Clostridial Disease in Calves The multi-factorial cluster death disease Clostridial diseases are caused by a variety of clostridium bacteria. These are spore-forming organisms that are naturally present in soil, bedding, and even in the gut. Spores can survive for years in the environment. Normally they're harmless however they turn deadly when the right trigger allows them to germinate and produce potent toxins. These toxins, not the bacteria themselves, are what damage tissue and kill calves.