Lyme Disease Download

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Lyme Disease
Ashley Elwell
Concordia University
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Introduction
Since I live in Minnesota checking for ticks when I get home from my outdoor
adventures has become routine. As soon as you spot one that creepy crawly feeling of more
tagging along takes a hot shower to get rid of. The real concern of bringing ticks home with you
is the potential disease that they may carry. This can become a real concern for outdoors lovers.
Knowing more about the disease and how to prevent it will benefit those living in areas that
these ticks can be found. This paper looks at the epidemiology, biostatistics, biomedical basis as
well as social and behavioral factors of lyme disease.
Epidemiology
Lyme disease is the most common vector borne disease reported in the United States
(Orloski, et al., 2000) with around 25,000 cases reported per year (CDC, 2013). The etiologic
agent is spirochete Borrelia burgdorferi which is carried by two types of ticks. The Ixodes
scapularis, better known as the deer tick, is found in the northern midwest of the country. The
disease is also carried by the Ixodes pacificus, more commonly known as the black legged tick
found on the western coast. Rodents and small mammals serve as reservoirs for the disease. The
people that live, work and play in infested areas where these ticks reside are most at risk of
infection.
They are found in wooded areas mostly in the northeast from Virginia to Maine,
Wisconsin, Minnesota and northern California (CDC, 2013) with the highest amounts of cases
happening between the months of May and October (Rodhain, 1989). The most defining
symptom of Lyme disease is erythema migrans which is a rash that develops as early as a day
after a bite or as late as a month after. It has a distinctive ring like appearance around the bite
making it an easy way of diagnosing the disease. Erythema migrans is a characteristic of the
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bacterial infection and is so specific to Lyme disease that no other tests are necessary to
diagnose. Other symptoms are not as specific including malaise, headaches, muscle pain, fever,
fatigue and joint pain (Orloski, et al., 2000). The generality of these symptoms in the absence of
erythema migrans make testing necessary in order to diagnose Lyme disease. According to the
American Lyme Disease Foundation lyme disease is not considered lethal by most physicians
(ALDF, 2013). A study done by the CDC looking at lyme disease as an underlying cause of
death on death certificates from 1999-2003 found only 23 cases out of 96,068 reported to be
lethal resulting in a low mortality rate.
In order for Lyme disease to be diagnosed it must meet criteria. One is a physiciandiagnosed erythema migrans that is five centimeters or larger in diameter. The other is at least
one disseminated manifestation plus a laboratory confirmation of the infection. Testing includes
an enzyme immunoassay or immunofluorescence assay. If that comes back positive then a
Western immunoblot test is the last step. These are necessary steps to be taken in order to not
misdiagnose a patient with Lyme disease and to be sure that a true incidence is being reported
(Orloski, et al., 2000).
Research done among forest inspectorates in Poland found that 70 percent of those with
general symptoms had a “permanent presence”. Only 25 percent experienced them “periodically”
with even less, 5 percent, experiencing them “sporadically” (Lewandowska, et al., 2013). The
incidence of disease was found to be more frequent with the older foresters that had been
working in that environment longer increasing their amount of exposure.
To keep track of patterns of Lyme disease in the United States diagnoses are reported
using a combination of passive, active and laboratory based surveillance. Passive is when a
health-care provider diagnoses a patient and then reports that to either their local or state public
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health. The state then verifies this and can via the internet submit it to the CDC. Active
surveillance is when public health staff make the effort to contact the health-care providers to
find out what they have diagnosed. Laboratory-based surveillance is required in order to report a
positive test to the health department (Orloski, et al., 2000).
Lyme disease is caused by the bite of infected ticks, which are found primarily on the
west coast and northern Midwest of the United States. Those most at risk of contracting the
disease are people who are exposed to the wooded areas and tall grasses where these ticks
inhabit. There is also risk of them being carried indoors by rodents and pets such as cats and
dogs. Symptoms can be vague and therefore diagnosis by laboratory tests are necessary to verify
infection. A better understanding of lyme disease starts with the biology.
Biomedical Basis
The bacteria that causes Lyme disease belongs to the family Spirochetaceae, genus
Borrelia and the species B. burgdorferi s. s. specifically in the United States and species B.
affzeli and B. garinii in Europe (Krupka, et al., 2007). It has been found that people in the United
States experience more joint pain while those in Europe have more skin and nervous system
symptoms. The symptomatic difference from those suffering from Lyme’s disease in the United
States and Europe is due to a structural difference between the species.
Borrelia Structure
Borrelia is a spirochete bacteria. It has a wavy or spiral shape. Its ability to be so
infectious is due to the fact that it is motile. The bacteria has a flexible body and flagella that
allow this. According to the University Hospital Heidelber (2009) the three types of the pathogen
have different numbers of flagella which might explain the difference in symptoms experienced.
The surface-exposed lipoproteins, OspA, are the main focus of vaccine efforts being researched.
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B. burgdorferi Characteristics
This is a host associated bacteria, meaning it relies on a host to survive like the tick it
resides in or animal or human it is passed on to. It is 10-30 um in length with 7-14 flagella for
mobility. There is not a rigid cellular wall so this does not have an active role in keeping its
shape. A special characteristic of this bacteria is that it does not have the circular chromosome
and extrachromosomal that other spirochetes have but rather a linear one. The ends of the
chromosome have closed hairpin telomeres which is not a common characteristic of a
prokaryote. This is something found on the DNA of double stranded DNA viruses. The genomic
structure and cell organization that is specific to this bacteria shows a past that was potentially
involved “trans kingdom genetic exchange” (Barbour, 1993).
Transmission From Tick To Humans
Lyme disease is caused by the passing of Borrelia from infected ticks to animals or
humans. Krupka, et al., (2007) gives a closer look at how this happens
● Borrelia attaches to the tick’s gut epithelium via OspA-TROSPA interaction.
● Intake of the human/animal blood with plasminogen.
● Plasminogen binds on the OspA and is activated.
● Borrelia then passes through the gut epithelium.
● Borrelia passes through the haemocoel to the tick salivary gland.
● The outer proteins of Borrelia change profile and binds to the immunosupressive Salp15.
● Borrelia leaves the tick.
● Borrelia enters the animal/human.
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Cultivation
Successful cultivation is vital to research. Because this bacteria is unique in its structure
as previously talked about it is also difficult to cultivate. With modifications a medium that has
proved workable is the Barbour-Stonner-Kely (BSK). This is a fluid medium with a high density.
In order for Borrelia to grow on this medium there are amino acids, cofactors, salts, N-acetyl-Dglucosamine and other variable components combined. This is a unique genome when it comes
to the biology of Lyme’s disease which is why it continues to be studied.
Biological Effects on Body
Once the borrelia enters the blood stream of the animal/human immune response is
triggered by the outer proteins (Krupka, et al., 2007). According to Mayo Clinic (2013) this
response results in flu-like symptoms including fatigue, fever, chills, and body aches. A
symptom specific to the borrelia infection is a bulls-eye like rash. If the infection continues joint
pain and neurological problems may develop. In rare chronic cases there may be heart problems,
swelling of the eyes, hepatits and severe fatigue. Common symptoms in reported cases and be
found on www.cdc.gov among other statistics related to Lyme disease.
Biostatistics
Biostatistics such as 80% of Lyme disease cases happening in the regions of the
northeastern and mid-Atlantic States lead to studies like one comparing genetics of the virus
carrying tick to ticks without the virus found in other geographic areas (Qui, et al., 2001). It is
thought that the genetic structure of the tick has been shaped by the history of the geographical
area it resides. It is important with any disease to gather information that better help us prevent
those that are at risk by educating the public with numbers they can comprehend and relate to.
These numbers can then be compiled to create tables and charts for an even better understanding,
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like this graph showing the reported cases of Lyme disease by year in the United States (CDC,
2013).
According to the CDC Lyme disease was the “sixth most common nationally notable
disease” in 2011. Of the cases diagnosed and reported that year 96% were found in 13 states of
the Northeast and upper Midwest including Connecticut, Delaware, Massachusetts, Maryland,
Maine, Minnesota, New Hampshire, New Jersey, New York, Pennsylvania, Vermont, Virginia
and Wisconsin (CDC, 2013). Statistical information on Lyme disease is closely collected,
reported and monitored on a local level by health care providers diagnosing the cases and then on
a national level by the Center for Disease Control and Prevention. The data is verified by the
CDC and then put into a public use data set allowing anyone to access the information.
The data that is collected and then used when a case is properly diagnosed and reported includes
location of the case (by county), the year the case was diagnosed, age of the affected person,
their sex and the symptoms experienced. The symptoms reported include cardiac,
meningitis/encephalitis, radiculoneuropathy, Bell’s palsy, arthritis and erythema migrans (CDC,
2013). This information is reported yearly, using the population as of July 1st of the year to
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calculate incidence rates. It is compiled by and then tables, charts and maps of the cases are
created.
Access to these figures is at the CDC website www.cdc.gov in order to educate people of
the risk they face. The tables available include cases by state and incidence by state for the years
2002-2011. Incidence is per 100,000 people. The charts people can look at are separated into
cases by year, age and sex, month, and symptom. This gives the public many ways to look at the
risk of Lyme disease like the time of year it is most reported. It also shows what the most popular
symptom is for people at the time of diagnosis.
The maps on the website, like the one of Reported
Cases of Lyme Disease in 2011 (CDC, 2013)
shown here, show the areas of the United States
with the highest occurrence. This is shown by a
dot per case placed in the county it was reported.
The statistics for Lyme disease are collected and
presented in a very efficient way to best get the information to the public. The information needs
to be presented in most effective way to encourage people to take action. Behavioral and social
factors must be taken into account to achieve this.
Behavioral and Social Factors
It does not seem like there would be significant social and behavioral factors for a disease
such as Lyme’s that is contracted from worry free outdoor activities. There are however
behaviors that will aid in prevention of contracting Lyme disease. A couple ways to look at the
likelihood that an individual will take these steps are using the Health Belief Model and the
Ecological Method.
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Health Belief Model
According to Boston University School of Public Health (2013) the Health Belief Model
is based on the individuals desire to avoid illness and the belief that a specific action will prevent
or cure an illness. Whether or not a person will take recommended action to prevent illness is
based on the following:
1. Perceived susceptibility- Does the individual feel they are at risk? Those living, working
and playing in heavily wooded areas find themselves at higher risk of contracting Lyme
disease via tick bite.
2. Perceived severity- Is the risk a serious one? Lyme disease, undiagnosed, can be a lethal
illness. By the time it is diagnosed the affected person may have suffered from flu-like
symptoms, joint aches and pains and even neurological symptoms.
3. Perceived benefits- The perception of the individual that action will be effective in
reducing threat. People must believe or be convinced that preventative steps such as
tucking in socks when out in the woods or tall grass, wearing hats, using repellents and
checking for ticks after activity will reduce their threat of contracting Lyme disease.
Residents in Connecticut responded to a community-wide education program with an
increase of 7% checking for ticks and 5% using repellents to make a total of 99% of the
population surveyed that used personal protective behaviors once told of the benefits
(Gould, et al., 2008).
4. Perceived barriers- What obstacles to people see in taking the health action? The only
obstacles apparent for people are that of convenience and cost. While 99% of the people
in the community in Connecticut mentioned previously were taking protective measures,
a majority of them would not spend more than 100 dollars to do so. On an individual
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basis this would not be a problem, but communities might face expenses at this level
when treating large areas.
5. Cue to Action- The stimulus needed for an individual to take action. For many people the
discovery of one tick is enough to take action. In my experience many cannot get rid of
the “creepy crawly” feeling that more ticks are hiding. Once an individual is actually
bitten they may have more incentive to take preventative action. There is also an increase
of preventative behaviors in people that have had Lyme disease themselves or have had a
family member with as well as an increase with age (McKenna, et al., 2004).
6. Self-efficacy- An individual’s confidence in performing the preventative behavior. With
behaviors as simple as tucking pants into socks, applying bug repellent and checking for
ticks in a hot shower after activity most people finding themselves at risk of Lyme
disease are able to successfully take action to protect themselves.
Ecological Model
The Ecological Model (Schneider, 2011) can be applied to Lyme disease as followed. At
the intra-personal level by educating individuals of their risk of contracting the disease and
supplying them with preventative measures to take. At the intrapersonal level family and friends
that share the same outdoor activities as well as coworkers who work in wooded areas will
influence individuals to take action as they do. If parents teach their children to take part in
preventative behaviors they will be more likely to continue this. Institutional factors would fall
under businesses supplying employees with proper repellents and clothing. This would also
include schools taking proper precautions when on field trips and teaching prevention in the
classroom in areas where Lyme disease is prominent. The Community can help educate by
posting information at trail and park entrances as well as treating areas of heavy foot traffic with
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tick insecticides. Public policy would come into play when keeping track of the incidence of
Lyme disease, making sure that diagnosed cases are reported so data used to keep up to date
information can be collected.
Summary
Research and surveillance of Lyme disease has led to a better understanding of where and
when infection may occur. This together with education of the seemingly harmless symptoms of
Lyme disease can lead to people making the connection and going in for diagnosis. While it is
only prominent in certain areas of the United States it is something for locals and travelers to
keep in mind and take preventative steps to avoid.
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References
American Lyme Disease Foundation website. Retrieved from
http://www.aldf.com/Misinformation_about_Lyme_Disease.shtml
Barbour, A. G. Fish, D. (1993). The Biological and Social Phenomenon of Lyme Disease.
Science. Vol. 260(5114), June 1993, pp. 1610-1616.
Boston University School of Public Health. (2013). The Health Belief Model. Retrieved August,
4, 2013 from http://sph.bu.edu/otlt/MPH-Modules/SB/SB721-Models/SB721Models2.html
Centers for Disease Control and Prevention website. Retrieved from http://www.cdc.gov/lyme/
Gould, H. L., Nelson, R. S., Griffith, K. S., Hayes, E. B., Piesman, J., Mead, P. S., & Cartter, M.
L. (2008). Knowledge, Attitudes, and Behaviors Regarding Lyme Disease Prevention
Among Connecticut Residents, 1994-2004. Vector-Borne and Zoonotic Diseases.
Volume 8, Number 6.
Krupka, M., Rask, M., Belakova, J., Horynova, M., Novotny, R., & Weigl, E. (2007). Biological
bacteria of the Borrelia burgdoferi species group. Bromed Pap Med Fac Univ Palacky
Olomouc Czech Repub, 151(2): 175-86.
Lewandowska, A., Kruba, Z., Filip, R. (2013). Epidemiology of Lyme disease among workers of
forest inspectorates in Poland. Annals of agricultural and environmental medicine,
20(2):329-31.
Mayo Clinic. (2013). Retrieved from http://www.mayoclinic.com/health/lymedisease/DS00116/DSECTION=symptoms
McKenna, D., Faustini, Y., Nowakowski, J., Wormser, G. P. (2004). Factors influencing the
utilization of Lyme Disease- prevention behaviors in a high-risk population. J am Acad
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Nurse Pract. 16(1): 24-30. Retrieved from
http://www.ncbi.nlm.nih.gov/pubmed/15008035
Orloski, K.A., Hayes, E. B., Campbell, G. L., Dennis, D. T. (2000). Surveillance for Lyme
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Rodhain, F., Perez-Eid, C. (1989). Lyme disease: epidemiology. La Revue du praticien,
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Schneider, M. (2011). Introduction to Public Health [Kindle Version]. Retrieved from
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Qui, W., Dykhulzen, D. E., Acusta, M.S., & Luft, B. J. (2001). Geographic Uniformity of the
Lyme Disease Spirochete (Borrelia burgdorferi) and Its Shared History With Tick Vector
(Ixodes scapularis) in the Northeastern United States.