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Management of Infection > Lecture 3B - Worms > Flashcards

Lecture 3B - Worms Flashcards

1
Q

What are worms?

A

highly developed multicellular organisms which generally replicate outside of the human host (through the shedding of eggs typically in faeces)

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2
Q

What do worms that are parasitic in humans lead to?

A

great suffering on a global scale because they are hard to treat

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3
Q

Classes of worms?

A

roundworms (4,500 million infections globally)

tapeworms (175 million)

trematodes (250 million)

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4
Q

What do worms rely on the body for?

A

nutrition of the parasite at early stages of its life cycle

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5
Q

Where does the ascaris roundworm have an adult stage?

A

in the gut, which can shed eggs into the faeces

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6
Q

What happens to the ascaris worm eggs outside the gut?

A

they are fertilised and the embryonic form of the parasite is reingested

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7
Q

Where do the larvae of the ascaris worm go?

A

they hatch from the eggs inside the gut, they break through the gut wall and migrate through the blood stream to the lungs

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8
Q

What happens to the larvae once in the lungs?

A

the developing larvae are coughed up and swallowed, gain to reinfect the gut and grow to adult hood

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9
Q

Why do worms go to the lungs?

A

because of the very fine capillaries

they go via the hepatic portal vein because the blood from the gut goes there

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10
Q

What are roundworms known as?

A

nematodes

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11
Q

Intestinal nematodes?

A

often cause diarrhoea, itch and anaemia

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12
Q

How are intestinal nematodes acquired?

A

orally or through skin, transmitted by faeces

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13
Q

Strongyloids?

A

threadworm - can migrate to lungs

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14
Q

Trichuris?

A

whipworm - transmitted via the soil, if human faeces is used asa fertiliser and food isnt cleaned

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15
Q

Ascaris?

A

roundworm

migrates to liver, heart, lung and back to gut

some patients carry 1000+ worms, females worms can lay 200,000 eggs daily

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16
Q

Enterobius?

A

pinworm

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17
Q

Necator and ancylostoma?

A

hookworms - larvae can penetrate bare feet

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18
Q

Trichostrongylus?

A

mild intestinal symptoms but very common

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19
Q

Extraintestinal nematodes?

A

trichinella (trichinosis) and dracunulus (guinea worm)

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20
Q

Trichinella?

A

present in infectedmear, cysts in muscle

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21
Q

Dracunculus?

A

can grow up to one metre long in the skin

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22
Q

Larva migrans?

A

disease eruption can occur in a variety of tissues when invaded by larvae of roundworms

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23
Q

What are nemathelminthes?

A

roundworms which include the nematodes - includes roundworms like ascaris

24
Q

What are platyhelminthes?

A

all flatworms

25
What are platyhelminthes divided into?
the cestoda (tapeworms like taenia) the trematodes (flukes like sheep liver fluke)
26
What are extraintestinal nematodes?
thread like wormsn, 200-300microns long when adult and about one red blood cell wide when transmitted by an insect vector
27
What stage do extraintesinal nematodes have?
an insect stage in which the larvae develops
28
Where do injected larvae go
to specific tissues such as skin, lungs, lymphatics | - here they mature to adults (forming skin nodules)
29
What happens once extraintestnal nematodes mature?
after a sexual stage they produce microfilariae
30
What do the microfilariae do?
migrate to particular tissues depending upon the species involved, giving rise to pathogenesis as they mature to microlarval stage?
31
Wucheria bancrofti?
microfilarial blockage of lymphatic ducts leading to elephantiases affects over 120 million people throughout the tropics and subtropics
32
Onchocerca volvulus?
larval migration to the eye causing river blindess 300 million at risk in sub saharan africa, parts of arabia and S america 27 million cases annually, 300,00 cases of permanent blindess
33
Treatment for onchocerca?
Ivermectin, but needs to be continued for 10-15 years as it only kills the larvae and not adult worms evidence that doxycycline can kill adult worms
34
What is elephentiasis?
legs swell to a huge extent because the fluid cannot return due to blocked ducts
35
Treatment for wucheria?
Diethylcarbamazine can kill all forms of the worms in around 2 weeks treatment more effective when used with ivermectin
36
Where do adult flukes mainly reside?
in blood (veins), gut or lungs
37
Life cycle of flukes?
complex, but essentially adult flukes produce eggs which become encysted when present in the liver or other tissues (bladder, lung, CNS)
38
What does reaction to presence of fluke eggs cause?
pathological changes in the infected tissue
39
What happens in schistosomiasis?
eggs are released via faeces or urine into water, where the parasite is taken up by snails, the snail then releases a form of larva (cercaria) which can penetrate skin and infect persons coming into contact with water
40
Schistostoma mansoni?
FLUKE encysted eggs present in the liver can cause fatal cirrhosis
41
Fasciola hepatica?
sheep liver fluke - can also infect humans
42
Where is schistosomiasis most common?
transmitted by water most prevalent in agriculture and fishing communities fro affected areas
43
What can infestation with schistosomiasis cause?
a variety of complications, mainly gut and urinogenital - but also include seizures, anaemia and renal failure praziquantel is the preferred treatment
44
What can flukes penetrate?
the colon wall and make their way via the hepatic portal vein to the liver
45
what does infestation with fasciola cause?
jaundice amongst a variety of complications causes cirrhosis and liver damage = jaundice
46
Tapeworms?
cestodes flat segmented worms containing both male and female organs
47
Taenia solium?
pork tapeworm pigs become infected by swallowing eggs present in the human faeces
48
What happens when humans ingest the uncooked pork?
the ingested eggs release larvae in the duodenum the larvae are carried in the blood to muscle, CNS and the eye where get encysted and cause pain and neurological problems such as epilepsy
49
Where is taenia a problem?
Mexico, latin america and other countries in the southern hemisphere with uncooked meat
50
Epinococcus granulosus?
adult worms are found in the guts of dogs they produce eggs (excreted in faeces) which can remain viable for up to a year
51
Where can epinococcus eggs be found?
in dog fur, on dog leads and on the tongues of infected dogs
52
What happens when epinococcus eggs are ingested?
they release larvae when in the gut and larval cysts can then be found in the liver and other tissues of humans and sheep
53
Cysts of epinococcus?
can be quite large (litres of fluid) and contain many immature larvae, causing major problems when they burst
54
How big are cestodes?
a few millimetres to 25 metres
55
What can the larval form of cestodes penetrate?
the gut wall and migrate to any internal tissues typicall they affect the lungs and liver but can also affect the CNS
56
What can infected meat contain?
hundreds of larval cysts (taenia solium) which can infect consumers when eaten the mouth of taenia solium hook into the gut wall so as to anchor the tapeworm

Management of Infection (36 decks)

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