Widespread pfhrp2/3 deletions and HRP2-based false-negative results in southern Ethiopia

BACKGROUND

Rapid diagnostic tests (RDTs) play a significant role in expanding case management in peripheral healthcare systems. Histidine-rich protein-2 (HRP2) antigen detection RDTs are predominantly used to diagnose Plasmodium falciparum infection. However, the evolution and spread of P. falciparum parasite strains with deleted hrp2/3 genes, causing false-negative results, have been reported. This study assessed the diagnostic performance of HRP2-detecting RDTs for P. falciparum cases and the prevalence of pfhrp2/3 deletions among symptomatic patients seeking malaria diagnosis at selected health facilities in southern Ethiopia.

METHODS

A multi-health facilities-based cross-sectional study was conducted on self-presenting febrile patients seeking treatment in southern Ethiopia from July to September 2022. A purposive sampling strategy was used to enroll patients with microscopically confirmed P. falciparum infections. A capillary blood sample was obtained to prepare a blood film for microscopy and a RDT using the SD Bioline™ Malaria Pf/Pv Test. Dried blood spot samples were collected for further molecular analysis. DNA was extracted using gene aid kits and amplification was performed using nested PCR assay. Exon 2 of hrp2 and hrp3, which are the main protein-coding regions, was used to confirm its deletion. The diagnostic performance of RDT was evaluated using PCR as the gold standard test for P. falciparum infections.

RESULTS

Of 279 P. falciparum PCR-confirmed samples, 249 (89.2%) had successful msp-2 amplification, which was then genotyped for hrp2/3 gene deletions. The study revealed that pfhrp2/3 deletions were common in all health centres, and it was estimated that 144 patients (57.8%) across all health facilities had pfhrp2/3 deletions, leading to false-negative PfHRP2 RDT results. Deletions spanning exon 2 of hrp2, exon 2 of hrp3, and double deletions (hrp2/3) accounted for 68 (27.3%), 76 (30.5%), and 33 (13.2%) of cases, respectively. The study findings revealed the prevalence of P. falciparum parasites lacking a single pfhrp2-/3-gene and that both genes varied across the study sites. This study also showed that the sensitivity of the SD Bioline PfHRP2-RDT test was 76.5% when PCR was used as the reference test.

CONCLUSION

This study confirmed the existence of widespread pfhrp2/3- gene deletions, and their magnitude exceeded the WHO-recommended threshold (> 5%). False-negative RDT results resulting from deletions in Pfhrp2/3- affect a country's attempts at malaria control and elimination. Therefore, the adoption of non-HRP2-based RDTs as an alternative measure is required to avoid the consequences associated with the continued use of HRP-2-based RDTs, in the study area in particular and in Ethiopia in general.

Spatiotemporal distribution and bionomics of Anopheles stephensi in different eco-epidemiological settings in Ethiopia

BACKGROUND

Malaria is a major public health concern in Ethiopia, and its incidence could worsen with the spread of the invasive mosquito species Anopheles stephensi in the country. This study aimed to provide updates on the distribution of An. stephensi and likely household exposure in Ethiopia.

METHODS

Entomological surveillance was performed in 26 urban settings in Ethiopia from 2021 to 2023. A kilometer-by-kilometer quadrant was established per town, and approximately 20 structures per quadrant were surveyed every 3 months. Additional extensive sampling was conducted in 50 randomly selected structures in four urban centers in 2022 and 2023 to assess households' exposure to An. stephensi. Prokopack aspirators and CDC light traps were used to collect adult mosquitoes, and standard dippers were used to collect immature stages. The collected mosquitoes were identified to species level by morphological keys and molecular methods. PCR assays were used to assess Plasmodium infection and mosquito blood meal source.

RESULTS

Catches of adult An. stephensi were generally low (mean: 0.15 per trap), with eight positive sites among the 26 surveyed. This mosquito species was reported for the first time in Assosa, western Ethiopia. Anopheles stephensi was the predominant species in four of the eight positive sites, accounting for 75-100% relative abundance of the adult Anopheles catches. Household-level exposure, defined as the percentage of households with a peridomestic presence of An. stephensi, ranged from 18% in Metehara to 30% in Danan. Anopheles arabiensis was the predominant species in 20 of the 26 sites, accounting for 42.9-100% of the Anopheles catches. Bovine blood index, ovine blood index and human blood index values were 69.2%, 32.3% and 24.6%, respectively, for An. stephensi, and 65.4%, 46.7% and 35.8%, respectively, for An. arabiensis. None of the 197 An. stephensi mosquitoes assayed tested positive for Plasmodium sporozoite, while of the 1434 An. arabiensis mosquitoes assayed, 62 were positive for Plasmodium (10 for P. falciparum and 52 for P. vivax).

CONCLUSIONS

This study shows that the geographical range of An. stephensi has expanded to western Ethiopia. Strongly zoophagic behavior coupled with low adult catches might explain the absence of Plasmodium infection. The level of household exposure to An. stephensi in this study varied across positive sites. Further research is needed to better understand the bionomics and contribution of An. stephensi to malaria transmission.

Malaria Risk Perception and Preventive Behaviors Among Elementary School Students, Southwest Ethiopia. Generalized Structural Equation Model

Background

In 2020, more than three billion of the world's population were the risk of being infected with malaria and four out of five deaths were from the African population. However, information is scarce on the association between risk perceptions and malaria prevention behaviors in resource-limited countries, particularly Ethiopia. Therefore, this study aimed to assess malaria risk perceptions and preventive behaviors.

Methods

A cross-sectional study design was conducted among 401 elementary school students in Jimma zone, Oromia, Ethiopia, from April 2 to June 8, 2020. Data were collected through interviews using a semi-structured questionnaire. The data were entered into Epi-data 4.6 and analyzed using STATA version 14.2. The descriptive statistics were presented using frequency and percentages. A Cronbach's α coefficient of 0.7 or higher was used to assess the reliability of each domain. The Generalized Structural Equation Model (GSEM) was employed to examine the relationships and prediction of explanatory variables with risk perception and preventive behaviors of malaria. The model with a lower information criterion was taken as a better-fitting model. Finally, the statistically significant model effects were declared at a P-value of less than 0.05 at a confidence interval of 95%.

Results

This study showed that having knowledge about malaria had an indirect positive effect on malaria preventive behavior (β = 1.29, 95% CI 0.11 to 2.47), and had a positive total effect on the preventive behavior (β = 2.99, 95% CI 0.08 to 2.67). Besides, an increased knowledge level had a direct positive effect on malaria risk perceptions (β = 0.08, 95% CI 0.01 to 0.14), and malaria risk perception had a direct positive effect on malaria preventive behavior (β = 1.21, 95% CI 0.10 to 2.31).

Conclusion and Recommendation

This study demonstrated that having knowledge about malaria had a direct and indirect association with malaria preventive behavior. An increased level of knowledge had a direct positive effect on malaria risk perceptions. Moreover, malaria risk perception had a direct positive effect on malaria preventive behavior. Therefore, malaria prevention-targeted interventions, behavior change, and knowledge enhancing communication should be enhanced or scaled up to contribute to prompt treatment and progress toward the elimination of malaria.

Malaria surveillance, outbreak investigation, response and its determinant factors in Waghemra Zone, Northeast Ethiopia: unmatched case-control study

Malaria is a major global public health concern, with around half of the world's population at risk of infection. It is one of the most common epidemic-prone diseases, resulting in on-going epidemics and significant public health problems. On September 12, 2022, Waghemra Zone malaria monitoring data revealed that the district was suffering an unusually high number of malaria cases. Therefore, the aim of this study was to assess the occurrence of malaria outbreaks and investigate contracting factors in Waghemra Zone, Northeast Ethiopia. A community-based case-control study with a 1:1 ratio was employed at Waghemra Zone from September 14 to November 27, 2022. A total of 260 individuals (130 cases and 130 controls) were included in the study. A structured questionnaire was used to collect the data. Malaria cases were confirmed by either microscopy or malaria rapid diagnostic tests. The magnitude of the outbreak was described by place, person, and time. A multivariable logistic regression analysis was conducted to identify malaria risk factors. A total of 13,136 confirmed cases of malaria were detected in the Waghemra zone, with an overall attack rate of 26.5 per 1000 and slide positivity rate was 43.0%. The predominant species was Plasmodium falciparum accounting for 66.1%. Children under five years old (AOR = 5.1; 95% CI 2.6-23.0), the presence of artificial water-holding bodies (AOR: 2.7; 95% CI 1.340-5.420), intermittent rivers closer to the living house (AOR = 4.9; 95% CI 2.51-9.62), sleeping outside a home (AOR = 4.9; 95% CI 2.51-9.62), and a lack of knowledge about malaria transmission and prevention (AOR: 9.7; 95% CI 4.459-20.930) were factors associated with malaria contraction. The overall attack rate for malaria during this outbreak was high. Children less than five years, the presence of mosquito breeding sites, staying outdoors overnight, and a lack of knowledge on malaria transmission and prevention were predictors of malaria. Early management of local vector breeding places, as well as adequate health education on malaria transmission and prevention methods, should be provided to the community to prevent such outbreaks in the future.

Suppressive, Curative, and Prophylactic Effects of Maesa lanceolata Forssk. against Rodent Malaria Parasite Plasmodium berghei

The artemisinin partial resistance is believed to be spread to artemisinin-based combination therapy partner drugs. As a result, new antiplasmodial compounds are required to treat resistant malaria infections. In the invention of antimalarial substances, claimed medical plants are precious resources. So, the current study was designed to assess the antiplasmodial effects of Maesa lanceolata in mice. In this study, preliminary phytoconstituent and in vivo acute oral toxicity tests were done. Early infection, established infection, and residual infection tests were employed to determine the antimalarial effects of the test drugs. Three doses (200, 400, and 600 mg/kg) of the extracts were provided orally to the test mice. Analysis of variance (one-way) followed by post hoc Tukey's test was used to analyze the difference between and within groups. Terpenoids, tannins, saponins, flavonoids, and alkaloids were detected in the phytochemical constituent analysis. Both 80% methanolic crude extract and solvent fractions had no toxic result at the 2000 mg/kg dose. All test drug doses suppressed parasite levels in a significant manner at all tests. The activity of chloroform fraction (maximum percentage suppression, 81.28%) overwhelms the crude extract activity. The curative effects of 80% methanolic crude extract, with a maximum of 80.22% parasitemia suppression, were greater than its suppressive and prophylactic effects. The 400 mg/kg dose of chloroform fraction resulted in a maximum survival period (18 days) than other doses of tested materials. The results of this investigation provide support for the activity of M. lanceolata leaf extract against malaria.