Community-wide Prevalence of Malaria Parasitemia in HIV-Infected and Uninfected Populations in a High-Transmission Setting in Uganda

Asymptomatic malaria infection, associated factors and accuracy of diagnostic tests in a historically high transmission setting in Northern Uganda

BACKGROUND

Asymptomatic malaria infections are important parasite reservoirs and could sustain transmission in the population, but they are often unreported. A community-based survey was conducted to investigate the prevalence and factors associated with asymptomatic malaria infections in a historically high transmission setting in northern Uganda.

METHODS

Using a cross-sectional design, 288 children aged 2-15 years were enrolled and tested for the presence of malaria parasites using rapid diagnostic tests (RDTs) and blood smear microscopy between January to May 2022. Statistical analysis was performed using the exact binomial and Fisher's exact test with p ≤ 0.05 indicating significance. The logistic regression was used to explore factors associated with asymptomatic malaria infections.

RESULTS

Overall, the prevalence of asymptomatic infection was 34.7% (95% CI 29.2-40.5) with the highest observed in children 5-10 years 45.9% (95% CI 35.0-57.0). Gweri village accounted for 39.1% (95% CI 27.6-51.6) of malaria infections. Median parasite density was 1500 parasites/µl of blood. Plasmodium falciparum was the dominant species (86%) followed by Plasmodium malariae (5%). Factors associated with asymptomatic malaria infection were sleeping under mosquito net (Adjusted Odds Ratio (aOR) 0.27; 95% CI 0.13-0.56), p = 0.001 and presence of village health teams (VHTs) (aOR 0.02; 95% CI 0.01-0.45), p = 0.001. Sensitivity and specificity were higher for the P. falciparum/pLDH RDTs compared to HRP2-only RDTs, 90% (95% CI 86.5-93.5) and 95.2% (95% CI 92.8-97.7), p = 0.001, respectively.

CONCLUSION

Asymptomatic malaria infections were present in the study population and this varied with place and person in the different age groups. Plasmodium falciparum was the dominant parasite species however the presence of P. malariae and Plasmodium ovale was observed, which may have implication for the choice and deployment of diagnostic tools. Individuals who slept under mosquito net or had presence of functional VHTs were less likely to have asymptomatic malaria infection. P.f/pLDH RDTs performed better than the routinely used HRP2 RDTs. In view of these findings, investigation and reporting of asymptomatic malaria reservoirs through community surveys is recommended for accurate disease burden estimate and better targeting of control.

Malaria prevalence in HIV-positive children, pregnant women, and adults: a systematic review and meta-analysis

Background

Malaria in human immunodeficiency virus (HIV)-positive patients is an ever-increasing global burden for human health. The present meta-analysis summarizes published literature on the prevalence of malaria infection in HIV-positive children, pregnant women and adults.

Methods

This study followed the PRISMA guideline. The PubMed, Science Direct, Google Scholar, Scopus and Cochrane databases were searched for relevant entries published between 1 January 1983 and 1 March 2020. All peer-reviewed original papers evaluating the prevalence of malaria among HIV-positive patients were included. Incoherence and heterogeneity between studies were quantified by the I2 index and Cochran’s Q test. Publication and population biases were assessed with funnel plots, and Egger’s regression asymmetry test.

Results

A total of 106 studies were included in this systematic review. The average prevalence of malaria among HIV-positive children, HIV-positive pregnant women and HIV-positive adults was 39.4% (95% confidence interval [CI]: 26.6–52.9), 32.3% (95% CI = 26.3–38.6) and 27.3% (95% CI = 20.1–35.1), respectively. In adult patients with HIV, CD4+ (cluster of differentiation 4) < 200 cells/µl and age < 40 years were associated with a significant increase in the odds of malaria infection (odds ratio [OR] = 1.5, 95% CI = 1.2–1.7 and OR = 1.1, 95% CI = 1–1.3, respectively). Antiretroviral therapy (ART) and being male were associated with a significant decrease in the chance of malaria infection in HIV-positive adults (OR = 0.8, 95% CI = 0.7–0.9 and OR = 0.2, 95% CI = 0.2–0.3, respectively). In pregnant women with HIV, CD4+ count < 200 cells/µl was related to a higher risk for malaria infection (OR = 1.5, 95% CI = 1.1–1.9).

Conclusions

This systematic review demonstrates that malaria infection is concerningly common among HIV-positive children, pregnant women and adults. Among HIV-positive adults, ART medication and being male were associated with a substantial decrease in infection with malaria. For pregnant women, CD4+ count of < 200 cells/µl was a considerable risk factor for malaria infection.

Graphical Abstract

Efficacy and safety of dihydroartemisinin-piperaquine versus artemether-lumefantrine for treatment of uncomplicated Plasmodium falciparum malaria in Ugandan children: a systematic review and meta-analysis of randomized control trials

Background

The emergence of artemisinin resistance in Southeast Asia and Plasmodium falciparum kelch13 propeller gene mutations in sub-Saharan African pose the greatest threat to global efforts to control malaria. This is a critical concern in Uganda, where artemisinin-based combination therapy (ACT) is the first-line treatment for uncomplicated falciparum. The objective of this study was to compare the efficacy and safety of dihydroartemisinin–piperaquine (DHA–PQ) and artemether–lumefantrine (AL) for the treatment of uncomplicated falciparum malaria in Ugandan children.

Methods

A search of PubMed and the Cochrane Central Register of Controlled Trials for retrieving randomized controlled trials comparing the efficacy and safety of DHA–PQ and AL for treatment of uncomplicated falciparum malaria in Ugandan children was done. The search was performed up to 31 August 2020. The data extracted from eligible studies and pooled as risk ratio (RR) with a 95% confidence interval (CI), using Rev Man Software (5.4). The protocol was registered in PROSPERO, ID: CRD42020182354.

Results

Eleven trials were included in this review and two of them only included under safety outcome. Total 3798 participants were enrolled. The PCR unadjusted treatment failure was significantly lower with DHA–PQ at day 28 (RR 0.30, 95% CI 0.19–0.49; participants = 7863; studies = 5; I² = 93%, low quality evidence) and at day 42 (RR 0.53, 95% CI 0.38–0.76; participants = 1618; studies = 4; I² = 79%, moderate quality of evidence). The PCR adjusted treatment failure at day 42 was significantly lower with DHA–PQ treatment group (RR 0.45, 95% CI 0.28 to 0.72; participants = 1370; studies = 5, high quality of evidence), and it was below 5% in both arms at day 28 (moderate quality of evidence). AL showed a longer prophylactic effect on new infections which may last for up to 63 days (PCR-adjusted treatment failure: RR 2.04, 95% CI 1.13–3.70; participants = 1311; studies = 2, moderate quality of evidence). Compared to AL, DHA–PQ was associated with a slightly higher frequency of cough (RR 1.07, 95% CI 1.01 to 1.13; 2575 participants; six studies; high quality of evidence). In both treatment groups, the risk of recurrent parasitaemia due to possible recrudescence was less than 5% at day 28. The appearance of gametocyte between 29 and 42 days was also significantly lower in DHA–PQ than AL (RR 0.26, 95% CI 0.12 to 0.56; participants = 623; studies = 2; I² = 0%).

Conclusion

Compared to AL, DHA–PQ appeared to reduce treatment failure and gametocyte carriage in Ugandan children. This may trigger DHA–PQ to become the first-line treatment option. Both treatments were safe and well-tolerated.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03711-4.

Performance and Application of Commercially Available Loop-Mediated Isothermal Amplification (LAMP) Kits in Malaria Endemic and Non-Endemic Settings

Loop-mediated isothermal amplification (LAMP) is a sensitive molecular tool suitable for use as a near point-of-care test for the diagnosis of malaria. Recent meta-analyses have detailed high sensitivity and specificity of malaria LAMP when compared to microscopy, rapid diagnostic tests, and polymerase chain reaction in both endemic and non-endemic settings. Despite this, the use of malaria LAMP has primarily been limited to research settings to date. In this review, we aim to assess to what extent commercially available malaria LAMP kits have been applied in different settings, and to identify possible obstacles that may have hindered their use from being adopted further. In order to address this, we conducted a literature search in PubMed.gov using the search terms (((LAMP) OR (Loop-mediated isothermal amplification)) AND ((Malaria) OR (Plasmodium))). Focusing primarily on studies employing one of the commercially available kits, we then selected three key areas of LAMP application for further review: the performance and application of LAMP in malaria endemic settings including low transmission areas; LAMP for malaria screening during pregnancy; and malaria LAMP in returning travelers in non-endemic settings.

Increased malaria parasitaemia among adults living with HIV who have discontinued cotrimoxazole prophylaxis in Kitgum district, Uganda

Background

Although WHO recommends cotrimoxazole (CTX) discontinuation among HIV patients who have undergone immune recovery and are living in areas of low prevalence of malaria, some countries including Uganda recommend CTX discontinuation despite having a high malaria burden. We estimated the prevalence and factors associated with malaria parasitaemia among adults living with HIV attending hospital outpatient clinic before and after discontinuation of CTX prophylaxis.

Methods

Between March and April 2019, 599 participants aged 18 years and above, and attending Kitgum hospital HIV clinic in Uganda were enrolled in a cross study. A standardized questionnaire was administered and physical examination conducted. A finger-prick blood sample was collected for identification of malaria parasites by microscopy. The prevalence of parasitaemia was estimated and compared among participants on and those who had discontinued CTX prophylaxis, and factors associated with malaria parasitaemia assessed.

Results

Of the enrolled participants, 27 (4.5%) had malaria parasites and 452 (75.5%) had stopped CTX prophylaxis. Prevalence of malaria parasitaemia was significantly higher in participants who had stopped CTX prophylaxis (5.5% versus 1.4% p = 0.03) and increased with increasing duration since the discontinuation of prophylaxis. Compared to participants taking CTX, those who discontinued prophylaxis for 3–5 months and >5 months were more likely to have malaria parasites (adjusted prevalence ratio (aPR) = 1.64, 95% CI 0.37–7.29, p = 0.51, and aPR = 6.06, 95% CI 1.34–27.3, P = 0.02). Low CD4 count (< 250cells/mm³) was also associated with increased risk of having parasites (aPR = 4.31, 95% CI 2.13–8.73, p <0.001).

Conclusion

People from malaria endemic settings living with HIV have a higher prevalence of malaria parasitaemia following discontinuation of CTX compared to those still on prophylaxis. The risk increased with increasing duration since discontinuation of the prophylaxis. HIV patients should not discontinue CTX prophylaxis in areas of Uganda where the burden of malaria remains high. Other proven malaria control interventions may also be encouraged in HIV patients following discontinuation of CTX prophylaxis.

Microscopic and Submicroscopic Asymptomatic Plasmodium falciparum Infections in Ghanaian Children and Protection against Febrile Malaria

Naturally acquired immunity to Plasmodium falciparum malaria is thought to be nonsterile and sustained by persistence of low-level parasitemia. This study assessed the association between baseline microscopic and submicroscopic asymptomatic P. falciparum infections and antimalarial antibody levels and whether these parasitemia modify protective associations between antibody levels and malaria in Ghanaian children. Healthy children (N = 973, aged 0.5 to 12 years) were recruited into a 50-week longitudinal malaria cohort study from January 2016 to January 2017. Baseline asymptomatic parasitemia were determined by microscopy (microscopic parasitemia) and PCR (submicroscopic parasitemia), and antibody levels against crude schizont antigens were measured by enzyme-limited immunosorbent assay (ELISA). Antibody levels, parasite diversity, and risk of malaria in the ensuing transmission season were compared among children who had baseline asymptomatic microscopic or submicroscopic or no P. falciparum infections. Of the 99 asymptomatic baseline infections, 46 (46.5%) were microscopic and 53 (53.5%), submicroscopic. Cox regression analysis adjusting for age group, sex and community found a strong association between both baseline microscopic (hazard ratio [HR] = 0.36, 95% confidence interval [95% CI] = 0.21 to 0.63; P < 0.001) and submicroscopic (HR = 0.22, 95% CI = 0.11 to 0.44; P < 0.001) asymptomatic parasitemia and a reduced risk of febrile malaria compared to those who were uninfected at baseline. Baseline asymptomatic submicroscopic parasitemia had a significant effect on associations between antischizont antibodies and protection against febrile malaria (P < 0.001; likelihood ratio test). The study found both baseline P. falciparum asymptomatic microscopic and more strongly submicroscopic infections to be associated with protection against febrile malaria in the ensuing transmission season. This could have important implications for malaria seroepidemiological studies and vaccine trials.

Knowledge of malaria prevention among pregnant women and non-pregnant mothers of children aged under 5 years in Ibadan, South West Nigeria

Background

Adequate knowledge of malaria prevention and control can help in reducing the growing burden of malaria among vulnerable groups, particularly pregnant women and children aged under 5 years living in malaria endemic settings. Similar studies have been conducted but with less focus on these vulnerable groups. This study assessed knowledge of malaria prevention and control among the pregnant women and non-pregnant mothers of children aged under 5 years in Ibadan, Oyo State, South West Nigeria.

Methods

In this cross sectional study, data on socio-demographic, clinical and knowledge on malaria prevention was collected using interviewer administered questionnaires from consenting study participants attending Adeoyo maternity hospital between May and November 2016. Data was described using percentages and compared across the two maternal groups in the study population. Knowledge scoring from collected data was computed using the variables on causes, symptoms and prevention of malaria and thereafter dichotomised. Multivariate analyses were used to assess the interactive effect of socio demographic and clinical characteristics with malaria knowledge. Level of statistical significance was set at p < 0.05.

Results

Of the 1373 women in the study, 59.6% (818) were pregnant women while 40.4% (555) were mothers of children aged under 5 years. The respondents mean age was 29 years ± 5.2. A considerable proportion of both the pregnant women (n = 494, 60.4%) and the non-pregnant mothers of children aged under 5 years (n = 254, 45.8%) did not have correct knowledge on malaria prevention measures based on our assessment threshold (p < 0.001). Having a tertiary level education was associated with better knowledge on malaria (4.20 ± 1.18, F = 16.80, p < 0.001). Multivariate analyses showed that marital status, educational attainment, gravidity, and HIV status were significantly associated with knowledge of malaria prevention and control.

Conclusion

The findings indicate that socio-demographic factors such as marital and educational status greatly influence knowledge on malaria prevention and control measures. Key health stakeholders and authorities need to implement strategies and direct resources to improve the knowledge of mothers on malaria prevention and control. This would stem the tides of malaria related deaths among pregnant women and children aged under 5 years.

General contextual effects on neglected tropical disease risk in rural Kenya

The neglected tropical diseases (NTDs) are characterized by their tendency to cluster within groups of people, typically the poorest and most marginalized. Despite this, measures of clustering, such as within-group correlation or between-group heterogeneity, are rarely reported from community-based studies of NTD risk. We describe a general contextual analysis that uses multi-level models to partition and quantify variation in individual NTD risk at multiple grouping levels in rural Kenya. The importance of general contextual effects (GCE) in structuring variation in individual infection with Schistosoma mansoni, the soil-transmitted helminths, Taenia species, and Entamoeba histolytica/dispar was examined at the household-, sublocation- and constituency-levels using variance partition/intra-class correlation co-efficients and median odds ratios. These were compared with GCE for HIV, Plasmodium falciparum and Mycobacterium tuberculosis. The role of place of residence in shaping infection risk was further assessed using the spatial scan statistic. Individuals from the same household showed correlation in infection for all pathogens, and this was consistently highest for the gastrointestinal helminths. The lowest levels of household clustering were observed for E. histolytica/dispar, P. falciparum and M. tuberculosis. Substantial heterogeneity in individual infection risk was observed between sublocations for S. mansoni and Taenia solium cysticercosis and between constituencies for infection with S. mansoni, Trichuris trichiura and Ascaris lumbricoides. Large overlapping spatial clusters were detected for S. mansoni, T. trichiura, A. lumbricoides, and Taenia spp., which overlapped a large cluster of elevated HIV risk. Important place-based heterogeneities in infection risk exist in this community, and these GCEs are greater for the NTDs and HIV than for TB and malaria. Our findings suggest that broad-scale contextual drivers shape infectious disease risk in this population, but these effects operate at different grouping-levels for different pathogens. A general contextual analysis can provide a foundation for understanding the complex ecology of NTDs and contribute to the targeting of interventions.

Burden of asymptomatic malaria, anemia and relationship with cotrimoxazole use and CD4 cell count among HIV1-infected adults living in Gabon, Central Africa

Objective : This study determined the prevalence of asymptomatic Plasmodium (P.) falciparum infection and anemia in adults living with HIV/AIDS (PLHIV) and compared malaria prevalence between 858 HIV-infected (PLHIV) and 272 uninfected individuals in Gabon where such information are lacking. Factors influencing malaria and anemia were also investigated.

PATIENTS AND METHODS

Participants were screened for malaria. Available hemoglobin level, socio-demographic and use of prevention or treatment data were compared between both groups.

RESULTS

The prevalence of asymptomatic parasitemia was 13.5%, lower in PLHIV (7.1%) than uninfected individuals (33.8%) (p<0.01). Among the PLHIV, females (p<0.01), those aged below 25 years old (p=0.03), those with primary education (p=0.03) and those with a CD4 cell count below 200/mm3 (p=0.03) had a higher median parasitemia. Cotrimoxazole use was associated with a lower prevalence of malaria (p<0.01). Age below 25 years was independently associated with malaria in PLHIV (p<0.01). Anemia prevalence was 42.1% among the PLHIV, higher in the youngest and those with low CD4 cell count (p<0.01). P.falciparum-infected PLHIV aged below 25 years old, not under ART, with low CD4 cell count and under cotrimoxazole had the lowest median hemoglobin level.

CONCLUSION

The prevalence of asymptomatic malaria is low among the PLHIV while the burden of anemia is considerable. Age below 25 years and CD4 cell count are associated factors. The cotrimoxazole use reduces the frequency of malaria.

Vδ2+ T cell response to malaria correlates with protection from infection but is attenuated with repeated exposure

Vδ2+ γδ T cells are semi-innate T cells that expand markedly following P. falciparum (Pf) infection in naïve adults, but are lost and become dysfunctional among children repeatedly exposed to malaria. The role of these cells in mediating clinical immunity (i.e. protection against symptoms) to malaria remains unclear. We measured Vδ2+ T cell absolute counts at acute and convalescent malaria timepoints (n = 43), and Vδ2+ counts, cellular phenotype, and cytokine production following in vitro stimulation at asymptomatic visits (n = 377), among children aged 6 months to 10 years living in Uganda. Increasing age was associated with diminished in vivo expansion following malaria, and lower Vδ2 absolute counts overall, among children living in a high transmission setting. Microscopic parasitemia and expression of the immunoregulatory markers Tim-3 and CD57 were associated with diminished Vδ2+ T cell pro-inflammatory cytokine production. Higher Vδ2 pro-inflammatory cytokine production was associated with protection from subsequent Pf infection, but also with an increased odds of symptoms once infected. Vδ2+ T cells may play a role in preventing malaria infection in children living in endemic settings; progressive loss and dysfunction of these cells may represent a disease tolerance mechanism that contributes to the development of clinical immunity to malaria.

Characterizing microscopic and submicroscopic malaria parasitaemia at three sites with varied transmission intensity in Uganda

BACKGROUND

Parasite prevalence is a key metric used to quantify the burden of malaria and assess the impact of control strategies. Most published estimates of parasite prevalence are based on microscopy and likely underestimate true prevalence.

METHODS

Thick smear microscopy was performed in cohorts of children (aged 6 month to 10 years) and adults every 90 days over 2 years, at three sites of varying transmission intensity in Uganda. Microscopy-negative samples were tested for sub-microscopic parasitaemia using loop-mediated isothermal amplification (LAMP). Generalized estimating equation models were used to evaluate associations between age and parasitaemia, factors associated with sub-microscopic infection and associations between parasitaemia and haemoglobin.

RESULTS

A total of 9260 samples were collected from 1245 participants. Parasite prevalence among children across the three sites was 7.4, 9.4 and 28.8 % by microscopy and 21.3, 31.8 and 69.0 % by microscopy plus LAMP. Parasite prevalence among adults across the three sites was 3.1, 3.0 and 5.2 % by microscopy and 18.8, 24.2 and 53.5 % by microscopy plus LAMP. Among those with parasitaemia, adults and persons recently treated with anti-malarial therapy had the highest prevalence of sub-microscopic infection. Children with sub-microscopic or microscopic parasitaemia had lower mean haemoglobin levels compared to children with no detectable parasites.

CONCLUSIONS

Across a range of transmission intensities in Uganda, microscopy vastly underestimated parasite prevalence, especially among adults.