Archaeoparasitology - Parasitology Basics

Parasitology Basics

Parasites are organisms which live in close association with another organism, called the host, in which the parasite benefits from the association, to the detriment of the host. Many other kinds of associations may exist between two closely allied organisms, such as commensalism or mutualism.

Endoparasites (such as protozoans and helminths), tend to be found inside the host, while ectoparasites (such as ticks, lice and fleas) live on the oustide of the host body. Parasite life cycles often require that different developmental stages pass sequentially through multiple host species in order to successfully mature and reproduce. Some parasites are very host-specific, meaning that only one or a few species of hosts are capable of perpetuating their life cycle. Others are not host-specific, since many different hosts appear to harbor and pass on the infective stages of the parasite.

Most archaeoparasitology reports involve species which are considered to be true parasites of humans today. However, incidental parasitism (referred to by some authors as "pseudoparasitism", "false parasitism" or "accidental parasitism") occurs when a parasite which does not normally utilize a host for the perpetuation of its lifecycle is found in that host incidentally. One example is finding the eggs of Cryptocotyle lingua (a fish parasite) in the stomach contents of an Eskimo mummy. It is estimated that 70% of the "parasite" species reported from present-day humans are actually only incidental parasites. Some incidental parasites do cause harm to the infested pseudohosts.