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Africa

Phenotypic, genotypic and biochemical changes during pyrethroid resistance selection in Anopheles gambiae mosquitoes

November 11, 2020 - 14:36 -- Open Access
Author(s): 
Machani MG, Ochomo E, Zhong D, Zhou G, Wang X, Githeko AK, Yan G, Afrane YA
Reference: 
Sci Rep. 2020 Nov 4;10(1):19063

The directional selection for insecticide resistance due to indiscriminate use of insecticides in public health and agricultural system favors an increase in the frequency of insecticide-resistant alleles in the natural populations. Similarly, removal of selection pressure generally leads to decay in resistance. Past investigations on the emergence of insecticide resistance in mosquitoes mostly relied on field survey of resistance in vector populations that typically had a complex history of exposure to various public health and agricultural pest control insecticides in nature, and thus the effect of specific insecticides on rate of resistance emergency or resistance decay rate is not known.

Evaluating the impact of larviciding with Bti and community education and mobilization as supplementary integrated vector management interventions for malaria control in Kenya and Ethiopia

November 4, 2020 - 10:08 -- Open Access
Author(s): 
Clifford M. Mutero, Collins Okoyo, Melaku Girma, Joseph Mwangangi, Lydia Kibe, Peter Ng’ang’a, Dereje Kussa, Gracious Diiro, Hippolyte Affognon and Charles M. Mbogo
Reference: 
Malaria Journal 2020 19:390, 3 November 2020

Malaria prevention in Africa is mainly through the use of long-lasting insecticide treated nets (LLINs). The objective of the study was to assess the effect of supplementing LLINs with either larviciding with Bacillus thuringiensis israelensis (Bti) or community education and mobilization (CEM), or with both interventions in the context of integrated vector management (IVM).

Not Open Access | Describing the current status of Plasmodium falciparum population structure and drug resistance within mainland Tanzania using molecular inversion probes

October 28, 2020 - 10:19 -- NOT Open Access
Author(s): 
Moser KA, Madebe RA, Bailey JA, et al.
Reference: 
Mol Ecol. 2020 Oct 26

High-throughput Plasmodium genomic data is increasingly useful in assessing prevalence of clinically important mutations and malaria transmission patterns. Understanding parasite diversity is important for identification of specific human or parasite populations that can be targeted by control programs, and to monitor the spread of mutations associated with drug resistance. An up-to-date understanding of regional parasite population dynamics is also critical to monitor the impact of control efforts.

Evaluation of a game-based training course to build capacity for insecticide resistance management in vector control programmes

October 20, 2020 - 16:04 -- Open Access
Author(s): 
Dormann C, Duda K, Hamainza B, Yewhalaw D, Hemingway C, Coleman M, Coleman M, Thomsen E
Reference: 
PLoS One. 2020 Oct 15;15(10):e0240514

Across Africa, malaria control programmes are increasingly challenged with the emergence of insecticide resistance among malaria vector populations. Confronted with this challenge, vector control staff must understand insecticide resistance management, think comprehensively and react positively when confronted with new problems. However, information on the subject is often only available through written guidelines that are difficult to put into practice.

Whole genome sequencing of Plasmodium vivax isolates reveals frequent sequence and structural polymorphisms in erythrocyte binding genes

October 13, 2020 - 13:01 -- Open Access
Author(s): 
Ford A, Kepple D, Lo E, et al.
Reference: 
PLoS Negl Trop Dis. 2020 Oct 12;14(10):e0008234

Plasmodium vivax malaria is much less common in Africa than the rest of the world because the parasite relies primarily on the Duffy antigen/chemokine receptor (DARC) to invade human erythrocytes, and the majority of Africans are Duffy negative. Recently, there has been a dramatic increase in the reporting of P. vivax cases in Africa, with a high number of them being in Duffy negative individuals, potentially indicating P. vivax has evolved an alternative invasion mechanism that can overcome Duffy negativity.

Rosettes integrity protects Plasmodium vivax of being phagocytized

October 8, 2020 - 15:37 -- Open Access
Author(s): 
Albrecht L, Lopes SCP, Costa FTM, et al.
Reference: 
Sci Rep. 2020 Oct 7;10(1):16706

Plasmodium vivax is the most prevalent cause of malaria outside of Africa. P. vivax biology and pathogenesis are still poorly understood. The role of one highly occurring phenotype in particular where infected reticulocytes cytoadhere to noninfected normocytes, forming rosettes, remains unknown. Here, using a range of ex vivo approaches, we showed that P. vivax rosetting rates were enhanced by plasma of infected patients and that total immunoglobulin M levels correlated with rosetting frequency.

The relationship between facility-based malaria test positivity rate and community-based parasite prevalence

October 8, 2020 - 08:01 -- Open Access
Author(s): 
Kamau A, Mtanje G, Mataza C, Malla L, Bejon P, Snow RW
Reference: 
PLoS One. 2020 Oct 7;15(10):e0240058

Malaria surveillance is a key pillar in the control of malaria in Africa. The value of using routinely collected data from health facilities to define malaria risk at community levels remains poorly defined.

Tolerance of Gambian Plasmodium falciparum to Dihydroartemisinin and Lumefantrine detected by Ex vivo Parasite Survival Rate Assay (PSRA)

October 7, 2020 - 15:39 -- Open Access
Author(s): 
Mbye H, Bojang F, Jawara AS, Njie B, Mohammed NI, Okebe J, D'Alessandro U, Amambua-Ngwa A
Reference: 
Antimicrob Agents Chemother. 2020 Oct 5:AAC.00720-20

Monitoring of Plasmodium falciparum sensitivity to antimalarial drugs in Africa is vital for malaria elimination. However, the commonly used ex-vivo/in-vitro IC50 test is inconsistent for several antimalarials, while the alternative ring-stage survival assay (RSA) for artemisinin derivatives has not been widely adopted. Here we applied an alternative two-colour flow-cytometry based parasite survival rate assay (PSRA) to detect ex-vivo antimalarial tolerance in P. falciparum isolates from The Gambia.

NOT Open Access | Piperaquine exposure is altered by pregnancy, HIV and nutritional status in Ugandan women

October 7, 2020 - 15:38 -- NOT Open Access
Author(s): 
Hughes E, Imperial M, Savic RM, et al.
Reference: 
Antimicrob Agents Chemother. 2020 Oct 5:AAC.01013-20

Dihydroartemisinin-piperaquine (DHA-PQ) provides highly effective therapy and chemoprevention for malaria in pregnant African women. PQ concentrations >10.3 ng/mL have been associated with reduced maternal parasitemia, placental malaria and improved birth outcomes. We characterized the population pharmacokinetics (PK) of PQ in a post-hoc analysis of human immunodeficiency virus (HIV)-infected and -uninfected pregnant women receiving DHA-PQ as chemoprevention every 4 or 8 weeks.

Generation of a malaria negative Ugandan birth weight standard for the diagnosis of small for gestational age

October 6, 2020 - 12:37 -- Open Access
Author(s): 
Zakama AK, Weekes T, Kajubi R, Kakuru A, Ategeka J, Kamya M, Muhindo MK, Havlir D, Jagannathan P, Dorsey G, Gaw SL
Reference: 
PLoS One. 2020 Oct 2;15(10):e0240157

Placental malaria is a known risk factor for small for gestational age (SGA) neonates. However, currently utilized international and African birthweight standards have not controlled for placental malaria and/or lack obstetrical ultrasound dating. We developed a neonatal birthweight standard based on obstetrically dated pregnancies that excluded individuals with clinical malaria, asymptomatic parasitemia, and placental malaria infection. We hypothesized that current curves underestimate true ideal birthweight and the prevalence of SGA.

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