Babesia Screening

Description

B. microti has resulted in 0-2 deaths annually reported to the FDA since FY 2012. Babesiosis has been nationally reportable since 2011. Incidence of babesiosis and TTB has increased. Hundreds of cases of TTB have been reported (1%–2% of babesia cases in New York State are TTB cases). TTB has occurred after administration of RBC-containing blood products, primarily RBCs since whole blood-derived platelets contain minimal red cells. Some blood centers in high-risk, endemic areas began screening whole blood and RBC donors for B. microti.

Infection

Babesiosis is caused by intraerythrocytic protozoan parasites, usually B. microti , via deer tick, Ixodes scapularis. B. microti is endemic to the northeast and upper midwest of the United States, and its geography is expanding. The first case of babesiosis in humans was identified in 1957 in Croatia, in an asplenic farmer who had grazed his cattle in tick-infested pastures. He presented with fever, anemia, and hemoglobinuria and expired owing to renal failure. The agent was either Babesia bovis or Babesia divergens , both pathogens of cattle. Other species causing babesiosis in humans include Babesia duncani (WA1) reported in the north Pacific coast, B. divergens –like (MO1) organisms from Missouri, Babesia odocoilei (EU1) a species seen in Europe, Babesia venatorum in China, TW1 in Taiwan, and KO1 in Korea. Originally a disease identified in Europe, babesiosis has since been reported globally.

Patients with babesiosis may experience no symptoms, mild to moderate flulike symptoms, or severe symptoms leading to death; symptoms typically occur within 6 weeks. Severe disease is more likely in people who are immunosuppressed including patients with malignancies, asplenia, and HIV infection. Asymptomatic infections contribute to the variance between seroprevalence and the number of reported cases. On Block Island, RI, 19% (13 of 67) of infected adults and 40% (4 of 10) of the infected children were asymptomatic. B. microti immunofluorescence antibody (IFA) titers were ≥1:64. When symptomatic, babesiosis may resolve within months but can last over a year. Treatment is usually a course of antibiotics using atovaquone and azithromycin or clindamycin and quinine; severe parasitemia may require RBC exchange.

The greatest risk of tick infection occurs during warmer months when the ticks are most active. However, TTB occurs year-around, and clinical laboratory testing shows positive results occur year-around.