6/17- Helminths I: Intestinal Nematodes Flashcards
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?
- Combat HIV/AIDS, malaria, and other diseases
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%)
What is this a symptom of?
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?
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
What is this?
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)
What is this?
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)
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
What is this? Characteristics?
- 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?
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)
What is this?
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
Seroprevalence:
- 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?
Hookworms:
- 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
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
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?
Hookworm embedded in intestine
What is this?
Adult hookworms in situ (1 cm)
What can be done to detect hookworms?
Adult hookworm antigens- hemoglobinases
(Ac-MEP-1, hookworm metalloendopeptidase 1)
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
At risk populations for hookworm disease? Symptoms?
Women and children: low iron stores
Children:
- 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?
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
What drug fails to treat hookworm?
Mebendazole
What is this?
Caused by?
Where is it found?
What at risk populations?
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?
How to differentiate hookworm larvae with Strongyloides larva?
Strongyloides have notched tail???
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
What is this?
Adult S. stercoralis in crypts of small intestine
Clinical features of Strongyloidiasis? Caused by what?
Clinical features:
- Enteritis
- Diarrhea
- GI discomfort
Autoinfection:
- Larva currens (creeping infection)
- Eosinophilia present
Caused by Strongyloides stercoralis
What is this?
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?
Steroids
- 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?
First stage larvae of Strongyloides (NOT EGGS)
Treatment for Strongyloides?
Ivermectin
What is this?
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
Epidemiology of Enterobius vermicularis?
- Geography
- Transmission
Geography
- Worldwide prevalence
- Tropical and temperate climates
Transmission:
- 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
Diagnosis of pinworm infection (Enterobius vermicularis)?
Unfrosted scotch tape over anus (early morning test)
Treatment of pinworm infection (Enterobius vermicularis)?
- Albendazole (1 dose)
- Repeat in 2-4 weeks
- Treat entire family
What is this?
Enterobius vermicularis egg (?)
