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classification of parasites


  • NB. unicellular or acellular animals (eucaryotic);
  • sarcomastigophora (motile elements)
  • ciliophora (cilia)
    • Balantidium
  • sporozoa (non-motile, alternate sexual/asexual cycles)
    • Plasmodium - see malaria
    • Toxoplasma - mainly through contact with cats, a potential issue during pregnancy see toxoplasmosis
    • Pneumocystis - Pneumocystis carinii is a significant cause of pneumonia in the immunocompromised such as those with HIV / AIDS

metazoa (helminths):

  • NB. multicellular animals (worms, insects, etc.);

flat worms:

  • monogeneans:
    • very small parasitic flatworms mainly found on skin or gills of fish, and also in the urinary bladder and rectum of cold-blooded vertebrates.
    • none infect birds, and only one (Oculotrema hippopotami) infects mammals, parasitizing the eye of the hippopotamus.
  • Trematodes (flukes) - watersnails eat eggs → cerceriae;
    • Schistosoma (invade skin if swim→adults in venous complexes) - see schistosomiasis
    • Fasciola (aquatic plant ingested→adults in liver)
    • Opistorchis (raw fish ingested→adults in liver)
    • Paragonimus (raw crustaceae ingested→adults in lung)
  • Cestodes (tapeworms)
    • Taenia
      • saginata (rare beef ingested → adult in GIT)
      • solium (rare pork ingested→adult GIT→cysticerci tissues)
    • Echinococcus (dog faeces ingested→hydatid cysts liver, etc) - see echinococcosis (hydatids)
    • Hymenolepis

Round worms (Nematodes):

  • No intermediate host
    • Direct infection
      • Enterobius (pinworm) - a major problem with school children
    • Soil maturation needed
      • Trichuris (whipworm) (caecum);
      • Ascaris (adult small bowel→larvae lungs)
      • Ancylostoma & Necator (hookworms) (skin→lung→duodenum)
      • Strongloides (skin→lung→GIT) - see strongyloidiasis
      • Toxocara
  • Intermediate host needed
    • Trichinella (rare pork→jejunal mucosa)
    • Anisakis (raw fish → GIT)
    • Dracunculus (ingested water flea → GIT → skin)
    • Angiostrongylus (eat snails→liver→heart/lungs/CNS) ⇒ angiostrongyliasis
      • most common cause of eosinophilic meningitis in SE Asia and Pacific Basin
    • filariae cause filariasis
      • Onchocerca volvulus
      • Onchocercidae Loa Loa
        • via biting deer flies and yellow flies
        • ⇒ Calabar swellings, itching, swelling in the eye
      • Wuchereria bancrofti
        • via mosquitoes
        • adult in lymph → pre-larvae blood/lung ⇒ elephantiasis)
      • Brugia
        • via mosquitoes
        • as for Wuchereria
      • Dirofilaria (dog “heartworm”)
        • via mosquitoes
        • die readily in human pulmonary artery branches ⇒ granuloma lung and may present as an incidental solitary lung lesions and nodules may also be found under skin, in brain, conjunctivae, as a breast lump, and in the testicle
        • D. immitis occurs globally including Australia (esp. temperate east coast ie. Qld, NSW) and USA; main host are dogs
        • D. repens, which is not found in the United States, is the leading cause of human dirofilariasis in Europe
        • D. tenuis host is raccoons
        • A review of cases of human dirofilariasis in the United States published in 2005 lists a total of 81 cases reported in the literature since 1941, the year of the first reported case 1)
      • Mansonella


parasites.txt · Last modified: 2023/11/20 04:29 by gary1

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