Congenital malaria: a case report

Congenital malaria is an uncommon disease even in endemic areas. A 19-day-old female infant with congenital malaria is presented. The mother of the patient was diagnosed to have malaria at the seventh month of gestation and was treated with chloroquine orally for three days. No malarial prophylaxis was given. The infant developed fever, hyperbilirubinemia, anemia and hepatosplenomegaly postnatally. Thin blood smears revealed many Plasmodium vivax parasites. She was treated with oral chloroquine for three days. We emphasize the importance of adequate antenatal medical therapy and prophylaxis during pregnancy.

Malaria diagnosis by dipstick assay in a Honduran population with coendemic Plasmodium falciparum and Plasmodium vivax

A Plasmodium lactate dehydrogenase dipstick designed to separately detect P. falciparum and P. vivax malaria was evaluated in two Honduran populations where both species are endemic. The dipstick was compared to thick film microscopy; the polymerase chain reaction (PCR) was used to analyze discordant results. The dipstick had a sensitivity of 100% and a specificity of 95% compared with microscopy in the diagnosis of Plasmodium infections in a hospital population; the mean parasite density was approximately 590/mm3. In a field sample of mostly asymptomatic volunteers, the sensitivity of the dipstick for Plasmodium infection varied with parasite density. Additionally, the sensitivity and specificity of the dipstick was similar to thick film microscopy in the diagnosis of vivax malaria compared with the PCR. The dipstick was unable to detect P. vivax in the presence of P. falciparum because of cross-reactivity in the pan-specific band. Accurate species identification in mixed infections remains a problem in malaria diagnosis.

Malaria diagnosis by the polymerase chain reaction: a field study in south-eastern Venezuela

A polymerase chain reaction (PCR) method that amplifies genus- and species-specific sequences present within the small subunit of ribosomal ribonucleic acid (ssRNA) genes of the human malaria parasites was used for the diagnosis of malaria in south-eastern Venezuela. One hundred blood samples were submitted to deoxyribonucleic acid extraction, PCR amplification and electrophoretic analysis of the PCR products, and the results were compared to those of routine microscopical diagnosis. The sensitivity of PCR for detection of Plasmodium vivax and P. falciparum malaria was 99% and 100%, respectively. However, 6 patients (6%) harboured parasites undetected by microscopy. The PCR assay detected a high proportion of mixed infections: 29% (17/59) of the infections microscopically diagnosed as P. vivax were shown to be mixed infections of P. vivax and P. falciparum. Forty per cent (7/17) of the individuals with a missed P. falciparum infection had received chloroquine in the previous 30 d. These results suggest that, in places where transmission of both P. vivax and P. falciparum occurs, PCR detection of malaria parasites can be a very useful complement to microscopical diagnosis in order to ascertain the true incidence of each species and for the follow-up of patients after specific treatment.

[Two cases of inexplicable autochthonous malaria in Toulouse, France]

Malaria involving both Plasmodium falciparum and vivax was observed in two patients hospitalized in the same room of the Cardiology Department of the Purpan University Hospital in Toulouse, France. One patient was in coma without fever by the time of diagnosis. None of the patients had traveled to malaria areas within the last 33 years. Epidemiological investigations failed to detect malaria in family members, hospital staff, or other patients. Transmission due to transfusion of infected blood, use of contaminated surgical instrumentation, or bite of an autochthonous anopheles mosquito was reasonable ruled out. Since Toulouse International Airport is located less than three kilometers from the Purpan University Hospital, the most likely explanation was airport-acquired malaria due to the bite of a mosquito imported by an aircraft coming from abroad. The hypothesis that an Anopheles mosquito survived the plane trip and then was blown into the patients' room was supported by temperature and wind conditions prevailing at the time of infection.

[Malaria in Antananarivo: evaluation of a post-epidemic situation]

Antananarivo has a population of close to one million inhabitants and is located in the highlands of Madagascar. The capital was, until some years ago, thought to be a malaria transmission-free zone. However, between 1985 and 1990, several malaria cases occurred in the suburbs of Antananarivo, along the Ikopa river (the Betsimitatatra Plain), suggesting that local transmission was occurring. Numerous malaria cases have since been reported by health workers each year, but there is insufficient epidemiological information about the cause and origin of the transmission, because cases are rarely confirmed by parasitological examination. The National Malaria Control Management in Madagascar has, after four years of intensive DDT spraying campaigns in the highlands, stopped this specific method of control. Epidemiological follow-up studies will be carried out to evaluate the effects on malaria transmission of this cessation of control measures. The transmission of malaria in Antananarivo was studied from 1995 to 1996. Patients from nine health centers in various suburbs of Antananarivo were included in the study, with the presence of fever used as the sole inclusion criterion. Children randomly selected from schools in the same area were included in a second study group. A blood sample was obtained from each participant to determine the parasite index and the prevalence of antibodies against P. falciparum. The splenic index was also determined. A second assessment was performed for the school children six months later, using the same markers of malaria infection. Nine hundred and thirty two patients from the health center group were referred for participation in the study. This represented 10% of all patients and 74% of the patients with fever. The school group included 1,545 children. The splenic index was similarly low (0.5%) in the health center and school groups, as was the overall parasite index (2.6% for the health center group and 0.8% in the school group). The prevalence of antibodies against P. falciparum was also low, but with a seasonal variation: 2.5% in June 1995 and 11.6% in January 1996. Almost all the cases confirmed by parasitological examination were due to the patient having stayed in an area with hyperendemic malaria or having been in contact with an individual who had been to an area with a high level of transmission. Our findings confirm that Antananarivo is now in a post-epidemic situation. Malaria cases are mostly associated with a history of travel in areas with high levels of malaria transmission, particularly the coastal regions of Madagascar. Nevertheless, a low level of transmission may persist and lead to further outbreaks of malaria in the future, due to the presence in the area of Anopheles arabiensis.

[ARDS in plasmodium vivax malaria]

Acute renal failure, disseminated intravascular coagulation, ARDS, hypoglycaemia, coma or epileptic seizures are manifestations of severe Plasmodium falciparum malaria. On the other hand, vivax malaria or benign tertian malaria is usually free from complications. In the present report we describe a case of acute tertian malaria with a severe and complicated course. In this situation bacterial coinfection should always be suspected and treated empirically with broad-spectrum antibiotics, until the results of cultures are available. Mixed plasmodial infection (P. vivax and P. falciparum) must be excluded by repeated and meticulous examination of blood smears. Newer techniques such as PCR processing or ParaSight F Test are mentioned.

Clinical diagnosis of uncomplicated malaria in Sri Lanka

To assess the possibility of developing a protocol for the clinical diagnosis of malaria, a study was done at the regional laboratory of the Anti-Malaria Campaign in Puttalam, Sri Lanka. Of a group of 502 patients, who suspected they were suffering from malaria, 97 had a positive blood film for malaria parasites (71 Plasmodium vivax and 26 P. falciparum). There were no important differences in signs and symptoms between those with positive and those with negative blood films. It is argued that it is unlikely that health workers can improve on the diagnosis of malaria made by the patients themselves, if laboratory facilities are not available. For Sri Lanka the best option is to expand the number of facilities where microscopic examination for malaria parasites can take place.

[Imported fever. A diagnostic challenge]

Fevers without distinguishing symptoms in persons who have visited tropical or subtropical areas is an increasing health problem in most western countries. The condition may be caused by several different microbes, but among cases diagnosed in Norway five infections dominate: falciparum malaria, vivax malaria, typhoid fever, paratyphoid fever and dengue fever. Primary measures should be taken against immediate life-threatening diseases e.g. typhoid fever and falciparum malaria.

Cerebral dysfunction in vivax malaria: a case report

A case of vivax malaria with neurological symptoms is described.

Molecular analysis of Plasmodium vivax relapses using the MSP1 molecule as a genetic marker

Plasmodium vivax has hepatocytic dormant stages, hypnozoites, that cause relapses. This work compared paired isolates from primary attacks and relapses obtained from 10 individuals in Brazil using the merozoite surface protein 1 gene, PvMSP1, as a genetic marker. Four samples from primary attacks contained genetically mixed parasites harboring the 2 major PvMSP1 allelic forms. PCR revealed the presence of these 2 forms in the relapse parasites of 2 patients, demonstrating that the activation of hypnozoites is not clonal. DNA sequences from paired primary/relapse samples demonstrated that the parasites from the primary attack are identical to those in relapse samples in which the same allele forms were detected in both infections. Studies on the naturally acquired humoral immune responses of these patients against a recombinant protein expressing the C-terminus PvMSP1 demonstrated an increase in the titers, affinity maturation, and predominance of the IgG1 subclass during the relapse.

Clinical features cannot predict a diagnosis of malaria or differentiate the infecting species in children living in an area of low transmission

The differentiation of malaria from other causes of fever in the absence of microscopy is notoriously difficult. Clinical predictors of malaria have been studied in an area of low and unstable transmission on the western border of Thailand. In 1527 children aged 2-15 years who were followed prospectively for 7 months, 82% (1254) had at least one febrile episode. Malaria caused 24% (301) of the first febrile episodes (Plasmodium falciparum 128, P. vivax 151, P. malariae 1, mixed infections with P. falciparum and P. vivax 21). Each malaria case was matched with the next child of similar age presenting to the dispensary with another cause of fever. Clinical symptoms or signs associated with a final diagnosis of malaria were: confirmed fever (> or = 38 degrees C) (odds ratio [OR] 1.6, 95% confidence interval [95% CI] 1.4-1.9), headache (OR 1.5, 95% CI 1.3-1.9), muscle and/or joint pain (OR 2.0, 95% CI 1.6-2.8), nausea (OR 1.7, 95% CI 1.4-2.3), clinical anaemia (OR 1.4, 95% CI 1.3-3.3), palpable spleen (OR 1.3, 95% CI 1.1-1.7), palpable liver (OR 1.4, 95% CI 1.1-2.1), absence of cough (OR 1.6, 95% CI 1.4-2.0), and absence of diarrhoea (OR 1.5, 95% CI 1.2-2.4). None of these signs alone or in combination proved a good predictor of malaria. The best diagnostic algorithms (history of fever and headache without cough, and history of fever with an oral temperature > or = 38 degrees C [sensitivity 51% for both, specificity 72 and 71%, respectively]) would result in prescription of antimalarial drugs in 28-29% of the non-malaria febrile episodes, and only 49% of the true malaria cases. Thus half of the potentially life-threatening P. falciparum infections would not be treated. Although multivariate analysis identified vomiting, confirmed fever, splenomegaly and hepatomegaly as independent risk factors for a diagnosis of falciparum malaria, use of these signs to differentiate falciparum from vivax malaria, and thus to determine antimalarial treatment, was insufficiently sensitive or specific. Malaria diagnosis should be confirmed by microscopical examination of a blood slide or the use of specific dipstick tests in areas of low transmission where highly drug-resistant P. falciparum coexists with P. vivax.

Evaluation of the OptiMAL test for rapid diagnosis of Plasmodium vivax and Plasmodium falciparum malaria

The development of rapid and specific diagnostic tests to identify individuals infected with malaria is of paramount importance in efforts to control the severe public health impact of this disease. This study evaluated the ability of a newly developed rapid malaria diagnostic test, OptiMAL (Flow Inc., Portland, Oreg.), to detect Plasmodium vivax and Plasmodium falciparum malaria during an outbreak in Honduras. OptiMAL is a rapid (10-min) malaria detection test which utilizes a dipstick coated with monoclonal antibodies against the intracellular metabolic enzyme parasite lactate dehydrogenase (pLDH). Differentiation of malaria parasites is based on antigenic differences between the pLDH isoforms. Since pLDH is produced only by live Plasmodium parasites, this test has the ability to differentiate live from dead organisms. Results from the OptiMAL test were compared to those obtained by reading 100 fields of traditional Giemsa-stained thick-smear blood films. Whole-blood samples were obtained from 202 patients suspected of having malaria. A total of 96 samples (48%) were positive by blood films, while 91 (45%) were positive by the OptiMAL test. The blood films indicated that 82% (79 of 96) of the patients were positive for P. vivax and 18% (17 of 96) were infected with P. falciparum. The OptiMAL test showed that 81% (74 of 91) were positive for P. vivax and 19% (17 of 91) were positive for P. falciparum. These results demonstrated that the OptiMAL test had sensitivities of 94 and 88% and specificities of 100 and 99%, respectively, when compared to traditional blood films for the detection of P. vivax and P. falciparum malaria. Blood samples not identified by OptiMAL as malaria positive normally contained parasites at concentrations of less than 100/microl of blood. Samples found to contain P. falciparum were further tested by two other commercially available rapid malaria diagnostic tests, ParaSight-F (Becton Dickinson, Cockeysville, Md.) and ICT Malaria P.f. (ICT Diagnostics, Sydney, Australia), both of which detect only P. falciparum. Only 11 of the 17 (65%) P. falciparum-positive blood samples were identified by the ICT and ParaSight-F tests. Thus, OptiMAL correctly identified P. falciparum malaria parasites in patient blood samples more often than did the other two commercially available diagnostic tests and showed an excellent correlation with traditional blood films in the identification of both P. vivax malaria and P. falciparum malaria. We conclude that the OptiMAL test is an effective tool for the rapid diagnosis of malaria.

Increased sensitivity of malaria detection by nested polymerase chain reaction using simple sampling and DNA extraction

Malaria remains a disease of underdeveloped and remote regions of the world. The application of polymerase chain reaction (PCR) technology to malaria epidemiology has the potential for increasing our knowledge and understanding of this disease. In order to study malaria in all geographical locations it is important that specimen collection and DNA extraction for PCR be kept simple. Here we report a method for extracting DNA from dried blood spots on filter paper which is capable of detecting one Plasmodium falciparum and two Plasmodium vivax parasites/microliter of whole blood by nested PCR without compromising the simplicity of specimen collection or DNA extraction.

A small epidemiological survey for vivax malaria in Kimpo-gun, Kyonggi-do, Korea undertaken after detecting two consecutive cases

On July and August 1997, two 15-year-old mates of a football team of Tongjin Middle School in northern Kyonggi-do, Korea were consecutively diagnosed as vivax malaria by peripheral blood smear. They had no histories of travelling abroad or drug abuse. They witnessed that other mates in the team were ill of fever in the same period. A small survey was therefore undertaken to determine whether vivax malaria was outbroken locally. A total of 57 students of the team living together in a dormitory was examined for history of fever, presence of splenomegaly, blood smear and anti-P. vivax antibody test by immunofluorescent antibody test (IFAT). Except for the above two patients, only one case revealed a marginal titer of IFAT. No other positive findings of vivax malaria were found. In the results of this local survey, no more cases of vivax malaria were revealed except the two sporadic cases.

Plasmodium vivax infection in a child residing in Mobile, Alabama

A previously healthy 4-year old male, born in India and residing in Mobile, Alabama since October 1996 came to the emergency department in April 1997 because of general malaise, fever and vomits of 5 days duration. A peripheral smear of the complete blood count revealed the presence of malarial parasites within the erythrocytes. Plasmodium vivax was later identified in serial thin peripheral smears. He defervesced after initial treatment with oral quinine and pyrimethamine-sulfadoxine, followed by primaquine for 14 days.

The laboratory diagnosis of malaria. The Malaria Working Party of The General Haematology Task Force of the British Committee for Standards in Haematology

Audits of malaria diagnosis in the UK have revealed shortcomings. The use of recommended procedures should improve the standard of malaria diagnosis. Both thick and thin films should be examined. Thick films should be stained unfixed with a Giemsa or modified Field's stain. Thin films should be fixed and stained with a Giemsa or a Leishman stain. All films should be examined for an adequate period of time by two observers. In the case of P. falciparum infection parasites should be quantified. Microscopy may be supplemented by an immunological or fluorescence-based method. Slides from all cases in which a diagnosis of malaria is made should be sent to a reference centre for verification. Laboratories should participate in a relevant NEQAS scheme and should take steps to ensure that all those carrying out malaria diagnosis maintain their skills.

Postpartal endomyometritis in a case of unknown tertian malaria

A 28-year-old woman developed puerperal endomyometritis and tertian malaria simultaneously. She delivered her child by vacuum extraction during week 41 of pregnancy in September 1994. The peripartal period was uneventful. Nine days post partum the patient was readmitted to hospital with fever and pain in the area of the episiotomy. On day 13 post partum a hysterectomy was performed because of suspected abscess-forming endomyometritis. Two days after the hysterectomy the patient developed septic temperatures, which persisted for 10 days. Tertian malaria due to Plasmodium vivax was found to be the cause of fever. The patient had been in Indonesia without anti-malarial prophylaxis in 1991. Two years later she travelled to Ghana, having taken mefloquine as prophylaxis. Malaria was obviously caused by reactivated hypnozoites in the liver, although the patient had never had an episode of fever associated with malaria before. This case proves that tertian malaria may "recur" even without previous manifestation, years after a stay in a region endemic for malaria.

Early diagnosis and treatment of malaria in a refugee population in Sri Lanka

To provide early diagnosis and prompt treatment for malaria, two interventions were compared in refugee camps in Kalpitiya, Sri Lanka. Community health volunteers (HV's) were trained in diagnosis and management of malaria on clinical grounds, while a field laboratory was established in another group of camps providing treatment after laboratory confirmation of a malarial infection. Patients with fever sought treatment from HV's on average after 2.74 days and from the field laboratory after 3.20 days. Although acceptance of both interventions was high, the effective catchment areas, especially of the HV's were small. Large numbers of health volunteers would be needed to cover all families, making it difficult to sustain supervision and necessary logistic support. For every malaria patient treated by HV's, three others would receive anti-malarial drugs unnecessarily. The maintenance of a field laboratory with a microscopist of the Anti-Malaria Campaign is not an economically viable option. Training of HV's in microscopy with a mechanism for cost recovery should be given serious consideration. HV's and diagnosis and treatment centers should be able to handle a wide spectrum of common diseases. A better option for Sri Lanka in the short term might be to improve existing general health facilities that are accessible to the refugee population.

[Malaria attack: a very late relapse due to Plasmodium vivax]

Plasmodium vivax malaria late-forms rarely exceed two years--the authors reported a late-form more than twenty years after a stay in endemic area. This late-form occurred in an immunocompromised patient with two terminal-stage neoplasia receiving radio, chimio corticotherapy associated with anemia and thrombopenia. Repeated-tests allowed the diagnostic.

Clinical trials of a new immunochromatographic test for diagnosis of Plasmodium falciparum malaria in Goa

Plasmodium falciparum histidine rich protein-2 (PfHRP-2) based immunochromatographic test kit (ICT Malaria Pf) for the rapid diagnosis of P. falciparum malaria was evaluated at the clinic of Malaria Research Centre (Field Station), Goa. Of the 98 febrile patients screened, 22 were ICT positive for P. falciparum. Simultaneous microscopic examination of the blood smears of these ICT positive patients showed that 20 were positive for P. falciparum alone, whereas one had mix infection of both P. vivax and P. falciparum suggesting 100% sensitivity. Only one slide negative patient who had taken 600 mg chloroquine the previous day was positive in the ICT. Out of the remaining 76 blood smears, 41 showed P. vivax infection and none cross-reacted with P. falciparum HRP-2 antigen and were ICT negative except one mix infection case in which P. vivax and P. falciparum infections occurred concomitantly suggesting species specificity of 98.7%. The positive predictive value, negative predictive value and efficacy of the ICT were 95.4, 100 and 98.9% respectively. The band intensity of the ICT positive cases significantly correlated with P. falciparum parasitaemia (p < 0.01). The usefulness and the disadvantages of this diagnostic kit have been discussed in context of prevailing malaria situation in the country.

Posttransplant malaria

The frequency and clinical characteristics of plasmodium infection were reported in 420 renal transplant recipients who were followed in the Transplantation Unit and Out-Patient Clinic of the Medical School of Istanbul. Plasmodium infection was diagnosed in eleven (9 male, 2 female) of the 420 patients (2.6%). Ten of the patients were transplanted in India, and one in our institution. The mean duration between the transplantation and the diagnosis of malaria was 21.7 + 44.4 days in patients who were transplanted in India. All of the patients were taking triple immunosuppressive drugs (CsA, AZA, PRED). Plasmodium falciparum was diagnosed in 6 patients, P vivax in 1 patient and P malariae in 1 patient. Also mixed infection with P falciparum and P malariae was diagnosed in 3 patients. After definite diagnosis, the patients were hospitalized. Chloroquine phosphate plus primaquine phosphate was administered for P vivax infection, whereas chloroquine phosphate alone was given for P falciparum and P malariae infection as a first line antimalarial therapy. As a result of therapy, infection improved clinically and the plasmodia disappeared rapidly from the thick blood film in 10 of the patients. Severe hemolysis and acute renal failure developed in one patient, who improved after hemodialysis therapy and exchange transfusions. It was concluded that malaria is quite a frequent infection of transplant recipients who get their allografts from donors living in high-risk areas, and all transplant recipients having this kind of transplantations should be suspected and examined for malaria. This may help to diagnose and treat the complication in the early period, thus resulting in an improved prognosis for this potentially life-threatening complication of the posttransplant period.

Plasmodium vivax malaria after autologous bone marrow transplantation: an unusual complication

We report the case of unusually early infection by Plasmodium vivax after autologous bone marrow transplantation in a 20-year-old female from Bangladesh affected by acute myelogenous leukemia in first complete remission (CR) who underwent autologous bone marrow transplantation in our center. During the aplastic phase she became febrile; broad spectrum antibiotics and antifungal therapy were without effect. Blood smears were examined and Plasmodium vivax was detected despite a very low number of red cells infected. Cloroquine therapy for 3 days was given followed by primaquine for 2 weeks in order to avoid possible cloroquine resistance. Fever disappeared within 48 h from initial treatment and the patient was discharged having completely recovered at day +30. Primary malaria infection in non-endemic areas is a very rare event. In this particular case, after excluding primary infection or blood transfusion-mediated infection, malaria was attributed to a recrudescence of a primary unidentified infection.

[The characteristics of the clinical course of malaria in Ethiopia]

The high incidence of malaria in Ethiopia is due to a number of natural and social factors. The 1988-1989 surveys of 525 patients among this country's indigenous population showed that its great proportion suffered from severe falciparum malaria, including that caused by the chloroquine-resistant strains Plasmodium falciparum. The severity of falciparum malaria seems to be determined by the low immunity of inhabitants in the hyperendemic areas and by late effective therapy. The lack of antimalarial drugs alternative to chloroquine will facilitate fatal malignant malaria.

[Atypical Plasmodium vivax malaria in an adopted child]

An atypical, because of relatively high parasitemia, multiply-infected erythrocytes and long incubation, Plasmodium vivax malaria case in an foreign born adopted child is presented. Features typical of Plasmodium vivax were enlarged infected erythrocytes, characteristic schizont and Schuffner's dots. Our observation emphasizes the importance of blood smear evaluation in traveller and foreign born adopted children.

Malaria--eight years of experience in a Tokyo metropolitan hospital

Malaria patients who were admitted to the Department of Infectious Diseases of the Tokyo Metropolitan Bokutoh General Hospital during the past 8 years are reviewed. Cases included 17 patients infected with Plasmodium falciparum (14 Japanese), 13 patients infected with P. vivax (9 Japanese), 3 patients infected with P. ovale (2 Japanese) and 1 Chinese patient with a mixed infection of P. falciparum and P. vivax. About 70% of Japanese patients infected with P. falciparum contracted the disease in Africa, about 90% P. vivax-infected Japanese patients contracted the disease in Asia and all P. ovale-infected patients contracted the disease in Africa. Only 13% of all (17% of Japanese) patients infected with P. falciparum who initially contracted doctors of other Japanese hospitals were correctly diagnosed, but 78% of all (67% of Japanese) patients infected with P. vivax who initially contacted doctors of other Japanese hospitals were correctly diagnosed. At present, malaria is not a rare disease in Tokyo among travelers to or from Africa or Asia.

Field evaluation of the QBC technique for rapid diagnosis of vivax malaria

The QBC (quantitative buffy coat) technique was compared with that of the Giemsa-stained thick blood film (GTF) under field conditions in Junlian and Mingshan counties, Sichuan, China, for rapid diagnosis of vivax malaria. Blood samples were collected from 364 volunteer villagers, and each sample was examined with both the QBC and GTF techniques. For each GTF sample (10 microliters of blood), as many as 300 oil-immersion fields were examined; each QBC tube was inspected for up to 5 minutes. The GTF technique resulted in 86 positive blood samples and 278 negative; the QBC technique indicated 89 positive and 275 negative samples. Relative to the results obtained with GTF, the QBC technique had a sensitivity and specificity of 87.2% and 95.0%, respectively; concordance between the tests was 93.1%. The median time-to-positive diagnosis with the QBC technique (1.12 min) was 11% of that with GTF. The distribution of different developmental stages of Plasmodium vivax parasites was also examined in the centrifuged QBC tubes: all stages except schizonts could be found in the lower part of the platelet zone (the interphase between the monocyte and platelet layers), especially ring forms.

Immunological characterization and expression in Escherichia coli and baculovirus systems of a Trypanosoma vivax antigen detected in the blood of infected animals

A monoclonal antibody (MAb)Tv27 employed in an antigen-detection enzyme immunosorbent assay (Ag-ELISA) for diagnosis of Trypanosoma vivax infection was shown to react with a T. vivax-specific protein of an approximate molecular weight of 10 kDa. This protein is diffusely distributed throughout the cytosol and nucleus of metacyclic forms, bloodstream forms, and procyclic-like elongated trypomastigotes, but is not detectable in epimastigotes of T. vivax. The T. vivax-specific antigen prepared from parasite lysates appeared to be of lower molecular mass than the form expressed in either Escherichia coli or in baculovirus-infected silkworm insect cells. In the recombinant baculovirus-infected cells, the protein was expressed mostly as an 18-kDa peptide with less abundant forms of 13 and 12 kDa, while the protein expressed in E. coli was approximately 14 kDa. Both the low- and higher-molecular-weight proteins are recognized by the MAb Tv27 in Western blots and in Ag-ELISA. Although the crude preparations of the protein produced by the insect cells are labile when kept for more than 2 hr at 24 degrees C, they retained reactivity at temperatures below 4 degrees C for several weeks. The proteins expressed in both the insect cells and E. coli captured anti-T. vivax antibodies in sera prepared from trypanosome-infected animals. Since the recombinant protein expressed in the baculovirus-infected cells is available in large homogeneous quantities, it would serve as a positive control in Ag-ELISA and is also usable for antibody detection assays.

False positive modified Widal test in acute malaria

The present study reports results of modified Widal test carried out on 96 cases of acute malaria and 25 healthy controls. Out of the 96 patients studied, 30 had complicated P.falciparum (CPF), 36 had uncomplicated P.falciparum (UPF) and 30 had P.vivax (pv) malaria. Modified widal test was done to know the Widal titers due to Igm type of anti-salmonella antibodies, which is considered very specific for diagnosis of recent enteric fever. This test was positive in 14.58% and 10.41% of malaria patients for salmonella 'o' and 'H' titers respectively. On four weeks follow up most of the positive test become negative. Non-specific polyclonal B lymphocyte stimulation due to malaria was postulated to be responsible for this phenomenon.

Species-specific 18S rRNA gene amplification for the detection of P. falciparum and P. vivax malaria parasites

Based on the sequence diversity of the Plasmodium 18S ribosomal RNA (rRNA), we designed oligonucleotide primers for polymerase chain reaction (PCR) to yield different size fragments for P. falciparum and P. vivax. The primers for the PCR procedure were chosen such that the 5' primer was Plasmodium-conserved while the 3' primers were species-specific. Using primer cocktails and cloned plasmid DNAs containing the 18S rRNA genes or parasite genomic DNA as targets, we show that the PCR procedure yields 1.4-kb and 0.5-kb DNA fragments for P. falciparum and P. vivax, respectively. Limited field testing of this procedure demonstrated the utility of a ribosomal gene based species-specific malaria diagnosis.

Plasmodium vivax: detection of blood parasites using fluorochrome labelled monoclonal antibodies

A monoclonal antibody (MoAb) 2C6111 specific for Plasmodium vivax erythrocytic stages was shown to detect parasitized erythrocytes in blood samples collected in the field. This MoAb binds to the mature trophozoite, schizont and gametes of P. vivax and upon examination of 43 wild isolates no evidence of polymorphism was found. To search for P. vivax parasites in human blood a MoAb immunofluorescent test (MoAb-IFT) was developed. The assay is based on the ability of fluorescein isothiocyanate labelled MoAb 2C6111 to combine with parasitized erythrocytes on thin blood smears. A preliminary field trial was carried out in Venezuela to determine the usefulness of MoAb-IFT for the specific diagnosis of P. vivax malaria. Blood samples collected from malarious and non-malarious individuals were examined both by standard microscopy of Giemsa stained thick blood smears (G-TS) and MoAb-IFT. The latter was specific and gave a 100% correlation with G-TS. Sensitivity was close to that usually achieved with Giemsa stained blood films.

A non-radioactive DNA diagnostic procedure for the detection of malarial infection: general application to genome with repetitive sequences

A novel non-radioactive DNA diagnostic method has been developed to detect Plasmodium falciparum infection in whole blood. In this method a drop of blood from a finger prick is added to a lysing solution containing a biotinylated oligonucleotide whose sequence design is based on the repeated sequence of the parasite genome. The mixture is heated in a boiling water bath and then added to a microtitre plate where the 'target-bioprobe hybrids' are captured by the immobilized oligonucleotides. The plate is then washed to remove the coloured material and the biotinylated oligonucleotide retained on the plate is assayed by streptavidin-alkaline phosphatase conjugate. This method has also been tested in field trials by double-blind studies to detect P.falciparum infection in blood samples. Results indicate that this method is superior to the classical blood smear examination for its speed and its ease in large epidemiological surveys and is especially useful in identifying clinical malaria in endemic areas where the semi-immune population predominates. The method described can be of general application for the detection of any foreign pathogen in blood, other body fluids and tissue samples, provided the DNA probe employed constitutes a part of the repeated sequence of the genome and is unique.

Comparison between microscopic examination, ELISA and quantitative buffy coat analysis in the diagnosis of falciparum malaria in an endemic population

Monoclonal antibody-based ELISA and QBC (quantitative buffy coat analysis) were tested in two endemic areas with low and high incidence of malaria in Kanchanaburi Province, West Thailand with annual parasite incidence in 1992 of 119 and 5 per 1,000 population, respectively. The numbers of individuals positive by thick blood film examination (TBF) for P. falciparum with or without P. vivax, and P. vivax only were 82 and 69, respectively. The detection limit of ELISA was 10 parasites/10(6) red blood cells (RBC) (0.001% parasitemia). Of 1,095 individuals involved in the study at the beginning of the study, ELISA showed sensitivity, specificity, positive predictive value and negative predictive value of 78.1%, 94.9%, 72% and 98.1%, respectively. Nine of 18 (50%) TBF-positive but ELISA-positive individuals had parasitemia of less than 10 parasites/10(6) RBC. High and low incidence areas did not affect the validity of our result. Regression analysis showed good correlation between log parasitemia and ELISA percent OD increase (Y = 0 + 64.9*logX, r = 0.65), and agreement between TBF and ELISA results was 95.9%. In a fortnightly follow-up, in 82 TBF-positive individuals, both ELISA and TBF positive rates correlatively declined with agreement of 96.3%. With samples taken on the first day of the study, the TBF and QBC results were also correlated with agreement of 95.8% for P. falciparum, 95.6% for P. vivax. During 8 week follow-up involving altogether 191 samples, agreement between TBF and QBC results were 87.4% for P. falciparum. QBC detected more cases with P. falciparum infections but detected smaller number of cases with P. vivax infections.

[Malaria imported by immigrants in Catalonia]

BACKGROUND

The aim of the present study was to analyze the epidemiologic aspects and particular features of malaria in immigrants in Catalonia, Spain.

METHODS

All the immigrants who visited the Unit of Tropical and Imported Diseases "Drassanes" in Barcelona from endemic zones of malaria from 1990 to 1993 were studied. The diagnosis of malaria was based on the thick blood film, peripheral blood smear exam and, since 1991, the QBC (Quantitative Buffy Coat).

RESULTS

One hundred three cases of malaria were diagnosed in 100 individuals from a total of 2,453 visited immigrants. Forty-four percent of the patients presented febrile syndrome, 11% cutaneous syndrome accompanied by other manifestations justifying the same, 9% presented other clinical manifestations and 36% were asymptomatic. Ninety-six percent of the subjects with parasites by Plasmodium were from sub-Saharan Africa and in 2 cases, both were produced by Plasmodium falciparum, with the length of time having been in Spain at the time of diagnosis being more than one year. P. falciparum represented 70% of the total cases, followed by P. malariae (15%), P. vivax (8%), Plasmodium spp. (6%) and P. ovale (1%).

CONCLUSIONS

Malaria by P. falciparum in semi-immune immigrants is not usually severe and follows an asymptomatic course in more than one third of the cases. The usual analysis for Plasmodium is recommended in immigrants from sub-Saharan Africa due to the high frequency of presentation and the absence of symptoms. Such analysis is not advised in groups from other areas except when suggestive symptoms are present.