This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
In cyclo-propagative transmission, the disease agent undergoes 
Select and explain. 
A. Only development, B. Only multiplication, C. Change in form and numbers, D. No change
C: Change in form and numbers
Answer: C: Change in form and numbers 
Explanation: Biological transmission of vector borne diseases: Cyclo-Propagative : The agent changes in both form and number, eg: Malaria parasite in mosquito Propagative : The agent merely multiplies in vector, but no change in form, eg: Plague bacilli in rat fleas Cyclo-Developmental : The disease agent undergoes only development but no multiplication, eg: Microfilaria in mosquito Ref : Park&;s Textbook of preventive and social medicine; 24th edition; Pg no: 98