CBSE Class 9 Answered

Insects like mosquitoes, bedbugs and fleas spread diseases like malaria, dengue fever and plague. These insects suck the blood of a person infected with the disease and become carriers of the germs. When these insects bite a healthy person, they inject these germs into the blood of the healthy person.

The mechanism used by most mosquito-borne parasites, including malaria, yellow fever, dengue, and the encephalitis viruses is as follows: After a blood meal, the causative agent enters and survives inside the mosquit?o, ??increases?? in numbers, and then migrates?? to the mosquito's salivary glands. The infected ?mosquito ??then seeks? its second blood meal from an uninfected host and transfers?? the causative agent? from its salivary glands during the course of the bite. In this way, the causative agent is trans?mitted.?