On farm evaluation of the contribution of three green manures to maize yield in the semi-deciduous forest zone of Ghana

Low soil fertility is one of the major factors responsible for low crop yields on small-scale farms in Africa. The use of Chromolaena odorata, Crotalaria juncea and Panicum maximum and their combination with NPK for improving soil fertility and maize yield was investigated in the semideciduous forest zone of Ghana. Each plant material was applied at two application rates, 1 and 3 t ha-1. The field design was a randomized complete block with three replications. The plant materials caused an initial immobilization of nutrients which negatively affected maize grain yield in the major season. The plant materials plus N45P30K60 however, was able to provide nutrients that were sufficient to increase maize yields by over 85% relative to the control for the two consecutive seasons. N90P60K60 application alone produced the highest grain yield of 4.65 t ha-1 in the major season but less so in the minor season. Maize grain yield was not influenced by the quantity of plant materials application but was higher during the minor season than in the major season. The results of the study provide soil fertility management options for sustainable food production in the semi-deciduous forest zone of Ghana. Key words: Fertilizer, maize, organic residues, soil fertility

Effect of site characteristics on the productivity and economic returns from cassava legume intercropping in Ghana

In a 2-year field study, cassava was intercropped with four legumes (cowpea, pigeon pea, soyabean and Stylosanthes at three locations with different soil and environmental conditions, to determine the effect of site characteristics on the agronomic and economic advantage of the intercrop. The trial was a factorial experiment in a split plot design with three replications. A cost benefit analysis was conducted for the trial on the different crop arrangements. Root yield of cassava in the mixed cassava legume treatment across location during the first year was significantly higher (p < 0.05) compared to the stripped treatment. Root yield of cassava cowpea mixed intercrop for example ranged from 38 to 88 t/ha. In the second year however, considerable variations were observed among the treatments with NPK treatment giving the highest yield of 84 t/ha. This influenced the overall economic net benefits and showed that the intercrop advantage depended on the interaction of component crops, the growth environment and to some extent agronomic manipulations, suggesting that the best combination of crops under a particular system of management in one environment with a particular set of climate and soil conditions may not necessarily be suitable in another environment

Transcriptomic analysis of insecticide resistance in the lymphatic filariasis vector Culex quinquefasciatus

Culex quinquefasciatus plays an important role in transmission of vector-borne diseases of public health importance, including lymphatic filariasis (LF), as well as many arboviral diseases. Currently, efforts to tackle C. quinquefasciatus vectored diseases are based on either mass drug administration (MDA) for LF, or insecticide-based interventions. Widespread and intensive insecticide usage has resulted in increased resistance in mosquito vectors, including C. quinquefasciatus. Herein, the transcriptome profile of Ugandan bendiocarb-resistant C. quinquefasciatus was explored to identify candidate genes associated with insecticide resistance. High levels of insecticide resistance were observed for five out of six insecticides tested, with the lowest mortality (0.97%) reported to permethrin, while for DDT, lambdacyhalothrin, bendiocarb and deltamethrin the mortality rate ranged from 1.63–3.29%. Resistance to bendiocarb in exposed mosquitoes was marked, with 2.04% mortality following 1 h exposure and 58.02% after 4 h. Genotyping of the G119S Ace-1 target site mutation detected a highly significant association (p 8-fold increase vs unexposed controls). These results provide evidence that bendiocarb resistance in Ugandan C. quinquefasciatus is mediated by both target-site mechanisms and over-expression of detoxification enzymes

Syndromic algorithms for detection of gambiense human African trypanosomiasis in South Sudan.

BACKGROUND: Active screening by mobile teams is considered the best method for detecting human African trypanosomiasis (HAT) caused by Trypanosoma brucei gambiense but the current funding context in many post-conflict countries limits this approach. As an alternative, non-specialist health care workers (HCWs) in peripheral health facilities could be trained to identify potential cases who need testing based on their symptoms. We explored the predictive value of syndromic referral algorithms to identify symptomatic cases of HAT among a treatment-seeking population in Nimule, South Sudan. METHODOLOGY/PRINCIPAL FINDINGS: Symptom data from 462 patients (27 cases) presenting for a HAT test via passive screening over a 7 month period were collected to construct and evaluate over 14,000 four item syndromic algorithms considered simple enough to be used by peripheral HCWs. For comparison, algorithms developed in other settings were also tested on our data, and a panel of expert HAT clinicians were asked to make referral decisions based on the symptom dataset. The best performing algorithms consisted of three core symptoms (sleep problems, neurological problems and weight loss), with or without a history of oedema, cervical adenopathy or proximity to livestock. They had a sensitivity of 88.9-92.6%, a negative predictive value of up to 98.8% and a positive predictive value in this context of 8.4-8.7%. In terms of sensitivity, these out-performed more complex algorithms identified in other studies, as well as the expert panel. The best-performing algorithm is predicted to identify about 9/10 treatment-seeking HAT cases, though only 1/10 patients referred would test positive. CONCLUSIONS/SIGNIFICANCE: In the absence of regular active screening, improving referrals of HAT patients through other means is essential. Systematic use of syndromic algorithms by peripheral HCWs has the potential to increase case detection and would increase their participation in HAT programmes. The algorithms proposed here, though promising, should be validated elsewhere