The Etiology of Flacherie, One of the Great Scourges of Sericulture

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The focus of this article is to trace the history of the etiology of flacherie from the middle nineteenth century to the decade of the 1960s. In 1867, Louis Pasteur ascribed the pestilential epizootics among silkworms to two symptomatically different diseases, pebrine and flacherie. Identification of several bacteria and viruses as the pathogens of flacherie has led to the modern concept of flacherie as follows: a complex of silkworm diseases that differ in etiology but share the common sign of flaccid condition. The conceptual innovation entailed fundamental changes in the approaches to nosology and diagnosis. The viral pathogens have greater potential than the bacterial ones for catastrophic losses in sericulture because they are obligate parasites, highly virulent and persist in the sericultural environment long enough to allow year-to-year infection cycle. Until the end of the nineteenth century, scientific research on flacherie was conducted almost entirely in Europe. At the turn of the century, however, Europe was slowly being overtaken by Japan as a leading center of flacherie research.