Relationships of Birds and Arboviruses

SEVERAL epidemics of disease in man have recently attracted wide public attention due to their spectacular characteristics, of particular interest here being the involvement of birds. Ornithologists have been bombarded with questions and have lacked answers. This paper reviews the relationships of birds and arboviruses, illustrates the impact of epidemics of arbovirus disease on human communities, and outlines some ornithological information needed by virologists and epidemiologists. The term arboviruses refers to viruses that infect hemophagous arthropods when they ingest infected vertebrate blood. The viruses multiply in the tissues of the arthropod and are transmitted by bite to susceptible vertebrates. About 150 different arboviruses are now recognized and they occur in practically all regions of the world. About 50 are known to produce disease in man or domestic animals, and 8 of these have been isolated from wild birds. These latter are eastern (EE), western (WE), St. Louis (SLE), and Japanese B (JBE) encephalitis viruses; West Nile, Sindbis, and Ilheus viruses; and at least one member of the Russian tick-borne complex of viruses. Undoubtedly other arboviruses will be discovered; the geographic distribution of those now known may be much greater than recognized, and knowledge of the ecology of most of them is too incomplete to assess adequately their host ranges or their importance in causing disease (Scherer, 1963; Hammon, 1961-62; Work, 1963). The following summarizes information available on the relationships of birds and those arboviruses known to produce disease in man.