A 28-year-old male with no significant past medical history presents to the ED with fatigue and palpitations. He notes recovering from a flu-like illness with a rash several weeks ago. On exam, he has the rash shown which he reports has been improving. EKG is significant for an AV nodal block. What is the most likely vector for this infection?

A. Dermacentor variabilis
B. Lone star tick
C. Ixodes scapularis
D. Mosquito

C) Ixodes scapularis is correct

A. Incorrect: Dermacentor variabilis
Dermacentor variabilis is the vector of Rickettsia rickettsi which causes Rocky Mountain spotted fever.

B. Incorrect: Lone star tick
The lone star tick is the vector responsible for STARI, southern tick associated rash illness. STARI presents similarly to Lyme disease in the early phases with annular erythematous rash and central clearing in addition to flu-like illness; however, later manifestations of disease such as cardiac disease are not characteristic of this disease.

C. Correct: Ixodes scapularis
Lyme disease is the most common tickborne illness in the United States. It is caused by the organism Borrellia burgdorfori and is transmitted by the Ixodes tick. While classically known for affecting the northeastern part of the country, northwest California, and the Great Lakes are high risk areas as well. Clinical manifestations of this disease are characterized by three stages: early acute infection symptoms such as erythema migrans and flu-like illness with myalgias and arthralgias; early disseminated disease within days to weeks characterized by neurologic and cardiac manifestations; late disseminated disease characterized by joint swelling and pain as well as neurologic symptoms. Treatment is typically with doxycycline or amoxicillin.
Source: Bratton RL, Whiteside JW, Hovan MJ, Engle RL, Edwards FD. Diagnosis and treatment of Lyme disease. Mayo Clin Proc. 2008;83(5):566-71.
PMID 184526888

D. Incorrect: Mosquito
The mosquito is a vector responsible for many illnesses. This patient is showing signs of Lyme disease however, which is not transmitted by mosquitos.

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