Dysentery is caused by various pathogens, including bacteria and protozoa. One of the common causes of amoebic dysentery is the protozoan Entamoeba histolytica.
Malaria is caused by a protozoan parasite of the genus Plasmodium, which is transmitted through the bite of an infected mosquito.
Thus, both diseases are caused by Protozoans.
Therefore, the correct answer is (3) Protozoans.