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ESSENTIALS OF DIAGNOSIS

ESSENTIALS OF DIAGNOSIS

  • Tick bites are typically painless, and <50% of patients with tickborne disease present with a known bite.

  • Consider tickborne diseases (TBDs) in the summer months for patients who present with fever, myalgias, and headaches but without gastrointestinal (GI) or upper respiratory symptoms who live in tick-endemic regions of the United States.

  • Diagnosis can be difficult because of nonspecific symptoms and difficulty in timely confirmatory testing.

  • Treatment with doxycycline should be initiated when Rocky Mountain spotted fever, human granulocytic anaplasmosis, and/or ehrlichiosis is included in the differential diagnosis.

General Considerations

TBDs continue to be on the rise in the United States. Several factors contribute to this surge, including suburban development, climate change, a rise in human outdoor activities, and an increase in vector hosts such as the white-tailed deer. Lyme disease is the most widely known tickborne illness to the public, as well as the most common. During 2000–2010, there were 250,000 reported cases of Lyme disease in the United States, and from 2011–2017, the number of cases surpassed that number. The incidence of reported cases of almost all TBDs have increased over that period of time, as well as the recognition of new illnesses that were not even identified when this chapter was originally written. As of this writing, 14 bacterial, 1 protozoal, and 4 viral TBDs have been identified in the United States. The tickborne illnesses we focus on in this chapter are Lyme disease, Rocky Mountain spotted fever (RMSF), ehrlichiosis, human granulocytic anaplasmosis (HGA), and babesiosis. Numerous other diseases associated with ticks should be considered in certain locations during summer months. For more information regarding these illnesses, visit the following Centers for Disease Control and Prevention (CDC) webpage: http://www.cdc.gov/ticks.

Essential to the diagnosis and treatment of TBD is the geographic distribution of the particular disease and the ticks that transmit them. Lyme disease, RMSF, ehrlichiosis, HGA, and babesiosis are all associated with particular species of ticks. Table 53–1 lists the six tick species of significance for this chapter, including their distribution and primary hosts. However, the patient rarely presents with the actual tick attached, and therefore, visual identification of species is typically unnecessary. Tick bites are typically painless, and <50% of patients with TBD present with a known bite.

Table 53–1.Tick species.

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