COVID-19 and Plasmodium ovale Malaria: A Rare Case of Co-Infection.

The COVID-19 pandemic continues to be a major health problem worldwide. Timely diagnosis of co-infections mimicking COVID-19, such as malaria, might be challenging particularly in non-endemic areas. We report the first case of COVID-19 and Plasmodium ovale malaria co-infection from our region aiming to highligt the importance of travel history and prophylaxis in malaria management in the context of pandemic. The galloping sound can sometimes be a harbinger of zebra besides the horse.

Epidemiological profile of Plasmodium ovale spp. imported from Africa to Anhui Province, China, 2012-2019.

BACKGROUND: Although autochthonous malaria cases are no longer reported in Anhui Province, China, imported malaria has become a major health concern. The proportion of reported malaria cases caused by Plasmodium ovale spp. increased to levels higher than expected during 2012 to 2019, and showed two peaks, 19.69% in 2015 and 19.35% in 2018. METHODS: A case-based retrospective study was performed using data collected from the China Information System for Disease Control and Prevention (CISDCP) and Information System for Parasitic Disease Control and Prevention (ISPDCP) from 2012 to 2019 to assess the trends and differences between Plasmodium ovale curtisi (P. o. curtisi) and Plasmodium ovale wallikeri (P. o. wallikeri). Epidemiological characteristics were analyzed using descriptive statistics. RESULTS: Plasmodium o. curtisi and P. o. wallikeri were found to simultaneously circulate in 14 African countries. Among 128 patients infected with P. ovale spp., the proportion of co-infection cases was 10.16%. Six cases of co-infection with P. ovale spp. and P. falciparum were noted, each presenting with two clinical attacks (the first attack was due to P. falciparum and the second was due to P. ovale spp.) at different intervals. Accurate identification of the infecting species was achieved among only 20.00% of cases of P. ovale spp. infection. At the reporting units, 32.17% and 6.96% of cases of P. ovale spp. infection were misdiagnosed as P. vivax and P. falciparum infections, respectively. CONCLUSION: The present results indicate that the potential of P. ovale spp. to co-infect with other Plasmodium species has been previously underestimated, as is the incidence of P. ovale spp. in countries where malaria is endemic. P. o. curtisi may have a long latency period of > 3 years and potentially cause residual foci, thus posing challenges to the elimination of malaria in P. ovale spp.-endemic areas. Considering the low rate of species identification, more sensitive point-of-care detection methods need to be developed for P. ovale spp. and introduced in non-endemic areas.

Hypnozoites in Plasmodium: Do Parasites Parallel Plants?

The phenomenon of relapsing malaria has been recognised for centuries. It is caused in humans by the parasite species Plasmodium vivax and Plasmodium ovale, which can arrest growth at an early, asymptomatic stage as hypnozoites inside liver cells. These dormant parasites can remain quiescent for months or years, then reactivate causing symptomatic malaria. The dynamics of hypnozoite dormancy and reactivation are well documented but the molecular basis remains a complete mystery. Here, I observe that the process has striking parallels with plant vernalisation, whereby plants remain dormant through the winter before flowering in spring. Vernalisation is thoroughly studied in several plant species and its mechanisms are known in exquisite detail. Vernalisation may thus provide a useful framework for interrogating hypnozoite biology.

The WorldWide Antimalarial Resistance Network Clinical Trials Publication Library: A Live, Open-Access Database of Plasmodium Treatment Efficacy Trials.

Parasite resistance to antimalarial drugs poses a serious threat to malaria control. The WorldWide Antimalarial Resistance Network (WWARN) aims to provide a collaborative platform to support the global malaria research effort. Here, we describe the "WWARN clinical trials publication library," an open-access, up-to-date resource to streamline the synthesis of antimalarial safety and efficacy data. A series of iteratively refined database searches were conducted to identify prospective clinical trials assessing antimalarial drug efficacy with at least 28 days of follow-up. Of approximately 45,000 articles screened, 1,221 trials published between 1946 and 2018 were identified, representing 2,339 treatment arms and 323,819 patients. In trials from endemic locations, 75.7% (787/1,040) recruited patients with Plasmodium falciparum, 17.0% (177/1,040) Plasmodium vivax, 6.9% (72/1,040) both, and 0.4% (4/1,040) other Plasmodium species; 57.2% (585/1,022) of trials included under-fives and 5.3% (55/1,036) included pregnant women. In Africa, there has been a marked increase in both P. falciparum and P. vivax studies over the last two decades. The WHO-recommended artemisinin-based combination therapies alone or with a gametocidal drug were assessed in 39.5% (705/1,783) of P. falciparum treatment arms and 10.5% (45/429) of P. vivax arms, increasing to 78.0% (266/341) and 22.9% (27/118), respectively, in the last five years. The library is a comprehensive, open-access tool that can be used by the malaria community to explore the collective knowledge on antimalarial efficacy (available at https://www.wwarn.org/tools-resources/literature-reviews/wwarn-clinical-trials-publication-library). It is the first of its kind in the field of global infectious diseases, and lessons learnt in its creation can be adapted to other infectious diseases.

Mosquito and human hepatocyte infections with Plasmodium ovale curtisi and Plasmodium ovale wallikeri.

BACKGROUND: Human ovale malaria is caused by the two closely related species, Plasmodium ovale curtisi and P. ovale wallikeri. Both species are known to relapse from quiescent hepatic forms months or years after the primary infection occurred. Although some studies have succeeded in establishing mosquito transmission for ovale malaria, none have specifically described transmission and human hepatocyte infection of both sibling species. METHODS: Here we describe a simplified protocol for successful transmission of both P. ovale curtisi and P. ovale wallikeri to Anopheles coluzzii mosquitoes and streamlined monitoring of infection using sensitive parasite DNA detection, by loop-activated amplification, in blood-fed mosquitoes. RESULTS: In one experimental infection with P. ovale curtisi and one with P. ovale wallikeri, viable sporozoites were isolated from mosquito salivary glands and used to successfully infect cultured human hepatocytes. CONCLUSIONS: This protocol provides a method for the utilisation of pretreatment clinical blood samples from ovale malaria patients, collected in EDTA, for mosquito infection studies and generation of the hepatic life cycle stages of P. ovale curtisi and P. ovale wallikeri. We also demonstrate the utility of loop-activated amplification as a rapid and sensitive alternative to dissection for estimating the prevalence of infection in Anopheles mosquitoes fed with Plasmodium-infected blood.

Persistent transmission of Plasmodium malariae and Plasmodium ovale species in an area of declining Plasmodium falciparum transmission in eastern Tanzania.

A reduction in the global burden of malaria over the past two decades has encouraged efforts for regional malaria elimination. Despite the need to target all Plasmodium species, current focus is mainly directed towards Plasmodium falciparum, and to a lesser extent P. vivax. There is a substantial lack of data on both global and local transmission patterns of the neglected malaria parasites P. malariae and P. ovale spp. We used a species-specific real-time PCR assay targeting the Plasmodium 18s rRNA gene to evaluate temporal trends in the prevalence of all human malaria parasites over a 22-year period in a rural village in Tanzania.We tested 2897 blood samples collected in five cross-sectional surveys conducted between 1994 and 2016. Infections with P. falciparum, P. malariae, and P. ovale spp. were detected throughout the study period, while P. vivax was not detected. Between 1994 and 2010, we found a more than 90% reduction in the odds of infection with all detected species. The odds of P. falciparum infection was further reduced in 2016, while the odds of P. malariae and P. ovale spp. infection increased 2- and 6-fold, respectively, compared to 2010. In 2016, non-falciparum species occurred more often as mono-infections. The results demonstrate the persistent transmission of P. ovale spp., and to a lesser extent P. malariae despite a continued decline in P. falciparum transmission. This illustrates that the transmission patterns of the non-falciparum species do not necessarily follow those of P. falciparum, stressing the need for attention towards non-falciparum malaria in Africa. Malaria elimination will require a better understanding of the epidemiology of P. malariae and P. ovale spp. and improved tools for monitoring the transmission of all Plasmodium species, with a particular focus towards identifying asymptomatic carriers of infection and designing appropriate interventions to enhance malaria control.

Prospective comparative multi-centre study on imported Plasmodium ovale wallikeri and Plasmodium ovale curtisi infections.

BACKGROUND: Few previous retrospective studies suggest that Plasmodium ovale wallikeri seems to have a longer latency period and produces deeper thrombocytopaenia than Plasmodium ovale curtisi. Prospective studies were warranted to better assess interspecies differences. METHODS: Patients with imported P. ovale spp. infection diagnosed by thick or thin film, rapid diagnostic test (RDT) or polymerase chain reaction (PCR) were recruited between March 2014 and May 2017. All were confirmed by DNA isolation and classified as P. o. curtisi or P. o. wallikeri using partial sequencing of the ssrRNA gene. Epidemiological, analytical and clinical differences were analysed by statistical methods. RESULTS: A total of 79 samples (35 P. o. curtisi and 44 P. o. wallikeri) were correctly genotyped. Males predominate in wallikeri group (72.7%), whereas were 48.6% in curtisi group. Conversely, 74.3% of curtisi group were from patients of African ethnicity, whilst 52.3% of Caucasians were infected by P. o. wallikeri. After performing a multivariate analysis, more thrombocytopaenic patients (p = 0.022), a lower number of platelets (p = 0.015), a higher INR value (p = 0.041), and shorter latency in Caucasians (p = 0.034) were significantly seen in P. o. wallikeri. RDT sensitivity was 26.1% in P. o. curtisi and 42.4% in P. o. wallikeri. Nearly 20% of both species were diagnosed only by PCR. Total bilirubin over 3 mg/dL was found in three wallikeri cases. Two patients with curtisi infection had haemoglobin under 7 g/dL, one of them also with icterus. A wallikeri patient suffered from haemophagocytosis. Chemoprophylaxis failed in 14.8% and 35% of curtisi and wallikeri patients, respectively. All treated patients with various anti-malarials which included artesunate recovered. Diabetes mellitus was described in 5 patients (6.32%), 4 patients of wallikeri group and 1 curtisi. CONCLUSIONS: Imported P. o. wallikeri infection may be more frequent in males and Caucasians. Malaria caused by P. o. wallikeri produces more thrombocytopaenia, a higher INR and shorter latency in Caucasians and suggests a more pathogenic species. Severe cases can be seen in both species. Chemoprophylaxis seems less effective in P. ovale spp. infection than in P. falciparum, but any anti-malarial drug is effective as initial treatment. Diabetes mellitus could be a risk factor for P. ovale spp. infection.

School-based malaria prevalence: informative systematic surveillance measure to assess epidemiological impact of malaria control interventions in the Democratic Republic of the Congo.

BACKGROUND: In southern Democratic Republic of the Congo, malaria transmission is stable with seasonal fluctuations. Different measurements can be used to monitor disease burden and estimate the performance of control programmes. Repeated school-based malaria prevalence surveys (SMPS) were conducted from 2007 to 2014 to generate up-to-date surveillance data and evaluate the impact of an integrated vector control programme. METHODS: Biannual SMPS used a stratified, randomized and proportional sampling method. Schools were randomly selected from the entire pool of facilities within each Health Area (HA). Subsequently, school-children from 6 to 12 years of age were randomly selected in a proportional manner. Initial point-of-care malaria diagnosis was made using a rapid detection test. A matching stained blood film was later examined by expert microscopy and used in the final analysis. Data was stratified and analysed based on age, survey time and location. RESULTS: The baseline SMPS (pre-control in 2007) prevalence was approximately 77%. From 2009 to 2014, 11,628 school-children were randomly screened. The mean age was 8.7 years with a near equal sex ratio. After exclusion, analysis of 10,493 students showed an overall malaria prevalence ratio of 1.92 in rural compared to urbanized areas. The distribution of Plasmodium falciparum malaria was significantly different between rural and urban HAs and between end of wet season and end of dry season surveys. The combined prevalence of single P. falciparum, Plasmodium malariae and Plasmodium ovale infections were 29.9, 1.8 and 0.3% of those examined, respectively. Only 1.8% were mixed Plasmodium species infections. From all microscopically detected infections (3545 of 10,493 samples examined), P. falciparum represented 88.5%, followed by P. malariae (5.4%) and P. ovale (0.8%). Cases with multiple species represented 5.3% of patent infections. Malaria prevalence was independent of age and gender. Control programme performance contributed to a significant decrease in mean P. falciparum infection density in urban compared to rural locations. Some rural areas remained highly refractory to control measures (insecticide-treated bed nets, periodic indoor residual spraying). CONCLUSION: The SMPS is a useful longitudinal measurement for estimating population malaria prevalence and demonstrating disease burden and impact of control interventions. SMPS can identify refractory areas of transmission and thus prioritize control strategies accordingly.

Persistent Parasitism: The Adaptive Biology of Malariae and Ovale Malaria.

Plasmodium malariae causes malaria in humans throughout the tropics and subtropics. Plasmodium ovale curtisi and Plasmodium ovale wallikeri are sympatric sibling species common in sub-Saharan Africa and also found in Oceania and Asia. Although rarely identified as the cause of malaria cases in endemic countries, PCR detection has confirmed all three parasite species to be more prevalent, and persistent, than previously thought. Chronic, low-density, multispecies asymptomatic infection is a successful biological adaptation by these Plasmodium spp., a pattern also observed among malaria parasites of wild primates. Current whole-genome analyses are illuminating the species barrier separating the ovale parasite species and reveal substantial expansion of subtelomeric gene families. The evidence for and against a quiescent pre-erythrocytic form of P. malariae is reviewed.

Arboviral diseases and malaria in Australia, 2012-13: Annual report of the National Arbovirus and Malaria Advisory Committee.

This report describes the epidemiology of mosquito-borne diseases of public health importance in Australia during the 2012-13 season (1 July 2012 to 30 June 2013) and includes data from human notifications, sentinel chicken, vector and virus surveillance programs. The National Notifiable Diseases Surveillance System received notifications for 9,726 cases of disease transmitted by mosquitoes during the 2012-13 season. The Australasian alphaviruses Barmah Forest virus and Ross River virus accounted for 7,776 (80%) of total notifications. However, over-diagnosis and possible false positive diagnostic test results for these 2 infections mean that the true burden of infection is likely overestimated, and as a consequence, the case definitions were revised, effective from 1 January 2016. There were 96 notifications of imported chikungunya virus infection. There were 212 notifications of dengue virus infection acquired in Australia and 1,202 cases acquired overseas, with an additional 16 cases for which the place of acquisition was unknown. Imported cases of dengue were most frequently acquired in Indonesia. No locally-acquired malaria was notified during the 2012-13 season, though there were 415 notifications of overseas-acquired malaria. There were no cases of Murray Valley encephalitis virus infection in 2012-13. In 2012-13, arbovirus and mosquito surveillance programs were conducted in most jurisdictions with a risk of vectorborne disease transmission. Surveillance for exotic mosquitoes at the border continues to be a vital part of preventing the spread of mosquito-borne diseases such as dengue to new areas of Australia, and in 2012-13, there were 7 detections of exotic mosquitoes at the border.

Clinical implications of a gradual dormancy concept in malaria.

Malaria recurrences after an initially successful therapy and malarial fever occurring a long time after infection are well-known problems in malariology. Currently, two distinct types of malaria recurrences are defined: recrudescence and relapse. A recrudescence is thought to originate from circulating Plasmodium blood stages which do not cause fever before a certain level of a microscopically detectable parasitemia is reached. Contrary, a relapse is thought to originate from quiescent intracellular hepatic parasite stages called hypnozoites. Recrudescences would typically occur in infections due to Plasmodium falciparum. Plasmodium knowlesi, and Plasmodium malariae, whereas relapses would be caused exclusively by Plasmodium vivax and Plasmodium ovale. This schematic view is, however, insufficiently supported by experimental evidence. For instance, hypnozoites of P. ovale have never been experimentally documented. On the other hand, the nonfinding of P. malariae hypnozoites turned into the proof for the nonexistence of P. malariae hypnozoites. Clinical relapse-type recurrences have been observed in both P. ovale and P. malariae infections, and decade-long incubation times have also been reported in P. falciparum infections. We propose a gradual hypothesis in accordance with the continuity concept of biological evolution: both, relapse and recrudescence may be potentially caused by all Plasmodium spp. We hypothesize that the difference between the various Plasmodium spp. is quantitative rather than qualitative: there are Plasmodium spp. which frequently cause relapses such as P. vivax, particularly the P.v. Chesson strain, species which cause relapses less frequently, such as P. ovale and sometimes P. malariae, and species which may exceptionally cause relapses such as P. falciparum. All species may cause recrudescences. As clinical consequences, we propose that 8-aminquinolines may be considered in a relapse-type recrudescence regardless of the causal Plasmodium sp., whereas primaquine relapse prevention might not be routinely indicated in malaria due to P. ovale.

Malaria in children of Tshimbulu (Western Kasai, Democratic Republic of the Congo): epidemiological data and accuracy of diagnostic assays applied in a limited resource setting.

BACKGROUND: The literature data on malaria in Western Kasai, DRC, are limited and inadequate. A recent molecular survey there has detected Plasmodium ovale and Plasmodium malariae as mixed infections with Plasmodium falciparum. In Tshimbulu, Western Kasai, during a humanitarian initiative designed to provide children with free preventive screening and to reduce the local high malaria death rate, accurate species identification was performed, in order to collect unambiguous epidemiological data and to evaluate the reliability of locally applied diagnostics. METHODS: Finger pricks provided fresh blood for microscopic analysis (MA), for rapid diagnostic test (RDT) and for molecular diagnostics (MD). MA and RDT were first performed by the local team and then a re-interpretation of the results (on the same slides and on RDT's taken pictures) was conducted in Italy, where MD were performed. RESULTS: The analysis was conducted on 306 children; RDT found 80.9 % as P. falciparum-positive (37.4 % as two-band positive, P. falciparum single infection). MA identified a further four children as positive to P. falciparum and six co-infections with P. ovale. The second RDT evaluation confirmed a similar infection rate (78.2 %) but interpreted as two-band positive a significantly higher share of tests (56.8 %). MA confirmed 80.0 % of the children as malaria positive and, in addition to P. falciparum, identified P. malariae (13.8 %), P. vivax (3.4 %) and P. ovale (2.4 %), and detected Babesia microti in 19 smears. MD confirmed all of the species found (Babesia microti included), classified as mono-infection with P. falciparum a rate of spots comparable to MA revision, and identified all P. ovale as Plasmodium ovale wallikeri. The RDT used locally proved 93.1 % sensitive and 92.1 % specific for P. falciparum. CONCLUSIONS: The malaria prevalence among the children and the presence of four Plasmodium species, highlighted in this study, identified a sanitary issue which proved to be more alarming than expected, as it was worsened by the unpredictable presence of P. vivax and Babesia microti (never before reported in DRC). Each diagnostic tool showed its point of weakness. Therefore, the most correct approach is by the combined use of different, locally available, diagnostic tools.

Widespread distribution of Plasmodium vivax malaria in Mauritania on the interface of the Maghreb and West Africa.

BACKGROUND: Plasmodium vivax is very rarely seen in West Africa, although specific detection methods are not widely applied in the region, and it is now considered to be absent from North Africa. However, this parasite species has recently been reported to account for most malaria cases in Nouakchott, the capital of Mauritania, which is a large country at the interface of sub-Saharan West Africa and the Maghreb region in northwest Africa. METHODS: To determine the distribution of malaria parasite species throughout Mauritania, malaria cases were sampled in 2012 and 2013 from health facilities in 12 different areas. These sampling sites were located in eight major administrative regions of the country, within different parts of the Sahara and Sahel zones. Blood spots from finger-prick samples of malaria cases were processed to identify parasite DNA by species-specific PCR. RESULTS: Out of 472 malaria cases examined, 163 (34.5 %) had P. vivax alone, 296 (62.7 %) Plasmodium falciparum alone, and 13 (2.8 %) had mixed P. falciparum and P. vivax infection. All cases were negative for Plasmodium malariae and Plasmodium ovale. The parasite species distribution showed a broad spectrum, P. vivax being detected at six of the different sites, in five of the country's major administrative regions (Tiris Zemmour, Tagant, Brakna, Assaba, and the capital Nouakchott). Most cases in Nouakchott were due to P. vivax, although proportions vary significantly among different health facilities in the city. In the northern town of Zouérat, all cases were due to P. vivax, whereas almost all cases in the south of the country were due to P. falciparum. All P. vivax cases tested were Duffy blood group positive. CONCLUSIONS: It is important that P. vivax is recognized to be a widespread cause of malaria in Mauritania, occurring in diverse regions. This should be noted by the World Health Organization, as it has significant implications for diagnosis, treatment and control of malaria in the northwestern part of Africa.

[Laboratory analysis of the first case of imported oval malaria in Rizhao City].

OBJECTIVE: To diagnose the first imported case of Plasmodium ovale infection by laboratory detection. METHODS: The epidemiological data and blood samples of the case were collected, and the samples were detected by the microscopic examination, rapid diagnostic test (RDT) and nested PCR. RESULTS: The patient was a construction worker backing from Congo, Africa. He experienced the symptoms of irregular fever and weakness one month after returning in Lingyang Town, Junxian County. The results of RDT only suggested no-Plasmodium falciparum infection. Under the microscope, it was seen that the infected RBC were obviously disfigured and in irregular shape, the ring forms were thick and big, and also thick granulas in big trophozoite stage and schizont stage were found. The results of PCR showed that the size of amplified product was about 800 bp, which was conformed to that of P. ovale. CONCLUSIONS: Though microscopic examination is the golden standard for malaria diagnosis, as P. ovale is difficult to be identified under microscope, the microscopic method combined with PCR test can be used for definite diagnosis.

Do hypnozoites cause relapse in malaria?

The concept that hypnozoites give rise to relapses in Plasmodium vivax and Plasmodium ovale malaria has become dogma. However, it is evident from particular contemporary research findings that hypnozoites are not necessarily the origin of all relapse-like recurrences of malaria caused by these parasites. This is the core opinion presented, and I discuss it fully. The hypnozoite theory of relapse needs to be re-evaluated in view of the recent, increased focus on P. vivax and liver stages of Plasmodium. Hypnozoites have also assumed a new significance because they might, by facilitating ongoing transmission, be a threat to the current (post-2007) goal of eliminating malaria globally. I have suggested some new research directions for finding putative nonhypnozoite sources of recurrent malaria.

Dimorphism in genes encoding sexual-stage proteins of Plasmodium ovale curtisi and Plasmodium ovale wallikeri.

Plasmodium ovale curtisi and Plasmodium ovale wallikeri are distinct species of malaria parasite which are sympatric throughout the tropics, except for the Americas. Despite this complete overlap in geographic range, these two species do not recombine. Although morphologically very similar, the two taxa must possess distinct characters which prevent recombination between them. We hypothesised that proteins required for sexual reproduction have sufficiently diverged between the two species to prevent recombination in any mosquito blood meal in which gametocytes of both species are ingested. In order to investigate possible barriers to inter-species mating between P. ovale curtisi and P. ovale wallikeri, homologues of genes encoding sexual stage proteins in other plasmodia were identified and compared between the two species. Database searches with motifs for 6-cysteine, Limulus Coagulation factor C domain-containing proteins and other relevant sexual stage proteins in the genus Plasmodium were performed in the available P. ovale curtisi partial genome database (Wellcome Trust Sanger Institute, UK). Sequence fragments obtained were used as the basis for PCR walking along each gene of interest in reference isolates of both P. ovale curtisi and P. ovale wallikeri. Sequence alignment of the homologues of each gene in each species showed complete dimorphism across all isolates. In conclusion, substantial divergence between sexual stage proteins in the two P. ovale spp. was observed, providing further evidence that these do not recombine in nature. Incompatibility of proteins involved in sexual development and fertilisation thus remains a plausible explanation for the observed lack of natural recombination between P. ovale curtisi and P. ovale wallikeri.

A 20-year longitudinal study of Plasmodium ovale and Plasmodium malariae prevalence and morbidity in a West African population.

BACKGROUND: Plasmodium ovale and Plasmodium malariae have long been reported to be widely distributed in tropical Africa and in other major malaria-endemic areas of the world. However, little is known about the burden caused by these two malaria species. METHODS AND FINDINGS: We did a longitudinal study of the inhabitants of Dielmo village, Senegal, between June, 1990, and December, 2010. We monitored the inhabitants for fever during this period and performed quarterly measurements of parasitemia. We analyzed parasitological and clinical data in a random-effect logistic regression model to investigate the relationship between the level of parasitemia and the risk of fever and to establish diagnostic criteria for P. ovale and P. malariae clinical attacks. The prevalence of P. ovale and P. malariae infections in asymptomatic individuals were high during the first years of the project but decreased after 2004 and almost disappeared in 2010 in relation to changes in malaria control policies. The average incidence densities of P. ovale and P. malariae clinical attacks were 0.053 and 0.093 attacks per person per year in children <15 years and 0.024 and 0.009 attacks per person per year in adults ≥ 15 years, respectively. These two malaria species represented together 5.9% of the malaria burden. CONCLUSIONS: P. ovale and P. malariae were a common cause of morbidity in Dielmo villagers until the recent dramatic decrease of malaria that followed the introduction of new malaria control policies. P. ovale and P. malariae may constitute an important cause of morbidity in many areas of tropical Africa.

Two cases of late Plasmodium ovale presentation in military personnel.

Only a few late cases of Plasmodium ovale presentation have been reported in literature. We describe two cases of late P. ovale presentation occurring in two French military personnel, 47 and 69 months, respectively, after a stay in Côte d'Ivoire and in the absence of new intercurrent malaria exposure.

[A case of Plasmodium ovale malaria--morphological diagnostic difficulty and utility of rapid diagnostic tests].

A 46-year-old Japanese man was referred to our travel clinic because of high fever for the past 7 days. He worked as an engineer for a month in Zambia and returned to Japan 2 days ago. He had a high-grade fever of 40.5 degrees C. Examination of the palpebral conjunctiva showed no evidence of anemia. Liver and spleen were not palpable. Blood sample was collected at the time of the febrile paroxysm. Malaria parasites were detected by examination of Giemsa-stained thin blood films. The dominant feature of parasite was early trophozoit with a low parasitemia (0.0469%, 1,857.6/microL). The James' stippling was absent. Schizonts and gametocytes were scarce. As ring morphology was quite variable, identification of species might not be possible. Identification of species is more difficult than usual, on the grounds that: 1) the blood sample contains rare early trophozoites, 2) the level of parasitemia is low, and 3) it is quite possible for parasites to be transformed due to the inappropriate treatment. Finally, the diagnosis was confirmed by nested PCR. Examination of Giemsa-stained blood films is the "gold standard" for detection and identification of organisms. However, in non-endemic countries, trained laboratory personnel are scarce and the most may be inexperienced in malaria diagnosis. It is recommended that personnel continue to gain experience by participating in external quality assurance schemes, and that routine laboratories utilize rapid diagnostic tests (RDTs) concurrently. The availability of simple and accurate RDTs could aid the diagnosis in no-endemic countries.

Variant Plasmodium ovale isolated from a patient infected in Ghana.

Recent data have found that Plasmodium ovale can be separated in two distinct species: classic and variant P. ovale based on multilocus typing of different genes. This study presents a P. ovale isolate from a patient infected in Ghana together with an analysis of the small subunit RNA, cytochrome b, cytochrome c oxidase I, cysteine protease and lactate dehydrogenase genes, which show that the sample is a variant P. ovale and identical or highly similar to variant P. ovale isolated from humans in South-East Asia and Africa, and from a chimpanzee in Cameroon. The split between the variant and classic P. ovale is estimated to have occurred 1.7 million years ago.