2.2.1. Babesia divergens

The first human babesiosis case was caused by B. divergens and it occurred in Croatia (Skrabalo and Deanovic, 1957). Human cases are typically severe, especially in splenectomized individuals. To date, approximately 40 cases have been reported, primarily from France, Ireland, and Great Britain with fewer cases reported from Sweden, Switzerland, Spain, Portugal, and Croatia (Centeno-Lima et al., 2003; Moreno Giménez et al., 2006; Martinot et al., 2011). However, undiagnosed exposures do occur, as a seroprevalence of 13% was detected among Lyme disease patients in Sweden (Uhnoo et al., 1992).

Cattle are the natural host for B. divergens and infections are noted throughout Europe and possibly into North Africa (Tunisia), which corresponds with the distribution of the only known vector, Ixodes ricinus (Zintl et al., 2003). Although cattle are the principal host, infections may have been detected in farmed reindeer (Rangifer tarandus) in the United Kingdom; however, these infections may have been caused by Babesia capreoli (Malandrin et al., 2010). Extensive molecular or biological characterizations of ‘‘ B. divergens ’’ samples from cervids have revealed that they are distinct and likely are B. capreoli (Adam et al., 1976; Schmid et al., 2008; Bastian et al., 2012). In addition, B. capreoli, unlike B. divergens, lacks infectivity for gerbils and splenectomized cattle (Malandrin et al., 2010). Additional studies are needed to confirm the ability of B. divergens to utilize cervids (non-splenectomized) as reservoirs (Zintl et al., 2011).

Experimental B. divergens infections have been established in a variety of splenectomized animals including chimpanzees (Pan troglodytes), rhesus macaque (Macaca mulatta), laboratory rats, roe deer (Capreolus capreolus), fallow deer, red deer (Cervus elaphus), European mouflon (Ovis orientalis musimon), and domestic sheep (Malandrin et al., 2010).

Babesia divergens shares the same vector as B. capreoli and two other zoonotic Babesia in Europe (B. sp. EU1 and B. microti). Infections have been reported in I. ricinus from Hungary, Austria, Belgium, Netherlands, Switzerland, Germany, Norway, and Estonia (Blaschitz et al., 2008; Wielinga et al., 2009; Schorn et al., 2011; Egyed et al., 2012 Lempereur et al., 2012; Oines et al., 2012). Importantly, surveys of ticks utilizing highly conserved or short regions of the 18S rRNA gene may lead to misidentification of B. capreoli and other B. divergens -like sp. as B. divergens. Transovarial transmission by I. ricinus has been documented (Bonnet et al., 2007a).