Rats by Robert Sullivan is a fascinating study of rats and their cohabitation with humans. One particularly interesting section was on rats and plague, which, as you may know, is spread to humans by the rat flea. Apparently the Japanese were the first to experiment with the use of plague as a biological weapon during WWII under the direction of General Shiro Ishii. He discovered that the best was to infect a city with plague was to fill clay bombs with infected fleas. An attack was successfully conducted against the Chinese city of Changde. A clue that the outbreak was caused by humans rather than rats was that the rats began dying of plague weeks after the humans, a reverse of the normal situation.
General Ishii also practiced vivisection on live humans. He was never tried for war crimes, apparently having made a deal with the Americans who got copies of his notes and papers which formed the basis for the early American attempts at creating biological weapons. He retired a respected medical man.
The United States began experimenting with biological weapons in the early fifties and tested their weapon distribution methods on unsuspecting Americans. In one case, Navy planes sprayed the eastern Virginia coat with microbes similar to Anthrax but "thought to be harmless," and as late as 1966, soldiers dressed in civilian clothes dropped light bulbs filled with the microbes on the tracks in New York subways in order to measure how the microbes dispersed -- all without the knowledge of the public or Congress.