What is meant by parous rate and how is it typically calculated in mosquito surveillance?

• A. It is the proportion of male mosquitoes.
• B. It is the proportion of immature females.
• C. It is the proportion of older, egg-laying females; calculated by dissecting ovaries and classifying follicles as mature vs immature.
• D. It is the rate at which mosquitoes hatch from eggs.

Answer: (C)

Parous rate reflects the proportion of older, egg-laying female mosquitoes in a population. In surveillance, you determine this by dissecting the ovaries and classifying the follicles as mature (parous, indicating a completed gonotrophic cycle) or immature (nulliparous, no prior oviposition). The rate is the number of mature ovaries divided by the total number of females examined. This measure helps gauge the age structure of the population, which matters because older females have had more chances to acquire and transmit pathogens. It’s not about males, not about immature females, and not about hatching rates.