Babesia blood supply safety is one of the most overlooked public health issues in tick-borne disease. While most people associate Babesia with tick bites, this malaria-like parasite can also spread through blood transfusions, blood donations, and even from mother to child during pregnancy. Over 200 cases of transfusion-transmitted babesiosis have been reported in the United States — making Babesia the highest-ranked parasite transmitted through the blood supply.
This page covers everything patients and providers need to know about how Babesia enters the blood supply, why screening falls short, and what the research tells us about protecting vulnerable populations.
How Babesia Enters the Blood Supply
Unlike Lyme disease, which has never been confirmed to spread through blood transfusions, Babesia can survive in stored blood products — red blood cells, platelets, and fresh frozen plasma. When an infected person donates blood, the parasite can be passed to the recipient.
Many donors have no idea they carry the infection. Babesia can persist in the bloodstream for months without causing obvious symptoms, which means asymptomatic carriers can unknowingly donate infected blood.
An FDA public workshop confirmed that Babesia is now the most significant transfusion-transmitted parasitic infection in the United States — ahead of malaria, which has largely been controlled through donor screening.
Transfusion-Transmitted Babesiosis
Transfusion-transmitted babesiosis occurs when a blood recipient receives a unit contaminated with Babesia microti. The consequences can be severe — especially for patients who are already immunocompromised, elderly, or receiving blood for chronic conditions.
In one case, a single unit of blood changed everything for a 30-year-old man with sickle cell disease. A donor lookback investigation traced the infection to one of seven unscreened units — from a donor in a state not required to test for Babesia.
Cases have also been reported in non-endemic states like Maryland, South Carolina, and Nebraska — challenging the assumption that Babesia is only a regional problem.
Babesia Blood Supply Risk to Newborns
Premature infants are among the most vulnerable populations. In a case reported by Yale School of Medicine, three premature infants in one NICU contracted Babesia from a single 24-year-old blood donor. The donor passed all FDA-mandated screening tests — yet carried the parasite.
Two of the infants developed dangerously high parasitemia levels. One relapsed 48 days after completing treatment, suggesting that even extended therapy may not fully clear the infection in some cases.
The case highlights a critical gap: current screening questionnaires are insufficient, and the babesia blood supply threat to neonatal patients demands better solutions.
Congenital Transmission: Mother to Child
Babesia doesn’t only enter a baby’s bloodstream through transfusion. It can also pass from mother to child during pregnancy.
Two mothers unknowingly transmitted Babesia to their babies during pregnancy — cases that underscore how this parasite can silently affect the most vulnerable patients.
Additional case reports document congenital babesiosis in:
- A 5-week-old twin diagnosed after symptoms initially attributed to prematurity
- Two additional case reports that demonstrate the diagnostic challenges of neonatal babesiosis
These cases reinforce why clinicians should maintain a high index of suspicion for Babesia in newborns who have received transfusions or whose mothers had tick exposure during pregnancy.
Why Donor Screening Falls Short
Current blood donor screening relies heavily on questionnaires that ask about tick bites and travel history. But research presented at the FDA workshop on babesia blood supply safety found that donor responses about tick bites and history of babesiosis had no correlation to actual infection.
Key challenges include:
- Many infected donors are completely asymptomatic
- Babesia is not screened for in all states — only those considered “endemic”
- A single infected donor can affect multiple recipients
- Parasites can persist in stored blood for the duration of the product’s shelf life
By comparison, malaria — once a major transfusion risk — has been reduced to fewer than 1 case per year since 2000 through improved screening. Babesia has not yet benefited from the same level of intervention.
Babesia vs. Lyme Disease in the Blood Supply
Patients often ask whether Lyme disease can spread through blood transfusion. Although Borrelia burgdorferi can survive in stored blood products, there have been no confirmed cases of Lyme disease transmitted through transfusion. The bacteria are present in low concentrations in the blood, making transmission unlikely.
Babesia microti, by contrast, has moderate to high concentrations in red blood cells — which is precisely why it survives the donation and storage process and remains infectious to recipients.
This difference explains why Babesia — not Lyme — is the dominant transfusion-transmitted tick-borne infection.
What Needs to Change
The growing number of transfusion-transmitted babesiosis cases demands action. Based on the available evidence, several changes could improve babesia blood supply safety:
- Universal Babesia screening for blood donors — not just in endemic states
- Molecular testing (PCR) in addition to antibody-based screening
- Greater awareness among clinicians caring for transfusion-dependent patients
- Higher suspicion for Babesia in patients who develop fevers after receiving blood — especially in non-endemic areas
Until screening catches up with the science, patients and providers should be aware that Babesia can travel through the blood bank — not just through the woods.
Frequently Asked Questions
Can you get Babesia from a blood transfusion?
Yes. Over 200 cases of transfusion-transmitted babesiosis have been reported in the United States. Babesia is currently the highest-ranked parasite transmitted through blood transfusions.
Is Lyme disease transmitted through blood transfusions?
No. Although Borrelia burgdorferi can survive in stored blood products, there have been no confirmed cases of Lyme disease transmitted through the blood supply.
Does donor screening prevent Babesia transmission?
Not reliably. Studies show that questionnaire-based screening does not correlate with actual infection. More advanced molecular testing is needed, and not all states require Babesia screening.
Can a mother pass Babesia to her baby?
Yes. Congenital transmission of Babesia has been documented in multiple case reports. Pregnant women with tick exposure should be evaluated for Babesia.
Who is most at risk from transfusion-transmitted Babesia?
Immunocompromised patients, the elderly, premature infants, patients without a spleen, and those requiring chronic transfusions (such as sickle cell disease patients) face the highest risk.
