An official website of the United States government
Amblyomma maculatum (Gulf Coast tick), and Dermacentor andersoni (Rocky Mountain wood tick) are two North American ticks that transmit spotted fevers associated Rickettsia . Amblyomma maculatum transmits Rickettsia parkeri and Francisella tularensis , while D. andersoni transmits R. rickettsii , Anaplasma marginale , Coltivirus (Colorado tick fever virus), and F. tularensis . Increases in temperature causes mild winters and more extreme dry periods during summers, which will affect tick populations in unknown ways. Here, we used ecological niche modeling (ENM) to assess the potential geographic distributions of these two medically important vector species in North America under current condition and then transfer those models to the future under different future climate scenarios with special interest in highlighting new potential expansion areas. Current model predictions for A. maculatum showed suitable areas across the southern and Midwest United States, and east coast, western and southern Mexico. For D. andersoni , our models showed broad suitable areas across northwestern United States. New potential for range expansions was anticipated for both tick species northward in response to climate change, extending across the Midwest and New England for A. maculatum , and still farther north into Canada for D. andersoni .
more »
« less
This content will become publicly available on November 18, 2025
Ticks without borders: microbiome of immature neotropical tick species parasitizing migratory songbirds along northern Gulf of Mexico
IntroductionThe long-distance, seasonal migrations of birds make them an effective ecological bridge for the movement of ticks. The introduction of exotic tick species to new geographical regions can cause the emergence of novel tick-borne pathogens. This study examined the prevalence of exotic tick species parasitizing migratory songbirds at stopover sites along the northern Gulf of Mexico using the mitochondrial 12S rRNA gene. MethodsOverall, 421 individual ticks in the generaAmblyomma,Haemaphysalis, andIxodeswere recorded from 28 songbird species, of whichAmblyommaandAmblyomma longirostrewere the most abundant tick genera and species, respectively. A high throughput 16S ribosomal RNA sequencing approach characterized the microbial communities and identified pathogenic microbes in all tick samples. Results and discussionMicrobial profiles showed that Proteobacteria was the most abundant phylum. The most abundant pathogens wereRickettsiaand endosymbiontFrancisella,Candidatus Midichloria, andSpiroplasma. Permutation multivariate analysis of variance revealed that the relative abundance ofFrancisellaandRickettsiadrives microbial patterns across the tick genera. We also noted a higher percentage of positive correlations in microbe-microbe interactions among members of the microbial communities. Network analysis suggested a negative correlation between a)FrancisellaandRickettsiaand, b)FrancisellaandCutibacterium. Lastly, mapping the distributions of bird species parasitized during spring migrations highlighted geographic hotspots where migratory songbirds could disperse ticks and their pathogens at stopover sites or upon arrival to their breeding grounds, the latter showing mean dispersal distances from 421–5003 kilometers. These findings spotlight the potential role of migratory birds in the epidemiology of tick-borne pathogens.
more »
« less
- Award ID(s):
- 2515340
- PAR ID:
- 10595379
- Publisher / Repository:
- Frontiers
- Date Published:
- Journal Name:
- Frontiers in Cellular and Infection Microbiology
- Volume:
- 14
- ISSN:
- 2235-2988
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Increasing incidence of tick-borne human diseases and geographic range expansion of tick vectors elevates the importance of research on characteristics of tick species that transmit pathogens. Despite their global distribution and role as vectors of pathogens such as Rickettsia spp., ticks in the genus Dermacentor Koch, 1844 (Acari: Ixodidae) have recently received less attention than ticks in the genus Ixodes Latreille, 1795 (Acari: Ixodidae). To address this knowledge gap, we compiled an extensive database of Dermacentor tick traits, including morphological characteristics, host range, and geographic distribution. Zoonotic vector status was determined by compiling information about zoonotic pathogens found in Dermacentor species derived from primary literature and data repositories. We trained a machine learning algorithm on this data set to assess which traits were the most important predictors of zoonotic vector status. Our model successfully classified vector species with ~84% accuracy (mean AUC) and identified two additional Dermacentor species as potential zoonotic vectors. Our results suggest that Dermacentor species that are most likely to be zoonotic vectors are broad ranging, both in terms of the range of hosts they infest and the range of ecoregions across which they are found, and also tend to have large hypostomes and be small-bodied as immature ticks. Beyond the patterns we observed, high spatial and species-level resolution of this new, synthetic dataset has the potential to support future analyses of public health relevance, including species distribution modeling and predictive analytics, to draw attention to emerging or newly identified Dermacentor species that warrant closer monitoring for zoonotic pathogens.more » « less
-
Environmental dimensions, such as temperature, precipitation, humidity, and vegetation type, influence the activity, survival, and geographic distribution of tick species. Ticks are vectors of various pathogens that cause disease in humans, andIxodes scapularisandAmblyomma americanumare among the tick species that transmit pathogens to humans across the central and eastern United States. Although their potential geographic distributions have been assessed broadlyviaecological niche modeling, no comprehensive study has compared ecological niche signals between ticks and tick-borne pathogens. We took advantage of National Ecological Observatory Network (NEON) data for these two tick species and associated bacteria pathogens across North America. We used two novel statistical tests that consider sampling and absence data explicitly to perform these explorations: a univariate analysis based on randomization and resampling, and a permutational multivariate analysis of variance. Based on univariate analyses, inAmblyomma americanum, three pathogens(Borrelia lonestari,Ehrlichia chaffeensis, andE. ewingii) were tested; pathogens showed nonrandom distribution in at least one environmental dimension. Based on the PERMANOVA test, the null hypothesis that the environmental position and variation of pathogen-positive samples are equivalent to those ofA. americanumcould not be rejected for any of the pathogens, except for the pathogenE. ewingiiin maximum and minimum vapor pressure and minimum temperature. ForIxodes scapularis,six pathogens (A. phagocytophilum,Babesia microti,Borrelia burgdorferisensu lato,B. mayonii,B. miyamotoi, andEhrlichia muris-like) were tested; onlyB. miyamotoiwas not distinct from null expectations in all environmental dimensions, based on univariate tests. In the PERMANOVA analyses, the pathogens departed from null expectations forB. microtiandB. burgdorferisensu lato, with smaller niches inB. microti, and larger niches inB. burgdorferisensu lato, than the vector. More generally, this study shows the value of large-scale data resources with consistent sampling methods, and known absences of key pathogens in particular samples, for answering public health questions, such as the relationship of presence and absence of pathogens in their hosts respect to environmental conditions.more » « less
-
Stevenson, Brian (Ed.)Ticks are the most important vectors of zoonotic disease-causing pathogens in North America and Europe. Many tick species are expanding their geographic range. Although correlational evidence suggests that climate change is driving the range expansion of ticks, experimental evidence is necessary to develop a mechanistic understanding of ticks’ response to a range of climatic conditions. Previous experiments used simulated microclimates, but these protocols require hazardous salts or expensive laboratory equipment to manipulate humidity. We developed a novel, safe, stable, convenient, and economical method to isolate individual ticks and manipulate their microclimates. The protocol involves placing individual ticks in plastic tubes, and placing six tubes along with a commercial two-way humidity control pack in an airtight container. We successfully used this method to investigate how humidity affects survival and host-seeking (questing) behavior of three tick species: the lone star tick ( Amblyomma americanum ), American dog tick ( Dermacentor variabilis ), and black-legged tick ( Ixodes scapularis ). We placed 72 adult females of each species individually into plastic tubes and separated them into three experimental relative humidity (RH) treatments representing distinct climates: 32% RH, 58% RH, and 84% RH. We assessed the survival and questing behavior of each tick for 30 days. In all three species, survivorship significantly declined in drier conditions. Questing height was negatively associated with RH in Amblyomma , positively associated with RH in Dermacentor , and not associated with RH in Ixodes . The frequency of questing behavior increased significantly with drier conditions for Dermacentor but not for Amblyomma or Ixodes . This report demonstrates an effective method for assessing the viability and host-seeking behavior of tick vectors of zoonotic diseases under different climatic conditions.more » « less
-
Becker, Daniel (Ed.)The states of Kansas and Oklahoma, in the central Great Plains, lie at the western periphery of the geographic distributions of several tick species. As the focus of most research on ticks and tick-borne diseases has been on Lyme disease which commonly occurs in areas to the north and east, the ticks of this region have seen little research attention. Here, we report on the phenology and activity patterns shown by tick species observed at 10 sites across the two states and explore factors associated with abundance of all and life specific individuals of the dominant species. Ticks were collected in 2020–2022 using dragging, flagging and carbon-dioxide trapping techniques, designed to detect questing ticks. The dominant species wasA.americanum(24098, 97%) followed byDermacentor variabilis(370, 2%),D.albipictus(271, 1%),Ixodes scapularis(91, <1%)and A.maculatum(38, <1%).Amblyomma americanum,A.maculatum and D.variabiliswere active in Spring and Summer, whileD.albipictus and I.scapulariswere active in Fall and Winter. Factors associated with numbers of individuals ofA.americanumincluded day of year, habitat, and latitude. Similar associations were observed when abundance was examined by life-stage. Overall, the picture is one of broadly distributed tick species that shows seasonal limitations in the timing of their questing activity.more » « less
