Transfusion malaria in Riyadh: Is improved screening needed?

On June 15, 1998, the infection control officer at a Riyadh hospital reported a case of locally acquired malaria in a 6-week-old infant who was born 28-weeks premature. The infant was admitted to a public pediatric hospital on April 12, 1998, with severe respiratory distress, anemia, thrombocytopenia, jaundice, hydrocephalus, and interventricular hemorrhage. The infant developed Plasmodium falciparum malaria after receiving multiple blood transfusions in the hospital. The officer requested help from the Field Epidemiology Training Program (FETP) to determine whether the malaria had been acquired by blood and blood-product transfusion or by another mode of transmission, and to suggest a practical approach in preventing transfusion malaria.

We reviewed the medical files of the infant and interviewed the infant's mother about-history of malaria both before and during pregnancy, any symptoms of malaria, or any recent travel to malarious areas. We also reviewed the mother's medical file of prenatal visits. At the hospital, we reviewed heparin preparation and administration, and intravenous device procedures to find any malpractice in these procedures. Then, we reviewed the malaria log books in the hospital parasitology lab for 2 months prior to admission of the infant, during admission, and 2 months after admission. We interviewed the nursery physicians about any suspected cases of malaria, such as any febrile cases in the nursery.

We also reviewed records of the source of blood units transfused to the infant and interviewed donors of these blood units about exposure to malarious areas. We reviewed the screening procedures at the blood bank and did parallel screening interviews of 80 new donors and also reviewed other transfusion malaria reports from Riyadh. No cases of P. falciparum malaria were detected in any admitted patients or health workers in the hospital for 6 months before the premature infant's admission, during the period of his admission, or for 3 months after his admission.

Between April 16 and May 24 the infant received 19 blood transfusions. On April 19, 22, and 29, the infant received 3 blood units from 3 donors who had a history of travel to malarious villages in southwest Saudi Arabia. On May 3, the infant developed the first spike of fever (37.8° C). On May 8, he received blood units from a Yemeni donor who had travelled recently to a malarious area in Yemen. On May 13, 18, and 21 the infant developed 3 spikes of high grade fever (37.9° C, 39° C, and 38° C, respectively) (Figure 1). On May 24, a blood smear showed (20-25%) red cells infected (RBCs) with ring form of P. falciparum malaria. Gametocytes and schizonts also were present. On May 24, the infant deteriorated and developed cardiac arrest. He was resuscitated but there was no response and he was pronounced dead.

From 1996 through 1998, 9 transfusion malaria cases (2 deaths) occurred in Riyadh. From 19,580 transfusions in 1998, there were 4 transfusion malaria cases (15 per 100,000 transfusions). Moreover, only 7 malaria-positive thick films were found in the blood bank during the same time. From 80 potential donors we found 17.5% unsuitable for donation because of recent exposure to malarious areas. However, regular screening on these same 80 donors rejected only 2.5% for reporting a malaria infection.

Riyadh has never been known to be a malarious area. The city has cold winters (average temperature, 16° C) and hot summers (average temperature, >34° C). Because of these temperature extremes, anopheline mosquitoes are not found here. Riyadh has experienced rapid changes in population demographics, increased international travel, and immigration from malaria endemic areas of Saudi Arabia. The vast majority of malaria cases are imported by patients who have acquired infection outside of Riyadh but have become ill here. However, minute numbers are acquired either by blood transfusion or malpractice in intravenous procedures leading to trans-mission of malaria from malarious patients to persons free from malaria.

From 1989 to 1992, 12 malaria cases in Riyadh were found to be post-blood transfusion [1]. In January 1992, 2 Saudi patients in Madina underwent cardiac surgery and developed postoperative transfusion malaria after discharge [2].

The suspected source of infection in this infant is blood transfused to him from 1 of the 4 donors who had a history of travel to malarious areas. The most likely donor to have transmitted the infection was the donor from Yemen. High-grade parasitemia was detected in the infant after 16 days; very few parasites may be transmitted with packed cells. Fever spikes might be due to malaria pigments. A high rate of parasite multiplication took place and high-grade parasitemia was detected on May 24. Death occurred because of heavy infection or severe malarial complications.

Generally, the following evidence will support the probability of transmission of infection through blood of donors from malarious areas. First, the questionnaires regarding malaria used at local blood banks do not exclude any donors with history of exposure to malarious areas. The forms include only one question about history of malaria in the past 3 years, but no questions about any recent travel to malarious areas in the 6 months preceding donation, and no questions about history of travel to malarious areas without prophylaxis in the past 3 years. Second, the rejection rate of donors using the standard questionnaires from the American Association of Blood Banks (AABB) is higher than the rejection rate without those questionnaires. This allows the donors with history of exposure to be included in the local blood banks [3]. Third, the sensitivity of routine thick films is low and donors with low parasitemia (such as cases of malaria with recent exposure or taking chemoprophylaxis), might be missed [4,5].

We recommended that the blood banks in the Kingdom exclude donors who traveled to malarious areas during the preceding 6 months or if prophylaxis was taken during the past 3 years. We also suggested a more sensitive (e.g. immunochromatographic) test to detect low parasitemia [6]. The high rate of transfusion malaria has resulted from incomplete screening of donors for travel to malarious areas.