The mammalian safety of Bacillus thuringiensis-based insecticides

United States Environmental Protection Agency between the years 1961 and 19 95 registered 177 products containing viable Bacillus thuringiensis (Bt), N umerous laboratory studies have demonstrated that Bt and Bt products are no ninfectious and are toxic to mammals only at a dose greater than or equal t o 10(8) colony forming units (cfu) per mouse (a human equivalent based on t he weight of >10(11) cfu), In contrast, as few as three vegetative cells of Bacillus anthracis can kill mice (a human equivalent of >10(3) cfu), There are only two literature reports of Bt infection in man between the year 19 97 and the present, and all infected individuals had experienced either ext ensive burns or a blast injury, which predisposed them to infection. Two ep idemiology studies conducted during large-scale aerial Bt serovar kurstaki spray campaigns reported no increased incidence of illness, Some recent pap ers have expressed concern about the production of Bacillus cereus enteroto xins by Bt isolates, Laboratory studies found no evidence of illness in rat s and sheep fed Bt products, nor have epidemiology studies found increased incidence of diarrhea during Bt aerial spray campaigns, Increases in human antibody levels following exposure to Bt products have been reported but th ere was no increased incidence in asthma or other illness, Based on laborat ory studies and field experience, Bt insecticides have an excellent safety record.