Transfusion-TransmittedBabesiaspp.: Bull's-Eye onBabesia microti

Abstract

SUMMARY Babesia spp. are intraerythrocytic protozoan parasites of animals and humans that cause babesiosis, a zoonotic disease transmitted primarily by tick vectors. Although a variety of species or types of Babesia have been described in the literature as causing infection in humans, the rodent parasite Babesia microti has emerged as the focal point of human disease, especially in the United States. Not only has B. microti become established as a public health concern, this agent is increasingly being transmitted by blood transfusion: estimates suggest that between 70 and 100 cases of transfusion-transmitted Babesia (TTB) have occurred over the last 30 years. A recent upsurge in TTB cases attributable to B. microti , coupled with at least 12 fatalities in transfusion recipients diagnosed with babesiosis, has elevated TTB to a key policy issue in transfusion medicine. Despite clarity on a need to mitigate transmission risk, few options are currently available to prevent the transmission of B. microti by blood transfusion. Future mitigation efforts may stress serological screening of blood donors in regionalized areas of endemicity, with adjunct nucleic acid testing during the summer months, when acute infections are prevalent. However, several hurdles remain, including the absence of a licensed blood screening assay and a thorough cost-benefit analysis of proposed interventions. Despite current obstacles, continued discussion of TTB without proactive intervention is no longer a viable alternative.

Macrophages Are Critical for Cross-Protective Immunity Conferred by Babesia microti against Babesia rodhaini Infection in Mice

“…Most of the human cases are either from tainted blood transfusions or from bites of infected Ixodes scapularis nymphs, which inject sporozoites into the bloodstream of the host during their feeding. The infection is often asymptomatic in healthy humans but can occasionally be fatal in immunocompromised individuals (27,36,37).…”

The Brief Case: Probable Transfusion-Transmitted Babesiosis in a Transplant Recipient

“…Infections due to all other species of Babesia are extremely rare; there have been a few cases of Babesia duncani and B. duncani-like species reported in the Pacific coastal region and three cases of a Babesia divergens-like species, two in the midwestern United States, and one in Washington State (1). Outside of the United States, cases of babesiosis due to any species (including B. microti) are infrequent, with several dozen cases of B. divergens reported throughout Europe and similar numbers of cases of Babesia venatorum reported in China (1,2).…”

“…There are at least 7 species of Babesia described to cause human diseases found throughout the world; however, the phylogeny is still in flux, and new species are likely to be defined (1). In the United States, B. microti is by far the dominant species associated with human infections (2). Infections due to all other species of Babesia are extremely rare; there have been a few cases of Babesia duncani and B. duncani-like species reported in the Pacific coastal region and three cases of a Babesia divergens-like species, two in the midwestern United States, and one in Washington State (1).…”

“…Transfusion-transmitted babesiosis (TTB) is a well-described phenomenon that has increased in frequency over the last 2 decades (2,5). While babesiosis is the leading cause of transfusiontransmitted infection and transfusion-transmitted infection-related death (2), it is not currently screened for by laboratory testing of the U.S. blood supply.…”

“…As an alternative to screening, universal pathogen reduction technologies, such as induced nucleic acid damage, have shown promise by inactivating Babesia species in blood products. These methods have yet to receive FDA approval for whole blood but have recently been approved for plasma and platelet treatment (2).…”