Evaluation of a malarial antibody assay for use in the screening of blood and tissue products for clinical use

BACKGROUND AND OBJECTIVES: A new recombinant Plasmodium antigen enzyme immunoassay (EIA) for the detection of malarial antibodies was evaluated for the screening of 'malaria-risk' blood and tissue donations. MATERIALS AND METHODS: A total of 13,269 donor and patient samples were tested by both the EIA and the standard diagnostic antibody immunofluorescence test (IFAT). RESULTS: A total of 114/138 (82.6%) samples from patients with P. falciparum and 11/13 (84.6%) samples from patients with P. vivax tested positive. A total of 714/13,053 (5.47%) samples from donors identified as 'malaria risk', owing to residency or travel, were reactive in the EIA. CONCLUSIONS: The assay is more sensitive than a previously implemented malarial antibody EIA (73% in acute P. falciparum and 56% in acute P. vivax infections). The sensitivity of this new EIA is comparable to that of the IFAT, and the specificity is sufficient to screen 'malaria-risk' donors.     

Anti-sporozoite antibodies induced by natural infection

Serum samples from 120 individuals living in a malaria-endemic area, 31 patients with Plasmodium falciparum infection, and 58 healthy blood donors were tested for antibodies against P. falciparum and P. vivax sporozoites. Specific antibodies were determined by the circumsporozoite precipitation (CSP) reaction and indirect immunofluorescent (IFA) tests for IgG and IgM antibodies. It was found that a high proportion of adults living in the endemic area had IFA anti-sporozoite antibodies, usually IgG. Children and healthy donors were either negative or had low antibody titers. A positive correlation was found between IgG antibody titers against P. falciparum sporozoites and those against P. vivax sporozoites. CSP reactivity was demonstrated in 5 of 31 sera from patients with falciparum malaria, and was always associated with a high level of IFA antibodies. The anti-sporozoite antibodies were found to be stage- and species-specific.     

Two cases of Plasmodium vivax Malaria with the clinical picture resembling toxic shock

Fatal complications of Plasmodium falciparum malaria have been reported. However, complicated P. vivax malaria is rare. We observed two unusual cases of P. vivax malaria who presented with clinical pictures of toxic shock. Both showed disseminated intravascular coagulation with marked thrombocytopenia, oliguric renal failure, and pulmonary edema. Examination of initial blood smears showed a P. vivax parasitemia of 2,352/microL and 12,376/microL, respectively. The patients were treated with hydroxychloroquine and primaquine without an antibacterial agent. These cases emphasize the importance of considering the possibility of P. vivax malarial infection in patients with a clinical picture resembling toxic shock if they have a travel history to malaria-endemic areas.     

Primary infection by Plasmodium falciparum or P. vivax in a cohort of Javanese migrants to Indonesian Papua

The clinical and parasitological characteristics of the first naturally acquired malarial infection have rarely been documented in humans. When 243 migrants from non-endemic Java were followed from the day of their arrival in Indonesian Papua, 217 (89%) were found to become infected with Plasmodium falciparum and/or P. vivax before they were lost to follow-up. The incidence of malarial infection in the children investigated (who were aged 6-10 years) was indistinguishable from that in the adults (aged >20 years), with 1.10 and 1.14 P. falciparum infections/person-year (relative risk=0.97; 95% confidence interval=0.72-1.29) and 1.47 and 1.49 P. vivax infections/person-year (relative risk=0.99; 95% confidence interval=0.72-1.29), respectively. During their first infections, the children had higher P. falciparum parasitaemias than the adults (with geometric means of 1318 and 759 parasites/microl, respectively; P=0.04) but similar P. vivax parasitaemias (with geometric means of 355 and 331 parasites/microl, respectively; P=0.76). At first infection, 56% of the subjects were febrile and 90% complained of symptoms. There were no differences between children and adults with respect to these two parameters, either for P. falciparum or P. vivax. These findings indicate that, with promptly diagnosed and treated uncomplicated malaria, migrant children and adults in north-eastern Indonesian Papua have an equal risk of malarial infection and of disease following their first infections with P. falciparum and P. vivax.     

Malaria during pregnancy and infancy, in an area of intense malaria transmission in central India

The clinico-epidemiological pattern of malarial infection in a cohort of pregnant women and infants was analysed during a malaria epidemic (1997-1998). The subjects were all members of tribal communities in an isolated and almost inaccessible area of central India. Overall, 151 (55%) of the 274 pregnant women investigated were found to have malarial infections at some time during the study, with Plasmodium falciparum predominating (88% of infections). All of the women investigated, whether primigravidae (42% found infected), secundigravidae (68%) or multigravidae (54%), were at great risk of developing severe malaria. When trimesters were compared, the highest prevalence of P. falciparum infection was recorded in the second (59% infected), irrespective of parity. Of the women found infected with P. falciparum, 3% had abortions, 4% stillbirths and 2% had babies who died while neonates. The small number of P. vivax infections observed prevented similar analyses for this species of parasite. Malarial infection was also seen in 218 (41%) of the 535 infants investigated. The values of age-specific prevalences revealed that > 30% of the infants examined at 2 months of age were then found to have P. vivax and/or P. falciparum parasitaemias. At 1 year of age, overall malaria prevalence was 50%, with P. vivax representing 25% of the infections and P. falciparum the rest. Subsequent follow-up revealed that three of the infants investigated, each of whom had had P. falciparum infections previously, died before their first birthdays. Re-infections (or treatment failures) were found to be common, both in the infants and the pregnant women. Pregnant women and infants from the study area clearly require systematic intervention to reduce their malaria-attributable morbidity.     

High prevalence of asymptomatic Plasmodium falciparum infection in Gabonese adults

Plasmodium falciparum, the most common malarial parasite in sub-Saharan Africa, accounts for a high number of deaths in children less than five years of age. In malaria-endemic countries with stable transmission, semi-immunity is usually acquired after childhood. For adults, severe malaria is rare. Infected adults have either uncomplicated malaria or asymptomatic parasitemia. During a period of one year, we screened 497 afebrile males to investigate the prevalence of asymptomatic P. falciparum parasitemia in villages near Lambaréné, Gabon by use of three different methods. A total of 52% of the individuals had parasites detected by a subtelomeric variable open reading frame polymerase chain reaction (stevor-PCR), 27% of the rapid diagnostic test results were positive, and 12% of the thick blood smears with low parasitemias had P. falciparum. Most positive cases were only detected by the stevor-PCR. Asymptomatic P. falciparum parasitemia in adults living in a malaria-endemic country is frequent.     

Imported malaria in southern Taiwan from 1991 to 2002: a single hospital's experience

Malaria, a major public health problem worldwide, is a predominant infectious disease in most tropical and subtropical countries. Before 1965, Taiwan was a hyperendemic area, but most cases are now imported. We present our experience of dealing with various malaria infections. Charts of malaria patients visiting university hospitals in southern Taiwan between January 1991 and June 2002 were available for review. All diagnoses were made by positive blood smear and detailed history that included countries visited, paroxysm of symptoms, and medical treatment. Seventeen patients, 6 women and 11 men (mean age, 32.3 +/- 11.8 years), were enrolled. Six were infected with Plasmodium falciparum, eight with Plasmodium vivax, two with a combination of P. falciparum and P. vivax, and one with an unidentified infection. All Taiwanese patients infected with P. falciparum (n = 5) contracted the disease in Africa or Indonesia. All Taiwanese patients infected with P. vivax (n = 4) contracted the disease in Southeast Asia or Oceania. Fever and chills were the leading symptoms of malaria. P. falciparum infection was treated with quinine and doxycycline/tetracycline, with the addition of artesunate for cerebral malaria. P. vivax infection was treated with chloroquine and primaquine. Maintaining a high degree of suspicion in patients with a history of travel to malaria-endemic areas is the major cornerstone of malaria diagnosis. Erroneous diagnosis and improper treatment leads to greater morbidity and even mortality.     

Detection of P. vivax antigens in malaria endemic populations of Nepal by ELISA using monoclonal antibodies raised against Thai isolates

An indirect enzyme linked immunosorbent assay (ELISA) using monoclonal antibody (MAb) originated from the native Thai isolates of P. vivax (McPV1) and the polyclonal antibody (PAb) raised against Nepali isolates of P. vivax was developed for detection of P vivax antigens in red cell lysates. The assay was specific (100%) since it was positive only with P. vivax-infected erythrocytes and was negative when erythrocytes from 40 healthy individuals from malaria non-endemic areas and 40 P. falciparum infected erythrocytes were tested. When the assay was applied to 203 vivax blood samples already proven by microscopic examination collected from Dhanusha district of Nepal, and using the cut-off level of the mean optical density (OD) (0.144) of 40 healthy individuals who had been living in malaria-endemic areas (0.073) + 2 SD (0.016), the assay could detect 189/203 samples, indicating the sensitivity of the test was 93.1% with a detection limit of erythrocytes of 240 parasites/10(6) erythrocytes. In addition, the assay was negative when 40 blood samples with fever of unknown origin, collected from the same malaria-endemic areas, were tested. However, there was a significant correlation between OD values and parasitemia (r=0.649; p=0.018). The results indicate that MAb-PAb indirect ELISA using MAb raised against Thai isolates of P. vivax as the coating antibodies, and polyclonal antibodies raised against local Nepali isolates as the detecting antibody, could detect P. vivax antigens with high degrees of sensitivity and specificity. Furthermore, it seems that the McPV1 MAb raised against Thai isolates of P. vivax could recognize the antigens of Nepali isolates in a wide range of blood samples.     

Malaria in a cohort of Javanese migrants to Indonesian Papua

The epidemiology of infection by Plasmodium falciparum and P. vivax was investigated among Javanese migrants to an endemic region of Papua, Indonesia. A cohort of 243 migrants from Java was followed for malaria in a new settlement village in the endemic Armopa area of north-eastern Papua, beginning on the day each migrant arrived in the village. The subjects were monitored during home visits (three/week) and by the twice-monthly production of bloodsmears that were checked for malarial parasites. At the end of 33 months, 159 (65%) of the subjects remained under follow-up. The prevalence of parasitaemia in the village declined from 16% among those already living there when the study began in August 1996, to 5% when the study finished in June 1999. Over this period, 596 infections by P. falciparum and 723 by P. vivax occurred in the cohort, 22 and 27 of the subjects each experiencing at least six infections by P. falciparum and P. vivax, respectively. The incidence of malarial infection was higher during the first and second years post-migration (3.2 and 2.7 infections/person-year) than during the third (1.2 infections/person-year). Although the geometric mean parasite counts for P. falciparum increased over time (1209, 1478, and 1830 parasites/microl in the first, second and third years, respectively), the corresponding values for P. vivax (497, 535 and 490 parasites/microl) showed no such trend. Only one of the nine subjects who developed severe malaria (requiring intravenous quinine therapy) was a child, giving an odds ratio for a case of severe malaria being in an adult of 6.1 (P=0.08).     

Transfusion-transmitted malaria: case report of asymptomatic donor harboring Plasmodium malariae

Malaria in Brazil is endemic in the Amazon region, but autochthonous cases with low parasitaemia occur in the Atlantic Forest area of the country. According to Brazilian legislation no test is mandatory for blood donors from non-endemic areas. However if they have traveled to malaria transmission regions they are deferred for six months before they can donate. This report describes a transfusion-transmitted malaria case in Sao Paulo, Brazil, where one recipient received infected blood and developed the disease. He lived in Sao Paulo and had no previous transfusion or trips to endemic areas, including those of low endemicity, such as Atlantic Forest. Thick blood smears confirmed Plasmodium malariae. All donors lived in Sao Paulo and one of them (Donor 045-0) showed positive hemoscopy and PCR. This asymptomatic donor had traveled to Juquia, in the Atlantic Forest area of S ao Paulo State, where sporadic cases of autochthonous malaria are described. DNA assay revealed P. malariae in the donor's (Donor 045-0) blood. Serum archives of the recipient and of all blood donors were analyzed by ELISA using both P. vivax and P. falciparum antigens, and IFAT with P. malariae. Donor 045-0's serum was P. malariae IFAT positive and the P. vivax ELISA was reactive. In addition, two out of 44 donors' archive sera were also P. vivax ELISA reactive. All sera were P. falciparum ELISA negative. This case suggests the need of reviewing donor selection criteria and deferral strategies to prevent possible cases of transfusion-transmitted malaria.     

Distribution of two species of malaria, Plasmodium falciparum and Plasmodium vivax, on Lombok Island, Indonesia

Medical and entomological surveys were conducted to determine the risk factors of Plasmodium falciparum and P. vivax infections on Lombok Island, Indonesia, to find the risk factors and the main mosquito vectors for each malaria. Multivariate longitudinal analysis demonstrated two significant risk factors for infection with P. falciparum: disappearance of P. vivax parasitemia (p<0.001) and a specific study site (p<0.001). In contrast, younger age (p=0.024) and the interpolated virtual density of An. subpictus (p=0.041) were significantly associated with increased risk of infection with P. vivax. Thus, it seems that the distribution of P. vivax was determined largely by the presence of An. subpictus, whilst that of P. falciparum was influenced by antagonism with P. vivax. This result shows the importance of following-up treated P. vivax patients to identify recrudescence of P. falciparum in this area.     

Prevalence and risk of Plasmodium falciparum and P. vivax malaria among pregnant women living in the hypoendemic communities of the Peruvian Amazon

The Amazon region of Iquitos, Peru is hypoendemic for Plasmodium vivax and P. falciparum. There is limited information regarding the epidemiology of malaria during pregnancy in this region. Passive surveillance for clinical malaria among pregnant women was conducted in eight health posts in 2004 and 2005. Community-based active surveillance was conducted to determine the incidence of malarial infection among pregnant women in the community of Zungarococha in 2004 and 2005. Passive surveillance demonstrated that pregnant women had a prevalence of clinical malaria of 7.5% in 2004 and 6.6% in 2005 compared with 20.6% and 22.4% of the total population. Active surveillance showed that pregnant women were 2.3 (95% confidence interval = 1.32-3.95, P = 0.004) times more likely to have a P. falciparum infection compared with non-pregnant women. This study demonstrated that because of detection bias, passive surveillance underestimates the burden of malarial infection during pregnancy, and that subclinical malarial infections may occur frequently among pregnant women in this region. Furthermore, pregnant women in this low-transmission and P. vivax-dominant setting, experience an increased risk for P. falciparum infection, but not P. vivax infection.     

The impact of repeated malaria attacks on the school performance of children

The impact of repeated malarial infections on the school performance of children was investigated in 571 school children 6-14 years of age in a malaria-endemic area in southern Sri Lanka where both Plasmodium falciparum and P. vivax infections are prevalent. Malaria infections confirmed by microscopy were monitored over a six-year period. School performance was assessed by two specially designed, school grade-specific, test papers for Sinhala language and mathematics. The scores for Sinhala language and mathematics for each school term test for the year 1997 were obtained. Malarial infections were a major predictor of children's performance in language and mathematics after controlling for parent's education, monthly family income, and house type. The education of the father predicted language scores but not mathematics scores. A child who experienced more than five attacks of malaria scored approximately 15% less than a child who experienced less than three attacks of malaria. The data suggest that repeated attacks of malaria have an adverse impact on the school performance of children.     

Rapid immunochromatography-based detection of mixed-species malaria infection in Pakistan

We report the identification of mixed Plasmodium infections in four recent patients with malaria clinically refractory to empiric chloroquine therapy using the rapid antigen detection kit, NOW ICT Malaria Pf/Pv. A rapid in vitro immunodiagnostic test, the NOW ICT Malaria Pf/Pv test kit was used for the detection of circulating Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) antigens in whole blood. Peripheral blood microscopy confirmed mixed-species infection in all the cases. Thick and thin peripheral blood films were made and stained with Giemsa stain and examined by both hospital laboratory staff and an experienced parasitologist who was blinded to the results of the rapid malarial antigen tests. Four recent patients (all male; mean age, 24 years) with mixed malarial infection were identified. All the subjects were males working for an oil company in a coastal area of Pakistan, and all had been diagnosed presumptively with malaria based on clinical grounds (without microbiologic confirmation), and were treated empirically with chloroquine without clinical response. Semiquantitative malaria counts via microscopy were as follows: P. vivax, scanty (2 patients) and moderate (2 patients); for P. falciparum--scanty (1 patient), moderate (2 patients), and heavy (1 patient). The present case series, although limited by the small number of patients with proven mixed P. falciparum-P. vivax infection, highlights the usefulness of the rapid antigen test in a highly malarious region of Pakistan where chloroquine resistance is prevalent. Although there was full concordance between the results of blood smear microscopy and rapid antigen testing, these techniques are potentially most useful when there is a discrepancy with microscopy findings. Accurate and rapid diagnosis of parasites, particularly in cases of mixed P. falciparum and P. vivax infection, is of immense importance for individual patient management and in reducing the burden of disease, especially in regions of chloroquine resistance.     

Epidemiology and spatial analysis of malaria in the Northern Peruvian Amazon

A retrospective surveillance study was conducted to examine the micro-geographic variation of malaria incidence in three malaria-endemic communities in the Northern Peruvian Amazon. The annual malaria risk rate (per 100) ranged from 38% to 47% for Plasmodium vivax and from 15% to 18% for P. falciparum. Spatial clusters were found for P. vivax in Padre Cocha, Manacamiri, and Zungaro Cocha, and for P. falciparum only in Padre Cocha. Spatial-temporal clusters showed that the highest monthly number of P. vivax cases varied every year from December to March in 1996-1997 and from February to June in 1998-1999, and for P. falciparum from November to April in 1996-1997 and from January to April in 1998-1999. Our results suggest a constant presence of high-risk areas (hot spots) for malaria infection in periods with high or low malaria incidence. Modest targeted control efforts directed at identified high-risk areas may have significant impact on malaria transmission in this region.     

Detection of specific antibodies to Plasmodium falciparum in blood bank donors from malaria-endemic and non-endemic areas of Venezuela.

Malaria antibody detection is valuable in providing retrospective confirmation of an attack of malaria. Blood bank screening is another area were malaria serology is potentially useful. In the present study, we tested the presence of antibodies to Plasmodium falciparum in sera from blood bank donors of non-endemic and malaria-endemic areas of Venezuela. Sera from 1,000 blood donors were tested by an indirect immunofluorescent antibody (IFA) assay and an IgG-ELISA for the presence of malaria antibodies using a synchronized in vitro-cultured Venezuelan isolate of P. falciparum as the antigen source. A selected group of positive and negative sera (n = 100) was also tested by a dot-IgG-ELISA. Positive results (reciprocal titer > or = 40) were found in 0.8% and 3.8% of blood donors when tested by the IFA assay and in 0.8% and 2% (optical density > or = 0.2) when tested by the IgG-ELISA in Caracas (non-endemic area) and Bolivar City (endemic area), respectively. The presence of anti-malarial antibodies in some sera from non-endemic areas such as Caracas reflects the increased potential risk of post-transfusional malaria in those areas due to the mobility of the blood donors. The data obtained indicate the need to implement new blood donor policy in blood banks in developing areas. Our results also indicate that the IFA assay is the most reliable test to use in malaria serodiagnosis.     

快速免疫色谱测试卡诊断恶性疟和间日疟的效果评价

目的： 评价快速免疫色谱测试卡（ Ｉ Ｃ Ｔ） 在疟区诊断恶性疟和间日疟的效果。方法： 以疟原虫镜检结果为标准, 用 Ｉ Ｃ Ｔ 检测门诊“四热”病人中的恶性疟和间日疟。结果： Ｉ Ｃ Ｔ 检测恶性疟与间日疟的敏感性分别为９６７ ％ 和９０４ ％ , 特异性为９８６ ％ 。与原虫镜检结果的符合率为９４７ ％ 。恶性疟与间日疟之间无交叉反应。结论： 免疫色谱测试卡可同时检测恶性疟和间日疟, 较镜检法快速、简易。     

First year donation patterns predict long-term commitment for first-time donors

BACKGROUND AND OBJECTIVES: Converting first-time donors to become regular donors continues to be a challenge facing blood centres. We examined whether first-time donors with frequent return in the first 12 months were more likely to become regular donors. SUBJECTS AND METHODS: The donation histories of 179 409 community whole-blood donors, whose first-time donation in 1991 was negative on donor screening tests, were evaluated. Donors were categorized by the number of donations made in the 12 months after (and including) their first donation. The donor return pattern in the subsequent 6 years, and its association with first-year donation frequency and demographics, was evaluated by using logistic regression analysis. A 'regular donor' was defined as one who returned to donate in at least 4 of the 6 years of follow-up. RESULTS: First-year donation frequency was significantly correlated with long-term donor return (P < 0.0001). Among those giving 1, 2, 3, 4 and > or = 5 donations in the first year, 4%, 11%, 21%, 32% and 42%, respectively, became regular donors (P < 0.0001). Similar associations between donation pattern and donor return behaviour were observed after adjusting for demographic variables (P < 0.0001). CONCLUSIONS: Strategies aimed at encouraging current donors to donate more frequently during the first year may help to establish a regular donation behaviour.