The challenge of diagnosing Plasmodium ovale malaria in travellers: report of six clustered cases in French soldiers returning from West Africa

A cross-sectional analysis identifies a low prevalence of Plasmodium ovale curtisi infections in symptomatic and asymptomatic individuals in Kilifi county, Kenya

Background: The focus on P. falciparum diagnosis has led to an underestimation of the global burden of malaria resulting from neglected Plasmodium species. However, there is still scarce data on the prevalence of P. ovale globally. To address this knowledge gap, data collected from cross-sectional studies in Kilifi county were used to: 1) determine the prevalence of P. ovale curtisi infections; and 2) determine the sensitivity of different diagnostic assays in detecting P. ovale curtisi infections. Methods: A total of 531 individuals were sampled across three study sites in Kilifi County, Kenya between 2009 and 2020. Blood smears were prepared from peripheral blood and screened for Plasmodium parasite stages using light microscopy. Molecular screening involved DNA extraction of dried blood spots and blood in ethylenediaminetetraacetic acid, polymerase chain reaction (PCR) using primers targeting the 18 small ribosomal subunit and sequencing. Results: Microscopy screening revealed that the most prevalent species was P. falciparum (32.0%) followed by P. malariae (9.0%) and then P. ovale (1.5%). PCR screening identified additional P. ovale curtisi positives cases. Overall, 48 (8.2%) out of the 531 individuals harbored P. ovale curtisi infection with the highest prevalence reported in the tertiary health facility, (14.6%, 95% CI 8-23.6%), followed by the primary health facility (8.6%, 95% CI 5.4-11.9%), and the community from a cross-sectional blood survey, (6.5%, 95% CI 3.0-11.8%). Microscopy screening for P. ovale had a low sensitivity of 7% (95% CI 1-19-30%) and a high specificity of 99% (95% CI 98-100%). Sequencing results confirmed the presence of P.ovale curtisi. Conclusions: This study provides baseline data for P.ovale curtisi surveillance  in Kilifi County, primarily using PCR to improve diagnosis. These results suggest that malaria elimination and eradication efforts should not only concentrate on P. falciparum but should embrace a holistic approach towards elimination of all Plasmodium species.

Increasing proportions of relapsing parasite species among imported malaria in China's Guangxi Province from Western and Central Africa

BACKGROUND

Travel-related malaria in non-endemic areas returning from endemic areas presents important challenges to diagnosis and treatment. Imported malaria to newly malaria-free countries poses further threats of malaria re-introduction and potential resurgence. For those traveling to places with high Plasmodium falciparum prevalence, prophylaxis against this parasite is recommended, whereas causal prophylaxis against relapsing malaria is often overlooked.

METHODS

We analyzed a cluster of imported malaria among febrile patients in Shanglin County, Guangxi Province, China, who had recent travel histories to Western and Central Africa. Malaria was diagnosed by microscopy and subsequently confirmed by species- and subspecies-specific PCR. Plasmodium vivax was genotyped using a barcode consisting of 42 single nucleotide polymorphisms.

RESULTS

Investigations of 344 PCR-confirmed malaria cases revealed that in addition to Plasmodium falciparum being the major parasite species, the relapsing parasites Plasmodium ovale and P. vivax accounted for ~40% of these imported cases. Of the 114 P. ovale infections, 65.8% and 34.2% were P. ovale curtisi and P. ovale wallikeri, respectively, with the two subspecies having a ~2:1 ratio in both Western and Central Africa. Phylogenetic analysis of 14 P. vivax isolates using a genetic barcode demonstrated that 11 formed a distinct clade from P. vivax populations from Eastern Africa.

CONCLUSION

This study provides support for active P. vivax transmission in areas with the predominant Duffy-negative blood group. With relapsing malaria making a substantial proportion of the imported malaria, causal prophylaxis should be advocated to travelers with a travel destination to Western and Central Africa.

Severity and mortality of severe Plasmodium ovale infection: A systematic review and meta-analysis

Plasmodium ovale can infect humans, causing malaria disease. We aimed to investigate the severity and mortality of severe P. ovale infection to increase the awareness of physicians regarding the prognosis of this severe disease and outcome-related deaths in countries in which this disease is endemic. Articles that were published in the PubMed, Scopus, and ISI Web of Science databases prior to January 5, 2020 and reported the prevalence of severe P. ovale infection were systematically searched and reviewed. Studies that mainly reported severe P. ovale infection according to the 2014 WHO criteria for the treatment of malaria were included. Two reviewers selected, identified, assessed, and extracted data from studies independently. The pooled prevalence of severe P. ovale mono-infections was estimated using the command “metaprop case population, random/fixed”, which yielded the pooled estimate, 95% confidence interval (CI) and the I² value, indicating the level of heterogeneity. Meta-analyses of the proportions were performed using a random-effects model to explore the different proportions of severity between patients with P. ovale and those with other Plasmodium species infections. Among the eight studies that were included and had a total of 1,365 ovale malaria cases, the pooled prevalence of severe P. ovale was 0.03 (95% CI = 0.03–0.05%, I² = 54.4%). Jaundice (1.1%), severe anemia (0.88%), and pulmonary impairments (0.59%) were the most common severe complications found in patients infected with P. ovale. The meta-analysis demonstrated that a smaller proportion of patients with P. ovale than of patients with P. falciparum had severe infections (P-value = 0.01, OR = 0.36, 95% CI = 0.16–0.81, I² = 72%). The mortality rate of severe P. ovale infections was 0.15% (2/1,365 cases). Although severe complications of P. ovale infections in patients are rare, it is very important to increase the awareness of physicians regarding the prognosis of severe P. ovale infections in patients, especially in a high-risk population.

A cluster of the first reported Plasmodium ovale spp. infections in Peru occuring among returning UN peace-keepers, a review of epidemiology, prevention and diagnostic challenges in nonendemic regions

BACKGROUND

Plasmodium ovale curtisi and Plasmodium ovale wallikeri are regarded as less virulent forms of malaria with a geographic distribution including Southeast Asia, Central and West Africa, and is increasingly reported as an infection in returning travellers. A species of malaria that may have delayed or relapsing presentations similar to Plasmodium vivax, the clinical presentation of P. ovale spp. has been described to have prepatent periods of 2 weeks or slightly longer with reports of relapse following primary infection out to 8-9 months. This presentation may be obscured further in the setting of anti-malarial exposure, with report of delayed primary infection out to 4 years. Presented is a cluster of 4 imported P. ovale spp. cases in returning Peruvian military personnel assigned to United Nations peace-keeping operations in the Central African Republic.

CASE PRESENTATION

From January to December 2016, Peruvian peace-keepers were deployed in support of United Nations (UN) operations in the Central African Republic (CAR). While serving abroad, Navy, Army, and Air Force members experienced 223 episodes of Plasmodium falciparum malaria following interruption of prophylaxis with mefloquine. Diagnosis was made using rapid diagnostics tests (RDTs) and/or smear with no coinfections identified. Cases of malaria were treated with locally-procured artemether-lumefantrine. Returning to Peru in January 2017, 200 peace-keepers were screened via thick and thin smear while on weekly mefloquine prophylaxis with only 1 showing nucleic acid within red blood cells consistent with Plasmodium spp. and 11 reporting syndromes of ill-defined somatic complaints. Between a period of 5 days to 11 months post return, 4 cases of P. ovale spp. were diagnosed using smear and polymerase chain reaction (PCR) following febrile complaints. All cases were subsequently treated with chloroquine and primaquine, with cure of clinical disease and documented clearance of parasitaemia.

CONCLUSION

These patients represent the first imported cases in Peru of this species of malaria as well as highlight the challenges in implementing population level prophylaxis in a deployed environment, and the steps for timely diagnosis and management in a non-endemic region where risk of introduction for local transmission exists.

Novel high resolution melting (HRM) and snapback assays for simultaneous detection and differentiation of Plasmodium ovale spp

Plasmodium ovale spp. are two of the six species of apicomplexan parasites belonging to the genus Plasmodium commonly causing disease in humans. A recent phylogeny study has identified both Plasmodium ovale species (P. ovale curtisi and P. ovale wallikeri) as two sympatric occurring species. The actual prevalence and clinical relevance of P. ovale spp. are likely underestimated due to low parasitemia and mixed infections, which pose a major challenge to microscopic diagnosis and are frequently undetectable using malaria Rapid Diagnostic Tests (RDTs). The aim of this work is to develop a HRM-based assay for simultaneous detection and differentiation of P. ovale wallikeri and P. ovale curtisi. Thirty three well-documented P. ovale spp. samples from previous studies were used for this study. The newly developed High Resolution Melting (HRM) assay targeting the apicoplast genome was highly specific to both P. ovale species. Adding a snapback tail at the 5' end of the forward primer for a nested HRM PCR, increased the melting temperature (Tm) difference between the two species. To our knowledge this study reports the first direct HRM assay developed on the apicoplast genome, specific for both P. ovale species. This method provides added value to the WHO open request of developing new practical malaria diagnostic methods for the malaria elimination program and could contribute to a quick and efficient diagnosis of low-level parasitemia, symptomatic or asymptomatic, as well as mixed or single P. ovale infections.

Utility of pf/pan RDT for diagnosis in the prevention of re-establishment of malaria in Sri Lanka

The utility of CareStartTM Malaria Pf/PAN (HRP2/pLDH) Ag Combo Test, in detecting non-endemic clinical malaria cases was evaluated in Sri Lanka, a country in prevention of re-establishment of malaria following elimination. RDT, microscopy and nested PCR were performed for 350 suspected malaria patients recruited prospectively. There were 173 PCR confirmed malaria patients and 177 PCR negative subjects. Plasmodium falciparum amounted to 48% of infections with 44% P. vivax, 6% P. ovale and 2% P. malariae. Performance characteristics of RDTs and microscopy were compared with nested PCR. Sensitivity and specificity of RDT with 95% confidence intervals (CI) were as follows: any malaria infection 95.95% (CI = 91.84-98.36) and 94.92% (CI = 90.57-97.65); P. falciparum 100% (CI = 95.65-100) and 97.00% (CI = 94.18-98.70) and other species 92.22% (CI = 84.63-96.82) and 99.62% (97.88-99.99) respectively. A significant difference between sensitivities of HRP2 (100%, CI = 95.65-100) and pan pLDH line (68.67%, CI = 57.56-78.41) was seen for P. falciparum, parasite densities less than 1000 parasites/microliter being detected only by HRP2. Sensitivity and specificity of microscopy with 95% CI were as follows: any malaria infection, 94.22% (CI = 89.63-97.19) and 99.44% (CI = 96.89-99.99); P. falciparum 89.16% (CI = 80.40-94.90) and 99.63% (CI = 97.94-99.99); other species 98.89% (CI = 93.96-99.97) and 100% (CI = 98.59-100) respectively. The low sensitivity of pan specific pLDH for P. falciparum, P. ovale and P. malariae should be taken in to consideration when using this RDT as a point of care test when and wherever microscopy facilities are not readily available. Considering the low sensitivity of microscopy for P. falciparum, it is preferable to perform both tests, when malaria is highly suspected.

Management of Acute Diarrheal Illness During Deployment: A Deployment Health Guideline and Expert Panel Report

BACKGROUND

Acute diarrheal illness during deployment causes significant morbidity and loss of duty days. Effective and timely treatment is needed to reduce individual, unit, and health system performance impacts.

METHODS

This critical appraisal of the literature, as part of the development of expert consensus guidelines, asked several key questions related to self-care and healthcare-seeking behavior, antibiotics for self-treatment of travelers' diarrhea, what antibiotics/regimens should be considered for treatment of acute watery diarrhea and febrile diarrhea and/or dysentery, and when and what laboratory diagnostics should be used to support management of deployment-related travelers' diarrhea. Studies of acute diarrhea management in military and other travelers were assessed for relevance and quality. On the basis of this critical appraisal, guideline recommendations were developed and graded by the Expert Panel using good standards in clinical guideline development methodology.

RESULTS

New definitions for defining the severity of diarrhea during deployment were established. A total of 13 graded recommendations on the topics of prophylaxis, therapy and diagnosis, and follow-up were developed. In addition, four non-graded consensus-based statements were adopted.

CONCLUSIONS

Successful management of acute diarrheal illness during deployment requires action at the provider, population, and commander levels. Strong evidence supports that single-dose antimicrobial therapy is effective in most cases of moderate to severe acute diarrheal illness during deployment. Further studies are needed to address gaps in available knowledge regarding optimal therapies for treatment, prevention, and laboratory testing of acute diarrheal illness.

'Holiday sickness'-reported exploratory outcome of over 500 United Kingdom holidaymakers with travellers' diarrhoea

AIMS

To ascertain any predictors of potential food poisoning pathogens and development of post-infective irritable bowel syndrome (IBS) in UK travellers. An analysis was undertaken on prospectively collected data on 527 patients reporting symptoms of suspected food poisoning between June 2012 and June 2015.

MAIN OUTCOME MEASURES

Positive stool sample indicative of food poisoning pathogens and diagnosis of post-infective IBS.

RESULTS

Data on 527 patients were examined. The large majority of patients did not provide a stool sample on return from holiday (n = 430, 81.6%) as few visited a Doctor locally or in the UK. Only 18 patients (18.6%, 95% confidence interval [CI] 11.4-27.7) who provided a stool sample were positive for microbiological food poisoning pathogens. Univariate analysis indicated a significant relationship between a positive stool sample and whether the individual sought any medical assistance at the resort (odds ratio [OR] 0.24, 95% CI 0.08-0.70) and whether they took any treatment (including self-medicated), (OR 0.21, 95% CI 0.06-0.67). Of the 527 patients only 30 (5.7%, 95% CI 3.9-8.1) experienced post-infective IBS. Univariate regression indicated a significant relationship between experiencing Per Rectal (PR) bleeding and a diagnosis of post-infective IBS (OR 3.64, 95% CI 1.00-10.49). Univariate regression also indicated an increase in the risk of developing post-infective IBS with increasing duration of symptoms (OR 1.04, 95% CI 1.02-1.05). No significant relationship was found between a positive stool sample and developing post-infective IBS (P = 0.307).

CONCLUSIONS

Very few patients provide a stool sample after experiencing holiday sickness abroad. Of those that do, only a small proportion have a positive stool sample indicative of a food poisoning microorganism. Around 6% of individuals were diagnosed with post-infective IBS. Those individuals with PR bleeding and symptoms persisting for longer durations were significantly more at risk of developing post-infective IBS, whilst medical aid and treatment abroad was found to reduce the odds of a positive stool sample.

Molecular characterization of misidentified Plasmodium ovale imported cases in Singapore

BACKGROUND

Plasmodium ovale, considered the rarest of the malaria parasites of humans, consists of two morphologically identical but genetically distinct sympatric species, Plasmodium ovale curtisi and Plasmodium ovale wallikeri. These parasites resemble morphologically to Plasmodium vivax with which they also share a tertian periodicity and the ability to cause relapses, making them easily misidentified as P. vivax. Plasmodium ovale infections are rarely reported, but given the likelihood of misidentification, their prevalence might be underestimated.

METHODS

Morphological and molecular analysis of confirmed malaria cases admitted in Singapore in 2012-2014 detected nine imported P. ovale cases that had been misidentified as P. vivax. Since P. ovale had not been previously officially reported in Singapore, a retrospective analysis of available, frozen, archival blood samples was performed and returned two additional misidentified P. ovale cases in 2003 and 2006. These eleven P. ovale samples were characterized with respect to seven molecular markers (ssrRNA, Potra, Porbp2, Pog3p, dhfr-ts, cytb, cox1) used in recent studies to distinguish between the two sympatric species, and to a further three genes (tufa, clpC and asl).

RESULTS

The morphological features of P. ovale and the differential diagnosis with P. vivax were reviewed and illustrated by microphotographs. The genetic dimorphism between P. ovale curtisi and P. ovale wallikeri was assessed by ten molecular markers distributed across the three genomes of the parasite (Genbank KP050361-KP050470). The data obtained for seven of these markers were compared with those published and confirmed that both P. ovale species were present. This dimorphism was also confirmed for the first time on: (1) two genes from the apicoplast genome (tufA and clpC genes); and, (2) the asl gene that was used for phylogenetic analyses of other Plasmodium species, and that was found to harbour the highest number of dimorphic loci between the two P. ovale species.

CONCLUSION

Misidentified P. ovale infections are reported for the first time among imported malaria cases in Singapore. Genetic dimorphism between P. ovale curtisi and P. ovale wallikeri was confirmed using markers from the parasites' three genomes. The apparent increase of imported P. ovale since 2012 (with yearly detection of cases) is puzzling. Given decrease in the overall number of malaria cases recorded in Singapore since 2010 the 'resurgence' of this neglected species raises public health concerns.

Characterization of Plasmodium ovale curtisi and P. ovale wallikeri in Western Kenya utilizing a novel species-specific real-time PCR assay

Background

Plasmodium ovale is comprised of two genetically distinct subspecies, P. ovale curtisi and P. ovale wallikeri. Although P. ovale subspecies are similar based on morphology and geographical distribution, allelic differences indicate that P. ovale curtisi and P. ovale wallikeri are genetically divergent. Additionally, potential clinical and latency duration differences between P. ovale curtisi and P. ovale wallikeri demonstrate the need for investigation into the contribution of this neglected malaria parasite to the global malaria burden.

Methods

In order to detect all P. ovale subspecies simultaneously, we developed an inclusive P. ovale-specific real-time PCR assay based on conserved regions between P. ovale curtisi and P. ovale wallikeri in the reticulocyte binding protein 2 (rbp2) gene. Additionally, we characterized the P. ovale subspecies prevalence from 22 asymptomatic malaria infections using multilocus genotyping to discriminate P. ovale curtisi and P. ovale wallikeri.

Results

Our P. ovale rbp2 qPCR assay validation experiments demonstrated a linear dynamic range from 6.25 rbp2 plasmid copies/microliter to 100,000 rbp2 plasmid copies/microliter and a limit of detection of 1.5 rbp2 plasmid copies/microliter. Specificity experiments showed the ability of the rbp2 qPCR assay to detect low-levels of P. ovale in the presence of additional malaria parasite species, including P. falciparum, P. vivax, and P. malariae. We identified P. ovale curtisi and P. ovale wallikeri in Western Kenya by DNA sequencing of the tryptophan-rich antigen gene, the small subunit ribosomal RNA gene, and the rbp2 gene.

Conclusions

Our novel P. ovale rbp2 qPCR assay detects P. ovale curtisi and P. ovale wallikeri simultaneously and can be utilized to characterize the prevalence, distribution, and burden of P. ovale in malaria endemic regions. Using multilocus genotyping, we also provided the first description of the prevalence of P. ovale curtisi and P. ovale wallikeri in Western Kenya, a region holoendemic for malaria transmission.

Humans can be infected with five malaria parasite species: Plasmodium falciparum, P. vivax, P. malariae, P. knowlesi, and P. ovale. Although the vast majority of malaria morbidity and mortality worldwide can be attributed to P. falciparum, non-falciparum malaria parasites can also cause clinical disease. Researchers use nucleic acid based detection methods, such a polymerase chain reaction (PCR), to detect low-density malaria parasitemias that can evade microscopic detection. P. ovale was recently identified to exist as two subspecies, P. ovale curtisi and P. ovale wallikeri, that look identical but differ genetically. In this study, we developed a novel real-time PCR (qPCR) assay to detect all P. ovale parasites, based on a conserved gene between P. ovale curtisi and P. ovale wallikeri. We also used DNA sequencing to differentiate between P. ovale curtisi and P. ovale wallikeri from a small sample of P. ovale asymptomatic infections in Western Kenya. Through the use of our novel rbp2 qPCR assay, we aim to characterize the prevalence of P. ovale in future epidemiological studies in order to better understand this neglected malaria parasite species.

First imported Plasmodium ovale malaria in Central America: case report of a Guatemalan soldier and a call to improve its accurate diagnosis

The Mesoamerican Ministers of Health have set 2020 as the target for malaria elimination to be achieved in the region. Imported malaria cases are a potential threat to countries attempting elimination or working to prevent resurgence. We report the first imported Plasmodium ovale infection with molecular confirmation in Central America, which occurred in a Guatemalan soldier that had been deployed in Africa. The obstacles for its diagnosis using the standard microscopy technique and the need to improve its detection are discussed.

Prevention of infectious diseases during military deployments: a review of the French armed forces strategy

Military personnel in operations have always paid a high toll to infections. In the 21st century some of these diseases still cause outbreaks with significant morbidity and impact on deployments. The new configuration of the French Armed Forces requires the permanent preparedness of deployable units. During deployments, soldiers are at least exposed to the infectious diseases that are observed in travellers, but with a potentially severe impact for the combatting strengths and a risk for cancelation or failure of the operational durability. The most common disabling infections during military deployments are faeco-oral transmitted diseases including diarrhoea. Preventing infectious diseases during deployments is of great concern and the French medical service has established a strategy based on different components; risk assessment and preparation, immunizations, protective measures and chemoprophylaxis, health education, health surveillance, outbreak investigations and medical tracking. In this review, the authors present the context of deployment of the French Armed Forces, the main health risks they are exposed to and develop the key points of the force health protection strategy, focused on infections related to military deployments.

Malaria control strategies in French armed forces

Each year, 40,000 French soldiers deploy or travel through malaria-endemic areas. Despite the effective control measures that were successively implemented, malaria remains a public health concern in French armed forces with several important outbreaks and one lethal case every two years. This article describes the malaria control strategy in French armed forces which is based on three combined strategies: i) Anopheles vector control to prevent infection with the implementation of personal protection against vectors (PPAV) adapted to the field living conditions of the troops. ii) Chemoprophylaxis (CP) to prevent the disease based on prescription of effective and well tolerated doxycycline. iii) Management of cases through early diagnosis and appropriate treatment to prevent death. In isolated conditions in endemic areas, rapid diagnosis tests (RDT) are used as first-line tests by military doctors. Treatment of uncomplicated Plasmodium falciparum (P. falciparum) malaria is based either on the piperaquine tetraphosphate-dihydroartemisinin association since 2013, or on the atovaquone-proguanil association. First-line treatment of severe P. falciparum malaria is based on IV artesunate. These measures are associated with constant education of the military, epidemiological surveillance of malaria cases and monitoring of parasite chemosensitivity.

New type of SSUrDNA sequence was detected from both Plasmodium ovale curtisi and Plasmodium ovale wallikeri samples

BACKGROUND

Plasmodium ovale is relatively unfamiliar to Chinese staff engaged in malaria diagnosis. In 2013, dried blood spots of four unidentified but suspected ovale malaria samples were sent to the National Malaria Reference Laboratory (NMRL) for reconfirmation.

METHODS

Partial and complete, small, subunit ribosomal DNA (SSU rDNA) sequences of four samples were obtained with PCR-cloning-sequencing method. Obtained sequences were analyzed by aligning with each other and with nine SSU rDNA sequences of six known Plasmodium parasites. A phylogenetic tree was constructed based on complete SSU rDNA sequences and 12 same gene sequences derived from six known Plasmodium parasites and three Babesia parasites. Primary structure of conservative and variable regions of variant sequences was determined also by comparing them with those of six known Plasmodium parasites. To confirm their existence in genome, they were redetected with primers matching their variable regions. PCR systems aimed to roughly detect any eukaryotes and prokaryotes respectively were also applied to search for other pathogens in one of four patients.

RESULTS

Totally, 19 partial and 23 complete SSU rDNA sequences obtained from four samples. Except eight variant sequences, similarities among sequences from same DNA sample were in general high (more than 98%). The phylogenetic analysis revealed that three cases were infected by P. ovale wallikeri and one by P. ovale curtisi. Four of the variant sequences which obtained from four samples relatively showed high similarities with each other (98.5%-100%). Identical variant sequences actually could be re-obtained from each DNA sample. Their primary structure of conservative and variable regions showed quite fit with that of six known Plasmodium parasites. The test for prokaryote pathogens showed negative and the tests for eukaryotes only found DNA sequences of Human and P. ovale parasites.

CONCLUSION

Both P. ovale wallikeri and P. ovale curtisi infections are present in imported malaria cases of China. New type of partial SSU rDNA sequence which assumed to express in a certain life stage of P. ovale was obtained from both P. ovale wallikeri and P. ovale curtisi samples. This discovery would supply information and clues to identify and understand P. ovale parasites more accurately.

Emergence of Plasmodium ovale malaria among the French Armed Forces in the Republic of Ivory Coast: 20 years of clinical and biological experience

BACKGROUND

French military surveillance identified an increase in Plasmodium ovale attacks among soldiers in Ivory Coast. This emergence and the low sensitivity of biological tests raise the question of a possible role of P. ovale variant species.

METHODS

Epidemiological data about P. ovale attacks from 1993 to 2012 were studied; the species diagnosis was based on a thin blood smear and/or a quick diagnostic test. Clinical and biological features in soldiers hospitalized in 2 French military hospitals were also reviewed. Malaria polymerase chain reaction followed by genotyping was performed when available.

RESULTS

French military physicians declared 328 P. ovale attacks over the 20-year study. A peak of incidence occurred in 2005. Among patients with positive blood smears, the quick diagnostic test was positive in 33 of 101 tests performed. The hospital study showed that symptoms and biological changes were not specific, which made diagnosis challenging: fever, anemia, and thrombocytopenia were not present in 20%, 71%, and 23% of the 45 confirmed cases, respectively. It was possible to perform molecular investigations on 19 clinical isolates: 18 were classic haplotypes with additional polymorphism and 1 was variant.

CONCLUSIONS

This emergence of P. ovale malaria enabled a good description to be made in nonimmune patients. The lack of sensitivity of both clinical features and quick diagnostic tests suggests an underestimation. Reasons for this outbreak are especially intense exposure to the vectors and the insufficient efficacy of doxycycline against P. ovale. The polymorphism of classic haplotypes of P. ovale rather than variant forms could be involved.