B. sphaericus toxin is effective against larvae of Culex and Psorophora, and its effect is variable to Anopheles depending on the species and is less active on Aedes larvae. Like Culex, Aedes larvae ingest the toxin, 42 kDa protein, and process to the more diminutive form. However, it has been observed that fluorescent-labeled toxin binds to midgut epithelial cells of Culex larvae with high specificity, poorly to Anopheles cells, and not to those of Ae. aegypti or Ae. triseriatus. Pathological changes in the larvae following toxin ingestion essentially involve the midgut cells. Large vacuoles or cytolysosomes appear in the posterior midgut cells, accompanied by general gut swelling. Eventually, these cells separate from one another and slough from the basement membrane, leading to the death of the larvae. In cultured cells, the mitochondrial cristae and endoplasmic reticulum rapidly swelled within 5 m of treatment [5]. The problem with B. sphaericus is the fast development of mosquito resistance, limiting its use in operational programmes.
Author(s) Details:
B. Usharani,
Department of Biomedical Genetics, Institute of Basic Medical Sciences, University of Madras, Tamil Nadu, India.
R. Venkateswari,
Department of Medical Microbiology, Institute of Basic Medical Sciences, University of Madras, Tamil Nadu, India.
P. Suganthi,
Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Madras, Tamil Nadu, India.
M. Muthuraj,
State TB Training and Demonstration Centre, Intermediate Reference Laboratory, Government Hospital for Chest Diseases, Puducherry, India.
