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MicroBio > Dr. Zhou - Lecture 20 > Flashcards

Dr. Zhou - Lecture 20 Flashcards

1
Q

Helminths

A

Worms

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2
Q

Constitutional symptoms

A

a group of symptoms characteristic to a disease, effecting many different body systems
Ex: weight loss, fevers, idiopathic fevers, hyprehidrosis, chronic pain, fatigue, dyspnea, etc

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3
Q

Trichinosis is caused by:

A
  • Any species of Trichinella parasite

- In artic bear + walrus meat, most common species: T. nativa

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4
Q

General features of a helminth

A
  • Helminth = worm
  • Usually large (0.3 mm-25m)
  • Grotesque:
  • squirming white worms coming out of nose; feeling and seeing a worm creep beneath your skin; slither across your eye
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5
Q

Categories of helminth

A
  • Nematodes: roundworms
  • Trematodes: flukes
  • Cestodes: tapeworms (huge, long; infects intestines of pts or animals)
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6
Q

helminth Life and Transmission Cycles

A

A COMPLETE life cycle:
- Fertilized egg (embryo) –> larva –> adult

Some worms have:

  • Intermediate (2ndary) host: where larval development
  • Definitive (final) host: adulthood + mating

SEXUAL reproduction

  • separate sexes: nematodes
  • Separate or hemaphroditic: trematodes
  • Hermaphroditic: Cestodes
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7
Q

Basic Helminth Life Cycles - Source of Infection, Route of Infection, # life cycles

A

Source:

  • Contaminated food
  • Soil, water
  • Infected animals

Route:

  • PO
  • Skin penetration

5 basic life cycles

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8
Q

Cycle A

A
  • Source: food + water contaminated w/ mature eggs
  • Route: PO
  • Human eats contaminated food/water –> Larva hatches in tissues –> travels to intestines to mature + mate
  • Embryonic eggs are then released back into environment
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9
Q

Cycle B

A
  • Source: contaminated soil or other environment contact
  • Route: Skin penetration
  • Eggs + larvae mature in environment instead of host to allow skin penetration
  • Larvae migrates to intestines to mature + mate –> eggs released back into environment
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10
Q

Cycle C

A
  • Source: Contaminated meat
  • Route: PO
  • Person eats contaminated livestock (host 1) –> Cyst formation in muscle/gut of host 2 –> larva released in digestive tract –> travel to intestines to mature + mate
  • Eggs released back into environment
  • Eggs taken up by livestock again (host 1)
    3 settings
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11
Q

Cycle D

A

2 Routes/Source: Contaminated meat OR direct skin penetartion

  • Parasite travels into intestines of bladder –> mature + mate to make eggs (1)
  • Eggs released into environment (2) –> eggs develop into 1st larva stage –> infect intermediate (2ndary) host (3) –> 2nd larva stage development
  • 2nd stage larva can infect via infected meat or direct skin penetration
  • More complicated
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12
Q

Cycle E

A
  • Source: Insect bites
  • Route: skin penetration
  • Infected larva gets lodged in tissues
  • New larva released into circulation, ready to be transferred into insects + new hosts

Humans + insects

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13
Q

Epidemiology

A

Large # infections:
- # worm infections > # humans

Kids in rural tropics/subtropics

  • Schistosomiasis
  • Filariasis
  • Hookworm diseases
  • Ascariasis
  • Oncocerciasis

In developed nations:
- Pinworm and trichinosis

Continuing infection :
- Unprocessed sewage as fertilizer, eating raw fish/meat, exposing bare feet in contaminated soil/water

Pts can get infected mult times

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14
Q

Helminth infection patho

A

Symptoms:

  • Organ enlargement
  • Hemorrhage
  • Weight loss
  • Anemia

Worms migrate w/ enzymes to liquefy + penetrate tissues: feeding, tissue damage (=inflamm), blocked ducts + organs, toxic secretions (growing mass of worms block lymphatic ducts), pressure

Host immunity incomplete bc worms often have: protective coverings, large, inaccessible to immune system attacks, and migration

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15
Q

Helminth Diagnosis (3)

A
  • Eosinophilia: increase # of eosinophils (granular leukocytes that destroy worms)
  • Travel history
  • Detecting eggs in stool, urine, or blood
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16
Q

Major Helminth Infections

A

I: Nematode (roundworm infections)

  • Headless worms w/ smooth, protective outer cuticle, periodically shedding as worm grows
  • Distinct sexes (female vs. male worms)
  • One of the most abundant animal groups
  • Most are NOT parasites
  • 50 species –> human parasites
  • 2 types (based on infection site + maturation):
  • Intestinal nematodes
  • Tissue nematodes
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17
Q

I-1: Intestinal Nematodes - Cycla A

A
  • Cycle A
  • Ascaris Lumbricoides (A. Lumbricoides) causes Ascariasis
    *300 mm long (~1ft)
    *1 Billion infections
    *in US: mostly in southern states
  • Life cycle:
    Larva + adult in humans –> embryonic eggs in feces –> contaminates food –> Eaten –> intestines –> circulation –> heart –> lungs –> throat –> swallowed –> small intestine –> 200,000 embryos/day/worm
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18
Q

A. lumbricoides

A
  • Worms keep motility, do not attach
  • Severe inflamm rxns mark on skin on migratory route
  • Allergic rxns can happen
  • Heavy worm loads can retard physcial + mental development
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19
Q

I-2: Intestinal Nematodes

A
  • Cycle B
  • I-2-1: hookworms - larvae burrowing into skin –> circulation –> lung –> throat –> small intestine (similar to A except route of entry)
  • Small hook-like tails, teeth to anchor into intestines
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20
Q

I-2-1 symptoms

A
  • Dermatitis (ground itch)
    Pneumonia
  • NV, pain, bloody diarrhea
  • Chronic fatigue, anemia
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21
Q

I-2-2

A

Strongyloidiasis

  • Threadworm (aka Pinworm) infections
  • 100-200 mill pts worldwide
  • Threadlike inflamma marks on skin
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22
Q

I-2-2 Symptoms

A
  • Bloody diarrhea
  • Liver enlargement
  • Bowel obstruction
  • Malabsorption
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23
Q

I-2-3

A
  • Trichinella spiralis (T. spiralis) causes Trichinosis
  • Mammalian hosts
  • Encysted larval form in muscles
  • Human infections source: raw meat from pig or bear
  • US: few new cases/yr
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24
Q

I-2-3 Symptoms

A

Initially:

  • Fever
  • Diarrhea
  • Nausea
  • Abdominal pain
  • Sweating
2nd phase:
- Intense muscle + joint pain
- SOB
- Eosinophilia
Leading to heart + brain damage and death (if untreated)
25
Q

I-2-3 Prevention:

A
  • Cook meat well
  • Freezing also kills worm larvae (T. spirolus in pork also) but NOT for Alaska variant (T. nativa) since they’re used ot the cold
26
Q

T. nativa

A
  • in Alaska bear + walrus meat
  • Cold-resistant
  • Freezing will NOT kill larva cysts
  • Bear + walrus meat are safe once entire piece of meat is completely cooked to a GRAY color
  • USDA: internal temp of at least 160 degrees F
  • Microwaving may not make food safe bc of uneven cooking
27
Q

I-3: Tissue nematodes

I-3-1

A

I-3-1: Filarial nematodes; filariasis

  • Cycle E
  • Long threadlike worms
  • BIPHASIC life cycle: alternating btwn humans + mosquitos/flies
  • 2 MAJOR species:
  • Wuchereria bancrofti (W. bancrofti)
  • Onconcerca volvulus (O. volvulus)
28
Q

I-3-2

A
  • Disease: Bancroftian filariasis
  • W. bancrofti (long threadlike worm)
  • Affects 120 mill
  • Symptoms: elephantiasis - inflamm + blockage of main lymph channels –> fluid accumulation
29
Q

I-3-3

A
  • River blindness: invasion of eyes
  • West African villages along rivers: 50% adults blind
  • Breeding sites for black flies
  • O. volvulus
  • Onchocerciasis: inflamm, granulomatous lesions; river blindness
30
Q

I-3-4:

A
  • Loa Loa: African eye worm
  • Transmitted by fly
  • Can be felt slithering beneath skin
31
Q

I-3-4 Treatment

A
  • Pull worm out

- Diethylcarbamazine

32
Q

I-3-5

A
  • Dracunculus medinensis (D. medinensis): Dragon worm
  • Disease: dracontiasis
  • India, Middle East, Central Africa
  • Cyclops: arthropod in still water

Infection cycle:
Ingestion of larva in cyclops –> intestine –> SQ tissue –> irritants released –> itching blisters (fireworm) –> blisters erupt in water –> cyclops released

33
Q

II. Trematodes/Flukes

A

Fluke: mostly flat (flatworms)

2nd major category of worms

34
Q

II-1

A

Blood flukes: the Schistosomes

  • Cycle D
  • Infection: Old disease - ancient Egyptians observed males “mensturating” –> kidney schistosomiasis
  • Overall 200 mill infections in world (Africa, South America, middle East, Far East)
35
Q

Blood Fluke Symptoms

A

Symptoms:

  • Fever
  • Chills
  • Diarrhea
  • Cough

Chronic infections:

  • Hepatomegaly (liver enlargement)
  • Splenomegaly (spleen enlargement)
  • Bladder obstruction
  • Kidney damage
  • Bloody urine
  • Brain damage
36
Q

Blood Fluke Life-Cycle and Control

A

Life Cycle:
Infected humans –> eggs released from host to environment –> develop into ciliated larva (miracidium) –> snails infected (1st host) –> forked larva (cercaria) –> penetrating human skin –> circulation –> liver –> intestine (mature+mate+make more eggs) –> feces (released into environ
- Males + females are intertwined FOR LIFE to facilitate mating + reproduction

Control: Snail-eating fish

37
Q

II-2: Liver and Lung Flukes (cycle, reproduction, hosts, sources of infection, body location)

A
  • Cycle D
  • Develop in liver or lung
  • Sexual development in humans
  • Intermediate (2ndary) hosts: snails
  • Infection caused by ingesting not fully cooked or raw freshwater fish + crustaceans
  • Hemaphroditic
38
Q

II-2 Life Cycle

A

Hatched larva –> cross into bile duct and grows+matures –> shed eggs into intestinal tract –> releasing into feces in standing water –> taken up by snails –> cercariae –> infect fish

39
Q

III: Cestode/Tapeworm Infections (cycle, morphology)

A
  • Cycle C
  • Usually very long
  • Hermaphroditic
    Morphology:
  • Scolex: head - sucker, NO MOUTH
  • Neck
  • Strobila: ribbon made up of reproductive segments (prolgottids)
40
Q

Beef Tapeworm

A
  • Taenia saginata (T. saginata)
  • Disease: Taeniasis
  • 2000 proglottids anchored by a scolex w/ suckers per T. saginata
  • Worldwide
  • Cows infected by eating in fields w/ proglottids or eggs contamination
  • Human infection source: eating raw beef

Symptoms:

  • Mild abdominal pain
  • Nausea
41
Q

Beef Tapeworm life cycle

A

Eggs eaten by cows –> ecysted larva (cysticercus) in grow in beef muscle –> human eats contaminated undercooked meat –> develop into proglottids –> released in feces into environment

42
Q

Swine Tapeworm

A 
Taenia solium (T. solium)
- SAMLLER than T. saginata
  • Endemic in areas eating raw or partially cooked pork (Southeast Asia, South America, Mexico, Eastern Europe)
  • Disease: Cysticercosis: severe form of T. solium infection
43
Q

Cysticercosis

A
  • Severe form of T. Solium infection
  • Tapeworm larvae migrate to different tissues
  • Form peculiar cysticerci
  • Tissue damage: heart, brain, eye
  • Caused by raw/partilally cooked pork, undercooked fish
44
Q

Worms in my Sushi?

A
  • Yes: fish helminths

Anisakis –> anisakiasis

  • Tingling feeling in throat a few hrs after eating sushi or sashimi
  • Anisakis try burrowing into tissue
  • Acute GI pain, cramping, and vomiting
  • Expelled w/o further symptoms (NO MAJOR SYMPTOMS)

Tape worm D. latum

  • Great lakes region, Canada, Alaska
  • Humans are DEFINITIVE hosts
  • Lasting infection + damage

What to do if you like sushi:

  • Reputable sushi bar: chef picks out larvae
  • Have tuna + octopus (not so much); avoid salmon + halibut (more likely to have fish worms)
  • Freeze fish for 5 days at -20 degrees C
45
Q

Controlling Helminth infections (Prevention and Treatment)

A

Prevention - Sewage treatment:

  • No human feces as fertilizers
  • Water treatment
  • No raw meat

Treatment: Chemo (2 mechs)

  • Paralyze worms
  • Interfere w/ metabolism (toxic to worms)
46
Q

Ascariasis Treatment:

A
  • Piperazine
  • Pyrantel
  • Mebendazole
47
Q

Pinworm Treatment

A
  • Piperazine

- Pyrantel

48
Q

Hookworm Treatment

A
  • Piperazine
  • Pyyrantel
  • Mebendazole
  • Thiabendazole
49
Q

Trichinosis Treatment

A
  • Pyrantel
  • Mebendazole
  • Thiabendazole
50
Q

Trichuriasis (whipworm) Treatment

A

Mebendazole

51
Q

Stronglyoidiasis Treatment

A

Thiabendazole

52
Q

Guinea worm Treatment

A

Thiabendazole

53
Q

Echinococciasis Treatment

A

Albendazole

54
Q

Filariasis Treatment

A

-Diethylcarbamazine

55
Q

Loiasis Treatment

A

Diethylcarbamazine

56
Q

Schistosomiasis Treatment

A
  • Niridazole
  • Praziquantel
  • Metrifonate
57
Q

Tapeworm Treatment

A

Praziquantel

58
Q

Other flukes Treatment

A

Praziquantel

MicroBio (3 decks)

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