Expanding Geographic Range Increases Importance of Testing
Updated: July 2014
Published: June 2013
Tick-borne diseases occur worldwide, including both temperate and tropical climates. In the United States, major tick-borne diseases include Lyme disease, anaplasmosis, babesiosis, ehrlichiosis, and Rocky Mountain spotted fever.
Historically, only certain pockets of the United States posed a risk for tick-borne disease. However, the geographic range of ticks has expanded and large areas of the population are now at risk. Because of this increased risk, it is important that physicians recognize who to test, when to test, and what test to use.
Lyme disease is the most common tick-borne illness in North America and is caused by the bacterium Borrelia burgdorferi. Patients treated with appropriate antibiotics in the early stages of the disease are likely to recover completely. In later stages, response to treatment may be slower, but the majority of patients with Lyme disease recover completely with appropriate treatment.
Infection Acquired from: Blacklegged or deer tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus).
Geographic Prevalence: Lyme disease is most prevalent in the northeastern, mid-Atlantic, northcentral and Pacific Coast of the United States.
Symptoms: Fever, headache, fatigue, and a characteristic bull’s-eye pattern skin rash called erythema migrans. If left untreated, infection can spread to joints, the heart, and the nervous system.
Babesiosis is caused by the protozoan parasite Babesia microti. Most cases of babesiosis are probably subclinical or mild, but the infection can be severe and life threatening, especially in older or asplenic patients.
Infection Acquired From: Blacklegged or deer tick (Ixodes scapularis).
Geographic Prevalence: Babesiosis is most prevalent in the northeastern, Upper Midwest, and Pacific Coast of the United States.
Symptoms: Most Commonly: Fever, fatigue, malaise, headache, and other flu-like symptoms. Patients may have hepatomegaly and splenomegaly. In severe cases: hemolysis, acute respiratory distress syndrome, and shock.
Human granulocytic anaplasmosis (HA) is caused by the tick-borne bacterium, Anaplasma phagocytophilum. Anaplasmosis can be a serious illness that can be fatal if not treated correctly, even in previously healthy people.
Infection Acquired from: Blacklegged or deer tick (Ixodes scapularis) and the western black-legged tick (Ixodes pacificus).
Geographic Prevalence: HA is most prevalent in the Upper Midwest and in other areas of the United States that are endemic for Lyme disease.
Symptoms: Fever, headache, muscle pain, malaise, chills, nausea and abdominal pain, cough, confusion.
Ehrlichiosis in the U.S. is caused primarily by Ehrlichia chaffeensis, but E. ewingii and Ehrlichia sp. Wisconsin (E. muris-like) are also known to cause infection in humans. Most cases of ehrlichiosis are probably subclinical or mild, but the infection can be severe and life-threatening in some individuals.
Infection Acquired from: Lone Star tick (Amblyomma americanum) (for E. chaffeensis and E. ewingii).
Geographic Prevalence: Ehrlichiosis is most prevalent in the southeastern, and southcentral regions of the United States.
Symptoms: Fever, fatigue, malaise, headache, and other “flu-like” symptoms, including myalgias, arthralgias, and nausea. Central nervous system involvement can result in seizures and coma.
In addition to Rickettsia rickettsii, the agent of Rocky Mountain spotted fever (RMSF), several other tick-borne species of Rickettsia, broadly grouped under the heading “Spotted Fever group Rickettsia (SFGR)” have been shown to cause human infections. Tick-borne SFGR may cause similar signs and symptoms to those observed for RMSF and can potentially be fatal in humans.
Infection Acquired from: American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (Dermacentor andersoni), and brown dog tick (Rhipicephalus sanguineus).
Geographic Prevalence: RMSF is most prevalent in the southeastern United States.
Symptoms: High fever, chills, severe headache, muscle aches, nausea and vomiting, and fatigue.
*Disease information and geographic distribution data available at www.cdc.gov. Retrieved 6/3/2013