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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
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
diagnosis of cestodes
imaging - see cyst serology - measure specific IgG
26
epidemiology of schistosomiasis
Probably the most common imported non-GI helminth 4 species, found in **Africa**, SE Asia and South / Central America (Brazil)
27
life cycle of schistosomiasis
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”** 3. **Eggs excreted in faeces or urine** 4. **Hatch** into miracidia, which **parasitise snails** 5. Snails release cercariae
28
damage caused by schisto eggs
Bladder cancer Fibrosis of bladder that is precancerous -> transitional ca Retropulsion back into liver -> look like cirrhosis
29
diagnosis of schistosomiasis
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
treatment of schistosomiasis
Is very easy: **praziquantel** may need empirial rx in endemic countries
31
prevention of schistosomiasis
break life cycle: * Kill snails * Destroy snail habitat * Mass treatment * Interrupt transmission: no swimming, no washing etc
32
what are the soil transmitted helminths
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
How do soil transmitted helminths cause disease
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
basic life cycle of soil transmitted helminths
1. Adults lay eggs, 2. eggs in stiool, 3. contaminate food, 4. people ieat them 5. - larvae migrate until lungs 6. - cough up 7. - swallow 8. - mature into adult worms
35
life cycle of strongyloides
*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
how does strongiolides cause damage
Hyperinfection Larva currens Malabsorption etc Generally asymptomatic
37
how does strongiolides cause damage
Hyperinfection Larva currens Malabsorption etc Generally asymptomatic
38
treatment of strongiolides
ivermectin
39
prevention of strongyloides
hygiene
40
what is filariasis
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
what diseases does filariasis cause
Adult worms: * lymphatic filariasis (elephantiasis, scrotal swelling) * oncho (nodules) Microfilariae: * Onchocerciasis (depigmentation, river blindness)
42
life cycle of filiarisis
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
how is filariasis diagnosed
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
lymphatic filariasis (elephantiasis) Doesn’t imply active infection - scarred lymphatics which may or may not have adult worms
45
summarise myiasis
**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
treatment of myiasis
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
causes of eosinophilia (>0.5)
**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
Ascaris - doesn’t like being hot Ascaris - so comes out **Trematode**
49
**Hookworm** dog hookworm in human foot dog worm cant find way in human - cant get to lungs, stay in foot
50
A Hydatid cyst Serology test -ve - they are -ve in 25% So made hole in cyst - leaked - anaphylaxis - AE
51
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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