Parasitism of Locally Recruited Egg Parasitoids of the Fall Armyworm in Africa

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), is an insect native to the tropical and subtropical Americas that has recently spread to Africa, where it predominately attacks maize, sorghum and other plant species. Biological control is an environmentally friendly way of combatting the pest and contributes to an integrated pest management approach. In Africa, several trichogrammatid parasitoids and Telenomus remus Nixon (Hymenoptera: Platygastridae) have been found parasitizing eggs of the FAW. In Niger, the egg parasitoids encountered include Trichogrammatoidea sp. (Hymenoptera: Trichogrammatidae) and Telenomus remus Nixon. Parasitism of the FAW eggs by the two egg parasitoids was assessed in the laboratory, followed by field testing on sentinel eggs. In the laboratory, T. remus parasitized on average 78% of FAWeggs, compared to 25% for Trichogrammatoidea sp. Telenomus remus was able to parasitize egg masses that were fully covered with scales, while Trichogrammatoidea sp. parasitized only uncovered egg masses. On-farm releases of T. remus in sorghum fields caused up to 64% of FAW egg parasitism. Parasitized eggs yielded viable progeny, which can contribute to FAW egg parasitism build-up during the cropping season. Our findings lay the groundwork for the use of T. remus in augmentative releases against FAW in Africa

Scaling up Land Restoration Approaches to Reclaim the Hardpans of Niger for Agriculture using Sentinel 2 Imagery

Degraded lands, widespread across sub-Saharan Africa, are used mainly for grazing and firewood harvesting and have low agricultural production potential. Such areas have become degraded through overuse and removal of surface cover and associated erosion processes and are termed hardpans. Hardpans with high clay content, high cation exchange capacity (CEC) and water holding capacity have productive potential. ICRISAT has developed and scaled a gender sensitive approach Bioreclamation of Degraded Land” (BDL) that combines water harvesting technologies (planting pits, half-moon and trenches), application of compost and plantation of high value fruit trees and annual drought tolerant indigenous vegetables. In partnership with CRS in Niger, BDL was scaled to over 3000 villages (2014-18) which led to many benefits in food security and income generation for the local population. To scale further multi-spectral remote sensing based imagery of high resolution (10 m) can identify and map hardpans and differentiate higher potential sites for the BDL approach. These maps will be used to quantify the area under hardpans and the potential area in which the interventions can be scaled up

Improving the productivity of millet based cropping systems in the West African Sahel: Experiences from a long-term experiment in Niger

Resource-poor farmers who are living in the harsh environments of the West African Sahel (WAS) depend on subsistence orientated, low-input farming systems for meeting their livelihood needs. These largely extractive farming systems have resulted in nutrient depletion, soil fertility decline, low productivity and land degradation. A study conducted over 25 years in Niger, aimed to evaluate the long-term effects of organic and mineral fertilizers, cropping systems (CS) of millet and cowpea on crop productivity. The traditional millet/cowpea intercrop system without P fertilizer (TrM/C) was compared with four improved CS receiving P fertilizer: sole millet (MM), millet/cowpea intercrop (M/C), millet-cowpea rotation (M-C), and M/C and rotation with cowpea (M/C-C). Nitrogen fertilizer (N) and the residues of millet (CR) were applied alone or in combination in all five cropping systems. CR were always applied as mulch. The traditional system (TrM/C) produced the lowest millet grain yields (GY) (0.02–0.43 t/ha). All the four improved CS (MM, M/C, M-C and M/C-C) increased GY compared with the traditional system (TrM/C). The M/C and MM systems increased millet GY 3 and 3.3 times compared with the TrM/C, respectively. The M/C-C and M-C systems produced 4 and 4.2 times more GY than that of the TrM/C system, respectively. The lowest revenue was obtained with the TrM/C system. Except for the TrM/C, the revenue of the MM system was lower compared with combined cultivation of millet and cowpea. Compared with the TrM/C system, M/C and M/C-C provided 2 times more revenue. By providing 2.4 times more revenue than the TrM/C system, the M-C system was the most productive system. Cowpea provided from 54% and 56% of the revenue in M/C-C and M-C system, respectively. Soil organic carbon decreased in all the CS from 46% to 63% compared with the soil kept under natural vegetation fallow. The improved CS increased soil P from 3.4 to 4 times. Over the 25 years of cropping, the highest millet yields were obtained with the lower levels of rainfall indicating the role of nutrients in the system. The four improved systems maintained millet yields over the 25 years of cropping. By improving water and nutrient use efficiency, integrated management of mineral fertilizers, CR and cowpea affected more crop productivity than rainfall. We concluded that cereal-legume-based cropping systems treated with small doses of mineral fertilizers and CR could be used for sustainable management of soil fertility in low-input farming systems

Molecular markers of resistance to amodiaquine plus sulfadoxine-pyrimethamine in an area with seasonal malaria chemoprevention in south central Niger

Background In Niger, malaria transmission is markedly seasonal with most of the disease burden occurring in children during the rainy season. Seasonal malaria chemoprevention (SMC) with amodiaquine plus sulfadoxine– pyrimethamine (AQ + SP) is recommended in the country to be administered monthly just before and during the rainy season. Moreover, clinical decisions on use of SP for intermittent preventive treatment in pregnancy (IPTp) now depend upon the validated molecular markers for SP resistance in Plasmodium falciparum observed in the local parasite population. However, little is known about molecular markers of resistance for either SP or AQ in the south of Niger. To address this question, clinical samples which met clinical and biological criteria, were collected in Gabi, Madarounfa district, Maradi region, Niger in 2011–2012 (before SMC implementation). Molecular markers of resistance to pyrimethamine (pfdhfr), sulfadoxine (pfdhps) and amodiaquine (pfmdr1) were assessed by DNA sequencing. Results Prior to SMC implementation, the samples showed a high proportion of clinical samples that carried the pfdhfr 51I/59R/108N haplotype associated with resistance to pyrimethamine and pfdhps 436A/F/H and 437G mutations associated with reduced susceptibility to sulfadoxine. In contrast mutations in codons 581G, and 613S in the pfdhps gene, and in pfmdr1, 86Y, 184Y, 1042D and 1246Y associated with resistance to amodiaquine, were less frequently observed. Importantly, pfdhfr I164L and pfdhps K540E mutations shown to be the most clinically relevant markers for high level clinical resistance to SP were not detected in Gabi. Conclusion Although parasites with genotypes associated with the highest levels of resistance to AQ + SP are not yet common in this setting, their importance for deployment of SMC and IPTp dictates that monitoring of these markers of resistance should accompany these interventions. This study also highlights the parasite heterogeneity within a small spatial area and the need to use caution when extrapolating results from surveys of molecular markers of resistance in a single site to inform regional policy decisions.</p

Efficacy of artesunate-amodiaquine, dihydroartemisinin-piperaquine and artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum malaria in Maradi, Niger

Background: Malaria endemic countries need to assess efficacy of anti-malarial treatments on a regular basis. Moreover, resistance to artemisinin that is established across mainland South-East Asia represents today a major threat to global health. Monitoring the efficacy of artemisinin-based combination therapies is of paramount importance to detect as early as possible the emergence of resistance in African countries that toll the highest burden of malaria morbidity and mortality. Methods: A WHO standard protocol was used to assess efficacy of the combinations artesunate-amodiaquine (AS-AQ Winthrop (R)), dihydroartemisinin-piperaquine (DHA-PPQ, Eurartesim (R)) and artemether-lumefantrine (AM-LM, Coartem (R)) taken under supervision and respecting pharmaceutical recommendations. The study enrolled for each treatment arm 212 children aged 6-59 months living in Maradi (Niger) and suffering with uncomplicated falciparum malaria. The Kaplan-Meier 42-day PCR-adjusted cure rate was the primary outcome. A standardized parasite clearance estimator was used to assess delayed parasite clearance as surrogate maker of suspected artemisinin resistance. Results: No early treatment failures were found in any of the study treatment arms. The day-42 PCR-adjusted cure rate estimates were 99.5, 98.4 and 99.0% in the AS-AQ, DHA-PPQ and AM-LM arms, respectively. The reinfection rate (expressed also as Kaplan-Meier estimates) was higher in the AM-LM arm (32.4%) than in the AS-AQ (13.8%) and the DHA-PPQ arm (24.9%). The parasite clearance rate constant was 0.27, 0.26 and 0.25 per hour for AS-AQ, DHA-PPQ and AM-LM, respectively. Conclusions: All the three treatments evaluated largely meet WHO criteria (at least 95% efficacy). AS-AQ and AL-LM may continue to be used and DHA-PPQ may be also recommended as first-line treatment for uncomplicated falciparum malaria in Maradi. The parasite clearance rate were consistent with reference values indicating no suspected artemisinin resistance. Nevertheless, the monitoring of anti-malarial drug efficacy should continue

The effect of dosing strategies on the therapeutic efficacy of artesunate-amodiaquine for uncomplicated malaria : a meta-analysis of individual patient data

Background: Artesunate-amodiaquine (AS-AQ) is one of the most widely used artemisinin-based combination therapies (ACTs) to treat uncomplicated Plasmodium falciparum malaria in Africa. We investigated the impact of different dosing strategies on the efficacy of this combination for the treatment of falciparum malaria. Methods: Individual patient data from AS-AQ clinical trials were pooled using the WorldWide Antimalarial Resistance Network (WWARN) standardised methodology. Risk factors for treatment failure were identified using a Cox regression model with shared frailty across study sites. Results: Forty-three studies representing 9,106 treatments from 1999-2012 were included in the analysis; 4,138 (45.4%) treatments were with a fixed dose combination with an AQ target dose of 30 mg/kg (FDC), 1,293 (14.2%) with a non-fixed dose combination with an AQ target dose of 25 mg/kg (loose NFDC-25), 2,418 (26.6%) with a non-fixed dose combination with an AQ target dose of 30 mg/kg (loose NFDC-30), and the remaining 1,257 (13.8%) with a co-blistered non-fixed dose combination with an AQ target dose of 30 mg/kg (co-blistered NFDC). The median dose of AQ administered was 32.1 mg/kg [IQR: 25.9-38.2], the highest dose being administered to patients treated with co-blistered NFDC (median = 35.3 mg/kg [IQR: 30.6-43.7]) and the lowest to those treated with loose NFDC-25 (median = 25.0 mg/kg [IQR: 22.7-25.0]). Patients treated with FDC received a median dose of 32.4 mg/kg [IQR: 27-39.0]. After adjusting for reinfections, the corrected antimalarial efficacy on day 28 after treatment was similar for co-blistered NFDC (97.9% [95% confidence interval (CI): 97.0-98.8%]) and FDC (98.1% [95% CI: 97.6%-98.5%]; P = 0.799), but significantly lower for the loose NFDC-25 (93.4% [95% CI: 91.9%-94.9%]), and loose NFDC-30 (95.0% [95% CI: 94.1%-95.9%]) (P &lt; 0.001 for all comparisons). After controlling for age, AQ dose, baseline parasitemia and region; treatment with loose NFDC-25 was associated with a 3.5-fold greater risk of recrudescence by day 28 (adjusted hazard ratio, AHR = 3.51 [95% CI: 2.02-6.12], P &lt; 0.001) compared to FDC, and treatment with loose NFDC-30 was associated with a higher risk of recrudescence at only three sites. Conclusions: There was substantial variation in the total dose of amodiaquine administered in different AS-AQ combination regimens. Fixed dose AS-AQ combinations ensure optimal dosing and provide higher antimalarial treatment efficacy than the loose individual tablets in all age categories