Projecting the Potential Distribution Areas of Ixodes scapularis (Acari: Ixodidae) Driven by Climate Change.
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ABSTRACT:
SUBMITTER: Zhang L
PROVIDER: S-EPMC8773098 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:In addition to serving as vectors of several other human pathogens, the black-legged tick, Ixodes scapularis Say, and western black-legged tick, Ixodes pacificus Cooley and Kohls, are the primary vectors of the spirochete (Borrelia burgdorferi) that causes Lyme disease, the most common vector-borne disease in the United States. Over the past two decades, the geographic range of I. pacificus has changed modestly while, in contrast, the I. scapularis range has expanded substantially, which likely contributes to the concurrent expansion in the distribution of human Lyme disease cases in the Northeastern, North-Central and Mid-Atlantic states. Identifying counties that contain suitable habitat for these ticks that have not yet reported established vector populations can aid in targeting limited vector surveillance resources to areas where tick invasion and potential human risk are likely to occur. We used county-level vector distribution information and ensemble modeling to map the potential distribution of I. scapularis and I. pacificus in the contiguous United States as a function of climate, elevation, and forest cover. Results show that I. pacificus is currently present within much of the range classified by our model as suitable for establishment. In contrast, environmental conditions are suitable for I. scapularis to continue expanding its range into northwestern Minnesota, central and northern Michigan, within the Ohio River Valley, and inland from the southeastern and Gulf coasts. Overall, our ensemble models show suitable habitat for I. scapularis in 441 eastern counties and for I. pacificus in 11 western counties where surveillance records have not yet supported classification of the counties as established.
| S-EPMC5491370 | biostudies-literature
Project description:In the north-central United States, the blacklegged tick (Ixodes scapularis) is currently known to vector seven human pathogens. These include five bacteria (Borrelia burgdorferi sensu stricto, Borrelia mayonii, Borrelia miyamotoi, Anaplasma phagocytophilum, Ehrlichia muris eauclairensis), one protozoan (Babesia microti) and one virus (Powassan). We sought to assess the prevalence and distribution of these pathogens in host-seeking nymphs collected throughout Minnesota, a state on the northwestern edge of the tick's expanding range, where reported cases of I. scapularis-borne diseases have increased in incidence and geographic range over the past decade. Among the 1240 host-seeking I. scapularis nymphs that we screened from 64 sites, we detected all seven pathogens at varying frequencies. Borrelia burgdorferi s.s. was the most prevalent and geographically widespread, found in 25.24% of all nymphs tested. Anaplasma phagocytophilum and Babesia microti were also geographically widespread, but they were less prevalent than Bo. burgdorferi s.s. (detected in 6.29% and 4.68% of ticks, respectively). Spatial clusters of sites with high prevalence for these three pathogens were identified in the north-central region of the state. Prevalence was less than 1.29% for each of the remaining pathogens. Two or more pathogens were detected in 90 nymphs (7.26%); coinfections with Bo. burgdorferi s.s. and either A. phagocytophilum (51 nymphs, 4.11%) or Ba. microti (43 nymphs, 3.47%) were the most common combinations. The distribution and density of infected ticks mirrors the distribution of notifiable tick-borne diseases in Minnesota and provides information on the distribution and prevalence of recently described human pathogens.
| S-EPMC6594169 | biostudies-literature
Project description:The incidence and geographic range of tick-borne illness associated with Ixodes scapularis and Ixodes pacificus have dramatically increased in recent decades. Anaplasmosis, babesiosis, and Borrelia spirochete infections, including Lyme borreliosis, account for tens of thousands of reported cases of tick-borne disease every year. Assays that reliably detect pathogens in ticks allow investigators and public health agencies to estimate the geographic distribution of human pathogens, assess geographic variation in their prevalence, and evaluate the effectiveness of prevention strategies. As investigators continue to describe new species within the Borrelia burgdorferi sensu lato complex and to recognize some Ixodes-borne Borrelia species as human pathogens, assays are needed to detect and differentiate these species. Here we describe an algorithm to detect and differentiate pathogens in unfed I. scapularis and I. pacificus nymphs including Anaplasma phagocytophilum, Babesia microti, Borrelia burgdorferi sensu stricto, Borrelia mayonii, and Borrelia miyamotoi. The algorithm comprises 5 TaqMan real-time polymerase chain reaction assays and 3 sequencing protocols. It employs multiple targets for each pathogen to optimize specificity, a gene target for I. scapularis and I. pacificus to verify tick-derived DNA quality, and a pan-Borrelia target to detect Borrelia species that may emerge as human disease agents in the future. We assess the algorithm's sensitivity, specificity, and performance on field-collected ticks.
| S-EPMC6452875 | biostudies-literature
Project description:BackgroundIxodes scapularis is a vector of several human pathogens in the United States, and there is geographical variation in the relative number of persons infected with these pathogens. Geographically isolated populations of I. scapularis have established or are in the process of establishing in southern Canada. Knowledge of the genetic variation within and among these populations may provide insight into their geographical origins in the United States and the potential risk of exposure of Canadians to the different pathogens carried by I. scapularis.MethodsPart of the mitochondrial (mt) 16S ribosomal (r) RNA gene was amplified by PCR from 582 ticks collected from southern Canada, and Minnesota and Rhode Island in the United States. Sequence variation was examined in relation to the predicted secondary structure of the gene. Genetic diversity among populations was also determined.ResultsDNA sequence analyses revealed 52 haplotypes. Most mutational alterations in DNA sequence occurred at unpaired sites or represented partial compensatory base pair changes that maintained the stability of the secondary structure. Significant genetic variation was detected within and among populations in different geographical regions. A greater proportion of the haplotypes of I. scapularis from the Canadian Prairie Provinces were found in the Midwest of the United States than in other regions, whereas more of the haplotypes of I. scapularis from the Canadian Central and Atlantic Provinces occurred in the Northeast of the United States. Nonetheless, 58% of I. scapularis were of a haplotype that occurs in the Midwest and Northeast of the United States; thus, their geographical origins could not be determined.ConclusionsThere is considerable genetic variation in the mt 16S rRNA gene of I. scapularis. There is some evidence to support the hypothesis that some lineages of I. scapularis in the Atlantic and Central Provinces of Canada may be derived from colonizing individuals originating in the Northeast of the United States, whereas those in the Prairie Provinces may be derived from individuals originating in the Midwest of the United States. However, additional genetic markers are needed to test hypotheses concerning the geographical origins of I. scapularis in Canada.
| S-EPMC4258262 | biostudies-literature
Project description:The blacklegged tick (Ixodes scapularis Say) is the primary vector of Borrelia burgdorferi sensu stricto (Spirochaetales: Spirochaetaceae), the Lyme disease agent in North America. The basic reproduction number (R0) for B. burgdorferi in I. scapularis in the Northeast is highly sensitive to the probability that engorged larvae survive the winter, molt into nymphs, and find a host. These processes are dependent on local environmental variables, including climate, host population size and movement, and tick behavior. A simple model is presented for estimating host-finding success from the ratio of tick abundance in two subsequent years, accounting for overwinter survival and possible differences in host associations between nymphs and larvae. This model was parameterized using data from two sites in mainland Connecticut and two on Block Island, RI. Host abundance and tick burdens were estimated via mark-recapture trapping of the primary host, Peromyscus leucopus Rafinesque. Overwintering survival was estimated using engorged larvae placed in field enclosures at each site. Only nymphs were recovered alive, and no significant differences in model parameters were observed between Connecticut and Block Island. Host-finding success was predicted to be high across a wide range of host association patterns at three of four sites. Assuming equivalent host association between larvae and nymphs, R0 was also estimated to be greater than one at three of four sites, suggesting these conditions allow for the persistence of B. burgdorferi. The model output was highly sensitive to differences between nymphal and larval host associations.
| S-EPMC7954101 | biostudies-literature
Project description:Lyme borreliosis is caused by spirochetes from the Borrelia burgdorferi sensu lato species complex. In the United States, B. burgdorferi sensu stricto (s.s.; Johnson, Schmid, Hyde, Steigerwalt, and Brenner) is the most common cause of human Lyme borreliosis. With >25,000 cases reported annually, it is the most common vector-borne disease in the United States. Although approximately 90% of cases are contained to the northeastern and Great Lake states, areas in Canada and some southern states are reporting rises in the number of human disease cases. Louisiana records a few cases of Lyme each year. Although some are most certainly the result of travel to more endemic areas, there exists evidence of locally acquired cases. Louisiana has established populations of the vector tick, Ixodes scapularis (Say), and a wide variety of potential reservoir animals, yet Lyme Borrelia has never been described in the state. Using culture and polymerase chain reaction, we investigated the presence of Lyme Borrelia in both mammals and questing ticks at a study site in Louisiana. Although culture was mostly unsuccessful, we did detect the presence of B. burgdorferi s.s. DNA in 6.3% (11 of 174) of ticks and 22.7% (five of 22) of animal samples. To our knowledge, this is among the first evidence documenting B. burgdorferi s.s. in Louisiana. Further investigations are required to determine the significance these findings have on human and animal health.
| S-EPMC3955005 | biostudies-literature
Project description:Rickettsia buchneri is the principal symbiotic bacterium of the medically significant tick Ixodes scapularis This species has been detected primarily in the ovaries of adult female ticks and is vertically transmitted, but its tissue tropism in other life stages and function with regard to tick physiology is unknown. In order to determine the function of R. buchneri, it may be necessary to produce ticks free from this symbiont. We quantified the growth dynamics of R. buchneri naturally occurring in I. scapularis ticks throughout their life cycle and compared it with bacterial growth in ticks in which symbiont numbers were experimentally reduced or eliminated. To eliminate the bacteria, we exposed ticks to antibiotics through injection and artificial membrane feeding. Both injection and membrane feeding of the antibiotic ciprofloxacin were effective at eliminating R. buchneri from most offspring of exposed females. Because of its effectiveness and ease of use, we have determined that injection of ciprofloxacin into engorged female ticks is an efficient means of clearing R. buchneri from the majority of progeny.IMPORTANCE This paper describes the growth of symbiotic Rickettsia buchneri within Ixodes scapularis through the life cycle of the tick and provides methods to eliminate R. buchneri from I. scapularis ticks.
| S-EPMC7848900 | biostudies-literature
Project description:Borrelia miyamotoi is an emerging, tick-borne human pathogen. In North America, it is primarily associated with Ixodes scapularis and Ixodes pacificus, two species known to bite humans. Here we describe the development and evaluation of a pair of real-time TaqMan PCR assays designed to detect B. miyamotoi in North American ticks. We sought to achieve sensitivity to B. miyamotoi strains associated with ticks throughout North America, the full genetic diversity of which is unknown, by targeting sequences that are largely conserved between B. miyamotoi strains from the eastern United States and genetically distinct B. miyamotoi strains from Japan. The two assays target different loci on the B. miyamotoi chromosome and can be run side by side under identical cycling conditions. One of the assays also includes a tick DNA target that can be used to verify the integrity of tick-derived samples. Using both recombinant plasmid controls and genomic DNA from North American and Japanese strains, we determined that both assays reliably detect as few as 5 copies of the B. miyamotoi genome. We verified that neither detects B. burgdorferi, B. lonestari or B. turicatae. This sensitive and specific pair of assays successfully detected B. miyamotoi in naturally-infected, colony-reared nymphs and in field-collected I. scapularis and I. pacificus from the Northeast and the Pacific Northwest respectively. These assays will be useful in screening field-collected Ixodes spp. from varied regions of North America to assess the risk of human exposure to this emerging pathogen.
| S-EPMC5572795 | biostudies-literature
Project description:Tick-borne pathogens transmitted by Ixodes scapularis Say (Acari: Ixodidae), also known as the deer tick or blacklegged tick, are increasing in incidence and geographic distribution in the United States. We examined the risk of tick-borne disease exposure in 9 national parks across six Northeastern and Mid-Atlantic States and the District of Columbia in 2014 and 2015. To assess the recreational risk to park visitors, we sampled for ticks along frequently used trails and calculated the density of I. scapularis nymphs (DON) and the density of infected nymphs (DIN). We determined the nymphal infection prevalence of I. scapularis with a suite of tick-borne pathogens including Borrelia burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia microti. Ixodes scapularis nymphs were found in all national park units; DON ranged from 0.40 to 13.73 nymphs per 100 m2. Borrelia burgdorferi, the causative agent of Lyme disease, was found at all sites where I. scapularis was documented; DIN with B. burgdorferi ranged from 0.06 to 5.71 nymphs per 100 m2. Borrelia miyamotoi and A. phagocytophilum were documented at 60% and 70% of the parks, respectively, while Ba. microti occurred at just 20% of the parks. Ixodes scapularis is well established across much of the Northeastern and Mid-Atlantic States, and our results are generally consistent with previous studies conducted near the areas we sampled. Newly established I. scapularis populations were documented in two locations: Washington, D.C. (Rock Creek Park) and Greene County, Virginia (Shenandoah National Park). This research demonstrates the potential risk of tick-borne pathogen exposure in national parks and can be used to educate park visitors about the importance of preventative actions to minimize tick exposure.
| S-EPMC5657145 | biostudies-literature
Project description:Obtaining reliable gene expression data using real-time quantitative polymerase chain reaction (qPCR) is highly dependent on the choice of normalization method. We tested the expression stability of multiple candidate genes in the salivary glands (SG) and synganglia (SYN) of female Ixodes scapularis (Say) ticks in multiple blood-feeding phases. We found that the amount of total RNA in both the SG and SYN increases dramatically during tick feeding, with 34x and 5.8x increases from 62 and 7.1 ng of unfed tick, respectively. We tested candidate genes that were predicted from I. scapularis genome data to encode glyceraldehyde 3-phosphate dehydrogenase (gapdh), ribosomal protein L13A (l13a), TATA box-binding protein (tbp), ribosomal protein S4 (rps4), glucose 6-phosphate dehydrogenase (gpdh), and beta-glucuronidase (gusb). The geNorm and NormFinder algorithms were used to analyze data from different feeding phases (i.e., daily samples from unfed to fully engorged females over a 7-d period in three replicate experiments). We found that the rps4 and l13a genes showed highly stable expression patterns over the feeding duration in both the SG and SYN. Furthermore, the highly expressed rps4 gene makes it useful as a normalization factor when we perform studies using minute amounts of dissected tissue for qPCR. We conclude that rps4 and l13a, whether individually or as a pair, serve as suitable internal reference genes for qRT-PCR studies in the SG and SYN of I. scapularis.
| S-EPMC3703510 | biostudies-literature