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Amy Somerville > INF2 - E. INTESTINAL WORM INFECTIONS-COVERED > Flashcards

INF2 - E. INTESTINAL WORM INFECTIONS-COVERED Flashcards

1
Q

what are the types of roundworms (nematodes)

A

pin/thread - enterobius vermicularis
whips - trichuris trichiura
giant - ascaris lumbricoides

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2
Q

what are the examples of tapeworms (cestodes)

A
  • taenia sodium
  • taenia saginata
  • echinococcus granulosus
  • echinococcus multilocularis
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3
Q

taxonomy

A

species
genus
family
order
class
phylum
kingdom
domain

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4
Q

facts about roundworms

A
  • rounded
  • complete alimentary canal (mouth to anus)
  • no suckers to attach (small mouth to eat)
  • sexually differentiated
  • females larger, lay eggs
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5
Q

facts about flatworms

A
  • flattened dorsoventrally, segmented
  • alimentary canal absent or rudimentary (basic) - no digestive tract, absorb nutrients through cells into long, thin, flat body
  • suckers present (so doesn’t pass when goes to toilet)
  • hermaphrodites (no males and females, reproduce asexually)
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6
Q

what are the 2 main phylums

A

Nematoda and Platyhelminthes

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7
Q

what are the 2 classes of Platyhelminthes

A

trematoda and Cestoda

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8
Q

what are the genus of Nematoda

A
  • Trichuris spp
  • Ascaris spp
  • Necator spp
  • Ancylostoma spp
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9
Q

what are the genus of trematoda

A
  • schistosoma spp
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10
Q

what are the genus of Cestoda

A
  • taenia spp
  • echinococcus spp
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11
Q

Enterobius vermicularis (most common worm infection in UK)

A
  • pinworm/threadworm
  • infection = enterobiasis
  • adult worms reside in cecum
  • very common in children under 10
  • humans are only hosts
  • no multiplication inside body: females migrate out at night and lay eggs on skin around anus. Eggs hatch into larvae and worms and passed to someone else or crawl back up and reinfect
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12
Q

prophylaxis of enterobiasis

A
  • trim fingernails
  • cotton clothes and gloves during sleep
  • don’t scratch
  • frequent washing of sheets and hands to remove eggs
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13
Q

how is enterobius vermicularis transmitted

A

faecal-oral route
1. direct: anal region to mouth by hand and fingernail contamination or self-inoculation and others

  1. indirect: exposure to viable eggs on surfaces, bed linen, clothes (fomites)
  2. airborne eggs entering nose/mouth from contaminated dust
  3. larvae hatch from eggs on anal mucosa and larvae migrate up bowel (retroinfection)
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14
Q

diagnosis of Enterobius vermicularis

A
  • microscopy
  • perianal scrapings/swabs from under nails
  • frequently tape used in perianal region to get eggs to stick
  • investigate in morning and next day as females lay eggs at night on perianal skin
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15
Q

symptoms of Enterobiasis

A
  • pruritus ani (perianal itching): mainly at night. Can lead to secondary infections
  • vulvitis: worms enter vulva
  • insomnia, restlessness, loss of appetite
  • no blood feeding so no anaemia or eosinophilia
  • ulcerations at sites of attachment: secondary infections?
  • non-specific colitis in children
  • ectopic infections can cause problems: vuvlva
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16
Q

Trichuris trichuria

A
  • whipworm
  • infection: trichuriasis
  • most prevalent in tropical/humid climates/areas with poor sanitation
  • adult worms reside in cecum, remain attached to epithelium by burrowing in epithelial folds/tunnels so not passed in faeces
  • don’t migrate at night
17
Q

Ascaris lumbricoides

A
  • giant roundworm
  • infection: ascariasis
  • largest nematode (females larger)
  • most common woman infection globally
  • most prevalent in tropical areas (South America, South Asia, Australia) with poor sanitation
  • eggs have long developmental phase: 20 days outside host at 25 degrees Celsius to be mature be infective
  • adult worms reside in lumen of small intestine
  • larvae migrate to lungs via circulation
  • female have high fertility (200,000 eggs per day)
18
Q

what type of helminths are A. lumbricoides and T. trichiura

A
  • Geohelmithes/ soil-transmitted helminths (transmitted through soil)
  • most common chronic infections of humans
19
Q

how does infection of A. lumbricoides and T. trichiura occur

A
  • contact with parasite eggs or infective larvae in contaminated soil or food (raw veg)
20
Q

diagnosis of trichuriasis and ascariasis

A
  • copromicroscopy: stool examination to detect eggs
  • higher the egg count, more severe infection
  • T. trichiura eggs: barrel-shaped with 2 polar plugs
21
Q

symptoms of A. lumbricoides

A
  • often asymptomatic
  • lung migration: symptoms like pneumonia or asthma
    persistent cough, shortness of breath
    high infection - Loffler’s syndrome
  • abdominal pain, weight loss, fatigue
  • larvae can be in sputum
  • adult worms may be passed in stool, mouth or nose
  • intussusception: (intestine folds back on itself
    blood flow and intestine blocked
    ischemia then tissue necrosis then gut perforation and peritonitis
22
Q

symptoms of T. trichiura

A
  • often asymptomatic
    lots of worms burrowing and damaging lining of large tissue - blood loss
  • abdominal pain
  • stool containing mucus/bloody diarrhoea
  • rectal prolapse
  • chronic anaemia, growth retardation, impaired cognitive development
  • mucosal damage, secondary infections?
23
Q

treatment for nematodes

A
  • Ovex (mebendazole)
  • pregnant, young children - see GP
  • enterobiasis: single dose tablet, second dose after 2 weeks as it kills worms, not eggs
24
Q

Taenia spp.

A
  • taenia solium: pig tapeworm (infects pigs)
  • taenia saginata: beef tapeworm (infects cows)
  • segmented flatworms
  • humans are only definitive host
  • pigs/cows are intermediate hosts
  • infection through ingestion of cystercerci of raw/undercooked meat
  • adult worms attach to small intestine via their scolex
  • grow to 5-7m (maybe 25m)
25
Q

why are flatworms flat

A
  • hermaphrodites: thin and flat body as they don’t have a full alimentary canal so they absorb nutrients in through their cells
26
Q

morphology of taenia

A
  • T. solium has 4 large suckers and a rostellum - 2 rows of large and small hooks (help tapeworm attach to small intestine, not passed in faeces)
  • T. saginata has 4 large suckers

not important:
- single segments: proglottids
- proglottids behind the stolen are immature and become thicker as they mature (further from scolex)
- each. mature proglottid has female and male reproductive organs - hermaphrodites
- mature, gravid proglottids detach, passed in faeces

27
Q

how do we get taeniasis infection

A
  • eggs hatch out of proglottid segments
  • penetrate into intestinal wall and migrate to muscle in pig/cow
  • develop into cysticerci
  • we eat the infected meat which have cysticerci (immature, primitive larva)
  • if undercooked/raw we get taeniasis
28
Q

what is cysticercosis

A
  • humans ingest eggs or gravid proglottids of T. solium
  • occurs in pigs
  • can be fatal
  • we are intermediate hosts
  • ingestion of food contaminated with faeces
  • auto infection: ingest through own faecal contamination or proglottids carried to stomach by reverse peristalsis
  • oncosphere hatch, invade intestinal wall and migrate to striated muscles
  • and to brain, liver, other tissues
  • develop into cysticerci
29
Q

symptoms of taeniasis

A

few symptoms/none associated with adult worms in intestine
- intestinal discomfort
- diarrhoea
- more hungry
- obstruction
- weight loss
- embarrassment caused by proglottids crawling from anus

30
Q

symptoms of cysticercosis

A
  • maturation to cysticerci takes 1-2 months
  • found in SC tissue, muscle, CNS and eyes
  • SC cysts - no pathology
  • CNS or ocular cysts - seizures, intracranial hypertension, neurocysticercosis from cysts in brain
31
Q

Echinococcus spp.

A

4 species pathogenic for humans
- E. granulosus causes cystic enchinococcosis
- E. multicularis causes alveolar enchinococcosis
segmented body with scolex

  • dogs/canids eat infected organs ie- liver of infected sheep
  • tapeworm eggs the found in species from canids (why you need to worm pets etc)
  • human ingestion by faecal-oral route (eggs from pets fur, contaminated soil, veg)
  • zoonotic infection
32
Q

what is a zoonotic infection

A

when a pathogen usually found in animals occasionally infects humans

ie - ebola, rabies

33
Q

problems with zoonotic infections

A
  • animal reservoir: difficult to eradicate as can’t vaccinate in the wild
  • pathology more severe than human parasites as haven’t evolved to live with humans
  • transmitted by pets/livestock
34
Q

symptoms of enchinococcosis

A
  • cysts can grow to large size without causing symptoms
  • hard to detect, no egg detection in faeces
  • depends on size, quantity, location of cysts
  • weight loss
  • abdominal pain
  • general malaise
  • neurological symptoms, liver failure? if SC won’t be a problem
  • cysts are soft, can rupture during surgery and release parasite toxins: allergic reactions, death by anaphylaxis
35
Q

diagnoses of enchinococcosis

A
  • ultrasound, CT, MRI
  • serological tests: detect antibodies but may be from different worm parasites
    THESE TESTS CAN’T DIAGNOSE A PRIMARY INFECTION
36
Q

treatment for cestodes

A
  • taeniasis and cystericercosis: praziquantel
  • enchinococcosis: albedazole or mebendazole or praziquantel
    combo of surgery and drug treatment often required to remove cysts from organs

Amy Somerville (70 decks)

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