In the formula for vectorial capacity of an anopheline population, which parameter appears raised to the power of the extrinsic incubation period (n)?
- A Probability of daily survival of the vector (p) ✓
- B Man-biting rate (ma)
- C Duration of sporogony (n)
- D Sporozoite rate (s)
Correct answer: A. Probability of daily survival of the vector (p)
Explanation
Vectorial capacity equals ma squared multiplied by p raised to the power n, divided by minus natural logarithm of p. The probability of daily survival p carries the exponent n because the mosquito must survive at least n days after infection before it can transmit sporozoites; this makes longevity the most sensitive determinant of transmission. The man-biting rate is squared but not exponentiated, and sporogony duration appears only as the exponent itself.
Reference: MacDonald's Epidemiology and Control of Malaria, cited in Park's Textbook of Preventive and Social Medicine, 26th ed.
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