Babesia and the Blood Supply: What Patients Need to Know

Babesia can spread through blood transfusions
Asymptomatic donors may unknowingly transmit infection
Vulnerable patients face the greatest risk

Babesia and blood supply safety remain underrecognized public health concerns. While most people associate Babesia with tick bites, this malaria-like parasite can also spread through blood transfusions, blood donations, and from mother to child during pregnancy.

More than 200 cases of transfusion-transmitted babesiosis have been reported in the United States, making Babesia the leading parasitic infection transmitted through the blood supply.

This page explains how Babesia enters the blood supply, where screening may fall short, and why vulnerable patients remain at risk.

How Babesia Enters the Blood Supply

Unlike Lyme disease, which has not been confirmed to spread through blood transfusion, Babesia and Lyme disease can survive in stored blood products including red blood cells, platelets, and plasma.

When an infected person donates blood, the parasite may be transmitted to the recipient.

Many infected donors have no symptoms. Asymptomatic carriers may unknowingly donate contaminated blood.

An FDA public workshop confirmed that Babesia is now the most significant transfusion-transmitted parasitic infection in the United States.

Transfusion-Transmitted Babesiosis

Transfusion-transmitted babesiosis occurs when a patient receives blood contaminated with Babesia microti.

The consequences may be severe, especially for:

• Immunocompromised patients
• Elderly individuals
• Patients requiring chronic transfusions
• Premature infants

In one report, a single unit of blood changed everything for a patient with sickle cell disease.

Cases have also been reported in non-endemic states, demonstrating that transfusion-related Babesia is not limited to traditional geographic regions.

Babesia Blood Supply Risk to Newborns

Premature infants are among the most vulnerable populations.

In one report, three premature infants in one NICU contracted Babesia from a single donor who passed standard screening.

Two infants developed high parasitemia, and one relapsed after treatment.

This case highlights the limitations of current screening methods and the potential consequences of undetected infection.

Congenital Transmission: Mother to Child

Babesia may also be transmitted during pregnancy.

Cases of mother-to-child transmission demonstrate that newborns may become infected even without direct tick exposure.

Additional neonatal reports include:

• A 5-week-old twin with congenital Babesia
• Additional congenital Babesia case reports

Why Donor Screening Falls Short

Current screening often relies on questionnaires regarding tick exposure and travel history.

However, research presented at the FDA Babesia workshop found that questionnaire-based screening alone may fail to identify infected donors.

Several challenges remain:

• Many infected donors are asymptomatic
• Screening is not universal nationwide
• A single donor may infect multiple recipients
• Babesia can survive during blood storage

Improved molecular testing and broader screening strategies may help reduce risk.

Babesia vs Lyme Disease in Blood Transfusion

Patients frequently ask whether Lyme disease can spread through blood transfusion.

Although Borrelia burgdorferi may survive briefly in blood products, there have been no confirmed cases of Lyme disease transmitted through transfusion.

Babesia microti, by contrast, infects red blood cells directly and can survive blood storage, making transfusion-related infection possible.

This distinction explains why Babesia—not Lyme disease—is considered the primary transfusion-transmitted tick-borne infection.

Frequently Asked Questions

Can Babesia spread through blood transfusion?

Yes. Babesia can be transmitted through contaminated blood products.

Can Lyme disease spread through blood transfusion?

No confirmed cases of Lyme disease transmission through transfusion have been documented.

Who is most at risk from transfusion-transmitted Babesia?

Immunocompromised patients, elderly individuals, premature infants, and patients requiring repeated transfusions are at highest risk.

Can Babesia be passed from mother to child?

Yes. Congenital transmission of Babesia has been reported.

Why does donor screening miss Babesia?

Many infected donors have no symptoms, and questionnaire-based screening may fail to detect infection.

Clinical Takeaway

Babesia is now the leading transfusion-transmitted parasitic infection in the United States.

Because many infected donors have no symptoms, screening gaps may place vulnerable patients at risk.

Clinicians should consider Babesia in patients with unexplained fever or hemolytic illness following transfusion, even in non-endemic regions.

Related Articles

These related articles explore Babesia transmission, congenital infection, co-infections, and diagnostic challenges associated with tick-borne disease.

Babesia Blood Donation: When Screening Finds Infection
Lyme Coinfections
Congenital Babesia Case
Lyme Disease Misdiagnosis
Delayed Lyme Disease Diagnosis

References

1. Leiby DA. Transfusion-transmitted Babesia spp.: Bull’s-eye on Babesia microti. Clin Microbiol Rev. 2020;33(2):e00022-19.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention