Answer:
Flies, mosquitoes and fleas
Explanation:
Living organisms which spread infectious diseases from infected to healthy humans or from animals to humans are called vectors. Flies, fleas and mosquitos are the vectors which are used by some protozoa to transmit diseases for examples sand flies are the vectors of Leishmania, a unicellular parasitic protozoan. Plasmodium, a parasitic protozoan cause malaria which is transmitted by mosquitos.