Infectious and parasitic diseases
A parasitic disease is an infectious disease caused or transmitted by a parasite.
Many parasites do not cause diseases. Parasitic diseases can affect practically all living organisms, including plants and mammals. The study of parasitic diseases is called parasitology. The share of parasitic diseases account for about 14 000 000 deaths per year, representing 25% of global mortality - one in four deaths according to the WHO.
Some parasites like Toxoplasma gondii and Plasmodium spp. can cause disease directly, but other organisms can cause disease by the toxins that they produce.