Microbiology Unit 8

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Microbiology Unit 8
2010-12-09 19:51:06
Chapter eighteen Paristology

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  1. Parasitic worms
    • called helminths
    • adult worms are large enough to see with the naked eye
    • ova and larve need microscope to view
    • 2 major groups: Nematodes (roundworm) and Cestodes (tapeworm)
  2. Nematodes (roundworm)
    • found in every habitat on earth --> sea, fresh water, soil, frutis, vegetables from polar regions to tropics
    • they parasitize every type of animal and plan causing economic damage and serious disease
    • structure: bodies are not segmented, but pointed at both ends; have complete digestive, excretory and nervous system; have seperate sex organs, and females may lay 200K eggs per day
    • worms includes: Necatur americanus, Ascaris lumbricoides, and Trichinella spiralis
  3. Necatur americanus
    • American hookworm
    • Transmission: larvae penetrates exposed skin then enter the circulatory system
    • Prevention: wear shoes, maintain proper sanitation for disposal of human waste
    • Disease: severe anemia, abdominal pain, diarrhea
    • Dx: Hookworms in O&P
    • Tx: Vermox
  4. Hookworm Life Cycle
  5. Dog and Cat hookworm
    • lifecycle is similar to human hookworms, but it cannot penetrate human skin.
    • it remains alive in the epidermis causing skin irritation called Creeping eruption or Ground itch
    • Dx: ID hookworm from stool speciman from the animal and look for eggs
    • Tx: Thiabendazole topical cream

    "Swimmer's Itch" is caused by goose feeces
  6. Ascaris lumricoides
    • largest of roundworms measuring 20-30 cm
    • life cycle is similar to hookworms
    • Transmission: enters the body via ingestion of eggs and travels to the lungs via circulatory system, patients cough up the larvae and swallow it and it gets to the digestive tract
    • Disease: severe pneumonitis, coughing, asthmatic breathing, diarrhea, vomiting, and abdominal pain
    • Dx: O&P exam of stool and look for Ascaris eggs
    • Tx: Vermox and look for passing of dead Ascaris in stool
  7. Trichinella spiralis
    • Transmission: eating infested bear or pork that has been undercooked
    • Prevention: cook meat thoroughly and never feed uncooked garbage to pigs
    • Life cycle: man is the alternate host
    • Disease: larvae is embedded in any muscle affecting heart, abdominal, tongue, biceps; the severity of disease depends on the number of viable larvae is eaten. Infection includes mild GI discomfort, muscle pain, chills, weakness, increase eosinophils over 40%. In severe infection-respiratory distress, heart involvement and death
    • Dx: muscle biopsy where the pain is, skin test, and increase eosinophils in WBCs
    • Tx: Thiabendazole

    • *muscle destruction is irreversible although new muscle cells will grow
    • *recovery begins when larval migration ends about 3-8 weeks
  8. Enterobius vermicularis
    • aka Pinworms
    • smallest parasitic roundworm and is the most common of all helminth infections
    • Transmission: ova on perianal skin of infected persons; direct or indirect transfer to others through clothing, bedding, toys, or food
    • Disease: anal scratching, itching, restlessness, insomnia
    • Dx: scotch tape or pinworm paddle pressed to the perianal area, exam for ova and parasites
    • Tx: Vermox and Piperazine
    • Prevention: Good hygeine, disinfect linens, toys, clothing