Why did Robert Koch use animals in experiments on infectious diseases?

Robert Koch utilized animals in his experiments primarily to establish a definitive causal relationship between specific microorganisms and the diseases they produce, a framework now known as Koch’s postulates.12

By inoculating healthy animals with a suspected pathogen isolated in pure culture, Koch could observe whether the animal developed the same disease as the original host. If the disease was reproduced, he would then isolate the organism from the newly infected animal to confirm it was identical to the original causative agent.312

Beyond validating these postulates, Koch used animal models to study the progression of infections, observe differences in pathogenicity across various host species, and demonstrate that the animal body serves as an effective environment for the cultivation of bacteria. While animal experimentation is a standard practice in medical research, it is essential to uphold the ethical principle of minimizing harm and ensuring that such studies are conducted with the utmost necessity and care for animal welfare.2