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MICRO 121 > Lecture 4: Approach to Understanding Parasites > Flashcards

Lecture 4: Approach to Understanding Parasites Flashcards

1
Q

What are parasitic organisms

A
  • Organisms that live on or in another organism (host) and derives a benefit and/or nutrients at the expense of the host
  • Acquired as a result of a bite (tick, mosquitoes); contaminated water, contaminated environment (bed bugs etc…) or contaminated food
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2
Q

2 types of parasites

A
  1. Exoparasite: lives on the host and causes an infestation
  2. Lives in the host and causes an infection
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3
Q

Examples of exo(ecto) parasites

A
  • Scabies
  • Body Louse
  • Head Lice
  • Pubic Lice (head lice)
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4
Q

2 Parasitic life cycles

A
  1. Direct Life Cycle
  2. Complex/indirect life cycle
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5
Q

What is the Direct Life Cycle

A

The entire lifecycle is completed in one host.
Control is easier.
Eggs often only viable for a short time in the environment.

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6
Q

What is the complex/indirect life cycle

A

The life cycle is completed in more than one host.
Control of the parasite is often much more difficult.
Examples include: Malaria, Lyme Disease

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7
Q

Classifying single celled parasites

A

Parasites -> Single celled -> Protozoa -> Intestinal or Blood and Tissue

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8
Q

Classifying multicellular parasites

A

Parasites -> Multicellular -> Helminths -> Cestodes (flatworms) or Trematodes (flukes) or Nematodes (roundworms)

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9
Q

Name all 5 Types of Protozoa: Intestinal Protozoa

A
  1. Entamoeba histolytica
  2. Giardia lamblia
  3. Cyclospora cayetanensis
  4. Dientamoeba fragilis
  5. Cryptosporidium parvum
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10
Q

Intestinal Protozoa: Entamoeba histolytica

A

Major pathogen associated with poor sanitation

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11
Q

Intestinal Protozoa: Giardia lamblia

A

“Beaver Fever” associated with contaminated H20

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12
Q

Intestinal Protozoa: Cyclospora cayetanensis

A

Contaminated water and produce exposed to contaminated water including raspberries, lettuce, fresh fruit, and vegetables.

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13
Q

Intestinal Protozoa: Dientamoeba fragilis

A

Ubiquitous and found in children worldwide. Transmitted person to person.

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14
Q

Intestinal Protozoa: Cryptosporidium parvum

A

Major outbreaks. Carried in cattle and other zoonosis. Can transmit human to human or from cattle.

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15
Q

Characteristics of Intestinal Protozoa

A
  • 500 million cases/yr worldwide
  • All of them have a direct lifecycle
  • Route of transmission is typically via contaminated H20, food, or soil (indirect contact) and zoonosis (direct contact)
  • Virulence factors include either production of toxins (watery diarrhea) or the ability to invade the GI epithelia (bloody diarrhea)
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16
Q

3 types of Protozoa: Blood/Tissue Protozoa

A
  1. Trichomonas vaginalis
  2. Plasmodium spp.
  3. Toxoplasma gondii
17
Q

Blood/Tissue Protozoa: Trichomonas vaginalis

A

2-3 million infections/yr. Common sexually transmitted infection. Diagnosis is via a wet-prep and antigen detection.

18
Q

Blood/Tissue Protozoa: Plasmodium spp.

A

Malaria ~ 3 million infections/yr. Transmission via anopheles mosquitoes.

19
Q

Blood/Tissue Protozoa: Toxoplasma gondii

A

~ 60% of cats are infected and can infect other invertebrates. Human infection as a result of exposure to cat feces or uncooked meat.

20
Q

What is Trichomonas vaginalis

A
  • One of the most common sexually transmitted infection
  • Most common complaint is vaginal discharge
  • May be associated with urinary frequency and dysuria - cystitis observed in a small proportion of women
21
Q

Malaria (Plasmodium spp.)

A
  • Has 5 species; P. faliciparum, P. malariae, P. knowlesi, P vivax, P. ovale
  • Over 3 million infections each yr, with almost a million deaths
  • Transmitted by mosquitos (indirect life cycle) - sexually mature in the mosquito and asexual states in human red blood cells
  • The mosquitos that transmit Malaria bite dusk to dawn so mosquito nets are other control measures work quite well
    Look on lecture slides for image about the lifecycle
22
Q

Lab diagnosis of Malaria Mechanisms

A
  • Microscopy
  • Molecular Detection
  • Protein Detection
23
Q

What is Protozoa: Toxoplasma gondii

A
  • Complex life cycle with multiple hosts and environmental maturation
  • Humans and other mammals are dead end hosts (doesn’t get transmitted onwards)
  • Asymptomatic infections in immunocompetent hosts
  • Serious clinical manifestations if acute infection during pregnancy - infects the baby in utero and lead to significant morbidity to the baby including deafness, microcephaly, meningitis, encephalitis, hydrocephalus, retinitis and even death
24
Q

3 Types of Helminths: Cestodes (Tapeworms)

A
  1. Diphyllobothrium latum (fish)
  2. Tinea solium (pork)
  3. Tinea saginata (beef)
25
Q

Cestodes: Taenea solium (Pork tapeworm)

A
  • Multiple hosts
  • Human gets teniasis is contaminated meat is ingested
  • In the case of tinea solium - if the eggs in feces are ingested by humans they can migrate to different tissues including the eye, brain (neurocysticercosis), muscle and bone
    (reason why some cultures won’t eat pork)
26
Q

Cestodes: Taenea saginata (Beef tapeworm)

A
  • Multiple hosts***** BIG DIFF.
  • Human get Tenaisis if they ingest contaminated meat or are exposed to cattle faecal matter
  • Does not develop tissue phase disease
27
Q

Cestodes: Diphyllobothrium latum (Fish tapeworm)

A
  • This is why you don’t fish out of Lake Ontario
  • Complex life cycles with multiple hosts
  • Crustaceans, fish, and humans
  • Humans can transmit
  • Can live outside a host in water
    • But always looking for a host
28
Q

3 types Helminths: Nematodes (Round worms)

A
  1. Ascaris lumbricoides
  2. Enterobius vermacularis
  3. Strongyloides stercoralaris
29
Q

Helminths Nematodes (Round worms): Ascaris lumbricoides

A
  • Contaminated food/water ingestion of eggs
  • Largest worm, very rare
  • Almost 1 billion people infected worldwide
  • Eggs have to mature in the environment or several days
  • Life of the worm is between 10 months and 2 years
  • Sometimes they get lost
  • You can have multiple worms
  • It cannot reinfect you or transmit
  • You swallow them, reach gut, they hatch, they migrate into the lungs, keeps coming up because it wants to be reswallowed
30
Q

Helminths Nematodes (Round worms): Enterobius vermacularis

A
  • Females come out at night lay their eggs outside the anus - very itchy
  • Very common
  • Transmission is from person to person via contaminated surfaces
  • Often in day care centres
  • Most common worm infection in North America
  • Leads to intense anal itching and often is passed on person via faecal matter (after they itch their bum)
31
Q

Helminths Nematodes (Roundworms): Strongyloides stercoralaris

A
  • Very serious/most severe
  • Contact with the environment
  • Free larval forms found in contaminated soil
  • Single cycle with only ONE host
  • Can be free living
  • Found in warm climates with beaches
  • Symptoms of infections include dermatitis, swelling, itching, larva currens
  • Immunocompromised individuals - can develop a hyper-infective syndrome - associated with 90% mortality
  • The worm can cause autoinfection so can continue a cycle of infection for over 30 yrs
32
Q

Name 2 types of Helminths: Trematodes

A
  1. Shistosoma species (blood flukes)
  2. Clonorchis sinensis (chinese liver fluke)
33
Q

Trematodes: Shistosoma spp.

A
  • Complex life cycle with > 1 host
  • Includes an environmental stage with an intermediate host
  • Found in tropical to semi tropical waters
  • Burrow into the skin of humans when in contact with contaminated water
  • Can be ingested
    • One to bladder
    • Other goes to gut
34
Q

Trematodes: Clonorchis spp.

A
  • Complex life cycle > 1 host
  • Includes an environmental stage with an intermediate host
  • Found in tropical to semi tropical waters
  • Result of ingestion of contaminated or infected fish
  • Easily treated

MICRO 121 (19 decks)

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