Host-Parasite Relationship (With Diagram)
Basis of Classification, Types of Parasites and Definition and Example. In the course of their life cycle, parasite may become associated with more than one host. which could be defined only by workers in other disciplines. Among such The host-parasite relationship could be discussed compre- hensively only on a. Types of parasitism (pathogenicity, being pathogenic). – obligate parasites: in defined host (range of hosts) always pathogenic, never found in the normal flora.
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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. May remain undamaged within the phagocytes and some may even multiply within host cells. Fate of encapsulated parasite: Nacrezation is another type of cellular defense mechanism, known in molluscs.
As certain helminth parasites, e. In so doing, a pearl is formed and the enclosed parasite is killed. The process involves deposition of the black-brown pigment, melanin around the invading parasite. Melanization is chemically the result of enzymatic oxidation of polyphenol by tyrosinase.
This is detrimental to the parasite and may lead to its death by interfering with such vital activities like hatching, moulting or feeding. Melanization of the nematode, Heterotylenchus autumnalis in haemocoel of larval house-fly—Musca domestica.
These fall into two categories: These are two types: Those are directly parasitocidal, e.
Those that enhance cellular reactions, e. These glycoprotein molecules enhance phagocytosis of the non-self-material.
These are also of two types: Immunity refers to resistance against disease caused by a foreign agent. Antigen is the only foreign substance Proteins, glycoproteins, nucleoproteins etc. These are chiefly of two types: Somatic antigens molecules comprising some of parasites.
Mechanism of antigen-antibody interactions: Host lymphocytes are now stimulated to proliferate and differentiate. Plasma cells are B-lymphocyte effector cells that secrete antibodies. The parasites try to establish itself within the host while the latter tries to destroy it which results in dynamic state of equilibrium. If resistance is sufficiently high to prevent parasite reproduction, it is known as absolute resistance and if parasite is able to overcome it and still reproducing it is called partial resistance.
The properties and number of antibodies vary from individual to individual parasitic infections. These are known to operate in malaria and other viral reactions by rendering the host cells unfit for habitation by intercellular parasites. Categories of antigen-antibody interactions: These are of three types: This is referred to as agglutination reaction.
Lysin and lysis reaction: Lysin antibodies dissolves or lyses antigens. The reaction occurs in the presence of complement, a substance in normal serum representing a system of enzymes.
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In the second phase of reaction the fixation of complement by antigen-antibody occurs which is used for detecting many of the parasitological infections. This precipitin reaction is used for detecting infections like plague, anthrax, tularaemia etc. In vertebrates, this is introduced through the action of antigen, antibody and complement.
This occurs in two ways: Opsonins are antibodies occurring in normal as well as in immune sera which inhibit microbes making them more amenable to phagocytosis. This is usually of two types: Cattle infected with certain species of Babesia shows premonition. While cattle, long after Theileria parva has disappeared, shows sterile immunity. Certain breeds of cattle develop partial immunity against Trypanosoma. Immunity to Toxoplasma gondii is evident in adult humans who show the antibodies, while congenital infection with T.
The trophozoites of gregarines Gregarina sp exhibit an eerie gliding movement. Various theories have been put forward. Similar movement has been noticed for the trophozoites of Plasmodium and Eimeria. In such case, infected individual show waves of blood parasites. Each wave comprises of parasites expressing a surface antigen that is different from the previous wave. Thus, by the time the host produces antibodies against the parasites, an antigenically new organism has grown out.
Include adult Schistosomes and certain microfilariae. Concomitant immunity is shown by rodents on Rhesus monkeys against infection of Schistosoma. Microfilariae of Wuchereria, Brugia etc.
Host-Parasite Relationship (With Diagram)
The serious and often fatal results of trichiniasis are due to the offspring of the infecting worms and not to the adult worms in the intestine. Parasites develop anatomic abnormalities along with oedema and necrosis, decreased albumin levels and significant reduction in weight gain and often death follows; e. It fails to develop a vulvar flop in calves.
Parasite does not grow as rapidly or reach its normal size, e. Antibodies, although, do not generally cause the death of adult worms but affected worms undergo retarded growth with destrobilisation. Protective Immunity is absent in case of tissue trematodes like Fasciola sp. This phenomena of antigen shearing between hosts and parasites is called molecular mimicry.
There are three possibilities regarding its origin: Effects of parasitism on parasites: This adaptation takes place by two ways as follows: Sense organs are poorly developed.
Less developed locomotory organs. Intestinal parasites have no well-developed digestive organs, e. New attainment of organs or systems: Tactile hairs in mites. Barbed proboscis in ticks.