Emerging tick-borne pathogens of public health importance: a mini-review

Abstract

Ticks are the most important vectors of human pathogens, leading to increased public health burdens worldwide. Tick-borne pathogens include viruses (e.g. tick-borne encephalitis and Powassan); bacteria, such as the causative agents of Lyme disease, spotted fever rickettsiosis and human anaplasmosis; and malaria-like protozoan parasites causing babesiosis. Tick-borne diseases are emerging due to the geographical expansion of their tick vectors, especially in the northern hemisphere. Two examples of this phenomenon are Ixodes scapularis and Amblyomma americanum, which have expanded their ranges in the USA in recent decades and are responsible for the continuous emergence of Lyme disease and human ehrlichiosis, respectively. This phenomenon is also occurring worldwide and is reflected by the increasing number of tick-borne encephalitis and haemorrhagic fever cases in Europe and Asia. In this review, we provide a concise synopsis of the most medically important tick-borne pathogen worldwide, with a particular emphasis on emerging public health threats.

Keywords: Haemaphysalis longicornis; Ixodes; Lyme disease; arboviruses; tick-borne diseases.

Fig. 1.

Geographical distribution of selected tick-borne pathogens and diseases. All geographical boundaries are generalized and approximate. Abbreviations and descriptions are shown in Table 1. For some pathogens (Heartland virus, Thogoto virus, B. divergens, Ca. N. mikurensis), only country or state-level data were available. Only partial ranges are shown for some worldwide diseases and conditions – TBRF (tick-borne relapsing fever) in northwestern Africa, tick paralysis in Australia. Modified from previously published records and maps [29, 37, 44, 51, 53, 64, 66, 72, 83, 94, 105, 149–155]