Parasitism - Wikipedia
Host and Parasite: A Mutual Relation: In the course of time a mutual adjustment or relation or tolerance frequently develops between the two which permits them . A parasitic relationship is one in which one organism, the parasite, lives off of another organism, the host, harming it and possibly causing. The dynamics of the host-parasite relationship - Volume 55 Issue 3 - J. K. Dineen, A. D. Donald, B. M. Wagland, Jan Offner.
This type of damage is characteristic of liver, cardiac muscle and kidney cells.
Host-Parasite Relationship (With Diagram)
Fatty degeneration cells are filled with an abnormal amount of fat deposits, e. Necrosis means any type of persistent cell degeneration which finally die, e.
Refers to an increased rate of cell division resulting from an increased level of cell metabolism. Leads to a greater total number of cells but not in their sizes.
This commonly follows an inflammation and is the consequence of an excessive level of tissue repair. For example—thickening of bile duct in presence of Fasciola sp. Refers to an increase in cell size. Commonly associated with intracellular parasites.
Spermatogonial cells of Polymnia nebulosum an Annelid when parasitized with Caryotropha mesnili a Protozoanare enlarged. Refers to the changing of one type of tissue into another without the intervention of embryonic tissue. The encapsulating epithelial cells and fibroblasts of the fluke, Paragonimus westermani in human lungs are transformation of certain other type of cells in the lungs.
This is the growth of cells in a tissue to form a new structure, e. Neoplastic tumour is not inflammatory. This is not required for the repair of organs. It does not conform to a normal growth pattern. It may be benign or malignant. Endoparasites with a great density causes nutritional deficiency in host by absorbing sugars, vitamins, amino-acids etc. Mal-nourished hosts are more proned to disease and infection.
Diphyllobothrium latum a fish tapeworm in human causes anaemia by absorbing profuse Vitamin B12 as much as 10 to 50 times more than do other tape-worms. Parasites in some cases also feed on host- substances, other than stored or recently acquired nutrients.
Increased number of those adult worms in lymph vessels coupled with aggregation of connective tissue may result in complete blockage of lymph flow. Excess fluid behind the blockage seeps through the walls of lymph ducts into the surrounding tissues, causing edema and ultimately with scar tissues—the elephantiasis of limbs, breasts, scrotum etc.
Effects of toxins, poisons and secretions: Specific poisons or toxins egested, secreted or excreted by parasites cause irritation and damage to hosts, e. Toxin of pathogenic Entamoeba histolytica produces toxic symptoms in parasitized mammalian hosts and creates ulcerations within the large gut of man. Schistosome cercarial dermatitis is the result of an allergin reaction against an irritating parasitic secretion from the fluke.
Gonads of parasitized hosts may change, leading to sex reversals; e. Parasitized male crab acquired secondary female characteristics like broad abdomen, appendages modified to grasp eggs, chelae become smaller, testes with testicular cells at various stages of degeneration. The mudflat snail—Ilyanassa obsoleta are directly castrated by the trematode— Zoogonus lasius.
The freshwater snail, Lymnaea stagnalis is indirectly castrated by larvae Sporocysts of Trichobilharzia ocellata a trematode. These larvae do not possess mouth and thus destroy the gonadal tissue by chemical means. An interesting aspect of parasite induced change in hosts is responsible for enhanced growth; e.
Host-Parasite Relationship (With Diagram)
Workers of the ant, Pheidole commutula become much larger when parasitized by the nematode, Mermis sp. Mice infected with larvae of Spirometra mansonoides a tapeworm grows faster than non-parasitized one. Rats when parasitized by Trypanosoma lewise increase their weight more rapidly than non-parasitized one. The enhanced growth of the host is due to stimulation of growth-promoting molecules secreted by the parasites. In immuno-parasitology, the animal is the host and the parasite is either self by molecular memory or non-self foreign.
When a host recognizes the parasite as non-self, it generally reacts against the invader in two ways: Cellular or cell mediated reactions: Where specialised cells become mobilised to arrest and eventually destroy the parasite as usual.
Innate or natural and II.
Theoretically each of them again can be of two types—cellular and humoral. Innate internal defense mechanism: These includes the following chief categories: Phagocytosis consists of three phases: Attraction of phagocytes to the non-self material, commonly by chaemo-taxis. Internalization of the foreign substance i. Fate of phagocytosed parasites: May be degraded intracellularly. May be transported by phagocytes across epithelial borders to the exterior.
HOST PARASITE RELATIONSHIPS
May remain undamaged within the phagocytes and some may even multiply within host cells. The agent must be observed in every case of the disease. The agent must be isolated from a diseased host and grown in pure culture.Host-Parasite Relationship
When purified agent is inoculated into a healthy but susceptible host, it must cause the same disease. The agent must be reisolated from the newly infected, diseased host, and be identical to the previously identified causative agent. Identification of disease agents, according to the postulates requires growing the organism; this can be difficult or impossible for some: Treponema pallidum, Mycobacterium leprae, and so this cannot be an inflexible approach.
How they behave within a population? NOT all communicable diseases are equally contagious. Contagiousness depends on several factors. II Frequency in a population: Diseases in a population: Details must be included the full name of replacement person, their title, contact phone number and email address. All other registration details will be assigned to the new person unless otherwise specified. However, Registration cannot be transferred if it is intimated within 14 days of respective conference.
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