Diseases from North America: focus on tick-borne infections

Abstract

Tick-borne infections are seen throughout the United States, with varying geographical locations. Many of these infections are also increasingly seen in Europe. Certain ticks (eg Ixodes) can transmit more than one infection. Diagnosis, particularly in early infection, can be challenging and therefore knowledge of the distinguishing clinical features and epidemiology of these diseases is important. Testing for Lyme disease often causes confusion for patients and medical providers, as serological tests may be negative in early infection and conversely may be positive for years after infection. Newer tests, such as the C6 ELISA, may play a role in Lyme diagnosis. Additionally, the value of a simple blood film should not be underestimated for diagnosing babesiosis and anaplasmosis. In certain situations, empiric therapy may be required for tick-borne infections as severe illness with multiorgan failure can occur, particularly in older and immunocompromised hosts. This review describes the more commonly seen tick-borne infections: Lyme, babesiosis, anaplasmosis and Rocky Mountain Spotted Fever. More recently identified tick-borne infections, such as southern tick-associated rash illness and Borrelia miyamotoi, are also covered.

Keywords: Anaplasma; Babesia; Lyme; Rocky Mountain spotted fever; tick-borne.

Fig 1.

Typical erythema migrans rash. Image obtained from the CDC Public Health Image Library; credit: James Gathany.

Fig 2.

Babesia sp in Giemsa-stained thin blood film demonstrating the tetrad of merozoite forms known as the Maltese cross. Image obtained from CDC-DPDx.

Fig 3.

Ehrlichiosis evidenced by intracytoplasmic inclusions (morulae) on Giemsa-stained blood film. Image obtained from CDC-DPDx.

Fig 4.

Typical Rocky Mountain spotted fever rash. Image obtained from the CDC Public Health Image Library.