The PCR test for Anaplasma phagocytophilum DNA was positive in one of the two RBC units. The donor of the positive unit was asymptomatic, but serological testing on blood obtained two months after donation demonstrated an IgM titer of 1:40 and and an IgG titer of 1:1040 in the donor. The donor was a 53-year-old male who had been hunting in wooded areas one week before donation, but did not recall a tick bite. He had shot and field dressed a rabbit and a deer. He also owned a dog.
Although donors who are symptomatic or have a fever would be prevented from donating blood, asymptomatic donors or those yet to develop symptoms would not be deferred. It has been determined that asking donors about tick bites is not useful because if noticed, the tick would probably be removed before infection was transmitted. If persons who reported tick bites were deferred, it is estimated about 9% of donors in endemic areas would be eliminated. Seroprevalence in Wisconsin is about 14.5%, so many donors would be deferred and PCR is considered to be cost prohibitive for testing donor blood units at this time. Leukocyte reduction should lessen the risk of infections from transfusions, but does not completely eliminate it. The patient in this case recovered, as did the donor.