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Fulltext Plasmodium ovale infection in Malaysia: first imported case

Lim YA, Mahmud R, Chew CH, T T, Chua KH

Malar J, 2010;9:272.
PMID: 20929588 DOI: 10.1186/1475-2875-9-272

BACKGROUND:
Plasmodium ovale infection is rarely reported in Malaysia. This is the first imported case of P. ovale infection in Malaysia which was initially misdiagnosed as Plasmodium vivax.

METHODS:
Peripheral blood sample was first examined by Giemsa-stained microscopy examination and further confirmed using a patented in-house multiplex PCR followed by sequencing.

RESULTS AND DISCUSSION:
Initial results from peripheral blood smear examination diagnosed P. vivax infection. However further analysis using a patented in-house multiplex PCR followed by sequencing confirmed the presence of P. ovale. Given that Anopheles maculatus and Anopheles dirus, vectors of P. ovale are found in Malaysia, this finding has significant implication on Malaysia's public health sector.

CONCLUSIONS:
The current finding should serve as an alert to epidemiologists, clinicians and laboratory technicians in the possibility of finding P. ovale in Malaysia. P. ovale should be considered in the differential diagnosis of imported malaria cases in Malaysia due to the exponential increase in the number of visitors from P. ovale endemic regions and the long latent period of P. ovale. It is also timely that conventional diagnosis of malaria via microscopy should be coupled with more advanced molecular tools for effective diagnosis.

Matched MeSH terms: Plasmodium ovale/genetics
Fulltext Prevalence of Asymptomatic and/or Low-Density Malaria Infection among High-Risk Groups in Peninsular Malaysia

Noordin NR, Lee PY, Mohd Bukhari FD, Fong MY, Abdul Hamid MH, Jelip J, et al.

Am J Trop Med Hyg, 2020 09;103(3):1107-1110.
PMID: 32618263 DOI: 10.4269/ajtmh.20-0268

Asymptomatic and/or low-density malaria infection has been acknowledged as an obstacle to achieving a malaria-free country. This study aimed to determine the prevalence of asymptomatic and/or low-density malaria infection in previously reported malarious localities using nested PCR in four states, namely, Johor, Pahang, Kelantan, and Selangor, between June 2019 and January 2020. Blood samples (n = 585) were collected and were extracted using a QIAamp blood kit. The DNA was concentrated and subjected to nested PCR. Thin and thick blood smears were examined as well. Of the 585 samples collected, 19 were positive: 10 for Plasmodium knowlesi, eight for Plasmodium vivax, and one for Plasmodium ovale. Asymptomatic and/or low-density malaria infection is a threat to malaria elimination initiatives. Eliminating countries should develop guidance policy on the importance of low-density malaria infection which includes detection and treatment policy.

Matched MeSH terms: Plasmodium ovale/genetics
Fulltext Two sympatric types of Plasmodium ovale and discrimination by molecular methods

Zaw MT, Lin Z

J Microbiol Immunol Infect, 2017 Oct;50(5):559-564.
PMID: 28065415 DOI: 10.1016/j.jmii.2016.08.004

Plasmodium ovale is widely distributed in tropical countries, whereas it has not been reported in the Americas. It is not a problem globally because it is rarely detected by microscopy owing to low parasite density, which is a feature of clinical ovale malaria. P.o. curtisi and P.o. wallikeri are widespread in both Africa and Asia, and were known to be sympatric in many African countries and in southeast Asian countries. Small subunit ribosomal RNA (SSUrRNA) gene, cytochrome b (cytb) gene, and merozoite surface protein-1 (msp-1) gene were initially studied for molecular discrimination of P.o. curtisi and P.o. wallikeri using polymerase chain reaction (PCR) and DNA sequencing. DNA sequences of other genes from P. ovale in Southeast Asia and the southwestern Pacific regions were also targeted to differentiate the two sympatric types. In terms of clinical manifestations, P.o. wallikeri tended to produce higher parasitemia levels and more severe symptoms. To date, there have been a few studies that used the quantitative PCR method for discrimination of the two distinct P. ovale types. Conventional PCR with consequent DNA sequencing is the common method used to differentiate these two types. It is necessary to identify these two types because relapse periodicity, drug susceptibility, and mosquito species preference need to be studied to reduce ovale malaria. In this article, an easier method of molecular-level discrimination of P.o. curtisi and P.o. wallikeri is proposed.

Matched MeSH terms: Plasmodium ovale/genetics*
Fulltext A panel of recombinant proteins from human-infective Plasmodium species for serological surveillance

Müller-Sienerth N, Shilts J, Kadir KA, Yman V, Homann MV, Asghar M, et al.

Malar J, 2020 Jan 17;19(1):31.
PMID: 31952523 DOI: 10.1186/s12936-020-3111-5

BACKGROUND: Malaria remains a global health problem and accurate surveillance of Plasmodium parasites that are responsible for this disease is required to guide the most effective distribution of control measures. Serological surveillance will be particularly important in areas of low or periodic transmission because patient antibody responses can provide a measure of historical exposure. While methods for detecting host antibody responses to Plasmodium falciparum and Plasmodium vivax are well established, development of serological assays for Plasmodium knowlesi, Plasmodium ovale and Plasmodium malariae have been inhibited by a lack of immunodiagnostic candidates due to the limited availability of genomic information.
METHODS: Using the recently completed genome sequences from P. malariae, P. ovale and P. knowlesi, a set of 33 candidate cell surface and secreted blood-stage antigens was selected and expressed in a recombinant form using a mammalian expression system. These proteins were added to an existing panel of antigens from P. falciparum and P. vivax and the immunoreactivity of IgG, IgM and IgA immunoglobulins from individuals diagnosed with infections to each of the five different Plasmodium species was evaluated by ELISA. Logistic regression modelling was used to quantify the ability of the responses to determine prior exposure to the different Plasmodium species.
RESULTS: Using sera from European travellers with diagnosed Plasmodium infections, antigens showing species-specific immunoreactivity were identified to select a panel of 22 proteins from five Plasmodium species for serological profiling. The immunoreactivity to the antigens in the panel of sera taken from travellers and individuals living in malaria-endemic regions with diagnosed infections showed moderate power to predict infections by each species, including P. ovale, P. malariae and P. knowlesi. Using a larger set of patient samples and logistic regression modelling it was shown that exposure to P. knowlesi could be accurately detected (AUC = 91%) using an antigen panel consisting of the P. knowlesi orthologues of MSP10, P12 and P38.
CONCLUSIONS: Using the recent availability of genome sequences to all human-infective Plasmodium spp. parasites and a method of expressing Plasmodium proteins in a secreted functional form, an antigen panel has been compiled that will be useful to determine exposure to these parasites.

Matched MeSH terms: Plasmodium ovale/genetics