Pathogenesis and midgut histopathology of Bacillus thuringiensis in Simulium vittatum (Diptera: Simuliidae) |
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Authors: | Lawrence A Lacey Brian A Federici |
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Institution: | Divisão de Cien?ias Medicas, INPA, Caixa Postal 478, Mannaus, Amazonas, Brazil 69.000;Division of Biological Control, University of California, Riverside, California 92521 USA |
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Abstract: | The pathogenesis and midgut histopathology which resulted when larvae of the blackfly, Simulium vittatum, were exposed to Bacillus thuringiensis at various temperatures and periods of exposure were investigated. The onset of mortality was studied at 10°, 15°, 19°, and 24°C. For each 4–5°C increase in temperature above 15°C, the onset of mortality was shortened by 24 hr. Exposures as brief as 15 min to 10 ppm of a whole spore preparation resulted in an average mortality of 29% in late-instar larvae. Mortality increased sharply for exposures up to 3 hr, approaching a maximum of 80%.The gross signs of disease included cessation of feeding and tetany with brachytosis. The tissue most affected was the midgut epithelium in the regions of the gastric caeca and posterior stomach. The formation of cytoplasmic vacuoles followed by cell lysis and/or sloughing were very apparent in moribund larvae. Death resulted without bacteremia. |
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Keywords: | Send reprint requests to B A Federici |
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