Para

• Parasitology


  The study of the interaction between parasites and their hosts

  
• Parasitologist


  A person who studies parasites

  
• Parasites


  An organism that lives on or in a host organism and gets its food from or at the expense of its host
• Three main classes of parasites

  • Protozoa
  • Helminths
  • Ectoparasites

  
• Try to identify the following organisms: Protozoans and Helminths

  
• Eating raw or semi-raw meat or fish, being in contact with pets, contaminated water or food (poor sanitation), poor hygiene, unwashed hands, unwashed vegetables and fruits, doctors and especially pediatricians are also exposed to parasites, as their patients often have parasites, institutional care centers, during traveling to a region known to have parasites (mostly rural or developing countries), living in regions known to have parasites, elderly people and children are more vulnerable to parasitic infections, weakened immune system e.g. HIV or AIDS are how you get parasites and what are the risk factors
• Nurses prevent further damage to the host especially if the hosts involve children
• Lice infestation is common among school age while pinworm is common among children aged 5-10
• Scotch tape Test = A test for children to identify a pinworm infestation
• Whipworm and Hookworm = examples of soil transmitted helminths

  
• The skin is the portal of entry of hookworms and Plasmodium (specie causing Malaria)
• Larvae stage of hookworms enters the human host
• Human mouth is the portal of entry of amoeba and whipworms
• In the human host, most parasites hatch in the small intestines
• As long as the head survives, tapeworms will continue to grow and shed segments
• Ascaris' mode of reproduction is sexual
• Anemia and distended abdomen are common signs and symptoms of children with helminthic infestation
• Definitive host


  Harbors the adult or sexual stage of the parasite or the sexual phase of the parasite's life cycle
• Intermediate host


  Harbors the larval or asexual stage of protozoans and parasites or the asexual phase of its life cycle
• Accidental host


  A living organism that can serve as a host in a particular parasite's lifecycle but is not a usual host in that life cycle
• Facultative parasite


  An organism that can be parasitic but does not have to live as a parasite
• Obligate parasite


  Has no choice to survive. It must be a parasite. Most parasites that infect humans are obligate parasites
• Infective stage


  The stage in the life cycle at which the parasite is able to initiate an infection to its host. The parasite is capable of entering its host and continue its development within the host
• Diagnostic stage


  The stage at which the parasite leaves the host
• Protozoa


  • From Greek protozoon word meaning "First animal"
  • Eukaryotic organisms that inhabit water, soil, and from animals
• Characteristics of Protozoans


  • Unicellular
  • Aerobic heterotroph
  • Asexual reproduction (binary fission, budding, multiple fission)
  • Sexual reproduction (conjugation, gamete formation)

  
• Encystment


  A protective capsule produced by some protozoa under certain adverse conditions that permits the organism to survive when food, moisture, oxygen are lacking, or when temperatures are not suitable, or when toxic chemicals are present
• Cyst


  The protective capsule produced by some protozoa
• Oocyst


  Cyst formed by members of the phylum Apicomplexa used to produce new cells asexually
• Trophozoite


  The growing stage in the life cycle of some sporozoan parasites, when they are absorbing nutrients from the host. The active, feeding, multiplying stage of most protozoa. In parasitic species this is the stage usually associated with pathogenesis. The infectious stage of a protozoa that has a highly condensed cytoplasm and thick cell wall
• Nutrition of Protozoans


  • All protozoa live in areas with a large supply of water. Some protozoa transport food across the plasma membrane. Ciliates take in food by waving their cilia toward a mouth-like opening called a cytostome. Amoebas engulf food by surrounding it with pseudopods and phagocytizing it. In all protozoa, digestion takes place in membrane-enclosed vacuoles, and waste may be eliminated through the plasma membrane or through a specialized anal pore
• Classification of Protozoans


  • Mastigophora or Flagellated protozoans
  • Sarcodina or Amoeboids
  • Sporozoa or Sporozoans

  
• Mastigophora or Flagellated protozoans


  • They are parasites or free-living. They have flagella for locomotion. Their body is covered by a cuticle or pellicle. Freshwater forms have a contractile vacuole. Reproduction is by binary fission (longitudinal division). Examples: Trypanosoma, Trichomonas, Giardia, Leishmania

  
• Trichomonas vaginalis


  Causes the disease Trichomoniasis, a sexually transmitted disease (STD). Treated with Metronidazole. Destroys epithelial cells and releases cytotoxic substances, increasing vaginal pH and leukocyte count. Symptoms include itching, burning in genital organs, and discharge. Often asymptomatic in males
• Sarcodina or Amoeboids


  • They live in freshwater, sea or moist soil. Movement is by pseudopodia, capturing prey. No definite shape, no pellicle. Contractile vacuole present in freshwater forms. Reproduction is by binary fission and cyst formation. Examples: Amoeba, Entamoeba

  
• Entamoeba Histolytica


  Infective stage is mature cyst. Diagnostic stage is cyst and trophozoite. Virulence factors are lectin (mediates attachment and cell lysis) and amebapores (used to penetrate). Causes amebiasis, amebic dysentery, and amebic liver abscess. Transmitted by feco-oral route. Risk factors include poor sanitation, travel to tropical areas, living in institutions, and immunocompromised status. Treated with metronidazole and diloxanide furoate. Prevention involves safe drinking water and thorough handwashing
• Sporozoa or Sporozoans


  • They are endoparasitic. No specialized organ for locomotion, but have a pellicle with subpellicular microtubules for movement. Reproduction is by sporozoite formation. Examples: Plasmodium, Myxidium, Nosema, Globidium
• Plasmodium


  Causative organisms of malaria: P. falciparum (deadliest, most prevalent in Africa), P. vivax, P. malariae, P. ovale, P. knowlesi. Infective stage is sporozoites. Vector is female Anopheles mosquito. Pathogenesis involves attacking the liver and red blood cells, releasing toxic hemozoin. Malaria is a serious and sometimes fatal disease. Transmitted by mosquito bites, blood transfusion, and contaminated needles. Diagnosed by direct microscopy. Treated with chloroquine. Prevented by avoiding mosquito bites
• Ciliophora or Ciliated protozoans


  • They are aquatic and move actively with the help of thousands of cilia
  • They have fixed shape due to covering of pellicle
  • They may have tentacles, e.g. in the sub-class Suctoria
  • Contractile vacuoles are present
  • Some species have an organ for defence called trichocysts
  • They move with the help of cilia and the movement of cilia also helps in taking food inside the gullet
  • They reproduce by transverse division and also form cysts

  
• Ciliophora or Ciliated protozoans


  • Paramecium, Vorticella, Balantidium, etc.