Population-level estimates of the proportion of Plasmodium vivax blood-stage infections attributable to relapses among febrile patients attending Adama Malaria Diagnostic Centre, East Shoa Zone, Oromia, Ethiopia

Seasonal Dynamics of Symptomatic and Asymptomatic Plasmodium falciparum and Plasmodium vivax Infections in Coendemic Low-Transmission Settings, South Ethiopia

Ethiopia has a plan to eliminate malaria in selected low-transmission districts by 2025. However, complex factors such as seasonality, focal heterogeneity, and coendemicity of Plasmodium vivax and Plasmodium falciparum, and asymptomatic cases, along with other factors, pose challenges. This longitudinal study assessed these dynamics and associated factors in three elimination-targeted settings in southern Ethiopia. The study included rural districts (Wonago and Yirgacheffe) and an urban setting (Dilla town) with 504 participants from 168 households per season. The study covered the peak and minor malaria transmission seasons and the dry season. Finger-prick blood was collected for microscopy, rapid diagnostic tests, and 18S-rRNA-based quantitative polymerase chain reaction (qPCR). During the dry season, P. vivax accounted for most infections (64.5%, 71/110) and symptomatic malaria (50.9%, 29/57), whereas P. falciparum dominated during the peak transmission season (45.7%, 42/92 infections and 58.1%, 25/43 of symptomatic cases). Treatment-seeking behavior was low, with 65.3% (143/219) of symptomatic individuals not seeking treatment. Dilla town had significantly higher infection prevalence (29.6%, 149/504, P <0.001) in all seasons compared with the rural sites. The incidence rate was 12/1,000 person-seasons by qPCR and 5/1,000 person-seasons by microscopy. Urban residents, those with low hemoglobin levels, nonuse of mosquito nets, and proximity to stagnant water had a significantly higher risk of infection (P <0.001). Tailored approaches are needed in elimination-targeted areas, focusing on urban settings, Plasmodium species, and strengthening community-level interventions for behavioral change and active case detection.

Analysis of the relapse of imported Plasmodium vivax and Plasmodium ovale in five provinces of China

BACKGROUND

The global battle against malaria is facing formidable challenges, particularly in controlling Plasmodium vivax and Plasmodium ovale, whose cases have not been reduced as effectively as Plasmodium falciparum because of their relapse. This study investigates the current situation and underlying factors contributing to relapse or recrudescence of imported cases of P. vivax and P. ovale, and seeks to provide a reference for reducing relapse or recrudescence in malaria-free areas and offers a scientific basis for designing strategies to prevent imported re-transmission.

METHODS

This study analysed imported P. vivax and P. ovale in Anhui, Zhejiang, Henan, Hubei, and Guangxi provinces during 2014-2021 by retrospective analysis. A case-control study was conducted on patients who experienced relapse or recrudescence.

RESULTS

From 2014 to 2021, 306 cases of P.vivax and 896 cases of P.ovale were included in the study, while 75 cases had relapse or recrudescence, including 49 cases of P. ovale (65.33%) and 26 cases of P. vivax (34.67%). Within less than 5 weeks after returning to the country, 122 cases of P. vivax (39.87%, 122/306) and 265 cases of P. ovale (29.58%, 265/896) occurred. Within less than 53 weeks, the ratio of P. vivax was 94.77% (290/306), and that of P. ovale was 89.96% (806/896). Among the cases experiencing relapse or recrudescence, only 1 case of P. vivax (1/26 3.85%) and 3 cases of P. ovale (3/49 6.12%) occurred within less than 5 weeks after the first onset, whereas 21 cases of P. vivax (21/26 80.77%) and 42 cases of P. ovale (42/49 85.71%) occurred within less than 53 weeks after the first onset. The difference in relapse or recrudescence due to different drugs and medication regimens and medical activities at various levels of medical institutions was statistically significant.

CONCLUSION

In areas where malaria has been eliminated, routine health screening in a scientific time frame for people returning from at-risk areas can effectively improve the efficiency of preventing re-transmission, thereby reducing prevention costs and disease burden. Preventing patients from self-treating and strengthening medication regulations in health facilities are key measures to reduce relapse or recrudescence.

Ethiopian Plasmodium vivax hypnozoites formation dynamics and their susceptibility to reference antimalarial drugs

One of the key obstacles to malaria elimination is largely attributed to Plasmodium vivax's ability to form resilient hypnozoites in the host liver that cause relapsing infections. As a result, interruption of P. vivax transmission is difficult. P. vivax transmission occurs in Duffy-positive individuals and have been mainly thought to be absent in Africa. However, increasing studies using molecular tools detected P. vivax among Duffy-negative individuals in various African countries. Studies on the African P. vivax has been severely limited because most of malaria control program focus mainly on falciparum malaria. In addition, there is a scarcity of laboratory infrastructures to overcome the biological obstacles posed by P. vivax. Herein, we established field transmission of Ethiopian P. vivax for routine sporozoite supply followed by liver stage infection in Mali. Furthermore, we evaluated local P. vivax hypnozoites and schizonts susceptibilities to reference antimalarial drugs. The study enabled the assessment of local African P. vivax hypnozoite production dynamics. Our data displayed the ability of the African P. vivax to produce hypnozoite forms ex-vivo at different rates per field isolate. We report that while tafenoquine (1µM) potently inhibited both hypnozoites and schizont forms; atovaquone (0.25µM) and the phosphatidylinositol-4-OH kinase (PI4K)-specific inhibitor KDU691 (0.5µM) showed no activity against hypnozoites forms. Unlike hypnozoites forms, P. vivax schizont stages were fully susceptible to both atovaquone (0.25µM) and the (PI4K)-specific inhibitor KDU691 (0.5µM). Together, the data revealed the importance of the local platform for further biological investigation and implementation of drug discovery program on the African P. vivax clinical isolates.

Differential transmissibility to Anopheles arabiensis of Plasmodium vivax gametocytes in patients with diverse Duffy blood group genotypes

BACKGROUND

Measuring risk of malaria transmission is complex, especially in case of Plasmodium vivax. This may be overcome using membrane feeding assays in the field where P. vivax is endemic. However, mosquito-feeding assays are affected by a number of human, parasite and mosquito factors. Here, this study identified the contributions of Duffy blood group status of P. vivax-infected patients as a risk of parasite transmission to mosquitoes.

METHODS

A membrane feeding assay was conducted on a total of 44 conveniently recruited P. vivax infected patients in Adama city and its surroundings in East Shewa Zone, Oromia region, Ethiopia from October, 2019 to January, 2021. The assay was performed in Adama City administration. Mosquito infection rates were determined by midgut dissections at seven to 8 days post-infection. Duffy genotyping was defined for each of the 44 P. vivax infected patients.

RESULTS

The infection rate of Anopheles mosquitoes was 32.6% (296/907) with 77.3% proportion of infectious participants (34/44). Infectiousness of participants to Anopheles mosquitoes appeared to be higher among individuals with homozygous Duffy positive blood group (TCT/TCT) than heterozygous (TCT/CCT), but the difference was not statistically significant. The mean oocyst density was significantly higher among mosquitoes fed on blood of participants with FY*B/FY*BES than other genotypes (P = 0.001).

CONCLUSION

Duffy antigen polymorphisms appears to contribute to transmissibility difference of P. vivax gametocytes to Anopheles mosquitoes, but further studies are required.

Naturally acquired antibodies to gametocyte antigens are associated with reduced transmission of Plasmodium vivax gametocytes to Anopheles arabiensis mosquitoes

Naturally acquired antibodies may reduce the transmission of Plasmodium gametocytes to mosquitoes. Here, we investigated associations between antibody prevalence and P. vivax infectivity to mosquitoes. A total of 368 microscopy confirmed P. vivax symptomatic patients were passively recruited from health centers in Ethiopia and supplemented with 56 observations from asymptomatic P. vivax parasite carriers. Direct membrane feeding assays (DMFA) were performed to assess mosquito infectivity; for selected feeds these experiments were also performed after replacing autologous plasma with malaria naïve control serum (n=61). The prevalence of antibodies against 6 sexual stage antigens (Pvs47, Pvs48/45, Pvs230, PvsHAP2, Pvs25 and PvCelTOS) and an array of asexual antigens was determined by ELISA and multiplexed bead-based assays. Gametocyte (ρ< 0.42; p = 0.0001) and parasite (ρ = 0.21; p = 0.0001) densities were positively associated with mosquito infection rates. Antibodies against Pvs47, Pvs230 and Pvs25 were associated with 23 and 34% reductions in mosquito infection rates (p<0.0001), respectively. Individuals who showed evidence of transmission blockade in serum-replacement DMFAs (n=8) were significantly more likely to have PvsHAP2 or Pvs47 antibodies. Further studies may demonstrate causality for the observed associations, improve our understanding of the natural transmission of P. vivax and support vaccine development.

Plasmodium vivax in Children: Hidden Burden and Conspicuous Challenges, a Narrative Review

There has been progress towards decreasing malaria prevalence globally; however, Plasmodium vivax has been less responsive to elimination efforts compared with Plasmodium falciparum. P. vivax malaria remains a serious public health concern in regions where it is the dominant species (South and South-East Asia, the Eastern Mediterranean region, and South America) and is increasingly recognized for its contribution to overall morbidity and mortality worldwide. The incidence of P. vivax decreases with increasing age owing to rapidly acquired clinical immunity and there is a disproportionate burden of P. vivax in infants and children, who remain highly vulnerable to severe disease, recurrence, and anemia with associated developmental impacts. Diagnosis is sometimes difficult owing to the sensitivity of diagnostic tests to detect low levels of parasitemia. Additionally, the propensity of P. vivax to relapse following reactivation of dormant hypnozoites in the liver contributes to disease recurrence in infants and children, and potentiates morbidity and transmission. The 8-aminoquinolines, primaquine and tafenoquine, provide radical cure (relapse prevention). However, the risk of hemolysis in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency necessitates testing prior to administration of 8-aminoquinolines, which has limited their uptake. Additional challenges include lack of availability of pediatric dose formulations and problems with adherence to primaquine owing to the length of treatment recommended. A paucity of data and studies specific to pediatric P. vivax malaria impacts the ability to deliver targeted interventions. It is imperative that P. vivax in infants and children be the focus of future research, control initiatives, and anti-malarial drug development.

Assessment of malaria prevalence in Boset District, East Shawa Zone, Oromia Regional State, Ethiopia: a retrospective study

Objective

In this study, we aimed to assess the epidemiological profile and associated risk factors of malaria in Boset District using clinical records from the Boset District Health Office Central Surveillance Unit, East Shawa Zone, Oromia, Ethiopia.

Methods

This health facility-based retrospective cross-sectional study included clinical malaria data for 5 years (2016–2020) recorded at all public and private health facilities in the district.

Results

The present study revealed an overall malaria slide positivity rate of 12.4% (21,059/169,986), ranging from 23.3% to 5.3% during 2016–2020 in Boset District. Malaria cases were recorded in all age groups, but individuals aged 15 years and above accounted for a higher (56.2%) average proportion of malaria cases. Concerning the relative proportion of malaria parasite species, Plasmodium falciparum was slightly predominant (58%) over P. vivax (42%).

Conclusion

The present study revealed a declining trend in malaria cases over the 5-year study period in Boset District. Scaling up the available malaria prevention strategies and control measures is recommended to achieve malaria pre-elimination.

Assessing the diagnostic performance of a novel RT-PCR fluorescence method for the detection of human plasmodium species

Background

Malaria elimination effort is hampered not only by the lack of effective medication but also due to the lack of sensitive diagnostic tools to detect infections with low levels of parasitemia. Therefore, more sensitive and specific high-throughput molecular diagnostic approaches are needed for accurate malaria diagnosis.

Methods

In the present study, the performance of a novel single-tube MC004 real-time polymerase chain reaction (PCR) assay (MRC-Holland, Amsterdam, the Netherlands) was assessed for the detection of infection and discrimination of Plasmodium species. Blood samples (n = 150) were collected from malaria suspected patients at Adama malaria diagnosis and treatment centre, Adama, central Ethiopia. The positive predictive value (PPV), negative predictive value (NPV), analytical sensitivity and specificity of the assay were assessed against the conventional microscopic method.

Results

Plasmodium species were detected in 59 (39.3%) of the samples by microscopy and in 62 (41.3%) by the novel MC004 RT-PCR. Plasmodium vivax, Plasmodium falciparum and mixed infections with Plasmodium falciparum & Plasmodium vivax accounted for 47.5%, 40.6% and 11.9% respectively as detected by microscopy. The MC004 RT-PCR assay identified 59.7% and 40.3% of the samples positive for Plasmodium vivax and Plasmodium falciparum respectively. The sensitivity, specificity, PPV, and NPV of the MC004 RT-PCR assay were 95.8%, 97.8%, 92%, and 98.9%, respectively. No mixed infections were detected using the MC004 assay.

Conclusion

The MC004 RT-PCR assay is a useful tool for the early detection of malaria and identification of Plasmodium species with a high degree of sensitivity and specificity. Due to its high sensitivity, and simplicity (being a single-tube assay), the MC004 is suitable for use in clinical settings and epidemiological studies.

Vivax malaria in Duffy-negative patients shows invariably low asexual parasitaemia: implication towards malaria control in Ethiopia

BACKGROUND

The increase in detections of Plasmodium vivax infection in Duffy-negative individuals in Africa has challenged the dogma establishing the unique P. vivax Duffy Binding Protein-Duffy antigen receptor for chemokines (PvDBP-DARC) pathway used by P. vivax merozoites to invade reticulocytes. Information on the impact of Duffy antigen polymorphisms on the epidemiology of P. vivax malaria remains elusive. The objective of this study was to determine the distribution of asexual parasitaemia of P. vivax according to the Duffy antigen polymorphisms in Ethiopia.

METHODS

DNA was extracted from dried blood spots (DBS) collected from prospectively recruited 138 P. vivax-infected patients from health centres. The identification and estimation of P. vivax asexual parasitaemia were performed by microscopic examination and quantitative real-time polymerase chain reaction (PCR). Duffy genotyping was conducted by DNA sequencing in a total of 138 P.vivax infected samples.

RESULTS

The proportion of Duffy-negatives (FY*BES/FY*BES) in P. vivax infected patients was 2.9% (4/138). Duffy genotype FY*B/FY*BES (48.6%) was the most common, followed by FY*A/FY*BES genotype (25.4%). In one patient, the FY*02 W.01/FY*02 N.01 genotype conferring a weak expression of the Fyb antigen was observed. All P.vivax infected Duffy-negative patients showed low asexual parasitaemia (≤ 110 parasites/µL). The median P. vivax parasitaemia in Duffy-negative patients (53 parasites/µL) was significantly lower than those found in homozygous and heterozygous individuals (P < 0.0001).

CONCLUSION

Plasmodium vivax in Duffy-negative patients shows invariably low asexual parasitaemia. This finding suggests that the pathway used by P. vivax to invade Duffy-negative reticulocytes is much less efficient than that used in Duffy-positives. Moreover, the low asexual parasitaemia observed in Duffy-negative individuals could constitute an 'undetected silent reservoir', thus likely delaying the elimination of vivax malaria in Ethiopia.

Plasmodium falciparum Clinical Isolates Reveal Analogous Circulation of 3D7 and FC27 Allelic Variants and Multiplicity of Infection in Urban and Rural Settings: The Case of Adama and Its Surroundings, Oromia, Ethiopia

Background

Despite significant progress achieved globally in reducing malaria burden, still it is one of the major public health and economic problems in Ethiopia. Investigation of the local genetic polymorphism of P. falciparum, the most virulent and predominant malaria parasite primarily targeted in malaria control and elimination program, is paramount to assess intensity of parasite transmission. Analysis of the block 3 region of the msp-2 gene of P. falciparum provides strong molecular evidence to evaluate the real picture of malaria epidemiology to fine-tune the ongoing control and elimination programs in the region. Thus, this study was aimed at examining the status of such polymorphic gene and its implications in Adama and its surroundings.

Methods

148 isolates from patients with uncomplicated falciparum malaria were collected in the study from September 2019 to August 2020. Tween® 20 and the Chelex method were employed for parasite DNA extraction. msp-2 allelic families were genotyped by using nested polymerase chain reaction targeting its 3D7 and FC27 allelic variants followed by gel electrophoresis for fragment analysis.

Results

Seventeen different polymorphic forms of msp-2 allelic fragments were detected in the study area. Moreover, 47 (31.8%) and 41(27.7%) were detected for 3D7 and FC27 allelic families, respectively. Furthermore, the multiclonal allele type accounted for 60 (40.5%). The mean MOI was 1.4, and the heterogeneity index (He) is 0.49 indicating nearly intermediate malaria transmission in the study area.

Conclusions

The study revealed nearly intermediate genetic diversity and mean MOI of P. falciparum in the study area, demanding further scale up of the ongoing control and elimination efforts.

Seasonality and transmissibility of Plasmodium ovale in Bagamoyo District, Tanzania

BACKGROUND

Plasmodium ovale is a neglected malarial parasite that can form latent hypnozoites in the human liver. Over the last decade, molecular surveillance studies of non-falciparum malaria in Africa have highlighted that P. ovale is circulating below the radar, including areas where Plasmodium falciparum is in decline. To eliminate malaria where P. ovale is endemic, a better understanding of its epidemiology, asymptomatic carriage, and transmission biology is needed.

METHODS

We performed a pilot study on P. ovale transmission as part of an ongoing study of human-to-mosquito transmission of P. falciparum from asymptomatic carriers. To characterize the malaria asymptomatic reservoir, cross-sectional qPCR surveys were conducted in Bagamoyo, Tanzania, over three transmission seasons. Positive individuals were enrolled in transmission studies of P. falciparum using direct skin feeding assays (DFAs) with Anopheles gambiae s.s. (IFAKARA strain) mosquitoes. For a subset of participants who screened positive for P. ovale on the day of DFA, we incubated blood-fed mosquitoes for 14 days to assess sporozoite development.

RESULTS

Molecular surveillance of asymptomatic individuals revealed a P. ovale prevalence of 11% (300/2718), compared to 29% (780/2718) for P. falciparum. Prevalence for P. ovale was highest at the beginning of the long rainy season (15.5%, 128/826) in contrast to P. falciparum, which peaked later in both the long and short rainy seasons. Considering that these early-season P. ovale infections were low-density mono-infections (127/128), we speculate many were due to hypnozoite-induced relapse. Six of eight P. ovale-infected asymptomatic individuals who underwent DFAs successfully transmitted P. ovale parasites to A. gambiae.

CONCLUSIONS

Plasmodium ovale is circulating at 4-15% prevalence among asymptomatic individuals in coastal Tanzania, largely invisible to field diagnostics. A different seasonal peak from co-endemic P. falciparum, the capacity to relapse, and efficient transmission to Anopheles vectors likely contribute to its persistence amid control efforts focused on P. falciparum.

Five-Year Trend Analysis of Malaria Cases in East Shawa Zone, Ethiopia

BACKGROUND

Malaria is an infectious disease caused by Plasmodium parasites. Of the five human malaria parasites Plasmodium falciparum and Plasmodium vivax are the two co-endemic predominant and widely distributed species in Ethiopia, with major public health importance. Even though enormous effort has been made countrywide to reduce the disease burden little was reported about trends of malaria transmission in the several localities of malarious areas like East Shawa Zone, Ethiopia. Thus, the present study was aimed at assessing fiveyear (2016-2020) trends of malaria transmission at Adama, Boset and Lume districts of East Shawa Zone of Oromia Regional State, Ethiopia.

METHODS

Retrospective data was extracted from the central surveillance database of East Shawa Zone Health Office. The data collected was analyzed from September 2020 to December 2020 to examine trends of malaria epidemiology in three malarious districts in the Zone.

RESULTS

The results of the present study showed a remarkable decrease in slide positivity rate (SPR) from 16.3 to 1.4% from 2016 to 2018 in the areas. However, a recent slight increase of malaria SPR was observed. On the other hand, as age increases more male individuals were infected with malaria compared to female of similar age groups. Falciparum, vivax and mixed malaria infection accounted for 53%, 41% and 6% respectively.

CONCLUSIONS

Even though, an overall reduction of malaria incidence was revealed in the study areas, an increase in malaria SPR was observed in 2019 and 2020. Such inconsistency in reduction of malaria cases in the study area demands due attention of health planners.

Detection of high frequency of MAD20 allelic variants of Plasmodium falciparum merozoite surface protein 1 gene from Adama and its surroundings, Oromia, Ethiopia

Background

One of the major challenges in developing an effective vaccine against asexual stages of Plasmodium falciparum is genetic polymorphism within parasite population. Understanding the genetic polymorphism like block 2 region of merozoite surface protein-1 (msp-1) gene of P. falciparum enlighten mechanisms underlining disease pathology, identification of the parasite clone profile from the isolates, transmission intensity and potential deficiencies of the ongoing malaria control and elimination efforts in the locality. Detailed understanding of local genetic polymorphism is an input to pave the way for better management, control and elimination of malaria. The aim of this study was to detect the most frequent allelic variant of the msp-1 gene of P. falciparum clinical isolates from selected health facilities in Adama town and its surroundings, Oromia, Ethiopia.

Methods

One hundred thirty-nine clinical isolates were successfully amplified for msp-1 gene using specific primers. Nested PCR amplification was conducted targeting K1, MAD20, and R033 alleles followed by gel electrophoresis for fragment analysis. Based on the detection of a PCR fragment, infections were classified as monoclonal or multiple infections.

Results

19 different size polymorphism of msp-1 gene were identified in the study, with 67(48%) MAD20, 18 (13%) K-1 and 18 (13%) RO33 allelic family. Whereas, the multiple infections were 21(15%), 8 (5.8%), 4(2.9%), 3(2.2%) for MAD20 + K-1, MAD20 + RO33, K-1 + RO33, and MAD20 + K-1, RO33, respectively. The overall Multiplicity of infection (MOI) was 1.3 and the expected heterozygosity (He) was 0.39 indicating slightly low falciparum malaria transmission.

Conclusion

The status of msp-1 allele size polymorphism, MOI and He observed in the study revealed the presence of slightly low genetic diversity of P. falciparum clinical isolates. However, highly frequent MAD20 allelic variant was detected from clinical isolates in the study area. Moreover, the driving force that led to high predominance of MAD20 allelic variant revealed in such malaria declining region demands further research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03914-9.

Plasmodium vivax epidemiology in Ethiopia 2000-2020: A systematic review and meta-analysis

BACKGROUND

Ethiopia is one of the scarce African countries where Plasmodium vivax and P. falciparum co-exist. There has been no attempt to derive a robust prevalence estimate of P. vivax in the country although a clear understanding of the epidemiology of this parasite is essential for informed decisions. This systematic review and meta-analysis, therefore, is aimed to synthesize the available evidences on the distribution of P. vivax infection by different locations/regions, study years, eco-epidemiological zones, and study settings in Ethiopia.

METHODS

This study was conducted in accordance with Preferred Reposting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. Studies conducted and published over the last two decades (2000 to 2020) that reported an estimate of P. vivax prevalence in Ethiopia were included. The Cochrane Q (χ2) and the I2 tests were used to assess heterogeneity, and the funnel plot and Egger's test were used to examine publication bias. A p-value of the χ2 test <0.05 and an I2 value >75% were considered presence of considerable heterogeneity. Random effect models were used to obtain pooled estimate of P. vivax infection prevalence. This study is registered with PROSPERO (International Prospective Register of Systematic Reviews): ID CRD42020201761.

RESULTS

We screened 4,932 records and included 79 studies that enrolled 1,676,659 confirmed malaria cases, from which 548,214 (32.69%) were P. vivax infections and 1,116,581 (66.59%) were due to P. falciparum. The rest were due to mixed infections. The pooled estimate of P. vivax prevalence rate was 8.93% (95% CI: 7.98-9.88%) with significant heterogeneity (I2 = 100%, p<0.0001). Regional differences showed significant effects (p<0.0001, and I2 = 99.4%) on the pooled prevalence of P. vivax, while study years (before and after the scaling up of interventional activities) did not show significant differences (p = 0.9, I2 = 0%). Eco-epidemiological zones considered in the analysis did show a significant statistical effect (p<0.001, I2 = 78.5%) on the overall pooled estimate prevalence. Also, the study setting showed significant differences (p = 0.001, and I2 = 90.3%) on the overall prevalence, where significant reduction of P. vivax prevalence (4.67%, 95%CI: 1.41-7.93%, p<0.0001) was observed in studies conducted at the community level. The studies included in the review demonstrated lack of publication bias qualitatively (symmetrical funnel plot) and quantitatively [Egger's test (coefficient) = -2.97, 95% CI: -15.06-9.13, p = 0.62].

CONCLUSION

The estimated prevalence of P. vivax malaria in Ethiopia was 8.93% with P. vivax prevailing in the central west region of Ethiopia, but steadily extending to the western part of the country. Its distribution across the nation varies according to geographical location, study setting and study years.

Spatiotemporal distributed lag modelling of multiple Plasmodium species in a malaria elimination setting

In much of the Greater Mekong Sub-region, malaria is now confined to patches and small foci of transmission. Malaria transmission is seasonal with the spatiotemporal patterns being associated with variation in environmental and climatic factors. However, the possible effect at different lag periods between meteorological variables and clinical malaria has not been well studied in the region. Thus, in this study we developed distributed lagged modelling accounting for spatiotemporal excessive zero cases in a malaria elimination setting. A multivariate framework was also extended to incorporate multiple data streams and investigate the spatiotemporal patterns from multiple parasite species via their lagged association with climatic variables. A simulation study was conducted to examine robustness of the methodology and a case study is provided of weekly data of clinical malaria cases at sub-district level in Thailand.

Older children are at increased risk of Plasmodium vivax in south-central Ethiopia: a cohort study

BACKGROUND

Better understanding of the distribution of Plasmodium vivax and its risk factors could be used to prevent and control malaria infection. Therefore, the aim of this study was to characterize the distribution and risk factors of P. vivax, and to compare them with Plasmodium falciparum occurrence in south-central Ethiopia.

METHODS

A cohort of 34,548 individuals were followed for 121 weeks between 2014 and 2016 as part of larger cluster randomized controlled trial to evaluate the effect of long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) on malaria prevention in Ethiopia. Weekly home visit (active search) and patient self- report to health post (passive search) between the weekly home visits were used to register malaria cases. A blood sample was collected by finger prick and malaria was diagnosed using rapid diagnostic test (RDT). Generalized estimating equation (GEE) Poisson model that accounts for repeated measure of malaria episodes was applied to assess the risk factors of P. vivax episode.

RESULTS

The overall incidence rate of P. vivax was 7.4 episodes per 1000 person-years of observation. The study showed households closer to the lake Zeway and Bulbula river (potential mosquito breeding sites) were more at risk of P. vivax infection (incidence rate ratio (IRR): 1.33; 95% CI = 1.23-1.45). Furthermore, the age group under 5 years (IRR: 1.40, 95% CI = 1.10-1.79), the age group 5-14 years (IRR: 1.27, 95% CI = 1.03-1.57), households with less educated household head (IRR: 1.63, 95% CI = 1.10-2.44) and house roof made of thatch/leaf (IRR: 1.35, 95% CI = 1.11-1.65) were at higher risk for P. vivax. Similar explanatory variables such as distance from the breeding sites, age group (under 5 years but not 5-14 years old), educational status and type of housing were also found to be the predictors of P. falciparum incidence.

CONCLUSION

Households living closer to a mosquito breeding site, age group under 15 years, less educated household heads and thatch/leaf roof housing were the risk factor for P. vivax. The result of this study can be used for tailored interventions for malaria control and prevention by prioritizing those living close to potential mosquito breeding site, enhancing bed net use of children less than 15 years of age, and improving housing.

Spatial and genetic clustering of Plasmodium falciparum and Plasmodium vivax infections in a low-transmission area of Ethiopia

The distribution of malaria infections is heterogeneous in space and time, especially in low transmission settings. Understanding this clustering may allow identification and targeting of pockets of transmission. In Adama district, Ethiopia, Plasmodium falciparum and P. vivax malaria patients and controls were examined, together with household members and immediate neighbors. Rapid diagnostic test and quantitative PCR (qPCR) were used for the detection of infections that were genetically characterized by a panel of microsatellite loci for P. falciparum (26) and P. vivax (11), respectively. Individuals living in households of clinical P. falciparum patients were more likely to have qPCR detected P. falciparum infections (22.0%, 9/41) compared to individuals in control households (8.7%, 37/426; odds ratio, 2.9; 95% confidence interval, 1.3–6.4; P = .007). Genetically related P. falciparum, but not P. vivax infections showed strong clustering within households. Genotyping revealed a marked temporal cluster of P. falciparum infections, almost exclusively comprised of clinical cases. These findings uncover previously unappreciated transmission dynamics and support a rational approach to reactive case detection strategies for P. falciparum in Ethiopia.

A preliminary study on urban malaria during the minor transmission season: The case of Adama City, Oromia, Ethiopia

The distribution of malaria shows considerable spatial heterogeneity globally, regionally and locally. For the design of effective malaria control and elimination, and for its implementation in Ethiopia, urban malaria should be given due attention. Therefore, the present study was aimed to examine the status of urban malaria during the minor transmission season in Adama city. A total of 2590 febrile patients were screened using the gold standard microscopy-based blood test for malaria diagnosis from seven purposively selected health facilities found in Adama City from April to July 2018. Socio-demographic data were collected from malaria positive patients to correlate predisposing factors; like previous malaria history, settlement, travel history, age, and other associated risk factors with malaria incidence. Climatological data, such as temperature and relative humidity, recorded during the study period were also collected from the data base of Adama meteorology center for analysis. The microscopic data indicated that from a total of 2590 febrile patients screened for malaria during the study period 3.7% (97/2590) of them were confirmed malaria positive. Adolescents and adults (≥15 years of age) were found to be most affected by Plasmodium vivax (66%) and Plasmodium falciparum (20.5%), and mixed (6%). Analysis of the climatological data revealed a rise in environmental temperature and relative humidity during the study that coincides with the increase of malaria cases, since it creates favorable mosquito breeding for malaria transmission in the city. P. vivax was found as a predominant species in causing malaria burden indicating its public health problem in Adama city affecting the productive age group of the community, adolescents and adults, during the minor transmission season of malaria. In addition to its public health importance by causing morbidity and mortality such kind of scenario may also exacerbates poverty.

Negligible Impact of Mass Screening and Treatment on Mesoendemic Malaria Transmission at West Timor in Eastern Indonesia: A Cluster-Randomized Trial

Background

Mass screening and treatment (MST) aims to reduce malaria risk in communities by identifying and treating infected persons without regard to illness.

Methods

A cluster-randomized trial evaluated malaria incidence with and without MST. Clusters were randomized to 3, 2, or no MST interventions: MST3, 6 clusters (156 households/670 individuals); MST2, 5 clusters (89 households/423 individuals); and MST0, 5 clusters (174 households/777 individuals). All clusters completed the study with 14 residents withdrawing. In a cohort of 324 schoolchildren (MST3, n = 124; MST2, n = 57; MST0, n = 143) negative by microscopy at enrollment, we evaluated the incidence density of malaria during 3 months of MST and 3 months following. The MST intervention involved community-wide expert malaria microscopic screening and standard therapy with dihydroartemisinin-piperaquine and primaquine for glucose-6 phosphate dehydrogenase–normal subjects. All blood examinations included polymerase chain reaction assays, which did not guide on-site treatment.

Results

The risk ratios for incidence density of microscopically patent malaria in MST3 or MST2 relative to that in MST0 clusters were 1.00 (95% confidence interval [CI], .53–1.91) and 1.22 (95% CI, .42–3.55), respectively. Similar results were obtained with molecular analysis and species-specific (P. falciparum and P. vivax) infections. Microscopically subpatent, untreated infections accounted for 72% of those infected.

Conclusions

Two or 3 rounds of MST within 3 months did not impact the force of anopheline mosquito-borne infection in these communities. The high rate of untreated microscopically subpatent infections likely explains the observed poor impact.

Clinical Trials Registration

NCT01878357.

A retrospective analysis on the transmission of Plasmodium falciparum and Plasmodium vivax: the case of Adama City, East Shoa Zone, Oromia, Ethiopia

Background

Malaria is more often considered a problem of the rural poor and the disease has been overlooked in urban settings for centuries due to the assumption that economic development in urban areas results in better life conditions, such as improved housing, drainage system and environmental changes that makes urban areas not conducive for breeding of the malaria vector. But, for many African countries, including Ethiopia, in most urban areas, although there are rapid developments, they are characterized by poor housing, lack of sanitation and drainage of surface water that would provide favourable conditions for vector breeding. Limited studies have been conducted as far as urban malaria is concerned in Ethiopia. The purpose of this study was to assess the status of falciparum and vivax malaria transmission in Adama City, Eastern Shoa Zone, Oromia, Ethiopia. Understanding the local epidemiology of malaria will help policy makers and other stakeholders to design and implement tailored cost effective and efficient intervention strategies targeting urban malaria.

Methods

The study was designed to analyse 5-year trends of malaria burden by two co-endemic species in Ethiopia (Plasmodium falciparum and Plasmodium vivax) and its annual and seasonal transmission pattern in the city, by using retrospective data on malaria burden by species, malaria related inpatient department (IPD) and outpatient department (OPD) consultations from 2013/14 to 2017/18.

Results

OPD retrospective data analysis indicated that adolescents and adults (≥ 15 years of age) were most affected by P. vivax 43.5% (2986/6862) and P. falciparum 31.7% (2179/6862). Plasmodium vivax was found to be a predominant species in causing malaria burden in the city exhibiting less seasonal occurrence, and the relative burden of P. vivax is gradually increasing from year to year over P. falciparum.

Conclusion

Malaria is endemic to the city showing a public health problem. The productive group of the community, adolescents and adults, were most affected exacerbating poverty. Plasmodium vivax was found to be the highest malaria burden in the city and the observed epidemiological shift from P. falciparum to P. vivax calls for additional tailored intervention strategies to reduce the associated burden.

Prevalence of malaria relapse: systematic review with meta-analysis

Objective:

systematic review with a meta-analysis of the prevalence of malaria relapse.

Method:

it consisted in a search for cross-sectional studies, carried out in three databases, without application of filters. A total of 1,924 articles were identified, selected based on eligibility criteria. The selection was made in pairs from the reading of the titles, abstracts and text. The meta-analysis was performed with a statistical program.

Results:

a sample of 1,308 patients with malaria, ranging from 70 to 586 patients in the study. Relapse was estimated at 0.47%, with a 95% confidence interval and 99.04% of squared i. In the included studies, the prevalence of relapse ranged from 17.00% to 92.85%. The result of the meta-analysis is considered relevant, despite the heterogeneity.

Conclusion:

relapse is a phenomenon that can contribute to the maintenance of the endemicity of malaria in the world and to introduce it in non-affected areas. In addition, there is the need for advancement in the production of knowledge regarding this disease, to qualify the research methods on prevalence.

Molecular characterization and mapping of glucose-6-phosphate dehydrogenase (G6PD) mutations in the Greater Mekong Subregion

Background

Plasmodium vivax malaria elimination can only be achieved by the deployment of 8-aminoquinolines (primaquine and tafenoquine) in combination with ACT to kill both blood and liver-stage parasites. However, primaquine and the other 8-aminoquinolines cause dose-dependent haemolysis in subjects with G6PD deficiency, an X-linked disorder of red blood cells that is very common in populations living in tropical and subtropical areas. In order to inform safer use of 8-aminoquinolines in the Greater Mekong Subregion, a multi-centre study was carried out to assess the prevalence of G6PD deficiency and to identify the main G6PD variants in samples collected in Cambodia, Lao PDR, Myanmar, Thailand and Vietnam.

Methods

Blood samples were collected in the five countries during National Malaria Surveys or during Population Surveys. During Population Surveys samples were characterized for G6PD phenotype using the Fluorescent Spot Test. Samples were then genotyped for a panel of G6PD mutations.

Results

G6PD deficiency was found to be common in the region with an overall mean prevalence of deficient or mutated hemizygous males of 14.0%, ranging from a mean 7.3% in Thailand, 8.1% in Lao PDR, 8.9% in Vietnam, 15.8% in Myanmar and 18.8% in Cambodia. Mahidol and Viangchan mutations were the most common and widespread variants found among the nine investigated.

Conclusions

Owing to the high prevalence of G6PD deficiency in the Greater Mekong Subregion, strategies for vivax malaria elimination should include point-of-care G6PD testing (both qualitative and quantitative) to allow safe and wide treatment with 8-aminoquinolines.

Electronic supplementary material

The online version of this article (10.1186/s12936-019-2652-y) contains supplementary material, which is available to authorized users.

A pilot randomized controlled trial to compare the effectiveness of two 14-day primaquine regimens for the radical cure of vivax malaria in South India

BACKGROUND

Radical cure of Plasmodium vivax malaria requires treatment with a blood schizonticide and a hypnozoitocide (primaquine) to eradicate the dormant liver stages. There has been uncertainty about the operational effectiveness and optimum dosing of the currently recommended 14-day primaquine (PQ) course.

METHODS

A two centre, randomized, open-label, two arm study was conducted in South India. Patients were randomized to receive either high dose (0.5 mg base/kg body weight) or conventional dose (0.25 mg/kg) PQ for 14 days. Plasma concentrations of PQ and carboxyprimaquine (CPQ) on the 7th day of treatment were measured by reverse phase high performance liquid chromatography. Study subjects were followed up for 6 months. Recurrent infections were genotyped using capillary fragment length polymorphism of two PCR-amplified microsatellite markers (MS07 and MS 10).

RESULTS

Fifty patients were enrolled. Baseline characteristics and laboratory features did not differ significantly between the groups. Mean age of the study population was 42 ± 16.0 years. Recurrences 80-105 days later occurred in 4 (8%) patients, two in each the groups. All recurrences had the same microsatellite genotype as that causing the index infection suggesting all were relapses. One relapse was associated with low CPQ concentrations suggesting poor adherence.

CONCLUSIONS

This small pilot trial supports the effectiveness of the currently recommended lower dose (0.25 mg/kg/day) 14 day PQ regimen for the radical cure of vivax malaria in South India. Trial registration Clinical Trials Registry-India, CTRI/2017/03/007999. Registered 3 March 2017, http://ctri.nic.in/Clinicaltrials/regtrial.php?modid=1&compid=19&EncHid=82755.86366 .