Showing papers on "Plasmodium vivax published in 2003"
TL;DR: The overall midgut bacterial infection in mosquito field populations may influence P. vivax transmission, and could contribute to explain the annual variations in malaria incidence observed in the area.
Abstract: Bacterial infections were investigated in midguts of insectary and field-collected Anopheles albimanus Weidemann from southern Mexico. Serratia marcescens, Enterobacter cloacae and Enterobacter amnigenus 2, Enterobacter sp., and Serratia sp. were isolated in field samples obtained in 1998, but only Enterobacter sp. was recovered in field samples of 1997 and no bacteria were isolated from insectary specimens. These bacteria were offered along with Plasmodium vivax infected blood to aseptic insectary An. albimanus, and the number of infected mosquitoes as well as the oocyst densities assessed after 7d. Plasmodium vivax infections in mosquitoes co-infected with En. amnigenus 2, En. cloacae, and S. marcensces were 53, 17, and 210 times, respectively, lower than in control mosquitoes, and the mean oocyst density in mosquitoes co-infected with En. cloacae was 2.5 times lower than in controls. Mortality was 13 times higher in S. marcensces-infected mosquitoes compared with controls. The overall midgut bacterial infection in mosquito field populations may influence P. vivax transmission, and could contribute to explain the annual variations in malaria incidence observed in the area.
235 citations
TL;DR: A new, rapid assay, based on a single-round, multiplex PCR, which targets the conserved 18S small-subunit RNA genes of the parasites, not only permits a malarial infection to be detected but also allows each Plasmodium species present to be identified, even in cases of mixed infection.
Abstract: A new, rapid assay, based on a single-round, multiplex PCR, can be used to detect Plasmodium falciparum, P. vivax, P. malariae or P. ovale in human blood. The PCR, which targets the conserved 18S small-subunit RNA genes of the parasites, not only permits a malarial infection to be detected but also allows each Plasmodium species present to be identified, even in cases of mixed infection.
189 citations
TL;DR: Papua New Guinea is a patchwork of different ecological zones, inhabited by human populations of exceptional cultural and linguistic diversity, which results in complex variations in vector ecology and malaria epidemiology, and a prime location for studies of interactions between different parasite species.
176 citations
TL;DR: Research is urgently needed to gauge the problem and to determine the safety, tolerability and efficacy of shorter courses and higher doses of PQ, the only drug available to eliminate hypnozoites in malaria.
171 citations
TL;DR: More than one third of malaria-infected travelers, the illness developed more than two months after their return, suggesting agents that act on the liver phase of malaria parasites are needed for more effective prevention of malaria in travelers.
Abstract: Background Most antimalarial agents used by travelers act on the parasite's blood stage and therefore do not prevent late-onset illness, particularly that due to species that cause relapsing malaria. We examined the magnitude of this problem among Israeli and American travelers. Methods We examined malaria surveillance data from Israel and the United States to determine the traveler's destination, the infecting species, the type of chemoprophylaxis used, and the incubation period. Results In Israel, from 1994 through 1999, there were 300 cases of malaria among returning travelers in which one species of plasmodium could be identified. In 134 of these cases (44.7 percent), the illness developed more than two months after the traveler's return; nearly all of these cases were due to infection with Plasmodium vivax or P. ovale. In 108 of the 134 cases (80.6 percent), the patient had used an antimalarial regimen according to national guidelines. In the United States, from 1992 through 1998, there were 2822 cas...
162 citations
TL;DR: Results strongly indicate that P. vivax populations are highly diverse and multiple clonal infections are common in this malaria-hypoendemic region of Thailand.
Abstract: Using two polymorphic genetic markers, the merozoite surface protein-3alpha (MSP-3alpha) and the circumsporozoite protein (CSP), we investigated the population diversity of Plasmodium vivax in Mae Sod, Thailand from April 2000 through June 2001. Genotyping the parasites isolated from 90 malaria patients attending two local clinics for the dimorphic CSP gene revealed that the majority of the parasites (77%) were the VK210 type. Genotyping the MSP3-alpha gene indicated that P. vivax populations exhibited an equally high level of polymorphism as those from Papua New Guinea, a hyperendemic region. Based on the length of polymerase chain reaction products, three major types of the MSP-3alpha locus were distinguished, with frequencies of 74.8%, 18.7%, and 6.5%, respectively. The 13 alleles distinguished by restriction fragment length polymorphism analysis did not show a significant seasonal variation in frequency. Genotyping the MSP-3alpha and CSP genes showed that 19.3% and 25.6% of the patients had multiple infections, respectively, and the combined rate was 35.6%. Comparisons of MSP-3alpha sequences from nine clones further confirmed the high level of genetic diversity of the parasite and also suggested that geographic isolation may exist. These results strongly indicate that P. vivax populations are highly diverse and multiple clonal infections are common in this malaria-hypoendemic region of Thailand.
139 citations
TL;DR: The clinical, epidemiological, and sequence data suggest a sequential pathway for the acquisition of the P. vivax dhfr mutations, which are associated with resistance to the antifolate antimalarial drugs.
Abstract: Mutations in the dihydrofolate reductase (dhfr) genes of Plasmodium falciparum and P. vivax are associated with resistance to the antifolate antimalarial drugs. P. vivax dhfr sequences were obtained from 55 P. vivax isolates (isolates Belem and Sal 1, which are established lines originating from Latin America, and isolates from patient samples from Thailand [n = 44], India [n = 5], Iran [n = 2], and Madagascar [n = 2]) by direct sequencing of both strands of the purified PCR product and were compared to the P. vivax dhfr sequence from a P. vivax parasite isolated in Pakistan (isolate ARI/Pakistan), considered to represent the wild-type sequence. In total, 144 P. vivax dhfr mutations were found at only 12 positions, of which 4 have not been described previously. An F→L mutation at residue 57 had been observed previously, but a novel codon (TTA) resulted in a mutation in seven of the nine mutated variant sequences. A new mutation at residue 117 resulted in S→T (S→N has been described previously). These two variants are the same as those observed in the P. falciparum dhfr gene at residue 108, where they are associated with different levels of antifolate resistance. Two novel mutations, I→L at residue 13 and T→M at residue 61, appear to be unique to P. vivax. The clinical, epidemiological, and sequence data suggest a sequential pathway for the acquisition of the P. vivax dhfr mutations. Mutations at residues 117 and 58 arise first when drug pressure is applied. Highly mutated genes carry the S→T rather than the S→N mutation at residue 117. Mutations at residues 57 and 61 then occur, followed by a fifth mutation at residue 13.
134 citations
TL;DR: A survey of polymorphism in a malaria-endemic population shows that nucleotide alleles in eba-175 region II occur at more intermediate frequencies than expected under neutrality, but polymorphisms in the homologous domains of two closely related genes show an opposite trend.
Abstract: Malaria parasite antigens involved in erythrocyte invasion are primary vaccine candidates The erythrocyte-binding antigen 175K (EBA-175) of Plasmodium falciparum binds to glycophorin A on the human erythrocyte surface via an N-terminal cysteine-rich region (termed region II) and is a target of antibody responses A survey of polymorphism in a malaria-endemic population shows that nucleotide alleles in eba-175 region II occur at more intermediate frequencies than expected under neutrality, but polymorphisms in the homologous domains of two closely related genes, eba-140 (encoding a second erythrocyte-binding protein) and psieba-165 (a putative pseudogene), show an opposite trend McDonald-Kreitman tests employing interspecific comparison with the orthologous genes in P reichenowi (a closely related parasite of chimpanzees) reveal a significant excess of nonsynonymous polymorphism in P falciparum eba-175 but not in eba-140 An analysis of the Duffy-binding protein gene, encoding a major erythrocyte-binding antigen in the other common human malaria parasite P vivax, also reveals a significant excess of nonsynonymous polymorphisms when compared with divergence from its ortholog in P knowlesi (a closely related parasite of macaques) The results suggest that EBA-175 in P falciparum and DBP in P vivax are both under diversifying selection from acquired human immune responses
130 citations
TL;DR: The known polymorphic genetic markers are reviewed, current data on the population structure of this parasite is summarized, and future prospects for using knowledge of the genetic diversity to improve control measures are discussed.
129 citations
TL;DR: 28-day in vivo in vivo drug efficacy trials at three sites in the Amazon region and one site on the northern Pacific Coast between 1998 and 2001 found no evidence that chloroquine-resistant P. vivax malaria in Peru had recurrent parasitemia.
Abstract: Reports from several sites in South America suggest the presence of isolated cases of chloroquine-resistant Plasmodium vivax malaria. To investigate the possibility of chloroquine-resistant P. vivax in Peru, we conducted 28-day in vivo drug efficacy trials at three sites in the Amazon region and one site on the northern Pacific Coast between 1998 and 2001. A total of 242 patients between the ages of 2 and 60 years were enrolled (177 from the Amazon region and 65 from the northern coast). All subjects received directly observed therapy with chloroquine, 25 mg/kg, over a three-day period. On enrollment, 49% had a documented fever and 96% had a history of fever; their geometric mean parasite density was 5,129 parasites/microL. A total of 212 (88%) of the 242 subjects completed their 28-day follow-up. Four of the 177 patients from the Amazon region had a recurrence of P. vivax parasitemia on days 21 and 28 after treatment was initiated. Two of these patients had chloroquine-resistant infections, based on polymerase chain reaction-single-stranded conformational polymorphism genotyping and chloroquine-desethylchloroquine blood levels, which were > or = 97 ng/mL at the time of the reappearance of parasitemia. None of the subjects studied on the northern Pacific Coast had recurrent parasitemia.
129 citations
TL;DR: Almost complete failure of chloroquine is document against Plasmodium falciparum or P. vivax near the northeastern coast of Indonesian Papua, the highest risk of therapeutic failure yet observed.
Abstract: Chloroquine remains the first-line therapy for uncomplicated malaria in Indonesia. Among a series of trials of chloroquine for malaria on this archipelago conducted since 1990, we now report the highest risk of therapeutic failure yet observed. A clinical trial of standard chloroquine therapy for uncomplicated malaria at Arso PIR V in northeastern Indonesian Papua was conducted during 1995. We enrolled 104 non-immune subjects infected with Plasmodium falciparum (n = 55), P. vivax (n = 29), or P. falciparum plus P. vivax (n = 20) and administered supervised standard chloroquine therapy (10 + 10 + 5 mg/kg at 24-hour intervals). The 28-day cumulative incidence of therapeutic failure was 95% for P. falciparum, 84% for P. vivax, and 100% for mixed infections. Only one subject each for P. falciparum and P. vivax remained free of parasites at day 28. All recurrent parasitemias occurred with whole blood levels of chloroquine plus desethylchloroquine exceeding 100 ng/ml. These findings document almost complete failure of chloroquine against P. falciparum or P. vivax near the northeastern coast of Indonesian Papua.
TL;DR: This work considers primaquine base to be safe, well-tolerated, and effective prophylaxis against malaria for nonpregnant persons and those with normal glucose-6-phosphate dehydrogenase levels and methemoglobinemia.
Abstract: An expanding risk and range of endemic malaria threatens travelers. Primaquine is an old drug recently demonstrated to offer effective prophylaxis. Clinical trials conducted in Indonesia, Kenya, and Colombia showed that a primaquine base (30 mg per day) had protective efficacy against Plasmodium falciparum and Plasmodium vivax of 85%-93%. Among 339 children (age, >8 years) and adults taking this regimen for 12-52 weeks, there was no greater risk of adverse symptomatic events among primaquine users than among recipients of placebo in double-blind studies. Among 151 subjects evaluated after 20 or 52 weeks of daily primaquine therapy, methemoglobinemia was found to be mild (<13%; typically <6%) and transient (duration, <2 weeks). We consider primaquine base (0.5 mg/kg per day consumed with food) to be safe, well-tolerated, and effective prophylaxis against malaria for nonpregnant persons and those with normal glucose-6-phosphate dehydrogenase levels. Primaquine's major advantage over most drugs for chemoprophylaxis is that it does not have to be taken before entering or beyond 3 days after leaving a malarious area.
TL;DR: Results indicate that clinical immunity in human populations can be driven in malaria-endemic regions that do not have high intensity malaria transmission and argue for using PCR for epidemiologic investigation and malaria control.
Abstract: A cross-sectional study was conducted in the Peruvian Amazon to test the hypothesis that a reservoir of asymptomatic malaria parasitemic patients would form the basis for continuing malaria endemicity in the region. Active surveillance yielded a Plasmodium spp. slide-positive prevalence of 4.2% (43 of 1,023) and a polymerase chain reaction (PCR)-positive prevalence of 17.6% (144 of 819). Plasmodium vivax prevalence was 2.9% and 14.2% while Plasmodium falciparum prevalence was 1.3% and 2.6% by microscopy and PCR, respectively. Approximately two-thirds of slide-positive and one-fourth of PCR-positive people were symptomatic. Anemia was associated with slide positivity (P < 0.001) and PCR positivity for P. falciparum (P = 0.003). Sensitivity of field microscopy and agreement between field and reference laboratory microscopists were low, arguing for using PCR for epidemiologic investigation and malaria control. While these data confirm recent findings from the Brazilian Amazon suggesting that sufficient numbers of asymptomatic malaria parasitemic patients are present to form a persistent reservoir for continuous reinfection within the Peruvian Amazon region, these results also indicate that clinical immunity in human populations can be driven in malaria-endemic regions that do not have high intensity malaria transmission.
TL;DR: A retrospective examination was made of archival data on 98 patient episodes of infection with Plasmodium vivax occurring over a period of 4-11 weeks to document changes in hemoglobin (Hb) concentrations associated with continuing parasitemia.
Abstract: A retrospective examination was made of archival data on 98 patient episodes of infection with Plasmodium vivax occurring over a period of 4-11 weeks to document changes in hemoglobin (Hb) concentrations associated with continuing parasitemia. The mean percentage change in the Hb concentration for each of the 10 seven-day intervals was -13.4, -10.9, -4.8, 0.12, 0.94, 4.0, 0.69, 11.6, 2.4, and 8.3, respectively. An equilibrium appeared to be established between weeks 4 and 6. Decreases in Hb concentrations were greatest following the first week of parasitemia. Total restoration to preinfection levels did not occur during persistent parasitemia.
TL;DR: An update on the Plasmodium v Vivax genome sequencing project is presented, as part of the Trends in Parasitology series of reviews expanding on various aspects of P. vivax research.
TL;DR: The in vitro assay developed in this study should be useful both for assessing the antimalarial sensitivity of P. vivax populations and for screening new antimalarials in the absence of long-term P. falciparum cultures.
Abstract: The aim of this study was to develop a simple, field-practical, and effective in vitro method for determining the sensitivity of fresh erythrocytic Plasmodium vivax isolates to a range of antimalarials. The method used is a modification of the standard World Health Organization (WHO) microtest for determination of P. falciparum drug sensitivity. The WHO method was modified by removing leukocytes and using a growth medium supplemented with AB(+) serum. We successfully carried out 34 in vitro drug assays on 39 P. vivax isolates collected from the Mae Sod malaria clinic, Tak Province, Thailand. The mean percentage of parasites maturing to schizonts (six or more merozoites) in control wells was 66.5% +/- 5.9% (standard deviation). This level of growth in the control wells enabled rapid microscopic determination (5 min per isolate per drug) of the MICs of chloroquine, dihydroartemisinin, WR238605 (tafenoquine), and sulfadoxine. P. vivax was relatively sensitive to chloroquine (MIC = 160 ng/ml, 50% inhibitory concentration [IC(50)] = 49.8 ng/ml) and dihydroartemisinin (MIC = 0.5 ng/ml, IC(50) = 0.47 ng/ml). The poor response of P. vivax to both tafenoquine (MIC = 14,000 ng/ml, IC(50) = 9,739 ng/ml) and sulfadoxine (MIC = 500,000 ng/ml, IC(50) = 249,000 ng/ml) was due to the slow action of these drugs and the innate resistance of P. vivax to sulfadoxine. The in vitro assay developed in our study should be useful both for assessing the antimalarial sensitivity of P. vivax populations and for screening new antimalarials in the absence of long-term P. vivax cultures.
TL;DR: It is likely that Plasmodium vivax diverged approximately 2 million years ago from a group of malaria parasites which are now endemic in monkeys and apes in southern Asia, and might be descended from parasites which infected human populations in the Mediterranean region and in sub-Saharan Africa during the last Ice Age, between 100,000 and 20,000 years ago.
TL;DR: Genetic diversity within and between populations was compared in 100 dbp sequences from isolates obtained from Papua New Guinea, Colombia, and South Korea and showed emergence of distinct allelic families suggestive of divergent selection of alleles between populations.
TL;DR: Analysis of an ≈100-kb contiguous chromosome segment from five isolates shows that P. vivax has a highly diverse genome, and useful information is provided for further understanding the genome diversity of the parasite.
Abstract: The study of genetic variation in malaria parasites has practical significance for developing strategies to control the disease. Vaccines based on highly polymorphic antigens may be confounded by allelic restriction of the host immune response. In response to drug pressure, a highly plastic genome may generate resistant mutants more easily than a monomorphic one. Additionally, the study of the distribution of genomic polymorphisms may provide information leading to the identification of genes associated with traits such as parasite development and drug resistance. Indeed, the age and diversity of the human malaria parasite Plasmodium falciparum has been the subject of recent debate, because an ancient parasite with a complex genome is expected to present greater challenges for drug and vaccine development. The genome diversity of the important human pathogen Plasmodium vivax, however, remains essentially unknown. Here we analyze an ≈100-kb contiguous chromosome segment from five isolates, revealing 191 single-nucleotide polymorphisms (SNPs) and 44 size polymorphisms. The SNPs are not evenly distributed across the segment with blocks of high and low diversity. Whereas the majority (≈63%) of the SNPs are in intergenic regions, introns contain significantly less SNPs than intergenic sequences. Polymorphic tandem repeats are abundant and are more uniformly distributed at a frequency of about one polymorphic tandem repeat per 3 kb. These data show that P. vivax has a highly diverse genome, and provide useful information for further understanding the genome diversity of the parasite.
Journal Article•
TL;DR: In this article, the authors performed a retrospective analysis of smear positive Plasmodium vivax patients with acute renal failure between Jan 1995 to Dec 2000 and found that out of 577 cases of ARF 93 [falciparum 74 (79.61%) were related to complicated malaria.
Abstract: Objectives: To analyze incidence clinical feature and outcome of acute renal failure due to Plasmodium vivax malaria. Material & method: This is retrospective analysis of smear positive Plasmodium vivax patients with acute renal failure between Jan 1995 to Dec 2000. Result: Out of 577 cases of ARF 93 [falciparum 74 (79.61%); vivax 19 (20.4%)] were related to complicated malaria. 3.2% (19/577) patients 16 males and three females with age range 17-72 mean 43.3 ± 13.4 years were due to vivax malaria. Thirteen had only vivax and six had mixed falciparum and vivax infection. The presenting features were fever (100%) jaundice (36.8%) hypotension-eight (42%) encephalopathy-11 (57.9%) sepsis-five (26.3%) and DIC-four (21%). The probable contributory factors for ARF were heavy parasitemia-11 (57.9%) hypotension-six (31.5%) hyperbilirubinemia-seven (36.8%) hemolysis-eight (42%) and DIC-four (21%). Oliguria was present in 47.3% 13 (68.4%) patients required dialysis. Mortality was noted in 15.7% (3/19) patients. Conclusions: P. vivax malaria can cause ARF which occurs more commonly in P. falciparum malaria. Renal ischemia is the dominant pathogenic mechanism that results in acute tubular necrosis. The prognosis of ARF in P. vivax malaria is favorable. (authors)
TL;DR: Assays for rapid diagnosis have the potential to enhance diagnostic capabilities in those instances in which skilled microscopy is not readily available, and each successive prototype showed substantial improvement in performance.
Abstract: The ParaSight F test was developed as a pioneer industry effort in the large-scale, process-controlled production of a device for the rapid diagnosis of malaria. This device performed well in field settings but was limited to the detection of a single malaria species, Plasmodium falciparum. The ParaSight F+V assay advanced upon the ParaSight F test format by incorporating a monoclonal antibody directed against a proprietary Plasmodium vivax-specific antigen, in addition to the antibody directed against P. falciparum histidine-rich protein 2, which was used in the ParaSight F assay. The modified assay was developed to add the capability to detect P. falciparum and P. vivax in a single-test-strip format. The present study evaluated three distinct ParaSight F+V prototypes with samples from symptomatic patients in regions of Thailand and Peru where malaria is endemic. Over a 2-year enrollment period (1998 and 1999), a total of 4,894 patients consented to participation in the study. Compared with the results for duplicate microscopic examinations of Giemsa-stained blood smears as the reference diagnostic standard, each successive prototype showed substantial improvement in performance. The final ParaSight F+V prototype, evaluated in 1999, had an overall sensitivity for detection of asexual P. falciparum parasites of 98%. The sensitivity of the device was 100% for P. falciparum densities of >500 parasites/μl, with a sensitivity of 83% for parasite densities of ≤500/μl. The specificity for the exclusion of P. falciparum was 93%. For P. vivax, the overall sensitivity was 87% for the final 1999 prototype. The sensitivities calculated for different levels of P. vivax parasitemia were 99% for parasite densities of >5,000/μl, 92% for parasite densities of 1,001 to 5,000/μl, 94% for parasite densities of 501 to 1,000/μl, and 55% for parasite densities of 1 to 500/μl. The specificity for the exclusion of P. vivax was 87%. The areas under the receiver operating characteristic curves for the diagnostic performance of the assay for the detection of P. falciparum and P. vivax were 0.8907 and 0.8522, respectively. These findings indicate that assays for rapid diagnosis have the potential to enhance diagnostic capabilities in those instances in which skilled microscopy is not readily available.
TL;DR: Fever, headache and chills were observed simultaneously in 91% of the cases while the most frequent signs were palmar pallor, jaundice, hepatomegaly, and spleen enlargement.
Abstract: A descriptive study was carried out in 104 patients with Plasmodium vivax malaria, from the region of Turbo (Antioquia, Colombia). Clinical features and levels of hemoglobin, glycemia, serum bilirubin, alanine-aminotransferase (ALT), aspartate-aminotransferase (AST), creatinine and complete blood cell profile were established. 65% of the studied individuals were men and their mean age was 23. Of all individuals 59% had lived in the region for > 1 year and 91% were resident in the rural area. 42% were farmers and 35% had a history of malaria. The mean parasitaemia was 5865 parasites/mm3. The evolution of the disease was short (average of 4.0 days). Fever, headache and chills were observed simultaneously in 91% of the cases while the most frequent signs were palmar pallor (46%), jaundice (15%), hepatomegaly (17%), and spleen enlargement (12%). Anemia was found in 39% of the women and in 51% of the men, 8% of individuals had thrombocytopaenia and 41% had hypoglycemia.
TL;DR: Extensive intervention is warranted to reduce the spread of vivax malaria in the Republic of Korea and chemoprophylaxis administered to military personnel may have been responsible for the decreasing number of cases.
Abstract: Vivax malaria reemerged in the Republic of Korea in 1993. Most of the cases occurred among soldiers in the region adjacent to the Demilitarized Zone (DMZ) until 1995. To determine the rate of dispersion of vivax malaria, we evaluated its epidemiologic characteristics. Of 13,903 cases of vivax malaria reported in 2000, 40.1% (5,577) were reported among Republic of Korea military personnel, 26.2% (3,641) among veterans discharged less than two years from the military, and 33.7% (4,685) among civilians. Cases of vivax malaria have rapidly increased annually among counties bordering the DMZ, and have spread to approximately 40 km south of the DMZ. Chemoprophylaxis administered to military personnel may have been responsible for the decreasing number of cases among the Republic of Korea military population. The first mosquito-transmitted cases appeared in early June. Therefore, chemoprophylaxis should be instituted in early April to reduce the number of infected mosquitoes. Extensive intervention is warranted to reduce the spread of vivax malaria in the Republic of Korea.
TL;DR: The presence of these paralogs among the food vacuole plasmepsins in P. falciparum as compared with the other three species causing malaria in man will impact efforts to rationally design antimalarials targeting the food vacated by these enzymes.
TL;DR: In this paper, a mathematical model for the transmission of Plasmodium vivax malaria quantitatively, which is adjusted to the infected region, Guadalcanal, in the Solomon Islands, is proposed.
TL;DR: Direct feeding of mosquitoes with Plasmodium vivax was more effective than use of whole blood or blood that was reconstituted with the patient's own plasma, suggesting a possible role of transmission-blocking antibody.
Abstract: The efficacy of a membrane-feeding apparatus as a means of infecting Anopheles dirus mosquitoes with Plasmodium vivax was compared with direct feeding of mosquitoes on gametocyte carriers. Volunteers participating in the study were symptomatic patients reporting to malaria clinics in western Thailand. Direct mosquito feeds were conducted on 285 P. vivax-infected individuals. Four methods of preparing blood for the membrane-feeding apparatus were evaluated. They included 1) replacement of patient plasma with sera from a P. vivax-naive donor (n = 276), 2) replacement of patient plasma with plasma from a P. vivax-naive donor (n = 83), 3) replacement of patient plasma with that individual’s own plasma (n = 80), and 4) whole blood added directly to the feeder (n = 221). Criteria used to compare the different methods included 1) number of feeds infecting mosquitoes, 2) percent of mosquitoes with oocysts, and 3) mean number of oocysts per positive mosquito. For most parameters, the direct- feeding method was not significantly different from methods that replaced patient plasma with sera/plasma from a P. vivax-naive donor. However, direct feeding was more effective than use of whole blood or blood that was reconstituted with the patient’s own plasma. These data suggest a possible role of transmission-blocking antibody. The implications towards development of a membrane-feeding assay for the evaluation of candidate transmission-blocking malaria vaccines is discussed.
TL;DR: Mice vaccinated with yeast-produced recombinant proteins Pvs25 and Pvs28 adsorbed to aluminum hydroxide developed strong antibody responses against the immunogens and the development of oocysts in mosquitoes was completely inhibited when these antisera were ingested with the P. vivax Salvador (Sal) I strain-infected chimpanzee blood.
TL;DR: A simple, time-effective and yet sensitive and specific technique, based on a multiplex PCR, has now been developed for the simultaneous detection and differentiation of P. falciparum and P. vivax in blood samples.
Abstract: The ability to detect and differentiate between Plasmodium falciparum and P. vivax is of great importance for the routine laboratory diagnosis of malaria, donor-blood screening and epidemiological studies. Most PCR-based methods for the discrimination of these two species require nested protocols or an additional hybridization reaction, leading to high labour costs and long turn-around times. A simple, time-effective and yet sensitive and specific technique, based on a multiplex PCR, has now been developed for the simultaneous detection and differentiation of P. falciparum and P. vivax in blood samples. Compared with the 'gold standard' of microscopy, this method had a sensitivity and specificity of 100%, with a detection limit of just one P. falciparum or three P. vivax parasites/μl blood.
TL;DR: The host response during a P. vivax paroxysm was found to involve T cells, monocytes and neutrophils, and the activity, among others, of the pyrogenic cytokines tumor necrosis factor alpha and interleukin 2 in addition to granulocyte macrophage-colony stimulating factor.
TL;DR: This study demonstrated that for the Brazilian population, an ELISA using a recombinant protein of the MSP119 can be used as the basis for the development of a valuable serological assay for the detection of P. vivax malaria.
Abstract: Background
Serological tests to detect antibodies specific to Plasmodium vivax could be a valuable tool for epidemiological studies, for screening blood donors in areas where the malaria is not endemic and for diagnosis of infected individuals. Because P. vivax cannot be easily obtained in vitro, ELISA assays using total or semi-purified antigens are rarely used. Based on this limitation, we tested whether recombinant proteins representing the 19 kDa C-terminal region of the merozoite surface protein-1 of P. vivax (MSP119) could be useful for serological detection of malaria infection.