PATTERNS OF CHANGE IN VECTOR-BORNE DISEASES

The statuses of vector-borne diseases have changed over recent years. How a few such diseases have changed and the primary causes of change (urbanization, increased conflict, changes in water-resource managemen t, ecological and environmental change, and reduced health service res ourcing) are the subjects of the present review. The key impacts which these primary causes have on selected vectors and the infections they transmit are tabulated. The success of vector-control programmes agai nst onchocerciasis and Chagas disease is discussed, and the methods us ed to evaluate the epidemiological impact of such controls are describ ed. Bednet programmes for control of malaria are recognized as a poten tial future means of reducing morbidity and mortality in children. In contrast to the success achieved in limiting Simulium and Triatoma pop ulations through vertical programmes, control of tsetse, whilst succes sful in Uganda, has not been utilized to stem recent epidemics of slee ping sickness in resource-stressed settings in Central Africa. Vector- borne diseases mill continue to be a problem because of the adaptabili ty of vectors, the potential problems of managing effective vector con trols within decentralized health systems, and the influence of activi ties outside the health sector itself. Changes beyond the health secto r can increase the problem posed by a vector and increase the frequenc y of transmission.