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Double test cuts odds of getting parasite from blood transfusion
December 7, 2016 / 10:16 PM / 9 months ago

Double test cuts odds of getting parasite from blood transfusion

An experimental test for the parasite that causes babesiosis was able to prevent the disease from infecting people through blood transfusion, according to a new study of nearly 90,000 U.S. blood donors.

Carried by ticks, babesiosis can cause serious malaise and fatigue. In some people, particularly the elderly, it can be fatal as the parasite infects oxygen-carrying red blood cells. Some people experience no symptoms.

Like Lyme disease, it is often spread by deer ticks. It is most prevalent in the Northeast and Midwestern United States and it’s the most common cause of blood infection transmitted by a blood transfusion.

“Not all the cases are terribly symptomatic, but some can be terribly symptomatic,” said Dr. Charles Ericsson, head of clinical infectious diseases at the University of Texas’ McGovern Medical School in Houston, who was not involved in the new study. “This will have an impact on public health policy.”

The combination test, under review by the U.S. Food and Drug Administration and developed by Massachusetts-based Imugen, is designed to put a dent in those odds.

“These results directly tell us screening is feasible and, from the results we generated, screened blood did not appear to be infectious. So the test system we used appeared to be effective in preventing transfusion-transmitted babesia,” coauthor Dr. Susan Stramer, vice president of scientific affairs at the American Red Cross, told Reuters Health.

In 10 counties in Connecticut and Massachusetts, where the disease is relatively common, there were 14 cases of babesiosis among recipients of unscreened blood versus none when screening was done.

The test looked for parasite DNA in red blood cells and for traces of the antibodies that appear when a blood donor has been infected and is fighting off the disease.

The researchers, reporting in the New England Journal of Medicine, also did follow-up tests of the blood on hamsters. When parasite DNA showed up in the blood cells, the hamster tests confirmed that those cells carried a high risk of infection, Ericsson told Reuters Health.

Stramer said the cost of the test is probably about $20 to $25 per unit of blood, although that price might come down if it’s approved and mass-produced. In contrast, testing for the Zika virus costs about $6 to $13 she said. The babesiosis test is currently available to blood banks on an experimental basis, she added.

Of the 89,153 donated samples tested, including from sites in Minnesota and Wisconsin, 335 were positive in some way for the infection.

The test only works for Babesia microti, the species of the parasite that causes most cases of the disease, though another species, Babesia duncani, “was implicated in 3 of 162 cases of transfusion-transmitted babesiosis from 1979 through 2009,” the authors note.

Although babesiosis doesn’t seem to be spreading quickly to other parts of the country, it “is currently an infectious risk to the U.S. blood supply,” Stramer and her colleagues write. “It was responsible for 27 percent of the deaths (4 of 15 deaths) in blood-transfusion recipients that were reported to the FDA from 2010 through 2014.”

They said it might be most cost-effective to limit the test to areas where the disease is endemic.

“It pretty much stays confined to the Northeast and up in Wisconsin,” Ericsson said. “The problem, of course, is that people travel so much. So I don’t think you’d want to limit your blood supply protection.”

Both the Red Cross and Imugen financed the study.

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