Pathogen
From Wikipedia, the free encyclopedia
For other uses, see Pathogen (disambiguation).
A pathogen (Greek: πάθος pathos “suffering, passion” and -γενής -genÄ“s “producer of”) in the oldest and broadest sense is anything that can produce disease, a term which came into use in the 1880s.[1][2] Typically the term is used to describe an infectious agent such as a virus, bacterium, prion, fungus, viroid, or parasite that causes disease in its host. The host may be an animal, a plant, a fungus or even another microorganism.[3][4]There are several substrates including pathways whereby pathogens can invade a host. The principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen. Diseases caused by organisms in humans are known as pathogenic diseases. Some of the diseases that are caused by viral pathogens include smallpox, influenza, mumps, measles, chickenpox, ebola and rubella.
Not all pathogens are necessarily undesirable to humans. In entomology, pathogens are one of the "three P's" (predators, pathogens and parasitoids) that serve as natural or introduced biological controls to suppress arthropod pest populations.
Contents
Types of pathogen
Subcellular infectious objects
Prionic
Main article: Prion
According to the prion theory, prions are infectious pathogens that do not contain nucleic acids. These abnormally folded proteins are found characteristically in some diseases such as scrapie, bovine spongiform encephalopathy (mad cow disease) and Creutzfeldt–Jakob disease.[5] Although prions fail to meet the requirements laid out by Koch's postulates, the hypothesis of prions as a new class of pathogen led Stanley B. Prusiner to receive the Nobel Prize in Physiology or Medicine in 1997.Viral
Further information: Viral disease
Pathogenic viruses are diseases mainly those of the families of: Adenoviridae, Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Papovaviridae, Polyomavirus, Rhabdoviridae, Togaviridae. Viruses typically range between 20-300 nanometers in length. [6]Prokaryotes
Bacterial
Main article: Pathogenic bacteria
Although the vast majority of bacteria are harmless or beneficial, a
few pathogenic bacteria can cause infectious diseases. Bacteria can
often be killed by antibiotics because the cell wall on the outside is
destroyed, expelling the DNA out of the body of the pathogen, therefore
making the pathogen incapable of producing proteins and dies. They
typically range between 1 and 5 micrometers in length.Eukaryotes
Fungal
Main article: Pathogenic fungi
Fungi comprise a eukaryotic kingdom of microbes that are usually saprophytes
(consume dead organisms) but can cause diseases in humans, animals and
plants. Fungi are the most common cause of diseases in crops and other
plants. The typical fungal spore size is 1-40 micrometers in length.Other parasites
Main article: Human parasites
Some eukaryotic organisms, such as protists and helminths, cause disease.Treatment and health care
Bacteria are usually treated with antibiotics while viruses are treated with antiviral compounds. Eukaryotic pathogens are typically not susceptible to antibiotics and thus need specific drugs. Infection with many pathogens can be prevented by immunization. A small amount of pathogens are used in vaccines to make immunity stay alert and strengthen defense on the insides to prepare for a larger quantity of the virus ever getting inside. Hygiene is critical for the prevention of infection by pathogens.Virulence
Virulence (the tendency of a pathogen to cause damage to a host's fitness) evolves when that pathogen can spread from a diseased host, despite that host being very debilitated. Horizontal transmission occurs between hosts of the same species, in contrast to vertical transmission, which tends to evolve symbiosis (after a period of high morbidity and mortality in the population) by linking the pathogen's evolutionary success to the evolutionary success of the host organism.Evolutionary medicine has found that under horizontal transmission, the host population might never develop tolerance to the pathogen.
Transmission
Main article: Transmission (medicine)
Transmission of pathogens occurs through many different routes,
including airborne, direct or indirect contact, sexual contact, through
blood, breast milk, or other body fluids, and through the fecal-oral route.See also
- Ecological competence
- Emerging Pathogens Institute
- Human pathogen
- List of human diseases associated with infectious pathogens
- Pathogen-Host Interaction Database (PHI-base)
References
- "Pathogen". Dictionary.com Unabridged. Random House. Retrieved August 17, 2013.
- Casadevall, Arturo; Pirofski, Liise-anne (11 December 2014). "Ditch the term pathogen". Comment. Nature (paper) 516 (7530): 165–6. doi:10.1038/516165a.
- http://www.medterms.com/script/main/art.[dead link]
- "MetaPathogen - about various types of pathogenic organisms". Retrieved 15 January 2015.
- The prion diseases STANLEY B. PRUSINER, Scientific American
- Viral Special Pathogens Branch | [26] Moved | CDC
External links
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