Nematodes

Question 1

List the nematodes:

Answer 1

• Trichuris trichiura (whipworm)
• Ascaris lumbricoides
• Toxocara canis/cati
• Enterobius vermicularis (pinworm)
• Strongyloides sterocoralis (threadworm)
• Ancylostoma duodenale / Necator americanus (hookworm)
• Ancylostoma braziliense
• Trichinella spiralis

Yikes.

Question 2

Life cycle of Trichuris trichiura? (whipworm)

Answer 2

Adult worms attach to human cecum - lay 1000-7000 eggs/day
Pass in feces and embryonate (become infective) in 3-6 weeks
Eaten; larvae hatch in intestine, penetrate villi; develop into adults in 1-3 months

Question 3

Pathogenesis of Trichuris trichiura?

Answer 3

Asymptomatic if less than 100

Colon damage, abdominal pain, vomiting, diarrhea, BLOOD in stool, prolapsed rectum

NO eosinophilia

Question 4

Diagnosis / Treatment of Trichuris trichiura?

Answer 4

Demonstrate barrel-shaped egg in feces

Mebendazole/albendazole

Question 5

Life cycle of Ascaris lumbricoides?

Answer 5

Largest nematode - up to 1 foot long

• Live in small intestine
• Eggs in stool / ingested by humans
• Hatch in duodenum –> mucosa, lymph –> portal circulation (LIVER) –> heart –> lungs (molt)

Migrate to bronchioles, trachea, glottis, esophagus, small intestines (adults)

Why the hell did he write so much.

Question 6

Pathogenesis of Ascaris lumbricoides?

Answer 6

Heavy infection: larvae migrate to lungs –> hemorrhage –> pneumonia

• Malnutrition from feeding on contents on intestines
• Bolus = intestinal blockage
• Can go to gall bladder, liver, appendix

Question 7

Diagnosis / Treatment of Ascaris lumbricoides?

Answer 7

Egg in stool / larvae in sputum

Mebendazole / albendazole

Question 8

Life cycle of Toxocara canis/cati?

Answer 8

Most puppies/kittens infected (like, nearly 100%)

Larvae activated in pregnancy and passes from mom to puppy/kitty - Humans ingest eggs

Question 9

Pathogenesis of Toxocara canis/cati?

Answer 9

Human infection is visceral larval migrans (VLM)

Random migration
HIGH eosinophilia; lesions in liver
Ocular larval migrans (OLM); trapped in eye tissue

Can be major tissue damage and immune response

Question 10

Diagnosis / Treatment of Toxocara canis/cati?

Answer 10

ELISA for antigen

Self-limiting, but thiabendazole used sometimes

Question 11

Life cycle of Enterobius vermicularis? (pinworm)

Answer 11

Humans only host

Live and mate in cecum; female migrate to anus; perianal region to lay eggs

Question 12

Pathogenesis of Enterobius vermicularis?

Answer 12

Intense anal itch –> scratch –> reinfection hand to mouth with eggs

Clothing and bedding can also hold eggs

Question 13

Symptomes of Enterobius vermicularis?

Answer 13

Self-limiting

Lack of sleep, poor appetite, nervousness, irritability in children

Adults: “pinworm neurosis” (from associated stigma)

Question 14

Diagnosis / Treatment of Enterobius vermicularis?

Answer 14

Scotch tape test –> visualize eggs

Pyrantel pamoate OR mebendazole

Question 15

Life cycle of Strongyloides sterocoralis?

Answer 15

In small intestine, lay eggs; hatch into rhabditiform larvae

• Direct: Develop to free-living filarifrom larva in soil
• Indirect: Free-living male/female worms
• Autoinfection: Filariform larvae in gut and invade mucosa

Filariform penetrate unbroken skin –> blood/heart –> lungs –> trachea –> small intestine

Question 16

Pathogenesis of Strongyloides sterocoralis?

Answer 16

Mild: Abdominal discomfort, nausea, vomiting, diarrhea

Heavy: Chronic dysentery, bronchitis, damage to intestinal mucosa (can lead to bacterial invasion and enteritis)

Question 17

Diagnosis / Treatment of Strongyloides sterocoralis?

Answer 17

Larvae/eggs in feces

Invermectin (hyperinfection), thiabendazole

Question 18

Life cycle of Ancylostoma duodenale / Necator americanus? (hookworm)

Answer 18

Suck blood from mucosa of small intestine (2-5 years)

Eggs in feces –> rhabditifrom larvae –> filarifrom larvae –> penetrate skin (like foot) –> blood to heart –> lungs/coughed up and swallowed –> intestines

Question 19

Pathogenesis of Ancylostoma duodenale / Necator americanus?

Answer 19

3 stages:

• Cutaneous: papule at site of penetration
• Pulmonary: larvae migrate through lungs (can cause bronchitis)
• Intestinal: suck blood

Anemia, weakness, vomiting, nausea, diarrhea

In infants: retardation

Question 20

Diagnosis / Treatment of Ancylostoma duodenale / Necator americanus?

Answer 20

Demonstrate hookworm in stool (blood in stool)

Mebendazole / albendazole; iron/vitamins

Question 21

What is Ancyclostoma braziliense?

Answer 21

Hookworm of dogs/cats (accidental in humans)

• Cutaneous larvae (creeping eruptions)
• Subcutaneous areas (migrate an inch a day)

Question 22

Diagnosis / Treatment of Ancyclostoma braziliense?

Answer 22

Appearance of lesion on hands, feet, buttocks

Albendazole or Ivermectin

Question 23

Life cycle of Trichinella spiralis?

Answer 23

Eating larvae in cysts in poorly-cooked pork
Mate in small intestine
Female invade mucosa/lymph nodes
Larvae in bloodstream
Encyst in muscle –> degeneration and calcifying cysts

Question 24

Pathogenesis of Trichinella spiralis?

Answer 24

Abdominal pain, diarrhea, nausea, vomiting

Migration of larvae causes localized edema (face), fever, eosinophilia, inflammation of heart

Intense muscular pain

Question 25

Diagnosis / Treatment of Trichinella spiralis?

Answer 25

Demonstrate larvae in muscle

Mebendazole / albendazole; pain relievers