Protozoan Diseases

• Parasite


  Live organism living in or on, and having some metabolic dependence on another organism known as a host
• Parasitism


  A relationship in which one of the participants, the parasite, either harms its host or in some sense lives at the expense of the host
• Parasitic disease


  An infectious disease caused or transmitted by a parasite
• Infection


  The invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce
• Medical parasitology


  The study and medical implications of parasites that infect humans
• Host


  The organism in, or on, which the parasite lives and causes harm
• Types of parasites


  • Protozoa (unicellular organisms, e.g. Plasmodium (malaria))
  • Metazoa (multicellular organisms, e.g. helminths (worms) and arthropods (ticks, lice))
• Endoparasite


  A parasite that lives within another living organism (e.g. malaria, Giardia)
• Ectoparasite


  A parasite that lives on the external surface of another living organism (e.g. lice, ticks)
• Definitive host


  The organism in which the adult or sexually mature stage of the parasite lives
• Intermediate host


  The organism in which the parasite lives during a period of its development only
• Zoonosis


  A parasitic disease in which an animal is normally the host - but which also infects man
• Vector


  A living carrier (e.g. an arthropod) that transports a pathogenic organism from an infected to a non-infected host
• Calcified helminth eggs found in mummies


  1200 BC
• Hippocrates knew about worms from fishes, domesticated animals, and humans

  460 to 375 BC
• Roman physician Celsus familiar with human roundworms and tapeworms

  25 BC to AD 50
• Roman physician Galen familiar with human roundworms and tapeworms


  AD 129 to 200
• Paulus Aegineta described Ascaris, Enterobius, and tapeworms


  AD 625 to 690
• Antonie van Leeuwenhoek observed and illustrated Giardia lamblia


  1681
• Detailed anatomy of worms described, first by Edward Tyson


  Late 17th century
• James Paget discovered the intestinal nematode Trichinella spiralis in humans


  1835
• Friedrich Lösch discovered the pathogen Entamoeba histolytica


  1873
• Karl Georg Friedrich Rudolf Leuckart discovered the alternation of generations involving parasitic and free-living phases


  1883
• Patrick Manson discovered the life cycle of elephantiasis


  1877
• Friedrich Zenker recognized the clinical significance of the adult worms infection and concluded that humans became infected by eating raw pork


  1860
• Sir Ronald Ross received the Nobel Prize for Physiology or Medicine for his work on the transmission of malaria


  1902
• Shimesu Koino discovered the life cycle in humans, including the migration of the larval stages around the body


  1922
• Humans have acquired an amazing number of parasites, about 300 species of helminth worms and over 70 species of protozoa
• Malaria has killed more people since humans first evolved than any other disease
• The world's largest flowering plant, called Rafflesia, is parasitic, living inside tropical trees
• Tapeworms can grow inside your and reach lengths of up to 30 feet long
• Helminths are one of the leading causes of morbidity in the developing world with over two billion people affected. That's almost a third of the world's population
• Infection can cause physical, nutritional and cognitive impairment in young, developing children
• The global burden of helminth disease exceeds that of conditions such as malaria and tuberculosis
• An estimated 819 million people worldwide are infected with Ascaris (common roundworm), 464 million with Trichuris (whipworm), and 438 million with hookworm
• Classification of protozoa


  • Systemic - detected in the blood
  • Intestinal - Transmitted by the faecal-oral route and cause diarrhea
• Important systemic protozoa


  • Plasmodium
  • Toxoplasma gondi
  • Leishmania
  • Trypanosoma
• Toxocara


  A world-wide infection of dogs and cats where human infection occurs when embryonated eggs are ingested from dog or cat faeces, causing visceral larva migrans (VLM)
• Important metazoa - systemic nematodes

  • Onchocerca volvulus
  • Wuchereria bancrofti
  • Brugia malayi
• Lymphatic Filariasis


  120m people infected in >80 countries in Africa, Asia, the Pacific islands and South and Central America, 40million of those infected are disfigured or severely incapacitated, 95% cases due to Wuchereria bancrofti