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The Science of Parasitology

Black fly (Simulium yahense)

Parasitology is the part of biology that studies parasitism, and their field of study and research are parasitic organisms and their relationship with their hosts and the environment. This science is related intimately with Zoology, Ecology and Microbiology. Parasitology has important implications in medicine, pharmacy and veterinary, constituting the medical parasitology and veterinary parasitology, applied sciences to health, that besides studying parasitism, too investigates the solutions.

Parasitism is a form of symbiosis or common life of living beings, is its dark side, the opposite of mutualism, in which both species are favored, because parasitism involves exploitation of species. Its a part of the evolution, since both species evolve over time. There are degrees, from facultative parasites to obligate parasites, which can not survive by themselves.

The parasite needs a host and overcome what can separate it. Ectoparasites or external parasites, animals and plants, have it easier than endoparasites or internal parasites, because the most common route of entry is the digestive, as they have to overcome barriers of the immune system, temperature, osmotic pressure, etc. This whole process of adaptation arise in invertebrates living in hostile systems.

Although the parasite is harmful, isn't interested in being lethal to the host, as their way of life and livelihood would end, must be in balance, which is reached by coevolution, the two species have evolved in an interaction. It is estimated that parasitism already exist in the Precambrian, some 1,100 million years ago.

The parasite must have certain characteristics that facilitate their way of life: ease of reproduction, organs for fixation, loss of sensory organs (not to waste energy), large egg production, lack of pigments, adapting their cycles to the host, etc. Moreover, the host may be final or intermediary. The parasite can have a life cycle, having an internal or external phase, or only one; or have the cycle is directly or indirectly through one or more intermediate hosts.

Among the major groups of parasites are protozoa; helminth, worms, flatworms (flattened flukes and tapeworms) and aschelminthes (cylindrical, the most important nematodes); and arthropods. But there are also other parasites groups such as fungi (Cordyceps, parasite of insects), viruses, or vertebrates, like the cuckoo, a bird.

The identification techniques of endoparasites may be direct (liquid stool samples) or indirect (ELISA test). The identification of hemoparasites and intercellular parasites, found in the blood or tissues may be direct (such as blood smear or sample analysis) or indirect (such as serum antibodies). The identification of arthropods are usually direct, by observation with a magnifying glass or microscope.

1. Parasitology

- Reading: Wikipedia. Parasitology

2. Interspecific interactions and parasitism. Origin of parasitism

- Reading: Wikipedia. Parasitism

3. Main classes of parasites

- Reading: CDC. About Parasites

4. The parasitology lab: diagnosis approaches and methods

- Reading: Hindawi. Diagnosis of Parasitic Diseases: Old and New Approaches

Resources for further learning

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