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MD3002 > Helminths and protozoal infections > Flashcards

Helminths and protozoal infections Flashcards

1
Q

what sp of protozoa infect the small intestine

A
  • Giardia lamblia

* Cryptosporidium parvum

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2
Q

what sp of protozoa infect the large intestine

A

Entamoeba histolytica

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3
Q

what is giardiasis

A

a cause of travellers’ diarrhoea

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4
Q

how is G. lamblia spread

A

drinking water and person to person

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5
Q

describe the life cycle of G.lamblia

A
  • Trophozoite
  • Flagellated and bi-nucleated
  • Lives in upper part of small intestine
  • Adheres to brush border of epithelial cells
  • Cyst
  • Formed when trophozoiteforms resistant wall
  • Passes out in stools
  • Can survive for several weeks
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6
Q

describe the pathogenesis of G. lamblia

A
  • Present in the duodenum and upper ileum
  • Attaches to the mucosa via ventral sucker
  • Does not penetrate the surface
  • Causes damage to the mucosa and villous atrophy
  • Leads to malabsorption of food, esp. fats and fat soluble vitamins
  • May swim up the bile duct to gall bladder
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7
Q

what are the stigmata of G. lamblia

A
  • Mild infections are asymptomatic
  • Diarrhoea is usually self-limiting (7-10 days)
  • Chronic diarrhoea presents in immunocompromised patients
  • Stools are characteristically loose, foul-smelling and fatty
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8
Q

how is C. parvum spread

A

faecally contaminated water
animal reservoir
opportunistic (e.g. aids)

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9
Q

describe the life cycle of C. parvum

A
  • Asexual ; sexual development within host
  • Ingestion of resistant oocysts
  • Release of infective sporoziotesin small intestine
  • Invasion of intestinal epithelium
  • Division to form merozoiteswhich re-infect cells
  • After sexual phase, oocytesreleased
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10
Q

describe the pathogenesis of C. parvum

A
  • Enters cells of the microvillus border of small intestine
  • Remains within vacuole of epithelial cell
  • May multiply to give large numbers of progeny, especially in immunocompromised hosts
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11
Q

what are the stigmata of C. parvum infection

A
  • Moderate to severe profuse diarrhoea
  • Up to 25 litres of watery faeces / day
  • Usually self limiting disease
  • In HIV positive individuals with CD4+T-cell counts of
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12
Q

describe the features of E. histolytica

A 
common in tropics and sub tropics 
via contaminated food or water or anal sex
reproduce in the small intestine 
damage epithelia and red blood cells 
later on live in the large intestine 
cause colitis
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13
Q

describe the pathogenesis of E.histolytica

A
  • Adheres to epithelium and acute inflammatory cells
  • Resists host humoral and cell mediated immune defence mechanisms
  • Produces hydrolytic enzymes, proteinases, collagenase, elastase
  • Produces protein that lyses neutrophils, the contents of which are toxic to the host
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14
Q

what are the stigmata of E.histolytica infection

A
  • Small localised superficial ulcers leading to mild diarrhoea
  • Entire colonic mucosa may become deeply ulcerated leading to severe amoebic dysentery
  • Complications include intestinal perforation
  • Trophozoites may spread to the liver, and other organs
  • Rarely, abscesses spread to overlying skin
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15
Q

what are the features of bacillary dysentery

A
  • Many PMN in stool
  • Eosinophilsabsent
  • Many bacilli in stool
  • Blood/mucus present in stool
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16
Q

what are the features of amoebic dysentery

A
  • Few PMN in stool
  • Eosinophils present
  • Few amoebae in stool
  • Blood/mucus present in stool
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17
Q

how is G. lamblia treated

A
  • Mepacrinehydrochloride
  • Metronidazole
  • Tinidazole
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18
Q

how is C. parvum treated

A
  • Nitazoxanide

* Spiramycin

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19
Q

how is E. histolytica treated

A
  • Spiramycin
  • Metronidazole

all treated with oral rehydration therapy

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20
Q

how can protozoal infections be treated

A
  • Improved hygiene and water supplies
  • Eating only freshly prepared food served hot
  • Avoiding salads and fruit which cannot be peeled
  • Avoiding tap water and ice cubes
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21
Q

what are nematodes

A

roundworms

bisexual and cylindrical

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22
Q

what are cestodes

A

tapeworms

elongated and flat, segmented, hermaphrodite

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23
Q

what are trematodes

A

Flukes
leaf shaped flat worms
mainly hermaphrodite
rare

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24
Q

how are nematodes transmitted

A

soil

either swallowing eggs or active skin penetration

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25
Q

what is S. stercoralis

A

pin worm

causes villous atrophy and loss of intestinal elasticity

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26
Q

what are the stigmata of pinworm

A
  • Dysentery (persistent in immunocompromisedhosts)
  • Dehydration
  • Malabsorptionsyndrome
  • Anal pruritis
  • Association with appendicitis
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27
Q

how is whip worm transmitted

A

eggs on vegetables

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28
Q

what is A. lumbricoides

A

giant roundworm

29
Q

what are the stigmata of giant roundworm

A

digestive upsets
malnutrition
intestinal blockages
may be allergic reaction

30
Q

what is E. vermincularis

A
  • Threadworm

* Small cylindrical nematodes

31
Q

what is A. duodenale

A

hookworm
•Often picked up walking barefoot in infected areas
•Attaches to small intestine, suck blood and protein, often present in huge numbers
•Cause hypochromic anaemia
•Blood loss 0.03ml/day/worm (often 500-1000 worms)

32
Q

what is T. solium

A 
tapeworm 
•Acquired from ingesting worms or eggs in undercooked pork
•Reside in large intestine
•Can grow up to 7m long!
•Scolex–for attachment
33
Q

why are helminths and protozoa difficult to treat

A
  • Large variety of species
  • Complexities of their life cycles
  • Differences in their metabolic pathways
  • Drugs active against protozoa are inactive against helminths
34
Q

what are the 3 types of Helminth

A

Nematodes, cestodes and trematodes

35
Q

what are the two types of nematodes

A

blood and tissue

intestinal

36
Q

what are the two types of cestode

A

taenia

echinococcus

37
Q

what are the 3 types of trematode

A

lung, liver, blood

38
Q

what is Onchocerciasis

A

a disease caused by infection with the parasitic worm Onchocerca volvulus.[1] Symptoms include severe itching, bumps under the skin, and blindness. it is spread by Simulium flies.

39
Q

what is schistomaiasis

A

a disease caused by parasitic flatworms of the Schistosoma type. The urinary tract or the intestines may be infected.

40
Q

what a the pathological mechanisms of helminth infections

A
  • Inflammation
  • Competition for nutrients
  • Space occupying lesions
  • Stimulation of fibrosis
41
Q

what is Filariasis

A

an infection with roundworms of the Filarioidea type.[1] These are spread by blood-feeding black flies and mosquitoes.
can lead to elephantiasis

42
Q

what worms compete for nutrition

A
  • Hookworms
  • Ascaris
  • Tapeworms
  • Trichiuris trichiura
  • Major threat to health
  • More severe with poor nutrition
  • Intellectual development may be slowed
43
Q

what is dysentery

A

inflammation of the intestine causing diarrhoea with blood and/ or mucus

44
Q

what is trichiuris

A

aka whipworm infection
can cause dysentery, abdominal symptoms
growth and mental retardation

45
Q

what does hookworm cause

A

anaemia due to worm consuming blood

abdo pain

46
Q

what is ascariasis

A

caused by the parasitic roundworm Ascaris lumbricoides.
symptoms include SOB, fever, abdo symptoms, malnutrition, learning difficulties
hepatobiliary obstruction and jaundice, intestinal obstruction

47
Q

what helminths can cause space occupying lesions

A
  • Eggs in the wrong place
  • Cysticercosis causing CSF obstruction
  • Ascaris causing intestinal obstruction
48
Q

what is cysticercosis

A

caused by pork tapeworm

may cause neuro problems and siezures

49
Q

what types of fibrosis might occur from schistosomes

A

lung fibrosis leading to rt heart failure
liver fibrosis leading to portal hypertension
bladder fibrosis leading to bladder cancer

50
Q

how are cestodes (tapeworms) treated

A

praziquantel
in cysticercosis anti epileptic drugs are given to treat the seizures
steroids to reduce inflammation

51
Q

how are nematodes treated

A

albendazole is most effective

sometimes levamisole and piperazin

52
Q

how does praziquantel work

A

Not fully known: probably increases calcium permeability of membranes depolarisingthem
•May interfere with purine synthesis

53
Q

what is Hydatid disease

A

a cyst containing a tapeworm larva

54
Q

what is praziquantel used to treat

A
  • Hydatid disease
  • Cysticercosis
  • Schistosomiasis
  • Clonorchis, Fascioliasis and Paragnomiasis
55
Q

what are the pharmacological features of praziquantel

A
  • Well absorbed orally
  • 20 mg/kg
  • On WHO essential medicine list
  • Significant first pass effect
  • Low systemic concentrations
  • Excreted in the kidneys
  • Short half life
56
Q

what are the side effects of praziquantel

A
  • Dizziness, headache, drowsiness and somnolescence, rarely seizures
  • Abdominal cramps and nausea. Diarrhoea
  • Transient asymptomatic rise in transaminases
  • Urticaria, rash and pruritis
  • Interacts with rifampicin (decreased concentrations), carbamazine, phenytoin (reducing praziquantelbioavailability)
57
Q

what is albendazole used to treat

A

Treatment of nematode infections: trichiuriasis, filariasis, Enterobiusinfection, ascariasis, hookworm, toxocariasis, strongyloidiasis and some protozoa, some cestodes, mebendazol and thiabendazole

58
Q

what is albendazole MOA

A

Binds to colchicine sensitive receptor or tubulin
•This prevents polymerisationinto microtubules
•Impaired glucose uptake and depleted glycogen stores
•Degenerative changes appear in the worm

59
Q

what are the side effects of albendazole

A
  • Concentrated in semen and may be teratogenic
  • Persistent sore throat
  • Headaches dizziness and seizures
  • Acute liver failure
  • Aplastic anaemiaand marrow supression
60
Q

how does piperazine work

A
  • Agonist activity against the gamma butyric acid receptor paralysingmuscular activity
  • Orally active
  • Metabolism in liver
  • Variable half life
  • Used to treat ascariasis and enterobiusinfection
  • SE include GI tract upset and rarely hypersensitivity, dizziness
61
Q

how does pyrantel work

A
  • Treatment of hookworms and roundworms
  • Causes depolarisingneuromuscular blockade
  • Poorly absorbed providing selective toxicity
  • Excreted unchanged in the faeces
  • Antagonistic with piperazine
  • Avoid in pregnancy
  • Can cause intestinal obstruction if there is a heavy worm load
62
Q

what is levamisole

A
  • WHO List of essential medicine
  • Nicotinic acetylcholine receptor antagonist
  • Ascariasis and mixed ascarishookworm infection
  • Rapidly absorbed
  • Caution in pregnancy
  • Abdominal pain, nausea and vomiting are reported
63
Q

what is diethyl carbamazine

A
  • A piperazinederivative
  • WHO essential medicine list
  • Inhibits arachidonic acid making parasites more susceptible to immune attack
  • Filariainfection
  • Associated with increase in inflammation: caution Mazzottireaction, loss of site in onchocerciasis
64
Q

what is ivermectin used to treat

A

eradication of lymphatic filariasisand onchocerciasis

65
Q

how does invermectin work

A

Ivermectinbinds glutamate-gated chloride increase in the permeability of the cell membrane to chloride ions with hyperpolarization of the nerve or muscle cell resulting in paralsysisand death of the parasite either directly or by causing the worms to starve.

66
Q

what is niclosamide

A
  • Inhibits glucose uptake, oxidative phosphorylation and anaerobic metabolism
  • Used for the treatment of tape worm infections only
  • Causes dizziness, skin rashes, drowsiness and perianal itching
67
Q

how can helminth infections be prevented

A
  • Vector control for filariasis
  • Meat inspection for cysticercosis
  • Sanitation and hygiene for intestinal nematodes
68
Q

what does pruritus mean

A

itching

MD3002 (56 decks)

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