What are infectious diseases, and what do they have to do with ecology?
Quite a lot, although we should first note that in this lecture we will focus particularly on diseases that are linked to ecology and biodiversity, as this emphasis ties in with the general theme of our course. Infectious diseases are illnesses caused by a disease agent that can be transmitted from organism to organism. Diseases can take on many forms but are generally characterized by the weakening of the infected organism, the degree of which depends on the organism’s resistance to the infection and the virulence of the disease agent causing it. The agents of disease fall into two major types. Microparasites include viruses, bacterial pathogens and parasitic protozoans, and cause what we refer to as pathogenic diseases. Examples include ebola hemorrhagic fever (a virus), Lyme disease (a bacterium), and malaria (a protozoan). Macroparasites include flatworms (Platyhelminthes), roundworms (Nematoda) and arthropods; are generally larger and have longer generation times than microparasit
