Field evaluation of selected cassava genotypes for cassava brown streak disease based on symptom expression and virus load

Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread.Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread.Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread.Background Production of cassava (Manihot esculenta Crantz), a food security crop in sub-Saharan Africa, is threatened by the spread of cassava brown streak disease (CBSD) which manifests in part as a corky necrosis in the storage root. It is caused by either of two virus species, Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV), resulting in up to 100% yield loss in susceptible varieties. Methods This study characterized the response of 11 cassava varieties according to CBSD symptom expression and relative CBSV and UCBSV load in a field trial in Uganda. Relative viral load was measured using quantitative RT-PCR using COX as an internal housekeeping gene. Results A complex situation was revealed with indications of different resistance mechanisms that restrict virus accumulation and symptom expression. Four response categories were defined. Symptom expression was not always positively correlated with virus load. Substantially different levels of the virus species were found in many genotypes suggesting either resistance to one virus species or the other, or some form of interaction, antagonism or competition between virus species. Conclusions A substantial amount of research still needs to be undertaken to fully understand the mechanism and genetic bases of resistance. This information will be useful in informing breeding strategies and restricting virus spread

Identification of F1 cassava (Manihot esculenta Crantz) progeny using microsatellite markers and capillary electrophoresis

Generation of genetic diversity is necessary in improving on the potential of cassava when faced with various biotic and abiotic challenges. Presently, cassava breeders are breeding for a number of traits, such as drought tolerance, early root bulking, yield, starch, beta-carotene, protein, dry matter, pest and disease resistance, by relying on genetic diversity that exists in manihot esculenta germplasm. Controlled pollination is one of the main methods used to generate genetic diversity in cassava. However, the process of controlled pollination especially in an open field is prone to contamination by illegitimate pollen right from the time of pollination, seed collection, nursery bed establishment to planting of the trials. Therefore, authentication of the progeny obtained from cas-sava crosses is very important for genetic studies. Twelve informative microsatellite markers were used to verify the authenticity of 364 F1 progeny thought to come from four controlled parental crosses. The transmission of each allele at nine microsatellite loci was tracked from parents to progeny in each of the four Namikonga-derived F1 cassava families. Out of the 364 F1 progeny, 317 (87.1%) were true-to-type, 44 (12.1%) were a product of self-pollination and 3 (0.8%) were a product of open pollination. The consistency of the results obtained using microsatellite markers makes this technique a reliable tool for assessing the purity of progeny generated from cassava crosses

Quantifying and valuing community health worker time in improving access to malaria diagnosis and treatment

Background: Community health workers (CHWs) are members of a community who are chosen by their communities as first-line, volunteer health workers. The time they spend providing healthcare and the value of this time are often not evaluated. Our aim was to quantify the time CHWs spent on providing healthcare before and during the implementation of an integrated programme of diagnosis and treatment of febrile illness in three African countries. Methods: In Burkina Faso, Nigeria and Uganda, CHWs were trained to assess and manage febrile patients in keeping with Integrated Management of Childhood Illness recommendations to use rapid diagnostic tests, artemisinin-based combination therapy and rectal artesunate for malaria treatment. All CHWs provided healthcare only to young children usually under 5 years old, and hence daily time allocation of their time to child healthcare was documented for one day (in the high malaria season) before the intervention and at several time points following the implementation of the intervention. Time spent in providing child healthcare was valued in earnings of persons with similar experience. Results: During the high malaria season of the intervention, CHWs spent nearly 50 minutes more in daily healthcare provision (average daily time 30.2 minutes before the intervention versus 79.5 minutes during the intervention; test for difference in means p< 0.01). On average, the daily time spent providing healthcare during the intervention was 55.8 minutes (Burkina Faso), 77.4 minutes (Nigeria) and 72.2 minutes (Uganda). Using the country minimum monthly salary, CHWs time allocated to child healthcare for one year was valued at USD 52 in Burkina Faso, USD 295 in Nigeria and USD 141 in Uganda. Conclusion: CHWs spend up to an hour and a half daily on child healthcare in their communities. These data are informative in designing reward systems to motivate CHWs to continue providing good quality services

Quantifying and Valuing Community Health Worker Time in Improving Access to Malaria Diagnosis and Treatment

This work was supported by the UNICEF/UNDP/World Bank/WHO/Special Programme for Research & Training in Tropical Diseases, World Health Organization, Geneva, Switzerland (project ID number A80553 [Burkina Faso]; A80550 [Nigeria]; and A80556 [Uganda]) through funds made available by the European Commission (FP7) for research to improve community access to health interventions in Africa

Impact of Improving Community-Based Access to Malaria Diagnosis and Treatment on Household Costs

Financial support. This work was supported by UNICEF/UNDP/World Bank/WHO/Special Programme for Research & Training in Tropical Diseases, World Health Organization, Geneva, Switzerland (project ID numbers A80553; [;Burkina Faso], A80550; [;Nigeria], and A80556; [Uganda]) through funds made available by the European Commission (FP7) for research to improved community access to health interventions in Africa. Supplement sponsorship. This article appears as part of the supplement “Malaria in Highly Endemic Areas: Improving Control Through Diagnosis, Artemisinin Combination Therapy, and Rectal Artesunate Treatment,” sponsored by the World Health Organization

Impact of improving community-based access to malaria diagnosis and treatment on household costs

Background: Community health workers (CHWs) were trained in Burkina Faso, Nigeria and Uganda to diagnose febrile children using malaria rapid diagnostic tests (RDTs), treat positive malaria cases with artemisinin combination treatment (ACTs) and those who could not take oral medicines with rectal artesunate. We quantified the impact of this intervention on private household costs for childhood febrile illness. Methods: Households with recent febrile illness in a young child in previous two weeks were selected randomly before and during the intervention and data obtained on household costs for the illness episode. Household costs included consultation fees, registration costs, user fees, diagnosis, bed, drugs, food and transport costs. Private household costs per episode before and during the intervention were compared. The intervention’s impact on household costs per episode was calculated and projected to district-wide impacts on household costs. Results: Use of CHW increased from 35% of illness episodes before the intervention to 50% during the intervention (p<0.0001) and total household costs per episode decreased significantly in each country from 4.36 to 1.54 dollars in Burkina Faso, from 3.90 to 2.04 dollars in Nigeria and from 4.46 to 1.42 in dollars Uganda (all p<0.0001). There was no difference in the time used by the child’s caregiver to care for a sick child (59% before intervention vs. 51% during intervention spent 2 days or less). Using the most recent population figures for each study district, we estimate that the intervention could save households a total of 29,965, 254,268 and 303,467 dollars, respectively in the study districts in Burkina Faso, Nigeria and Uganda. Conclusions: Improving access to malaria diagnostics and treatments in malaria endemic areas substantially reduces private household costs. The key challenge is to develop and strengthen community human resources to deliver the intervention, and ensure adequate supplies of commodities and supervision. We demonstrate feasibility and benefit to populations living in difficult circumstances

Impact of improving community-based access to malaria diagnosis and treatment on household costs

Background: Community health workers (CHWs) were trained in Burkina Faso, Nigeria and Uganda to diagnose febrile children using malaria rapid diagnostic tests (RDTs), treat positive malaria cases with artemisinin combination treatment (ACTs) and those who could not take oral medicines with rectal artesunate. We quantified the impact of this intervention on private household costs for childhood febrile illness. Methods: Households with recent febrile illness in a young child in previous two weeks were selected randomly before and during the intervention and data obtained on household costs for the illness episode. Household costs included consultation fees, registration costs, user fees, diagnosis, bed, drugs, food and transport costs. Private household costs per episode before and during the intervention were compared. The intervention’s impact on household costs per episode was calculated and projected to district-wide impacts on household costs. Results: Use of CHW increased from 35% of illness episodes before the intervention to 50% during the intervention (p<0.0001) and total household costs per episode decreased significantly in each country from 4.36 to 1.54 dollars in Burkina Faso, from 3.90 to 2.04 dollars in Nigeria and from 4.46 to 1.42 in dollars Uganda (all p<0.0001). There was no difference in the time used by the child’s caregiver to care for a sick child (59% before intervention vs. 51% during intervention spent 2 days or less). Using the most recent population figures for each study district, we estimate that the intervention could save households a total of 29,965, 254,268 and 303,467 dollars, respectively in the study districts in Burkina Faso, Nigeria and Uganda. Conclusions: Improving access to malaria diagnostics and treatments in malaria endemic areas substantially reduces private household costs. The key challenge is to develop and strengthen community human resources to deliver the intervention, and ensure adequate supplies of commodities and supervision. We demonstrate feasibility and benefit to populations living in difficult circumstances