Histopathological effects of Bacillus thuringiensis on the alimentary canal of the sheep louse, Bovicola ovis

• Published in: Journal of invertebrate pathology Vol. 72; no. 1; pp. 9 - 20
• Main Authors: Hill, C.A. (University of Adelaide, Glen Osmond, SA, Australia.), Pinnock, D.E
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.07.1998
• Subjects: Adenosine - analogs & derivatives; Adenosine - analysis; Animals; BACILLUS THURINGIENSIS; Bacillus thuringiensis - chemistry; Bacillus thuringiensis - physiology; Bacillus thuringiensis - ultrastructure; BACILLUS THURINGIENSIS SUBSP. KURSTAKI; Biological and medical sciences; Biological Assay; BOVICOLA BOVIS; Bovicola ovis; CELL MEMBRANES; Chromatography, High Pressure Liquid; CRYSTAL PROTEINS; CYTOTOXICITY; Digestive System; ENDOTOXINAS; ENDOTOXINE; ENDOTOXINS; Female; Fundamental and applied biological sciences. Psychology; HISTOPATHOLOGIE; HISTOPATHOLOGY; HISTOPATOLOGIA; INTESTIN; INTESTINES; INTESTINOS; Male; Medically important nuisances and vectors, pests of stored products and materials: population survey and control; MEMBRANA MUCOSA; MEMBRANAS CELULARES; MEMBRANE CELLULAIRE; MICROVILLI; MIDGUT; MODE OF ACTION; MUCOUS MEMBRANE; MUQUEUSE; Nuisances; Phosphatidylcholines - analysis; Phthiraptera - microbiology; Phthiraptera - ultrastructure; PROTEINAS; PROTEINE; PROTEINS; Sheep - parasitology; Sugar Acids - analysis; TOXICIDAD; TOXICITE; TOXICITY; Trichodectidae; Mallophaga; Nuisance; Midgut; Toxicity; Insecta; Biological control; Bacillus thuringiensis; Mortality; Bacillaceae; Phthiraptera; Histopathology; Microbiological control; Transmission electron microscopy; Bacillales; Bovicolidae; Ultrastructure; Arthropoda; Bacteria; Epithelial cell; Livestock; Ectoparasite; Invertebrata; Microbial insecticide
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1006/jipa.1998.4761

Sequential observations were made of the ultrastructural effects of Bacillus thuringiensis (Bt) subsp. kurstaki strain WB3S16 on midgut epithelial cells of the sheep biting louse, Bovicola ovis, after the lice were fed, ad libitum, a powdered preparation of Bt spores, delta-endotoxin crystals, and lysed cellular components. Light microscope observations revealed cytopathological changes to the midgut epithelial cells 4 h postfeeding. Transmission electron micrographs showed that the microvilli of the midgut epithelial cells became disrupted 4-8 h postfeeding, after which the cells became vacuolated and swollen, and the cell organelles lost definition and disappeared. Paralysis and death of B. ovis occurred between 8 and 12 h postfeeding, coincident with midgut cells lysis and release of cellular contents into the midgut lumen. The histopathological effects reported here are similar to those reported in lepidopteran and coleopteran larvae affected by the delta-endotoxin crystal proteins. The constituent fractions of the Bt preparation were tested for toxicity to B. ovis using a feeding bioassay. Native delta-endotoxin crystals were not toxic to B. ovis and remained intact in the midgut of the insect. There was no evidence that the native Bt crystal was involved in the cytopathology and death of the lice. However, in vitro solubilized delta-endotoxin crystal proteins were significantly toxic to B. ovis. In addition, a louse active toxin was associated with the Bt membranes and culture supernatant