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PATHOLOGY > worms > Flashcards

worms Flashcards

1
Q

in general, do worms cause damage

A

no - as long as adapted to be in you

when damage happens it can be:
* slow - worm/progeny tries to escape -> get trapped -> inflammation (eg schisto in bladder)
* rapid parasite mediated damage - tissue damage as humans not natural host - parasite and human die

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2
Q

types of helminth

A

cestodes (tape worms) - not a human worm

trematodes (flukes)

nematodes (round worms)

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3
Q

types of cestodes

A

hydatid

pork/beef/fish tape worm

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4
Q

types of trematodes

A

lung, liver, intestinal - not very common in UK

blood - schistosoma

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5
Q

types of nematodes

A

hookworms

ascarids

strongyloides

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6
Q

summarise cestodes

A
flat and long
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7
Q

summarise trematodes

A
unsegmented
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8
Q

summarise nematodes

A
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9
Q
A

Top L - ascaris - round worm - common world wide - 1 million effected

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10
Q
A

tape worm

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11
Q
A

fluke

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12
Q

structure of tapeworms

A

Head
Some have hookers/hooks - attach to wall of bowel

Neck - where segments spring from - grow and grow until have long warm
Each segment has pair of uteri - pumping out eggs

Old segments fall off - see in stool - this is what cause sx

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13
Q

life cycle of a pork and beef tapeworm

A

Definitive host is man - tapeworms of man

Pig and cow are intermediate host:
1. eat eggs passed by human
2. go into animal
3. -> cyst
4. Man eats uncooked beef/pork
5. - > cyst open
6. -> tapeworm

Cysticercosis - when human is accidental intermediate host - ie pig in cycle

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14
Q
A

taenia segment and egg

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15
Q
A

segments are independently motile

water cloudy - full of eggs

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16
Q
A

Beef - cysts in meat - proteosclorsis?

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17
Q
A

Human tapeworms

  • so food contaminated by human poo -> cysticercosis
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18
Q
A

Cysticercosis

See worm head in cyst

If eaten - bubble break down - tape worm released

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19
Q

summarise hydatid

A

not a human worm

dogs and foxes are definitive host - never know infected

humans are accidental intermediate host
sheep and goats are intentional intermediate

if humans eat eggs from food contaminated by dog faeces
* cyst in human
* -> disease in human
* -> complications from mass effect/cyst rupture

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20
Q
A

Carcass of sheep

Bubbles are cysts in cysticercosis

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21
Q
A

hydatid

22
Q

treatment and of cestodes

A

easy

Praziquantel for human tape worms

Praziquantel for dogs (Echinococcus)

23
Q

treatment of cestode cysts

A

difficult

Hydatid: drugs don’t penetrate
* PAIR - needle into cyst, inject ?alcohol and take it out
* Surgery,
* long term albendazole, praziquantel

Cysticercosis: dying worms cause trouble - Ruptured cyst -> spread/anaphylaxis - content of cyst is parasitic and hidden by the immune system
* Albendazole, praziquantel
* STEROIDS.

24
Q

prevention of cestodes

A

Hygiene,

de-worm dogs,

cull foxes.

25
Q

diagnosis of cestodes

A

imaging - see cyst

serology - measure specific IgG

26
Q

epidemiology of schistosomiasis

A

Probably the most common imported non-GI helminth

4 species, found in Africa, SE Asia and South / Central America (Brazil)

27
Q

life cycle of schistosomiasis

A
  1. Cercariae invade human skin when in contact with contaminated water.
  2. Worms develop in venous plexus -male and female flukes, live together 20-30yrs

Adult schistosomes lay eggs:
* Migration of eggs through bladder or bowel causes damage
* Retrograde passage of eggs into the liver causes “cirrhosis”

  1. Eggs excreted in faeces or urine
  2. Hatch into miracidia, which parasitise snails
  3. Snails release cercariae
28
Q

damage caused by schisto eggs

A

Bladder cancer

Fibrosis of bladder that is precancerous -> transitional ca

Retropulsion back into liver -> look like cirrhosis

29
Q

diagnosis of schistosomiasis

A

Microscopy:
* Urine (last drops of urine - most infected): S. haematobium (migrate through bladder)
* Stool: S. mansoni, S. japonicum

Serology - Ab

Biopsy - liver/labial granuloma

Response to treatment (not in the UK)

30
Q

treatment of schistosomiasis

A

Is very easy: praziquantel

may need empirial rx in endemic countries

31
Q

prevention of schistosomiasis

A

break life cycle:

  • Kill snails
  • Destroy snail habitat
  • Mass treatment
  • Interrupt transmission: no swimming, no washing etc
32
Q

what are the soil transmitted helminths

A

Very well adapted to humans and cause little pathology

3 main pathogens are:

  • Ascaris lumbricoides – ingested with food
  • Trichuris trichiura – ingested with food
  • Hookworm – transdermal infection
  • Plus: Strongyloides stercoralis – transdermal infection
33
Q

How do soil transmitted helminths cause disease

A

dont cause many sx other than malabsorption - most people dont know infected

Migration (ascaris, hookworm and strongyloides)

Intestinal obstruction (ascaris) - If have a lot of worms - bowel not work as well - intestinal obstruction, up bile duct -> colic/cholangitis

Malabsorption and blood loss (all of them)

rectal prolapse

Psychological distress

34
Q

basic life cycle of soil transmitted helminths

A
  1. Adults lay eggs,
  2. eggs in stiool,
  3. contaminate food,
  4. people ieat them
    • larvae migrate until lungs
    • cough up
    • swallow
    • mature into adult worms
Eggs swallowed with food - hatch in stomach - migrate - find way back to duodenum - mature
35
Q

life cycle of strongyloides

A

The only helminth capable of autoinfection

Therefore worm burden not related to infectious dose

Lifecycle:
1. Larvae invade skin
2. Mature into adult pinworms in the small bowel
3. Eggs produced,
4. hatch into rhabtidiform larvae
5. These mature into filariform larvae (infectious)
6. These can autoinfect via perianal skin

ie it is larvae, not eggs in stool - can pass into env to mature, or mature before even get into the stool

adult worms dont die as fast as replaced -> hyperinfestation

if biopsy gut - full of adult worms

36
Q

how does strongiolides cause damage

A

Hyperinfection
Larva currens
Malabsorption etc
Generally asymptomatic

37
Q

how does strongiolides cause damage

A

Hyperinfection
Larva currens
Malabsorption etc
Generally asymptomatic

38
Q

treatment of strongiolides

A

ivermectin

39
Q

prevention of strongyloides

A

hygiene

40
Q

what is filariasis

A

variety of nematode infections

spread by blackflies and mosquitoes

Divided according to where the adult worm lives
* Lymphatic filariasis (Wuchereria, Brugia)
* Subcutaneous filariasis (Onchocerciasis, Mansonella, Loa loa)
* Serous cavity filariasis (Mansonella, Dirofilaria)

41
Q

what diseases does filariasis cause

A

Adult worms:
* lymphatic filariasis (elephantiasis, scrotal swelling)
* oncho (nodules)

Microfilariae:
* Onchocerciasis (depigmentation, river blindness)

42
Q

life cycle of filiarisis

A

Adult worms release larvae (microfilariae) taken up by vector (mosquito)

Larvae can only mature if taken up by vector

mature and then injected into next victim

43
Q

how is filariasis diagnosed

A

Find microfilariae (blood film examination, skin snips)

Find antibodies against adult worm (ELISA, IFAT)

Find adults (US over lymphatics – “dance sign”, Loa Loa migration)

44
Q
A

lymphatic filariasis (elephantiasis)

Doesn’t imply active infection - scarred lymphatics which may or may not have adult worms

45
Q

summarise myiasis

A

Parasitisation of human flesh by fly larvae

Very common in some areas

Occasionally imported

Mainly:
* Bot (S. america) and
* Tumbu (Africa) - lays eggs on washing - if don’t iron - human warm hatch and lie on skin

Local damage as the maggot eats necrotic flesh

46
Q

treatment of myiasis

A

removal of larva by asphyxiation or surgery

Highly motile maggot

Cover with vaseline and it will pop out looking for oxygen

Bot fly might need surgery - harder to get out

Bot nad tumbi can infect healthy

47
Q

causes of eosinophilia (>0.5)

A

Atopy - most common cause in UK
Drug allergies
Some forms of malignancy
* Hodgkin’s lymphoma
* Some forms of Non-Hodgkin lymphoma
Systemic autoimmune diseases (e.g. SLE)
Some forms of vasculitis (e.g. Churg-Strauss syndrome)
Cholesterol embolism (transiently)

BUT DON’T FORGET PARASITES
Soil transmitted helminths esp. strongyloides (stool culture/Ab)
Schistosomiasis (africa)
Filaria (africa and far east)
Leaking hydatid cysts

48
Q
A

Ascaris - doesn’t like being hot
Ascaris - so comes out

Trematode

49
Q
A

Hookworm

dog hookworm in human foot

dog worm cant find way in human - cant get to lungs, stay in foot

50
Q
A

A

Hydatid cyst
Serology test -ve - they are -ve in 25%

So made hole in cyst - leaked - anaphylaxis - AE

51
Q
A

worm in wrist

Loa loa

Filarises- more benign - adults live in subcut tissue -> calibar swelling whereever they go
Migrate w/o causing damage - left eye before seeked med attention for it

PATHOLOGY (94 decks)

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