L37: Parasitic Roundworm Infections of the GI Tract

Question 1

3 types of helminths

Answer 1

1. Nematodes (roundworms) – non-segmented bodies, separate sexes, complete digestive system
2. Cestodes (tapeworms) – segmented bodies, hermaphroditic, absorb nutrients
3. Trematodes (flukes) – non-segmented/leaflike, hermaphroditic, primitive gut

Question 2

General facts about GI nematodes

Answer 2

Most common parasitic helminths in the US/world, not usually fatal, common in areas with poor sanitation (particularly developing tropics), caused by presence of adult forms in body – common in SE US

Question 3

Life cycle of nematodes

Answer 3

Egg –> multiple larval stages –> adult stages

• -Separate sexes, female is larger than male
• -Adult worms do not replicate in humans
• -Lead to eosinophilia

Question 4

Geohelminths

Answer 4

Nematode infection acquired through contact with infected soil due to larvae/eggs needing to develop in warm soil

Question 5

Enterobius vermicularis (pinworm)

Answer 5

Most common helminthic infection in US, flat-sided eggs, hang out in butt hole

Question 6

Transmission of pinworm

Answer 6

Fecal-oral due to ingestion of eggs which hatch and develop in the intestines – reinfection and transmission within families are both common – animal pinworms do not infect humans

Question 7

Symptomatic infection of pinworm

Answer 7

Perianal itching (can lead to secondary bacterial infection) and potential appendicitis – most infections are asymptomatic

Question 8

Diagnosis of pinworm

Answer 8

Identification of eggs in perianal region (flat-sided, use tape to see them)

Question 9

Control and prevention of pinworm

Answer 9

Anti-helminthic compounds such as mebendazole, pyrantel pamoate – single dose, repeated later – must treat ALL household members

Question 10

Trichuris trichiura (whipworm)

Answer 10

Named for shape of eggs (side kind of looks like a whip)

Question 11

Life cycle of Trichuris trichiura (whipworm)

Answer 11

Infected individual passes eggs in stool, mature in the soil/environment then consumed, hatch in intestines and develop in mucosa

Question 12

Epidemiology of Trichuris trichiura (whipworm)

Answer 12

1/4 of the world infected, mostly in tropical regions (SE US), 90% asymptomatic

Question 13

Transmission of Trichuris trichiura (whipworm)

Answer 13

Fecal-oral from contaminated soil

Question 14

Symptomatic infections of Trichuris trichiura (whipworm)

Answer 14

Often due to heavy worm burden (>200) and causes bloody, mucus-containing diarrhea, frequent stools, rectal prolapse, growth slowing, and anemia in kids

Question 15

Diagnosis of Trichuris trichiura (whipworm)

Answer 15

Identification of eggs in stool (look like handles of whips on the sides)

Question 16

Control and prevention of Trichuris trichiura (whipworm)

Answer 16

Proper sanitation and personal hygiene

Question 17

Ascaris lumbricoides

Answer 17

Cause ascariasis, largest of the intestinal nematodes and forms tangles of worms that can cause physical obstruction or blockage

Question 18

Life cycle of Ascaris lumbricoides

Answer 18

Infected individuals pass lumpy bumpy eggs that develop outside of human and get ingested – get into liver and lungs (eosinophil count in these locations is important) – takes over a month

Question 19

Transmission of Ascaris lumbricoides

Answer 19

Fecal-oral; soil contaminated with human feces – eggs must develop in soil first – HUMANS ARE ONLY RESERVOIR – most infections asymptomatic

Question 20

Symptoms of Ascaris lumbricoides

Answer 20

Range from abdominal discomfort to death – physical presence of adult worms in small intestine can lead to abdominal pain, indigestion, loss of appetite, vomiting, diarrhea – physical obstruction can occur

Question 21

Pulmonary disease of Ascaris lumbricoides

Answer 21

Combination of physical presence of larvae and immune response – mild cough, pneumonitis

Question 22

Diagnosis of Ascaris lumbricoides

Answer 22

Lumpy bumpy eggs in stool, larvae or eosinophils in sputum

Question 23

Control and prevention of Ascaris lumbricoides

Answer 23

Sanitation and hygiene

Question 24

What are the two types of hookworm?

Answer 24

Necator americanus and Anclylostoma duodenale

Question 25

Life cycle of hookworm/Necator americanus/Anclylostoma duodenale

Answer 25

Larvae form in the soil from eggs, takes a few weeks to mature but then alive in soil, can break through the skin and then get swallowed

Question 26

Epidemiology of hookworm/Necator americanus/Anclylostoma duodenale

Answer 26

Major cause of anemia (especially children and pregnant women), found in SE US

Question 27

Transmission of hookworm/Necator americanus/Anclylostoma duodenale

Answer 27

Larvae from fecal contaminated soil penetrate intact skin – no animal reservoir for human hookworms

Question 28

Disease of hookworm/Necator americanus/Anclylostoma duodenale

Answer 28

Cause iron-deficiency anemia due to blood loss from feeding; protein malnourishment; penetration of the skin can lead to moderate dermatitis; pneumonia and eosinophilia – Ancylostoma consumes more blood than Necator

Question 29

Diagnosis of hookworm/Necator americanus/Anclylostoma duodenale

Answer 29

Presence of eggs in stool (distinguishing between two species requires looking at adult worms/larvae)

Question 30

Prevention and control of hookworm/Necator americanus/Anclylostoma duodenale

Answer 30

Sanitation and wearing shoes

Question 31

Strongyloides stercoralis

Answer 31

Smallest intestinal nematode, found in SE US and Appalachia – first example of facultative parasite (can multiply and exist as free-living nematode in the soil)

Question 32

Life cycle of Strongyloides stercoralis

Answer 32

Infected individual is actually passing larvae through stool then develops into free-living adult in the soil and produces eggs there – mature larvae can also penetrate before they leave the intestines and cause a hyperinfection

Question 33

Transmission of Strongyloides stercoralis

Answer 33

Penetration of skin by infectious larvae

Question 34

Symptomology of Strongyloides stercoralis

Answer 34

Low worm burdens lead to little symptomology (epigastric pain and tenderness, bloating, heartburn) – pulmonary stage of infection can provoke pulmonary inflammation and eosinophilia

Question 35

Hyperinfection of Strongyloides stercoralis

Answer 35

• -Due to abrogation of immune defenses – increased numbers of filariform larvae leave the intestine –> worsening of diarrhea and pulmonary symptoms
• -Disseminated infections can also occur which causes migration of larvae all around body

Question 36

Diagnosis of Strongyloides stercoralis

Answer 36

Detection of LARVAE in stool

Question 37

Control and prevention of Strongyloides stercoralis

Answer 37

Sanitation and hygiene and wearing shoes

Question 38

Know your eggs!

Answer 38

Flat on one side = Enterobius vermicularis
Lemon/barrel (like a whip handle) = Trichuris trichiura
Lumpy bumpy = Ascaris lumbricoides
Boring/plain = hookworm
Larvae instead of eggs in stool = Strongyloides stercoralis