The current pandemic of cassava mosaic virus disease in Uganda

Abstract

This chapter differs from many of the other contributions to this volume in that it deals with one specific disease. Cassava mosaic virus disease (CMD) justifies special treatment for several reasons: Cassava provides one of the main staple foods in many tropical areas and it is particularly important in many of the poorest countries of sub-Saharan Africa. CMD is the most important disease of cassava in Africa and also in Sri Lanka and southern India. The disease has a long history in Africa, where research has been in progress for many years. Indeed, CMD is likely to have received more attention than any other vector-borne disease of an African food crop. CMD is a prime example of a particularly important group of virus diseases of tropical, subtropical and temperate crops — those which have a dual strategy of dispersal in that they are disseminated in vegetative propagules and transmitted by an arthropod vector. A very damaging pandemic of CMD currently causes serious food shortages and affects the livelihood and well-being of rural communities in many parts of Uganda and threatens adjacent areas of Kenya and Tanzania. When attempts were made to control the pandemic, it became apparent that there was insufficient information to initiate effective management strategies and this led to increased research on CMD, not only in Uganda but elsewhere in Africa. The pandemic provides a striking example of the way in which the occurrence and control of a disease is closely associated with the vulnerability of the varieties being grown. Experience with CMD in Uganda has demonstrated the advantages of adopting an ecological approach in seeking to explain the main features of the current pandemic and its effects on the amount and type of cassava grown. Research on the disease and the viruses responsible has benefited greatly from collaboration between virologists in the tropics and those in developed countries of Europe and North America with access to sophisticated laboratory equipment.