A Public Health Alerts report published today describes 11 cases of infection with Babesia, a genus of parasites transmitted by Ixodes ticks, in Nova Scotia since 2023, seven of which were confirmed last year.

The paper also notes a potential detection—though not a confirmation—of Babesia among almost 11,000 blood samples from donors in the province.

Public Health Alerts, a collaboration between NEJM Evidence and CIDRAP, fills a gap in reliable data, offering expert-reviewed reports that translate frontline observations into actionable public health evidence. An NEJM Evidence editorial explains the initiative further. Read all Public Health Alerts reports here.

Babesiosis (infection with Babesia) became a reportable disease in Nova Scotia on May 23, 2023, along with implementation of a case definition. Since that time, two infections were confirmed in 2023, two in 2024, and seven in 2025. The 2025 infection rate was 0.6 cases per 100,000 population.

Nine cases were reported in the province’s Western Zone, and one each in the Northern and Central Zones. Seven patients were female, and seven were adults 70 or older.

Three people tested positive for other tick-borne diseases. One of them also had Lyme dis­ease, one had a simultaneous anaplasmosis infec­tion, and one had a previous and current Lyme disease infection.

Officials were not able to complete public health investigations for three retrospectively reported cases. Eight cases with available information, all in the Western Zone, were locally acquired, indicating the patients had not recently traveled to a Babesia-endemic area. None of the patients reported donating or receiving blood, and all had docu­mented signs and symptoms consistent with babesiosis.

Only three of the eight patients with complete information reported a tick bite before they had symptoms.

Nova Scotia case rates and rates of babesia [test] reactivity in blood donors are lower than rates in New Hampshire, Maine, and Vermont.

One of 10,976 collection tubes of donor blood resulted in a reactive nucleic acid test (NAT), with the authors noting that “two of three repeats were weakly reactive.” 

A Canadian Blood Services Medical Officer interviewed the blood donor who had the reactive Babesia NAT result. The person, who lived in the Western Zone, reported extensive outdoor activities, a Lyme disease diagnosis in the two months before donating blood, and several months of feeling generally unwell.

Confirmatory tests, however, came back negative.

The authors conclude, “This report provides evidence of local transmission of human babesiosis in Nova Scotia, consistent with recog­nized changes in ixodes tick distribution and climate and ecosystems.”

They add, “Nova Scotia case rates and rates of babesia NAT reactivity in blood donors are lower than rates in New Hampshire, Maine, and Vermont, where babesia NAT screening is mandated by the Food and Drug Administration for blood components that cannot be treated for the pathogen (e.g., whole blood, red blood cells).”