Identification of Reticulocyte Binding Domain of Plasmodium ovale curtisi Duffy Binding Protein (PocDBP) Involved in Reticulocyte Invasion

The Plasmodium ovale curtisi (Poc) prevalence has increased substantially in sub-Saharan African countries as well as regions of Southeast Asia. Poc parasite biology has not been explored much to date; in particular, the invasion mechanism of this malaria parasite remains unclear. In this study, the binding domain of the Duffy binding protein of P. ovale curtisi (PocDBP) was characterized as an important ligand for reticulocyte invasion. The homologous region of the P. vivax Duffy binding protein in PocDBP, named PocDBP-RII herein, was selected, and the recombinant PocDBP-RII protein was expressed in an Escherichia coli system. This was used to analyze reticulocyte binding activity using fluorescence-activated cell sorting and immune serum production in rabbits. The binding specificity was proven by treating reticulocytes with trypsin, chymotrypsin and neuraminidase. The amino acid sequence homology in the N-terminal Cys-rich region was found to be ~ 44% between PvDBP and PocDBP. The reticulocyte binding activity of PocDBP-RII was significantly higher than the erythrocyte binding activity and was concentration dependent. Erythrocyte binding was reduced significantly by chymotrypsin treatment and inhibited by an anti-PocDBP-RII antibody. This finding suggests that PocDBP may be an important ligand in the reticulocyte invasion process of P. ovale curtisi.

Epidemiological, Physiological and Diagnostic Comparison of Plasmodium ovale curtisi and Plasmodium ovale wallikeri

Nowadays, Plasmodium ovale is divided into two non-recombinant sympatric species: Plasmodium ovale wallikeri and Plasmodium ovale curtisi. In this mini review, we summarize the available knowledge on the clinical/biological aspects of P. ovale spp. malaria and current techniques for the diagnosis/characterisation of P. ovale curtisi and P. ovale wallikeri. P. ovale wallikeri infections are characterized by a deeper thrombocytopenia and shorter latency compared to P. ovale curtisi infections, indicating that P. ovale wallikeri is more pathogenic than P. ovale curtisi. Rapid diagnosis for effective management is difficult for P. ovale spp., since specific rapid diagnostic tests are not available and microscopic diagnosis, which is recognized as the gold standard, requires expert microscopists to differentiate P. ovale spp. from other Plasmodium species. Neglect in addressing these issues in the prevalence of P. ovale spp. represents the existing gap in the fight against malaria.

Hacia un mundo libre de malaria: Utopía o realidad

La Malaria es una enfermedad causada por un parásito que se transmite a los humanos a través de la picadura de mosquito hembra Anophele. Reportando la WHO en el 2019, 229 millones de casos y 409.000 muertes por la enfermedad en 87 paises del mundo, Existen seis especies de este párasito: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale wallickeri, Plasmodium ovale curtisi, Plasmodium malariae y Plasmodium knowlesi. Siendo la especie P. falciparum la causante de mayor morbilidad, con tasa entre 10 y 50% de mortalidad por malaria complicada. Alrededor de 108 países han declarado la malaria como enfermedad endémica, pudiendo padecer la enfermedad en cualquier época del año. Sin embargo, en el caso de América Latina hoy en día se vive un estancamiento de la enfermedad, reportándose en países menos de 100 casos autóctonos entre el 2000 y 2019, con algunas excepciones. Esta situación de vulnerabilidad de países como Brasil, Colombia, la frontera Perú-Ecuador, Venezuela, se incrementan ante la presencia activa de la pandemia producto del Covid -19 aunado a restricciones económicas, incremento de la actividad minera, o políticas públicas que ponen en riesgo la sostenibilidad del programa de control de la enfermedad. Para el 2021 la OMS corrobora que existen 87 países con malaria a nivel mundial, de los cuales 24 de ellos habían interrumpido su transmisión autóctona por 3 años. Realidad que consolidad la propuesta tras la experiencia adquirida, que cualquiera que sea la situación epidemiológica de entrada, el trabajo hacia la erradicación de la malaria debe entenderse y atenderse como un proceso continuo donde los propios Estados deben desde su realidad y estrategias propias se articulen con el Plan Estratégico Técnico Mundial Contra la Malaria 2016-2030 propuesto por la OMS. Palabras

High prevalence of asymptomatic malaria infections in adults, Ashanti Region, Ghana, 2018

Background Ghana is among the high-burden countries for malaria infection and recently reported a notably increase in malaria cases. While asymptomatic parasitemia is increasingly recognized as a hurdle for malaria elimination, studies on asymptomatic malaria are scarce and usually focus on children and on non-falciparum species. The present study aims to assess the prevalence of asymptomatic Plasmodium falciparum and non-falciparum infections in Ghanaian adults in the Ashanti region during the high transmission season. Methods Asymptomatic adult residents from five villages in the Ashanti Region, Ghana, were screened for Plasmodium spp. by rapid diagnostic test (RDT) and polymerase chain reaction (PCR) during the rainy season. Samples tested positive were subtyped using species-specific real-time PCR. For all P. ovale infections additional sub-species identification was performed.Results Molecular prevalence of asymptomatic Plasmodium infection was 284/391 (73%); only 126 (32%) infections were detected by RDT. While 266 (68%) participants were infected with Plasmodium falciparum, 33 (8%) were infected with Plasmodium malariae and 34 (9%) with Plasmodium ovale. The sub-species Plasmodium ovale curtisi and P. ovale wallikeri were identified to similar proportions. Non-falciparum infections usually presented as mixed infections with Plasmodium falciparum.Conclusions Most adult residents in the Ghanaian forest zone are asymptomatic Plasmodium carriers. The high Plasmodium prevalence not detected by RDT in adults highlights that malaria eradication efforts must target all members of the population. Beneath Plasmodium falciparum, screening and treatment must also include infections with Plasmodium malariae, P. ovale curtisi and P. ovale wallikeri .

Diagnosis and Molecular Analysis on Imported Plasmodium ovale curtisi and P. ovale wallikeri Malaria Cases from West and South Africa during 2013-2016

Majority of the imported malaria cases in Korea is attributed to <i>Plasmodium falciparum</i> and <i>P. vivax</i> infections, whereas <i>P. malariae</i> and <i>P. ovale</i> infections are very rare. Falciparum and ovale malaria are mostly imported from Africa, while most of the vivax malaria cases are imported from Southeast Asia. Here, we report 6 Korean imported ovale malaria cases (4 males and 2 females) who had visited in Africa during 2013-2016. These subjects were diagnosed with <i>P. ovale</i> based on microscopic findings, <i>Plasmodium</i> species-specific nested-PCR, and phylogenetic clade using 18S rRNA gene sequences. We identified 2 <i>P. ovale</i> subtypes, 1 <i>P. ovale curtisi</i> (classic type) and 5 <i>P. ovale wallikeri</i> (variant type). All patients were treated with chloroquine and primaquine, and no relapse or recrudescence was reported for 1 year after treatment. With increase of travelers to the countries where existing Plasmodium species, the risk of <i>Plasmodium</i> infection is also increasing. Molecular monitoring for imported malaria parasites should be rigorously and continuously performed to enable diagnosis and certification of <i>Plasmodium</i> spp.