The E23 munition was a cardboard sub-munition developed by the United States biological weapons program for use as an anti-crop weapon. The E23 underwent a conversion for use as a vector weapon and was briefly used in large-scale entomological warfare trial but technical issues forced it from the tests.
The E23 munition was originally conceived as an anti-crop weapon.[1] When, following the Korean War, U.S. interest in large-scale entomological warfare increased, the E23 was one of two munitions involved in field testing the potential of insect vectors as weapons.[2]
The E23 was made of cardboard and had a diameter of 9.75 inches (24.8 cm) and a length of 18 inches (46 cm).[1] Essentially a cardboard container, the E23 consisted of an internal actuator which simply reversed a plastic bag, expelling its contents.[1] The E23 sub-munition also included a small parachute for use when dropped from the E77 cluster bomb.[1] The weapon was deployed between 2,000 and 1,000 feet in altitude after its release from the cluster bomb.[1] Once converted for use as a vector weapon the E23 could hold 200,000 rat fleas in its interior among small pieces of sponge.[1]
Initially, the E23 was involved in "Operation Big Itch".[1] In September 1954 Big Itch aimed to determine coverage patterns and survivability of uninfected tropical rat fleas (Xenopsylla cheopis) for use in biological warfare as disease vector.[3][4] In preliminary Big Itch tests approximately half of the E23 munitions failed to properly function.[1] In one instance, the problems with the E23 led uninfected fleas to escape into the aircraft where they bit the pilot, bombardier and an observer.[2] These problems led to the E23 being pulled off of Operation Big Itch.[1] Despite the problems with the E23, the Big Itch field trials ultimately proved successful.[4]