What is the role of parity rates in assessing vector populations?

• A. Parity rates measure larval density in water.
• B. Parity rates indicate species diversity.
• C. Parity rates indicate older, potentially infectious female mosquitoes; higher parity suggests greater transmission risk.
• D. Parity rates measure daily landing rate on humans.

Answer: (C)

Parity rates tell you about the age structure of the female mosquito population and their potential to transmit disease. A parous female has already completed at least one egg-laying cycle, meaning she’s older and has taken more blood meals. Pathogens often need time to develop inside a mosquito (the extrinsic incubation period), so older, parous females are more likely to have become infectious and capable of transmitting pathogens to humans. Seeing a higher parity rate in a population, therefore, points to greater transmission risk because more of the mosquitoes have survived long enough to become infectious. This makes parity a useful proxy for assessing vectorial capacity and informing control strategies aimed at reducing adult survival. The other options describe different aspects—larval density, species diversity, or daily biting rate—that don’t directly indicate whether the mosquitoes present are older and potentially infectious.