Suchergebnisse

As part of a series of studies associated with the development of improved vaccines for heartwater (a tick-borne disease of ruminant livestock caused by Cowdria ruminantium), field surveys were carried out to assess losses associated with the disease and the costs associated with controlling it in the two main agro-ecological zones of Zimbabwe (lowveld and highveld) where heartwater is believed to be endemic and epidemic, respectively. In each zone, a cross-sectional study was performed in the main farming systems (smallholder (SH) and large-scale commercial (LSC) beef and dairy), followed by longitudinal studies in the same sectors to improve data accuracy for some parameters. Suspected heartwater-specific mortality in cattle was similar in all LSC sectors (p=0.72) accounting for a median 1 percent mortality risk. Heartwater-specific mortality in SH areas was not assessed due to poor diagnostic ability of the farmers. Few LSC farms and Sh households kept sheep: suspected heartwater-specific mortality in LSC sheep was 0.8 percent in the lowveld and 2.4 percent in the highveld. Goats were a major enterprise in SH areas but not on LSC farms. Suspected heartwater mortality in LSC goats was 0.8 percent at one site in the highveld and 17.5 percent on a farm in the lowveld. Application of acaricides was the major control method for heartwater and other tick-borne diseases on both SH and LSC farms. On LSC farms, plunge dipping was used most frequently and the number of acaricide applications ranged widely between 3 and 52 per year. The total cost of acaricides per head per annum was higher in highveld dairies than in highveld and lowveld beef enterprises (p=0.03). In SH areas, cattle plunge dipping was conducted by the government with an average frequency of 8 (+ or -) (sd) immersions per annum in both the lowveld and highveld. The type of tick control on sheep and goats in all production systems was highly variable (ranging from none to hand removal or intensive acaricide treatment). Suspected heartwater cases on LSC farms were treated with tetracyclines; treatment was not reported in SH areas. Reported treatment costs were high (median Z$120) and highly variable (range Z$4-833). Vaccination against heartwater with the live, blood-based vaccine was reported on only one LSC farm. LSC farms applying acaricide 30 or more times per year reported higher morbidity (p<0.0001) and mortality (p<0.0001) than farms applying acaricides less than 30 times a year. This finding supports the use of reduced tick control in the management of heartwater in Zimbabwe.

Heartwater, caused by the rickettsial organism Cowdria ruminantium, is a serious constraint to livestock development in much of sub-Saharan Africa. Traditionally, the disease has been controlled by the use of chemical acaricides to control the vector tick. The University of Florida/USAID-supported heartwater research project (based in Zimbabwe) is developing a new inactivated vaccine to control the disease. In order that the vaccine is used effectively, the project has been studying the epidemiology of the disease in different livestock production systems of Zimbabwe, and evaluating the economic impact of the disease and of its future control using a vaccine such as the one under development. Initially, field studies were conducted to characterise the communal and commercial livestock-productions systems at risk from heartwater and to understand the epidemiology of the disease. The data from these studies were then applied to an infection-dynamics model of heartwater which was used to provide estimates of disease incidence and impact under various scenarios over a period of 10 yr. Two principal outputs of the epidemiological model (cumulative annual heartwater incidence and infection-fatality proportion) were key inputs into an economics model. The estimated total annual national losses amount to Z$ 61.3 million (US$ 5.6 million) in discounted value terms over 10 yr. Annual economic losses per animal in the commercial production system (Z$ 56 discounted values) are 25 times greater than the losses in the communal system (Z$ 2.2). The greatest component of economic loss is acaricide cost (76 percent), followed by milk loss (18 percent) and treatment cost (5 percent). Losses in outputs other than milk (beef traction and manure) appear to be minimal. A new vaccine has the promise of a benefit: cost ratio of about 2.4: 1 in the communal and 7.6 : 1 in the commercial system. A control strategy based on a new vaccine would yield additional non-financial benefits to farmers and the government resulting from reductions in the use of chemical acaricides.

The world's climate is continuing to change at rates that are projected to be unprecedented in recent human history. Some models are now indicating that the temperature increases to 2100 may be larger than previously estimated in 2001. The impacts of climate change are likely to be considerable in tropical regions. Developing countries are generally considered more vulnerable to the effects of climate change than more developed countries, largely attributed to a low capacity to adapt in the developing world. Of the developing countries, many in Africa are seen as being the most vulnerable to climate variability and change. High levels of vulnerability and low adaptive capacity in the developing world have been linked to factors such as a high reliance on natural resources, limited ability to adapt financially and institutionally, low per capita GDP and high poverty, and a lack of safety nets. The challenges for development are considerable, not least because the impacts are complex and highly uncertain. The overall aims of DFID's new research programme on climate change and development in sub-Saharan Africa are to improve the ability of poor people to be more resilient to current climate variability as well as to the risks associated with longer-term climate change. The programme is designed to address the knowledge implications of interacting and multiple stresses, such as HIV/AIDS and climate change, on the vulnerability of the poor, and it will concentrate on approaches that work where government structures are weak. To help identify where to locate specific research activities and where to put in place uptake pathways for research outputs, information is required that relates projected climate change with vulnerability data. ILRI undertook some exploratory vulnerability mapping for the continent in late 2005 and early 2006, building on some livestock poverty mapping work carried out in 2002. The work described here is a small piece of a larger activity that involved the commissioning of several studies on ...