is the study of parasites
, their hosts
, and the relationship between them. As a biological discipline
, the scope of parasitology is not determined by the organism or environment in question, but by their way of life. This means it forms a synthesis of other disciplines, and draws on techniques from fields such as cell biology
, molecular biology
The parasitic mode of life is the most common on the planet, with representatives from all major taxa, from the simplest unicellular organisms to complex vertebrates. Every free-living species has its own unique species of parasite, so the number of parasitic species greatly exceeds the number of free living species.
The study of these diverse organisms means that the subject is often broken up into simpler, more focused units, which use common techniques, even if they are not studying the same organisms or diseases. Much research in parasitology falls somewhere between two or more of these definitions. In general, the study of prokaryotes fall under the field of bacteriology rather than parasitology.
One of the largest fields in parasitology, medical parasitology is the study of those parasites which infect humans. These include organisms such as:
Medical parasitology can involve drug development, epidemiological studies and study of zoonoses.
The study of parasites which cause economic losses in agriculture
operations, or which infect companion animals
. Examples of species studied are:
- Lucilia sericata, a blowfly, which lays eggs on the skins of farm animals. The maggots hatch and burrow into the flesh, distressing the animal and causing economic loss to the farmer
- Otodectes cynotis, the cat ear mite, responsible for Canker.
- Gyrodactylus salaris, a monogenean parasite of salmon, which can wipe out populations which are not resistant.
Parasites exhibit an aggregated distribution among host individuals, thus the majority of parasites live in the minority of hosts. This feature forces parasitologists to use advanced biostatistical methodologies.
This is the study of structures of proteins from parasites. Determination of parasitic protein structures may help to better understand how these proteins function differently from homologous proteins
in humans. In addition, protein structures may inform the process of drug discovery
Parasites can provide information about host population ecology. In fisheries biology
, for example, parasite communities can be used to distinguish distinct populations of the same fish species co-inhabiting a region. Additionally, parasites possess a variety of specialized traits and life-history strategies that enable them to colonize hosts. Understanding these aspects of parasite ecology, of interest in their own right, can illuminate parasite-avoidance strategies employed by hosts.
Taxonomy and phylogenetics
The huge diversity between parasitic organisms creates a challenge for biologists who wish to describe and catalogue them. Recent developments in using DNA
to identify separate species and to investigate the relationship between groups at various taxonomic
scales has been enormously useful to parasitologists, as many parasites are highly degenerate
, disguising relationships between species.