Clinical para

• Helminths and Protozoans are among the common agents of infection
• Predation: It may attack another living animal, con-

  suming part or all of its body for nourishment
• The attacker iss called the Predator
• The victim is called the Prey
• Scavenging: An animal deriving its nutrition from already dead animals, either devouring those dead of natural causes or taking the leavings of s predator
• Scavengers: Animals that subsist in scavenging
• Symbiosis (“living together”): This refers to association of two species for food and shelter. Different forms of symbiosis may be distinguished on the basis of whether or not the association is detrimental to one of the two partners.
• Mutualism: A specialized type of symbiosis that occurs when associations are beneficial to both organisms.
• Parasitism: Symbiotic relationship in which one animal, the parasite, lives at the expense of the other animal, the host.
• Medical Parasitology is a branch of biology that is focused on the animal parasites of human and their medical significance and public health impact. It also covers phenomena of dependence among living organisms.
• Parasitology is the scientific study of a parasite, an organism that depends, and a host, an organism that provides shelter and nourishment.
• Definitive Host: Harbors the adult or sexually mature stage of parasite.
• Intermediate Host: Harbors the larval stages or asexual forms of the parasites.
• Vector: blood feeding arthropod.
• Reservoir Host: A natural habitat where the parasite can survive without causing disease to its host.
• Mechanical Vector: is used to describe a vector which assist in the transfer of a parasitic form between hosts but is not essential in the life cycle of parasite.
• Non-arthropods mechanical vector is called transport or paratenic host
• First intermediate host (1st IH): harbors the early larval stage of the parasites.
• Second intermediate host (2nd IH): harbors the infective larval stage of the parasit
• Paratenic host: Harbors the parasite in an underdeveloped or in arrested state of development.
• Reservoir host: Alternative host to a parasite that is harbored normally by humans.

  • The host continues the life cycle of the parasite and acts as an additional source of infection.
• A parasitic infection in which the normal host is an animal but can produce disease in human if they be- come infected accidentally is known as zoonosis
• Obligate parasite: Organism that cannot survive in any other manner in the absence of a host.
• Facultative parasite: Organism that may exist in a free-living state or as a commensal and that, if opportu- nity presents itself, may become parasitic.
• Temporary parasite: Parasites that are obligatory at one or more stages of their life cycles but free living at others.
• Intermittent parasite: Small organisms, such as mosquitoes, which must periodically seek out other and larger forms on which to nourish themselves. These are parasites that visit their host during feeding time.
• Endoparasite: Parasites living within the host.
• Ectoparasite: Parasites that are found on the surface of the body.
• Preadaptive changes is due to increased resistance to the enzymatic activities of the host.
• Only groups of protozoans that contain nothing but parasitic forms: Phylum Apicomplexa and Microsporidia.

  • Members of these phyla have no locomotor organelles, although the structures are present in one form or another in all other phyla of protozoa, even in their parasitic representatives.
• Most of the free-living turbellarian flatworms are provided with a ciliated epidermis in the adult stage.

  • Cilia are not found on the parasitic members of this group or on the related but strictly parasitic trema- todes and cestodes.

  • A digestive tract, moderately complex in the turbellarians, is generally reduced in the trematodes and is absent in the cestodes.
• Specialized attachment organs in the form of suck- ers and hooks have been developed by the parasitic flatworms.
• E. histolytica (pathogenic intestinal amoeba)

  elaborates a proteolytic enzyme that aids its penetration of the intestinal mucosa.
• Schistosoma sp. (blood fluke) in its cercarial stage has penetration glands which produce enzyme capable of digesting the skin.
• Hymenolepis nana (dwarf tapeworm) during its embryonic stage prior to developing into a cysticercoid larva, penetrates an intestinal villus with the help of the six hooklets it bears.
• Fasciolopsis buski (Giant intestinal fluke) when present toxic symptoms in large numbers but the precise cause is unknown. It may produce severe local damage to the intestinal wall by means of its powerful suckers. In high intensity infection when there is a significant number of adult flukes, intestinal obstruction may likely occur.
• Entamoeba histolytica erodes the intestinal wall, destroying the tissues locally by means of a pro- teolytic enzyme.
• Plasmodium falciparum (pathogenic species of malarial parasite) invade and multiply in red blood cells, which are destroyed in the process and may also attach to the walls of smaller blood vessels in the brain, occluding them to produce localized ischemia.
• Ascaris lumbricoides (Giant intestinal roundworm) may perforate the bowel wall, cause intestinal obstruction if present in large numbers, and ectopically may invade the appendix, bile duct, or other organs.
• Human Hookworms, like Ancylostoma duodenale and Necator americanus, suck blood deprive the host of more iron than is replaced by diet and therefore leading to a case of microcytic hypochromic anemia.