The sero-epidemiology of Rift Valley fever in people in the Lake Victoria Basin of western Kenya

Rift Valley fever virus (RVFV) is a zoonotic arbovirus affecting livestock and people. This study was conducted in western Kenya where RVFV outbreaks have not previously been reported. The aims were to document the seroprevalence and risk factors for RVFV antibodies in a community-based sample from western Kenya and compare this with slaughterhouse workers in the same region who are considered a high-risk group for RVFV exposure. The study was conducted in western Kenya between July 2010 and November 2012. Individuals were recruited from randomly selected homesteads and a census of slaughterhouses. Structured questionnaire tools were used to collect information on demographic data, health, and risk factors for zoonotic disease exposure. Indirect ELISA on serum samples determined seropositivity to RVFV. Risk factor analysis for RVFV seropositivity was conducted using multi-level logistic regression. A total of 1861 individuals were sampled in 384 homesteads. The seroprevalence of RVFV in the community was 0.8% (95% CI 0.5–1.3). The variables significantly associated with RVFV seropositivity in the community were increasing age (OR 1.2; 95% CI 1.1–1.4, p<0.001), and slaughtering cattle at the homestead (OR 3.3; 95% CI 1.0–10.5, p = 0.047). A total of 553 slaughterhouse workers were sampled in 84 ruminant slaughterhouses. The seroprevalence of RVFV in slaughterhouse workers was 2.5% (95% CI 1.5–4.2). Being the slaughterman, the person who cuts the animal’s throat (OR 3.5; 95% CI 1.0–12.1, p = 0.047), was significantly associated with RVFV seropositivity. This study investigated and compared the epidemiology of RVFV between community members and slaughterhouse workers in western Kenya. The data demonstrate that slaughtering animals is a risk factor for RVFV seropositivity and that slaughterhouse workers are a high-risk group for RVFV seropositivity in this environment. These risk factors have been previously reported in other studies providing further evidence for RVFV circulation in western Kenya

Suitability of Modified Dilute Double Acid ÐMehlich 1 (0.1NHCL + 0.025NH2SO4) and Olsen (0.5MNaHCO3PH 8.5) Methods for Testing of Available Phosphorous for Kenyan Soils

A study was conducted to investigate the suitability of using modified Mehlich 1 and sodium bicarbonate Olsen methods for testing of available P for Kenyan soils. The soils were from 52 sites within the high and medium agricultural potential rainfall areas. Maize grain yields were used to calibrate the soil available P. The two P extraction methods were used at soil extracting ratio of 1:5. Regression analysis of maize grain yields (kg/ha) from plots with no fertilizer P application against extractable P by the two methods was done for the soil PH range: 4.0- 7.8, PH&#88045.5, 5.6&#8804PH £6.4 and 6.5 &#8804PH£ 7.8. Similar regression analysis was done for HB-600S and HB500S maize varieties and agro ecological zones (UM, LH, UH, LM and CL). Further regression was done taking into account of different prevailing agro-ecological zones. The results revealed that maize grain yields (kg/ha) were significantly (P&#88040.015) correlated (r= 0.335) to soil available P extractable by Olsen method and not modified dilute double acid Mehlich 1 method at soil PH range of 4.0-7.8. These results showed that available P can be estimated by the sodium bicarbonate method although the correlation was very small (r =0.335) but significant. The very small significant correlation implied need for further regression with more soil data. When regression analysis was done at soil PH &#88045.5 the correlations for both methods were not significant. This meant that both test methods were not suitable for estimating available P at this soil PH range and another suitable method should be found for soils within this PH range. At 5.6&#8804PH£ 6.4, both methods were significantly, (P&#88040.05) suitable with improved correlations (r = 0.488 and r= 0.490). This meant that at this soil PH range, both methods were suitable and can be used interchangeably although Olsen method gave lower values of available P than the double acid method. At 6.5&#8804PH £7.8, both methods were not significant and hence not suitable for estimating available P. When maize varieties HB 600 and HB 500 series were taken into account. It was found that both methods were significantly (P&#88040.05) suitable for estimating soil available P for planting maize HB 600 series. Only Olsen P method was significantly suitable (P&#8804 0.011) for estimating soil available P for planting maize HB 500 & 600 series. When agro ecological zones were taken into account, both methods were found significantly (P&#88040.05) suitable for estimating available P in LH zones only. It was concluded that Olsen method is significantly suitable for testing of available P at all soil PH range while modified Mehlich 1 method is not. The two methods are not suitable at PH&#8804 5.5 and another method must be found. At 5.6&#8804 PH&#8804 6.4, both methods can be used interchangeably. At 6.5&#8804PH&#88047.8 both methods are not suitable. This was attributed to over extraction by the modified dilute double acid and laboratory errors associated with Olsen method particularly on increase in pH of extracting solution when not kept in plastic containers. This leads to over extraction and hence poor correlation with crop yields. Olsen P method is suitable for estimating available P for planting maize HB 600 and HB 500 series. Both methods are not suitable for estimating available P in UM; LM and CL zones but are suitable in LH zones. In overall Olsen method appeared to be slightly suitable method for estimating available P in Kenyan soils and can be used interchangeably with modified Mehlich 1 at soil PH, 5.6&#8804 PH&#88046.4. However the small significant (p&#88040.015, r= 0.335) correlation meant more research was required to correlate other soil P testing methods for Kenyan soils. Keywords:Soil pH, P-testing, crop response and correlationsDiscovery and Innovation Vol. 19 (3) 2007: pp. 195-20

Payments for Ecosystem Services, Poverty and Sustainability: The Case of Agricultural Soil Carbon Sequestration

This chapter explores the potential impacts of payments for ecosystem services on poverty and sustainability of farm households, using the example of agricultural soil carbon sequestration. Economic analysis shows that there is a variety of technical and economic factors affecting adoption of practices that increase soil carbon and their impacts on poverty, hence, the net effect of these factors is an empirical question. The evidence suggests that carbon payments could have a positive impact on the sustainability of production systems while also raising incomes and reducing poverty. However, carbon contracts are found to have only modest impacts on poverty, even at relatively high carbon prices. Moreover, the participation of poor farmers in carbon contracts is likely to be constrained by the same economic and institutional factors that have inhibited their use of more productive, more sustainable practices in the first place. Thus, payments for ecosystem services are most likely to have a positive impact on poverty and sustainability when they are implemented in an enabling economic and institutional environmen