REVIEW A proposal for the classification of biological weapons sensu lato Lajos Rozsa Received: 19 May 2014 / Accepted: 18 June 2014 Ó Springer-Verlag Berlin Heidelberg 2014 Abstract Due to historical and legislation reasons, the category of bioweapons is rather poorly defined. Authors often disagree on involving or excluding agents like hor- mones, psychochemicals, certain plants and animals (such as weeds or pests) or synthetic organisms. Applying a wide definition apparently threatens by eroding the regime of international legislation, while narrow definitions abandon several important issues. Therefore, I propose a category of ‘biological weapons sensu lato’ (BWsl) that is defined here as any tool of human aggression whose acting principle is based on disciplines of biology including particularly microbiol- ogy, epidemiology, medical biology, physiology, psychol- ogy, pharmacology and ecology, but excluding those based on inorganic agents. Synthetically produced equivalents (not necessarily exact copies) and mock weapons are also inclu- ded. This definition does not involve any claim to subject all these weapons to international legislation but serves a purely scholarly purpose. BWsl may be properly categorized on the base of the magnitude of the human population potentially targeted (4 levels: individuals, towns, countries, global) and the biological nature of the weapons’ intended effects (4 levels: agricultural-ecological agents, and non-pathogenic, pathogenic, or lethal agents against humans). Keywords Biological weapons Á Ecological weapons Á Psychochemical weapons Á Definition Á Typology Á Classification Historical constraints of defining biological weapons Origins The history of using pathogens as weapons may well go back to prehistoric or even pre-human ages (Ro ´zsa 2000, 2009). However, the first legal concept of microbial weapons emerged only after WWI when some neutral nations realized that the German embassies in their capitals had been housing mysterious microbiological labs in their buildings during the Great War (Wheelis 1998). Realizing that these labs might had served a hostile role, the League of Nations (1925) proposed a treaty that was signed by most contemporary powers to prohibit the first use of ‘Bacteriological Methods of Warfare’. Although viruses had been discovered long before, the brief text did not refer to viruses or virology. Neverthe- less, the prohibition of ‘bacteriological methods’ was usually meant to prohibit the use of all contagious microbial patho- gens, whatever their taxonomical positions were, namely viruses, viroids, prions (though the latter two were discov- ered much later), bacteria, Rickettsiae (that were later iden- tified as a subgroup of bacteria), and even eukaryotic microbes like pathogenic protists and fungi. Thus, instead of ‘bacteriological weapons’, the term ‘biological weapons’ came into use as a more appropriate synonym and it was typically meant to be as ‘pathogenic microbe weapons’. The involvement of toxins Interestingly, several pathogenic bacteria, including high- priority biowarfare agents such as Bacillus anthracis, Vibrio cholerae, Shigella dysenteria among others, actually harm the infected human body by excreting toxins into it. From a purely technical point of view, targeting the enemy either by a purified version of such toxins or by the bacteria that will L. Rozsa (&) MTA-ELTE-MTM Ecology Research Group, Pazmany Str. 1/C, Budapest 1117, Hungary e-mail: lajos.rozsa@gmail.com L. Rozsa Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, Hungary 123 Theory Biosci. DOI 10.1007/s12064-014-0204-0