The Blacklegged Tick, Ixodes scapularis: An Increasing Public Health Concern

Eisen RJ, Eisen L.
Trends in Parasitology. 2018 Jan 11. pii: S1471-4922(17)30311-2.
In the United States, the blacklegged tick, Ixodes scapularis, is a vector of seven human pathogens, including those causing Lyme disease, anaplasmosis, babesiosis, Borrelia miyamotoi disease, Powassan virus disease, and ehrlichiosis associated with Ehrlichia muris eauclarensis.In addition to an accelerated rate of discovery of I. scapularis-borne pathogens over the past two decades, the geographic range of the tick, and incidence and range of I. scapularis-borne disease cases, have increased. Despite knowledge of when and where humans are most at risk of exposure to infected ticks, control of I. scapularis-borne diseases remains a challenge.

Lyme Disease Propelled by Borrelia burgdorferi-Infected Blacklegged Ticks, Wild Birds and Public Awareness ─ Not Climate Change.
Scott JD, Scott CM.
Journal of Veterinary Science & Medicine. 2018;6(1): 8.
The blacklegged tick, Ixodes scapularis, is of major public health importance as a vector of Borrelia burgdorferi, the causal organism of Lyme disease. Migratory songbirds are involved in short- and longdistance transport of bird-feeding ticks, and play a vital role in the wide dispersal of I. scapularis and the epidemiology of Lyme disease. Because northern latitudes generally have a thick blanket of snow each winter, the blacklegged tick withstands phenomenal outdoor temperature fluctuations. However, when the snow cover is lost in the core months of winter, due to subtle periods of warmer temperatures, we discovered that overwinter survival declined significantly. Photoperiod is a limiting factor in the pole-ward expansion and establishment of I. scapularis because immature stages of I. scapularis will not molt in late summer when photoperiod shortens quickly.When it comes to I. scapularis ticks, climate change is a triviality. Health professionals must be aware that Lyme disease and tick-associated diseases are a significant public health burden, and include them in their differential diagnosis.

Bloodsucking Ticks Make Cement to Attach to Your Skin – The disease-carrying parasites’ natural glue could also hold a key to healing us.
By Joshua Rapp Learn, National Geographic, Washington, DC
January 19, 2018
Bloodsucking parasites that can carry deadly diseases create their own cement to glue themselves to our bodies, a new study says. Hard ticks – a family of 700 species that includes the Lyme-spreading deer tick – use pincer-like appendages and mouths to attach to a host’s skin. But sometimes this grip isn’t strong enough for the arachnid to hold on and feed while the host moves. Sylvia Nürnberger and colleagues discovered hard ticks have an extra tool to glom onto their hosts’ skin – a kind of glue made of proteins in their saliva.

Integrated Pest Management in Controlling Ticks and Tick-Associated Diseases
Kirby C Stafford, III, Scott C Williams, Goudarz Molaei
Journal of Integrated Pest Management, online first, 17 October 2017.
In this paper, we review surveyed human behaviors and risks for exposure to ticks, concepts pertinent to integrated pest management for ticks, simulation models, various tick control strategies, integrated tick management studies, and highlight what is needed going forward. Increased education and communication between physicians and veterinarians is essential to address tick-associated diseases in a ‘one health’ approach and unify the animal and human branches of medicine to identify, treat, and implement preventive measures.

Pet ownership increases human risk of encountering ticks
Jones EH, Hinckley AF, Hook SA, Meek JI, Backenson B, Kugeler KJ, Feldman KA.
Zoonoses and Public Health, online first 2017 Jun 19.
We examined whether pet ownership increased the risk for tick encounters and tickborne disease among residents of three Lyme disease-endemic states as a nested cohort within a randomized controlled trial. Information about pet ownership, use of tick control for pets, property characteristics, tick encounters and human tickborne disease were captured through surveys, and associations were assessed using univariate and multivariable analyses.Pet-owning households had 1.83 times the risk (95% CI = 1.53, 2.20) of finding ticks crawling on and 1.49 times the risk (95% CI = 1.20, 1.84) of finding ticks attached to household members compared to households without pets.

An Up-Close Look at the Tiny Sensory Pits That Ticks Use to Smell
By Meredith Swett Walker, Entomology Today, Annapolis, Maryland
If you ever find a tick before it finds you – that is when it’s still hanging out on vegetation hoping you’ll brush past it – you may notice the little bloodsucker waving its “arms in the air like it just don’t care.” But ticks aren’t fans of 1980’s hip hop. They’re waving their arms because they are trying to get a whiff of you. While insects primarily smell with their antennae, ticks are not insects; rather, they’re arachnids, and they don’t have antennae. Instead, a tick smells using a structure on its forelegs called the Haller’s organ.

Accelerated phenology of blacklegged ticks under climate warming
Taal Levi, Felicia Keesing, Kelly Oggenfuss, Richard S. Ostfeld
Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 2015 Apr 5; 370(1665).
Here, we use 19 years of data on blacklegged ticks attached to small-mammal hosts to quantify the relationship between climate warming and tick phenology. Warmer years through May and August were associated with a nearly three-week advance in the phenology of nymphal and larval ticks relative to colder years, with little evidence of increased synchrony.Warmer Octobers were associated with fewer larvae feeding concurrently with nymphs during the following spring. Projected warming by the 2050s is expected to advance the timing of average nymph and larva activity by 8-11 and 10-14 days, respectively. If these trends continue, climate warming should maintain or increase transmission of persistent pathogens, while it might inhibit pathogens that do not produce long-lasting infections.

Effectiveness of Residential Acaricides to Prevent Lyme and Other Tickborne Diseases in Humans.
Hinckley AF, Meek JI, Ray JA, Niesobecki SA, Connally NP, Feldman KA, Jones EH, Backenson PB, White JL, Lukacik G, Kay AB, Miranda WP, Mead PS.
The Journal of Infectious Diseases, online first 2016 Jan 5.
In the northeastern United States, tickborne diseases are a major public health concern. In controlled studies, a single springtime application of acaricide has been shown to kill between 68 and 100% of ticks. Although public health authorities recommend use of acaricides to control tick populations in yards, the effectiveness of these pesticides to prevent tick bites or human tickborne diseases is unknown.Although abundance of questing ticks was significantly lower (63%) on acaricide-treated properties, there was no difference between treatment groups in human-tick encounters, self-reported or medical record-validated tickborne diseases.Used as recommended, acaricide barrier sprays do not significantly reduce household risk of tick exposure or tickborne disease. Measures for preventing tickborne diseases should be evaluated against human outcomes to confirm effectiveness.

Scientists Have Sequenced the Genome of the Tick that Transmits Lyme Disease
Entomology Today, Entomological Society of America, Annapolis, Maryland
February 29, 2016
An international team of scientists led by Purdue University has sequenced the genome of the tick that transmits Lyme disease, the most common vector-borne illness in North America. Ixodes scapularis, known as the blacklegged tick or the deer tick, is the first tick species to have its genome sequenced. The decade-long project, involving 93 authors from 46 institutions, decodes the biology of an arachnid with sophisticated spit, barbed mouthparts, and millions of years of successful parasitism. The genome of Ixodes scapularis also sheds light on how ticks acquire and transmit pathogens and offers tick-specific targets for control.

Different Populations of Blacklegged Tick Nymphs Exhibit Differences in Questing Behavior That Have Implications for Human Lyme Disease Risk.
Arsnoe IM, Hickling GJ, Ginsberg HS, McElreath R, Tsao JI.
PLoS One. 2015 May 21;10(5):e0127450.
We studied the questing (= host-seeking) behavior of blacklegged tick (Ixodes scapularis) nymphs, which are the primary vectors of Lyme disease in the eastern United States. Our findings suggest that southern origin I. scapularis nymphs rarely emerge from the leaf litter, and consequently are unlikely to contact passing humans. We propose that this difference in questing behavior accounts for observed geographic differences in the efficacy of the standard sampling techniques used to collect questing nymphs. These findings also support our hypothesis that very low Lyme disease incidence in southern states is, in part, a consequence of the type of host-seeking behavior exhibited by southern populations of the key Lyme disease vector.

Meteorological Influences on the Seasonality of Lyme Disease in the United States
Moore SM, Eisen RJ, Monaghan A, Mead P.
American Journal of Tropical Medicine and Hygiene, online before print 2014 Jan 27.
An earlier beginning to the LD season was positively associated with higher cumulative growing degree days through Week 20, lower cumulative precipitation, a lower saturation deficit, and proximity to the Atlantic coast. The timing of the peak and duration of the LD season were also associated with cumulative growing degree days, saturation deficit, and cumulative precipitation, but no meteorological predictors adequately explained the timing of the end of the LD season.

The impact of temperature and precipitation on blacklegged tick activity and Lyme disease incidence in endemic and emerging regions
Burtis JC, Sullivan P, Levi T, Oggenfuss K, Fahey TJ, Ostfeld RS.
Parasites & Vectors. 2016 Nov 25;9(1):606.
Recently endemic regions showed an increase in Lyme disease incidence over time, while incidence in long-term endemic regions appears to have stabilized. Only within the stabilized areas were we able to detect reduced Lyme disease incidence in years with hot, dry summer weather. These patterns were reflected in our field data, which showed that questing activity of nymphal I. scapularis was reduced by hot, dry summer weather.

Bioassays to evaluate non-contact spatial repellency, contact irritancy, and acute toxicity of permethrin-treated clothing against nymphal Ixodes scapularis ticks
Lars Eisen, Dominic Rose, Robert Prose, Nicole E. Breuner, Marc C. Dolan, Karen Thompson, Neeta Connally
Ticks and Tick-borne Diseases, online first July 1, 2017.
Our results indicate that permethrin-treated textiles provide minimal non-contact spatial repellency but strong contact irritancy against ticks, manifesting as a “hot-foot” effect and resulting in ticks actively dislodging from contact with vertically oriented treated textile. Preliminary data suggest that the contact irritancy hot-foot response may be weaker for field-collected nymphs as compared with laboratory-reared nymphs placed upon permethrin-treated textile. We also demonstrate that contact with permethrin-treated textiles negatively impacts the vigor and behavior of nymphal ticks for >24 hr, with outcomes ranging from complete lack of movement to impaired movement and unwillingness of ticks displaying normal movement to ascend onto a human finger.

Flying ticks: anciently evolved associations that constitute a risk of infectious disease spread
de la Fuente J, Estrada-Peña A, Cabezas-Cruz A, Brey R.
Parasites & Vectors. 2015 Oct 15;8(1):538.
Birds are central elements in the ecological networks of ticks, hosts and TBP. The study of host-tick-pathogen associations reveals a prominent role for birds in the dissemination of Borrelia spp. and Anaplasma phagocytophilum, with little contribution to the possible dissemination of other TBP. Birds have played a major role during tick evolution, which explains why they are by far the most important hosts supporting the ecological networks of ticks and several TBP.

Deer, predators, and the emergence of Lyme disease
Taal Levi, A. Marm Kilpatrick, Marc Mangel, and Christopher C. Wilmers
Proceedings of the National Academy of Sciences of the
United States of America, online before print, June 18, 2012.
Across four states we find poor spatial correlation between deer abundance and Lyme disease incidence, but coyote abundance and fox rarity effectively predict the spatial distribution of Lyme disease in New York. These results suggest that changes in predator communities may have cascading impacts that facilitate the emergence of zoonotic diseases, the vast majority of which rely on hosts that occupy low trophic levels.

Rickettsia rickettsii Transmission by a Lone Star Tick, North Carolina
Edward B. Breitschwerdt, Barbara C. Hegarty, Ricardo G.
Maggi, Paul M. Lantos, Denise M. Aslett, and Julie M. Bradley
Emerging Infectious Diseases, Volume 17, Number 5 – May 2011.
Only indirect or circumstantial evidence has been published to support transmission of Rickettsia rickettsii by Amblyomma americanum (lone star) ticks in North America. This study provides molecular evidence that A. americanum ticks can function, although most likely infrequently, as vectors of Rocky Mountain spotted fever for humans.

Bartonella henselae and B. koehlerae DNA in birds
Mascarelli PE, McQuillan M, Harms CA, Harms RV, Breitschwerdt EB.
Emerging Infectious Diseases March 2014
There is growing evidence that migratory birds serve as reservoirs and/or mechanical vectors for pathogens such as tick-borne encephalitis virus and Rickettsia spp.. Birds have been implicated as reservoirs for several Borrelia spp. and for possible dispersion of other tick-borne pathogens (e.g., Anaplasma and Bartonella spp.)

Assessing the Contribution of Songbirds to the Movement of Ticks and Borrelia burgdorferi in the Midwestern United States During Fall Migration
Sarah C. Schneider, Christine M. Parker, James R. Miller, L. Page Fredericks, Brian F. Allan
EcoHealth, online before print, October 9, 2014.
Infestation of birds by Ixodes spp. differed significantly by region, while B. burgdorferi infection did not. These data suggest that migratory birds may play a larger role in the dispersal of B. burgdorferi than previously realized.

Multiflora rose invasion amplifies prevalence of Lyme disease pathogen, but not necessarily Lyme disease risk.
Adalsteinsson SA, Shriver WG, Hojgaard A, Bowman JL, Brisson D, D’Amico V, Buler JJ.
Parasites & Vectors, online first 2018 Jan 23;11(1):54.
Understory structure provided by non-native, invasive shrubs appears to aggregate ticks and reservoir hosts, increasing opportunities for pathogen transmission. However, when we consider pathogen prevalence among nymphs in context with relative abundance of questing nymphs, invasive plants do not necessarily increase disease risk. Although pathogen prevalence is greater among ticks in invaded forests, the probability of encountering an infected tick remains greater in uninvaded forests characterized by thick litter layers, sparse understories, and relatively greater questing tick abundance in urban landscapes.

Environmental Factors Affecting Survival of Immature Ixodes scapularis and Implications for Geographical Distribution of Lyme Disease: The Climate/Behavior Hypothesis
Howard S. Ginsberg, Marisa Albert, Lixis Acevedo, Megan C. Dyer, Isis M. Arsnoe, Jean I. Tsao, Thomas N. Mather, Roger A. LeBrun
PLOS One, published online, January 11, 2017
Recent reports suggest that host-seeking nymphs in southern populations of Ixodes scapularis remain below the leaf litter surface, while northern nymphs seek hosts on leaves and twigs above the litter surface. This behavioral difference potentially results in decreased tick contact with humans in the south, and fewer cases of Lyme disease. We studied whether north-south differences in tick survival patterns might contribute to this phenomenon.

Population and Evolutionary Genomics of Amblyomma americanum, an Expanding Arthropod Disease Vector
Javier D. Monzón, Elizabeth G. Atkinson, Brenna M. Henn, and Jorge L. Benach
Genome Biology and Evolution. 2016; 8:1351-1360. Online first, April 13, 2016.
The lone star tick, Amblyomma americanum, is an important disease vector and the most frequent tick found attached to humans in the eastern United States. The lone star tick has recently experienced a rapid range expansion into the Northeast and Midwest, but despite this emerging infectious threat to wildlife, livestock, and human health, little is known about the genetic causes and consequences of the geographic expansion.

Suppression of Host-Seeking Ixodes Scapularis and Amblyomma Americanum (Acari: Ixodidae) Nymphs After Dual Applications of Plant-Derived Acaricides in New Jersey
Jordan RA, Dolan MC, Piesman J, Schulze TL.
Journal of Economic Entomology, Volume 104, Number 2, April 2011, pp. 659-664.
Of the three compounds tested, 2% nootkatone provided the most consistent results, with 96.5 and 91.9% control of I. scapularis and A. americanum through 42 and 35 d, respectively. The ability of plant-derived natural products to quickly suppress and maintain significant control of populations of these medically important ticks may represent a future alternative to the use of conventional synthetic acaricides. In addition, the demonstrated efficacy of properly-timed backpack sprayer application may enable homeowner access to these minimal-risk acaricides.

Amblyomma americanum (Acari: Ixodidae) Ticks Are Not Vectors of the Lyme Disease Agent, Borrelia burgdorferi (Spirocheatales: Spirochaetaceae): A Review of the Evidence
Ellen Y Stromdahl, Robyn M Nadolny, Graham J Hickling, Sarah A Hamer, Nicholas H Ogden, Cory Casal, Garrett A Heck, Jennifer A Gibbons, Taylor F Cremeans. Mark A Pilgard
Journal of Medical Entomology, online first 31 January 2018.
In total, 54 surveys from more than 35 research groups, involving more than 52,000 ticks, have revealed a low prevalence of B. lonestari, and scarce B. burgdorferi, in A. americanum. In Lyme disease-endemic areas, A. americanum commonly feeds on B. burgdorferi-infected hosts; the extremely low prevalence of B. burgdorferi in this tick results from a saliva barrier to acquiring infection from infected hosts. At least nine transmission experiments involving B. burgdorferi in A. americanum have failed to demonstrate vector competency. Advancements in molecular analysis strongly suggest that initial reports of B. burgdorferi in A. americanum across many states were misidentified B. lonestari, or DNA contamination, yet the early reports continue to be cited without regard to the later clarifying studies. In this article, the surveillance and vector competency studies of B. burgdorferi in A. americanum are reviewed, and we conclude that A. americanum is not a vector of B. burgdorferi.

Ability of Two Commercially Available Host-Targeted Technologies to Reduce Abundance of Ixodes scapularis (Acari: Ixodidae) in a Residential Landscape
Jordan RA, Schulze TL.
Journal of Medical Entomology, online first 2019 Apr 15.
Host-targeted technologies provide an alternative to the use of conventional pesticide applications to reduce the abundance of Ixodes scapularis Say, the vector for an array of tick-associated human diseases. We compared the ability of Damminx Tick Tubes (Damminix) and SELECT Tick Control System (Select TCS) bait boxes to control host-seeking I. scapularis nymphs in a wooded residential environment.
Deployment of Damminix resulted in 27.6 and 20.3% control of questing nymphs in treated areas at 1 yr and 2 yr postintervention, while Select TCS bait boxes provided 84.0 and 79.1% control, respectively. The economics of residential tick control using these products in wooded residential landscapes is discussed.

Repellence of essential oils and selected compounds against ticks – A systematic review
Benelli G, Pavela R.
Acta Tropica, online first, 2017 Dec 26.
The use of natural products as active ingredients in eco-friendly repellent formulations is currently a prominent research area, due to the wide diversity and high effectiveness of a number of plant-borne compounds, with special reference to essential oils (EOs) extracted from medicinal and aromatic species. Here, we reviewed current knowledge available on EOs tested as repellents against tick species of veterinary importance. Furthermore, we analysed the effectiveness of pure compounds isolated from EOs as tick repellents and their potential implications for practical use in the “real world”. A quantitative analysis of literature available is this research field was provided, along with its impact (i.e., in terms of citations over time) on the scientific community of researchers in tick control science and natural product chemistry.

Repelling Bugs With The Essence Of Grapefruit
by Richard Knox, National Public Radio, Washington, DC
April 18, 2011
That’s why the CDC is pushing hard to develop a completely natural insect repellent made from a chemical called nootkatone, which is found in Alaska yellow cedar trees and citrus fruit.

Pilot Study Assessing the Effectiveness of Long-Lasting Permethrin-Impregnated Clothing for the Prevention of Tick Bites
Meagan F. Vaughn, Steven R. Meshnick. Vector-Borne and
Zoonotic Diseases, online ahead of print, March 11, 2011.
Results: Subjects wearing Insect Shield-treated clothing had a 93% reduction (p<0.0001) in the total incidence of tick bites compared to subjects using standard tick bite prevention measures. Conclusion: This study provides preliminary evidence that long-lasting permethrin-impregnated clothing may be highly effective against tick bites.

Tick bite protection with permethrin-treated summer-weight clothing
Miller NJ, Rainone EE, Dyer MC, Gonzalez ML, Mather TN
Journal of Medical Entomology, 2011 Mar; 48(2):327-33.
Subjects wearing outfits treated with permethrin received 3.36 times fewer tick bites than subjects wearing untreated outfits. No statistically significant differences in number of tick bites were detected between commercial permethrin treatment (19.33%) and the do-at-home permethrin application method (24.67%). The success of permethrin-treated clothing in reducing tick bites varied depending on the specific article of clothing. Subjects wearing permethrin-treated sneakers and socks were 73.6 times less likely to have a tick bite than subjects wearing untreated footware. Subjects wearing permethrin-treated shorts and T-shirts were 4.74 and 2.17 times, respectively, less likely to receive a tick bite in areas related to those specific garments than subjects wearing untreated shorts and T-shirts. Ticks attached to subjects were classified as alive or dead before removal. On subjects wearing untreated outfits, 97.6% of attached nymphs were alive, whereas significantly fewer (22.6%) attached nymphs were alive onsubjects wearing repellent-treated outfits. Results of this study demonstrate the potential of permethrin-treated summer clothing for significantly reducing tick bites and tick-borne pathogen transmission.

The heat is on: Killing blacklegged ticks in residential washers and dryers to prevent tickborne diseases
Nelson CA, Hayes CM, Markowitz MA, Flynn JJ, Graham AC, Delorey MJ, Mead PS, Dolan MC
Ticks and Tick-borne Diseases, online first, 2016 Apr 28.
Reducing exposure to ticks can help prevent Lyme disease and other tickborne diseases. Although it is currently recommended to dry clothes on high heat for one hour to kill ticks on clothing after spending time outdoors, this recommendation is based on a single published study of tick survival under various washing conditions and a predetermined one-hour drying time.We conducted a series of tests to investigate the effects of temperature, humidity, and drying time on killing nymphal and adult blacklegged ticks (Ixodes scapularis). Muslin bags containing 5 ticks each were washed then dried or dried only with six cotton towels during each drying cycle. All nymphal and adult ticks were killed when exposed to wash cycles when the water temperature reached =54 °C (=130 °F); however, 50% of ticks survived hot water washes when the water temperature was <54 °C. The majority (94%) of ticks survived warm washes [temperature range, 27–46 °C (80–115 °F)] and all ticks survived cold washes [15–27 °C (59–80 °F)].When subsequently dried on high heat setting [54–85 °C (129–185 °F)], it took 50 min to kill all ticks (95% confidence limit, 55 min). Most significantly, we found that all adult and nymphal ticks died when placed directly in the dryer with dry towels and dried for 4 min on high heat (95% confidence limit, 6 min). We have identified effective, easily implemented methods to rid clothing of ticks after spending time outdoors.Placing clothing directly in a dryer and drying for a minimum of 6 min on high heat will effectively kill ticks on clothing. If clothing is soiled and requires washing first, our results indicate clothing should be washed with water temperature =54 °C (=130 °F) to kill ticks. When practiced with other tick-bite prevention methods, these techniques could further reduce the risk of acquiring tickborne diseases.

Tick Humoral Responses: Marching to the Beat of a Different Drummer
Oliva Chávez AS, Shaw DK, Munderloh UG, Pedra JH.
Frontiers in Microbiology, 2017 Feb 14;8:223. eCollection 2017.
Ticks transmit a variety of human pathogens, including Borrelia burgdorferi, the etiological agent of Lyme disease. Multiple pathogens that are transmitted simultaneously, termed “coinfections,” are of increasing importance and can affect disease outcome in a host. Arthropod immunity is central to pathogen acquisition and transmission by the tick.

Vector competence of the blacklegged tick, Ixodes scapularis, for the recently recognized Lyme borreliosis spirochete Borrelia mayonii
Marc C. Dolan, Andrias Hojgaard, J. Charles Hoxmeier, Adam J. Replogle, Laurel B. Respicio-Kingry, Christopher Sexton, Martin A. Williams, Bobbi S. Pritt, Martin E. Schriefer, Lars Eisen
Ticks and Tick-borne Diseases, online first, February 12, 2016.
A novel species within the Borrelia burgdorferi sensu lato complex, provisionally named Borrelia mayonii, was recently found to be associated with Lyme borreliosis in the Upper Midwest of the United States.Our results demonstrate that I. scapularis is capable of serving as a vector of B. mayonii. This finding, together with data showing that field-collected I. scapularis are infected with B. mayonii, indicate that I. scapularis likely is a primary vector to humans of this recently recognized Lyme borreliosis spirochete.

Characterizing the relationship between tick bites and Lyme disease in active component U.S. Armed Forces in the eastern United States
Rossi C, Stromdahl EY, Rohrbeck P, Olsen C, DeFraites RF.
Medical Surveillance Monthly Report. 2015 Mar;22(3):2-10.
In the population of service members in the study sample, mean annual LD incidence was 52.2 per 100,000 person-years (95% CI±; 7.6 per 100,000) between 1 January 2006 and 31 December 2012. A 10% increase in the rate of ticks submitted to the HTTKP corresponded to an increase in LD incidence of 5.7% (p<0.01). Where Borrelia burgdorferi infection of Ixodes scapularis ticks was high (20% or greater tick infection prevalence), tick removal rates explained 53.7% of the annual variation in LD incidence (p=0.01)

A Tick Vector Transmission Model of Monocytotropic Ehrlichiosis
Saito TB, Walker DH.
The Journal of Infectious Diseases, online before print, 2015 Mar 3.
For the first time we were able to develop a tick transmission model with an Ehrlichia that is pathogenic for humans.

Occurrence of soil- and tick-borne fungi and related virulence tests for pathogenicity to Ixodes scapularis (Acari: Ixodidae).
Greengarten PJ, Tuininga AR, Morath SU, Falco RC, Norelus H, Daniels TJ.
Journal of Medical Entomology, 2011 Mar; 48(2):337-44.
Currently, only a few entomopathogenic fungal species are considered virulent to ticks. We hypothesized that these species may not represent the most abundant local taxa that would be pathogenic to ticks in situ.In laboratory bioassays, 15 fungal taxa were found to be significantly virulent, although none of these were previously considered common pathogens of I. scapularis. Two species, Hypocrea lixii Patouillard 1891 and Penicillium soppii K. M. Zalessky 1927, were tested in field trials by spraying suspensions on forested plots. Mean tick mortality was 71% after treatment with H. lixii, 58% after treatment with P. soppii, and 32% in the control plots.

The Lyme Disease Pathogen Has No Effect on the Survival of Its Rodent Reservoir Host
Voordouw MJ, Lachish S, Dolan MC.
PLoS One. 2015 Feb 17;10(2):e0118265.
Zoonotic pathogens that cause devastating morbidity and mortality in humans may be relatively harmless in their natural reservoir hosts. The tick-borne bacterium Borrelia burgdorferi causes Lyme disease in humans. We analyzed four years of capture-mark-recapture (CMR) data on a population of white-footed mice, Peromyscus leucopus, to test whether B. burgdorferi and its tick vector affect the survival of this important reservoir host. We used a multi-state CMR approach to model mouse survival and mouse infection rates as a function of a variety of ecologically relevant explanatory factors. We found no effect of B. burgdorferi infection or tick burden on the survival of P. leucopus.

Ecological factors influencing small mammal infection by Anaplasma phagocytophilum and Borrelia burgdorferi s.l. in agricultural and forest landscapes
Perez G, Bastian S, Chastagner A, Agoulon A, Plantard O, Vourc’h G, Butet A.
Environmental Microbiology, online first 2017 Aug 11.
Small mammals are key components of numerous tick-borne disease systems, as hosts for immature ticks and pathogen reservoirs. To study the factors influencing tick-borne infection in small mammals, we trapped small mammals and collected questing ticks in spring and autumn in 2012 and 2013 at 24 sites in a 10×15 km rural landscapes (Brittany, France).Tissue samples were screened by real-time PCR for Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato. Of the two dominant small mammal species captured, bank voles (Myodes glareolus) had higher prevalence than wood mice (Apodemus sylvaticus) for both infections, presumably because of specific differences in immunological defenses. Prevalence of infections was higher in 2013 than in 2012, likely because small mammals were fivefold less abundant in 2013, favoring tick aggregation.Bacterial prevalence, which was higher in autumn, was not associated to questing Ixodes ricinus nymph abundance which was 6 times higher in spring, but rather to the structure of the small mammal community. These findings suggest the involvement of endophilic tick species, I. trianguliceps and/or I. acuminatus, in bacterial transmission.

Deer ked: a Lyme-carrying ectoparasite on the move
Kelsey A, Finch J.
Cutis 2018 Aug;102(2):121-122.
or http://bit.ly/2OLohbk
Lipoptena cervi, known as the deer ked, is an ectoparasite of cervids traditionally found in northern European countries such as Norway, Sweden, and Finland. Although rarely reported in the United States, this vector recently has been shown to carry Borrelia burgdorferi and Anaplasma phagocytophylum from specimens collected domestically.
Importantly, it has been suggested that deer keds are one of the many disease-carrying vectors that are now found in more expansive regions of the world due to climate change. We report a rare sighting of L cervi in Connecticut. Additionally, we captured a high-resolution photograph of a deer ked that can be used by dermatologists to help identify this disease-carrying ectoparasite.

Improving access to appropriate post-exposure doxycycline for Lyme disease prophylaxis: role for community pharmacies.
Dering-Anderson AM, Adams AJ.
Journal of Antimicrobial Chemotherapy. Online first, 2018 Sep 14.
The transmission of Borrelia burgdorferi to humans through tick bites results in Lyme disease. Appropriate therapy for Lyme disease is antibacterial drugs, most often doxycycline. Patients often approach community pharmacists for self-care assistance with the symptoms of Lyme disease: fever, headache, fatigue and skin rash.
Pharmacists with the patient history are trained and capable of appropriately dispensing doxycycline to treat these patients and prevent the spread of infection to the joints, nerves or heart. We challenge restrictions to the appropriate and timely provision of therapy for Lyme disease and encourage the use of community pharmacists in managing these patients.

An Invasive New Tick Is Spreading in the U.S.
By Donald G. McNeil Jr., The New York Times, New York, NY
August 6, 2018
For the first time in 50 years, a new tick species has arrived in the United States – one that in its Asian home range carries fearsome diseases.
The Asian long-horned tick, Haemaphysalis longicornis, is spreading rapidly along the Eastern Seaboard. It has been found in seven states and in the heavily populated suburbs of New York City.
At the moment, public health experts say they are concerned, but not alarmed.

Lyme Disease Transmission Risk: Seasonal Variation in the Built Environment
Roome A, Spathis R, Hill L, Darcy JM, Garruto RM.
Healthcare. 2018 Jul 19;6(3).
Seasonal variation in spatial distribution and pathogen prevalence of Borrelia burgdorferi in blacklegged ticks (Ixodes scapularis) influences human population risk of Lyme disease in peri-urban built environments. Parks, gardens, playgrounds, school campuses and neighborhoods represent a significant risk for Lyme disease transmission.
From June 2012 through May 2014, ticks were collected using 1 m2 corduroy cloths dragged over low-lying vegetation parallel to walkways with high human foot traffic. DNA was extracted from ticks, purified and presence of B. burgdorferi assessed by polymerase chain reaction amplification.
Summer is reported as the time of highest risk for Lyme disease transmission in the United States and our results indicate a higher tick density of 26.0/1000 m2 in summer vs. 0.2/1000 m2 to 10.5/1000 m2 in spring and fall. However, our findings suggest that tick infection rate is proportionally higher during the fall and spring than summer (30.0–54.7% in fall and 36.8–65.6% in spring vs. 20.0–28.2% in summer).
Seasonal variation in infected tick density has significant implications for Lyme disease transmission as people are less likely to be aware of ticks in built environments, and unaware of increased infection in ticks in spring and fall. These factors may lead to more tick bites resulting in Lyme infection.

Fatal attraction: lone star ticks (Amblyomma americanum) exhibit preference for human female breath over male breath
Tanya Josek, Allison M. Gardner, Tyler J. Hedlund, Allison T. Parker, Erin Allmann Updyke, Brian F. Allan
Experimental and Applied Acarology, online first 10 January 2019.
We focused on the lone star tick, Amblyomma americanum, due to its importance as a disease vector in the United States and its active host-seeking behavior. To test the hypothesis that ticks exhibit preference based upon host sex, we conducted a binary choice behavioral bioassay. Male and female human volunteers (n = 20 pairs) breathed into opposite sides of a secured polycarbonate tube containing 10 adult A. americanum and the proportion of ticks that exhibited a host preference was recorded.
We found that under controlled conditions, human females attract a significantly larger proportion of ticks than males. Possible mechanisms to explain these results include that (1) female breath contains components that ticks find attractive, and/or (2) male breath contains a repellent chemical component.

Study finds tiny larval ticks can transmit Borrelia miyamotoi
Lyme Science Blog, by Daniel Cameron, MD, MPH, Mt. Kisco, New York
March 25, 2019
Nymphal and adult black-legged ticks, also known as deer ticks, harbor a growing number of pathogens. But researchers are now discovering that larval ticks, which are even smaller, may pose an equal threat to public safety as a new study describes larval ticks infected with the tick-borne bacteria Borrelia miyamotoi.
(Back to top)

(Return to research home page)