Failure of primaquine therapy for the treatment of Plasmodium ovale malaria

Malaria parasite species composition of Plasmodium infections among asymptomatic and symptomatic school-age children in rural and urban areas of Kinshasa, Democratic Republic of Congo

BACKGROUND

Malaria remains a major public health concern in the Democratic Republic of Congo (DRC), and school-age children are relatively neglected in malaria prevalence surveys and may constitute a significant reservoir of transmission. This study aimed to understand the burden of malaria infections in school-age children in Kinshasa/DRC.

METHODS

A total of 634 (427 asymptomatic and 207 symptomatic) blood samples collected from school-age children aged 6 to 14 years were analysed by microscopy, RDT and Nested-PCR.

RESULTS

The overall prevalence of Plasmodium spp. by microscopy, RDT and PCR was 33%, 42% and 62% among asymptomatic children and 59%, 64% and 95% in symptomatic children, respectively. The prevalence of Plasmodium falciparum, Plasmodium malariae and Plasmodium ovale spp. by PCR was 58%, 20% and 11% among asymptomatic and 93%, 13% and 16% in symptomatic children, respectively. Among P. ovale spp., P. ovale curtisi, P. ovale wallikeri and mixed P. ovale curtisi + P. ovale wallikeri accounted for 75%, 24% and 1% of infections, respectively. All Plasmodium species infections were significantly more prevalent in the rural area compared to the urban area in asymptomatic infections (p < 0.001). Living in a rural as opposed to an urban area was associated with a five-fold greater risk of asymptomatic malaria parasite carriage (p < 0.001). Amongst asymptomatic malaria parasite carriers, 43% and 16% of children harboured mixed Plasmodium with P. falciparum infections in the rural and the urban areas, respectively, whereas in symptomatic malaria infections, it was 22% and 26%, respectively. Few children carried single infections of P. malariae (2.2%) and P. ovale spp. (1.9%).

CONCLUSION

School-age children are at significant risk from both asymptomatic and symptomatic malaria infections. Continuous systematic screening and treatment of school-age children in high-transmission settings is needed.

Molecular evidence for relapse of an imported Plasmodium ovale wallikeri infection

Background

Malaria caused by Plasmodium ovale spp. has been neglected by and large from research and has received only little scientific attention during the past decades. Ovale malaria is considered to feature relapses by liver hypnozoites although scientific evidence for this paradigm is scarce.

Case presentation

Here, the case of a 16-year-old male, who presented with fevers to the outpatient department in Vienna, Austria, after travelling to Uganda and Papua New Guinea is described. Infection with Plasmodium malariae was diagnosed by microscopy and the patient was treated accordingly with a full course of supervised artemether–lumefantrine. He was discharged in good clinical condition with a negative blood smear. One month after initial diagnosis, he returned complaining of fever. Thick blood smear was positive again for malaria parasites, which were confirmed as P. ovale wallikeri by PCR. Retrospective analysis revealed the identical Plasmodium spp. in the initial blood samples. Molecular analysis of various gene loci (nuclear porbp2, 18S rRNA and potra genes) gave identical results providing further evidence for relapse by an identical parasite genotype. Consecutively, the patient was retreated with artemether–lumefantrine and received a regimen of primaquine according to WHO guidelines.

Conclusion

Conclusive evidence for relapses with P. ovale spp. is rare. The presented case provides convincing confirmation for the relapse paradigm based on re-appearing parasitaemia following supervised treatment in a non-endemic region with a parasite strain of identical genotype.

A systematic review of the clinical presentation, treatment and relapse characteristics of human Plasmodium ovale malaria

BACKGROUND

Despite increased efforts to control and ultimately eradicate human malaria, Plasmodium ovale malaria is for the most part outside the focus of research or public health programmes. Importantly, the understanding of P. ovale-nowadays regarded as the two distinct species P. ovale wallikeri and P. ovale curtisi-largely stems from case reports and case series lacking study designs providing high quality evidence. Consecutively, there is a lack of systematic evaluation of the clinical presentation, appropriate treatment and relapse characteristics of P. ovale malaria. The aim of this systematic review is to provide a systematic appraisal of the current evidence for severe manifestations, relapse characteristics and treatment options for human P. ovale malaria.

METHODS AND RESULTS

This systematic review was performed according to the PRISMA guidelines and registered in the international prospective register for systematic reviews (PROSPERO 2016:CRD42016039214). P. ovale mono-infection was a strict inclusion criterion. Of 3454 articles identified by the literature search, 33 articles published between 1922 and 2015 met the inclusion criteria. These articles did not include randomized controlled trials. Five prospective uncontrolled clinical trials were performed on a total of 58 participants. P. ovale was sensitive to all tested drugs within the follow-up periods and on interpretable in vitro assays. Since its first description in 1922, only 18 relapsing cases of P. ovale with a total of 28 relapse events were identified in the scientific literature. There was however no molecular evidence for a causal relationship between dormant liver stages and subsequent relapses. A total of 22 severe cases of P. ovale malaria were published out of which five were fatal. Additionally, two cases of congenital P. ovale malaria were reported.

CONCLUSIONS

Current knowledge of P. ovale malaria is based on small trials with minor impact, case reports and clinical observations. This systematic review highlights that P. ovale is capable of causing severe disease, severe congenital malaria and may even lead to death. Evidence for relapses in patients with P. ovale malaria adds up to only a handful of cases. Nearly 100 years after P. ovale's first description by Stephens the evidence for the clinical characteristics, relapse potential and optimal treatments for P. ovale malaria is still scarce.

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.

Optimal primaquine use for radical cure of Plasmodium vivax and Plasmodium ovale malaria in Japanese travelers--A retrospective analysis

BACKGROUND

Recently, a dose of 30 mg (base) primaquine daily for 14 days is increasingly recommended for radical cure of Plasmodium vivax malaria. However, total primaquine doses, or those per body weight, are also recognized as important. In Japan, primaquine is not a licensed medicine, but has been used through the Research Group on Chemotherapy of Tropical Diseases for >3 decades.

METHODS

Based on clinical records submitted to the Research Group, patients with P. vivax and Plasmodium ovale malaria treated with primaquine were analyzed to determine the efficacy and safety of the antimalarial drug.

RESULTS

Seventy-five P. vivax cases, including 3 in children, and 19 P. ovale cases were enrolled. Five of the P. vivax cases demonstrated at least one relapse despite primaquine therapy. Total primaquine doses per body weight were obtained in 4 of the 5 relapsed patients, presenting 9 malaria episodes totally, and most of the primaquine failures were caused with a total dose ≤ 3.5 mg/kg. Liver function disturbance was reported in 2 cases.

CONCLUSION

In order to optimize radical cure of P. vivax, the total primaquine dose per body weight should be considered, at least 3.5 mg/kg or even more if contracted in countries with significant drug resistance. Possibility of primaquine hepatotoxicity in chronic liver disease patients remains to be elucidated.

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.

Primaquine for radical cure of Plasmodium vivax and Plasmodium ovale malaria: an observational survey (2008-2010)

Since 2008, the French guidelines have promoted the systematic use of 30 mg/day of primaquine for the radical cure of Plasmodium vivax and Plamodium ovale infections. We observed three relapses in 10 patients with P vivax acquired in French Guiana. No relapses were seen in West African P ovale patients.

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

Background

Plasmodium ovale is responsible for 5% of imported malaria in French travellers. The clinical and biological features of six clustered cases of P. ovale malaria in an army unit of 62 French soldiers returning from the Ivory Coast are reported.

Case report

All patients were symptomatic and developed symptoms on average 50 days after their return and 20 days after the end of chemoprophylaxis (doxycycline). Clinical features included fever (6/6), mostly tertian (4/6), aches (6/6), nausea (3/6), abdominal pain (2/6), diarrhoea (2/6), or cough (2/6). Thrombocytopaenia was lower than 100,000/mm³ in half the cases only, and the haemoglobin count was normal for all patients. The diagnosis was made after at least three thick and thin blood smear searches. Parasitaemia was always lower than 0.5%. All rapid diagnostic tests were negative for HRP2 and pLDH antigens.

Discussion

Plasmodium ovale malaria is currently a problem to diagnose in travellers, notably in French soldiers returning from the Ivory Coast. Early attempts at diagnosis are difficult due to the lack of specific clinical features, the rarity of biological changes and the poor sensitivity of diagnostic tools to detect low parasitaemia. Thus, the diagnosis is commonly delayed or missed. Physicians should be aware of this diagnostic challenge to avoid relapses and provide prompt and adequate treatment with chloroquine and radical cure with primaquine.