The importance of agricultural knowledge systems (AKS) especially in rural communities cannot be overemphasized. AKS are important for creation, sharing and enhancing access and usage of agricultural knowledge. They link agricultural research and farms; increase adoption of good agricultural practices; improve the performance of agricultural marketing systems; and enhance effective post-harvest management. Despite the importance of agriculture to the economy and livelihoods of majority of Tanzanians, there is a consensus from scholars that the sector has been performing poorly. This is partially due to limited access to agricultural knowledge resulting into irrational decisions on agricultural activities thus dwarfing the sector. The modified Knowledge Management Processes Model guided the study in investigating how AKS can be strengthened to enhance access and usage of agricultural knowledge among stakeholders. The study adopted a pragmatic paradigm and used mixed method research by applying a survey, key informant interviews, focus group discussions (FGDs) and document reviews. Structured questionnaires were administered to 314 farmers while key informant interviews involved 57 respondents among village executives, councillors, input-suppliers, information providers, buyers, agricultural extension officers and researchers. Moreover, three FGDs involving 24 farmers were conducted. Qualitative data were analysed through classical content and constant comparison analysis, while SPSS software was used to analyse quantitative data. Quantitative and qualitative data were mixed during analysis, interpretation and discussion of results. The study identified farmers, the private sector and the government as major actors, but not working in unison. Most actors used human based systems while few used ICT and paper based systems. Actors needed agricultural knowledge on weather, farm preparation, seeds, crop maintenance, post-harvest practices, agricultural marketing and credits. Most actors shared agricultural knowledge through face-to-face interactions and mobile phones, few through internet. It was concluded that poor linkage among actors limited accessibility of agricultural knowledge. To improve accessibility to agricultural knowledge, a model for strengthening AKS usage is proposed. It is recommended that actors should be linked together and involved in enhancing access and usage of agricultural knowledge. Moreover, the proposed model should be validated before applying it. / Information Science / D. Litt. et Phil (Information Science)

Background: Parasite evolution is hypothesized to select for levels of parasite virulence that maximise transmission success. When host population densities fluctuate, low levels of virulence with limited impact on the host are expected, as this should increase the likelihood of surviving periods of low host density. We examined the effects of Morogoro arenavirus on the survival and recapture probability of multimammate mice (Mastomys natalensis) using a seven-year capture-mark-recapture time series. Mastomys natalensis is the natural host of Morogoro virus and is known for its strong seasonal density fluctuations. Results: Antibody presence was negatively correlated with survival probability (effect size: 5-8% per month depending on season) but positively with recapture probability (effect size: 8%). Conclusions: The small negative correlation between host survival probability and antibody presence suggests that either the virus has a negative effect on host condition, or that hosts with lower survival probability are more likely to obtain Morogoro virus infection, for example due to particular behavioural or immunological traits. The latter hypothesis is supported by the positive correlation between antibody status and recapture probability which suggests that risky behaviour might increase the probability of becoming infected.

Background: In order to optimize net transmission success, parasites are hypothesized to evolve towards causing minimal damage to their reservoir host while obtaining high shedding rates. For many parasite species however this paradigm has not been tested, and conflicting results have been found regarding the effect of arenaviruses on their rodent host species. The rodent Mastomys natalensis is the natural reservoir host of several arenaviruses, including Lassa virus that is known to cause Lassa haemorrhagic fever in humans. Here, we examined the effect of three arenaviruses (Gairo, Morogoro and Lassa virus) on four parameters of wild-caught Mastomys natalensis: body mass, head-body length, sexual maturity and fertility. After correcting for the effect of age, we compared these parameters between arenavirus-positive (arenavirus RNA or antibody) and negative animals using data from different field studies in Guinea (Lassa virus) and Tanzania (Morogoro and Gairo viruses). Results: Although the sample sizes of our studies (1297, 749 and 259 animals respectively) were large enough to statistically detect small differences in body conditions, we did not observe any adverse effects of these viruses on Mastomys natalensis. We did find that sexual maturity was significantly positively related with Lassa virus antibody presence until a certain age, and with Gairo virus antibody presence in general. Gairo virus antibody-positive animals were also significantly heavier and larger than antibody-free animals. Conclusion: Together, these results suggest that the pathogenicity of arenaviruses is not severe in M. natalensis, which is likely to be an adaptation of these viruses to optimize transmission success. They also suggest that sexual behaviour might increase the probability of M. natalensis to become infected with arenaviruses.

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