see also:

• microbiology
• zoonoses
• Antihelminths
• the febrile returned traveller
• could some helminths be good for you?

• NB. unicellular or acellular animals (eucaryotic);
• sarcomastigophora (motile elements)
  • amoebae (pseudopods)
    • Entamoeba (anaerobe) - causes amoebiasis
    • Naegleria (aerobe) - may cause meningitis from thermal baths
    • Hartmanella (aerobe) - may cause meningitis from thermal baths
  • flagellates (flagella)
    • intestinal
      • Trichomonas eg. Trichomonas vaginalis - a cause of sexually transmitted infections (STDs/STIs)
      • Giardia may cause gastroenteritis, see giardiasis
    • visceral/blood
      • Trypanosoma - Trypanosoma brucei causes sleeping sickness; Trypanosoma cruzi causes Chagas disease
      • Leishmania - may cause cutaneous lesions from sandfly bites
• 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

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

• 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

• 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
  • Eustrongylidosis
    • caused by three species of Eustrongylides: E. ignotus, E. tubifex, and E. excisus
    • E. excisus “red-worm-of-trout” has recently been found in NSW, southern Qld and Victoria
      • infects an invertebrate in fresh water, which is then eaten by a fish which becomes infected which can then infect a bird or other animal which eats the fish
      • can infect humans (rare and gastric acids will generally prevent infection) and other mammals (eg. pets) when they eat uncooked or undercooked fish caught in fresh water and can be lethal to some animals
  • Baylisascariasis
    • Baylisascaris procyonis raccoon roundworm, an increasing problem in Europe - causes permanent blindness in humans, although only 3 cases recorded to 2025 ¹⁾
  • filariae cause filariasis
    • Onchocerca volvulus
      • via biting black fly
      • skin itch ⇒LN ⇒“river blindness” see onchocerciasis / river blindness
    • 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 ²⁾
    • Mansonella

• insects that attach or burrow into the skin and remain there for relatively long periods of time (e.g., weeks to months) such as:
  • ticks in Australia
  • fleas
  • human louse / lice
  • scabies and other mites