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Microbiology Part 2 > Lec43 Nematodes > Flashcards

Lec43 Nematodes Flashcards

1
Q

What do you generally use to treat nematodes [round worms]?

A
  • albendazole, mebendazole, pyrantel pamoate
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2
Q

What are the intestinal nematodes?

A
  • ascaris lumbricoides
  • hookworm [necatur americanus, ancylostoma duodenale]
  • strongyloides stercoralis
  • enterobius vermicularis [ping worm?]
  • trichuris trichiura
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3
Q

What are properties of ascaris lumbricoides

A
  • infects 1/4 of world population
  • most infections asymptomatic
  • clinical presentation in intestines related to obstruction
  • more significant disease in children
  • not attached to wall, constantly swimming against fecal stream
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4
Q

What is ascaris lumbricoides life cycle?

A
  • human host, no other reservoir
  • male and female worms live 1-2 yrs in lumen of duodenum and upper jejunum
  • females produce 2000 eggs daily
  • eggs laid in duodenum and evacuated in feces
  • develop to infective stage in soil in 3-4 wks
  • after ingestion –> larvae penetrate intestinal wall and enter circulation/lymph
  • migrate to liver –> right heart –> lungs
  • develop in pulmonary capillaries
  • mature larvae enter alveoli, coughed up and swallowed –> are now mature enough to resist gastric acidity and enter duodenum
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5
Q

How is ascaris lumbricoides transmitted?

A
  • ingestion of soil/food contaminated with eggs
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6
Q

What are clinical effects of ascaris lumbricoides?

A
  • intestinal obstruction
  • secrete digestive enzymes and use host-ingested proteins –> nutrient impairment causes reduced growth in children
  • ascaris pneumonitis [loeffler’s syndrome] –> productive cough/fever/dyspnea/wheezing
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7
Q

What is loeffler’s syndrome?

A
  • pneumonitis caused by ascaris
  • due to hypersentitivity rxn to migrating larvae in lung
  • present with productive cough, dyspnea, wheezing, fever, angioedema, urticaria, pulm infiltrates, eosinophilia
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8
Q

What is mech of action of benzimidazoles?

A
  • inhibit assembly of microtubules and inhibit uptake of glucose by helminths
  • get immobilization and death of helminths
  • also kills larva
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9
Q

What do you use to treat ascaris?

A

benzimidazoles [albendazole or mebendazole]

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10
Q

What are two types of benzimidazoles?

A
  • albendazole

- mebendazole

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11
Q

What can benzimidazoles treat?

A
  • ascaris lumbricoides
  • hookworm
  • strongyloides stercoralis
  • enterobius vermicularis
  • trichurius trichiura
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12
Q

Where are ascaris infections?

A

in impoverished areas world wide

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13
Q

How do you diagnose ascaris

A
  • find adult female

- look under microscope for eggs in stool

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14
Q

What are signs of hookworm

A
  • microcytic anemia [not as much pigment and small RBC] = chronic iron deficient anemia
  • eosinophilia
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15
Q

Where do you get hookworm infections?

A

in warm temperate climates

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16
Q

When you hear hookworm what should you think?

A
  • childhood anemia in developing country
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17
Q

How is hookworm transmitted? life cycle??

A
  • no reservoir hosts
  • penetrates skin and migrates through venous circulation, pulm arterial irculation, alveoli, bronchi, trachea, swallowed and go to small intestine
  • mature into adults in small intestine and mate
  • adult worms 9mm-13mm long have two pairs of cutting plates [NA] and teeth [AD]
  • live for 4-5 yrs
  • feed on host small bowel mucosa and suck blood directly from site where attached to wall
  • goes through free-living cycle, molts to become infective filariform larvae
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18
Q

What does ancyclostoma braziliense? pathogenesis?

A
  • dog hookworm
  • causes creeping eruption when enters human = wrong host –> cannot complete life cycle and get itchy tracks in skin
  • after wks - mos larva dies and
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19
Q

What do you use to treat ancylostoma braziliense/

A
  • single dose ivermectin or 2 days albendazole
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20
Q

Where is ancyclostoma braziliense common?

A
  • southeastern US and the tropics
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21
Q

How do you treat hook worm?

A

mebendazole or albendazole

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22
Q

What are the two hook worm species?

A
  • necatur americanus

- ancyclostoma duodenale

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23
Q

How do you diagnose hook worms?

A

eggs in stool

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24
Q

What are signs of strongyloides steroralis?

A
  • causes severe hyperinfection syndrome in immunocompromised [have lots of bacterial infections at same time]
  • can see worsening after you give steroids
  • intestinal obstruction
  • nutritional deficiencies
  • pulm infiltrates
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25
Q

What are active treatments against s. stercoralis?

A
  • ivermectin
  • albendazole
  • thiabendazole
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26
Q

Where is strongyloides stercoralis world wide?

A

worldwide, in SE US

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27
Q

Worsening symptom on steroids what should you think?

A

strongyloides

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28
Q

How is strongyloides transmitted?

A

penetration of intact skin by filariform larvae

29
Q

How is strongyloides diagnosed?

A
  • visualization of larvae in stool, sputum, biopsied tissue

- serologic evidence of past exposure

30
Q

what is pathogenesis of infection?

A
  • penetrates skin
  • through blood to lungs
  • coughed up and swallowed
  • thousands of eggs per day, hatch in intestinal lumen, shed in stool as larvae
  • free form life cycle
  • maintain auto-infection cycle sometimes for decades because larvae can reinfect via perianal skin when they are being excreted
31
Q

What are the intestinal worms with migratory phase in lungs?

A
  • ascaris lumbricoides
  • necator americanus [hookworm]
  • ancyclostoma duodenale [hookworm]
  • strongyloides stercorales
32
Q

What is pinworm?

A
  • enterobius vermicularis
33
Q

What is whipworm? sign?

A
  • trichurius trichuria

- causes rectal prolapse

34
Q

What is dog helminth? sign?

A
  • toxocara canis
  • causes visceral larva migrans and retinal larva migrans
  • reason for sandbox covers
35
Q

Where is enterobius vermicularis prevalent?

A
  • throughout world including US
36
Q

What are signs of pinworm?

A
  • many infections asymptomatic

- ma have: perianal itching, vaginitis from worms migrating ectopically

37
Q

What is the most common intestinal nematode infection in US?

A
  • enterobius vermicularis
38
Q

Is there a reservoir for enterobius vermicularis?

A

nope! only humans

39
Q

What are risk factors of pinworm spread?

A
  • moderate humidity
  • dense indoor crowding
  • high proportion of school-age children increases prevalence
40
Q

What is life cycle of pinworm?

A
  • at night gravid female migrates to perianal and perineal region to lay eggs
  • eggs mature in 6 hrs and transferred from perianal region to mouth = autoinnoculation [scratch butt then suck thumb]
41
Q

What are lateral alae?

A
  • on adult enterobius worm, allow it to move easily along GI tract mucosa
42
Q

How is enterobius transmitted?

A
  • ingestion of embryonated eggs from stool of infected individual
43
Q

What is diagnostic test for pinworm?

A
  • identify ova in perianal area using scotch tape test
44
Q

What is treatment for enterobius/

A
  • pyrantel pamoate or mebendazole or albendazole
45
Q

Who/where is trichuris trichiura infection usually found?

A
  • mostly children of low socioeconomic status
  • warm most climates –> SE Asia, sub saharan africa, caribbean islands
  • esp. found where human feces used as fertilizer
46
Q

What is polyparasitism?

A
  • having multiple parasites

- common with trichuris trichiura and ascaris/hookworm/malaria

47
Q

What are properties of trichuris trichiura?

A
  • adult worm 3-4.5 cm
  • anterior end threaded into epithelial tunnel
  • posterior end protrudes into small intestine
48
Q

What is associated wtih trichuris trichiura?

A

rectal prelapse

49
Q

How is trichuris transmitted?

A
  • ingestion of eggs from stool
50
Q

What are clinical signs of trichuri trichiura?

A
  • diarrhea
  • abdominal pain
  • rectal prolapse
51
Q

How is trichuris diagnosed?

A
  • identification in stoll of barrel shaped eggs with characteristic polar plugs
52
Q

How is trichuris treated?

A

mebendazole or albendazole

53
Q

What are diseases of tissue nematodes

A
  • lymphatic filiariasis

- river blindness [onchocerciasis]

54
Q

What are tissue nematodes?

A

diseases whos adult phase is outside of intestinal tract

55
Q

What is lymphatic filariasis?

A
  • infected mosquito introduces 3rd stage filarial larvae onto skin of human host
  • larvae penetrate bite wound and develop into adult
  • adult resides in lymphatic channels
  • adults produce microfilariae that migrate into blood channels moving actively through lymph and blood
56
Q

What are clinical manifestations of lymphatic filiarisis

A
  • disrupt normal lymphatic flow
  • chronic lymphedema –> elephantiasis
  • damage to lympathics stays after adult worms dead or treated
57
Q

How is lymphatic filiarasis transmitted?

A

mosquito bite, introduce mirofiliari

58
Q

What is geo distribution of parasites that cause lymphatic filiarasis?

A
  • wuchereria bancrofit in tropical areas
  • onchocerca volvulus in Africa, latin ameria, middle east
  • others endemic to asia or indonesia or south america etc
59
Q

When are highest times of microfilarisis?

A
  • at night –> adult worms release microfilariae at night at same time as mosquitos feed
60
Q

What is river blindness? Effects?

A
  • onchocerca volvulus adult worms live in subcutaneous tissue
  • microfilariae migrate in subcutaneous tissue causes pruritis and hypopigmnetations
  • migrate to eye and cause blindess
61
Q

What is life cycle of onchocerca vovlulus?

A
  • infected blackfly brings filarial larvae to skin
  • pentrates into bite wound
  • in subcutaneous tissue larvae develop into adult filariae
  • adult filariae reside in subcutaneous nodules
  • female worms in nodules live 9 yrs
62
Q

Where are onchocerca vovlulus found in body?

A
  • typically in skin and lymphatic connective tissue

- also in peripheral blood, urine, sputum

63
Q

What is geo distribution of onchocerca volvulus?

A
  • mainly africa, also latin america and middle east
64
Q

What are clinical manifestations of river blindness?

A
  • subcutaneous nodules

- dermatitis

65
Q

How is river blindness diagnosed?

A

skin snips

66
Q

How is river blindness treated?

A

ivermectin

67
Q

How is dracunculis medinsis transmitted?

A

by drinking water contaminated by larvae that infect copepods

68
Q

What is pathogenesis of dracunculiasis?

A
  • larvae penetrate host stomach and intestinal wall and enter ab cavity and retroperitoneal space
  • adult females migrate toward skin surface
  • 1 yr after infection female worm induces blister on skin
  • when lesion comes into contact with water, female worm emerges and releases larvae
69
Q

What is treatment for dracunculiasis?

A
  • local cleansing of lesion and local application of antibiotics
  • mechanical extraction of worm over period of days
  • no curative antihelmnithic treatment available
  • interupt transmission by filtering water through nylon cloth

Microbiology Part 2 (30 decks)

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