Estimating the Prevalence of Asymptomatic Malaria Parasite Carriage in Southern Ghana: Utility of Molecular and Serological Diagnostic Tools

Abstract Background. Asymptomatic malaria infections can serve as potential reservoirs for malaria transmission. These infections range from microscopic to submicroscopic densities, making an accurate estimation of asymptomatic parasite carriage highly dependent on the sensitivity of the tool used for the diagnosis. This study sought to evaluate the sensitivities of a variety of molecular and serological diagnostic tool at determining the prevalence of asymptomatic Plasmodium falciparum parasite infections in two communities of varying malaria parasite prevalence.Methods. Whole blood from 194 afebrile participants aged between 6- and 70-years old living in a high (Obom) and a low (Asutsuare) malaria transmission setting of Ghana was used in this study. Thick and thin blood smears, an HRP2-based malaria rapid diagnostic test (RDT) and filter paper dried blood spots (DBS) were prepared from each blood sample. Genomic DNA was extracted from the remaining blood and used in Plasmodium specific photo-induced electron transfer polymerase chain reaction (PET-PCR) and Nested PCR, whilst the HRP2 antigen content of the DBS was estimated using a bead immunoassay. Comparison of prevalence as determined by each method was performed.Results. Parasite prevalence in the high transmission site of Obom was estimated at 71.4%, 61.9%, 60%, 37.8% and 19.1% by Nested PCR, the HRP2 bead assay, PET-PCR, HRP2-RDT and microscopy respectively. Parasite prevalence in the low transmission site of Asutsuare was estimated at 50.1%, 11.2%, 5.6%, 0% and 2.2% by Nested PCR, the HRP2 bead assay, PET-PCR, RDT and microscopy respectively.Conclusions: Nested PCR exhibited the highest sensitivity by identifying the highest prevalence of asymptomatic P. falciparum in both the high and low parasite prevalence setting. However, parasite prevalence estimated by the HRP2 bead assay and PET-PCR had the highest level of inter-rater agreement relative to all the other tools tested and have the advantage of requiring fewer processing steps and producing quantitative results relative Nested PCR. These advantages make PET-PCR and the HRP2 bead assay very useful tools for estimating malaria parasite prevalence in community surveys in these settings.

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Dynamics of the Composition of Plasmodium Species Contained within Asymptomatic Malaria Infections in the Central Region of Ghana

Journal of Tropical Medicine ◽

10.1155/2021/7419548 ◽

2021 ◽

Vol 2021 ◽

pp. 1-7

Author(s):

Dorcas Bredu ◽

Dickson Donu ◽

Linda Eva Amoah

Keyword(s):

Plasmodium Species ◽

Parasite Prevalence ◽

Dried Blood Spots ◽

Molecular Diagnostic ◽

Diagnostic Tools ◽

Rrna Gene ◽

Asymptomatic Malaria ◽

Chi Square ◽

Cross Sectional ◽

Human Plasmodium

Background. Monitoring changes in the composition of the Plasmodium species circulating within the population over a period can inform appropriate treatment recommendations. This study monitored variations in the prevalence of four common human Plasmodium species carried by children with asymptomatic malaria infections over a two-year period. Methods. Two cross-sectional studies were conducted in November 2017 and December 2019. A total of 210 children aged between 4 and 13 years were recruited in 2017, and 164 similarly aged children were recruited in 2019. Approximately 150 μl of finger-pricked blood was used to prepare thick and thin blood smears as well as spot Whatman® #3 filter paper. Genomic DNA was extracted from the dried blood spots and used in PCR to amplify the 18S rRNA gene from four different human Plasmodium parasites. Results. Parasite prevalence by microscopy and the prevalence of P. falciparum detected by PCR was relatively similar at the two time points (Pearson chi-square = 0.405, p = 0.525 , and Pearson chi-square = 0.452, p = 0.501 , respectively). However, the prevalence of PCR detectable P. malariae increased by 8.5-fold, whilst P. ovale increased from 0 to 9% in the children sampled in 2019 relative to the children sampled in 2017. The only parasite species identified by microscopy in this study was P. falciparum, and no P. vivax was identified by either microscopy or PCR in the study population during the study period. Conclusion. There is the need to implement molecular diagnostic tools for malaria parasite surveillance in Ghana. This will enable the identification and treatment of all circulating malaria parasites including P. malariae and P. ovale, whose population is expanding in parts of Ghana including Simiw.

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Large Variations in Malaria Parasite Carriage by Afebrile School Children Living in Nearby Communities in the Central Region of Ghana

Journal of Tropical Medicine ◽

10.1155/2020/4125109 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Evans K. Obboh ◽

Ruth E. Okonu ◽

Linda E. Amoah

Keyword(s):

Malaria Transmission ◽

Central Region ◽

Malaria Control ◽

Filter Paper ◽

Malaria Parasite ◽

Molecular Evidence ◽

Asymptomatic Malaria ◽

Cape Coast ◽

Malaria Parasites ◽

Asymptomatic Infections

Background. Indicators of successful malaria control interventions include a reduction in the prevalence and densities of malaria parasites contained in both symptomatic and asymptomatic infections as well as a reduction in malaria transmission. Individuals harboring malaria parasites in asymptomatic infections serve as reservoirs for malaria transmission. This study determined the prevalence of asymptomatic malaria parasite carriage in afebrile children attending six different schools in two districts, the Cape Coast Metropolitan Assembly (CCMA) and the Komenda Edina Eguafo Abirem (KEEA) of the Central Region of Ghana. Methods. This cross sectional study recruited afebrile children aged between 3 and 15 years old from six randomly selected schools in the Central Region of Ghana. Finger-pricked blood was collected and used to prepare thick and thin blood smears as well as spot a strip of filter paper (Whatman #3). Nested PCR was used to identify Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale, and Plasmodium vivax in DNA extracted from the filter paper spots. The multiplicity of P. falciparum infection was determined using merozoite surface protein 2 genotyping. Results. Out of the 528 children sampled, PCR identified 27.1% to harbor Plasmodium parasites in asymptomatic infections, whilst microscopy identified malaria parasites in 10.6% of the children. The overall PCR estimated prevalence of P. falciparum and P. malariae was 26.6% and 1.3%, respectively, with no P. ovale or P. vivax identified by PCR or microscopy. The RDT positivity rate ranged from 55.8% in Simiw to 4.5% in Kuful. Children from the Simiw Basic School accounted for 87.5% of all the asymptomatic infections. The multiplicity of P. falciparum infection was predominantly monoclonal and biclonal. Conclusions. The low prevalence of asymptomatic malaria parasite carriage by the children living in the Cape Coast Metropolis suggests that the malaria control interventions in place in CCMA are highly effective and that additional malaria control interventions are required for the KEEA district to reduce the prevalence of asymptomatic malaria parasite carriers. No molecular evidence of P. ovale and P. vivax was identified in the afebrile children sampled from the selected schools.

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The Impact of 3 Years of Targeted Indoor Residual Spraying With Pirimiphos-Methyl on Malaria Parasite Prevalence in a High-Transmission Area of Northern Zambia

American Journal of Epidemiology ◽

10.1093/aje/kwz107 ◽

2019 ◽

Vol 188 (12) ◽

pp. 2120-2130 ◽

Cited By ~ 3

Author(s):

Marisa A Hast ◽

Mike Chaponda ◽

Mbanga Muleba ◽

Jean-Bertin Kabuya ◽

James Lupiya ◽

...

Keyword(s):

Malaria Transmission ◽

Malaria Control ◽

Malaria Parasite ◽

Control Measure ◽

Indoor Residual Spraying ◽

Parasite Prevalence ◽

Organophosphate Insecticide ◽

Malaria Burden ◽

Pirimiphos Methyl ◽

The Impact

Abstract Malaria transmission in northern Zambia has increased in the past decade, despite malaria control activities. Evidence-based intervention strategies are needed to effectively reduce malaria transmission. Zambia’s National Malaria Control Centre conducted targeted indoor residual spraying (IRS) in Nchelenge District, Luapula Province, from 2014 to 2016 using the organophosphate insecticide pirimiphos-methyl. An evaluation of the IRS campaign was conducted by the Southern Africa International Centers of Excellence for Malaria Research using actively detected malaria cases in bimonthly household surveys carried out from April 2012 to July 2017. Changes in malaria parasite prevalence after IRS were assessed by season using Poisson regression models with robust standard errors, controlling for clustering of participants in households and demographic, geographical, and climatological covariates. In targeted areas, parasite prevalence declined approximately 25% during the rainy season following IRS with pirimiphos-methyl but did not decline during the dry season or in the overall study area. Within targeted areas, parasite prevalence declined in unsprayed households, suggesting both direct and indirect effects of IRS. The moderate decrease in parasite prevalence within sprayed areas indicates that IRS with pirimiphos-methyl is an effective malaria control measure, but a more comprehensive package of interventions is needed to effectively reduce the malaria burden in this setting.

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Prevalence of asymptomatic malaria infections in selected military camps in Tanzania

Tanzania Journal of Health Research ◽

10.4314/thrb.v21i1.4 ◽

2020 ◽

Vol 21 (1) ◽

pp. 1-11

Author(s):

Akili Kalinga ◽

Reginald A. Kavishe ◽

Deus S Ishengoma ◽

Gibson Kagaruki ◽

Clement Mweya ◽

...

Keyword(s):

Malaria Parasite ◽

Geometric Mean ◽

Parasite Prevalence ◽

Cross Sectional Study ◽

Asymptomatic Malaria ◽

Malaria Surveillance ◽

Cross Sectional ◽

Malaria Burden ◽

Military Recruits ◽

Significant Difference

Background: Despite a decrease in malaria burden reported between 2000 and 2015, an increasing trend of malaria transmission has been recently reported in some endemic countries including Tanzania. Periodic monitoring to identify pocket areas for asymptomatic Plasmodium falciparum infection is vital for malaria elimination efforts. The objective of this study was to determine prevalence of asymptomatic malaria infections among military recruits in selected camps in Tanzania. Methods: A cross-sectional study was conducted in 2015 at four military camps (Bulombora, Mgambo, Ruvu, and Rwamkoma) of National Service located in regions with varying malaria endemicity in Tanzania. Finger prick blood samples collected from asymptomatic military recruits who had been at the camps for over two months were simultaneously tested using microscopy and malaria rapid diagnostic tests (mRDTs) to detect malaria parasite infections. Results: Malaria parasite prevalence among asymptomatic recruits was 20.3% and 19.4% by microscopy and mRDT respectively. There was moderate agreement (Kappa=0.724) between microscopy and mRDT test results. A significant difference (p<0.001) of malaria parasite prevalence among the four study camps was observed; ranging from 1.9% in Bulombora to 39.4% in Rwamkoma. The geometric mean parasite density was 11,053 asexual parasites/µl and most recruits (56.8%) had 200 to 1999 asexual parasites/µl. P. falciparum was the predominant (99.2%) malaria parasite species. Conclusion: Our study found high prevalence of asymptomatic malaria infections among military recruits in the selected camps, and this varied from one camp to another. The study has highlighted that public residence institutions such as military camps can be potential hotspots for malaria infection and therefore should not be skipped in routine national malaria surveillance system for monitoring trends of infections

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Community-based molecular and serological surveillance of subclinical malaria in Myanmar

BMC Medicine ◽

10.1186/s12916-021-01993-8 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Katherine O’Flaherty ◽

Win Han Oo ◽

Sophie G. Zaloumis ◽

Julia C. Cutts ◽

Kyaw Zayar Aung ◽

...

Keyword(s):

Malaria Transmission ◽

Quantitative Polymerase Chain Reaction ◽

Dried Blood Spots ◽

Molecular Testing ◽

Sample Collection ◽

Malaria Surveillance ◽

Surveillance Network ◽

Targeted Interventions ◽

Residual Malaria Transmission ◽

Serological Surveillance

Abstract Background In the Greater Mekong Subregion (GMS), current malaria surveillance strategies rely on a network of village health volunteers (VHVs) reporting the results of rapid diagnostic tests (RDTs), known to miss many asymptomatic infections. Integration of more sensitive diagnostic molecular and serological measures into the VHV network may improve surveillance of residual malaria transmission in hard-to-reach areas in the region and inform targeted interventions and elimination responses. However, data on residual malaria transmission that would be captured by these measures in the VHV-led testing and treatment surveillance network in the GMS is unknown. Methods A total of 114 VHVs were trained to collect dried blood spots from villagers undergoing routine RDTs as part of VHV-led active and passive case detection from April 2015 to June 2016. Samples were subjected to molecular testing (quantitative polymerase chain reaction [qPCR]) to determine Plasmodium falciparum and P. vivax infection and serological testing (against P. falciparum and P. vivax antigens) to determine exposure to P. falciparum and P. vivax. Results Over 15 months, 114 VHVs performed 32,194 RDTs and collected samples for molecular (n = 13,157) and serological (n = 14,128) testing. The prevalence of molecular-detectable P. falciparum and P. vivax infection was 3.2% compared to the 0.16% prevalence of Plasmodium spp. by RDT, highlighting the large burden of infections undetected by standard surveillance. Peaks in anti-P. falciparum, but not P. vivax, merozoite IgG seroprevalence coincided with seasonal P. falciparum transmission peaks, even in those with no molecularly detectable parasites. At the individual level, antibody seropositivity was associated with reduced odds of contemporaneous P. falciparum (OR for PfCSP 0.51 [95%CI 0.35, 0.76], p = 0.001, PfAMA1 0.70 [95%CI 0.52, 0.93], p = 0.01, and PfMSP2 0.81 [95%CI 0.61, 1.08], p = 0.15), but not P. vivax infection (OR PvAMA1 1.02 [95%CI 0.73, 1.43], p = 0.89) indicating a potential role of immunity in protection against molecular-detectable P. falciparum parasitaemia. Conclusions We demonstrated that integration and implementation of sample collection for molecular and serological surveillance into networks of VHV servicing hard-to-reach populations in the GMS is feasible, can capture significant levels of ongoing undetected seasonal malaria transmission and has the potential to supplement current routine RDT testing. Improving malaria surveillance by advancing the integration of molecular and serological techniques, through centralised testing approaches or novel point-of-contact tests, will advance progress, and tracking, towards malaria elimination goals in the GMS.

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G6PD deficiency among malaria-infected national groups at the western part of Myanmar with implications for primaquine use in malaria elimination

Tropical Medicine and Health ◽

10.1186/s41182-021-00339-7 ◽

2021 ◽

Vol 49 (1) ◽

Author(s):

Kay Thwe Han ◽

Zay Yar Han ◽

Kyin Hla Aye ◽

Khin Thet Wai ◽

Aung Thi ◽

...

Keyword(s):

Enzyme Activity ◽

Malaria Elimination ◽

G6pd Deficiency ◽

Control Program ◽

Cross Sectional Study ◽

Diagnostic Tools ◽

Asymptomatic Malaria ◽

Radical Cure ◽

Readiness Assessment ◽

Cross Sectional

Abstract Background Glucose 6-phosphate dehydrogenase deficiency (G6PDd) plays a central role in readiness assessment for malaria elimination in Myanmar by 2030 that includes primaquine (PQ) use. The risk of hemolysis in G6PDd individuals hampers the widespread use of primaquine safely in malaria-infected patients. In the pre-elimination era, it is important to screen initially for asymptomatic malaria in combination with G6PD deficiency by applying more sensitive diagnostic tools. Therefore, this study examined the proportion of G6PDd and the distribution of G6PD genotypes among malaria-infected national groups in Myanmar before initiation of malaria elimination strategies. Methods A cross-sectional study in one township each with high malaria burden from two states in the western part of Myanmar, was conducted during 2016-2018, and 320 participants (164 Rakhine and 156 Chin National groups) were recruited. We used RDT and ultrasensitive polymerase chain reaction (us PCR) method to confirm malaria infection, and a G6PD RDT(CareStart) to detect G6PDd and PCR/restriction fragment length polymorphism (RFLP) method to confirm the variant of G6PDd for genotyping. G6PD enzyme activity was measured by G6PD Biosensor (CareStart). Results Malaria positivity rates detected by RDT were lower than those detected by us PCR in the combined samples [13% (42/320) vs. 21% (67/320)] as well as in the Rakhine samples [17% (28/164) vs. 25% (41/164)] and in Chin samples [9% (14/156) vs. 17% (26/156)]. G6PD deficiency rates were approximately 10% in both the combined samples and specific national groups. For G6PD enzyme activity in the combined samples, G6PDd (defined as < 30% of adjusted male median) was 10% (31/320) and severe G6PDd (< 10% of AMM) was 3% (9/320). Among malaria-infected patients with positive by both RDT and usPCR, G6PDd was less than 20% in each national group. G6PD genotyping showed that the G6PD Mahidol (G487A) was the major variant. Conclusions The varying degree of G6PDd detected among malaria-infected national groups by advanced diagnostic tools, strongly support the recommend G6PD testing by the National Malaria Control Program and the subsequent safe treatment of P. vivax by primaquine for radical cure. Establishing a field monitoring system to achieve timely malaria elimination is mandatory to observe the safety of patients after PQ treatment.

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The epidemiology and detectability of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in low, moderate and high transmission settings in Ethiopia

Malaria Journal ◽

10.1186/s12936-021-03587-4 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Elifaged Hailemeskel ◽

Surafel K Tebeje ◽

Sinknesh W. Behaksra ◽

Girma Shumie ◽

Getasew Shitaye ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Plasmodium Vivax ◽

Age Groups ◽

Diagnostic Tools ◽

Asymptomatic Malaria ◽

Rapid Diagnostics ◽

Cross Sectional ◽

Low Transmission ◽

High Transmission ◽

Study Sites

Abstract Background As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, the epidemiology and detectability of asymptomatic Plasmodium falciparum and Plasmodium vivax infections were investigated in different transmission settings in Ethiopia. Method: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA-based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API > 0 and < 5), moderate (API ≥ 5 and < 100) and high transmission (API ≥ 100) and detectability of infections was assessed in these settings. Results In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95% CI] 1.6–7.2, P = 0.002) and high endemic settings (AOR = 5.1; 95% CI 2.6–9.9, P < 0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95% CI 0.9–1.0, P = 0.013) declined with age. Conclusions Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.

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Asymptomatic malaria and anaemia among pregnant women during high and low malaria transmission seasons in Burkina Faso: household-based cross-sectional surveys in Burkina Faso, 2013 and 2017

Malaria Journal ◽

10.1186/s12936-021-03703-4 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Toussaint Rouamba ◽

Sékou Samadoulougou ◽

Mady Ouédraogo ◽

Hervé Hien ◽

Halidou Tinto ◽

...

Keyword(s):

Burkina Faso ◽

Pregnant Women ◽

Malaria Transmission ◽

Asymptomatic Malaria ◽

Cross Sectional ◽

Transmission Season ◽

Low Transmission ◽

High Transmission ◽

Asymptomatic Carriage ◽

Low Malaria Transmission

Abstract Background Malaria in endemic countries is often asymptomatic during pregnancy, but it has substantial consequences for both the mother and her unborn baby. During pregnancy, anaemia is an important consequence of malaria infection. In Burkina Faso, the intensity of malaria varies according to the season, albeit the prevalence of malaria and anaemia as well as their risk factors, during high and low malaria transmission seasons is underexplored at the household level. Methods Data of 1751 pregnant women from October 2013 to March 2014 and 1931 pregnant women from April 2017 to June 2017 were drawn from two cross-sectional household surveys conducted in 24 health districts of Burkina Faso. Pregnant women were tested for malaria in their household after consenting. Asymptomatic carriage was defined as a positive result from malaria rapid diagnostic tests in the absence of clinical symptoms of malaria. Anaemia was defined as haemoglobin level less than 11 g/dL in the first and third trimester and less than 10.5 g/dL in the second trimester of pregnancy. Results Prevalence of asymptomatic malaria in pregnancy was estimated at 23.9% (95% CI 20.2–28.0) during the high transmission season (October–November) in 2013. During the low transmission season, it was 12.7% (95% CI 10.9–14.7) between December and March in 2013–2014 and halved (6.4%; 95% CI 5.3–7.6) between April and June 2017. Anaemia prevalence was estimated at 59.4% (95% CI 54.8–63.8) during the high transmission season in 2013. During the low transmission season, it was 50.6% (95% CI 47.7–53.4) between December and March 2013–2014 and 65.0% (95% CI 62.8–67.2) between April and June, 2017. Conclusion This study revealed that the prevalence of malaria asymptomatic carriage and anaemia among pregnant women at the community level remain high throughout the year. Thus, more efforts are needed to increase prevention measures such as IPTp–SP coverage in order to reduce anaemia and contribute to preventing low birth weight and poor pregnancy outcomes.

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Contribution of Asymptomatic Plasmodium Infections to the Transmission of Malaria in Kayin State, Myanmar

The Journal of Infectious Diseases ◽

10.1093/infdis/jiy686 ◽

2018 ◽

Vol 219 (9) ◽

pp. 1499-1509 ◽

Cited By ~ 14

Author(s):

Victor Chaumeau ◽

Ladda Kajeechiwa ◽

Bénédicte Fustec ◽

Jordi Landier ◽

Saw Naw Nyo ◽

...

Keyword(s):

Malaria Transmission ◽

Entomological Inoculation Rate ◽

Fold Increase ◽

Estimating Equation ◽

Malaria Prevalence ◽

Pcr Analysis ◽

Asymptomatic Malaria ◽

Asymptomatic Infections ◽

Greater Mekong Subregion ◽

The Impact

Abstract Background The objective of mass antimalarial drug administration (MDA) is to eliminate malaria rapidly by eliminating the asymptomatic malaria parasite reservoirs and interrupting transmission. In the Greater Mekong Subregion, where artemisinin-resistant Plasmodium falciparum is now widespread, MDA has been proposed as an elimination accelerator, but the contribution of asymptomatic infections to malaria transmission has been questioned. The impact of MDA on entomological indices has not been characterized previously. Methods MDA was conducted in 4 villages in Kayin State (Myanmar). Malaria mosquito vectors were captured 3 months before, during, and 3 months after MDA, and their Plasmodium infections were detected by polymerase chain reaction (PCR) analysis. The relationship between the entomological inoculation rate, the malaria prevalence in humans determined by ultrasensitive PCR, and MDA was characterized by generalized estimating equation regression. Results Asymptomatic P. falciparum and Plasmodium vivax infections were cleared by MDA. The P. vivax entomological inoculation rate was reduced by 12.5-fold (95% confidence interval [CI], 1.6–100-fold), but the reservoir of asymptomatic P. vivax infections was reconstituted within 3 months, presumably because of relapses. This was coincident with a 5.3-fold (95% CI, 4.8–6.0-fold) increase in the vector infection rate. Conclusion Asymptomatic infections are a major source of malaria transmission in Southeast Asia.

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Asymptomatic Malaria Infection and Their Antibodies Against Malaria: A Study in Abra de Ilog, Occidental Mindoro, Philippines

American Journal of Clinical Pathology ◽

10.1093/ajcp/aqz121.028 ◽

2019 ◽

Vol 152 (Supplement_1) ◽

pp. S116-S116

Author(s):

Carlo Ledesma ◽

Ma Gina Sadang

Keyword(s):

Real Time ◽

Malaria Infection ◽

Malaria Parasite ◽

National Commission ◽

Enzyme Linked Immunosorbent Assay ◽

Asymptomatic Malaria ◽

Blood Samples ◽

Blood Smears ◽

Specific Igg

Abstract Human malaria, caused by four species of Plasmodium, namely P falciparum, P vivax, P malariae, and P ovale, remains a health problem of global concern, with one to two million deaths annually and risking about two billion people worldwide. Alternative ways of controlling the incidence of malaria through understanding the host’s immune response to monoinfection and the detection of the presence of asymptomatic malaria infection are the factors being addressed in this study. The determination of the possible existence of cross-antigenic stimulation is a matter of great significance for future research and development. The isolation of these antigenic structures may give the first step to the development of better vaccines that may protect the general population who are at risk of developing malaria. Prior to blood collection, a memorandum of agreement was signed between the researcher and the Iraya-Mangyan leaders of Abra de Ilog, Occidental Mindoro. A Certificate Precondition was issued by the National Commission of Indigenous Peoples, which was required by the Graduate School Ethics Review Committee. Determination of the presence of malaria parasite on blood samples of residents of two barangays in Abra de Ilog, Occidental Mindoro, was performed using two methods: microscopic examination of stained blood smears for the presence of malaria parasite and polymerase chain reaction. Blood smears were prepared and eventually stained using Giemsa and Dip Quick stains. The detection of 5 positive cases of malaria infection with ring/schizont stage among the 53 cases was a clear indication of positive asymptomatic cases. Nested PCR using Plasmodium spp.–specific primer as well as P falciparum–specific and P vivax–specific primers showed the absence of bands so that one of the recommendations in this study is the performance of real-time PRC using more sensitive primers. Levels of P falciparum and P vivax–specific immunoglobulin were measured using an enzyme-linked immunosorbent assay revealing a higher level of PF-specific IgG than PV-specific IgG. Whole blood samples were saved for future determinations such as real-time PCR, immunophenotypic analysis, and possible parasitic culture. Further similar studies may also be done by increasing the number of respondents as well as the areas of concern for a more extensive scope.

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