BackgroundWest Nile fever virus is a zoonotic arboviral infection maintained in a sylvatic cycle involving mosquito vectors and birds. It is one the arboviruses whose geographical range is expanding because of climate and land use changes that enhance the densities of mosquitoes and promote mosquito-bird-human interactions. We carried out a survey to determine the reservoirs of WNV among wild birds in Tana River and Garissa counties, Kenya.MethodsBlood samples were obtained from 361 randomly trapped wild birds. Using real-time polymerase chain reaction (PCR), all samples were screened for WNV using gene specific primer sets amplifying a portion of the E region of the genome encoding the envelope protein.ResultsSixty five (65) out of 361 birds screened tested positive for WNV on real-time PCR assay. Sequencing of the selected positive samples reveals that the isolated WNV were most closely related to strains isolated from China (2011). A regression analysis indicated that sampling location influenced the occurrence of WNV while species, age, weight and sex of the birds did not have any effect.ConclusionsThis study provides baseline information on the existing circulation of WNV in this region among wild bird reservoirs that could spill over to the human population and points to the need for implementation of surveillance programs to map the distribution of the virus among reservoirs. Awareness creation about West Nile fever in this region is important to improve its detection and management.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-2019-8) contains supplementary material, which is available to authorized users.

Mangrove forests are active carbon sinks and important for nutrient cycling in coastal ecosystems. Restoration of degraded mangrove habitats enhances return of ecosystem goods and services, including carbon sequestration. Our objective was to assess the restoration of primary productivity of reforested mangrove stands in comparison with natural reference stands in Gazi Bay, Kenya. Litter fall data were collected in nine Rhizophora mucronata and Sonneratia alba monospecific stands by use of litter traps over 2 years. Litter was emptied monthly, dried, sorted, and weighed. The reforested and natural stands showed seasonality patterns only in the production of reproductive material. Leaves constituted the highest percentage to total litter fall. Litter productivity rates for the R. mucronata stands were not significantly different and ranged from 6.61–10.15 to 8.36–11.02 t ha−1 yr−1 for the restored and natural stands, respectively. The productivity of 5 years R. mucronata stands reached 5.22 t ha−1 yr−1 and was significantly different from other stands. Litter productivity rates for S. alba stands was 7.77–7.85 for the restored stands and 10.15 t ha−1 yr−1 for the natural stand but differences were not significant. Our results indicate that plantations of at least 11 years have attained litter productivity rates comparable to the natural forests. This suggests that productivity of replanted mangroves is likely to reach complete recovery by this age under the prevailing environmental conditions.

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Ndirangu MD, Chira RM, Wang’ondu V, Kairo JG. 2018. Wave energy reduction and sediment stabilization by mangroves in Gazi Bay, Kenya. Biodiversitas 19: 83-94. Mangrove forests provide natural protection to the coast by attenuating wave energy and stabilizing sediments. The efficiency of coastal protection is likely to decline with increased degradation and losses of mangrove forests. Nevertheless, there are few empirical studies to test these hypotheses. The objective of the study was to investigate how wave energy and sediment stabilization vary with tree density in a monospecies stand of mangroves (Sonneratia alba) at Gazi Bay, Kenya. Seven belt transects were randomly selected along 900 m stretches of shoreline with homogenous emergent wave energy. Structural parameters, including; tree density, pneumatophores density, and basal areas were quantified using two quadrat measuring 25 m by 20 m along each transect. Three intertidal stations, each with five sampling points were sampled for wave energy using uniform plaster of Paris clod cards. Sediment stability was measured using improvised sinking metal disks made from bicycle spokes, and sediment accretion was monitored by Surface Elevation Tables (SETs). All transects showed significant difference in pneumatophores density (F (2.39) =25.15), tree density (F (2.33) =24.79), and basal area (F (2.39) = 29.66). The wave energy sampled by tree stems between stations and the correlation of wave energy reduction against tree density/ha, pneumatophores density, and basal areas per m2 also showed a significant difference. Regression analysis showed a significant difference in the sediment stability against tree density (R2 = 61%) and basal areas (R2 = 72.8%) while there was no significant difference between sediment stability and pneumatophores density (R2= 47%). Regression analysis between mean sediment accretion rates against all parameters were not significant. This study will help the managers and the government on the merit of using mangroves as bio-shields in protecting coastlines against erosion and stabilizing sediment in the wake of much anticipated global changing climate and sea-level rise.