Mammalian safety of microbial agents for vector control: a WHO memorandum.

This Memorandum outlines recommended safety tests for application to biological agents under consideration for widespread use for pest control. The basic principles utilized in developing these recommendations were that: (i) the hazards presented by microbial pesticides are inherently different from those associated with chemical pesticides and the tests used to determine hazard potential to man should reflect this; (ii) a high proportion of negative results is likely; (iii) tiered testing systems should be used; negative data obtained at any level would obviate the need for further testing; (iv) the primary tier testing protocols should be designed to expose test animals to the microbial agents under conditions that provide maximum opportunity for the expression of any adverse effects.Outlines of tests proposed for use with four groups of biological agents (bacteria, fungi, protozoa, and viruses) are given. The safety tests required at each level of development of a microbial agent are described.The present status of safety testing of the agents already under development for possible use in vector control is considered. It is concluded that, for Bacillus thuringiensis H-14 and B. sphaericus, a level of safety testing has been reached that permits their use in large-scale field trials.Suggestions for applied research are made, covering safety aspects of cottage-industry production of microbial agents, studies on allergic responses, serological surveys on laboratory workers, and the investigation of environmental persistence of newly developed agents.