Germs are transmitted from an infected person to healthy person by means of certain insects. These insects are called vectors.
House Fly as Vector: -
i) Housefly is a mechanical vector.
ii) It feeds on decaying matter and dung, which is rich source of germs.
iii) These germs cause typhoid fever, typhus, cholera, dysentery, tuberculosis and
anthrax etc.
iv) When flies feed, their feet, bodies and digestive system become contaminates
with germs.
v) And when this fly set on food items of human being, it transfer the germs to
food.
vi) By eating this food, a person becomes ill.
Mosquitoes as Vectors: -
i) Mosquito is a biological vector.
ii) Mosquito is a vector for transmitting malaria and yellow fever.
iii) In case of malaria, pathogen is a protozoan Plasmodium. Plasmodium under
goes two stages in its life cycle, one in man and one in the mosquito.
iv) The mosquito in its life cycle is an intermediary host. Without this disease could
not be passed from patient to healthy person.