Introduction to Epidemiology 6th Edition by Ray M Merrill

Exercise 21

What is different about those who develop cholera compared with those who do not?

Step 1 of 2

Louis Pasteur was able to grow bacterium culture in vitro that causes fowl cholera. He deliberately injected this culture into the fowl stock to check whether they developed cholera from this or not. The fowl as expected did develop cholera and died. Since, he ran out of the fowl stock, he administered the same culture to those who survived the primary exposure to the bacteria. To his surprise these fowl did not develop any disease and they survived. When he administered the bacterial culture after two months to the fresh stock of fowl, the fowl did not die.

This indicates that attenuation (loss of strength) has been achieved in the bacteria as they grew old. Also, those fowls which have survived earlier exposed to bacterial culture did not develop disease after secondary exposure.