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
All of the following are commonly used Filarial indices except - 
Select and explain. 
A. Microfilaria reate, B. Filarial disease rate, C. Filarial epidemicity rate, D. Mosquito infection rate
B: Filarial disease rate
Answer: B: Filarial disease rate 
Explanation: <p> filarial indices 1. Microfilaria rate: percentage of persons showing microfilaria in their peripheral blood (20 cu. mm) in sample population, one slide being taken from each person. 2. Filarial endemicity rate: percentage of persons examined showing microfilaria in their blood/disease Manifestation / both. 3. Microfilarial density: number of microfilaria per unit volume of blood in samples from individual person. 4. Filarial disease rate. {Reference: park&;s textbook of preventive and social medicine, 23rd edition, pg no.274}</p>