Bachelor’s Degree Programme(BSCG)– INSECT VECTORS AND VECTOR BORNE DISEASES Answer | BZYET-143(Q-6)
6. a) Describe the life cycle of the Anopheles mosquito.
b) Explain the epidemiology of malarial parasites.
a) Mosquitoes lay eggs directly on the water (Culex, Culiseta, Anopheles) or on moist substrates ( Aedes and Culiseta). In some species (Aedes), in the absence of impoundment, eggs can remain viable for several years (in quiescence). Each impoundment of the spawning area (larval location) generates the simultaneous appearance of a multitude of larvae whose aquatic development is variable according to the temperature conditions (from 5 to 90 days). Larvae live in the water.
At the end of 4 molts, they turn into nymphs before emerging into the adult state. After emergence, males (emerged first) and females mate. Then the females disperse in search of hosts while the males remain on the spot and survive only a few days. The dispersal of females in search of a blood meal necessary for the maturation of eggs can reach several tens of kilometers in a few days and lay eggs again on the water, hence the cycle can restart.
b) The malaria parasite is transmitted via the bite of a female Anopheles spp mosquito, which occurs mainly between dusk and dawn. Other rare mechanisms for transmission include congenitally acquired disease, blood transfusion, sharing of contaminated needles, organ transplantation, and nosocomial transmission.
Malaria occurs primarily in tropical and some subtropical regions of Africa, Central and South America, Asia, and Oceania. There is tremendous geographic variation in the intensity of transmission and risk of infection. Human malaria is caused by one or more parasites: Plasmodium falciparum, P. vivax, P. ovale, or P.
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