6/17- Helminths I: Intestinal Nematodes Flashcards Preview

Term 5: Infectious Disease > 6/17- Helminths I: Intestinal Nematodes > Flashcards

Flashcards in 6/17- Helminths I: Intestinal Nematodes Deck (53):

What are Neglected Tropical Diseases (NTDs)?

The most common afflictions of the "bottom billion"


What are the 3 most common afflictions of people living in poverty? Relative sizes?

(Intestinal Helminth Infections: soil-transmitted)

1. Ascariasis (2 in)

2. Trichuriasis (2 ft, largest)

3. Hookworm (cm, smallest)


What are the Millenium Development Goals?

6. Combat HIV/AIDS, malaria, and other diseases


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Prevalence of "worms" in Guatemalan kids? (chart)

Basically, all kids are infected; kids are disproportionately affected (adults have them too, but not as much)

- Peak just under 10 yo (practically 100%)

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What is this a symptom of? 

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Ascaris infection


Symptoms of hookworm and other soil-transmitted helminth infections?

- Hookworm leads to __% _____________

- Stunting

- Impaired memory

- Decreased school performance

- Debilitating and limit potential, but typically not fatal

Hookworm leads to 40% reduction in future wage earnings


What is this? Characterisics?

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Trichuris trichiura (Whipworm)

- Male on left

- Female on right

Thinner end is anterior (internal existence), while fatter back end is external in gut

- Causes inflammation


Structure of Tirchuris trichuria (whipworm) in environment?

Thinner end is anterior (internal existence), while fatter back end is external in gut

- Causes inflammation

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What is this? 

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T. trichiura egg


Life cycle of Tirchuriasis?

- Eggs ingested

- Larva hatch in small intestine

- Larvae migrate to colon

- Adults mature in colon

- Unembryonated eggs pass out in feces

- Eggs embryonate in soil

- Eggs ingested (May cause prolapsed rectum)

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What is this? 

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SEM of T. trichiura with its intracellular and extracellular existence


What are the clinical sequelae of Trichuriasis?

- Trichruis dysentery syndrome

- Trichuris colitis

- Rectal prolapse

(because feel like something is in rectum and straining hard)

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Life cycle of Ascaris lumbricoides?

- Eggs ingested

- Larvae hatch in small intestine, enter bloodstream, go to liver (then to IVC)

- Larvae migrate to the heart (right side)

- Larvae reach lung capillaries (via pulmonary a.)

- Larvae enter alveolar spaces; will have eosinophils and IgE in the lung (induces asthma)

- Larvae migrate up trachea and are swallowed

- Adults mature in small intestine

- Cause penetration and obstruction in the gut

- Eggs pass out in feces

- Eggs embryonate in soil 

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What is this? Characteristics? 

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- Eggs are very hardy

- Sticky: mucopolysaccharide


Disease syndromes of Ascariasis?

- Loeffler's syndrome (pneumonitis)

- Impaired nutrition

- Growth retardation

- Acute Intestinal Obstruction

- Biliary Tract Obstruction: pancreatitis, cholangitis, hepatitis


What is this? 

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Ascariasis obstruction of gut


Treatment for intestinal worms? Exception?

- Mebendazole

- Albendazole

Except Strongyloides


What is the life cycle of Toxocariasis?

Toxocara canis and Toxocara cati (Ascaris homolog found in cats and dogs):

- Animals eat embryonated eggs, acquires adults

- Eggs pass in feces and embryonate in soil

- Eggs are ingested by humans

- Larvae hatch in small intestine and penetrate wall

- Larvae migrate to all organs via bloodstream (don't become adult worms in intestine cause kinda in wrong host; migrate elsewhere)

- Causes pathology in eye, CNS, and liver (visceral larva migrans)

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What is this? 

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Eggs of Toxocara canis or T. cati


Clinical Syndromes of Toxocarisis? Ages affected?

Visceral Larva Migrans (1-3 yo)

- Pneumonitis (wheezing)

- Hepatitis

- Cerebritis

- Eosinophilia

- Hypergammaglobulinemia

Ocular Larva Migrans (>5 yo)

- Strabismus (exotropia)

Covert Toxocariasis

- Environmental cause of asthma- getting eosinophils, wheezing, maybe some cognitive deficits

- Rise of asthma in our inner cities?


Toxocariasis in the US

- Seroprevalence (by ethnicity)

- Highest in what region?

- Risk factors


- 21.2% in non-Hispanic blacks

- 12% in Whites

Highest in American South

Risk factors:

- Low household education

- Poverty

- Elevated lead levels

- Toxoplasmosis


What are these? What are included in this category? 

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- Necator americanus (85% of infxn)

- Ancylostoma duodenale

- Ancylostoma ceylanicum


Global distribution of human hookworm infection?

What is the prominent species?

Necator americanus

Wherever rural poverty and adequate climate overlap 

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Life cycle of Necator americanus?

- Larvae hatch and develop in soil

- Filariform larvae on blades of grass

- Larvae penetrate skin, enter bloodstream, and reach heart (not always through feet, may also spread over skin- cause dermatitis)

- Larvae enter lung capillaries and then alveolar spaces

- Larvae migrate up trachea, and are swallowed

- Adults mature in small intestine

- Eggs pass out in feces

- Larvae hatch and develop in soil 

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What is the underlying mechanism/cause of disease from hookworms? Result?

Intestinal blood loss (attach to small intestine)

- 25 worms = 1 mL blood loss = 0.55 mg Fe (a child's daily iron intake)

- Results in iron deficiency anemia and protein malnutrition


What is this? 

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Hookworm embedded in intestine


What is this? 

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Adult hookworms in situ (1 cm)


What can be done to detect hookworms?

Adult hookworm antigens- hemoglobinases

(Ac-MEP-1, hookworm metalloendopeptidase 1) 

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Symptoms of hookworm infections?

- Iron deficiency anemia and severe anemia

- Reduced growth, psychomotor development, physical fitness

- Developmental delays, lower IQ

- Reduced school performance and attendance

- Pallor and facial edema

- Anasarca

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At risk populations for hookworm disease? Symptoms?

Women and children: low iron stores


- Physical growth stunting

- Cognitive deficits and intellectual retardation

Women of child-bearing age:

- Puberty

- Menstruation

- Pregnancy (adverse fetal outcomes)


Comparison of typical age/intensity relationships of the three main infections?

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What can be used to treat these? (hookworms?)

- Benzimidazoles

- Mebendazole

- Albendazole Targeting the blood-feeding in the hookworm gut is in phase I trials in Brazil

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What drug fails to treat hookworm?



What is this?

Caused by?

Where is it found?

What at risk populations?

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Cutaneous Larva Migrans, "Creeping Eruption"

- Caused by A. braziliense

- Found in Caribbean, Florida, Gulf Coast

- Travelers from tropical resorts and Military person


Distribution of Strongyloidiasis?

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How to differentiate hookworm larvae with Strongyloides larva?

Strongyloides have notched tail??? 

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Life cycle of Strongyloides stercoralis?

- Reservoir hosts in dogs and monkeys

- Free living soil cycle

- Larvae penetrate unbroken skin

- Larvae enter bloodstream and reach lung capillaries

- Larvae enter alveolar spaces

- Larvae are swallowed

- Adult worms live in small intestine

- Larvae develop to L3 in colon and enter bloodstream

- Larvae pass out in feces

- Free-llving soil cycle

There is a potential for auto-infection from gut into lungs 

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What is this?

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Adult S. stercoralis in crypts of small intestine


Clinical features of Strongyloidiasis? Caused by what?

Clinical features:

- Enteritis

- Diarrhea

- GI discomfort


- Larva currens (creeping infection)

- Eosinophilia present

Caused by Strongyloides stercoralis


What is this?

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Lava Currens from Strongyloides

- Larva currens = autoinfection with Strongyloides filariform larvae


Clinical features of hyperinfection with Strongyloides?

- Intestinal perforation

- Shock, sepsis, gram-negative meningitis

- Hemorrhagic pneumoina

- Eosinophilia often absent


Risk factors for Strongyloides hyperinfection?


- Immunosuppressive therapy

- Autoimmune disease, malignancy HTLV-1 infection (not HIV)

Malnutrition (especially children under 10 yo)


Diagnosis of Human Strongyloidiasis?

- Hunting in "black gold"- multiple fecal exams looking for larvae

- Blood agar plate looking for larval tracks

- Culture with charcoal to amplify through heterogonic life cycle

- Serologic tests ("not yet ready for prime-time")


What is this?

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First stage larvae of Strongyloides (NOT EGGS)


Treatment for Strongyloides?



What is this?

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Pinworm, or Enterobiasis

- Enterobius vermicularis


Life cycle for Enterobiasis (pinworm)?

Enterobius vermicularis

- Eggs ingested

- Larvae hatch in small intestine

- Larvae migrate to colon

- Adults mature in colon

- Gravid adults migrate out of anus

- Adults lay eggs on perianum

- Eggs embryonate on perianum

- Eggs contaminate fingers

- Eggs are ingested

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Epidemiology of Enterobius vermicularis?

- Geography

- Transmission


- Worldwide prevalence

- Tropical and temperate climates


- Re-infection

- Person-to-person

- Sexual

- Fomite


Adult habitat of Enterobius vermicularis?

Cecum and appendix

- Gravid female nocturnally deposits eggs onto perianal skin

- Eggs mature after 4-6 hrs of oxygen exposure


Clinical features of hookworm infection (Enterobius vermicularis)?

- Asymptomatic -> pruritus ani (itchy butthole)

- Appendiceal inflammation

- Female urogenital tract infection, granulomas

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Diagnosis of pinworm infection (Enterobius vermicularis)?

Unfrosted scotch tape over anus (early morning test) 

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Treatment of pinworm infection (Enterobius vermicularis)?

- Albendazole (1 dose)

- Repeat in 2-4 weeks

- Treat entire family


What is this? 

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Enterobius vermicularis egg (?)