Prevalence and incidence of tick-borne diseases in smallholder farming systems in the western-Kenya highlands
Introduction
Tick-borne diseases (TBDs) are most prevalent and numerous and exert their greatest impact in the tropical and sub-tropical regions (Bram, 1983, Minjauw and Mcleod, 2003). Theileriosis alone was estimated to cause a loss of US$168 million in 11 African countries in 1989 (Mukhebi, 1992). Tick-borne diseases caused by Theileria parva, Anaplasma marginale and Babesia bovis are considered to be the most important constraints in the Kenya highlands (Norval et al., 1992, Peeler and Omore, 1997). Estimation of disease frequencies at population level can be used to compare different populations in order to express specific numbers relative to each population. Most of the past epidemiological evaluations of TBDs conducted in Kenya have been on passive data that cannot be extrapolated to other areas. The inadequacy of appropriate data leads to lack of quantification of economic losses from ticks and TBDs and their impacts on livestock productivity (Mukhebi, 1992, Pegram et al., 1989).
In the recent past, properly designed epidemiological studies were conducted in various parts of the country (Gitau, 1992, O’Callaghan, 1998, Maloo et al., 2001a, Maloo et al., 2001b) that gave dependable assessment of risk of TBDs in those areas. This type of studies had not been conducted in the western-Kenya highlands (Wilsmore, 1994). We undertook one as part of a broad study on the assessment of livestock productivity constraints in smallholder farming systems in the western-Kenya highlands (Okuthe, 1999, Okuthe et al., 2003).
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Study area
The study was conducted in Uasin Gishu district in the northern part of the Rift Valley province, Kenya. The district lies between 34°50′E and 35°03′E and 0°03′N and 0°55′N and is situated in a plateau ranging in altitude from 1900 to 2700 m, running approximately from Northwest to Southeast. Maximum temperatures range from 19 to 24 and minimum temperatures from 13 to 16 °C. The district has a highland-equatorial type of climate with a mean annual rainfall of 1124 mm which is a weakly bimodal
Herd structure, management practices and tick-borne diseases control
There were relatively more calves and adults in the RA than the PU area. This pattern was reversed in weaners (Table 1) that also give other descriptive statistics on cattle numbers. The cow: bull ratio was 25 and 53 for the RA and PU areas, respectively. The main type of grazing in the RA (73.4%) and PU (59.7%) areas was communal (Table 2).
The major tick control frequency, acaricide brand and tick control in the RA and PU areas was four times per month, TriatixR and hand spray. Detail of other
Discussion
Treatment of all TBDs during the study acted as an incentive for efficient reporting of disease cases. Hence the high quality of the data obtained in this study on TBDs incidence. The higher prevalence and incidence of TBDs in the peri-urban than the rural area could be attributed to three factors. The first factor was the relatively higher proportion of irregular tick control in the peri-urban compared to the rural area. The personnel who were responsible for the management of tick control
Conclusions
This study has shows that the incidence and prevalence of TBDs is high amongst resource poor smallholder dairy farming system in the western-Kenya highlands. This is the first epidemiological study that has quantified the risk of TBDs in the western-Kenya highlands using a longitudinal observational study. Other studies that include Gitau (1992) and Maloo (1993) only depicted that TBDs were the major causes of deaths in dairy cattle production systems in the central Kenya highlands and the
Acknowledgements
We acknowledge the Department for International Development (DFID) and Kenya Agricultural Research Institute (KARI) for the financial support. The Ministry of Agriculture Livestock Development and Marketing is also acknowledged for the co-operation and logistic support. We highly appreciate and feel indebted to the wonderful smallholder farmers in Uasin Gishu district for their co-operation and understanding during the study period.
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