural focus is presented. This model is based on the life history of the vector tick Ixodes scapularis Say and the primary reservoir host Peromyscus leucopus. Using this model, the threshold condition for the disease to be able to invade a nonenzootic region is determined as a function of the various possible transmission chains operating throughout the year. These expressions show that the transmission chain in which ticks acquire the disease from mice in the fall and transmit it back to mice as nymphs in the spring is the most important chain (contributing approximately 87 % of the elasticity of the threshold for the parameter choices examined). Equilibrium disease levels were examined under the assumption of a constant tick population; these levels were determined as a function of tick and mouse density, the vertical transmission rate, the infectivity of mice, and the survivorship parameters of the ticks and of the tick-host contact rates. Vertical transmission has a disproportionately large effect, since unfed infected larval ticks have two opportunities to feed on mice, rather than only one opportunity (as for a newly infected unfed nymph). Finally, a global sensitivity analysis based on Latin hypercube sampling is performed, in which is shown the importance of quantifying the natural history of infection in mice, and of elucidating the contribution of other hosts for I.scapularis than mice.

Variation in Ribosomal DNA Internal Transcribed Spacers 1 Among Eastern Populations of Ixodes scapularis (Acari: Ixodidae)

The base sequence of the internal transcribed spacer 1 (ITS 1) of ribosomal DNA of the tick Ixodes scapularis Say (= I. dammini Spielman, Clifford, Piesman & Corwin) was determined to assess genetic divergence between populations along the eastern (Atlantic) seaboard of the United States. Twenty sequences were obtained from localities down the eastern margin of the species's range: 10 from the southeast (Georgia and Florida), seven from the middle east (North Carolina, Maryland), and three from the northeast (Massachusetts, New Jersey, New York). Both the neighbor-joining and parsimony methods cluster most of the southeastern sequences together and most of the middle eastern sequences together but fail to cluster those from the northeast. In addition, an F ratio test revealed significant between-region sequence variation. Thus, there appears to be genetic structuring on at least a macrogeographic scale. Only 23% (SEM = 6.4%) of the sequence variation occurs between regions, with the vast majority of variation, 77% (SEM = 6.4%), being within region. These data, plus other published data, indicate that I. scapularis constitutes a single species. However, the pattern of variation is consistent with restricted gene flow between regions or, alternatively, with recent introgression between northern and southern types in the middle-eastern part of the species's range.

Evidence for kairomonal influence on selection of host-ambushing sites by adult Ixodes scapularis (Acari: Ixodidae).

Unfed adult blacklegged ticks Ixodes scapularis Say, were tested under laboratory conditions for behavioral responses to substances rubbed from external glands on legs of white-tailed deer, Odocoileus virginianus (Zimmermann). In replicated trials, significantly more female ticks became stationary on portions of vertical glass tubing rubbed with the tarsal gland substances of both bucks and does than on nontreated tubing. This behavior, apparently an arrestant response, was infrequent among males. White-tailed deer urinate upon their tarsal glands, and doe urine also produced an arrestant response among female ticks. Metatarsal gland secretions of bucks elicited no arrestant response in either male or female I. scapularis, but doe metatarsal gland secretions elicited low-level positive responses from both sexes. A low-level arrestant response also was exhibited by females to secretions from the interdigital glands of bucks. In a second bioassay, three times as many females came to rest on the terminal ends of vertical glass rods whose bases were treated with secretions from buck interdigital glands than on rods with nontreated bases. This suggests that interdigital gland secretion influences blacklegged tick climbing behavior. Substances produced by or associated with the leg glands of O. virginianus may therefore serve as kairomones for host-seeking adult I. scapularis; interdigital gland secretions on soil or leaf litter may signal active deer trails, and tarsal gland substances may denote portions of vegetation contacted previously by white-tailed deer. In nature, use of these chemical cues by host-seeking adult I. scapularis may increase the probability of acquiring a suitable host.