By Vanessa Pomarico-Denino
Tick borne infections are increasing in number due to the proliferation of the population of ticks and climate change that affects the ecosystem for ticks to thrive. Ticks can continue to live in areas of the country that do not experience a hard frost. Currently, there are over 950 species of ticks worldwide, the most common infections being Lyme, Babesiosis, Erhlichiosis, Anaplasmosis, Rocky Mountain Spotted Fever (RMSF), Colorado tick fever, tickborne relapsing fever and Powassan to name just a few. Ticks are vectors and pathogens are transmitted through the saliva from the bite of an infected tick that can carry more than one type of infection concomitantly.
How do tick bites occur?
Ticks are obligate ectoparasitic arthropods meaning they need to have a suitable host in order to survive. The lifespan of a tick is approximately 2-3 years. They must feed on a blood meal at every stage of their life span with each meal lasting anywhere from 10 minutes to 2 hours before they fall off the host, many times without the host ever knowing they were bitten. This is due to the anesthetic property found in tick saliva. Lone star ticks (Amblyomma americanum) and blacklegged ticks (deer ticks) are the two most common types of ticks. Peak season for tickborne infections is between April and October. The highest rates of infection are during the months of June to August.
It is important to consider those individuals working outdoors who are at higher risk of contracting a tickborne illness: people who work or engage in outdoor activities such a forestry, construction, railroads, wildlife or park management, hikers, outdoor recreationists and those who garden. Ticks also thrive in the tall seagrass, dune vegetation, and shaded trails leading up to the beach.
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How can NPs spot tick-borne infections in clinical practice?
The clinical presentation of tickborne illness is not always straightforward as these infections can mimic symptoms of other infections: fevers, fatigue, headaches, generalized body aches or joint pain. Each tickborne infection has common overlap of symptoms as well as their own unique symptoms. Perhaps the most common symptom of “summer flu” is an indicator of a potential tickborne infection as influenza is not typically seen during the summer months when ticks are more likely to infect humans.
Lyme Disease
Diagnostic testing can be challenging if performed too early for seroconversion, missing the window of opportunity for proper diagnosis. The presence of erythema migrans (EM) or a classic “bullseye” is diagnostic for Lyme infection but approximately 20% of all Lyme infections do not develop a rash. The two-step confirmatory testing is the gold standard for Lyme infection. ELISA testing with reflex to a Western Blot will detect both immunoglobulin M (IgM) and immunoglobulin G (IgG). The IgM Western Blot must have at least 2 out of 3 bands to be diagnostic: 23, 39, and 41kDa. The IgG must have at least 5 out of 10 bands positive for a Lyme disease diagnosis.
Babesiosis, Ehrlichiosis & Anaplasmosis
Peripheral blood smears are the diagnostic test of choice for Babesiosis. Serial peripheral blood smears are used to track decreasing parasitemia counts once treatment has been initiated. The most useful diagnostic test for Ehrlichiosis and Anaplasmosis is the Polymerase Chain Reaction (PCR) assay and is best used during the first week of illness. Antibody titers, the indirect immunofluorescence assay (IFA) can also be used to confirm an infection. These are considered convalescent samples taken 2 to 4 weeks after infection to determine an increase in antibodies. IFA is the gold standard for diagnosis RMSF. Patients with RMSF may present with a non-pruritic rash on the ventral aspects of hands and feet. Patients with RMSF can rapidly decline due to multisystem organ failure if not treated early so it is recommended to treat if there is any index of suspicion.
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Recommended Treatment Guidelines
Treatment is dependent upon the specific tickborne infection. Doxycycline remains the first-line therapy for Lyme, Ehrlichiosis and Anaplasmosis as well as RMSF while Babesiosis is treated with azithromycin and atovaquone. It is important for clinicians to have access to appropriate resources for antimicrobial therapies for specific tickborne illness. For patients who have a tick that has been embedded for at least 36-72 hours, a one-time dose of doxycycline 200 mg is recommended to reduce the risk of developing Lyme infections.
It is essential for NPs to have a strong understanding of tickborne infections especially if patients present to the office or urgent care with “summer flu” symptoms. Recognizing regional epidemiology and early clinical manifestations can lead to reduction of complications from a tick infection. A meticulous H&P is important to determine patient risk and potential exposure to tickborne illnesses.
