NSF: TICKS AND LYME DISEASE

FROM:  NATIONAL SCIENCE FOUNDATION 

Lyme Disease: Ten things you always wanted to know about ticks...

...but maybe were afraid to ask...

May is Lyme Disease Awareness Month.

To find out how to steer clear of Lyme disease during "picnic season" - a time when people are more likely to pick up ticks - the National Science Foundation spoke with NSF-funded disease ecologist Rick Ostfeld of the Cary Institute of Ecosystem Studies in Millbrook, N.Y., and program director Sam Scheiner of NSF's Division of Environmental Biology.

Ostfeld's research is funded by the joint NSF-NIH Ecology and Evolution of Infectious Diseases Program and NSF's Long-Term Research in Environmental Biology Program.

1) What have we learned about how Lyme disease is transmitted?

Lyme disease can develop when someone is bitten by a blacklegged tick infected with a virulent strain of the bacterium Borrelia burgdorferi. At least 15 strains of the bacterium are found in ticks, but only a few turn up in Lyme disease patients, says Ostfeld.

Newly hatched larval ticks are born without the Lyme bacterium. They may acquire it, however, if they feast on a blood meal from an infected host. Scientists have learned that white-footed mice, eastern chipmunks and short-tailed shrews can transfer the Lyme bacterium to larval ticks.

Tick nymphs infected with Lyme bacteria pose the biggest threat to humans; their numbers are linked with the size of mouse populations.

2) The list of illnesses spread by blacklegged ticks seems to increase each year. What's going on?

People in the Northeast, Mid-Atlantic, and Midwest have experienced waves of "new" tick-borne diseases. It started in the 1980s with Lyme disease. Then in the 1990s it was anaplasmosis, followed in the early 2000s by babesiosis. Now we may be seeing the emergence of Borrelia miyamotoi, says Ostfeld.

The pathogens are transmitted by blacklegged ticks. "We suspect that they were present for decades in isolated geographic areas, but we're working to understand what's triggering their spread," says Ostfeld. For example, while Lyme disease bacteria can be carried long distances by birds, Anaplasma and Babesia don't fare well in birds.

3) How do small mammals play a part?

Mice, chipmunks and shrews play a major role in infecting blacklegged ticks with the pathogens that cause Lyme disease, anaplasmosis, and babesiosis. Ticks feeding on these animals can acquire two or even all three pathogens from a single bloodmeal, says Ostfeld.

Health care providers need to be aware, he says, "that patients with Lyme disease may be co-infected with anaplasmosis and babesiosis, which will affect symptoms, treatments, and possibly outcomes. The good news is that by regulating these small mammals, we can reduce our risk of exposure to all three illnesses."

4) How are predators like foxes protecting us against diseases such as Lyme?

Some predators appear to be protecting our health by regulating small mammals, Ostfeld says. Research suggests that where red foxes are abundant, there is a lower incidence of Lyme disease in the human population.

"We're investigating whether foxes and other predators reduce our risk by preying on the small mammals responsible for transmitting Lyme disease to ticks," says Ostfeld. "We don't yet know whether predators like owls and hawks behave similarly."

5) How is climate change influencing the spread of tick-borne illnesses?

The northward and westward spread of blacklegged ticks and Lyme disease in recent decades is caused in part by climate warming, says Ostfeld. However, Lyme disease has also been spreading south, which is unlikely to be caused by climate change, scientists believe.

Models predict that Lyme disease will continue to move to higher latitudes and elevations over coming decades, a result of milder winters and longer growing seasons. "We're currently exploring how climate warming affects the seasonal timing of host-seeking and biting behavior of ticks," says Ostfeld.

6) Why are we more likely to contract Lyme disease in fragmented forests?

"When humans fragment forests, often through urbanization, we create conditions that favor the small mammals that amplify Lyme disease," Ostfeld says.

The species consistently found in forest sites, no matter how small or isolated, is the white-footed mouse. And lyme-infected ticks are often most abundant in the smallest forest patches, leading to a high risk of human exposure.

"To combat Lyme disease, one of the fastest growing threats to human health in the U.S., we need to know where it is, how it's transmitted, and how it can be controlled," says Scheiner.

"Long-term studies, such as work by Ostfeld and colleagues, show that the abundance of the disease-causing bacteria is determined by the number and variety of small mammals in a community. The research also demonstrates the value of conserving biodiversity as a way of limiting the spread of disease."

7) Aren't mice affected by ticks?

Long-term monitoring of mice and ticks in upstate New York shows that mice survive just as well when they're infested with hundreds of ticks as when they have few or no ticks. In fact, male mice survive longer when they have more ticks, Ostfeld says.

"This is bad news, as it means that heavy tick loads won't bring down mouse numbers, which would have helped reduce the human risk of tick-borne diseases."

8) Why are ecological studies essential to understanding emerging infectious diseases?

Tick-borne disease takes a huge toll on public health and on the economy, says Ostfeld. "Take the case of Lyme disease, where diagnosis and treatment remain controversial. One thing that everyone can agree on is the importance of preventing exposure. Doing this requires understanding the ecology of ticks, pathogens and hosts."

The more we know about where and when the risk is high, he says, the better we'll be able to protect ourselves and respond appropriately when we're exposed.

9) What precautions might be wise for people wishing to spend time outside?

"I'd recommend the use of tick repellents on skin or clothes, paying special attention to shoes and socks," Ostfeld says. "Tick nymphs seek hosts on or just above the ground, so shoes and socks are the first line of defense." Some studies show that daily tick checks during late spring and early summer can be protective.

Knowing the early symptoms of Lyme disease - fever, chills, muscle aches, often a large rash - is important. "People who live in the heaviest Lyme disease zones of the Northeast, Mid-Atlantic, and Upper Midwest," says Ostfeld, "and who start feeling flu-like symptoms, especially from May through July, should ask their doctors to consider Lyme disease."

10) Does this mean that we should stay inside so we don't risk becoming infected?

The likelihood of contracting Lyme disease is very low overall, says Scheiner, "and is even lower if you take reasonable precautions. Don't let the threat of Lyme disease keep you from enjoying the best part of spring and summer: the great outdoors."

-- Cheryl Dybas, NSF

CDC REPORT ON SUDDEN CARDIAC DEATHS ASSOCIATED WITH LYME CARDITIS

FROM:  CENTERS FOR DISEASE CONTROL AND PREVENTION 

Three Sudden Cardiac Deaths Associated with Lyme Carditis — United States, November 2012–July 2013

Lyme carditis is a known but rare cause of sudden cardiac death. Lyme carditis can cause heart palpitations, chest pain, light-headedness, fainting, and shortness of breath in addition to the commonly recognized Lyme disease symptoms of fever, rash, and body aches. If you live in an area where Lyme disease is common and have these symptoms, see a healthcare provider immediately. Between November 2012 and July 2013, three young adults who lived in high-incidence Lyme disease regions suffered from sudden cardiac death associated with undiagnosed Lyme carditis. Lyme carditis is a known, but rare cause of death in persons who have Lyme disease. The CDC and state and local health departments investigated these three deaths. Two of the three individuals who died had corneas transplanted to three separate recipients before the cause of death was notified, but there was no evidence of disease transmission. Prompt recognition and early, appropriate therapy for Lyme disease with antibiotics is essential. These deaths underscore the urgent need for better methods of primary prevention of Lyme disease and other tickborne infections.

CDC ESTIMATES NUMBER OF AMERICANS WITH LME DISEASE

FROM:  CENTERS FOR DISEASE CONTROL AND PREVENTION

CDC provides estimate of Americans diagnosed with Lyme disease each year
Preliminary estimates released by the Centers for Disease Control and Prevention indicate that the number of Americans diagnosed with Lyme disease each year is around 300,000. The preliminary estimates were presented Sunday night in Boston at the 2013 International Conference on Lyme Borreliosis and Other Tick-Borne Diseases.External Web Site Icon

This early estimate is based on findings from three ongoing CDC studies that use different methods, but all aim to define the approximate number of people diagnosed with Lyme disease each year. The first project analyzes medical claims information for approximately 22 million insured people annually for six years, the second project is based on a survey of clinical laboratories and the third project analyzes self-reported Lyme disease cases from a survey of the general public.
Each year, more than 30,000 cases of Lyme disease are reported to CDC, making it the most commonly reported tick-borne illness in the United States. The new estimate suggests that the total number of people diagnosed with Lyme disease is roughly 10 times higher than the yearly reported number.  This new estimate supports studies published in the 1990s indicating that the true number of cases is between 3- and 12-fold higher than the number of reported cases.

“We know that routine surveillance only gives us part of the picture, and that the true number of illnesses is much greater,” said Paul Mead, M.D., M.P.H, chief of epidemiology and surveillance for CDC’s Lyme disease program. “This new preliminary estimate confirms that Lyme disease is a tremendous public health problem in the United States, and clearly highlights the urgent need for prevention.”

CDC continues to analyze the data in the three studies to refine the estimates and better understand the overall burden of Lyme disease in the United States and will publish finalized estimates when the studies are complete. Efforts are also underway at CDC and by other researchers to identify novel methods to kill ticks and prevent illness in people.

“We know people can prevent tick bites through steps like using repellents and tick checks. Although these measures are effective, they aren’t fail-proof and people don’t always use them,” said Lyle R. Petersen, M.D., M.P.H, director of CDC’s Division of Vector-Borne Diseases. “We need to move to a broader approach to tick reduction, involving entire communities, to combat this public health problem.”

This community approach would involve homeowners trying to kill ticks in their own yards, and communities addressing a variety of issues. These issues include rodents that carry the Lyme disease bacteria, deer that play a key role in the ticks’ lifecycle, suburban planning, and the interaction between deer, rodents, ticks, and humans. All must be addressed to effectively fight Lyme disease.

Most Lyme disease cases reported to CDC through national surveillance are concentrated heavily in the Northeast and upper Midwest, with 96 percent of cases in 13 states. Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks. Typical symptoms include fever, headache, fatigue, and a characteristic skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system.

CDC recommends people take steps to help prevent Lyme disease and other tickborne diseases:
Wear repellent
Check for ticks daily
Shower soon after being outdoors
Call your doctor if you get a fever or rash

ANIMAL-TO-HUMAN INFECTIOUS DISEASE AT ANNUAL CONFERENCE

FROM:  CDC.  This is a male Ixodes ricinus tick (smaller) shown copulating with a female tick (larger). I. ricinus, the "castor bean" tick, so called because of its resemblance to the castor bean, is a vector for the B. burgdorferi spirochete, the cause of Lyme disease, and is commonly found on farm animals, and deer who are the natural host. Credit: Centers For Disease Control and Prevention/Wikimedia

FROM: THE NATONAL SCIENCE FOUNDATION

Interplay of Ecology, Infectious Disease, Wildlife and Human Health Featured at Annual Conference
West Nile virus, Lyme disease and hantavirus. All are infectious diseases spreading in animals and in people. Is human interaction with the environment somehow responsible for the increase in these diseases?

The ecology and evolution of infectious diseases will be highlighted at two symposia at the Ecological Society of America's annual meeting, held from Aug. 5-9 in Minneapolis, Minn.

One symposium will address human influences on viral and bacterial diseases through alteration of landscapes and ecological processes.

Another will focus on the emerging field of eco-epidemiology, which seeks to integrate biomedical and ecological research approaches to addressing human health threats.

Much of the research presented is funded by the joint National Science Foundation- (NSF) National Institutes of Health Ecology and Evolution of Infectious Diseases (EEID) Program.

"These sessions show that basic research is critical for managing disease threats," said Sam Scheiner, NSF EEID program director. "They also showcase the need to link scientists with public health professionals."

The first symposium, on Monday, Aug. 5, will take a deeper look at the connections between human activities and infectious diseases.

Though we often think of diseases as simply being "out there" in the environment, human actions--such as feeding birds--can influence the abundance, diversity and distribution of wildlife species and thus, infectious diseases.

"New human settlements, the spread of agriculture and the increasing proximity of people, their pets and livestock to wild animals increase the probability of disease outbreaks," said session organizer Courtney Coon of the University of South Florida.

"We're interested in learning more about how urban and other environments that humans dramatically change affect the susceptibility and transmission potential of animals that are hosts or vectors of disease."

What are the key determinants of spillover of wildlife diseases to domestic animals and humans?

Why is the prevalence of pathogens in wildlife in urban areas often altered by counterparts in less developed environments?

Speakers will address these and other questions.

The second symposium, on Tuesday, Aug. 6, will continue the theme of infectious diseases, but with an eye toward integrating biomedical and ecological approaches into the investigation and control of emerging diseases.

"Environmental processes and human health are linked, and we'd like to chart a future in which ecologists and epidemiologists more routinely work in tandem to address health problems," said symposium organizer Jory Brinkerhoff of the University of Richmond.

Scientists studying human diseases may overlook possible ecological factors.

For example, most Lyme disease cases in the eastern United States happen in the North even though the black-legged tick, which transmits the bacterium, is found throughout the Eastern states.

Human life histories and interactions with the environment, researchers say, are critically important to the success of managing a mosquito-borne virus called dengue fever.

"Disease ecologists and epidemiologists address some of the same kinds of questions, yet operate largely in isolation of one another," said Brinkerhoff.

"We're bringing them together to share their approaches and study designs, and to strengthen our ability to address public health issues."

Disease Ecology in Human-Altered Landscapes: Monday, Aug. 5, 2013, 1:30 p.m.-5 p.m., 205AB, Minneapolis Convention Center.
Organizer/Moderator: Courtney Coon, University of South Florida
Co-Organizer: James Adelman, Virginia Tech

Speakers:
Parviez Hosseini, EcoHealth Alliance
Matthew Ferrari, Penn State University
Marm Kilpatrick, University of California, Santa Cruz
Raina Plowright, Penn State University
Sonia Altizer, University of Georgia
Becki Lawson, Zoological Society of London
Eco-Epidemiology: A Multi-Disciplinary Approach to Addressing Public Health Problems: Tuesday, Aug. 6, 2013, 1:30 p.m.-5 p.m., 205AB Minneapolis Convention Center.
Organizer/Moderator: Jory Brinkerhoff, University of Richmond
Co-Organizer: Maria Diuk-Wasser, Yale School of Public Health

Speakers:
Maria Diuk-Wasser, Yale School of Public Health
Daniel Salkeld, Colorado State University
Mark Wilson, University of Michigan
James Holland Jones, Stanford University
Harish Padmanabha, National Center for Socio-Environmental Synthesis
Jean Tsao, Michigan State University
-NSF-

MILD WINTERS BRING ON RISE IN TICK-BORNE DISEASES

Photo:  Ticks.  Credit:  National Science foundation 

FROM: NATIONAL SCIENCE FOUNDATION
Precautions for Tick-Borne Disease Extend "Beyond Lyme"

September 7, 2012
This year's mild winter and early spring were a bonanza for tick populations in the eastern United States. Reports of tick-borne disease rose fast.

While Lyme disease is the most common tick-borne disease in the Northeast and Upper Midwest, new research results emphasize that it is not the greatest cause for concern in most Southeastern states.

The findings are published today in a paper in the journal Zoonoses and Public Health.

The majority of human-biting ticks in the North--members of the blacklegged tick species--cause Lyme disease, but these same ticks do not commonly bite humans south of mid-Virginia.

Biologist Graham Hickling of the University of Tennessee, co-author of the paper, says many patients in Southeastern states, who become sick from a tick-bite, assume they have Lyme disease, but the odds of that being the case are low.

"Ticks in the eastern U.S. collectively carry more than a dozen agents that can cause human disease," says Hickling.

"Here in Tennessee we regularly collect lone star ticks that test positive for Ehrlichia, [a tick-borne bacterial infection]. Lone stars are an aggressive species that account for most of the human bites that we see in this region. So ehrlichiosis has to be a big concern, yet most people have never heard of it."

In contrast, says Hickling, there have been no confirmed reports to date of the Lyme disease pathogen among the sparse populations of blacklegged ticks found in Tennessee.

"The Southeast is dominated by different tick species than the ones that attack humans in the North," says Ellen Stromdahl, an entomologist at the U.S. Army Public Health Command and lead author of the paper.

"The lone star tick is by far the most abundant tick in the Southeast, and which species of tick bites you is critical because different ticks carry different diseases. In the Southeast you are unlikely to be bitten by the blacklegged ticks that spread Lyme disease," Stromdahl says.

Most bites in the Southeast are from the tick species that spread spotted fever rickettsiosis and ehrlichiosis, but not Lyme disease.

A complicating factor for public health officials is that tick species are on the move, as wildlife populations, forest habitats and weather patterns change across the continent.

This spring the Tennessee Department of Health, for example, reported a 500 percent increase in tick-borne rickettsiosis.

"Identifying health risks in the face of changing climates will be critical in coming years," says Sam Scheiner, National Science Foundation program director for the joint NSF-National Institutes of Health Ecology and Evolution of Infectious Diseases (EEID) program, which funds Hickling's research.

At NSF, the EEID program is co-funded by the Directorates for Biological Sciences and Geosciences.

"This study will inform public health officials about what diseases are found in which areas," says Scheiner, "so they can minimize human health problems."

Hickling's work is also in collaboration with scientist Jean Tsao of Michigan State University and is part of an EEID project to identify the ecological factors leading to distributions of tick species and pathogens--in particular, where the Lyme disease tick and pathogen are found.

Lyme-infected blacklegged ticks are expanding south through Virginia, and lone star ticks are moving north, the scientists have found.

The bite of the lone star tick can create a bulls-eye rash that appears like that of Lyme disease, but the rash isn't caused by the Lyme bacteria.

The scientists say that this almost certainly leads to misdiagnosis of some patients in mid-Atlantic states, where both tick species are common.

The best way to distinguish Lyme from other tick-borne diseases is to be vigilant for tick bites, and whenever possible save any tick that manages to bite you, the biologists recommend. Store the tick in your freezer or in a vial of alcohol so it can be identified if you become ill.

In the Northeast, Lyme disease awareness campaigns have focused public attention on the nymphal blacklegged tick--which is responsible for most disease transmission and which is tinier than the adult form.

While nymphal blacklegged ticks and nymphal lone star ticks--which also bite humans--can be distinguished, the two are often confused by the public.

In one study, 13 of 20 patients reporting tick bites to physicians were given antibiotics on the assumption that they were at risk for Lyme disease, yet 53 of the 54 ticks removed from those same patients were lone star ticks, which do not spread Lyme disease.

"Where you live determines which tick species is likely to bite you," says Tsao, "and therefore which diseases you're most likely to contract."

The biologists say they are happy that recent treatment recommendations have begun to emphasize the importance of considering the tick species and its infection status as part of the diagnostic process.

Their advice: Stay open-minded about which tick-borne diseases are most common in your area--and save the tick that bites you.