The Global Emergence of Human Babesiosis

Abstract

Babesiosis is an emerging tick-borne disease caused by intraerythrocytic protozoa that are primarily transmitted by hard-bodied (Ixodid) ticks and rarely through blood transfusion, perinatally, and organ transplantation. More than 100 Babesia species infect a wide spectrum of wild and domestic animals worldwide and six have been identified as human pathogens. Babesia microti is the predominant species that infects humans, is found throughout the world, and causes endemic disease in the United States and China. Babesia venatorum and Babesia crassa-like agent also cause endemic disease in China. Babesia divergens is the predominant species in Europe where fulminant cases have been reported sporadically. The number of B. microti infections has been increasing globally in recent decades. In the United States, more than 2000 cases are reported each year, although the actual number is thought to be much higher. In this review of the epidemiology of human babesiosis, we discuss epidemiologic tools used to monitor disease location and frequency; demographics and modes of transmission; the location of human babesiosis; the causative Babesia species in the Americas, Europe, Asia, Africa, and Australia; the primary clinical characteristics associated with each of these infections; and the increasing global health burden of this disease.

Babesia and Theileria Identification in Adult Ixodid Ticks from Tapada Nature Reserve, Portugal

“…Babesia microti, which is also potentially zoonotic, particularly in the USA [20], is distinct from the Babesia s.s. group and consists of a species complex divided into five distinct clades, infecting a wide range of vertebrates with the notable exception of ungulates [21]. Those in clade 1, also referred to as B. microti sensu stricto (s.s.), cause most of the human babesiosis cases worldwide, and those in clade 3 include the B. microti Munich strain, which has an ambiguous zoonotic status [21].…”

Call for Caution to Consider Babesia bovis and Babesia bigemina as Anthropozoonotic Agents in Colombia. Comment on Kumar et al. The Global Emergence of Human Babesiosis. Pathogens 2021, 10, 1447

“…We have read with great interest the review by Kumar et al, "The Global Emergence of Human Babesiosis", published in Pathogens, in which several aspects on the epidemiology of this tick-borne disease are addressed, including the geographic distribution of reported cases and related Babesia species [1].…”

“…In Table 2 of their review, Kumar et al mention the causative agents of human babesiosis throughout the world, designating Babesia bovis and Babesia bigemina as associated with human cases in Colombia, South America [1]. Nevertheless, in the Table's footnote and "Human babesiosis in the Americas" subheading, they highlight that "some causative agents have not been confirmed in larger case series so are not yet accepted as established causes of human babesiosis" and "human babesiosis due to B. bovis and B. bigemina had not previously been described", respectively.…”

“…Currently, among the more than the 100 Babesia spp. identified in wild and domestic animals worldwide, six species (Babesia microti, Babesia divergens, Babesia duncani, Babesia venatorum, Babesia motasi, and Babesia crassa-like pathogen) and two genetic variants (Babesia divergens-like and Babesia microti-like) have been confirmed as human pathogens [1,4]. Related vectors are anthropophilic ixodid ticks from the temperate regions of the northern hemisphere, in the Ixodes ricinus complex (Ixodes persulcatus, Ixodes ricinus, Ixodes scapularis), as well as Dermacentor albipictus and Ixodes ovatus [1,4].…”

“…identified in wild and domestic animals worldwide, six species (Babesia microti, Babesia divergens, Babesia duncani, Babesia venatorum, Babesia motasi, and Babesia crassa-like pathogen) and two genetic variants (Babesia divergens-like and Babesia microti-like) have been confirmed as human pathogens [1,4]. Related vectors are anthropophilic ixodid ticks from the temperate regions of the northern hemisphere, in the Ixodes ricinus complex (Ixodes persulcatus, Ixodes ricinus, Ixodes scapularis), as well as Dermacentor albipictus and Ixodes ovatus [1,4]. In contrast, B. bovis and B. bigemina are causative agents of bovine babesiosis, which affect cattle and buffaloes, causing severe disease of considerable economic impact due to loss of meat production and death of infected animals [5].…”