Student guest post: A taste of Lyme

Student guest post by Kyle Malter

In many areas of the country there is a vile blood sucker that lurks in our forests, our parks and even our backyards.  What concerns us is not what this creature takes but rather what it leaves in our body after it bites us:  corkscrew shaped bacteria called spirochetes and with the name Borrelia burgdorferi.  When the bacteria invade our bodies and cause problems along the way we call it Lyme disease.

It is Lyme, not “Lymes” disease, and here’s how it got that name. In the early 1970’s a large number of cases emerged involving children with a “bulls-eye” rash followed by arthritis and they were concentrated in a small area in and near Lyme, Connecticut.  Initially, the cause of the disease was unknown.  A clue to the mystery was that most of the kids lived near a wooded area.  After more investigation, ticks that feed on deer were identified as likely suspects.  The medical community learned that the “deer tick” transmitted the spirochete bacteria which was likely infecting the children and causing symptoms.  A researcher named Willy Burgdorfer helped identify the organism and in honor of his contribution the bacterium was named Borrelia burgdorferi. [1]  Wouldn’t it be fun to have a nasty bacteria named after you?

Signs of Lyme disease can vary from a mild rash to serious pain and disability. If infected, a “bull’s-eye” rash occurs in most people because of the inflammation left in the trail of the migrating bacteria. They move from the bite site away leaving the classic target appearance.  When this bug spirals though your joints, organs and tissues it can cause damage and a wide range of symptoms including fever, headache, lethargy, stiffness and general soreness.   In some cases, more serious and long-term problems with swollen joints, arthritis, Bell’s palsy, and even heart disease can result.   The symptoms can come and go and may last a lifetime.  [1] This is one serious problem if you have the disease-spreading tick in your environment.  Most people refer to the species as the “deer tick” or the “black-legged tick” although the proper name is Ixodes. Don’t forget about your dogs either.  They are also commonly infected in endemic states, can get permanent arthritis, and can rarely even die from the disease. [2]

Lyme disease has been diagnosed in all 50 states but is heavily concentrated in the northeast and upper Mid-West. [3] Approximately 96% of cases come from only 13 states. [4] CDC data by state, maps and disease forecast models show a clearly increasing trend.  Why such a steep increase in the number of cases?  There are probably many reasons.  First, surveillance is probably higher now than it was 15 years ago.  We simply weren’t looking for it as much then.  Another contributor is the increased population of the white-footed mouse in some regions. [5] This rodent is a reservoir for the bacteria meaning they harbor the bug until the tick larva come for a meal.  They are like a bank filled with Borrelia ready for every tick to make a withdrawal.  Once the tick has the bug in its gut, it is a loaded gun.

The recent increase in the white-footed mouse population may be the result of a cascade of events. “Change one thing. Change everything.”[6] Ohio reported two recent “banner years” for acorn production with a 36% increase in white oak acorns between 2011 and 2012.[7] A more abundant supply of “mouse food” in the way of acorns could result in more mice because they replicate much more efficiently.  More white-footed mice means more banks filled with Borrelia.  Ticks have a much better chance of making a withdrawal with every meal.  More ticks with Borrelia means more animals and humans infected.   So that’s how more acorns could mean more Lyme disease.

If you are unsure if Lyme bacteria are in your area just ask your dog.  Some studies suggest that dogs that live in your area may be able to predict your risk level. [8] [9] [10]  For those in the northeast and upper Mid-West you don’t have to ask.  It is ubiquitous in these parts of the country. Veterinarians in many non-endemic states are now screening dogs yearly to see if they have ever been infected with Borrelia.   If some dogs in your region are positive you should be more vigilant.  The CDC will keep track as well so check their Lyme page annually.

Preventing Lyme disease can be a very big challenge.  For dogs, very effective vaccines are available to protect them. [11] [12] So if this is such a potentially devastating disease in people why don’t we have a vaccine for humans?  Well, we did.  In the late 1990’s a vaccine was approved by the FDA to aid in the prevention of Lyme disease in humans.  While the safety and efficacy during the approval studies were good, there were skeptics and strong opponents in the public and medical community.  Some people claimed that the vaccine caused Lyme disease rather than prevent it.  Ultimately, the vaccine manufacturer withdrew it from the market citing poor demand. [12] Allen Steere, the man who discovered Lyme disease, also led one of the SmithKline Beecham (SKB) Lyme vaccine trials.  He said, “the withdrawal of the SKB vaccine . . . represents the most painful event in our Lyme disease history . . . the vaccine was really withdrawn because of fear and lawsuits, not because of scientific findings” [13]  Some advocates are attempting to rekindle efforts to make a vaccine for Lyme disease available again while others are opposed to the idea.

Tick prevention is our best strategy to prevent Lyme disease. Without a tick bite you cannot get Lyme disease.  In fact, even if an Ixodes tick bites you, it takes at least 24-48 hours of attachment to transmit the bacteria into your body. The National Institutes of Health suggest that you follow their fashion advice and tuck in your shirt into your light colored pants, tuck your pants into your socks and then put tape around the bottom. [1] I’ve never seen this method utilized in a public place but I’m sure you will end up on the “People of Wal-Mart” site if you try it.  The CDC recommends pyrethrins on your clothing and DEET on your skin and clothing to repel ticks. [4] The EPA also has a nice online tool.  Check yourself everyday for ticks during peak months.  Deer ticks are tiny so take some time and inspect your nooks and crannies.  The nymph stage, the second smallest tick in this picture,  is the one that usually infects people.  Again, don’t forget about your dog. While he can’t give you Lyme disease, he is also susceptible to it. Ask your veterinarian which flea and tick preventative is right for your pets.

Kyle picture

Lyme disease is no longer just a Lyme, Connecticut problem.  If it is not yet in your backyard, it could be soon. Lyme disease can have lifelong, debilitating consequences. Arm yourself with information and your body with tick protection.  We are not defenseless.  Protect yourself.   Protect your dog.  Please.

References:

[1] NIH Website http://www.niaid.nih.gov/topics/lymedisease/understanding/pages/intro.aspx

[2] Littman MP. Lyme nephritis. J Vet Emerg Crit Care (San Antonio). 2013 Mar-Apr;23(2):163-73

[3] Smith BG, Cruz AI Jr, Milewski MD, Shapiro ED. Lyme disease and the orthopaedic implications of lyme arthritis. J Am Acad Orthop Surg. 2011 Feb;19(2):91-100

[4] Centers for Disease Control and Prevention www.CDC.gov

[5] National Science Foundation http://www.nsf.gov/news/special_reports/ecoinf/lyme.jsp

[6] Townsend, Tracy A., “Change One Thing, Change Everything: Understanding the Rhetorical Triangle” (2013). Rhetoric Unit. Paper 3.

[7] Ohio DNR http://www.ohiodnr.com/home_page/NewsReleases/tabid/18276/EntryId/3033/Acorn-Mast-Survey-Results-Show-Increases-for-White-Red-Oaks.aspx

[8] J M Lindenmayer, D Marshall, and A B Onderdonk.  Dogs as sentinels for Lyme disease in Massachusetts. American Journal of Public Health November 1991: Vol. 81, No. 11, pp. 1448-1455.

[9] Olson, Canines as Sentinels for Lyme Disease in San Diego County, California, Journal of Veterinary Diagnostic Investigation March 2000 vol. 12 no. 2 126-129

[10] Faith D. Smith, Rachel Ballantyne, Eric R. Morgan, Richard Wall Estimating Lyme disease risk using pet dogs as sentinels Comparative Immunology, Microbiology and Infectious Diseases, Volume 35, Issue 2, March 2012, Pages 163–167

[11] Levy et al. Use of a C6 ELISA test to evaluate the efficacy of a wholecell bacterin for the prevention of naturally transmitted canine Borrelia burgdorferi infection. Vet Ther. 2002 Winter;3(4):420-4

[12] Aronowitz RA. The rise and fall of the lyme disease vaccines: a cautionary tale for risk interventions in American medicine and public health. Milbank Q. 2012 Jun;90(2):250-77.

[13] Steere, A.C. 2006. Lyme Borreliosis in 2005, 30 Years after Initial Observations in Lyme Connecticut. Wien Klin Wochenschr 118(21–22):625–33.

[14} http://medicineworld.org/stories/lead/7-2010/protection-against-ticks-that-carry-lyme-disease.html

Here come the ticks: is global warming leading to an increase in Lyme disease?

This is the last of 16 student posts, guest-authored by Jessica Waters. 

Climatologists have been warning us about the ongoing and impending consequences of global warming for years. But the results of climate change affect more than just polar bears and penguins  – if you live anywhere in the northeastern, north-central or west coast states of the U.S.., you could be at a greater risk for contracting Lyme Disease.

Lyme disease is an infection of the Borrelia burgdorferi bacterium that is spread through black legged ticks (otherwise known as deer ticks) who feed on the white footed mouse species, also known as the wood mouse, which carries the bacteria.  The symptoms of the disease itself include fever, headache, fatigue, and a telltale “bulls eye” rash near the site of the tick-bite. Left untreated, Lyme disease can spread to affect the joints (causing arthritis), heart, and nervous system – often causing irritability and mood swings.

Lyme disease transmission occurs in a Reservoir à Vector à Host cycle.  A Reservoir is the habitat in which an infectious agent normally lives, grows and multiplies – in this case, it is the white-footed mouse. A disease vector is a carrier animal (usually an arthropod) that transfers an infective agent from one host to another- i.e. the blacklegged tick.  And the host in this scenario is an organism that harbors an infective agent – us, our pets, and other animals.

Lyme disease is transmitted when a nymphal (young) tick feeds on a B. burgdorferi carrying white-footed mouse. The contaminated bloodmeal that it ingests allows the bacterium to live on in the tick (the vector), and the infected tick can then transmit the bacteria to its next host – a dog, your child, you, or any other animal roaming around in a wooded area.

Nearly a quarter of all Lyme disease cases are in children, as they play near to the ground, where host-seeking ticks are often waiting.  The CDC reports that pet owners and outdoorsy types are also at higher risk, as dogs and people traipsing through thick brush can easily pick up a tick or two without realizing it.

So how does climate change factor into this? According to ecologist Rick Osfeldt, a small mammal expert in Millbrook , New York, it all comes down to acorns.

“ Acorn abundance gives rodents a jump start on breeding. By the next summer, mice numbers are through the roof”.

This phenomenon gave rise to a “mouse-boom” in 2010, a low-acorn year in 2011, and what promises to be a busy summer for public health officials in 2012.  As the theory goes, as nymphal ticks wake up to a low mouse count (from 2011), they will feed on the existing mice and then turn to the next best thing – humans.

While the exact science behind what causes oak trees to produce more acorns is not yet identified, studies suggest that plants in warmer climates produce more seeds.

More acorns means a bumper crop for hungry mice, and milder winters mean higher breeding rates and higher survival rates for the B. burdorferi carrying rodents.

Maria Diuk-Wasser, an assistant professor of epidemiology at the Yale school of public health also attributes an increase in Lyme disease to higher average temperatures, but for a different reason.

“One possible way in which temperature may limit tick populations is by increasing the length of their life cycle from two to three years in the north, where it is colder.”  As average temperatures increase, climate change could be reverting the normal temperature pattern and increasing the production Lyme disease carrying ticks.

If both hypothesis prove to be true (and so far, CDC reported cases of Lyme disease have increased from 15,000 in the mid 1990s to over 40,000 today), an increase in both mouse and tick populations could indicate an increased prevalence of Lyme disease in years to come.

It may also be that the number of (geographically) susceptible people will increase as well. Nick Ogden, a zoonoses  researcher with the Public Health agency of Canada recently published a paper suggesting that the tick-inhabitable regions of North America may be increasing – in Eastern Canada, the tick inhabitable region will expend from 18% to over 80% by 2020, while the average temperatures in Canada have simultaneously increased by 2.5 degrees Fahrenheit over the past 60 years.

While some measures can be taken to prevent infection of Lyme disease once a tick has made a meal of you, cautionary measures are the best way to prevent you and your loved ones from becoming hosts.

The CDC recommends using insect repellant, applying pesticides, reducing tick habitat (i.e. cutting down heavy brush areas in your yard), and wearing long sleeves and pants when in wooded areas.  Prompt removal of ticks is also necessary, so continually check exposed skin areas when you are outdoors  -the backs of your legs, the back of your neck, the ears of your dog, etc.

One creepy-but-saving grace in tick removal may be that once a tick has landed on you, it will not immediately attach, instead crawling around for up to three hours to find an ideal location to feed. While not pleasant to imagine, it may give you enough time to jump in a hot shower after time outdoors and wash off any unattached ticks. Even attached ticks still require 24 to 36 hours to spread the B. burgorferi bacteria into your blood – if you remove a tick within 24 hours, you are greatly reducing your chances of getting Lyme disease.   Attached ticks  should be removed gently with tweezers.

If diagnosed early, Lyme disease can be cured with antibiotics. If you find an attached tick, see a general practitioner. You may be offered a single dose of antibiotics if you were bitten by a Lyme disease carrying tick species and the tick has probably been attached for at least 36 hours.

So, perhaps most importantly, if you suspect that you may have been bitten by a tick or have symptoms of Lyme disease – get thee to a doctor, and consider saving the planet from further warming by riding your bike there.

Online Sources:

http://www.cdc.gov/lyme/

http://www.cdc.gov/lyme/transmission/blacklegged.html

http://www.who.int/topics/zoonoses/en/

http://www.huffingtonpost.com/2012/04/04/global-warming-lyme-disease-west-nile_n_1400692.html

http://www.mnn.com/health/fitness-well-being/blogs/experts-predict-major-increase-in-lyme-disease-for-2012

Patrick A. Leighton, Jules K. Koffi, Yann Pelcat, L. Robbin Lindsay, Nicholas H. Ogden. Predicting the speed of tick invasion: an empirical model of range expansion for the Lyme disease vector Ixodes scapularis in Canada.Journal of Applied Ecology, 2012; DOI: 10.1111/j.1365-2664.2012.02112.x