Incidence and Reporting of Lyme Disease in the Endemic Area of Martha’s Vineyard, Massachusetts
Avinash Sridhar, UMass Medical School Class of 2015
Tick borne illnesses (TBIs), such as Lyme disease, are endemic on the island of Martha’s
Vineyard, Massachusetts. By using the novel method of payer data of on-island monthly
prescriptions of doxycycline for 2008 – 2011 and 2012 through June, we have found that there
has been a drastic under-reporting of the on-island incidence of Lyme disease when
compared to that which is published by the Centers for Disease Control (CDC). This source of
real-time data can provide a means of monitoring efficacy of TBI prophylactic treatment with
doxycycline as well as improve efforts to increase awareness of TBIs on the island in full-time
island residents, summer residents, and vacationing populations.
Introduction:
The island of Martha’s Vineyard, Massachusetts, has long been considered an endemic area of tick-borne
illnesses. In 2010, the island’s health commissioners launched a 5 year campaign aimed at reducing the
incidence of disease by 70%, bringing it in line with that of Cape Cod, Massachusetts. An initial goal of this
project was to obtain accurate baseline incidence data. Existing data reported by the CDC indicated <30 patients
suffering from Lyme disease from 2008 - 20111, which is well below the generally appreciated incidence level
and too low such that monitoring intervention was inaccurate and untimely. This was confirmed by comparing
the number of doxycycline prescriptions administered for Lyme disease with the reported CDC incidence data.
The novel use of payer databases allows an efficient, timely, and less labor intensive method for accurately
monitoring the incidence of Lyme disease on the island of Martha’s Vineyard.
Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite
of an infected tick.3, 4 Most commonly, B. burgdorferi infects blacklegged deer ticks (Ixodes scapularis) in the
northeastern United States whereas the western blacklegged deer tick (Ixodes pacificus) is responsible for
disease on the Pacific coast. Infected I. scapularis are very common on the island of Martha’s Vineyard and are
found in wooded and bushy areas with dense leaf litter.2 While B. burgdorferi-infected deer ticks are most
commonly found parasitizing the white-tailed deer (Odocoileus virginianus,) these deer are incapable of being
infected with Lyme disease. Instead, the most common reservoirs of infection are small rodents and birds. I.
scapularis have a two year life cycle where eggs are laid and larva hatch in the spring. Primary parasitization of
small rodents and birds occurs in the summer months. During the spring of the following year, these larvae
mature into nymphs and reach full adulthood in the following fall. The spring and summer months during the
second year of life are when the risk of human infection are greatest.5
The pathogenesis of Lyme disease can progress in three main stages. Stage one of the infection presents as
an acute illness after being bit by I. scapularis and manifests as an erythematous papule which may or may not
include the distinctive erethema chronicum migrans, more commonly known as the “bull’s eye rash.” These
symptoms may be accompanied by fever and lymphadenopathy and usually disappear in 4-12 weeks. Stage 2 is
the early disseminated stage of the disease where spirochetes spread hematogenously throughout the body
and cause secondary skin lesions, lymphadenopathy, migratory joint and muscle pain, cardiac arrhythmias, and
meningitis often associated with cranial nerve involvement. A common result of these neurological
involvements is facial nerve paralysis resulting in Bell’s palsy. In stage three, or the late disseminated stage of
the disease, Lyme borreliae can cause a chronic arthritis that may include severe damage to large joints. Also,
polyneuropathy and encephalitis can vary in severity from mild to debilitating states. This final stage can
manifest up to 2 or 3 years post-tick bite.6
Lyme disease is most often treated with the tetracycline antibiotic doxycycline. Doxycycline is a broadspectrum bacteriostatic antibiotic that inhibits protein synthesis. Doxycycline absorption after oral
administration is approximately 95% - 100% and is distributed throughout the body 40% - 80% bound to serum
proteins. Doxycycline is metabolized in the liver and eliminated from the body mainly in bile, urine, and feces.
Adverse effects of doxycycline most commonly include photosensitivity and gastrointestinal effects such as
nausea, vomiting, and diarrhea.7
Methodology:
Prescribed doxycycline was used as a surrogate for Lyme disease and tick bites. Pharmaceutical
market data was obtained from Source Healthcare Analytics (SHA) and included dispensed
doxycycline prescriptions on-Island by month, by days of therapy, by patient age for all islanders with
a sixth grouping for all off-Island residents for the years 2010 through the present. To use prescription
and physician visit databases to validate approach and its limits, a one-time representative report of
all island doxycycline prescriptions grouped by ICD 9 code to validate the percentage of doxycycline
written for Lyme disease to determine the extent of overstatement in use of doxy surrogate was used.
Also, the total doxycycline yearly on-Island retail inventory turnover for years 2008 through 2011 was
collected and compared with corresponding gross values from payer prescription database. To further
validate doxycycline as an acceptable surrogate for on-island Lyme disease, a survey was given to all
island physicians and asked them to report the percentage of doxycycline they prescribed exclusively
for Lyme disease as well as other tick-borne illnesses.
Data:
Methodology
CDC "Confirmed" Cases
Doxycycline* Prescriptions
Doxycycline* Pills
Doxycycline Pills per Prescription
2008
47
903
27783
30.8
2009
28
880
26871
30.5
2010
25
803
25082
31.2
2012
N/A
977
26895
27.5
Discussion:
Advantages and limitations of this approach to incidence reporting include:
•
Larger treatment capture numbers enable better intervention monitoring
•
Ability to follow patients longitudinally
•
Ability to measure local standards of care
•
Ability to link longitudinal diagnosis, treatment, and cost data
•
Timeliness, especially in times of endemic / epidemic crisis
Works Cited:
Centers for Disease Control, 2011
1. Martha's Vineyard Boards of Health, Island-Wide Tick Borne Illness Prevention Program.
(2012). Tick-borne incidence findings. Retrieved from website: http://www.mvboh.org/tick-borneillness/about
2. Centers for Disease Control and Prevention, Bacterial Diseases Branch (2011). Lyme disease
transmission. Retrieved from website: http://www.cdc.gov/lyme/transmission/index.html
3. Hengge UR, et al: Lyme borreliosis. Lancet Infect Dis 2003; 3:489.
4. Hoppa E, Bachur R: Lyme disease update. Curr Opin Pediatr 2007; 19:275.
5. Centers for Disease Control and Prevention, Bacterial Diseases Branch (2012). Life cycle of
hard ticks that spread disease. Retrieved from website:
http://www.cdc.gov/lyme/transmission/index.html
6. Kumar, V., Abbas, A. K., Fausto, N., & Aster, J. C. (2010). Robbins and cotran pathologic basis
of disease. (8 ed., pp. 377-378). Philadelphia, PA: Saunders.
7. Deck D.H., Winston L.G. (2012). Chapter 44. Tetracyclines, Macrolides, Clindamycin,
Chloramphenicol, Streptogramins, & Oxazolidinones. In B.G. Katzung, S.B. Masters, A.J. Trevor
(Eds), Basic & Clinical Pharmacology, 12e. Retrieved August 13, 2012 from
http://www.accessmedicine.com/content.aspx?aID=55829359.