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Course: Tickborne Diseases Return to Course Outline

Tickborne Diseases

An overview of identification, testing and prevention for four common types

Learning Objectives
After reading this article, the learner will be able to:
1. Identify symptoms of tickborne illness.
2. Describe the appropriate tests for identifying tickborne illness.
3. Provide examples of patient education related to tickborne diseases. 

Several tickborne diseases are common in the United States. This article focuses on four of the most prevalent types: Lyme disease, Rocky Mountain spotted fever, Ehrlichiosis and Babesiosis.

Tickborne diseases are passed to humans through the bite of an infected tick. In order for a tick to transmit disease, the insect must first draw the blood of a small mammal carrying the organism. Once the organism is present in the tick, it can be transmitted to a host during the tick's blood meal. Not all tickborne diseases are caused by the same type of tick; each causes a specific disease process.

Some tickborne diseases have been transmitted by methods other than tick and host. For example, Lyme disease and Babesiosis have been implicated in transmission through organ donation and blood transfusion. Because symptoms can be minor or absent, infections can be present in the donor organ or blood during donation and transmitted to an immunocompromised recipient, causing infection. When this type of transmission occurs, a tickborne disease is not commonly the first clinical thought.

Screening patients for tickborne illness includes asking about their history of outdoor activities, noticeable tick bites, skin rash, geographic location, presence of pets in the home, and travel to areas known to have ticks. Blood transfusion and organ donation are not necessarily part of a clinical patient history to rule out these types of infections.

Lyme Disease

Lyme disease is caused by the spirochete Borrelia burgdorferi. A spirochete is a corkscrew-shaped organism. The disease was first recognized in the United States in 1975 near Lyme, Conn.1 Providers noticed an unusual outbreak of arthritis in this region of the country, which led to investigation of the cause. The disease was identified and named in 1982.2

B burgdorferi uses mice as a typical reservoir, but the tick lives on deer and other mammals as a host. The black-legged tick (Ixodes scapularis) and the Western black-legged tick (Ixodes pacificus) are the most common carriers of B burgdorferi.3 The black-legged tick is found in the Northeastern and upper Midwestern United States, whereas the western black-legged tick is found along the Pacific coast, particularly northern California. Black-legged ticks are most prominent during the spring, summer and fall, and they search for a host during the winter months, when temperatures are above freezing.3 The nymphs and adult females are most likely to bite humans.

Lyme disease can also be transmitted through organ donation. B burgdoferi has been transmitted in kidney, heart and allogeneic hematopoietic stem cell transplant recipients.4 The risk of transmission through transplantation has been increasing due to population changes. The population of immunocompromised hosts is growing as the number of annual transplantations increases. Transplant recipients are living longer and receive more powerful immunosuppressive agents.4

The first typical clinical manifestation of Lyme disease is erythema migrans, which occurs in about 70% to 80% of patients with the infection.2 The erythema migrans is a red macule or papule that expands and reaches at least 5 cm in diameter. Other symptoms may also present, such as: malaise, fatigue, fever, headache, stiff neck, myalgia, migratory arthralgias and/or lymphadenopathy.2 If left untreated, these symptoms can last several weeks.

Blood testing can be performed for the purposes of diagnosis. The sensitivity of the tests increases as the disease progresses. Interpreting the results of the test can be complicated if a good patient history is not obtained. Cross reactions with immunofluorescence and enzyme-linked immunosorbent assay may occur when a patient has underlying conditions such as syphilis, relapsing fever, leptospirosis, HIV, Rocky Mountain spotted fever, infectious mononucleosis, lupus or rheumatoid arthritis.2

The CDC guidelines for performing these tests are two tiered and presented in the form of a decision tree (see figure).5 A positive result requires a second test, and the length of symptoms provides guidance for which test to use. A negative result could mean another diagnosis, or if the symptoms are less than 30 days old, to consider a convalescent serum.



Rocky Mountain Spotted Fever

Rocky Mountain spotted fever is a rickettsial disease caused by Rickettsia rickettsii. Rocky Mountain spotted fever is transmitted by the American dog tick (Dermacentor variabilis), the brown dog tick (Rhipicephalus sanguineus) and the Rocky Mountain wood tick (Dermacentor andersoni). The disease is named for Howard T. Ricketts, who proved in 1906 that the wood tick was involved in the transmission of R rickettsi.6

The American dog tick can be found east of the Rocky Mountains and in limited areas on the Pacific Coast; brown dog ticks are found worldwide; and Rocky Mountain wood ticks are found in Rocky Mountain states and southwestern Canada.3 Both American and brown dog ticks use dogs as their primary host, however, they may also bite humans or other mammals.3 The risk for bites is highest during the spring and summer.

Early stages of Rocky Mountain spotted fever may be confused with Ehrlichiosis and include: sudden onset fever persisting for 2 to 3 weeks, malaise, deep muscle pain, severe headache, chills and conjunctival injection.2 Patients may also develop a maculopapular rash on the extremities on the third to fifth day. This rash usually spreads to the palms of the hands and soles of the feet. When treated properly and in a timely manner, death is rare.2

Testing for Rocky Mountain spotted fever can be accomplished using blood samples. Serology testing of acute and convalescent IgG and IgM can detect antibodies. Skin biopsy of the maculopapular rash is also an acceptable specimen for histology. A nucleic acid amplification test or immunohistochemical staining of the skin can be ordered. The staining will identify antigens up to the first 24 hours after antibiotic therapy has been initiated.7

Ehrlichiosis

Ehrlichiosis is an infection caused by a bacterium in the family of Anaplasmataceae. This group consists of small, obligate intracellular, pleomorphic bacteria that survive and reproduce in the phagosomes of mononuclear or polymorphonuclear leukocytes of the infected host.2 The agent, Ehrlichia chaffeensis, is named after Fort Chaffee, Ark., which is where the first isolate was obtained from a patient.2

This infection is spread by the bite of the Lone star tick (Amblyomma americanum). The Lone star tick is aggressive, and the adult female is identifiable with a white dot or "lone star" on her back.3 The wound associated with a Lone star tick bite can be irritated and red, however, this does not indicate the spread of Ehrilichiosis. The Lone star tick is commonly found in the Southeastern and Eastern United States.

The symptoms of Ehrlichiosis are nonspecific and can include: fever, headache, anorexia, nausea, myalgia and vomiting. Ehrlichiosis can cause meningoencephalitis in about 20% of patients.2 Ehrlichiosis can be mild to severe and has a 2.7% case-fatality rate.2 Testing can be performed on the blood of a suspected patient by performing a blood smear. A negative smear does not necessarily indicate that Ehrlichiosis is not present, since the sensitivity of the test is often low and variable.

Babesiosis

Babesiosis is caused by intraerythrocytic protozoan parasites such as Babesia microti and Babesia duncani, both of which occur predominately in the United States.2 The black-legged tick (Ixodes scapularis) can transmit Babesiosis.3 Black-legged ticks can be found in the Northeastern and upper Midwestern United States. Tick bites by the black-legged tick are most likely to occur in the spring, summer and fall and are delivered by the nymphs and adult females.

Babesiosis may also be transmitted through blood transfusion. Even though the ticks that spread this disease are found in the Northeast and upper Midwest, the infection can be transmitted anywhere in the country due to travel. When humans travel, they can pick up the illness, return home, donate blood and unknowingly transmit the illness to a blood donor recipient.

Certain circumstances are required for transfusion-related infection to occur. First, the agent must establish a viable infection in the blood donor. Second, the agent must be present and/or circulate in the peripheral blood of the donor. Third, the agent must survive the blood collection process and remain viable under normal blood storage conditions. Last, the agent must be able to infect the blood recipient following blood transfusion.8

The American Red Cross reported 18 cases of Babesiosis transmission via blood transfusion between 2005 and 2007 (national), six cases in Rhode Island in 2007 and seven cases in New York City in late 2008.8 All blood transfusion cases in the United States, with the exception of two, have been with Babesia microti infection. The literature also contains report of a patient who contracted Babesiosis during blood transfusion for a heart transplant.9

Currently, blood donors are screened prior to donation and asked health history questions associated with exposure to Babesiosis. This is recommended according to American Association of Blood Banks standards. Screening does not always eliminate spread of the infection because the affected person can carry the infection yet be asymptomatic or exhibit mild symptoms. The American Red Cross is working to improve the safety of the blood supply by working with a company on an investigational test to detect Babesia DNA and the presence of antibodies to Babesia in donor blood.

Signs and symptoms of Babesiosis can include fever, chills, myalgia, fatigue and jaundice. These symptoms are similar to many other types of infection. A cough, sore throat, emotional lability, depression, photophobia and conjunctival injection may occur, but are less common. The incubation period for Babesiosis is 1 to 9 weeks. A peripheral blood smear, polymerase chain reaction or isolation of the Babesia parasite are acceptable diagnostic laboratory tests.

Prevention and Treatment Measures

Precautions against tick bites are the only way to prevent tickborne illness. Protection methods include: wearing light-colored, long-sleeved and long-leg clothing when outdoors; wearing insect repellant that contains DEET (N,N-diethyl-meta-toluamide); and checking the skin for any signs of a tick or tick bite upon returning indoors.

When checking the skin, patients should examine skin folds, crevices and under arms because ticks can hide in these areas. Animals may also carry ticks indoors, so pets need to be checked regularly. If ticks are transported indoors on a pet, they may infect the pet with a bite or crawl onto a human.

Ticks need a host in order to spread infection. If a tick is found attached to the skin, removal is necessary. Use tweezers to ensure removal of the mouthparts. Mouthparts alone cannot transmit tickborne illness, but they can cause a skin infection if they remain embedded in the skin.

Antibiotics are used to treat tickborne illness in patients. The Centers for Disease Control and Prevention has published treatment recommendations for tickborne disease.3 A consult with an infectious disease specialist may be necessary.

Case Example

The following case example illustrates a typical presentation and how CDC recommendations can be followed.

"J.P." is a 35-year-old woman who presents to her primary care office with complaints of rash. During the review of symptoms and recent history of present illness, J.P. states that she had noticed a circular rash on her left underarm. She reports no pain or pruritus at the rash site. She also reported no exposure to any known allergens.

During a careful examination, the NP provider identified a 7-cm "bulls-eye" circular rash that was neither raised nor blanching. It was warm to touch. After a brief review of the history of present illness, the NP learned that the patient had recently been hiking with her golden retriever in a nearby Pennsylvania state park and had later found a tick at the site of the current rash.

J.P. reported having no fever, chills, headache or swollen lymph nodes, but stated that she had been experiencing generalized headaches, as well as muscle aches and slight fatigue. She attributed the muscle aches to the exertion of the hike 8 days prior, when the tick bite occurred. J.P. said she was able to remove the tick with tweezers, but that she hadn't become aware of the tick until the day after the hike. She washed the site with soap and water.

With a differential diagnosis of Lyme disease secondary to a tick bite and common presenting symptoms, the NP orders first step testing EIA, which has a positive result. The NP then proceeded to the second step, the Western blot test. After positive EIA and immunoblot results, the NP concluded that J.P. must be treated based on the CDC guidelines for Lyme disease.

Note: The two steps of Lyme disease testing are designed to be done together. The CDC does not recommend skipping the first test and doing the Western blot only. Doing so will increase the frequency of false-positive results and may lead to misdiagnosis and improper treatment.

Patients treated with appropriate antibiotics in the early stages of Lyme disease usually recover rapidly and completely. Antibiotics commonly used for oral treatment include doxycycline, amoxicillin and cefuroxime axetil. With no allergies to medications, the NP prescribed doxycycline 100 mg orally twice daily for 60 days.

J.P. was scheduled to return to the office following completion of treatment, or sooner for any worsening symptoms. Upon return for recheck, J.P. denied any symptom and stated that she felt much better.

Risk Continues

Tickborne diseases often occur in the United States and are typically identified in the spring and summer months. Ticks can be carried on several types of mammals, including, dogs, deer, mice and humans. For the tick to spread infection to humans, it must first have a blood meal from an infected host.

Simple methods can be used to prevent tickborne illness. Wearing appropriate clothing when participating in outdoor activities, particularly in the spring and summer months, is a primary method of prevention. Others are checking pets for ticks and wearing DEET-containing insect repellant. Not all types of tickborne illness lead to the development of a rash, which is why these methods are so important. Without exterior evidence, tickborne illness can go undetected for long periods. Despite prevention methods and screening, these infections have been present in humans for many years and are still being spread.

References

1. Kenneley I. My Bugaboo: Lyme disease-Can you hit the bullseye? Prevention Strategist. 2014;Summer:33-37.
2. Heyman D. Control of Communicable Disease Manual. 18th ed. American Public Health Association; 2004.
3. Centers for Disease Control and Prevention. Tickborne Diseases of the United States A Reference Manual for Health Care Providers. 2nd Edition, 2014.
4. Kotton C. Zoonoses in solid-organ and hematopoietic stem cell transplant recipients. Clin Infect Dis. 2007;44:857-866.
5. Centers for Disease Control and Prevention. Lyme disease two-tiered testing decision tree. http://www.cdc.gov/lyme/healthcare/clinician_twotier.html.
6. Parola P, et al. Ticks and tickborne bacterial diseases in humans: an emerging infectious threat. Clinical Infectious Diseases. 2001;32:897-928.
7. Baron E, et al. A guide to utilization of the microbiology laboratory for diagnosis of infectious diseases: 2013 recommendations by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology. Clin Infect Dis. 2013;57(4):e22-121.
8. Leiby D. Transfusion-transmitted babesia spp.: bull's-eye on babesia microti. Clin Microbiol Rev. 2011;24(1):14-28.
9. Lux J, et al. Tranfusion-associated babesiosis after heart transplant. Emerg Infect Dis. 2003;9(1):116-119.

Kelly Romano is the director of infection control and patients safety at Einstein Medical Center Montgomery in East Norriton, Pa. She has completed a disclosure statement and reports no relationships related to this article.





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