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Malaria control and elimination require prompt diagnosis and accurate treatment. Conventional methods such as rapid diagnostic tests (RDTs) and microscopy lack the characteristics to detect low parasitemias, commonly found in asymptomatic parasitemias and/or submicroscopic malaria carriers. On the contrary, molecular methods have higher sensitivity and specificity. This study evaluated the performance of two commercial real-time polymerase chain reaction (PCR) assays, RealStar® Malaria PCR (RealStar-genus) and RealStar Malaria Screen&Type PCR (RealStar-species), compared with the reference Nested Multiplex Malaria PCR, for the detection of the main five Plasmodium species affecting humans. A total of 121 samples were evaluated. Values of sensitivity (98.9% and 97.8%) and specificity (100% and 96.7%) of the RealStar-genus and the RealStar-species assays, respectively, were very good. The limit of detection (LoD) for the RealStar-genus assay showed a mean value of 0.28 parasites/µL with Plasmodium falciparum samples; while, the LoD of the RealStar-species assay ranged from 0.09 parasites/µL for P. vivax to two parasites/µL for P. ovale. The time to complete a diagnosis was established in 4 hours. Our findings showed a very good concordance of both assays compared with the reference method, with a very good analytical sensitivity. RealStar-species assay was able to correctly characterize double and triple infections. Therefore, these RealStar assays have shown to be useful tools in malaria diagnosis in non-endemic countries and even endemic countries, and for malaria control in general, detecting low parasitemias with sensitivity similar to the most sensitive methods as nested PCR, but with lower time to get the results. This work was funded by projects PI14CIII/00014 and PI17CIII/00035 from the Instituto de Salud Carlos III (Ministry of Science and Innovation) and cofounded by the European Regional Development Fund. Altona Diagnostics also partially funded this study by donating the kits and funding the necessary consumables. Alexandra Martin Ramirez is supported by an ISCIII Rio Hortega contract. Sí

All U.S.-bound refugees from sub-Saharan Africa receive presumptive antimalarial treatment before departing for the United States. Among U.S.-bound Congolese refugees, breakthrough malaria cases and persistent splenomegaly have been reported. In response, an enhanced malaria diagnostic program was instituted. Here, we report the prevalence of plasmodial infection among 803 U.S.-bound Congolese refugees who received enhanced diagnostics. Infections by either rapid diagnostic test (RDT) or PCR were detected in 187 (23%) refugees, with 78 (10%) by RDT only, 35 (4%) by PCR only, and 74 (9%) by both. Infections identified by PCR included 103 monoinfections (87 Plasmodium falciparum, eight Plasmodium ovale, seven Plasmodium vivax, and one Plasmodium malariae) and six mixed infections. Splenomegaly was associated with malaria detectable by RDT (odds ratio: 1.8, 95% CI: 1.0–3.0), but not by PCR. Splenomegaly was not strongly associated with parasitemia, indicating that active malaria parasitemia is not necessary for splenomegaly.

Laboratory detection of malaria antigens has proved valuable for research and epidemiological purposes. We recently developed a bead-based multiplex antigen assay for pan-Plasmodium and Plasmodium falciparum targets. Here, we report integration of a Plasmodium vivax–specific target to this multiplex panel: P. vivax lactate dehydrogenase (PvLDH). Within the multiplex panel, assay signal for purified PvLDH antigen titrated into the single-digit picogram range. Against a panel of polymerase chain reaction (PCR)-confirmed samples from acute P. vivax infections (n = 36), sensitivity was 91.7% in using PvLDH detection for identifying the presence of parasites. Specificity against a panel of persons with no Plasmodium infection (n = 44) was 100%, and specificity against a panel of PCR-confirmed P. falciparum, Plasmodium malariae, or Plasmodium ovale infections (n = 164) was 90.2%. Addition of this PvLDH capture and detection system into the multiplex antigen panel will now allow for sensitive screening for species identification of both P. falciparum and P. vivax in the laboratory.

Imported malaria in Anhui Province, China, remains a significant public health issue with frequent reporting of severe and fatal cases, partly because of globalization and increased international communication. A retrospective evaluation using surveillance data from 2012 to 2018 was conducted to draw lessons on diagnosis of imported malaria. Epidemiological characteristics, together with diagnostic information, were analyzed using descriptive and comparative statistics. Simultaneously, blinded rechecking of malaria blood slides was performed at general hospitals in Anhui Province in 2018. The results showed that, in their first medical visits, 238 (28.2%) of 844 imported cases were not correctly diagnosed. Notably, the proportion of patients who were misdiagnosed at the first clinic visit was 104/120 (86.7%) at private and village clinics, and 41/81 (50.6%) at primary hospitals. The species identification rates for Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae were 85.2%, 66.7%, 23.2%, and 32.3% (χ(2) = 224, P < 0.001), respectively. Nearly 7% of cases lacked laboratory evidence and were classified as presumed cases. Our findings suggest that physicians and health care providers, especially those at the primary level, lacked the awareness of diagnosing imported malaria. The training of physicians in malaria diagnosis needs to be enhanced. In addition, polymerase chain reactions (previously only carried out at the provincial level) should be performed at municipal CDC for rapid species identification, thereby guiding clinical treatment.

Plasmodium malariae is a neglected malaria parasite. It has wide geographic distribution and, although often associated with mild malaria, is linked to a high burden of anemia and nephrotic syndromes. Here, we report a cohort study conducted in the Kanchanaburi Province of Thailand during May 2013-June 2014 in which P. malariae infection was detected. Of the 812 study participants, two were found to be infected with P. malariae. One had an infection that led to acute malaria, but the other was positive for P. malariae at multiple visits during the study and apparently had chronic asymptomatic infection. Such persistent infection may explain how P. malariae has been able to thrive at very low prevalence and represents a challenge for malaria elimination.

A 63-year-old woman who migrated from Nigeria to the United States was found to have an elevated total serum protein, anemia, and eosinophilia. Serum protein electrophoresis (SPEP) and serum protein immunofixation electrophoresis (SPIFE) demonstrated monoclonal immunoglobulin G (IgG) κ restricted bands (IgG 3,820 mg/dL; κ/λ ratio 4.47), indicative of monoclonal gammopathy of unknown significance (MGUS). A rapid diagnostic test (RDT) for malaria was positive for Plasmodium falciparum (BinaxNOW®; Alere Scarborough Inc., Scarborough, ME). Giemsa-stained blood smears were negative for malarial parasites, however, Loa loa microfilariae were identified. Reverse transcription polymerase chain reaction for P. falciparum, Plasmodium ovale, Plasmodium malariae, and Plasmodium vivax yielded a negative result. She was treated for loiasis with diethylcarbamazine and received no malaria medication. Treatment resulted in a resolution of the microfilaremia and eosinophilia, a negative RDT for malaria, and marked reduction in the monoclonal gammopathy. This is the first reported human case of MGUS associated with loiasis and its resolution after antiparasitic treatment.

The number of Asian migrants working in sub-Saharan developing countries like Angola has been increasing. Their malaria risk, prevention, and care-seeking practices have not been characterized. A cross-sectional survey was conducted in 733 Chinese and Southeast Asian migrants in Angola. Respondents were interviewed and provided blood samples. Samples were analyzed to detect Plasmodium antigen and characterize host anti-Plasmodium response. Positive samples were genotyped using the pfs47 marker. Most respondents (72%; 95% CI: 68-75) reported using bed nets, but less than 1% reported using chemoprophylaxis. Depending on the assay, 1-4% of respondents had evidence of active malaria infection. By contrast, 55% (95% CI: 52-59) were seropositive for Plasmodium antibodies. Most infections were Plasmodium falciparum, but infection and/or exposure to Plasmodium vivax and Plasmodium malariae was also detected. Seroprevalence by time in Angola showed most exposure occurred locally. One respondent had sufficiently high parasitemia for pfs47 genotyping, which showed that the infection was likely locally acquired despite recent travel to home country. Asian migrants to Angola are at substantial risk of malaria. Employers should consider enhanced malaria prevention programs, including chemoprophylaxis; embassies should encourage prevention practices. Angolan healthcare workers should be aware of high malaria exposure in Asian migrants.

While Plasmodium falciparum continues to be the main target for malaria elimination, other Plasmodium species persist in Africa. Their clinical diagnosis is uncommon while rapid diagnostic tests (RDTs), the most widely used malaria diagnostic tool, are only able to distinguish between P. falciparum and non-falciparum species, the latter as ‘pan-species’. Blood samples, both from clinical cases and communites, were collected in southern Nigeria (Lagos and Calabar) in 2017 (October-December) and 2018 (October–November), and analysed by several methods, namely microscopy, quantitative real-time PCR (qPCR), and peptide serology targeting candidate antigens (PmAMA1, PmLDH and PmCSP). The sensitivity of the diagnostic approaches for the dominant P. falciparum were comparable, detecting approx. 80% infection, but not so for non-falciparum species – 3% and 10% infection for P. malariae; 0% and 3% infection for P. ovale by microscopy and qPCR respectively, across communities. P. ovale prevalence was less than 5%. Infection rates for P. malariae varied between age groups, with the highest rates in individuals > 5 years. P. malariae specific seroprevalence rates fluctuated in those < 10 years but generally reached the peak around 20 years of age for all peptides. The heterogeneity and rates of these non-falciparum species calls for increased specific diagnosis and targeting by elimination strategies.

The incidence of an indigenous malaria, defined as malaria acquired by a local mosquito transmission, declined from 2004 to 2015 in the Guangxi Zhuang Autonomous Region. However, imported malaria, defined as malaria acquired from other endemic regions outside of China, has been increasing in the region, as in the rest of the country, particularly the disease caused by Plasmodium falciparum. A retrospective study was conducted to explore malaria-endemic characteristics in Guangxi during the 2004–2015 timeframe; a total of 2,726 confirmed malaria cases were reported, and the majority (90.3%) were due to P. falciparum (N = 1,697 [62.2%]) and Plasmodium vivax (N = 765 [28.1%]). Thirty-four indigenous cases (1.2%) were observed, with no cases of transmission recorded since 2012. Imported P. vivax and Plasmodium ovale infections increased since 2013. The interval between returning to China and the onset of illness was longer for P. vivax and P. ovale infections than for P. falciparum and Plasmodium malariae infections. The difference interval among the species is likely because of the relapse of P. vivax and P. ovale caused by the activation of the latent hypnozoites. Therefore, health clinics should raise awareness and carry out epidemiological studies and follow-up surveys on migrant workers to avoid misdiagnosis and mistreatment. The evaluation of radical treatment should be carried out using a genotyping technology based on glucose-6-phosphate dehydrogenase deficiency levels, and some new drugs active against the hypnozoites should be developed to mitigate malaria in the region.

Important strides have been made within the past decade toward malaria elimination in many regions, and with this progress, the feasibility of eradication is once again under discussion. If the ambitious goal of eradication is to be achieved by 2040, all species of Plasmodium infecting humans will need to be targeted with evidence-based and concerted interventions. In this perspective, the potential barriers to achieving global malaria elimination are discussed with respect to the related diversities in host, parasite, and vector populations. We argue that control strategies need to be reorientated from a sequential attack on each species, dominated by Plasmodium falciparum to one that targets all species in parallel. A set of research themes is proposed to mitigate the potential setbacks on the pathway to a malaria-free world.

The occurrence of Plasmodium vivax malaria was reported in Nouakchott, Mauritania in the 1990s. Several studies have suggested the frequent occurrence of P. vivax malaria among Nouakchott residents, including those without recent travel history to the southern part of the country where malaria is known to be endemic. To further consolidate the evidence for P. vivax endemicity and the extent of malaria burden in one district in the city of Nouakchott, febrile illnesses were monitored in 2012-2013 in the Teyarett health center. The number of laboratory-confirmed P. vivax cases has attained more than 2,000 cases in 2013. Malaria transmission occurs locally, and P. vivax is diagnosed throughout the year. Plasmodium vivax malaria is endemic in Nouakchott and largely predominates over Plasmodium falciparum. Malaria has been known to be endemic, with occasional and sometimes deadly epidemics, in the Sahelian southern Mauritania, bordering Senegal and Mali, two West African countries where malaria has been endemic for centuries. 1 In one of the first epidemiological studies on malaria conducted during the colonial period in 1945-1946 along the Senegal River that forms a natural boundary between Senegal and Mauritania, Plasmodium falciparum (133 of 180 positive smears, 74%) largely predominated over Plasmodium vivax (8%) and Plasmodium malariae (18%). 2 The primary vector was reported to be Anopheles gambiae sensu lato in that study. However, two further studies conducted in southern Mauritania in the 1960s did not confirm the presence of P. vivax, and of the two human malaria species found, P. falciparum largely predominated over P. malariae. 3,4 The

International audience; Accurate information regarding malaria prevalence at national level is required to design and assess malaria control/elimination efforts. Although many comparisons of microscopy and polymerase chain reaction (PCR)-based methods have been conducted, there is little published literature covering such comparisons in southeast Asia especially at the national level. Both microscopic examination and PCR detection were performed on blood films and dried blood spots samples collected from 8,067 individuals enrolled in a nationwide, stratified, multistage, cluster sampling malaria prevalence survey conducted in Cambodia in 2007. The overall malaria prevalence and prevalence rates of Plasmodium falciparum, Plasmodium vivax, and Plasmodium malariae infections estimated by microscopy (N = 8,067) were 2.74% (95% confidence interval [CI]: 2.39-3.12%), 1.81% (95% CI: 1.53-2.13%), 1.14% (95% CI: 0.92-1.40%), and 0.01% (95% CI: 0.003-0.07%), respectively. The overall malaria prevalence based on PCR detection (N = 7,718) was almost 2.5-fold higher (6.31%, 95% CI: 5.76-6.89%, P < 0.00001). This difference was significantly more pronounced for P. falciparum (4.40%, 95% CI: 3.95-4.90%, P < 0.00001) compared with P. vivax (1.89%, 95% CI: 1.60-2.22%, P < 0.001) and P. malariae infections (0.22%, 95% CI: 0.13-0.35%, P < 0.0001). The significant proportion of microscopy-negative but PCR-positive individuals (289/7,491, 3.85%) suggest microscopic examination frequently underestimated malaria infections and that active case detection based on microscopy may miss a significant reservoir of infection, especially in low-transmission settings.

Recent reports of reductions in malaria transmission in several African countries have resulted in optimism that malaria can be eliminated in parts of Africa where it is currently endemic. It is not known whether these trends are global or whether they are also present in areas where political instability has hindered effective malaria control. We determined malaria parasite carriage and age-dependent antibody responses to Plasmodium falciparum antigens in cross-sectional surveys in Apac, northern Uganda that was affected by political unrest. Under-five parasite prevalence was 55.8% (115/206) by microscopy and 71.9% (41/57) by polymerase chain reaction. Plasmodium ovale alone, or as a co-infection, was detected in 8.6% (12/139) and Plasmodium malariae in 4.3% (6/139) of the infections. Age seroprevalence curves gave no indication of recent changes in malaria transmission intensity. Malaria control remains a tremendous challenge in areas that have not benefited from large-scale interventions, illustrated here by the district of Apac.

The merozoite surface protein 1 (MSP1) is the principal surface antigen of the blood stage form of the Plasmodium parasite. Antibodies recognizing MSP1 are frequently detected following Plasmodium infection, making this protein a significant component of malaria vaccines and diagnostic tests. Although the MSP1 gene sequence has been reported for Plasmodium falciparum and Plasmodium vivax, this gene has not been identified for the other two major human-infectious species, Plasmodium malariae and Plasmodium ovale. MSP1 genes from these two species were isolated from Cameroon blood donor samples. The genes are similar in size to known MSP1 genes and encode proteins with interspecies conserved domains homologous to those identified in other Plasmodium species. Sequence and phylogenetic analysis of all available Plasmodium MSP1 amino acid sequences clearly shows that the Po and Pm MSP1 sequences are truly unique within the Plasmodium genus and not simply Pf or Pv variants.

We report the results of clinical studies carried out at six sites in Madagascar, between January and October 2006. The aims were (i) to update our knowledge of the burden of Plasmodium malariae infection and (ii) to assess the therapeutic efficacy of chloroquine for uncomplicated quartan malaria. Our findings confirm that P. malariae is the third leading cause of malaria, accounting for 1.1% of all malarial infections. They also demonstrate that chlo- roquine—currently recommended for the home management of presumed malaria in children under the age of five years and commonly used by adults—remains highly effective in patients with uncomplicated P. malariae infection. Plasmodium malariae, one of the four species of Plasmo- dium affecting humans, is found in tropical and subtropical regions, often in sympatry with other Plasmodium species, as in Madagascar. Its reported prevalence varies from less than 4% to more than 20% in endemic regions. 1-4 No accurate estimate of the prevalence of P. malariae infection worldwide is currently available, but it has been calculated that there are probably at least 60 million infections per year, based on the prevalence of P. falciparum 5,6 and known underestimation of the prevalence of P. malariae. 7,8 The clinical features associ- ated with febrile bouts of P. malariae are generally milder than those caused by other species. 9 Fever displays quartan (4-day) periodicity, parasite density is usually considerably below 1000 parasites per ml of blood, and infection is rarely life-threatening in the absence of complications, such as neph

Item does not contain fulltext Haptoglobin (Hp) levels were investigated in relation to host genotype in a malaria-endemic area in Gabon. A cross-sectional study of 1-12-year-old children was conducted in the rainy season, a period of high malaria transmission, to examine this relationship. Variables that influenced Hp levels were Hp genotype, location, and age interacting with parasite density. At low parasite densities, there was a negative correlation between Hp levels and age. At higher densities, there was a positive correlation with age. This suggests that in the presence of greater parasite-induced hemolysis, older children are capable of increased production of Hp. Sickle cell trait and ABO blood group was not associated with Hp levels in this population.

We analyzed records of malaria therapy patients sequentially or simultaneously inoculated with Plasmodium falciparum and Plasmodium malariae. Gametocyte production was enhanced in P. falciparum by prior or concurrent P. malariae infection but diminished or unaffected in P. malariae by P. falciparum. Conversely, asexual-form production was diminished in P. malariae but unaffected in P. falciparum.

A retrospective examination was made of archival data on the response of Plasmodium malariae infections in humans to chloroquine. The clearance time for P. malariae was longer than that for P. falciparum and P. vivax. Of 100 P. malariae-infected patients treated with 1,500 mg of chloroquine given over 3 days, 15 had detectable parasites for 7 days, 4 for 10 days, and 1 for 15 days after treatment. Of 17 patients treated intramuscularly with 450 mg of dihydrochloroquine, parasites persisted in 1 patient for 11 days. Of patients with chloroquine-sensitive P. falciparum. 44 cleared parasites by 6 days after treatment; 37 patients with P. vivax infections cleared parasites by day 5. The confirmation of chloroquine resistance may depend on the adaptation of isolates to nonhuman primates in which controlled drug trials can be made.

In an area of Papua New Guinea with high prevalence of Plasmodium falciparum (39.6%), Plasmodium vivax (18.3%), and Plasmodium malariae (13.8%), cross-sectional analysis found P. falciparum infection to be independent of the other species despite heterogeneities in transmission. Plasmodium vivax and P. malariae infections were negatively correlated. Plasmodium malariae infection was positively associated with homologous infection four months previously and with prior P. falciparum, but not P. vivax infection. There were no other indications that any Plasmodium species protected against heterologous infection. Prospective analysis of health-center morbidity supported the idea that P. malariae infection protects against disease, but indicated greater protection against non-malaria than P. falciparum-associated fevers. Plasmodium vivax appeared to protect against P. falciparum disease but not against other forms of morbidity. Covariate adjustment had considerable effects on estimated relationships between species, and confounding variables may account for many differences among reports of inter-species interactions in human malaria.

The OptiMAL assay, a new immunochromatographic "dipstick" test for malaria based on detection of Plasmodium lactate dehydrogenase (pLDH), is purported to detect infections of approximately 200 parasites/microL of blood and to differentiate between Plasmodium falciparum and non-P. falciparum. We evaluated OptiMAL performance by comparing the test strip interpretations of two independent readers with consensus results obtained independently by expert malaria microscopists. Unbiased measures of sensitivity were derived by applying the OptiMAL test for detection and differentiation of light, asymptomatic infections by P. falciparum and Plasmodium vivax. OptiMAL readings were separated in time to determine whether the reaction signal was stable. Microscopy identified infections in 225 of 505 individuals screened; those with P. falciparum (n = 170) averaged 354 asexual forms/microL and P. vivax/Plasmodium malariae (n = 112) averaged 216 asexual forms/microL of blood. Concordance between OptiMAL and microscopy was 81% and 78% by the two independent readings. The assay's sensitivity for detection of any malaria species was 60.4% and 70.2% respectively and specificity was 97% and 89%. Most cases identified by microscopy as P. falciparum were graded as negative or non-falciparum by both OptiMAL readers. OptiMAL false negatives as well as misidentifications were related to low parasitemias (< 500/microL). The OptiMAL assay demonstrated 88-92% sensitivity for detecting infections of 500-1,000 parasites/microL, a range covering the mean parasitemia of primary symptomatic P. falciparum infections in malaria-naive Indonesian transmigrants. This device was markedly less sensitive than expert microscopy for discriminating between malaria species and is presently unsuited for use as an epidemiological screening tool. The OptiMAL assay is not approved for diagnostic use but is commercially available for research purposes only.

A retrospective examination was made to determine parasitemia and episodes of fever in 97 patients, previously infected with Plasmodium malariae, P. ovale, and/or P. vivax, who were reinfected with P. falciparum for treatment of neurosyphilis, the standard treatment at the time. Data were collected at the National Institutes of Health laboratories in Columbia, South Carolina and Milledgeville, Georgia during the period 1940 to 1963. Results were compared with observations recorded for patients following primary infection with P. falciparum. The mean daily percentage of patients with fever > or = 101 degrees F during the first 20 days of primary infection with P. falciparum was 42.4; the percentage with fever > or = 104 degrees F was 19.9%. Those previously infected with P. ovale, P. vivax, and P. malariae had mean daily percentages of fever > or = 101 degrees F and > or = 104 degrees F of 39.1% and 14.8%, 39.1% and 19.4%, and 28.4%, and 11.3%, respectively. Previous infection with P. ovale or P. vivax had little, if any, effect on subsequent clinical malaria due to P. falciparum, whereas infection with P. malariae resulted in reduced frequencies of fever. A similar comparison was made for parasite counts > or = 1,000/microl and > 10,000/microl. The percentages for 268 patients during the first 20 days of primary infection with P. falciparum parasite counts > or = 1,000/microl and > or = 10,000/microl were 58.2% and 29.9%, respectively. Those previously infected with P. ovale, P. vivax, and P. malariae had mean daily percentages of parasitemia > or = 1,000/microl and > or = 10,000/microl of 58.0% and 24.3%, 57.3% and 31.1%, and 45.9% and 19.0%, respectively. Previous infection with P. malariae resulted in a reduction in the frequency of high-density parasitemia (> or = 10,000/microl) as well as an asexual parasite count > or = 1,000/microl. These results suggest that P. falciparum and P. malariae share common antigens that are able to induce parasitologic and clinical protection when infection with P. falciparum follows that with P. malariae. The results did not suggest that protection to P. falciparum is provided by previous infection with P. ovale or P. vivax.

The frequency of cytokine-producing peripheral blood mononuclear cells was assessed in 28 subjects with microfilaremic loiasis and in 14 amicrofilaremic individuals. In addition, a subgroup of seven microfilaremic individuals coinfected with Plasmodium malariae was evaluated. By using flow cytometry for the intracellular detection of cytokines, a more pronounced T helper (Th)2 cell-type response with the expansion of interleukin (IL)-4, IL-10, and IL-13 expressing CD4+ cells in the microfilaremic compared with the amicrofilaremic group was noted. Expression of IL-5 was equivalent in both groups as was the frequency of Th2-type cytokines expressing CD8+ cells and of Th1-type cytokines (interferon [IFN]-gamma, IL-2, IFN-gamma/IL-2) producing CD4+ and CD8+ cells. Th0-type cytokine-expressing cells, represented by IL-4/IFN-gamma, IL-10/IFN-gamma, and IL-13/IFN-gamma, were equally distributed within groups. Coinfection of P. malariae did not significantly alter the cytokine expression compared with microfilaremic individuals without P. malariae infections. By identifying a large panel of cytokine-producing T cell subpopulations, a Th2-driven immune response in microfilaremic Loa loa patients was noted.

The International Center for Medical Research (CIRMF) is located in an area highly endemic for malaria in southeastern Gabon, where humans and apes (gorillas and chimpanzees) are living in the same geographic area. The presence of the CIRMF primate center housing apes (59 chimpanzees and nine gorillas in 1994) within the city of Franceville provided an opportunity to investigate the capability of cross-transmission of malaria species from humans to apes. The main vector of human malaria, Anopheles gambiae, was found in the primate center and in a nearby populated area of Franceville. Despite high malaria transmission in humans of both Plasmodium falciparum and P. malariae (mean of 43% cumulative prevalence in schoolchildren), none of the apes were found infected with plasmodia during a six-month investigation. However, low antibody levels against sporozoite and blood stages of both P. falciparum and P. malariae were detected in a few chimpanzees and gorillas. These results demonstrate that only rarely would apes be bitten in the field by mosquitoes infected with human malaria parasites. In the case of infection proven by serology, we did not find any evidence that blood-stage malaria parasites were able to the gametocyte stage. The absence of any established malaria transmission cycle within the primate colony of CIRMF indicates that apes cannot be considered as animal reservoirs for human malaria parasites in this environment.

Twenty-eight nonimmune patients with acute uncomplicated falciparum malaria returning from subSaharan Africa were treated with a micronized formulation of halofantrine hydrochloride (three doses of 250 mg at 6-hr intervals) to investigate the drug's efficacy, tolerance, and pharmacokinetics. In vitro drug susceptibility patterns were determined by the isotopic semimicrotest. Twenty-four of 28 patients were cured. Two of the four patients experiencing recrudescence were associated with low absorption of the drug and parasites susceptible in vitro to halofantrine. The other two patients had adequate plasma concentrations of halofantrine and its main human metabolite, N-desbutylhalofantrine, but the isolates were also resistant in vitro to the drugs, suggesting drug resistance as the cause of treatment failure. Only mild, transitory side effects were noted. A wide interindividual variation in plasma concentrations of halofantrine and its metabolite was observed. Pharmacokinetic studies suggested that the micronized formulation of halofantrine hydrochloride may not increase drug absorption considerably. Further studies using higher doses or longer treatment periods are needed to ensure that adequate plasma concentrations of the drug are used.

The pathogenesis of renal diseases associated with Plasmodium malariae infections is still not fully understood. The present work is concerned with the infection caused by P. inui in the rhesus monkey Macaca mulatta as a potential model for human quartan malaria, which the monkey parasite resembles in morphology and schizogonic behavior. Various aspects of the disease were studied. Changes in the levels of serum complement components C3 and C4 indicate activation of complement through the clas sical pathway. A few days after infection, IgG antibody titers increased, coinciding with low levels of parasitemia, which suggests that some of these antibodies are protective. Immunofluorescence testing of kidney tissue showed a predominance of 1gM antibodies over IgG, C3, C4, albumin, and fibrinogen, which was detected in a number of the infected monkeys. These findings were consistent with those seen in humans with P. malariae infectionand indicatethattheP. inui/rhesusmonkey model islikelytobe appropriatefor the study of different aspects of quartan malaria. Since Hendrickse and Gilles suggested that the nephrotic syndrome associated with malaria might be due to kidney damage following an immunologic reaction to Plasmodium malariae,' evidence has accumulated from several studies to support this view.2@ This evidence was based either on serologic studies (complement, parasite antigen or antibody) or on immunohistochemical investigations of tissue lesions associated with the infection. Studies of the renal biopsies of subjects in fected with P. malariae by fluorescence micros copy have demonstrated the presence of IgG, 1gM, and complement components deposited along the glomerular basement membrane and the capillary walls.2” Experimental work in the past has been hindered by the lack of a suitable animal model. However, studies using rhesus monkeys infected with P. cynomolgi showed that soluble immune complexes developed in the kidneys of animals during the course of infec tion.7-8 This provided an animal model that seemed to be an experimental counterpart for the renal complication of human quartan malaria. Aotus monkeys infected with either P. malariae or P. brasilianum have been used to study the immunopathology of the nephroticsyndrome.5-6 Since Aotus monkeys are scarce, another model system is urgently needed. One of the major sys tems that gives highly predictable results is Ma caca mulanaiP. inui.9 It is particularly important to mention that P. inui is a natural parasite of the rhesus monkey (M. mulatta), causing a low grade chronic infection.

Five Aotus monkeys and two chimpanzees were infected with Plasmodium malariae isolated from a patient who acquired her infection approximately 50 years ago. All animals were splenectomized. The chimpanzees supported the highest parasite densities of 22,271/microliters and 18,544/microliters. Three Aotus monkeys with a previous history of infection with P. vivax had maximum parasite counts of from 1,818/microliters to 2,909/microliters, whereas two monkeys not previously infected had maximum parasite counts of 6,908/microliters. The establishment of new isolates in these animals aides the development of diagnostic probes and the identification of areas of antigenic variation within the species.

We have characterized the circumsporozoite (CS) gene sequences of Plasmodium malariae China-1 CDC, isolated recently from a person who was infected 50 years ago in China, and P. vivax Chesson, isolated 48 years ago from a patient who had returned from New Guinea. These protein sequences were compared with the CS protein sequences of recently isolated P. vivax and P. malariae parasites. In a similar manner, we compared the previously characterized CS protein gene of P. falciparum clone 7G8, derived from a Brazilian isolate collected in 1980, with the CS protein genes of recent P. falciparum field isolates. In the case of the P. malariae CS protein gene, with the exception of an additional copy of major (NAAG) and minor (NDAG) repeat sequences and the presence of one copy of NDEG sequence, the China-1 CDC P. malariae parasite is similar to the Uganda-1 CDC isolate of 1982. In the nonrepeat region, changes were noted in two amino acid residues, one of which is also seen in a closely related monkey malaria parasite, P. brasilianum. In the case of P. vivax CS proteins, the nonrepeat region of the protein in Chesson strain shares identity with nearly 71% of the CS clones characterized from field isolates. In the P. falciparum CS proteins, the 7G8 CS protein sequence is identical to 75% of the genes of recent field isolates in the Th1R-N1 region. In the Th2R and Th3R regions, 34% and 55% of the CS clones analyzed, respectively, had changes at two amino acid residues.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of alpha(+)-thalassemia on malaria in pregnancy was assessed in a cross-sectional study of 530 women in Ghana. Plasmodial infections, alpha(+)-thalassemia, serum levels of C-reactive protein, and antimalarial drugs in urine were determined. The alpha-globin genotypes did not correlate with the prevalence of Plasmodium falciparum-infection and parasite densities. However, Plasmodium malariae tended to be more frequent in alpha(+)-thalassemic women (P = 0.05). Excluding women with residual antimalarials, a significant excess of P. malariae was observed in alpha(+)-thalassemic individuals. Febrile responses (P = 0.05) and inflammation (CRP > 0.6 mg/dl, P = 0.06) appeared to be less common in infected alpha(+)-thalassemic women and were also comparatively rare in parasitemic individuals who harbored double species infections with P. falciparum and P. malariae. Plasmodium malariae may influence the pathogenesis of falciparum malaria leading to a low prevalence of inflammation and febrile responses in alpha(+)-thalassemic women.

The effect of iron therapy on malarial infection was investigated in Papua New Guinea, where malaria is endemic. Prepubescent schoolchildren with hemoglobin levels of 8-12 g/dl were randomly assigned to receive either 200 mg ferrous sulfate or a placebo twice daily for 16 weeks. Iron status and malarial infection were assessed at baseline, after 6 and 16 weeks of therapy, and 8 weeks after therapy was discontinued. Iron status was significantly improved by the treatment. The treatment did not significantly affect parasite rate, parasite density, or levels of anti-malarial IgG. No changes in spleen size were observed in either group. Furthermore, there was no significant difference between the groups in reported episodes of suspected malaria during the therapy. These results suggest that, in malaria endemic areas, oral treatment for iron deficiency can be carried out in semi-immune or immune schoolchildren without adverse consequences.

This is the first reported case of congenital double malaria infection. In San Francisco, California, a 6-week-old infant presented with Plasmodium vivax and P. malariae infections. Although the child had not traveled, the mother had recently immigrated from an area north of Bombay, India. Reasons for the delay in onset of the infant's symptoms are given.

A method consisting of filtration of up to 100 macerated mosquitoes in a batch, followed by fixation with glutaraldehyde and concentration of filtrate by centrifugation has been developed to rapidly assess malaria infection in anopheline mosquitoes. Determination of the presence of sporozoites is made by observation of a sample of the final filtrate with a phase microscope. The method is simple and field adaptable, essential factors for the application of any technique to large scale field operations. Application of the technique in El Gancho, Chiapas, Mexico, in February 1984 yielded an infection rate for Anopheles albimanus of 0.9% for intradomicile-collected human bait mosquitoes and 0.1% for peridomicile-collected human bait mosquitoes.

We conducted a cross-sectional study to determine the serological response to malaria in an HIV-1 infected population and in a control population in a region of high malaria transmission. The study group consisted of 66 hospitalized patients with clinical acquired immunodeficiency syndrome (AIDS) and 70 trauma patients without clinical AIDS (controls). Mean optical densities of antibody produced against RESA-4, RESA-8, RESA-11, (PNAN)5 and (NAAG)5 synthetic peptides of Plasmodium falciparum were compared between HIV-1 seropositive and HIV-1 seronegative patients using non-parametric statistics. HIV-1 seropositive patients with clinical AIDS had significantly less antibody to the synthetic P. falciparum ring stage peptide, RESA-8 (P = 0.001), than a comparable group of seronegative patients. Antibody levels were also low for the other ring stage peptides, RESA-4 (P = 0.024) and RESA-11 (P = 0.024). Although not statistically significant, antibody levels among the HIV-1 seropositive trauma patients were higher than among the HIV-1 seronegative trauma patients. During HIV-1 infection, a polyclonal B cell activation may occur as noted in the HIV-1 seropositive trauma patients, but with increased immunosuppression in advanced clinical AIDS, B cell stimulation appears to be diminished. This results in decreased production of malaria antibody.

From a representative sampling of several remote populations living on the Banks and Torres Islands (New Hebrides), the Eastern and Southern Districts of the Solomon Islands, the Western Caroline Islands (U. S. Pacific Trust Territory), West New Guinea (Indonesia), and Papua New Guinea, 752 sera were examined for fluorescent antibodies to the four species of human malaria, and the results were compared to already published parasite survey data based on blood smears and medical examinations. Antibody prevalence data confirmed the presence of significant endemic malaria among most of the visited islands in the New Hebrides, and a variable but smaller amount of malaria in the Solomons. On those islands known to be free of malarial vectors, data were compatible with importation of self-limited infection by travelling residents. Malarial infection occurred in from 40% to 100% of the New Guinea villages that were visited, and was entirely absent from the Western Caroline Islands. The actual proportions of malarial species in endemic areas were not accurately reflected by relative antibody titer levels to the different species, possibly due to unpredictably high heterologous antibody reactions following multiple mixed infections.

Enzyme-linked immunosorbent assays (ELISAs) for the circumsporozoite (CS) antigens of Plasmodium falciparum, P. malariae, and P. ovale were used to identify species of sporozoite and oocyst infections detected by dissection in Anopheles gambiae s.l. and An. funestus collected in western Kenya. ELISAs identified 92.5% of 1,113 salivary gland infections; Plasmodium species infections included 79.4% P. falciparum, 3.2% P. malariae, 1.7% P. ovale, and 2 or more Plasmodium species were detected in 15.7% of the Anopheles in which the species of parasite was identified. Identification was more likely with greater numbers of sporozoites observed in dissections, increasing from 65% ELISA positivity in mosquitoes with 1–10 sporozoites in their salivary glands to 96% in mosquitoes with over 1,000 sporozoites. ELISAs detected CS antigen in 66% of 294 Anopheles that by dissection had oocysts but uninfected salivary glands. Of 112 Anopheles with a single species of Plasmodium detected in the salivary glands, 29 (25.9%) had 1 or more additional species detected in the midgut, indicating a high potential for multiple infections. Similar proportions of Plasmodium species were found in An. gambiae s.l. and An. funestus.

An outbreak of Plasmodium malariae malaria occurred in Grenada some 16 years after the end of a malaria eradication campaign, probably due to renewal of transmission from recrudescent cases. Serological studies were used in addition to blood film surveys in defining the outbreak, and their value in such surveillance situations is emphasized.

The status of the available data regarding the transmission of the Plasmodium malariae has recently been critically reviewed by Gordon and Davey (1), who point out that the only satisfactory record is the report by Stephens and Christopher (2) of gland infection obtained in two of six A. culicifacies fed on four persons with quartan malaria in India. The evaluation of the records in the literature made by Gordon and Davey was based on the following criteria: (a) The mosquitoes used must have been laboratory bred, or obtained in a district free from any suspicion of malaria; (b) sporozoite infection of the salivary glands must have been obtained; (c) great care must have been taken to exclude the possibility of mixed infection in the host. With the exception noted, they reject all recorded claims to successful transmission of P. malariae by anophelines, and express surprise that the various claims should rest on such a small basis of fact.

Summary There have been presented findings obtained from the study of serial reticulocyte preparations of the peripheral blood made during described periods in three falciparum and two malariae infections. The total numbers of mature erythrocytes infected with P. falciparum constantly exceeded the total numbers of parasitized reticulocytes. Infected mature erythrocytes were found on all occasions; infected reticulocytes were observed in only 70 per cent of instances. The two types of host cell alternated irregularly in exhibiting the higher rate of infection. Correlations between the findings and the stage of the disease process were not discernible. P. malariae, on all occasions, was found in mature erythrocytes in both greater absolute and relative numbers than in reticulocytes. The incidence of infection of the immature erythrocytes by this parasite was extremely low.

It now appears that Plasmodium cynomolgi, Plasmodium knowlesi, Plasmodium inui, and Plasmodium schwetzi are true zoonoses, although the latter, as Plasmodium ovale, may be an anthroponosis as well. Plasmodium malariae and Plasmodium rodhaini are generally accepted as being synonymous; if this is true, and it probably is, then this African quartan parasite is either one, i.e., a zoonosis or an anthroponosis, depending on which group of primates gave it origin. Certain African-Asian forms, Plasmodium gonderi for example, appear to be neither. The Central and South American primate malarias pose a different problem, for it is held that these malarias appeared only after 1492 when man, carrying P. malariae and Plasmodium vivax invaded this area from Europe. Consequently, each infection appeared in the monkeys as an anthroponosis. If this is true, synonymy is inevitable. If, on the other hand, Plasmodium brasilianum is a valid species, it acts as a zoonosis. There is reasonable doubt that Plasmodium simium acts in the same capacity.

Summary and Conclusions Field trials in British Guiana in 1946 showed that metachloridine at doses of 1 to 2 grams weekly, divided into 2, 3 or 5 parts, completely suppressed natural infections of P. malariae and partially suppressed parasitemia with P. falciparum. Limited data indicate good suppression of P. vivax. No toxicity was seen during the treatment period of 6 months. Lower doses should be tried to determine the minimum effective dose for the suppression of P. malariae and higher doses should be tried for the same purpose in infections with P. falciparum. The ability of metachloridine to suppress clinical symptoms of infections with P. falciparum should be determined.

Studies on the prevalence and etiology of splenomegaly were accomplished at three hamlets of a geographically remote village in South Vietnam. The percent of children and adolescents with enlarged spleen ranged from 70 to 90. Single or mixed malaria infections were demonstrated in 19 of 42 splenomegalic children. The results indicated that malaria infections were the primary cause for splenomegaly in those examined, although the beta-thalassemia trait was not excluded as a contributory factor.

VII. Summary 1. The literature Plasmodium lenue criteria: (i) Unusually ameboid form. (ii) Scanty cytoplasm. (iii) Abundant, irregular nuclear chromatin, as first grouped by Stephens (11) may be exhibited by any of the three well-known species of malaria parasites but more often by Plasmodium vivax and Plasmodium falciparum than by Plasmodium malariae. The cause of these deviations from what have been the commonly accepted characters of a well-behaved parasite of the accepted species is not known, but three classes of answers to this question are to be found in the literature. (a) Deviations of this particular sort represent a new and distinct species called Plasmodium tenue by Stephens. (b) An extracellular position of the parasite, as either the usual or occasional event, makes manipulations, or malnourishment, or the action of the chemical substances in the blood, factors in producing atypical morphology in the three commonly accepted species. (c) Unusual variation in the blood complex due to the interplay of factors such as environment, medication, health or ill-health of host, and similar influences, is reflected in an unusual morphology of the parasites of the three commonly accepted species. 2. The case reported A case is presented of a negro girl, aged three, always resident in Georgia, U. S. A., whose blood examined at weekly intervals over a period of a year, repeatedly revealed typical Plasmodium vivax and Plasmodium falciparum parasites. In addition to these typical forms, there were seen occasionally attenuated forms having the characters of Stephens' (11) and Sinton's (37) Plasmodium tenue. The fact that these tenue forms appeared at intervals over a period of a year, and that their appearance and disappearance can not be correlated with any external factor might perhaps be an argument in favor of new species. But on the other hand the fact that the tenue forms were seen in the same smears as typical young and mature Plasmodium vivax and Plasmodium falciparum parasites, that no unusual mature forms were seen, that no unusual forms or activity were seen in fresh blood mears,—all of these observations would seem to indicate that these tenue forms belonged to either Plasmodium falciparum or Plasmodium vivax or both.