Epidemiology of Surra: Unanswered Questions

抄録

Trypanosoma evansi occurs in a variety of ecological regions in both the Old and the New World and although it affects many different domesticated livestock species, there is a dearth of information on its distribution, prevalence and/or incidence and economic significance throughout its geographical range. Although reproductive wastage has been identified occasionally as a source of economic loss, the impact of T. evansi on productivity is recognized usually only when epidemic outbreaks of disease cause widespread loss. The possibility that economically significant production losses might occur also when less acute forms of disease exist has not been considered. The absence of accurate information distorts the overall picture: only outbreaks of disease with a high mortality tend to be quoted in discussions of the effects of surra. Deficiencies in our knowledge of the epidemiology of T. evansi contribute to this situation. These shortfalls include our knowledge and understanding of the natural history of the disease, the absence of any strategies for effective monitoring and surveillance, and the inability to design and implement cost-effective, appropriate strategies for control of the disease. Furthermore, the inadequate data on the effects of T. evansi infection on milk and meat production, draught power, or reproductive efficiency tend to diminish its importance as a disease, and has a negative influence on the attitude of national government and international funding organizations to implement measures to control the disease or to undertake research. Until it is possible to put in place reliable methods for identifying infected animals, estimating morbidity and assessing the economic impact of surra, this situation will continue to prevail.