After researching bacteriological agents for my novel, I considered myself something of an expert. Little did I know that my partner had first hand experience ...
Cole's early life was spent on a farm in Australia's Snowy Mountains where the battle to eradicate rabbits was carried out using the same toxic gas mixture used in the trenches in World War 1. The mere killing of rabits was not the aim, there was a need to permanently effect the species, to permanently affect populations in sufficient numbers to cause permanent decline. Rabbits need homes to breed and survive predators, and so fumigation of rabbit warrens was carried out. A toxic gas mixture was blown throughout the warren system (pressure fumigation).
Both my partner and his father were frequently overcome by fumes and were fortunate not to have died. It should be noted that fumigants are dangerous to both the aggressor and the victim.