By John Gever, Senior Editor, MedPage Today September 06, 2011
MedPage Today Action Points
Note that according to this report, the protozoan parasite Babesia microti, usually transmitted by the bite of an infected deer/black-legged tick and the cause of babesiosis, has become the infectious agent most frequently transmitted by blood transfusion in the U.S.
Point out that 87% of the cases in this study were reported in seven endemic states and as yet there is no approved assay.
Review
Infections with Babesia protozoan parasites -- normally a tickborne disease -- from blood transfusions have escalated recently, suggesting that the blood supply is increasingly at risk for contamination, CDC researchers said.
A total of 159 transfusion-related babesiosis cases from 1979 to 2009 have been confirmed, with more than three-quarters occurring in the last decade, Barbara L. Herwaldt, MD, MPH, at CDC headquarters in Atlanta, and colleagues reported online in Annals of Internal Medicine.
Unfortunately, no high-throughput babesiosis assay is currently available, nor is there any way to kill or filter the parasite in donated blood, leaving transfusion recipients vulnerable at least for the near future, the researchers indicated.
In an accompanying editorial, David A. Leiby, PhD, of the American Red Cross' Holland Laboratory in Rockville, Md., sounded a similarly pessimistic note.
"Several hurdles prevent implementation of an effective strategy," he wrote.
Leiby noted that, in addition to the current lack of an approved blood-screening assay, "manufacturers have shown a reluctance to develop a test for a regionalized agent that may require only a limited number of tests."
Herwaldt and colleagues found that 87% of the cases originated in just seven states where the Babesia organism is most endemic -- Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Wisconsin, and Minnesota.
"Any intervention needs to target these regions first," Leiby suggested. An FDA advisory committee made the same point in 2010, recommending that donor testing be limited to endemic areas at least initially.
In addition to testing, pathogen reduction is another strategy that deserves investigation although no proven technology is ready for use now, Leiby added.
For the current study, Herwaldt and colleagues analyzed data on babesiosis cases confirmed at the CDC's Parasitic Disease Laboratory and/or collected by state and local public health departments, blood collection and distribution services, and published reports.
They counted 162 cases in which the infection appeared to have originated from transfusions rather than tick bites. Three of these involved the B. duncani species whereas B. microti was responsible for the other 159.
Nearly 60% of blood donations identified as the source of infection occurred during summer and early fall, the traditional "season" for babesiosis.
But, as Herwaldt and colleagues pointed out, 41% occurred at other times of the year, with every month showing at least two cases.
And while the vast majority of cases were seen in the seven endemic states, individuals in 12 other states including California, Texas, and Florida, also developed babesiosis from transfusions.
Many of the latter cases involved donors who acquired the infection in endemic areas and then donated blood elsewhere; others appeared to stem from interstate shipment of blood products.
"Our findings underscore the year-round vulnerability of the U.S. blood supply -- especially, but not only, in and near babesiosis-endemic areas," the researchers wrote.
One cluster of cases centered on a man who died following multiple blood transfusions and whose kidneys were harvested for transplant. Although the man was not infected before the day of his death, both kidney recipients subsequently became infected -- apparently because one of the blood units he received came from an infected donor.
Herwaldt and colleagues emphasized that their case count is "undoubtedly" an underestimate because babesiosis often goes undetected and was not subject to mandatory reporting during the study period. (It became a notifiable disease earlier this year.)
Although the disease can be life-threatening, symptoms in otherwise healthy people often are more flu-like and may not even be seen by doctors.
In some of the cases identified in the study, diagnosis was accidental when Babesia protozoa were spotted in blood smears.
Leiby noted that "even severe cases of babesiosis from endemic regions can be misdiagnosed" -- 14 cases in the study were thought at first to be malaria.
However, he was uncertain whether the apparently rising incidence was real. Perhaps "physicians and hospitals are more attuned to potential Babesia infections in blood recipients," he suggested, although it is also possible that the parasite is becoming more widespread.
But that aside, the likelihood that the actual number of transfusion-related babesiosis cases is much higher than 162 should compel attention, Leiby indicated: "The time to act is now.