Human Babesiosis Caused by Babesia duncani Has Widespread Distribution across Canada.

John Scott,Catherine Scott

doi:10.3390/healthcare6020049

Abstract

Human babesiosis caused by Babesia duncani is an emerging infectious disease in Canada. This malaria-like illness is brought about by a protozoan parasite infecting red blood cells. Currently, controversy surrounds which tick species are vectors of B. duncani. Since the availability of a serological or molecular test in Canada for B. duncani has been limited, we conducted a seven-year surveillance study (2011–2017) to ascertain the occurrence and geographic distribution of B. duncani infection country-wide. Surveillance case data for human B. duncani infections were collected by contacting physicians and naturopathic physicians in the United States and Canada who specialize in tick-borne diseases. During the seven-year period, 1119 cases were identified. The presence of B. duncani infections was widespread across Canada, with the highest occurrence in the Pacific coast region. Patients with human babesiosis may be asymptomatic, but as this parasitemia progresses, symptoms range from mild to fatal. Donors of blood, plasma, living tissues, and organs may unknowingly be infected with this piroplasm and are contributing to the spread of this zoonosis. Our data show that greater awareness of human babesiosis is needed in Canada, and the imminent threat to the security of the Canadian blood supply warrants further investigation. Based on our epidemiological findings, human babesiosis should be a nationally notifiable disease in Canada. Whenever a patient has a tick bite, health practitioners must watch for B. duncani infections, and include human babesiosis in their differential diagnosis.

Highlights

Human babesiosis, a zoonosis, is an infectious disease caused by intraerythrocytic protozoan parasites of the genus Babesia [1]
89% of these Canadian patients were diagnosed in United States, while 11% were diagnosed in Canada
Based on the fact that other Ixodes ticks in other zoogeographic regions in the northern hemisphere transmit Babesia species to humans, we suggest that B. duncani can be transmitted to humans in North America via a tick bite (Figure 1)

Summary

Introduction

A zoonosis, is an infectious disease caused by intraerythrocytic protozoan parasites of the genus Babesia [1]. These microscopic malaria-like organisms (1−3 μm) invade human erythrocytes and lyse them, causing a febrile hemolytic anemia [2]. In the continental United States and Canada, Babesia duncani and Babesia microti (Apicomplexa: Babesiidae) are commonly recognized and identified in humans. These apicomplexan piroplasms are morphologically similar but are genetically different [3]. Babesia has four life stages, namely sporozoite, trophozoite, merozoite, and gamete

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