Characterisation of the lymph node immune response following Mycoplasma mycoides subsp. Mycoides SC infection in cattle

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides biotype Small Colony (MmmSC), is still a major cattle disease in Africa. Development of long-term protective vaccines, the only relevant strategy to achieve CBPP eradication, requires the characterisation of the protective immune mechanism. To this aim, the present study investigated the cellular immune response persisting in the lymph nodes of cattle infected naturally and experimentally by contact, one year post exposure. The lymph node cell composition, MmmSC responsiveness and phenotype of the MmmSC-responding lymphocytes were compared between animals according to the different outcomes of the infection. To unravel the protective mechanism, the study focussed on the MmmSC-specific memory immune response generated in recovered cattle, known to develop long-term immunity and to be resistant to reinfection. An MmmSC-specific immune response, mediated by IFNgamma-secreting CD4 T-cells, was detected in the lymph nodes of all recovered cattle. Furthermore, the magnitude of this immune response was significantly higher in animals with complete recovery than in recovered animals presenting lung sequestra. The findings suggest that, in recovered cattle, a subset of MmmSC-primed IFNgamma-secreting CD4 T-cells homed to the regional lymph nodes as MmmSC-specific memory T-cells, likely responsible for the protective anamnestic response. Induction and expansion of this subset of MmmSC-specific CD4 memory T-cells might be a major goal to develop efficient long term protective vaccines against CBPP.     

Clinical, post mortem and virological findings after simultaneous inoculation of pigs with hog cholera and bovine viral diarrhoea virus.

The clinical course, post mortem lesions as well as virological and serological results after simultaneous intranasal inoculation of pigs with bovine viral diarrhoea virus (BVDV) and hog cholera virus (HCV) are described. Five groups of four weaners received constant doses of BVDV strain OSLOSS/2482 and tenfold decreasing doses of HCV strain ALFORT/187. Doses of 1,000 and 100 TCID50 of HCV in groups A and B of pigs led to fever and severe clinical signs in all animals of two groups, whereas at higher dilution of inoculum two, three or four animals survived without any clinical signs in the respective groups (C-E). Leucocyte samples taken from febrile animals and from normal pigs on five consecutive days were inoculated into both fetal calf kidney (FCK) and PK (15) cell cultures. Virus isolates were differentiated with BVDV and HCV specific monoclonal antibodies. HCV viraemia was detected in febrile animals exclusively, and BVDV viraemia occurred in not affected animals on days 3 to 7 post inoculation. Neutralizing antibodies (nab) against BVDV appeared before HCV nab in surviving animals of groups C and D after receiving low doses of HCV (10 or 1 TCID50). No BVDV nab were detected in group E that had received such a high dilution of HCV in addition to BVDV that theoretically no HCV was applied.     

Heterogeneity in farmers’ production decisions and its impact on soil nutrient use: Results and implications from northern Nigeria

Sustainable use (in terms of nutrients) of soil resources by farmers in Sub-Saharan Africa is constrained by institutions and markets. This paper explores the case of northern Nigeria, by using a combination of multi-attribute utility theory and bio-economic modelling. This approach allowed us to identify heterogeneity in production strategies and to quantify its effect on the use of soil nutrient resources.We find that farmers with larger land holdings place more emphasis on gross margins in their utility function, while those with larger holdings of fertile fadama fields place more emphasis on sustainability. Risk aversion, operationalised through variance minimization, appears an important attribute in the utility function of many farm households that are more dependent on agriculture for their overall income.A regression analysis shows that differences in production strategies significantly affect nutrient balances, but also shows that such effects are heterogeneous across locations. We find more favourable nutrient balances for some of the more market-oriented farm households who place more emphasis on sustainability. In farm plans of the most risk-averse households, the production of cereals for subsistence consumption dominates and leads to negative soil nutrient balances, especially for potassium.Farmers who place a large importance on gross margins are likely to benefit most from policies aimed at enhancing profitability through improving functioning of markets. The large group of risk-averse farmers will have the largest immediate gain in utility from policies and technologies aimed at reducing production risk in high-value crops. Additional policies aimed at creating a stronger market-oriented production by the least-endowed farm households could play a role in reducing intensity of soil fertility mining. Under these conditions, the efficient cropping pattern shifts partially from cereal cropping to high-value crops, associated with higher input use.The main results are similar to those in other studies, although some of the nutrient balances are less negative. The results do appear to be sensitive to the type of cropping activities included in the analysis, and additional methodological research is required. Extensions of the used method should further account for temporal and spatial differences in soil fertility, leading to differences in nutrient uptake and production, as well as potential temporal heterogeneity in production strategies.     

Farmers’ practices,utilization, conservation and marketing of Bambara groundnut (<Emphasis Type="Italic">Vigna subterranea</Emphasis> (L.) Verdc.) in Dosso Region,Western Niger

Bambara groundnut (Vigna subterranea (L.) Verdc.) is one of the important legume crop grown in marginal soils of sub-Saharan Africa. Despite its importance in food security and income generation for small scale farmers, it remains as a neglected and underutilized crop and the productivity is very low in the field due to the lack of improved varieties and lack adequate farming practices. Thus, the aim of this study is to investigate all aspects related to its production including source of seeds supply and farmers management practices, utilization, conservation and marketing. The results revealed that in this Region of Western Niger Bambara groundnut was mainly produced by female (95%) compared to male (5%). Farmers use their own recycled seed (80%) which is the main source followed by provision of recycled seeds by relatives (5%) and purchasing from the local market (15%). Also, this finding shows that there is a lack of adequate farming practices and the crop is mostly produced on inherited land without any inputs as reported by 80% of the respondents. Mono-cropping is mainly practiced by 97% of farmers while a few of them do rotation (2%) and most of pre and postharvest handling technologies are traditional. The most important traits preferred by Bambara farmers is seed colour (cream color), followed by high grain yield, early maturity and cooking ability according to the respondents with 98, 92, 88 and 72% respectively. Several features have to be taking into account in order to promote Bambara nut including its ability to do well in harsh conditions, its nutritional benefits, and its ability to fix nitrogen, thereby increasing soil fertility in mixed cropping systems.     

Valuation of Rice Postharvest Losses in Sub-Saharan Africa and Its Mitigation Strategies

正Data on rice harvest and postharvest loss in Sub-Sahara Africa(SSA) is scanty making it difficult for stakeholders to appreciate the loss and set priority areas for loss reduction along the value chain. To address this problem, a protocol was developed and validated for postharvest loss(PHL) quantification in SSA. Quantitative losses at each segment were determined by field measurements.     

SUSTAINABLE DEVELOPMENT OF CROP-LIVESTOCK FARMS IN AFRICA

Crop-livestock farms across Africa are highly variable due to in agroecological and socioeconomic factors, the latter shaping the demand and supply of livestock products. Crop-livestock farms in Africa in the 20-first century are very different from most mixed farms elsewhere in the world. African crop-livestock farms are smaller in size, have fewer livestock, lower productivity and less dependency on imported feed than farms in most countries of Europe, the Americas and the intensive agricultural systems of Asia. This paper discusses the role African crop-livestock farms have in the broader socio-agricultural economy, and how these are likely to change adapting to pressures brought on by the intensification of food systems. This intensification implies increasing land productivity (more food per hectare), often leading to more livestock heads per farm, producing fertilized feeds in croplands and importing feed supplements from the market. This discussion includes (1) the links between crop yields, soil fertility and crop-livestock integration, (2) the increasing demand for livestock products and the land resources required to meet to this demand, and (3) the opportunities to integrate broader societal goals into the development of crop-livestock farms. There is ample room for development of crop-livestock farms in Africa, and keeping integration as part of the development will help prevent many of the mistakes and environmental problems related to the intensification of livestock production observed elsewhere in the world. This development can integrate biodiversity, climate change adaptation and mitigation to the current goals of increasing productivity and food security. The inclusion of broader goals could help farmers access the level of finance required to implement changes.     

SNP genotyping defines complex gene-flow boundaries among African malaria vector mosquitoes

Mosquitoes in the Anopheles gambiae complex show rapid ecological and behavioral diversification, traits that promote malaria transmission and complicate vector control efforts. A high-density, genome-wide mosquito SNP-genotyping array allowed mapping of genomic differentiation between populations and species that exhibit varying levels of reproductive isolation. Regions near centromeres or within polymorphic inversions exhibited the greatest genetic divergence, but divergence was also observed elsewhere in the genomes. Signals of natural selection within populations were overrepresented among genomic regions that are differentiated between populations, implying that differentiation is often driven by population-specific selective events. Complex genomic differentiation among speciating vector mosquito populations implies that tools for genome-wide monitoring of population structure will prove useful for the advancement of malaria eradication.     

Stabilizing isopeptide bonds revealed in gram-positive bacterial pilus structure

Many bacterial pathogens have long, slender pili through which they adhere to host cells. The crystal structure of the major pilin subunit from the Gram-positive human pathogen Streptococcus pyogenes at 2.2 angstroms resolution reveals an extended structure comprising two all-beta domains. The molecules associate in columns through the crystal, with each carboxyl terminus adjacent to a conserved lysine of the next molecule. This lysine forms the isopeptide bonds that link the subunits in native pili, validating the relevance of the crystal assembly. Each subunit contains two lysine-asparagine isopeptide bonds generated by an intramolecular reaction, and we find evidence for similar isopeptide bonds in other cell surface proteins of Gram-positive bacteria. The present structure explains the strength and stability of such Gram-positive pili and could facilitate vaccine development.     

Crop production under different rainfall and management conditions in agroforestry parkland systems in Burkina Faso: observations and simulation with WaNuLCAS model

Traditional agroforestry parkland systems in Burkina Faso are under threat due to human pressure and climate variability and change, requiring a better understanding for planning of adaptation. Field experiments were conducted in three climatic zones to assess Sorghum bicolor (L.) Moench (Sorghum) biomass, grain yield and harvest index in parklands under different rainfall pattern and compared to simulations of sorghum biomass and grain yield with the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model for calibration and parametrisation. For planning adaptation, the model was then used to evaluate the effects of different management options under current and future climates on sorghum biomass and grain yield. Management options studied included tree densities, tree leaf pruning, mulching and changes in tree root patterns affecting hydraulic redistribution. The results revealed that sorghum biomass and grain yield was more negatively affected by Parkia biglobosa (Jacq.) Benth. (néré) compared to Vitellaria paradoxa C. F Gaertn (karité) and Adansonia digitata L. (baobab), the three main tree species of the agroforestry parkland system. Sorghum biomass and grain yield in different influence zones (sub-canopy, outside edge of canopy, open field) was affected by the amount of precipitation but also by tree canopy density, the latter depending itself on the ecological zone. The harvest index (grain as part of total biomass) was highest under the tree canopy and in the zone furthest from the tree, an effect that according to the model reflects relative absence of stress factors in the later part of the growing season. While simulating the effects of different management options under current and future climates still requires further empirical corroboration and model improvement, the options of tree canopy pruning to reduce shading while maintaining tree root functions probably is key to parkland adaptation to a changing climate.