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Malaria parasites common among blood donors
Globally, as many as 1 in 10 healthy blood donors may carry malaria parasites, making transfusion-transmitted malaria, or TTM, one of the most common transfusion- associated infections, according to results from a systematic review and meta-analysis published in Open Forum Infectious Diseases.
Researchers found that malaria parasitemia was particularly common in sub-Saharan Africa, with almost one-third of blood donors in Nigeria testing positive.
“Although it is not surprising to observe high prevalence in Nigeria given that it is one of the most malaria-affected countries, primarily due to the increased number of vector mosquitos, socioeconomic conditions and favorable climate, worryingly one-third of healthy donors by microscopy was found to be malaria infected,” Ehsan Ahmadpour, MD, PhD, assistant professor of parasitology and mycology at Tabriz University of Medical Sciences in Iran, and colleagues wrote.
“This emphasizes that TTM is one of the most significant transfusion-associated infections in sub-Saharan African compared with other infections such as HIV, hepatitis C and hepatitis B where the prevalence ranges from 0.5% to 16%, 0.5% to 3% and 5% to 25%, respectively.”
Ahmadpour and colleagues included 71 studies from 21 countries and five continents in their review. Studies had to be peer-reviewed original cross-sectional studies published online in English between 1982 and Oct. 10, 2017, that estimated the prevalence of malaria infection in blood donors as obtained by microscopy, rapid diagnostic tests (RDT) or molecular techniques.
The studies included a total of 984,975 blood samples examined for malaria infection — 374,919 by microscopy, 604,693 by RDT including immunochromatographic test and 5,363 by molecular techniques including PCR, real-time PCR, PCR-restriction fragment length polymorphism and nested PCR.
According to Ahmadpour and colleagues, the pooled proportion of malaria prevalence among the blood donor population was 10.54% (95% CI, 8.44-12.84) by microscopy — the “gold standard” diagnostic technique — 5.36% (95% CI, 2.25-9.7) by PCR and 0.38% (95% CI, 0.25-0.54) by RDT.
They also compared studies published before and after 2010 to provide a recent estimate of the prevalence by microscopy in this population and found that the pooled prevalence of malaria infection in asymptomatic blood donors was 7.14% (95% CI, 3.61-11.74) among pre-2010 studies and 13.61% (95% CI, 9.33-18.55) among post-2010 studies, although the difference was not statistically significant.
In a subgroup analysis by continent, the researchers found the highest prevalence of malaria infection among blood donors by microscopy was 21% (95% CI, 14%-29%) in Africa, which also had the highest prevalence observed by RDTs at 7.4% (95% CI, 3%-12%), as well as by PCR [36% (95% CI, 11%-72%). Molecular methods did not impact the observed prevalence in other continents, which were 4% (95% CI, 1%-13%) in Asia, 2% (95% CI, 1%-7%) in the Americas and 1% (95% CI, 0%-3%) in Europe. No parasitemia was detected in other continents, Ahmadpour and colleagues wrote.
Nigeria had the highest estimated prevalence (31.7%), followed by Ghana (19.4%) and Sudan (17%). The lowest estimated prevalence rates were observed in Turkey and China.
Multivariate analysis revealed a positive association between malaria infection and female sex, commercial donor type and A blood group. Patients living in rural areas and with no previous transfusions had a higher prevalence of infection, though this was not statistically significant, according to the study.
“WHO guidelines for screening and deferral need to be reinforced in each country and tailored to the local context,” Ahmadpour and colleagues wrote. “Future work must aim to understand the clinical significance of transfusion-transmitted malaria in malaria-endemic settings.” – by Joe Gramigna
Disclosures: The authors report no relevant financial disclosures.