Epidemiological risk factors for clinical malaria infection in the highlands of Western Kenya

High prevalence and risk factors associated with asymptomatic malaria among children in Nkwen village, Northwest Region, Cameroon

BACKGROUND

In endemic locations, asymptomatic malaria is a major contribution to the rise in clinical malaria. In order to achieve the goal of interrupting malaria transmission, control programmes should take into consideration carriers of asymptomatic malaria parasite. Hence, the purpose of this study was to look at the prevalence and risk factors of asymptomatic malaria in children in Nkwen village.

METHODS

Using a cross-sectional and community-based design, conducted between June and December 2022, a total of 246 children were enrolled after obtaining informed and signed consent from parents and/ or guardians. To collect data, pre-tested, closed-ended, structured questionnaires were used, ensuring the accuracy and reliability of the information gathered. A digital thermometer with infrared forehead capability was used to take participants' body temperature, providing precise measurements and respondents with temperature < 37.5 °C, and not presenting any symptoms or indicators of malaria were included in the study, ensuring the focus on asymptomatic cases. Blood samples were collected by venipuncture and screened for the presence of asymptomatic parasitaemia using blood smear microscopy and nested polymerase chain reaction (PCR). Data was entered into Microsoft Excel worksheet and analysed using SPSS version 23 software. Logistic regression models were carried out to explore the risk factors associated with asymptomatic malaria at household and individual levels and statistically significant association was considered at a p-value < 0.05.

RESULTS

A total of 246 healthy children were examined for asymptomatic malaria infection using microscopy and PCR. Of the examined children, 65.9% (162/246) were malaria positive by PCR while 59.3% (146/246) were malaria positive by microscopy. Considering both diagnostic methods, females had a greater prevalence of asymptomatic malaria than males. In logistic analysis, the risk of developing asymptomatic malaria was associated several factors: previous malaria episode (OR = 5.14; CI 2.94-9.01), family history of malaria (OR = 3.86; CI 2.21-6.74), homestead near swampy areas (OR = 3.56; CI 2.10-10.61), non-utilization of insecticide treated nets (OR = 4.36; CI 2.53-7.5), non-usage of indoor residual spray (IRS) (OR = 6.67; CI 3.75-11.86) and opened eaves (OR = 3.86; CI 2.21-6.74). No associations were established between asymptomatic malaria and the following factors: age group (p > 0.05), gender (p > 0.05) and type of wall construction (p > 0.05).

CONCLUSION

The high rate of asymptomatic malaria in this study is a significant problem and may jeopardize the current malaria control effort. Personal and house-level risk factors were linked with asymptomatic malaria. Therefore, it should be considered when evaluating and restructuring more successful malaria elimination tactics to accomplish the intended goals of malaria control.

Plasmodium Parasitaemia and Urine Alterations among Pregnant Women Attending Antenatal Care in Aba Metropolis, Abia State, Nigeria

Malaria presents a huge threat to pregnant women, their foetus, and children below five years. This study is aimed at assessing malaria prevalence, associated clinical symptoms, and urine abnormalities among pregnant women in Aba metropolis, Abia State, Nigeria. A cross-sectional study involving 450 pregnant women purposively selected from nine health care centres was conducted. Data were analysed using SPSS version 26. The overall malaria prevalence rate was 68.4% (n = 308). Age group of 21-25 years had the highest prevalence rate of 20.4% (n = 92) while the least was recorded among the age group of 41-45 years (17 (3.8%)). Pregnant women in their first trimester had the greatest prevalence rate of 28.6% (n = 129), and the least prevalence was recorded among those in their third trimester (7 (15.6%)). The primigravidae were mostly infected at the rate of 27.7% (n = 125) whereas the multigravidae recorded the least prevalence of 85 (18.9%). Participants with secondary education were the most susceptible at the rate of 38.6% (n = 174). The infected participants exhibited significantly higher frequencies of reported fever (p > 0.001, OR 12.881, 95% CI 3.977-41.725) and headaches (p < 0.001, OR 4.688, 95% CI 1.819-12.083). However, cold, cough, body pains, poor appetite, and catarrh showed no significant association with malaria infection at p > 0.05. Participants using long-lasting insecticidal nets (LLINs) showed significantly lower prevalence rate of malaria infection (p < 0.001, OR 2.485, 95% CI 1.619-3.814). Malaria-infected participants showed statistically significant frequencies of proteinuria (p < 0.001, OR 274.14, 95% CI 16.91-4444.0), bilirubinuria (p < 0.001, OR 49.29, 95% CI 11.01-186.34), and urobilinogenuria (p < 0.001, OR 65.16, 95% CI 4.00-1062.40) than those not infected. Ascorbic acid, nitrate, and ketone showed no significant associations with malaria infection at p > 0.005. Infected participants had statistically significant amber and clear urine colour whereas there was no statistically significant difference between the pH levels of urine of the malaria-infected and malaria-noninfected pregnant women.

Prevalence and risk factors associated with malaria infection in children under two years of age in southern Togo prior to perennial malaria chemoprevention implementation

BACKGROUND

Malaria remains the leading cause of mortality and morbidity in young children in sub-Saharan Africa. To prevent malaria in children living in moderate-to-high malaria transmission areas, the World Health Organization has recommended perennial malaria chemoprevention (PMC). Prior to piloting PMC implementation in southern Togo, a household survey was conducted to estimate malaria infection prevalence in children under 2 years of age (U2).

METHODS

A cross-sectional community-based household survey was conducted in the Haho district in the Togo Plateaux region. A three-stage random sampling method was used to select study participants aged 10-23 months whose caretakers gave informed consent. The prevalence of Plasmodium infection, defined as a positive rapid diagnostic test (RDT), was estimated with 95% confidence interval (CI). Clinical malaria was defined as having a positive RDT plus fever (≥ 37.5 °C) or history of fever in the last 24 h. Mixed-effects logistic regression models were used to assess the child's, caretaker's, and household's factors associated with malaria infection.

RESULTS

A total of 685 children were included in the survey conducted January-February in 2022 (dry season). Median age was 17 months (interquartile range: 13-21). About 80% of the children slept under a bed net the night before the interview. Malaria infection prevalence was 32.1% (95% CI 27.7-37.0) with significant area variation (cluster range: 0.0-73.3). Prevalence of clinical malaria was 15.4% (95% CI 12.2-19.2). Children whose caretakers were animist (aOR: 1.71, 95% CI 1.19-2.46) and those living in mother-headed households (aOR: 2.39, 95% CI 1.43-3.99) were more likely to have a positive RDT. Living more than 5 km away from the nearest health facility (aOR: 1.60, 95% CI 1.04-2.44) and presence of two or more under-5-years children in the household (aOR: 1.44, 95% CI 1.01-2.07) were also associated with increased risk of infection.

CONCLUSION

One-third of the children U2 who participated in this survey had malaria infection, thus PMC could be a promising strategy to reduce malaria burden in young children in Plateaux region. Reinforcement of outreach services and targeting the poorest households should be prioritized to reduce the inequity in malaria prevention in children exposed to the infection.

Prevalence and predictors of asymptomatic malaria infection in Boricha District, Sidama Region, Ethiopia: implications for elimination strategies

BACKGROUND

Malaria remains a major public health threat in Ethiopia despite the tremendous progress made towards the 2030 elimination targets. The silent transmission of asymptomatic infection is one of the factors that enhance the persistence of the disease as a public health issue and impedes efforts to eliminate malaria. Thus, this study aimed at investigating the prevalence and risk factors of asymptomatic malaria infection in Boricha district, Sidama region of Ethiopia.

METHODS

A community-based cross-sectional study was conducted in eight selected kebeles (smallest administrative unit) in Boricha district. Representative households were chosen using a multi-stage sampling technique. A total of 573 participants were included in the study. Malaria diagnosis was performed using rapid diagnostic test (RDT) and microscopy. A structured questionnaire was administered to collect socio-demographic information. Epi data 3.1 was employed for data entry, and SPSS version 25 was used for analysis.

RESULTS

Of the 573 asymptomatic participants tested, 6.1% were found to be positive by RDT and 4.0% by microscopy. Participants aged under 5 years (AOR = 1.57, 95% CI 0.46-5.39) and 5-14 years old (AOR = 2.42, 95% CI 1.08-5.40), Insecticide-treated net utilization (AOR = 8.41; 95% CI 1.09-65.08), travel history (AOR = 6.85, 95% CI 2.32-20.26) and living in a house with windows (AOR = 2.11, 95% CI 1.02-4.36) were significantly associated with the asymptomatic malaria infection.

CONCLUSION

The findings of this study revealed that prevalence of asymptomatic malaria infection was higher in the study area. As a result, rigorous implementation of existing interventions, such as vector control and anti-malaria drugs, is strongly recommended. In addition, devising new ones that are suited to the contextual situations is highly suggested.

Assessing afebrile malaria and bed-net use in a high-burden region of India: Findings from multiple rounds of mass screening

A key obstacle in the fight against malaria is afebrile malaria. It remains undiagnosed and, therefore, is invisible to the health system. Apart from being a serious illness, it contributes to increased transmission. Existing studies in India have not adequately reported afebrile malaria and its determinants, including the use of long-lasting insecticide-treated nets (LLINs). This study used six waves of mass screening, which were conducted by the state government in the high-malaria-burden region of Chhattisgarh, a state in India, in 2020, 2021, and 2022. Each round of data collection included more than 15000 individuals. Descriptive statistics were used to analyse key indicators of malaria prevalence and LLIN use. Multivariate analyses were performed to identify the determinants of afebrile malaria and LLIN use. Malaria prevalence in the afebrile population varied from 0.6% to 1.4% across the different waves of mass screening. In comparison, malaria positivity among febrile individuals was greater than 33% in each wave. Afebrile malaria contributed to 19.6% to 47.2% of the overall malaria burden in the region. Indigenous communities (scheduled tribes) were more susceptible to malaria, including afebrile malaria. Individuals using LLINs were less likely to be affected by afebrile malaria. Overall, 77% of the individuals used LLINs in early monsoon season, and in winter the rate was lower at 55%. LLIN use was significantly associated with the number of LLINs the households received from the government. Although fever continues to be a primary symptom of malaria, afebrile malaria remains a significant contributor to the malaria burden in the region. The free distribution of LLINs should be expanded to include high-burden populations. Global policies must include strategies for surveillance and control of afebrile malaria in high-burden areas.

Civil Engineering and Malaria Risk: A Descriptive Study in a Rural Area of Cubal, Angola

(1) Background: Angola is among the high-burden countries with malaria cases globally. After 2013, we suspected an increase in the number of malaria cases in Cubal (Angola), previously in decline. Our objective was to evaluate the incidence rate in Cubal, overall and by neighborhood, for 2014, 2015, and 2016. (2) Methods: A retrospective, observational study was performed in Cubal (Angola) from January 2014 to December 2016, including all patients with a microbiologically confirmed diagnosis, treated at Cubal's Hospitals for this period of time. The principal variables calculated were the incidence rates of 2014, 2015, and 2016 in Cubal (overall and by neighborhood). (3) Results: There were 3249 malaria cases. The incidence rates were 2.27, 10.73, and 12.40 cases per 1000 inhabitants in 2014, 2015, and 2016, respectively. In the neighborhood, Hamavoko-Kasseke, there was a 10.73-fold increase in incidence during this period. Additionally, Hamavoko-Kasseke presents an anomalous distribution of malaria cases. (4) Conclusions: We observed an increase in the incidence of malaria in Cubal during the three-year study period. The case distribution was highly heterogeneous with hyperendemic areas, and we found a chronobiological association between the construction of a civil engineering project. This information could be useful for deciding which malaria control strategies must be implemented in this area.

A prospective cohort study of Plasmodium falciparum malaria in three sites of Western Kenya

BACKGROUND

Malaria in western Kenya is currently characterized by sustained high Plasmodial transmission and infection resurgence, despite positive responses in some areas following intensified malaria control interventions since 2006. This study aimed to evaluate long-term changes in malaria transmission profiles and to assess patterns of asymptomatic malaria infections in school children aged 5-15 years at three sites in western Kenya with heterogeneous malaria transmission and simultaneous malaria control interventions.

METHODS

The study was conducted from 2018 to 2019 and is based on data taken every third year from 2005 to 2014 during a longitudinal parasitological and mosquito adult surveillance and malaria control programme that was initiated in 2002 in the villages of Kombewa, Iguhu, and Marani. Plasmodium spp. infections were determined using microscopy. Mosquito samples were identified to species and host blood meal source and sporozoite infections were assayed using polymerase chain reaction.

RESULTS

Plasmodium falciparum was the only malaria parasite evaluated during this study (2018-2019). Asymptomatic malaria parasite prevalence in school children decreased in all sites from 2005 to 2008. However, since 2011, parasite prevalence has resurged by > 40% in Kombewa and Marani. Malaria vector densities showed similar reductions from 2005 to 2008 in all sites, rose steadily until 2014, and decreased again. Overall, Kombewa had a higher risk of infection compared to Iguhu (χ² = 552.52, df = 1, P < 0.0001) and Marani (χ² = 1127.99, df = 1, P < 0.0001). There was a significant difference in probability of non-infection during malaria episodes (log-rank test, χ² = 617.59, df = 2, P < 0.0001) in the study sites, with Kombewa having the least median time of non-infection during malaria episodes. Gender bias toward males in infection was observed (χ² = 27.17, df = 1, P < 0.0001). The annual entomological inoculation rates were 5.12, 3.65, and 0.50 infective bites/person/year at Kombewa, Iguhu, and Marani, respectively, during 2018 to 2019.

CONCLUSIONS

Malaria prevalence in western Kenya remains high and has resurged in some sites despite continuous intervention efforts. Targeting malaria interventions to those with asymptomatic infections who serve as human reservoirs might decrease malaria transmission and prevent resurgences. Longitudinal monitoring enables detection of changes in parasitological and entomological profiles and provides core baseline data for the evaluation of vector interventions and guidance for future planning of malaria control.

Influence of landscape heterogeneity on entomological and parasitological indices of malaria in Kisumu, Western Kenya

Background

Identification and characterization of larval habitats, documentation of Anopheles spp. composition and abundance, and Plasmodium spp. infection burden are critical components of integrated vector management. The present study aimed to investigate the effect of landscape heterogeneity on entomological and parasitological indices of malaria in western Kenya.

Methods

A cross-sectional entomological and parasitological survey was conducted along an altitudinal transect in three eco-epidemiological zones: lakeshore along the lakeside, hillside, and highland plateau during the wet and dry seasons in 2020 in Kisumu County, Kenya. Larval habitats for Anopheles mosquitoes were identified and characterized. Adult mosquitoes were sampled using pyrethrum spray catches (PSC). Finger prick blood samples were taken from residents and examined for malaria parasites by real-time PCR (RT-PCR).

Results

Increased risk of Plasmodium falciparum infection was associated with residency in the lakeshore zone, school-age children, rainy season, and no ITNs (χ² = 41.201, df = 9, P < 0.0001). Similarly, lakeshore zone and the rainy season significantly increased Anopheles spp. abundance. However, house structures such as wall type and whether the eave spaces were closed or open, as well as the use of ITNs, did not affect Anopheles spp. densities in the homes (χ² = 38.695, df = 7, P < 0.0001). Anopheles funestus (41.8%) and An. arabiensis (29.1%) were the most abundant vectors in all zones. Sporozoite prevalence was 5.6% and 3.2% in the two species respectively. The lakeshore zone had the highest sporozoite prevalence (4.4%, 7/160) and inoculation rates (135.2 infective bites/person/year). High larval densities were significantly associated with lakeshore zone and hillside zones, animal hoof prints and tire truck larval habitats, wetland and pasture land, and the wet season. The larval habitat types differed significantly across the landscape zones and seasonality (χ² = 1453.044, df = 298, P < 0.0001).

Conclusion

The empirical evidence on the impact of landscape heterogeneity and seasonality on vector densities, parasite transmission, and Plasmodium infections in humans emphasizes the importance of tailoring specific adaptive environmental management interventions to specific landscape attributes to have a significant impact on transmission reduction.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05447-9.

Quantifying the effect of human population mobility on malaria risk in the Peruvian Amazon

The impact of human population movement (HPM) on the epidemiology of vector-borne diseases, such as malaria, has been described. However, there are limited data on the use of new technologies for the study of HPM in endemic areas with difficult access such as the Amazon. In this study conducted in rural Peruvian Amazon, we used self-reported travel surveys and GPS trackers coupled with a Bayesian spatial model to quantify the role of HPM on malaria risk. By using a densely sampled population cohort, this study highlighted the elevated malaria transmission in a riverine community of the Peruvian Amazon. We also found that the high connectivity between Amazon communities for reasons such as work, trading or family plausibly sustains such transmission levels. Finally, by using multiple human mobility metrics including GPS trackers, and adapted causal inference methods we identified for the first time the effect of human mobility patterns on malaria risk in rural Peruvian Amazon. This study provides evidence of the causal effect of HPM on malaria that may help to adapt current malaria control programmes in the Amazon.

Malaria-associated risk factors among adolescents living in areas with persistent transmission in Senegal: a case-control study

BACKGROUND

In Senegal, malaria morbidity has sharply decreased over these past years. However, malaria epidemiology remains heterogeneous with persistent transmission in the southeastern part of the country and many cases among older children and adolescents. Little is known about factors associated with clinical malaria among this group. A better understanding of malaria transmission among this newly emerging vulnerable group will guide future interventions targeting this population group. This study aimed to identify factors associated with clinical malaria among adolescents in Senegal.

METHODS

A case-control study was conducted from November to December 2020 in four health posts located in the Saraya district. Cases were defined as adolescents (10-19 years) with an uncomplicated malaria episode with fever (temperature > 37.5°) or a history of fever and positive malaria rapid diagnostic test (RDT). Controls were from the same age group, living in the neighbourhood of the case, presenting a negative RDT. A standardized, pre-tested questionnaire was administered to each study participant followed by a home visit to assess the participant's living conditions. Factors associated with clinical malaria were assessed using stepwise logistic regression analysis.

RESULTS

In total, 492 individuals were recruited (246 cases and 246 controls). In a multivariate analysis, factors associated with clinical malaria included non-use of long-lasting insecticidal net (LLIN) (aOR = 2.65; 95% CI 1.58-4.45), non-use of other preventive measures (aOR = 2.51; 95% CI 1.53-4.11) and indoor sleeping (aOR = 3.22; 95% CI 1.66-6.23). Protective factors included 15-19 years of age (aOR = 0.38; 95% CI 0.23-0.62), absence of stagnant water around the house (aOR = 0.27; 95% CI 0.16-0.44), having a female as head of household (aOR = 0.47; 95% CI 0.25-0.90), occupation such as apprentice (OR = 0.24; 95% CI 0.11-0.52).

CONCLUSIONS

The study revealed that environmental factors and non-use of malaria preventive measures are the main determinants of malaria transmission among adolescents living in areas with persistent malaria transmission in Senegal. Strategies aimed at improving disease awareness and access to healthcare interventions, such as LLINs, are needed to improve malaria control and prevention among these vulnerable groups.

High asymptomatic malaria among seasonal migrant workers departing to home from malaria endemic areas in northwest Ethiopia

Background

In Ethiopia, thousands of seasonal migrant workers travel from non-malaria or mild malaria transmission areas to malaria-endemic areas for seasonal farm activities. Most of these migrants stay in the farm areas for land preparation, plowing, planting, weeding, and harvesting for a specific period and return to their living areas. However, there is limited evidence of how seasonal migrant workers contribute to the transmission of malaria to new or less malaria transmission areas.

Methods

A cross-sectional study was conducted at the departure phase of seasonal migrant workers in the Metema district from September 2018 to October 2019. A total of 1208 seasonal migrant workers were interviewed during their departure from farm sites to their homes. The face-to-face interviews were performed using a pretested structured questionnaire. Moreover, blood samples were collected from each study participant for microscopic malaria parasite examination. The data were fitted with the logistic regression model to estimate the predictors of malaria transmission.

Results

At departure to home, the prevalence of malaria among seasonal migrant workers was 17.5% (15.6–19.45%). Approximately 71.80% (177/212) of the cases were Plasmodium falciparum, and 28.20% (35/212) were Plasmodium vivax. Most seasonal migrant workers 934 (77.4%) were from rural residences and highlanders 660 (55%). Most 661 (55.4%) of the migrants visited two and more farm sites during their stay at development corridors for harvesting activities. Approximately 116 (54.7%) asymptomatic malaria cases returned to the Dembia 46 (21.7%), Chilaga 46 (19.8%) and Metema 28 (13.2%) districts.

Conclusion

In this study, asymptomatic malaria remains high among seasonal migrant workers departing to home from malaria endemic areas. This may fuel a resurgence of malaria transmission in the high lands and cause challenges to the country's malaria prevention and elimination efforts. Hence, tailored interventions for seasonal migrant workers could be in place to enhance malaria control and elimination in Ethiopia, such as asymptomatic malaria test and treat positive cases at departure and transit, and integration between malaria officers at their origin and departure for further follow-up to decrease any risk of spread at the origin.

Risk associations of submicroscopic malaria infection in lakeshore, plateau and highland areas of Kisumu County in western Kenya

BACKGROUND

Persons with submicroscopic malaria infection are a major reservoir of gametocytes that sustain malaria transmission in sub-Saharan Africa. Despite recent decreases in the national malaria burden in Kenya due to vector control interventions, malaria transmission continues to be high in western regions of the country bordering Lake Victoria. The objective of this study was to advance knowledge of the topographical, demographic and behavioral risk factors associated with submicroscopic malaria infection in the Lake Victoria basin in Kisumu County.

METHODS

Cross-sectional community surveys for malaria infection were undertaken in three eco-epidemiologically distinct zones in Nyakach sub-County, Kisumu. Adjacent regions were topologically characterized as lakeshore, hillside and highland plateau. Surveys were conducted during the 2019 and 2020 wet and dry seasons. Finger prick blood smears and dry blood spots (DBS) on filter paper were collected from 1,777 healthy volunteers for microscopic inspection and real time-PCR (RT-PCR) diagnosis of Plasmodium infection. Persons who were PCR positive but blood smear negative were considered to harbor submicroscopic infections. Topographical, demographic and behavioral risk factors were correlated with community prevalence of submicroscopic infections.

RESULTS

Out of a total of 1,777 blood samples collected, 14.2% (253/1,777) were diagnosed as submicroscopic infections. Blood smear microscopy and RT-PCR, respectively, detected 3.7% (66/1,777) and 18% (319/1,777) infections. Blood smears results were exclusively positive for P. falciparum, whereas RT-PCR also detected P. malariae and P. ovale mono- and co-infections. Submicroscopic infection prevalence was associated with topographical variation (χ2 = 39.344, df = 2, p<0.0001). The highest prevalence was observed in the lakeshore zone (20.6%, n = 622) followed by the hillside (13.6%, n = 595) and highland plateau zones (7.9%, n = 560). Infection prevalence varied significantly according to season (χ2 = 17.374, df = 3, p<0.0001). The highest prevalence was observed in residents of the lakeshore zone in the 2019 dry season (29.9%, n = 167) and 2020 and 2019 rainy seasons (21.5%, n = 144 and 18.1%, n = 155, respectively). In both the rainy and dry seasons the likelihood of submicroscopic infection was higher in the lakeshore (AOR: 2.71, 95% CI = 1.85-3.95; p<0.0001) and hillside (AOR: 1.74, 95% CI = 1.17-2.61, p = 0.007) than in the highland plateau zones. Residence in the lakeshore zone (p<0.0001), male sex (p = 0.025), school age (p = 0.002), and living in mud houses (p = 0.044) increased the risk of submicroscopic malaria infection. Bed net use (p = 0.112) and occupation (p = 0.116) were not associated with submicroscopic infection prevalence.

CONCLUSION

Topographic features of the local landscape and seasonality are major correlates of submicroscopic malaria infection in the Lake Victoria area of western Kenya. Diagnostic tests more sensitive than blood smear microscopy will allow for monitoring and targeting geographic sites where additional vector interventions are needed to reduce malaria transmission.

When Local Trade-Offs between SDGs Turn Out to Be Wealth-Dependent: Interaction between Expanding Rice Cultivation and Eradicating Malaria in Rwanda

Interactions between SDGs are increasingly mapped and mediating factors that determine whether existing synergies or trade-offs can be identified. However, if and how the wealth status of the concerned population shapes whether SDG interaction constitutes a vicious or virtuous circle is largely overlooked. This article focuses on interaction between SDG2 (nutrition) and SDG3 (health), in particular, the relationship between rice production intensification and the fight against malaria, and thus the role of wealth in explaining the trade-off. This study employed a large-scale survey of rural households (n = 3968) in eastern Rwanda, conducted at a time when a rapid expansion of rice fields co-existed with a strong resurgence of malaria. Logistic regression shows that rice-cultivating households faced significant higher malaria risk, as proxied by fever incidence, confirming the negative externality of agricultural intensification on public health through offering a habitat for vector-borne diseases. Even though rice-cultivating households tend to be higher up the local wealth distribution than those outside the rice sector, its distributional effects are generally biased against the poor. Poorer households outside the rice sector hardly share in the benefits from increased rice production but suffer the consequences in terms of increased malaria risk. The case thus draws attention to the importance of using a distributional lens when analyzing interaction between SDGs locally.

Five-Year Trend of Malaria Prevalence in Mojo Town, Central Ethiopia: Shifting Burden of the Disease and Its Implication for Malaria Elimination: A Retrospective Study

Introduction

Malaria continues to strike hardest against the health and economic development in Ethiopia. The peak of malaria incidence follows the main rainfall season in each year; however, its transmission tends to be highly heterogeneous within or between years and from area to area. Thus, this study was aimed to determine the trend prevalence of malaria in Mojo town, central Ethiopia.

Methods

A retrospective study was conducted in Mojo town, East Shoa zone, Ethiopia from February to March 2021. Malaria cases and related data documented between 2016 and 2020 were carefully reviewed from laboratory registration logbooks. The collected data were analyzed using descriptive statistics.

Results

A total of 19,106 blood films were examined from malaria-suspected patients. The overall microscopically confirmed prevalence of malaria was 4.2% (793/19,106). Plasmodium vivax was the predominant species accounting for 76.2% (604/793) of positive samples. Malaria cases declined from 259 in 2016 to 77 in 2020. The proportion of malaria was higher among males (64.8%, 514/793) than females (35.2%, 279/793) (P < 0.0001). Higher malaria cases were observed from the age group 15–24 years followed by the age group of 25–34 (P < 0.0001). The number of malaria cases was at a high level from September to November and lowest from December to February.

Conclusion

Despite a declining trend of malaria prevalence, it remains a public health burden in the area. P. vivax, the predominant species, should get attention during prevention and control strategies for the successful progress of the malaria elimination program.

Malaria risk factors in northern Namibia: The importance of occupation, age and mobility in characterizing high-risk populations

In areas of low and unstable transmission, malaria cases occur in populations with lower access to malaria services and interventions, and in groups with specific malaria risk exposures often away from the household. In support of the Namibian National Vector Borne Disease Program's drive to better target interventions based upon risk, we implemented a health facility-based case control study aimed to identify risk factors for symptomatic malaria in Zambezi Region, northern Namibia. A total of 770 febrile individuals reporting to 6 health facilities and testing positive by rapid diagnostic test (RDT) between February 2015 and April 2016 were recruited as cases; 641 febrile individuals testing negative by RDT at the same health facilities through June 2016 were recruited as controls. Data on socio-demographics, housing construction, overnight travel, use of malaria prevention and outdoor behaviors at night were collected through interview and recorded on a tablet-based questionnaire. Remotely-sensed environmental data were extracted for geo-located village residence locations. Multivariable logistic regression was conducted to identify risk factors and latent class analyses (LCA) used to identify and characterize high-risk subgroups. The majority of participants (87% of cases and 69% of controls) were recruited during the 2016 transmission season, an outbreak year in Southern Africa. After adjustment, cases were more likely to be cattle herders (Adjusted Odds Ratio (aOR): 4.46 95%CI 1.05-18.96), members of the police or other security personnel (aOR: 4.60 95%CI: 1.16-18.16), and pensioners/unemployed persons (aOR: 2.25 95%CI 1.24-4.08), compared to agricultural workers (most common category). Children (aOR 2.28 95%CI 1.13-4.59) and self-identified students were at higher risk of malaria (aOR: 4.32 95%CI 2.31-8.10). Other actionable risk factors for malaria included housing and behavioral characteristics, including traditional home construction and sleeping in an open structure (versus modern structure: aOR: 2.01 95%CI 1.45-2.79 and aOR: 4.76 95%CI: 2.14-10.57); cross border travel in the prior 30 days (aOR: 10.55 95%CI 2.94-37.84); and outdoor agricultural work at night (aOR: 2.09 95%CI 1.12-3.87). Malaria preventive activities were all protective and included personal use of an insecticide treated net (ITN) (aOR: 0.61 95%CI 0.42-0.87), adequate household ITN coverage (aOR: 0.63 95%CI 0.42-0.94), and household indoor residual spraying (IRS) in the past year (versus never sprayed: (aOR: 0.63 95%CI 0.44-0.90). A number of environmental factors were associated with increased risk of malaria, including lower temperatures, higher rainfall and increased vegetation for the 30 days prior to diagnosis and residing more than 5 minutes from a health facility. LCA identified six classes of cases, with class membership strongly correlated with occupation, age and select behavioral risk factors. Use of ITNs and IRS coverage was similarly low across classes. For malaria elimination these high-risk groups will need targeted and tailored intervention strategies, for example, by implementing alternative delivery methods of interventions through schools and worksites, as well as the use of specific interventions that address outdoor transmission.

Spatial and epidemiological drivers of Plasmodium falciparum malaria among adults in the Democratic Republic of the Congo

Background

Adults are frequently infected with malaria and may serve as a reservoir for further transmission, yet we know relatively little about risk factors for adult infections. In this study, we assessed malaria risk factors among adults using samples from the nationally representative, cross-sectional 2013–2014 Demographic and Health Survey (DHS) conducted in the Democratic Republic of the Congo (DRC). We further explored differences in risk factors by urbanicity.

Methods

Plasmodium falciparum infection was determined by PCR. Covariates were drawn from the DHS to model individual, community and environmental-level risk factors for infection. Additionally, we used deep sequencing data to estimate the community-level proportions of drug-resistant infections and included these estimates as potential risk factors. All identified factors were assessed for differences in associations by urbanicity.

Results

A total of 16 126 adults were included. Overall prevalence of malaria was 30.3% (SE=1.1) by PCR; province-level prevalence ranged from 6.7% to 58.3%. Only 17% of individuals lived in households with at least one bed-net for every two people, as recommended by the WHO. Protective factors included increasing within-household bed-net coverage (Prevalence Ratio=0.85, 95% CI=0.76–0.95) and modern housing (PR=0.58, 95% CI=0.49–0.69). Community-level protective factors included increased median wealth (PR=0.87, 95% CI=0.83–0.92). Education, wealth, and modern housing showed protective associations in cities but not in rural areas.

Conclusions

The DRC continues to suffer from a high burden of malaria; interventions that target high-risk groups and sustained investment in malaria control are sorely needed. Areas of high prevalence should be prioritised for interventions to target the largest reservoirs for further transmission.

Trends in malaria prevalence and risk factors associated with the disease in Nkongho-mbeng; a typical rural setting in the equatorial rainforest of the South West Region of Cameroon

Globally, malaria in recent years has witnessed a decline in the number of cases and death, though the most recent world malaria report shows a slight decrease in the number of cases in 2018 compared to 2017 and, increase in 2017 compared to 2016. Africa remains the region with the greatest burden of the disease. Cameroon is among the countries with a very high burden of malaria, with the coastal and forest regions carrying the highest burden of the disease. Nkongho-mbeng is a typical rural setting in the equatorial rain forest region of Cameroon, with no existing knowledge of the epidemiology of malaria in this locality. This study aimed at determining the current status of malaria epidemiology in Nkongho-mbeng. A cross-sectional survey was conducted, during which blood samples were collected from 500 participants and examined by microscopy. Risk factors such as, age, sex, duration of stay in the locality, housing type, environmental sanitation and intervention strategies including use of, LLINs and drugs were investigated. Trends in malaria morbidity were also determined. Of the 500 samples studied, 60 were positive, giving an overall prevalence of 12.0% with the prevalence of asymptomatic infection (10.8%), more than quadruple the prevalence of symptomatic infections (1.2%) and, fever burden not due to malaria was 1.4%. The GMPD was 6,869.17 parasites/μL of blood (95% C.I: 4,977.26/μL– 9,480.19/μL). A LLINs coverage of 84.4% and 77.88% usage was observed. Unexpectedly, the prevalence of malaria was higher among those sleeping under LLINs (12.56%) than those not sleeping under LLINs (8.97%), though the difference was not significant (p = 0.371). Being a male (p = 0.044), being unemployed (p = 0.025) and, living in Mbetta (p = 0.013) or Lekwe (p = 0.022) and the presence bushes around homes (p = 0.002) were significant risk factors associated with malaria infection. Trends in proportion demonstrated that, the prevalence of malaria amongst patients receiving treatment in the health center from 2015 to 2019 decreased significantly (p < 0.001) and linearly from 9.74% to 3.08% respectively. Data generated from this study can be exploited for development of a more effective control measures to curb the spread of malaria within Nkongho-mbeng.

Ten years of monitoring malaria trend and factors associated with malaria test positivity rates in Lower Moshi

Background

High altitude settings in Eastern Africa have been reported to experience increased malaria burden due to vector habitat expansion. This study explored possible associations between malaria test positivity rates and its predictors including malaria control measures and meteorological factors at a high-altitude, low malaria transmission setting, south of Mount Kilimanjaro.

Methods

Malaria cases reported at the Tanganyika Plantation Company (TPC) hospital’s malaria registers, meteorological data recorded at TPC sugar factory and data on bed nets distributed in Lower Moshi from 2009 to 2018 were studied. Correlation between bed nets distributed and malaria test positivity rates were explored by using Pearson correlation analysis and the associations between malaria test positivity rates and demographic and meteorological variables were determined by logistic regression and negative binomial regression analyses, respectively.

Results

Malaria cases reported at TPC hospital ranged between 0.48 and 2.26% per year and increased slightly at the introduction of malaria rapid diagnostic tests. The risk of testing positive for malaria were significantly highest among individuals aged between 6 and 15 years (OR = 1.65; 1.65 CI = 1.28–2.13; p = 0.001) and 16–30 years (OR = 1.49; CI = 1.17–1.89; p = 0.001) and when adjusted for age, the risk were significantly higher among male individuals when compared to female individuals (OR = 1.54; 1.00–1.31; p = 0.044). Malaria test positivity rates were positively associated with average monthly minimum temperatures and negatively associated with average monthly maximum temperatures (incidence rate ratio (IRR) = 1.37, 95% confidence interval (CI) = 1.05–1.78, p = 0.019 and IRR = 0.72, 95% CI = 0.58–0.91, p = 0.005, respectively). When analysed with one month lag for predictor variables, malaria test positivity rates were still significantly associated with average monthly minimum and maximum temperatures (IRR = 1.67, 95% CI = 1.28–2.19, p = 0.001 and IRR = 0.68, 95% CI = 0.54–0.85, p = 0.001, respectively). Average monthly rainfall and relative humidity with or without a one month lag was not associated with malaria test positivity rates in the adjusted models. Explopring possible associations between distribution of long-lasting insecticidal nets, (LLINs) and malaria test positivity rates showed no apparent correlation between numbers of LLINs distributed in a particular year and malaria test positivity rates.

Conclusion

In Lower Moshi, the risk of being tested positive for malaria was highest for older children and male individuals. Higher minimum and lower maximum temperatures were the strongest climatic predictors for malaria test positivity rates. In areas with extensive irrigation activity as in Lower Moshi, vector abundance and thus malaria transmission may be less dependent on rainfall patterns and humidity. Mass distribution of LLINs did not have an effect in this area with already very low malaria transmission.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03730-1.

Significant factors associated with malaria spread in Thailand: a cross-sectional study

Purpose

This paper aims to uncover new factors that influence the spread of malaria.

Design/methodology/approach

The historical data related to malaria were collected from government agencies. Later, the data were cleaned and standardized before passing through the analysis process. To obtain the simplicity of these numerous factors, the first procedure involved in executing the factor analysis where factors' groups related to malaria distribution were determined. Therefore, machine learning was deployed, and the confusion matrices are computed. The results from machine learning techniques were further analyzed with logistic regression to study the relationship of variables affecting malaria distribution.

Findings

This research can detect 28 new noteworthy factors. With all the defined factors, the logistics model tree was constructed. The precision and recall of this tree are 78% and 82.1%, respectively. However, when considering the significance of all 28 factors under the logistic regression technique using forward stepwise, the indispensable factors have been found as the number of houses without electricity (houses), number of irrigation canals (canals), number of shallow wells (places) and number of migrated persons (persons). However, all 28 factors must be included to obtain high accuracy in the logistics model tree.

Originality/value

This paper may lead to highly-efficient government development plans, including proper financial management for malaria control sections. Consequently, the spread of malaria can be reduced naturally.

Is the source of domestic water associated with the risk of malaria infection? Spatial variability and a mixed-effects multilevel analysis

BACKGROUND

There is a dearth of information on the relationship between domestic water source and malaria infection in malaria-endemic regions such as Tanzania. This study examined the geospatial variability and association between domestic water source and malaria prevalence in Tanzania.

METHODS

We analyzed data from a sample of 6707 children, aged 6-59 months, from the 2017 Tanzania Malaria Indicator Survey. The outcome variable was the result of malaria testing (positive or negative) and the main explanatory variable was domestic water source (piped or non-piped). Random effect variables were administrative region and geographical zone. ArcGIS 10.7 was used to create geospatial distribution maps. A STATA MP 14.0 was used to fit a mixed-effects multilevel logistic regression to examine the factors associated with malaria prevalence.

RESULTS

The prevalence of malaria and non-piped domestic water source was respectively 7.3% and 59.6%. The regions and zones with a higher prevalence of malaria also had a higher percentage of non-piped water. There was a statistically significant variation in the risk of malaria across the regions (variance = 1.27; 95% CI, 0.40-4.07) and zones (variance = 4.75; 95% CI, 1.46-15.46). The final fixed-effects model showed that non-piped domestic water was significantly associated with malaria prevalence (adjusted odds ratio (AOR) = 2.18; 95% CI, 1.64-2.89; P < 0.001).

CONCLUSIONS

A non-piped source of domestic water was independently associated with positive testing for malaria. Moreover, regions with a high percentage of non-piped domestic water had a correspondingly high prevalence of malaria.

Malaria among febrile neonates attending the neonatology unit of the Bamenda regional hospital

Malaria remains the leading cause of infant’s mortality in malaria endemic countries like Cameroon. Due to the presence of passively acquired maternal antibodies, malaria in neonates was thought to be scarce. Consequently routine malaria checks are mostly not considered for febrile neonates. Nonetheless findings from malaria endemic areas have proven that malaria in neonates is not uncommon. This study is therefore designed to evaluate malaria among febrile neonates attending the neonatology unit of the Bamenda Regional Hospital. A structured questionnaire and laboratory diagnostic test methods were used for data collection. Maternal sociodemographic data and malaria predisposing factors for neonates with and without malaria were determined using sums and percentages of mean. Regression analysis was used to determine the effects of age of mother, parity, mother’s educational level, sex of neonate and malaria predisposing factors on malaria parasitaemia. Chi-square (and Fisher’s exact) test was used to calculate sensitivity (%), specificity (%), predictive values (%), likelihood ratios, odd ratios, relative risk and attributable risk. A total of 189 neonates were included in the study out of which 33 (17.46%) tested malaria positive. 54.55% (18/33) of the malaria positive neonates were˃ 3 – 4 weeks old, while only 09.09% (03/33) were within 0 – 1 week of age. Neonates who presented with both signs of “fever + refusal to feed” were found to be most likely (P = 0.0188) to test malaria positive. Based on these findings routine malaria test is recommended especially for all neonates who presents with both signs of “fever + refusal to feed”, in malaria endemic regions.

Risk factors for malaria infection prevalence and household vector density between mass distribution campaigns of long-lasting insecticidal nets in North-western Tanzania

BACKGROUND

Long-lasting insecticidal nets (LLINs) are the most widely deployed vector control intervention in sub-Saharan Africa to prevent malaria. Recent reports indicate selection of pyrethroid insecticide resistance is widespread in mosquito vectors. This paper explores risk factors associated with malaria infection prevalence and vector density between mass distribution campaigns, changes in net coverage, and loss of protection in an area of high pyrethroid resistance in Northwest Tanzania.

METHODS

A cross sectional malaria survey of 3456 children was undertaken in 2014 in Muleba district, Kagera region west of Lake Victoria. Vector density was assessed using indoor light traps and outdoor tent traps. Anophelines were identified to species using PCR and tested for Plasmodium falciparum circumsporozoite protein. Logistic regression was used to identify household and environmental factors associated with malaria infection and regression binomial negative for vector density.

RESULTS

LLIN use was 27.7%. Only 16.9% of households had sufficient nets to cover all sleeping places. Malaria infection was independently associated with access to LLINs (OR: 0.57; 95% CI 0.34-0.98). LLINs less than 2 years old were slightly more protective than older LLINs (53 vs 65% prevalence of infection); however, there was no evidence that LLINs in good condition (hole index < 65) were more protective than LLINs, which were more holed. Other risk factors for malaria infection were age, group, altitude and house construction quality. Independent risk factors for vector density were consistent with malaria outcomes and included altitude, wind, livestock, house quality, open eaves and LLIN usage. Indoor collections comprised 4.6% Anopheles funestus and 95.4% Anopheles gambiae of which 4.5% were Anopheles arabiensis and 93.5% were Anopheles gambiae sensu stricto.

CONCLUSION

Three years after the mass distribution campaign and despite top-ups, LLIN usage had declined considerably. While children living in households with access to LLINs were at lower risk of malaria, infection prevalence remained high even among users of LLINs in good condition. While effort should be made to maintain high coverage between campaigns, distribution of standard pyrethroid-only LLINs appears insufficient to prevent malaria transmission in this area of intense pyrethroid resistance.

Rapid shifts in the age-specific burden of malaria following successful control interventions in four regions of Uganda

Background

Malaria control using long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) has been associated with reduced transmission throughout Africa. However, the impact of transmission reduction on the age distribution of malaria cases remains unclear.

Methods

Over a 10-year period (January 2009 to July 2018), outpatient surveillance data from four health facilities in Uganda were used to estimate the impact of control interventions on temporal changes in the age distribution of malaria cases using multinomial regression. Interventions included mass distribution of LLINs at all sites and IRS at two sites.

Results

Overall, 896,550 patient visits were included in the study; 211,632 aged < 5 years, 171,166 aged 5–15 years and 513,752 > 15 years. Over time, the age distribution of patients not suspected of malaria and those malaria negative either declined or remained the same across all sites. In contrast, the age distribution of suspected and confirmed malaria cases increased across all four sites. In the two LLINs-only sites, the proportion of malaria cases in < 5 years decreased from 31 to 16% and 35 to 25%, respectively. In the two sites receiving LLINs plus IRS, these proportions decreased from 58 to 30% and 64 to 47%, respectively. Similarly, in the LLINs-only sites, the proportion of malaria cases > 15 years increased from 40 to 61% and 29 to 39%, respectively. In the sites receiving LLINs plus IRS, these proportions increased from 19 to 44% and 18 to 31%, respectively.

Conclusions

These findings demonstrate a shift in the burden of malaria from younger to older individuals following implementation of successful control interventions, which has important implications for malaria prevention, surveillance, case management and control strategies.

Characterizing the Spatial Determinants and Prevention of Malaria in Kenya

The United Nations' Sustainable Development Goal 3 is to ensure health and well-being for all at all ages with a specific target to end malaria by 2030. Aligned with this goal, the primary objective of this study is to determine the effectiveness of utilizing local spatial variations to uncover the statistical relationships between malaria incidence rate and environmental and behavioral factors across the counties of Kenya. Two data sources are used-Kenya Demographic and Health Surveys of 2000, 2005, 2010, and 2015, and the national Malaria Indicator Survey of 2015. The spatial analysis shows clustering of counties with high malaria incidence rate, or hot spots, in the Lake Victoria region and the east coastal area around Mombasa; there are significant clusters of counties with low incidence rate, or cold spot areas in Nairobi. We apply an analysis technique, geographically weighted regression, that helps to better model how environmental and social determinants are related to malaria incidence rate while accounting for the confounding effects of spatial non-stationarity. Some general patterns persist over the four years of observation. We establish that variables including rainfall, proximity to water, vegetation, and population density, show differential impacts on the incidence of malaria in Kenya. The El-Nino-southern oscillation (ENSO) event in 2015 was significant in driving up malaria in the southern region of Lake Victoria compared with prior time-periods. The applied spatial multivariate clustering analysis indicates the significance of social and behavioral survey responses. This study can help build a better spatially explicit predictive model for malaria in Kenya capturing the role and spatial distribution of environmental, social, behavioral, and other characteristics of the households.