Which Organism Is Most Likely Transmitted by Blood Transfusion?

Babesia microti is the leading tick-borne transfusion infection
Other tick-borne pathogens have rarely been transmitted through donated blood
Lyme disease has not been confirmed to spread through blood transfusion

Which organism is most likely to be transmitted through a blood transfusion? Among tick-borne pathogens, Babesia microti is the organism most commonly associated with transfusion-transmitted infection. According to an FDA-sponsored public workshop, more than 200 transfusion-transmitted cases had been reported in the United States at the time of the meeting. In contrast, there have been no confirmed cases of Lyme disease transmitted through the blood supply.

In their article, “Emerging Tick-Borne Diseases and Blood Safety: Summary of a Public Workshop,” Mohan and Leiby summarized discussions from a public workshop organized by the U.S. Food and Drug Administration (FDA).

The workshop, entitled “Emerging Tick-Borne Diseases and Blood Safety,” brought together experts in tick-borne diseases, representatives from blood centers, academic institutions, government agencies, and manufacturers of diagnostic tests. Participants reviewed emerging tick-borne infections in the United States and discussed whether additional blood safety measures should be implemented.

Listen to the podcast: Three premature babies who contract Babesia from blood transfusions

Why Babesia microti is the leading tick-borne transfusion infection

Workshop participants agreed that Babesia microti has posed the greatest tick-borne threat to the U.S. blood supply. At the time of the workshop, more than 200 cases of transfusion-transmitted babesiosis had been reported in the United States.

According to Dr. Peter J. Krause, Babesia microti often reaches substantially higher concentrations in the bloodstream than Borrelia burgdorferi. Because the parasite infects red blood cells, infected donors may unknowingly transmit the organism while feeling completely well or experiencing only mild symptoms.

This characteristic distinguishes babesiosis from Lyme disease and explains why blood banks have focused much more attention on Babesia microti than on Borrelia burgdorferi.

Transfusion-transmitted babesiosis can be particularly severe in:

• Premature infants
• Older adults
• People without a spleen
• Individuals receiving chemotherapy or other immunosuppressive therapy
• Patients with weakened immune systems

For additional discussion of donor screening and blood safety, see Babesia patients and blood bank safety concerns.

Can Lyme disease be transmitted through blood transfusion?

Borrelia burgdorferi, the bacterium responsible for Lyme disease, behaves very differently in the bloodstream than Babesia microti.

Unlike Babesia, which infects red blood cells and may circulate at relatively high levels, Borrelia burgdorferi is generally present in much lower concentrations in the blood before moving into tissues throughout the body.

Laboratory studies have shown that B. burgdorferi can survive in fresh frozen plasma, red blood cells, and platelets during blood storage. However, despite these experimental findings, there have been no confirmed cases of Lyme disease transmitted through blood transfusion.

This biological difference largely explains why Babesia microti poses a much greater transfusion risk than Lyme disease.

It also explains why blood safety efforts have primarily focused on detecting Babesia microti in donated blood rather than Borrelia burgdorferi.

For more information on Lyme disease testing and why the organism is often difficult to detect in blood, see Lyme disease test accuracy.

Other tick-borne infections transmitted through donated blood

Other tick-borne pathogens have occasionally been transmitted through donated blood, but the reported numbers discussed during the workshop were substantially lower than those for Babesia microti.

• 11 cases: Anaplasma phagocytophilum, the agent responsible for anaplasmosis and transmitted primarily by Ixodes ticks
• 2 cases: Viruses within the tick-borne encephalitis virus complex, including Powassan virus and deer tick virus
• 1 case: Colorado tick fever virus, transmitted by Rocky Mountain wood ticks
• 1 case: Rickettsia rickettsii, the agent responsible for Rocky Mountain spotted fever
• 1 case: Ehrlichia ewingii, transmitted primarily by the lone star tick

One workshop attendee described Anaplasma phagocytophilum as the most frequent transfusion-transmitted tick-borne agent after Babesia, with a rapidly increasing number of recognized clinical cases.

[bctt tweet=”The threat to blood safety from tick-borne agents is ever-increasing.” username=”DrDanielCameron”]

Emerging concerns involving Borrelia miyamotoi and Powassan virus

The workshop also addressed two emerging tick-borne pathogens: Borrelia miyamotoi and Powassan virus.

Reported cases of B. miyamotoi infection had steadily increased since 2014. The organism causes hard tick relapsing fever and may circulate at higher concentrations in the blood than B. burgdorferi.

However, despite the higher concentrations of B. miyamotoi that may be present in blood, no transfusion-transmitted cases had been reported at the time of the workshop.

Testing can also be challenging because Lyme disease antibody tests may sometimes react in patients with B. miyamotoi infection. This issue is discussed further in C6 peptide testing and Borrelia miyamotoi.

Screening blood donors to reduce transmission

Blood donor screening has reduced the transmission of several infections, including HIV, hepatitis B, and malaria.

Between 1963 and 2013, 99 cases of malaria transmitted through blood transfusion were reportedly identified. Most occurred before 2000. Since 2000, the rate has fallen to fewer than one case per year, the authors explained.

A related example is described in a reported malaria and Lyme disease coinfection.

Unfortunately, donor questionnaires alone do not always identify infected individuals. Studies discussed during the workshop found no reliable correlation between infection and donor responses regarding a history of tick bites, babesiosis, or Chagas disease.

This limitation is especially important for babesiosis because an infected donor may feel well and may not recall a tick bite.

Frequently Asked Questions

Which organism is most likely to be transmitted through blood transfusion?

Among tick-borne organisms, Babesia microti is the pathogen most commonly transmitted through blood transfusion. More than 200 transfusion-transmitted cases had been reported in the United States at the time of the FDA workshop.

Can Lyme disease be transmitted through a blood transfusion?

There have been no confirmed cases of Lyme disease transmitted through the blood supply. Although Borrelia burgdorferi can survive in stored blood products under laboratory conditions, it is generally present at low concentrations in the bloodstream.

Is Lyme disease a bloodborne pathogen?

Lyme disease is caused by Borrelia burgdorferi, which can circulate briefly in the bloodstream early in infection. However, Lyme disease has not been shown to spread through blood transfusion.

Why can Babesia be transmitted through donated blood?

Babesia microti infects red blood cells and may circulate in the blood of individuals who have no symptoms or only mild symptoms. An infected person may therefore donate blood without realizing that the infection is present.

Which tick-borne diseases can be transmitted through donated blood?

Babesia microti is the most important tick-borne pathogen transmitted through donated blood. Rare transfusion-transmitted cases involving Anaplasma phagocytophilum, Powassan virus, Colorado tick fever virus, Rickettsia rickettsii, and Ehrlichia ewingii have also been reported.

Can someone who has had Lyme disease donate blood?

Blood donation eligibility depends on the person’s current health and the policies of the blood collection organization. Individuals who are actively ill or being treated for a tick-borne infection should discuss donation eligibility with the blood center.

Are all donated blood units screened for Babesia?

Babesia screening requirements and practices may depend on current regulatory guidance, geographic risk, and the blood collection organization. Donor questionnaires alone may not detect infections in individuals who do not remember a tick bite or have no symptoms.

Clinical Takeaway

Babesia microti remains the most important tick-borne pathogen associated with transfusion-transmitted infection because it infects red blood cells and may circulate in healthy-appearing blood donors who have few or no symptoms.

Although several other tick-borne pathogens—including Anaplasma phagocytophilum, Powassan virus, Colorado tick fever virus, Rickettsia rickettsii, and Ehrlichia ewingii—have rarely been transmitted through donated blood, their reported numbers remain far lower than those of babesiosis.

Laboratory studies have demonstrated that Borrelia burgdorferi can survive in stored blood products, but its low concentration in circulating blood and preference for tissue infection likely explain why transfusion-associated Lyme disease has not been documented.

Current evidence indicates that Babesia microti—not Lyme disease—remains the principal tick-borne threat to the U.S. blood supply.

Related Articles

Learn more about transfusion-transmitted babesiosis, donor screening, and other Babesia-related topics.

Study raises concerns for Babesia patients and blood banks
Severe Babesia infection leads to exchange transfusion
Transfusion-transmitted babesiosis reported in more states
Babesia symptoms, diagnosis, and treatment

References

1. Mohan KVK, Leiby DA. Emerging tick-borne diseases and blood safety: Summary of a public workshop. Transfusion. 2020;60(8):1624-1632.

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