Nematodes: Intestinal Nematodes

Question 1

Life cycle: direct
Route of infection: contaminated soil
Geography: worldwide
Specimen source: stool sample
Morphology: adults - 20-35 cm female, 15-31 cm male. eggs - fertilized, 45-75 mcm by 50 mcm, unfertilized, 85-95 mcm
Lab tests: formalin-ethyl acetate concentrate stool
Pathology: asymptomatic, pneumonitis - Loeffler’s syndrome, eosinophilia, malabsorption, bowel obstruction

Answer 1

Ascaris lumbricoides

Question 2

Life cycle: direct
Route of infection: ingestion of eggs; fingers, airborne eggs, fomites-soiled nightclothes, soiled bed linens
Geography: worldwide
Specimen source: stool sample
Morphology: eggs; 50-60 mcm flattened on one side. adults; females, 8-13 mm, males 2-5 mm
Lag tests: scotch tape/cellulose/cellophane method, when to take specimen - early morning/ just after waking up. can be infective to lab personnel
Pathology: pruritus, nervousness, may have eosinophilia

Answer 2

Enterobius vermicularis

Common name: pinworm

Question 3

Life cycle: direct
Route of infection: ingesting eggs
Geography: worldwide
Specimen sample: stool sample
Morphology: eggs; 50-54 mcm by 20 mcm - barrel shape. adults; females 35-50 mm, males 30-45 mm
Lab tests: formalin-ethyl acetate conc. stool
Pathology: asymptomatic, hypo chromic anemia - malnutrition and blood loss, dysentery

Answer 3

Trichuris trichiura

Common name: whipworm

Question 4

Life cycle: Eggs passed by birds or man enter the environment, become embryonate, and become infective. Eaten by fish, larvae develop in fish. Fish eaten by humans.
Route of infection: May be ingestion raw fish, raw shrimp, crabs and snails
Geography: Philippines, Taiwan Japan, Egypt, Iran
Specimen source: stool sample
Morphology: adults; 2.5-4.3 mm female, 2.3-3.2 mm male. eggs; like Trichuris - less prominent polar plugs, striated, 36-45 mcm
Pathology: large numbers - malabsorption, watery stools, pneumonia, heart failure

Answer 4

Capillaria philippinensis

Question 5

Life cycle: larvae- heart, lungs, intestine
Route of infection: skin penetration by filariform larvae
Geography: N. amercanus (NA) - new world - U.S., Malaysia, Africa. A. duodenale (AD)- old world - Europe, Asia
Specimen source: stool sample
Morphology: adults; 7-11 mm male, 10-13 mm female, 2 pair teeth (AD), 9-11 mm female (NA) cutting plates. eggs; 56-75 mcm by 36-40 mcm, thin shell. rhabditiform larvae; long buccal cavity, small genital primordium - only seen if old stool, >1-2 days unfixed.
Lab tests: formalin-ethyl acetat conc. stool
Pathology: pruritis, vesicles from erythematous papulae is called ground itch. Lg. # larvae - pneumonitis. adults, intestine - diarrhea, nausea, blood loss (stools- red to black). chronic infections - iron deficiency

Answer 5

Hookworms - Ancylostoma duodenal and Necator americanus

Question 6

Life cycle: larvae - intestine - adults
Route of infection: infected larvae contaminating plant material
Geography: worldwide
Specimen source: stool sample
Morphology: adults; like hookworm, except no distinct buccal capsule with special mouth parts. Rhabditiform larvae; long buccal cavity, small genital primoridum. eggs; like hookworm, 75-95 mcm, oval, pointed ends
Lab tests: formalin-ethyl acetate conc. stool
Pathology: asymptomatic, diarrhea, anorexia, nausea, headache, hemorrhage in intestinal tract

Answer 6

Trichostrongylus spp.

Question 7

Life cycle: larvae- vessels - lungs - intestine
Route of infection: skin penetration
Geography: worldwide
Specimen source: stool sample
Morphology: rhabditiform larvae - short and sexy. can develop in intestinal tract and be infective to lab personnel
Lab tests: formalin-ethyl acetate conc. stool. entero-test, baemann concentration technique, harada - mori filter paper (“Mini Barman”), agar plate culture, IgM, IgG antibody test, ELISA
Pathology: asymptomatic to cutaneous - pruritus, lung - pneumonia, intestinal infections, diarrhea; super infections - death. auto infection- filariform larvae

Answer 7

Strongyloides stercoralis