Transfusion-transmitted malaria will be a thing of the past in Europe

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The current strategy used in Europe to reduce the risk of malaria transfusions is efficient: only ten cases have been reported in the last twenty years. However, current serological tests used to identify ‘high-risk’ donors are not sensitive enough to completely eliminate the risk.

In a presentation that will be given this year ESCMID Global Congress (formerly ECCMID) in Barcelona, ​​Spain (April 27-30), Dr. Sophie Le Cam of the French blood transfusion service (Etablissement Français du Sang [EFS]), discusses the ongoing efforts being made to prevent transfusion-associated malaria in Europe and outlines the different malaria screening strategies that need to be combined to ensure the safety of blood transfusions in the future.

Transfusion-transmitted malaria (TTM) is an accidental Plasmodium infection caused by transfusion of whole blood or a blood component from a malaria-infected donor to a recipient. Just a few parasites in a unit of blood are enough to cause an infection, and all Plasmodium species can survive in stored blood, even when frozen, remaining viable for at least a week. Ten cases of TTM have been reported in Europe in the last twenty years, in France, Spain, Great Britain, Italy and the Netherlands.

Dr. Le Cam highlights an important difference between natural malaria infection and TTM saying, “When individuals are naturally infected with malaria through a mosquito bite, they undergo an initial asymptomatic phase during which immunity cells can be activated against malaria parasites.

“But infected blood transfusions deliver malaria parasites directly into the bloodstream, causing high-risk complications that can potentially lead to fatal outcomes, especially in non-endemic countries where the majority of people have never been exposed to malaria, and in patients with a weakened immune system, such as people with cancer and the elderly.”

Europe has a mandatory guideline to prevent TTM, which recommends that people who have recently traveled to a country with malaria, or former residents of areas where malaria occurs, should not donate blood for at least six months and three years after their return, respectively.

In many countries, this grace period can be reduced to four months if a negative malaria test is presented before each donation. However, the existing microscopy and serological tests used to mandate these rules are not sensitive enough to reliably reduce the risk of malaria transfusions.

Microscopic examination is the ‘gold standard’ for the diagnosis of malaria, but has not been adapted to the activities of blood banks in Europe. Serological tests are widely used, but their sensitivity and specificity are not as good as expected.

According to Dr. Le Cam: “The most difficult risk to mitigate comes from donors who were born or spent their early childhood in countries where malaria is endemic, and who may develop an immune tolerance – a host response that protects against large numbers of parasite and disease without eliminate the infection.”

In these infectious, immune-tolerant individuals, cases of TTM have been associated with blood donations more than five years after the donor’s last potential exposure to P. falciparum, and decades in the case of P. malariae.

Like Dr. Le Cam explains: “These asymptomatic infections characterized by low parasite density require more sensitive detection methods, such as recent molecular methods. But while a fully automated molecular method may be the ideal screening method for malaria infections in the blood donor population, it is an expensive option.”

Le Cam sees the current challenge in optimizing testing strategy in non-endemic countries as increasing screening sensitivity for immunotolerant donors without compromising the availability of blood products.

“On the one hand, the limited number of potentially infected donors requires a cost-effective strategy of blood donor screening, but on the other hand, the accuracy of screening must be optimal for the severe consequences of TTM in malaria-naïve and immunocompromised recipients. ,” she says.

What needs to be done to ensure that TMM in Europe becomes a thing of the past?

According to Dr. Le Cam, “the key to transfusion safety remains the grace period after the return of donors from endemic countries. But we really need to develop new testing strategies. The parasitic inactivation of blood using new technologies capable of selectively inactivating blood pathogens without damaging cells or plasma could also be a good option, but the technology is not completely reliable for packed red blood cells and is very expensive.

“Ultimately, several strategies need to be combined to ensure the safety of blood transfusions in Europe, including screening blood donors using appropriate diagnostic tools, which will likely include molecular testing.”

Provided by the European Society of Clinical Microbiology and Infectious Diseases

Quote: Making transfusion-transmitted malaria in Europe a thing of the past (2024, April 26) retrieved April 27, 2024 from

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