Infectious Disease · Medical Literature
Emergence of Babesiosis in Nova Scotia, Canada.
Abstract
AbstractAs part of a multi-year surveillance program of tick-borne diseases, we describe babesia surveillance of blood donors using nucleic acid tests conducted in 2025 and summarize cases of babesiosis reported by public health officials in Nova Scotia, Canada, from 2023 through 2025. Among 10,976 blood donor specimens, one specimen, collected from a blood donor in Nova Scotia Health's Western Zone, was positive, although this result was unable to be confirmed. Since babesiosis became reportable in Nova Scotia on May 23, 2023, eleven clinical cases have been documented, including eight in individuals who resided in the Western Zone and had no recent history of travel.
Clinical relevance
This surveillance report documents the emergence of Babesia transmission in Nova Scotia, Canada, representing a northward geographic expansion of babesiosis beyond its historically endemic regions in the northeastern United States. The identification of autochthonous cases in immunocompromised, elderly, or asplenic patients in this newly endemic zone carries significant morbidity and mortality risk if unrecognized. Clinicians practicing in Atlantic Canada and those evaluating febrile illness or unexplained hemolytic anemia in travelers from the region should now include babesiosis in the differential diagnosis.
Key findings
1. Among 10,976 blood donor specimens screened via nucleic acid testing (NAT) as part of a multi-year tick-borne disease surveillance program in Nova Scotia in 2025, one specimen tested positive for Babesia, though confirmatory testing was unsuccessful. 2. The seropositive donor specimen originated from Nova Scotia Health's Western Zone, geographically concentrating the transmission risk signal within that sub-region. 3. Since babesiosis became a provincially reportable disease on May 23, 2023, eleven clinical cases have been documented over approximately two years (2023–2025). 4. Eight of the eleven clinical cases (approximately 73%) resided in the Western Zone, suggesting a focal, geographically circumscribed area of enzootic transmission. 5. Eight cases had no recent history of travel outside the region, confirming locally acquired (autochthonous) transmission rather than importation. 6. Specific effect sizes, confidence intervals, p-values, and NNT/NNH were not reported in the abstract; quantitative epidemiologic parameters await full publication.
Practice implications
Clinicians in Nova Scotia — particularly those in the Western Zone — should include Babesia microti in the differential for any febrile hemolytic illness during tick season, ordering thick and thin peripheral blood smears and Babesia-specific PCR, especially in asplenic, immunocompromised, or elderly patients who are at highest risk for severe disease. Blood banking and transfusion medicine services in Atlantic Canada should be aware of the confirmed NAT signal in local donors and consider the evolving risk of transfusion-transmitted babesiosis when evaluating post-transfusion fever workups. Public health reporting infrastructure is now in place (mandatory reportability since May 2023), and clinicians should ensure all confirmed or suspected cases are reported to facilitate ongoing surveillance and refine the geographic risk map.