Archive for the ‘Babesia’ Category

Review of Tick Attachment Time For Different Pathogens

http://dx.doi.org/10.3390/environments4020037

Stephanie L. Richards, Ricky Langley, Charles S. Apperson and Elizabeth Watson 

Abstract

Improvements to risk assessments are needed to enhance our understanding of tick-borne disease epidemiology.

We review tick vectors and duration of tick attachment required for pathogen transmission for the following pathogens/toxins and diseases: (1) Anaplasma phagocytophilum (anaplasmosis); (2) Babesia microti (babesiosis); (3) Borrelia burgdorferi (Lyme disease); (4) Southern tick-associated rash illness; (5) Borrelia hermsii (tick-borne relapsing fever); (6) Borrelia parkeri (tick-borne relapsing fever); (7) Borrelia turicatae (tick-borne relapsing fever); (8) Borrelia mayonii; (9) Borrelia miyamotoi; (10) Coxiella burnetii (Query fever); (11) Ehrlichia chaffeensis (ehrlichiosis); (12) Ehrlichia ewingii (ehrlichiosis); (13) Ehrlichia muris; (14) Francisella tularensis (tularemia); (15) Rickettsia 364D; (16) Rickettsia montanensis; (17) Rickettsia parkeri (American boutonneuse fever, American tick bite fever); (18) Rickettsia ricketsii (Rocky Mountain spotted fever); (19) Colorado tick fever virus (Colorado tick fever); (20) Heartland virus; (21) Powassan virus (Powassan disease); (22) tick paralysis neurotoxin; and (23) Galactose-α-1,3-galactose (Mammalian Meat Allergy-alpha-gal syndrome).

Published studies for 12 of the 23 pathogens/diseases showed tick attachment times. Reported tick attachment times varied (<1 h to seven days) between pathogen/toxin type and tick vector. Not all studies were designed to detect the duration of attachment required for transmission. Knowledge of this important aspect of vector competence is lacking and impairs risk assessment for some tick-borne pathogens.

**Highlights**

The researchers point out that unlike mosquitoes which rely on saliva for transmission, ticks can transmit via saliva, regurgitation of gut contents, and also via the cement-like secretion used to secure itself to the host (hard ticks).  Published data on transmission times relies upon rodent studies showing 15–30 min for Powassan, anywhere from 4-96 hours for bacteria, 7–18 days for the protozoan Babesia microti, and 5-7 days for neurotoxin (Tick Paralysis). For soft ticks, attachment time of 15 sec–30 min was required for transmission of Borrelia turicata (Tick Relapsing Fever).

The challenge with these studies, and there are many, is that most placed multiple ticks on multiple rodents.  Multiple ticks may be transmitting different pathogens.  It has also been shown that ticks feeding on mice coinfected with B. microti and B. burgdorferi were twice as likely to become infected with Bb compared to B. microti, suggesting that coinfection can amplify certain pathogens – which is another reason to only use one rodent and one pathogen to separate out multiplying factors to muddy the waters.  Also, rarely do studies record the titer of both tick and host – again, making it nearly impossible to determine what’s what.  It was also noted that transmission times are unknown for many pathogens.

**And as always:  if you are the ONE person who contracted Lyme Disease in 10 minutes, all these numbers are essentially meaningless.  The frightening truth is that these numbers, along with geographical information regarding tick habitats, are often used against patients.  It is beyond time for doctors to listen, educate themselves, and treat patients with the respect they deserve – not to mention it’s time for them to treat patients clinically and not based on tests that are wrong over half the time and with the knowledge that ticks are spreading everywhere and bringing the pathogens with them. (In other words, throw the maps away!)

The review essentially gives the following transmission times for various pathogens. Again, please know these numbers are not definitive and many, many cases have proven this fact.

Take each and every tick bite seriously and don’t mess around and take a “wait and see approach.”  There is too much at stake.

Transmission Times noted in review:

Anaplasmosis: 24 hours and increased dramatically after 48-50 hours.  It is possible for it to be transmitted transovarially (from mom to baby tick) and it inhabit’s the salivary glands more frequently than the mid-gut.

Babesiosis:  Greater than 36 hours, 17% after 48 hours, and 50% after 54 hours.  Can be transmitted transovarially and transstadially (pathogen stays with tick from one stage to the next).  Ticks feeding on mice coinfected with B. microti and B. burgdorferi were twice as likely to become infected with Bb compared to B. microti.

Lyme Disease (Borrelia burgdorferi):  24 hours; however, the researchers comment that there are questions regarding previous transmission studies.  They also commented that there may be a difference in attachment time between nymphs and adult females. Transovarian transmission is unknown.

Tick Relapsing Fever (Borrelia turnicatae, B. hermsii):  15 and 30 seconds respectively.  Transovarian transmission is unknown.

Borreliosis (Borrelia mayonii):  24 hours.  Transovarian transmission is unknown.

Borrelia myamotoi Disease:  24 hours.  Transovarial transmission occurs.

Tularemia (Francisella tularensis):  Not assessed.  Can be transmitted mechanically by deer flies, horse flies, mosquitoes, aerosol/ingestion when processing/eating infected animal tissues.  Can be transmitted transtadially and transovarially.

Rocky Mountain Spotted Fever (Rickettsia rickettsii):  10-20 hours.  Can be transmitted transovarially.

Heartland Virus:  Not assessed.  Can be transmitted transovarially and transstadially.

Powassan Virus:  15 Minutes; however, it is possible it was sooner since the first they checked for transmission was 15 minutes.  Can be transmitted transovarially.

Tick Paralysis (Neurotoxin):  2-6 days.

Alpha Gal/Mammalian Meat Allergy (Galactose-a-1,3-Galactose):  Not assessed.  Transovarian transmission is unknown.

For more on transmission times, please read:  https://madisonarealymesupportgroup.com/2017/04/14/transmission-time-for-lymemsids-infection/

 

 

Co-infection of Ticks: The Rule Rather Than the Exception

http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0004539

Sara Moutailler, Claire Valiente Moro, Elise Vaumourin, Lorraine Michelet, Florence Hélène Tran, Elodie Devillers, Jean-François Cosson, Patrick Gasqui, Van Tran Van, Patrick Mavingui, Gwenaël Vourc’h, Muriel Vayssier-Taussat
Published: March 17, 2016  https://doi.org/10.1371/journal.pntd.0004539

Abstract

Introduction

Ticks are the most common arthropod vectors of both human and animal diseases in Europe, and the Ixodes ricinus tick species is able to transmit a large number of bacteria, viruses and parasites. Ticks may also be co-infected with several pathogens, with a subsequent high likelihood of co-transmission to humans or animals. However few data exist regarding co-infection prevalences, and these studies only focus on certain well-known pathogens. In addition to pathogens, ticks also carry symbionts that may play important roles in tick biology, and could interfere with pathogen maintenance and transmission. In this study we evaluated the prevalence of 38 pathogens and four symbionts and their co-infection levels as well as possible interactions between pathogens, or between pathogens and symbionts.

Methodology/principal findings

A total of 267 Ixodes ricinus female specimens were collected in the French Ardennes and analyzed by high-throughput real-time PCR for the presence of 37 pathogens (bacteria and parasites), by rRT-PCR to detect the presence of Tick-Borne encephalitis virus (TBEV) and by nested PCR to detect four symbionts. Possible multipartite interactions between pathogens, or between pathogens and symbionts were statistically evaluated. Among the infected ticks, 45% were co-infected, and carried up to five different pathogens. When adding symbiont prevalences, all ticks were infected by at least one microorganism, and up to eight microorganisms were identified in the same tick. When considering possible interactions between pathogens, the results suggested a strong association between Borrelia garinii and B. afzelii, whereas there were no significant interactions between symbionts and pathogens.

Conclusion/significance

Our study reveals high pathogen co-infection rates in ticks, raising questions about possible co-transmission of these agents to humans or animals, and their consequences to human and animal health. We also demonstrated high prevalence rates of symbionts co-existing with pathogens, opening new avenues of enquiry regarding their effects on pathogen transmission and vector competence.

Author Summary

Ticks transmit more pathogens than any other arthropod, and one single species can transmit a large variety of bacteria and parasites. Because co-infection might be much more common than previously thought, we evaluated the prevalence of 38 known or neglected tick-borne pathogens in Ixodes ricinus ticks. Our results demonstrated that co-infection occurred in almost half of the infected ticks, and that ticks could be infected with up to five pathogens. Moreover, as it is well established that symbionts can affect pathogen transmission in arthropods, we also evaluated the prevalence of four symbiont species and demonstrated that all ticks were infected by at least one microorganism. This work highlights the co-infection phenomenon in ticks, which may have important implications for human and animal health, emphasizing the need for new diagnostic tests better adapted to tick-borne diseases. Finally, the high co-occurrence of symbionts and pathogens in ticks, reveals the necessity to also account for these interactions in the development of new alternative strategies to control ticks and tick-borne disease.

To which we all said AMEN!

A few notes on the study:  To see a chart showing exactly what coinfections and symbionts they looked at, go to the link for the study.  They looked at 6 strains of borrelia (Lyme), Anaplasma, Ricketssia helvetica, Bartonella, Babesia, and Neoehrlichia mikurensis (Order: Rickettsiales, Family: Anaplasmataceae).  The symbiots looked at were:  Wolbachia, Spiroplasma, Acinetobacter, and Midichloria mitochondri.

While I am unfamiliar with most of the symbionts, Wolbachia concerns me as scientists are actively inserting Wolbachia into mosquitoes and releasing them into the wild in efforts of eradicating Dengue Fever, Chikungunya, yellow fever, and possibly even Malaria.  While scientists claim Wolbachia, a gram-negative bacterium in the family of Rickettsiales, can not infect humans, they can and do infect worms which cause human disease.  Since nematodes have been found in ticks and many Lyme/MSIDS patients have to treat for worms, the question begs to be asked, “Does Wolbachia play a role in Lyme/MSIDS?”  This is a question I plan on writing about, but the answer could very well be, “Yes.”  I certainly pray that more research on Wolbachia in relation to Lyme/MSIDS is done as this could definitely be a fly in the proverbial ointment.

Lastly, I believe recorded coinfection numbers to be abysmally low.  My own LLMD doesn’t even test for them, he feels the tests are that poor.  Also, probably the numbers reflect the most severe cases – leaving many out.  As you are aware, coinfections are notorious for presenting differently than the textbook presentations that most doctors are familiar with. Dr. Horowitz writes and speaks about this often.

Published on Nov 3, 2014
At the “Symposium on Tick-borne Diseases” held May 17, 2014

37:30 You will only find a positive test for Babesia if the level of parasitima in the blood is greater than 5%.  38:05 Medical textbooks also state you should have hemolytic anemia, thrombocytopenia, and renal failure if you have Babesia.  Dr. Horowitz states he has not had one Lyme/MSIDS patient present this way.  

How many doctors are going to think outside their medical textbooks?

Podcast: Lyme Disease and Tick-Borne Co-infections

https://globallymealliance.org/podcast-lyme-disease-tick-borne-co-infections/

PODCAST: LYME DISEASE AND TICK-BORNE CO-INFECTIONS
January 17, 2017

The most common tick-borne infection is Lyme disease. However, infected ticks also carry and spread numerous co-infections.

The newest Global Lyme Alliance podcast, with GLA’s Dr. Harriet Kotsoris and Dr. Mayla Hsu, discusses Lyme disease and the co-infections that are often transmitted along with the initial tick bite. Below is an excerpt.  https://soundcloud.com/user-988784721/lyme-disease-and-tick-borne-co-infections  (Click on this link for the entire podcast or you can fast forward to 13:15 and it will pick up at Bartonella which is where the transcript stops below.  It also goes into viruses and STARI).

Host: In this podcast we’re going to expand our discussion to include co-infecting tick-borne diseases that are often transmitted along with Lyme. I’m in our studio with Dr. Harriet Kotsoris and Dr. Mayla Hsu who are science and research officers at the Global Lyme Alliance. I’ll start off by asking, what is a tick-borne infection?
Dr. Harriet Kotsoris: A tick-borne infection is an infectious disease spread by the bite of an infected tick. The most common is Lyme disease but many others are present in the same tick bite. Depending on the location and the season, up to half of all ticks may have had more than one kind of microbe or disease producing organism that can make humans very sick. The list of microbes is expanding up to 11 or 12 at last count, but we’ll focus today on the major ones. These are called co-infections, the simultaneous infection of a host by multiple pathogenic or disease producing organisms.
There is an increasing number of ticks that are multiply infected as we just said. In a recent west European study of Ixodes ricinus ticks, very similar to the American black legged deer tick, up to 45% of those ticks were co-infected with up to five pathogens or disease producing organisms. We have a similar experience here in the United States.
Host: How many people get tick-borne infections?
Dr. Kotsoris: The Centers for Disease Control calculates about 330,000 Lyme disease cases per year but it may be even over 400,000. It’s not really understood how many of these are also infected with other microbes, which in some cases cause different illnesses that require different diagnostic tests and different treatments.
Host: What can you tell us about the ticks that spread these diseases?
Dr. Mayla Hsu: Well in the United States there are different families of ticks that may be co-infected with various pathogens. As Harriet just mentioned, the Ixodes ticks or the black-legged ticks are now in half of all United States counties. There’s another tick that is further south, known as the Lone Star and there is also an American dog tick called Dermacentor that also harbors infectious microbes.
Host: How about internationally?
Dr. Hsu: Well it seems that ticks are generally found in all temperate climate zones, so there are the Ixodes species in North America, these are also found in Europe and Asia, there are other ticks found in Africa, parts of temperate Africa, that infect humans as well as animals there, and they’re responsible for causing relapsing fevers. There are soft ticks, Ornithodoros, the Ornithodoros family of ticks, that are found in South America and Western Africa, and these too are associated with causing diseases in humans. The jury is still out in Australia. There are ticks there but it’s not known whether or not they’re correlating with human disease.
Host: What do we know about changing tick geography?
Dr. Kotsoris: It seems that in the United States, the geographic range where ticks are found is expanding and we know that with climate change the range is also changing, so for instance, it is expanding northwards into Canada where Lyme disease was never a concern, it now is starting to emerge. We can expect and see more tick-borne diseases elsewhere, also spreading in through the United States. These are now classified as emerging infections and so public health authorities are very concerned about this and tracking the emergence of more tick-borne illnesses.
Host: What are some of the emerging tick-borne diseases and again we’re going to focus only on the major ones about which the most is known.
Dr. Hsu: One of the more interesting tick-borne illnesses that has been emerging in recent years is called babesiosis. This is an illness caused by a parasite that’s very similar to malaria. It’s called Babesia, Babesia microti. This is characterized by recurrent fevers, so people get fevers that spike and then go away and then come back over and over again, chills, muscle and joint aches and pains and it can be actually fatal in rare cases. The diagnostic test for this is not a blood test looking for antibodies, rather the blood is examined under a microscope and here you can see the organism actually growing in red blood cells, so just like malaria it grows in red blood cells and you can see it in a blood smear and the treatment required for this is also very similar to anti-malaria therapies, so that’s drugs that are similar to quinine but also anti-protozoan drugs like Atovaquone, also known as Mepron, and antibiotics, azithromycin and clindamycin.
About 1,800 people were reported to have gotten babesiosis in the year 2013, and the numbers are rising so where we see Lyme disease we are also starting to see more and more Babesia, and it’s important to point out that the treatment and diagnostic for Babesia is different from that of Lyme disease, so if Lyme disease is suspected and is looked for, and treated, a person who also has Babesia will not get adequately diagnosed or treated and can continue to be ill.
Host: There are several bacterial diseases that are spread by ticks that have been getting more attention in recent years, Anaplasma and Ehrlichia.
Dr. Kotsoris: Yes, historically these started out as veterinary diseases. They were identified in the late 80s and early 1990s, after having been studied as long-standing veterinary problems. These organisms belong to a group known as the Rickettsiae, Anaplasma, Ehrlichia, and Rickettsia itself. These are what we call obligate intracellular parasites. They’re bacteria that only live inside the cells of another organism, and that’s how they affect humans. Human granulocytic anaplasmosis is what we call a gram-negative bacterium of the rickettsia family. It invades white blood cells after a tick bite by an infected tick and it travels and lodges within granulocytes or the neutophils, the white blood cells of the human being.
About one to two weeks after the bite, the patient will develop spiking fevers, headache, drop in white blood count, drop in platelet count…the platelets are responsible for clotting blood, and a rise of liver function tests indicative of an inflammation of the liver. These organisms are very smart and release a chemical substance known as a chemokine, or a cytokine, interleukin-8 that actually is an attracting chemical for white blood cells to help propagate the infection throughout the body. The diagnosis has to be made by blood smear because the comparison of acute and convalescent sera that is the development of convalescent antibodies may be too late in the game, that the patient will have been compromised medically and treatment will have been delayed. The diagnosis can also be made by something known as polymerase chain reaction and the treatment is doxycycline, 100 milligrams twice a day, similar to what’s used in acute Lyme disease and the treatment is until three days after the disappearance of the fever.
Related is something known as human monocytic ehrlichiosis. Ehrlichia and Anaplasma were used interchangeably in the past, but now they’ve been divided into separate categories because of the bacterial composition. Human granulocytic anaplasmosis is carried by the black legged deer tick, Ixodes scapularis, Ixodes pacificus on the west coast, but this vector for human monocytic ehrlichiosis is the Lone star tick, or Amblyomma americanum and Dermacentor variabilis, the American dog tick. The classic infection in the Midwest in particular is by Ehrlichia chaffeensis and Ehrlichia ewingii, more so chaffeensis. Usually peaking in July, usually affecting males older than 50 years old, and again, within a few weeks of the tick bite, the patient develops headaches, muscle aches, otherwise known as myalgias, fatigue, a drop in white blood count, a drop in platelet count, fever, gastrointestinal systems, which may lead to also respiratory insufficiency and kidney failure.
The three states most affected by Ehrlichia chaffeensis and ewingii are Oklahoma, Missouri, and Arkansas. They account for 30% of the reported cases of these bacterial species. The numbers have been reported in the low thousands over the last few years. In 2009, a third cause of human ehrlichiosis was identified in the upper Midwest. This has been known as Ehrlichia muris-like agent. Interestingly, it also exists in Eastern Europe and Asia. The detection of this pathogen or disease producing organism is by looking for the DNA, that is the genetic material, of this organism in the blood of patients. About 2.5% of Ixodes scapularis ticks are infected by this E. muris type agent. Note that this one is spread by Ixodes scapularis, the black legged deer tick, not the Lone Star tick as in human monocytic ehrlichiosis.
One of the better known bacterial infections that people read about, hear about, especially with people traveling into the Rocky Mountain area, into the Midwest, into the Southeast, is something known as Rocky Mountain Spotted Fever. This is Rickettsia rickettsia…it is spread by the American dog tick, by the Rocky Mountain wood tick, and by the brown dog tick. There are reported 14 cases per million population, peaking in April through September. Despite its name, as I said before, it’s not confined to the Rocky Mountains, it’s also found in the southeastern United States. These bacteria, after the tick bite, travel within the blood stream and lodge within endothelial cells, that’s the lining cells of small blood vessels, and elicit inflammatory changes and make the blood vessels leaky, affecting all organs infected, especially the skin and the adrenal glands. The platelets responsible for clotting are consumed and you may have kidney malfunctioning.
Patient will present with severe headaches, high fevers, a few days after the bite and a few days after that, a spotted rash on the wrists, palms, and ankles. Patient may also have abdominal pain, nausea, vomiting, and other generalized symptoms. The mortality rate can be as high as 4% and this is caused by a delay in diagnosis and treatment. The treatment is doxycycline and patients do best, and have a much lower morbidity and mortality if they’re treated within five days of being infected.
Below is the full podcast with Dr. Kotsoris and Dr. Hsu. They continue their overview of Lyme and co-infections, specifically Bartonella and the Powassan virus.

Follow Global Lyme Alliance on SoundCloud to hear future podcasts.

LymeSeq – New Lyme/MSIDS Test Explained

http://www.azpbs.org/arizonahorizon/play.php?vidId=10327

Arizona PBS

Airdate: March 21, 2017

Lyme Disease is spread by ticks and can be difficult to diagnose because symptoms mimic other illnesses. The group Focus on Lyme is funding research at the Translational Genomics Research Institute in Phoenix to increase the speed and accuracy of Lyme Disease diagnosis with a test called LymeSeq.

Tammy Crawford, the executive director of Focus on Lyme, explains the new test.

Listen to interview in link above.

Possible Transfusion-Transmitted Babesia divergens-like/MO-1 in Arkansas Patient

https://academic.oup.com/cid/article-abstract/doi/10.1093/cid/cix216/3067352/Possible-Transfusion-Transmitted-Babesia-divergens?redirectedFrom=fulltext  Mary J. Burgess, MD Eric R. Rosenbaum, MD, MPH Bobbi S. Pritt, MD, MSc Dirk T. Haselow, MD, PhD Katie M. Ferren, MD Bashar N. Alzghoul, MD Juan Carlos Rico, MD Lynne M. Sloan, BS Poornima Ramanan, MD Raghunandan Purushothaman, MD Robert W. Bradsher, MD    Published March 13, 2017

A patient with asplenia and multiple red blood cell transfusions acquired babesiosis infection with Babesia divergens-like/MO-1 and not Babesia microti, the common United States species. He had no known tick exposure. This is believed to be the first transfusion-transmitted case and the fifth documented case of Babesia divergens-like/MO-1.

Systematic Review: Human Diseases From Deer Ticks

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4857413/#!po=47.6331

Mark P. Nelder,corresponding author Curtis B. Russell, Nina Jain Sheehan, Beate Sander, Stephen Moore, Ye Li, Steven Johnson, Samir N. Patel, and Doug Sider

I condensed information from the above link.

Abstract

Background

The blacklegged tick Ixodes scapularis transmits Borrelia burgdorferi (sensu stricto) in eastern North America; however, the agent of Lyme disease is not the sole pathogen harbored by the blacklegged tick. The blacklegged tick is expanding its range into areas of southern Canada such as Ontario, an area where exposure to blacklegged tick bites and tick-borne pathogens is increasing. We performed a systematic review to evaluate the public health risks posed by expanding blacklegged tick populations and their associated pathogens.

Methods

Researchers searched Ovid MEDLINE, Embase, BIOSIS, Scopus and Environment Complete databases for the years 2000 through 2015 using specific eligibility criteria such as field-collected backlegged ticks and studies that did NOT focus solely on B. burgdorferi (Bb) and performed quality assessments on eligible studies.  

Results

Seventy-eight studies were chosen.  The ticks in the studies harbored 91 distinct taxa, 16 of which are tick-transmitted human pathogens including Anaplasma, Babesia, Bartonella, Borrelia, Ehrlichia, Rickettsia, Theileria and Flavivirus.

Conclusions

Our review is the first systematic assessment of the literature on the human pathogens associated with the blacklegged tick. As Lyme disease awareness continues to increase, it is an opportune time to document the full spectrum of human pathogens transmittable by blacklegged ticks.

If you go to the link at the top of page, Table One in the study has an informative table that shows the various states the studies were derived from as well as the human infections they found.  For Wisconsin the following were found:

*Arboviral infection (encephalitis, meningitis)

*Anaplasmosis

*Babesiosis

*Lyme Disease

*Ehrlichiosis

*Rocky Mountain Spotted Fever

**Bartonella is NOT reportable, which we need to do something about.  Frankly, it is as nasty if not nastier than borrelia, and just as hard to get rid of.  Also, other borrelia species are also NOT reportable.  

***Also, just because it wasn’t found in this systemic review doesn’t mean it doesn’t exist.  

 

TBI’s Increasing and Spreading

Tick Borne Infections (TBI’s) were tested in 9 national parks in this study.

As a patient and advocate, I wish researchers would carefully choose their wording when reporting results.  For instance the authors state:  “Ba. microti occurred at just 20% of the parks.   http://jme.oxfordjournals.org/content/early/2016/12/28/jme.tjw213.  That wording will bias people into thinking it isn’t significant, but 20% is nothing to sniff at, particularly when you are one of the 20%.  Also, that is what they discovered.  Someone else may discover something else and if time is any indicator, that number will probably rise.  I would also like to see Bartonella strains added to the pathogen list.  Interesting to note: there are 210 cases of locally acquired Zika in the Continental U.S., yet Congress is considering appropriating billions of dollars toward it.   https://www.cdc.gov/zika/intheus/maps-zika-us.htmlhttp://www.usatoday.com/story/news/2016/01/28/who-warns-zika-spread/79451430/http://www.usatoday.com/story/news/politics/2016/05/25/zika-funding-mired-congress/84914934/

Abstract

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.

In the eastern United States, the blacklegged tick, Ixodes scapularis Say, is the primary vector of Borrelia burgdorferi, the causative agent of Lyme disease, which is the most commonly reported vector-borne disease in the United States (Mead 2015). Ixodes scapularis also vectors other pathogens that can cause potentially serious disease, including Borrelia miyamotoi, Anaplasma phagocytophilum, and Babesia microti (Barbour and Fish 1993, Homer et al. 2000, Jin et al. 2012, Krause et al. 2015). Established blacklegged tick populations are nearly continuous across counties in the Northeastern and North-Central United States where the majority of I. scapularis-borne disease cases are reported (Mead 2015, Eisen et al. 2016). The risk of acquiring Lyme disease is influenced by spatio-temporal variation in the density of host-seeking infected nymphs (Diuk-Wasser et al. 2012). This metric often correlates with Lyme disease incidence, though to varying degrees (Mather et al. 1996, Stafford et al. 1998, Falco et al. 1999, Pepin et al. 2012). Human behavior, including time spent in tick-infested areas or engaged in behaviors that enhance or reduce the likelihood of encounters with ticks (Orloski et al. 2000, Connally et al. 2009), also influences the likelihood of acquiring Lyme disease and may explain some of the lack of concordance between measures of density of infected host-seeking nymphs and Lyme disease incidence (Pepin et al. 2012).

Understanding where people may come into contact with infected vector-competent ticks is central to mitigating tick-borne disease risk. For example, in the Mid-Atlantic and Northeastern United States, peridomestic exposure to I. scapularis likely occurs frequently (Falco and Fish 1988, Maupin et al. 1991, Klein et al. 1996, Connally et al. 2006, Feldman et al. 2015), whereas in the North-Central United States, recreational exposures are believed to be more common than peridomestic exposures (Kitron and Kazmierczak 1997, Paskewitz et al. 2001). Regardless of geographic region, previous studies have demonstrated a risk of human exposure to infected host-seeking I. scapularis nymphs in recreational settings (Falco and Fish 1989, Schulze et al. 1992, Oliver and Howard 1998, Paskewitz et al. 2001, Han et al. 2014, Prusinski et al. 2014, Ford et al. 2015). National parks are popular recreation destinations and may represent areas of elevated acarological risk, yet one cannot adequately infer the risk of tick-borne disease for park visitors or employees from the epidemiological surveillance conducted at the county spatial scale (Eisen et al. 2013). National parks often vary ecologically from surrounding areas, and thus the density of infected ticks may differ between settings; further, human behavior within the parks may differ from behavior in surrounding communities.

In this study, we sought to characterize the acarological risk, that is, the risk of human exposure to tick-borne pathogens, in national parks in the Eastern United States. We surveyed frequently used trails in national park units across six Northeastern and Mid-Atlantic States and the District of Columbia, ranging from Maine in the north to Virginia in the south. Our collection efforts focused on the nymphal stage of I. scapularis. This stage likely poses the greatest threat of transmission of B. burgdorferi and other pathogens to humans, as peak activity of questing nymphs occurs in late spring and early summer which coincides with peak onset of human disease (Piesman 1989, Fish 1993, Falco et al. 1999, Mead 2015). Here, we describe the diversity of ticks collected by drag sampling during summer months, density of host-seeking I. scapularis nymphs, and diversity and prevalence of B. burgdorferi, B. miyamotoi, A. phagocytophilum, and Ba. microti infection in I. scapularis nymphs.