Tag Archives: tick-borne diseases

  Finally some good news regarding ticks and the diseases they can transmit to humans. Currently ticks in the US are known to transmit at least 14 diseases, including Lyme disease. But a recent study done in the Netherlands found that the presence of predators such as foxes resulted in mice and voles having fewer ticks on them. A really big reduction in both tick numbers and the percentage of ticks infected with a disease. The researchers  thought that this was due to the mice and voles being less active when predators were nearby, and also that mice and voles that did venture further were preyed upon and eaten by the predators. So be happy if you see foxes in your neighborhood - they're beneficial. Excerpts from the NY Times:

Lyme Disease’s Worst Enemy? It Might Be Foxes

It is August, the month when a new generation of black-legged ticks that transmit Lyme disease and other viruses are hatching. On forest floors, suburban estates and urban parks, they are looking for their first blood meal. And very often, in the large swaths of North America and Europe where tick-borne disease is on the rise, they are feeding on the ubiquitous white-footed mice and other small mammals notorious for harboring pathogens that sicken humans.

But it doesn’t have to be that way. A new study suggests that the rise in tick-borne disease may be tied to a dearth of traditional mouse predators, whose presence might otherwise send mice scurrying into their burrows. If mice were scarcer, larval ticks, which are always born uninfected, might feed on other mammals and bird species that do not carry germs harmful to humans. Or they could simply fail to find that first meal. Ticks need three meals to reproduce; humans are at risk of contracting diseases only from ticks that have previously fed on infected hosts.

For the study, Tim R. Hofmeester, then a graduate student at Wageningen University in the Netherlands and the lead researcher of the study, placed cameras in 20 plots across the Dutch countryside to measure the activity of foxes and stone martens, key predators of mice. Some were in protected areas, others were in places where foxes are heavily hunted. Over two years, he also trapped hundreds of mice — and voles, another small mammal — in the same plots, counted how many ticks were on them, and tested the ticks for infection with Lyme and two other disease-causing bacteria. To capture additional ticks, he dragged a blanket across the ground.

In the plots where predator activity was higher, he found only 5 to 10 percent as many newly hatched ticks on the mice as in areas where predators were scarcer. Thus, there would be fewer ticks to pass along pathogens to the next generation of mice. In the study, the density of infected “nymphs,” as the adolescent ticks are called, was reduced to 6 percent of previous levels in areas where foxes were more active.“The predators appear to break the cycle of infection,’’ said Dr. Hofmeester, who earned his Ph.D. after the study.

Interestingly, the predator activity in Dr. Hofmeester’s plots did not decrease the density of the mouse population itself, as some ecologists had theorized it might. Instead, the lower rates of infected ticks, Dr. Hofmeester suggested in the paper, published in Proceedings of the Royal Society B, may be the result of small mammals curtailing their own movement when predators are around. [Original study.]

 Many of us who who spend time outdoors worry about ticks. Just about everyone in the Northeast knows someone who has struggled with Lyme disease or one of the other diseases spread by ticks. An earlier post from June 8, 2015 noted that the CDC says that there are 14 known tick-borne diseases in the United States, and possibly 15 (if recently discovered Bourbon virus is included). Lyme disease is the most common, but people can be infected with more than one tick-borne illness at a time. [POST on Some Ways  To Get Rid of Ticks]

But recently I've seen news reports about a rare and scary tick borne disease called Powassan virus which is spread by deer ticks. News stories reported that an infant that developed the disease was the first case ever in Connecticut, and that the tick had been attached less than 3 hours on the child.

What is Powassan virus and should I be concerned? The good news is that it is very rare, but the bad news is that it's very scary: the virus can be transmitted in less than 2 hours (even as little as 15 minutes!) from an attached tick, and is fatal in about 10% of cases. It can cause encephalitis. And among those who recover, there is about a 50 percent chance of permanent neurological damage.  On the other hand, the CDC also says: "Many people who become infected with POW virus do not develop any symptoms." - But note that we don't know how many people get it and don't get serious symptoms, or any symptoms at all.

Powassan virus (POWV) is a tick-borne flavivirus that was first discovered in Ontario, Canada in 1956. At this time we don't know how prevalent it is in the US. From 2006 to 2015, an average of 7 cases of POWV were reported each year in the United States - only 77 cases in total. Although the virus is mostly found in the Northeast and Great Lakes region of the United States, some states outside of this area have been reporting their first cases.  One recent study found that the Powassan virus was in 1 to 2% of the ticks studied in Long Island in NY and Connecticut.

The Centers for Disease Control (CDC) states that: "Signs and symptoms of infection can include fever, headache, vomiting, weakness, confusion, seizures, and memory loss. Long-term neurologic problems may occur. There is no specific treatment, but people with severe Powassan virus illnesses often need to be hospitalized to receive respiratory support, intravenous fluids, or medications to reduce swelling in the brain. One study of 14  Powassan virus cases in NY state (2004-20012) reported that all of the hospitalized patients who received corticosteroids during their illness survived (looks like something helps).

From CNN: Experts warn of increases in tick-borne Powassan virus

Summer is nearly here, and it's bringing fears of a rare tick-borne disease called Powassan. This potentially life-threatening virus is carried and transmitted by three types of ticks, including the deer tick that transmits Lyme disease. Over the past decade, 75 cases have been reported in the northeastern states and the Great Lakes region, according to the US Centers for Disease Control and Prevention. Though no one can say how many infections will occur this year, warmer winters have led to an increased tick population, so experts predict rising tick-borne infections of many types.

Everyone is at risk for Powassan: Newborns, 20-somethings, the middle-aged, the elderly and the immunocompromised. Anyone bitten by an infected tick can get it, said Dr. Jennifer Lyons, chief of the Division of Neurological Infections and Inflammatory Diseases at Brigham and Women's Hospital in Boston. Infections are most likely during late spring, early summer and mid-fall, when ticks are most active.

"About 15% of patients who are infected and have symptoms are not going survive," said Lyons, who is also an assistant professor of neurology at Harvard Medical School. "Of the survivors, at least 50% will have long-term neurological damage that is not going to resolve." Although most infected people will never show symptoms, those who do become sick usually do so a few days to about a week after the tick bite, she said. The most common symptoms will be fever and headache. "You basically feel nonspecific flu-like stuff," Lyons said, including "muscle aches and pains; maybe you have a little rash on your skin, but almost certainly, you'll have a fever and the headache."The unlucky few who develop a more serious illness will do so "very quickly over the next couple of days," she said. "You start to develop difficulties with maintaining your consciousness and your cognition. ....

Just as there are no vaccines to prevent infection, there are also no treatments for Powassan. There are some experimental therapies we try when somebody comes in and they get here early enough and we get the therapy started early enough, but we have no idea if any of that works," Lyons said. Standard treatment includes intravenous fluids, though antiviral medications, systemic corticosteroids and other drugs have been tried in some patients.

Scientists also believe Powassan is on the rise based on studies that have identified an increasing number of infections in deer. Similarly, Lyme is showing increasing numbers. ....To make the matter more complicated, we are seeing greater number of ticks infected with other tick-associated pathogens, including babesiosis and anaplasmosis," Molaei said. Both babesiosis and anaplasmosis usually don't have symptoms, just like Powassan, though both may cause severe or even life-threatening illnesses.

05 bug bites tick burrowed Engorged tick attached to human skin  Credit: CNN

Medical story about the Connecticut infant who developed Powassan virus. From Contagion Live: Connecticut Reports Its First Human Case of Powassan Virus

 Another microbe that causes Lyme disease! Lyme disease is the most common tick-borne disease in the northern hemisphere, and it is caused by the bacteria Borrelia burgdorferi. Recently Mayo Clinic researchers found a new bacteria, which they named Borrelia mayonii, in the fluids and tissues of some people diagnosed with Lyme disease in the upper midwestern USA. The symptoms are different from typical Lyme disease: with nausea and vomiting, diffuse rashes (rather than a single bull's-eye rash), and a higher concentration of bacteria in the blood. Same treatment as with the original bacteria , but it may not show up in tests for Lyme disease.

Other researchers say that other Borrelia species found throughout the US and Europe also cause Lyme disease. This may explain why Lyme diseasse sufferers are not always diagnosed with Lyme disease, even though they have it. From Scientific American:

New Cause for Lyme Disease Complicates Already Murky Diagnosis

Tick-borne Lyme disease in the U.S. has long been thought to be caused by a single microbe, a spiral-shaped bacterium called Borrelia burgdorferi. Last week this notion was challenged when a team led by scientists at the Mayo Clinic discovered that Lyme could be caused, albeit rarely, by a different bacterial species that may incite more serious symptoms ranging from vomiting to neurological issues. Scientists working in the contentious field of Lyme disagree, however, as to what this information means for public health and if these findings are truly the first of their kind. For years, they say, research has pointed to the notion that the spirochete that causes Lyme disease in the U.S. is more heterogeneous than many have acknowledged.

In the new study, recently published in The Lancet Infectious Diseases,Mayo Clinic pathologist and laboratory doctor Bobbi Pritt and her colleagues tested more than 100,500 clinical specimens, such as blood, cerebrospinal fluid and tissue, collected from U.S. patients with suspected Lyme disease between 2003 and 2014. Using a special molecular biology technique called PCR that can identify genetic differences among bacterial strains, they found that six of the samples—collected from patients between 2012 and 2014 in Wisconsin, Minnesota and North Dakota—contained DNA suggestive of a new species. They isolated some of these live bacteria and analyzed parts of their genetic sequence, confirming that the microbe has, in fact, never been documented before. The researchers propose to name the new species Borrelia mayonii

Whereas these findings have been touted as the first evidence that bacteria other than B. burgdorferi can cause Lyme in the U.S., “other Borrelia species have [in the past] been implicated,” says Richard Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies. For example, in 2011 researchers led by Yvette Girard, a medical entomologist at the University of California, Berkeley, found DNA close in sequence to a spirochete called Borrelia bissettii, which has been implicated in Lyme disease in Europe, in three California individuals. Kerry Clark, a tick-borne disease ecologist and epidemiologist at the University of North Florida, and his colleagues also found B. bissettii DNA in an individual from the U.S. Southeast, and they identified the DNA of two other Borrelia species in a handful of Florida and Georgia individuals with Lyme-like symptoms.

Lyme-causing bacteria are complex for another reason: Even within a single species of Borrelia, diversity flourishes. Contrary to what has long been believed, B. burgdorferi can genetically recombine to create different strains that behave dissimilarly inside the human body. Some strains seem more likely to remain in the skin whereas others are more likely to invade the nervous system or heart. Some strains are also more commonly found in certain parts of the country. “When I started out and we identified a tick as having Borrelia burgdorferi, we thought that was the gold standard—aha!—but now we are not thinking that way,” says Robert Lane, a medical entomologist at the University of California at Berkeley. “We have to go within the species itself and break it down further, according to strains or genotypes or alleles. As we learn more, it gets more complicated over time to disentangle the transmission cycles in nature and also what’s going on in the human body after exposure to a given spirochete.”

Could some of these differences explain why Lyme patients report diverse symptoms and treatment outcomes? Weigang Qiu, a biologist who studiesBorrelia genetics at Hunter College in New York City, says no one yet knows. “This is the most important question, but we haven’t found a definitive answer yet,” he says. B. mayonii, though, seems to cause strange and serious symptoms: Some patients experienced nausea and vomiting and had diffuse and spotty rashes that were drastically different from the typical Lyme bulls-eye rash. Half displayed neurological problems and one third were hospitalized.

All these scientific challenges could help explain why there are so many rifts within the Lyme research community. The organism is difficult to study and genetically diverse, and its ecology—the complicated and intricate dance that takes place between the ticks, their spirochetes and their numerous animal and human hosts—is immensely difficult to track and understand. “To me, the underlying biology that paves the way for controversy and vastly different perspectives is all a function of the amazing complexity and sophistication of Borrelia,” Ostfeld says. Adding to the problem, scientists bring to the field different backgrounds, methodologies, standards of evidence and preconceptions.
 
The new bacterium could complicate the diagnosis of Lyme, too, which has long been a contentious issue. Even with B. burgdorferi–caused Lyme, government-recommended diagnostic tests do not typically work in the first four weeks of infection; blood antibody levels are too low. (Three of the six patients who had B. mayonii in the Mayo Clinic study would have failed the standard Lyme tests based on their antibody results.)

Because of these difficulties, physicians diagnosing Lyme in its early stages are supposed to rely entirely on clinical cues such as the characteristic bulls-eye rash, fever, aches and fatigue. But what if a patient is vomiting and has a spotty rash? “People may not think of a tick-borne disease with that,” Aucott says, so cases of B. mayonii may go undiagnosed and untreated. (B. burgdorferi–caused Lyme disease, he adds, does not always cause a bulls-eye rash either.) Pritt and her colleagues recommend that physicians use their PCR (polymerase chain reaction) test to diagnose B. mayonii early on, as these bacteria, unlike B. burgdorferi, proliferate readily in blood. But Aucott points out that these tests require physicians to send samples to the Mayo Clinic, and “that just may not happen.”

A cluster of Borrelia burgdorferi bacteria, which Lyme disease. Humans catch it when bitten by ticks. These bacteria belong to a group called spirochetes, which resemble coiled springs.  A cluster of Borrelia burgdorferi bacteria, which causes Lyme disease.  Credit: CDC/ Claudia Molins photo: Janice Haney Carr

 Adult deer tick, Ixodes scapularisCredit:  Scott Bauer/USDA

 I recently posted on ways the number of  ticks can be reduced in a backyard. Now an article on vaccines being developed to battle tick borne diseases, especially Lyme disease. However, the bad news is that ticks now transmit 16 diseases in the US (including anaplasmosis, babesiosis, ehrlichiosis), while vaccines typically only focus on one disease at a time. Tick borne diseases are on the rise throughout the world. We all know about Lyme disease (which is also a problem in Europe, China, and Mongolia), but in parts of Africa, the Middle East, Asia and southern Europe, ticks can spread Crimean–Congo haemorrhagic fever, which is fatal 40% of the time! And while some researchers are focusing on human vaccines, some are focusing on vaccines for mice. Big problem: would we really be able to give the vaccine to enough mice to make a difference? I really like the idea of a vaccine that hampers the ability of ticks to feed on humans. From Nature:

The new war on Lyme and other tick-borne diseases

Williams is testing whether vaccinating mice against Borrelia burgdorferi, the bacterium that causes Lyme disease in the United States, can reduce the proportion of ticks that are infected. ....Borrelia burgdorferi infects an estimated 329,000 people in the United States each year, according to the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. And although most people who get prompt treatment recover quickly — Williams has had Lyme three times — up to one in five develops long-term and potentially life-threatening symptoms, including heart, vision or memory problems, or debilitating joint pain.

Williams's approach is one of several strategies being tested in an attempt to thwart the spread of tick-borne diseases. Some, like the mouse vaccine, interrupt the pathogen's ecological circuitry by targeting the wild animals that pass along and amplify the disease. Others, such as efforts to revive a human Lyme vaccine, aim to protect people from infection directly. A more radical approach could hamper the ability of ticks to bite humans or animals, potentially protecting against dozens of illnesses spreading across the United States, Europe, Africa and Asia.

That the field needs creative solutions is clear. Many long-recommended interventions, such as pesticide application or controlling populations of deer, which are an important host for adult ticks, have had mixed success in scientific studies. Even the time-honoured protective strategies that most people use are not evidence-based. “We tell people to wear repellents, to do tick checks and to shower if they've been in the field, but there's very little data to show that these things reduce human illness,” explains Ben Beard, chief of the CDC's bacterial-diseases branch in the division of vector-borne diseases.

The plan is unconventional, because most Lyme-control measures focus on white-tailed deer (Odocoileus virginianus), which have exploded in number in the United States over the past century as young forests have become increasingly fragmented by human development and large predators have been all but eradicated. Adult blacklegged ticks (Ixodes scapularis) typically feed and mate on deer, so many scientists have argued that the only way to get rid of Lyme is to get rid of the deer. But such efforts have had “an incredibly spotty record”, says Richard Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, New York, who has been studying tick-borne diseases for decades.

Ostfeld and others contend that mice are a major driver for both the tick problem and the disease problem. Mice, like deer, flourish in fragmented woodlands — in part because predators such as foxes and opossums get displaced. Ticks then thrive on the rodents, which are poor groomers. Studies suggest that larval ticks have a 50% chance of surviving when they feed on mice, but only a 3.5% chance on opossums2.

And mice are typically where ticks pick up B. burgdorferi. Most mice in Lyme-endemic areas get infected with the bacterium at a young age and, for reasons that are not completely clear, they are particularly good at transmitting it to other ticks. Almost all young ticks that feed on white-footed mice become infected, compared with a mere 1% of ticks that feed on deer. Interrupting the tick–mouse infection cycle, says Ostfeld, could make ticks a lot less dangerous.... The bait-based vaccine is also attractive because it is less ecologically destructive than other strategies — it does not kill animals or even ticks, just the pathogens.

Other scientists argue for more a direct means of protecting people against Lyme, ideally with a human vaccine. ....product called LYMErix, manufactured by UK-based pharmaceutical company SmithKline Beecham (now GlaxoSmithKline), was approved by the US Food and Drug Administration in 1998. It reduced the risk of Lyme caused by US strains of Borrelia by 76% in clinical trials4. But it faced problems from the start....The company voluntarily shelved LYMErix in 2002. Plotkin maintains that this was a mistake. “The vaccine was safe,” he says.

Now, a new and potentially improved vaccine has completed safety trials5. Developed by researchers at Stony Brook University and Brookhaven National Laboratory in New York, and licensed to Baxter Innovations in Vienna... it protects against many Borrelia species known to cause Lyme in humans, including those that affect people in Europe....Richard Marconi, a microbiologist and vaccinologist at Virginia Commonwealth University in Richmond, says that he and his colleagues are working on an even better vaccine.

Mouse vaccines would not raise such concerns, but some researchers, including Plotkin, are sceptical about whether they could dose enough mice to reduce Lyme rates. And both vaccine approaches are limited because they combat only one tick-borne disease, when more than a dozen others are spreading throughout the world (see 'Reality bites').

There is one strategy that could conquer them all, and it involves turning one of the tick's most ingenious tools — its saliva — against it. When a tick bites a host, molecules in its saliva help it to evade detection and start to feed by blocking pain, inflammation and immune signals. If a vaccine could raise an immune response to key salivary proteins, it could make tick bites more noticeable or block the tick's ability to feed. Ostfeld himself is a proof-of-concept for this approach. He has been bitten more than 100 times, and his body now reacts to tick saliva. “I realize when a tick is biting me because I get a burning sensation. It's pretty intense,” he explains. 

A European Commission-funded consortium called ANTIDotE (Anti-tick Vaccines to Prevent Tick-borne Diseases in Europe) is characterizing the tick salivary proteins that could be targeted to thwart feeding. “We think that an anti-tick vaccine could be immensely useful in protecting both humans and animals,” says Hein Sprong, an ANTIDotE leader at the National Institute for Public Health and the Environment in Bilthoven, the Netherlands. US Biologic also plans to develop a bait-based vaccine for mice that could thwart tick feeding, thereby protecting against multiple diseases. That could reduce overall tick numbers, too, because it would make it difficult for larval ticks to get the meals that they need to survive into adulthood and reproduce.

But these approaches are hardly around the corner. Part of the problem, scientists say, is that funding is scarce. The stereotype of Lyme and other US tick-borne diseases as primarily 'yuppie' illnesses does not help;... Until an all-encompassing solution becomes available, controlling tick-borne diseases will probably require an array of smaller-scale approaches that attack the problem, bit by bit, on a number of levels. 

 Deer can harbor many engorged ticks behind their ears; the ticks drop off in areas where the deer pass through or rest. Credit: Peter Priolo

The good news is that not every tick is infected, but the bad news is that the CDC says that there are 14 known tick-borne diseases in the United States, and possibly 15 (if newly discovered Bourbon virus is included). Lyme disease is the most common, but people can be infected with more than one tick-borne illness simultaneously.  Three new diseases to watch for: Borrelia miyamotoi (bacteria carried by deer ticks), Heartland virus (carried by Lone Star Tick), and Bourbon virus. From Medical Xpress;

Beyond Lyme, new illnesses, more reason to watch for ticks

Lyme disease makes the headlines but there are plenty of additional reasons to avoid tick bites. New research highlights the latest in a growing list of tick-borne threats—a distant relative of Lyme that's easy to confuse with other illnesses.Monday's study suggests a kind of bacteria with an unwieldy name—Borrelia miyamotoi—should be on the radar when people in Lyme-endemic areas get otherwise unexplained summertime fevers. It's one of several recently discovered diseases linked to ticks in different parts of the country, a reminder to get tick-savvy no matter where you live.

The first U.S. case was reported in 2013 in New Jersey, an 80-year-old cancer survivor who over four months became increasingly confused, had difficulty walking and lost 30 pounds. Doctors found spiral-shaped bacteria in her spinal fluid that looked like Lyme but caused a relapsing fever more closely related to some other tick-borne illnesses. While treatable by antibiotics—the woman recovered—doctors know little about B. miyamotoi.

Researchers with Imugen Inc., a Massachusetts testing lab, tested blood samples from patients in Massachusetts, Rhode Island, New Jersey and New York whose doctors suspected tick-borne illnesses and used that lab. During the 2013 and 2014 tick seasons the lab found 97 cases of the new infection. That's roughly 1 percent of samples tested and close to the lab's detection of a better-known tick disease named anaplasmosis. ...Researchers then analyzed medical records from 51 of those patients, and found symptoms typically include a high fever, severe headache, chills and blood abnormalities—decreases in infection-fighting and blood-clotting cells

The bacterium is carried by deer ticks, also known as blacklegged ticks, which also can spread Lyme and two other illnesses, babesiosis and anaplasmosis.

Two new tick-borne viruses were recently discovered in the Midwest, and neither has a specific treatment.The Centers for Disease Control and Prevention has confirmed nine cases of Heartland virus, and one death, with other reports under investigation, said CDC entomologist Roger Nasci. Symptoms include fever, fatigue, headaches, muscle aches, diarrhea and low blood counts. Identified in Missouri, the virus also was reported in Tennessee and Oklahoma, although the Lone Star tick that spreads it lives around the East and Southeast.

Then there's the Bourbon virus, with similar symptoms, discovered last year after the death of a Kansas man and named for his home county. Another patient, in Oklahoma, recovered. The Kansas man had found an embedded tick days before getting sick, and CDC researchers are searching for the culprit species.

The CDC counts 14 illnesses linked to specific U.S. tick species, not including the Bourbon virus still being studied. Lyme is the most common, with about 30,000 cases reported each year, although CDC has estimated that the true number could be 10 times higher. It's too early to know how widespread the newly discovered illnesses are. But people can be infected with more than one tick-borne illness simultaneously, complicating care.

Adult deer tick.jpg Deer tick.            Amblyomma americanum tick.jpgLone Star Tick,  From Wikipedia.