Tick-Borne Infections: Beware the Tortoises Among Us

Abstract

Worldwide vector-borne agents of disease continue to emerge and play ever-increasing roles as threats to blood safety likely influenced by several factors including climate and weather, changing ecosystems, human behavior, economic development, and changes in land use. While mosquito-borne agents garner most of the attention, tick-borne agents are rising in prominence, particularly with respect to blood safety risk. Most disease outbreaks associated with mosquito-borne agents of concern are ephemeral in nature and quickly transition to naive populations in new geographic locations. In contrast, tick-borne agents are generally zoonotic in nature, remaining entrenched where first identified, spreading slowly from the areas of initial establishment to new geographic regions. Tick-borne and mosquito-borne agents are thus analogous to Aesop’s Tortoise and the Hare, respectively. Hence, this chapter will focus on those tick-borne agents or “tortoises,” which in their steady plodding fashion pose expanding and ongoing threats to blood safety. Specifically, three emerging members of the deer or black-legged tick (Ixodes scapularis) “guild” will be at the core of this discussion: Anaplasma phagocytophilum which has been implicated in an increasing number of transfusion cases, the newly described Borrelia miyamotoi whose survival in blood products and transmission by blood transfusion in animal models has been documented, and the lesser known Powassan virus, unusual in that it is a tick-borne flavivirus, a group of viruses that have been transmitted by blood transfusion.