BackgroundMalaria management policies currently recommend that the treatment should only be administered after laboratory confirmation. Where microscopy is not available, rapid diagnostic tests (RDTs) are the usual alternative. Conclusive evidence is still lacking on the safety of a test-based strategy for children. Moreover, no formal attempt has been made to estimate RDTs accuracy on malaria-attributable fever. This study aims at estimating the accuracy of a RDT for the diagnosis of both malaria infection and malaria - attributable fever, in a region of Burkina Faso with a typically seasonal malaria transmission pattern.MethodsCross-sectional study. Subjects: all patients aged > 6 months consulting during the study periods. Gold standard for the diagnosis of malaria infection was microscopy. Gold standard for malaria-attributable fever was the number of fevers attributable to malaria, estimated by comparing parasite densities of febrile versus non-febrile subjects. Exclusion criteria: severe clinical condition needing urgent care.ResultsIn the dry season, 186/852 patients with fever (22%) and 213/1,382 patients without fever (15%) had a Plasmodium falciparum infection. In the rainy season, this proportion was 841/1,317 (64%) and 623/1,669 (37%), respectively. The attributable fraction of fever to malaria was 11% and 69%, respectively. The RDT was positive in 113/400 (28.3%) fever cases in the dry season, and in 443/650 (68.2%) in the rainy season. In the dry season, the RDT sensitivity and specificity for malaria infection were 86% and 90% respectively. In the rainy season they were 94% and 78% respectively. In the dry season, the RDT sensitivity and specificity for malaria-attributable fever were 94% and 75%, the positive predictive value (PPV) was 9% and the negative predictive value (NPV) was 99.8%. In the rainy season the test sensitivity for malaria-attributable fever was 97% and specificity was 55%. The PPV ranged from 38% for adults to 82% for infants, while the NPV ranged from 84% for infants to over 99% for adults.ConclusionsIn the dry season the RDT has a low positive predictive value, but a very high negative predictive value for malaria-attributable fever. In the rainy season the negative test safely excludes malaria in adults but not in children.

BackgroundMalaria rapid diagnostic tests (RDTs) have generally been found reliable and cost-effective. In Burkina Faso, the adherence of prescribers to the negative test result was found to be poor. Moreover, the test accuracy for malaria-attributable fever (MAF) is not the same as for malaria infection. This paper aims at determining the costs and benefits of two competing strategies for the management of MAF: presumptive treatment for all or use of RDTs.MethodsA cost benefit analysis was carried out using a decision tree, based on data previously obtained, including a randomized controlled trial (RCT) recruiting 852 febrile patients during the dry season and 1,317 in the rainy season. Cost and benefit were calculated using both the real adherence found by the RCT and assuming an ideal adherence of 90% with the negative result. The main parameters were submitted to sensitivity analysis.Results and discussionAt real adherence, the test-based strategy was dominated. Assuming ideal adherence, at the value of 525 € for a death averted, the total cost of managing 1,000 febrile children was 1,747 vs. 1,862 € in the dry season and 1,372 vs. 2,138 in the rainy season for the presumptive vs. the test-based strategy. For adults it was 2,728 vs. 1,983 and 2,604 vs. 2,225, respectively. At the subsidized policy adopted locally, assuming ideal adherence, the RDT would be the winning strategy for adults in both seasons and for children in the dry season.At sensitivity analysis, the factors most influencing the choice of the better strategy were the value assigned to a death averted and the proportion of potentially severe NMFI treated with antibiotics in patients with false positive RDT results. The test-based strategy appears advantageous for adults if a satisfactory adherence could be achieved. For children the presumptive strategy remains the best choice for a wide range of scenarios.ConclusionsFor RDTs to be preferred, a positive result should not influence the decision to treat a potentially severe NMFI with antibiotics. In the rainy season the presumptive strategy always remains the better choice for children.

Rice improvement for disease resistance has scarcely involved farmers' knowledge in Sub-Saharan Africa. A participatory rural appraisal was conducted in two main rice cultivation areas in Burkina Faso to assess farmers' awareness of rice production constraints with emphasis on rice yellow mottle disease (RYMD) and its management. Farmers' preference for rice varieties to be used in the breeding program was also assessed. Major concerns for rice cultivation as perceived by farmers were water shortage and RYMD. However, relative importance of each constraint depended on the survey areas, RYMD being prominent at Banzon while water shortage predominated at Mogtedo. Mogtedo farmers preferred rice variety FKR19 because of its tolerance to drought. At Banzon, farmers' first criterion was taste which was reflected in the choice of variety FKR18. Yield was also a major criterion in both areas, positioning NERICA varieties FKR56N, FKR62N, and FKR60N among the top preferred varieties. Farmers mentioned RYMD as the most important rice disease. Most farmers used varietal shifts or pesticide treatments for RYMD management. RYMD incidence reached 28% in average at Banzon over the 2012-2013 main growing seasons. In rice varieties FKR56N, FKR62N and TS2, diseased plants yielded 79.3% less than the healthy ones. Accordingly, based on disease incidence, overall yield loss in the study area was estimated at 22.3%. Altogether, rice production can be significantly increased by taking RYMD into account in a participatory rice breeding strategy.

02/08 Fax : (226) 25 31 92 75 A B S T R A C T Cowpea (Vigna unguiculata (L.) Walp.) is one the main leguminous crop plants world wide, particularly in sub-Saharan Africa where the rainfall is low and often unevenly distributed. However, its production is limited by insect attacks and numerous diseases including those caused by viruses. In Burkina Faso, the Cowpea Aphid-Borne Mosaic Virus (CABMV) is one of the viruses capable of causing 7-60% of yield losses. The aim of this study is to assess the susceptibility of 21 cowpea varieties against CABMV and to also assess the yield losses caused by this virus on each of the varieties. In this context trial was conducted on INERA research stations at Kamboinsé and Farako-Bâ in 2012 and 2013. Twenty one varieties were used for this study. The experimental design used is a split-plot with 4 repetitions for which the first 2 repetitions were inoculated with the CABMV. Symptoms caused by the CABMV on the 21 varieties of cowpea were of a great diversity. The assessment of the virus in infected plant samples from these varieties by ELISA test allowed detecting the mosaic virus in all samples that presented mosaic symptoms. The number of flowers and pods strongly varied depending to the type of plant (inoculated or non-inoculated plant) and the variety. Yields from the different varieties, comprised between 187 and 6250 kg haG 1 , were influenced by the site, the year, the variety and the type of plant. Yields losses were ranged from 3-64% depending to the variety.

Rice stripe necrosis virus (RSNV) was first described in 1977 as a new virus infecting rice in Cote d'Ivoire (3) and was subsequently observed in Liberia, Nigeria, and Sierra Leone (2). RSNV is a soil-borne virus transmitted by the fungus Polymyxa graminis (1) and belongs to the genus Benyvirus (4). During a survey carried out in April of 2013, severe symptoms characterized by seedling death, severe plant malformation, and foliar striping were observed on rice plants in an experimental field of INERA at Banfora located in western Burkina Faso. Disease incidence in the field was estimated to be 80 ± 5%. The symptoms of disease were successfully transmitted to the susceptible rice (Oryza sativa) cultivar IR64 by soil transmission experiments (1). RSNV was detected by ELISA using a polyclonal antiserum (1), kindly provided by Dr. Denis Fargette, IRD, Montpellier, France. Total nucleic acid was extracted with TRIzol reagent (Invitrogen) from IR64 and field infected samples. The presence of the virus was confirmed by RT-PCR using primers 5′-CATCTTGTCGAGATGAG-3′ and 5′-GCGTTGTCTTTATCAGTG-3′ for specific sequences flanking the RNA2 CP gene. The RT-PCR product was directly sequenced and the sequence was deposited in GenBank (Accession No. LK023710). Sequence analysis showed that the CP gene of the RSNV isolate from Burkina Faso shared the highest nucleotide sequence identity (97.6%) with the known RSNV CP gene sequence from the Colombian isolate (EU099845) available in GenBank, confirming the presence of RSNV in the rice crops in Burkina Faso. To our knowledge, this is the first confirmed report of RSNV in Burkina Faso. Further studies are needed to determine its incidence and spread in the country. Detection of RSNV in Burkina Faso signals the urgent need for adoption of appropriate measures to restrict the spread and impact of this virus within Africa. References: (1) C. Fauquet and J. C. Thouvenel. Proc. Acad. Sci. Ser. D 296:575, 1983. (2) C. Fauquet et al. Develop. Appl. Biol. 2:71, 1988. (3) D. Louvel and J.-M. Bidaux. Agronomie Tropicale 32:257, 1977. (4) I. Lozano and F. Morales. Eur. J. Plant Pathol. 124:673, 2009.

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Bambara groundnut (Vigna subterranea) is an African legume with a great nutritional, economic and social potential. However, one of the main constraints to this crop is viral diseases which reduced yields. Indeed, approximately 12 viruses have been reported to infect bambara groundnut. Among these, only four were reported from Burkina Faso, namely, cowpea aphid-borne mosaic virus (CABMV), bean common mosaic virus strain-blackeye cowpea mosaic (BCMV-BlCM), peanut mottle virus (PeMoV), and cowpea mottle virus (CPMoV). This study was carried out in order to identify and characterize the main viruses occurring in bambara groundnut from Burkina Faso using serological and molecular tests. 140 plants were sampled in the three agro-climatic zones of Burkina Faso. Both Potyvirus CABMV and BCMV-BlCM were identified in 8.57% of the samples when double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) test was used and 14.29% of the samples when reverse transcription-polymerase chain reaction (RT-PCR) test was used. Phylogenetic tree based on 476 nt in coat protein showed that all Burkina Faso CABMV isolates clustered together with Uganda isolate (KT726938). However, two groups were distinguished within these isolates. Burkina Faso BCMVBlCM isolates are strengthly clustered with BCMV and BlCMV group. This study reports the first molecular characterization of CABMV and BCMV-BlCM infecting Bambara groundnut in Burkina Faso.

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