Lecture 4

• Parasitic organisms

  organisms that either live on OR in another organism (a host). Will gain something at the loss of the host. Obtained by bites, contaminated waters/environment, food
• Exoparasite

  live ON the host and causes infestation (head lice, body louse, pubic lice)
• Ectoparasite

  live inside the host and causes infection (tapeworm, botfly, scabies)
• How many people are infected?

  3 out of 8 people are most likely infected. more than 832 million deaths
• Direct lifecycle


  easier to control, eggs of parasite is only able to live for small amount of time. If transmission is interrupted then parasite is lost and dies. Has only one host and will die with said host
• Complex/indirect lifecycle

  harder to control. Malarie, lyme disease. Harder to interrupt as there are multiple organisms that are infected. Completes life with more than one host
• Protozoa?

  single celled parasites (intestinal and blood & tissue)
• Helminths

  multicellular parasites, cestodes (flatworms), nematodes (roundworms), trematodes (flukes)
• Examples of protozoa?

  Entamoeba histolytica (poor sanitation)

  Giardia Lamblia (contaminated water, get best poop tho)

  Cyclospora cayetanensis (produce exposed to contaminated water)

  Dientamoeba fragilis (fecal exposure to oral)

  Cryptosporidium parvum (cattle and zoonosis)
• Intestinal protozoa

  500 million cases/year

  all have direct lifecycle

  normally from contaminated water

  virulene factors = produciton of toxins (watery diarrhea) or ability to invade GI epithelia (bloody diarrhea)
• Blood/tissue protozoa

  Trichomonas vaginalis (2-3 million/year, increase risks of getting STI, discharge)

  Plasmodium spp. (malaria, 3 million/year. caught by anopheles mosquitoes)

  toxoplasma gondii (60% of cats have this and can infect other vertebraes (cat poop and uncooked meat is bad)
• Plasmodium spp.

  reproduction takes 24 hours (penetrating blood cells, dividing, etc)

  
• laboratory diagnosis of malaria?

  Microscopy, protein detection, molecular detection (may take multiple tries)
• toxoplasma gondii

  complex lifecycle

  • environmental maturation
  • humans and other mammals are dead ends, cannot be passed on by them
  • infection during pregnancy is BAD (baby is infected and can develop disabilities
• Helminths: cestodes

  tape worms, grow up to 40ft

  • Diphyllobothrium lactum (eggs from fish generate in stomach, multiple hosts, infects crustaceans fish and humans)
  • Tinea solium (from pigs and leads to either teniasis or brain infection after infecting tissues and migrating)
  • Tinea saginata (from cattle, multiple hosts, humans get teniasis from contaminated meat, exposure to poop, do not get tissue phase)
• Helminths: Nematodes (roundworms)

  Ascaris lumbricoides (contaminated food, water, eating eggs. the eggs need to mature for a few days,live between 10 months - 2years, ~1 billion infected)

  Enterobius vermacularis (pinworm, passed by people via contaminated surfaces, live in butthole and females come out at night to lay eggs)

  stronglyoides stercoralaris (contact with environment, free larval forms in soil, simple cycle, causes death, continue its infection for over 30 years)
• Helminths: Trematodes (Flukes)

  Shistosoma species (blood flukes, complex lifecycle, environmental stage with first host then can burrows into human skin when it contacts contaminated water)

  Clonorchis sinensis (chinese liver fluke, complex lifecycle, from ingestion of contaminated or infected fish)
• Lab detection of parasites

  intestinal parasites: stool specimen in preservatives to keep parasite structure

  tissue and blood: antobody detection and biopsy (collect blood sample)

  *when positive, will stay positive for long time