Upgrade to remove ads
Only $2.99/month

Intestinal Nematodes

Terms in this set (37)

Enterobius vermicularis Transmission
Via direct oral ingestion of eggs, inhalation of airborne eggs in dust, and retro-infection through the anus
Enterobius vermicularis Clinical Manifestations
Asymptomatic
Symptomatic: Incubation, then perianal, perineal, and vaginal irritation and pruritis
Enterobius vermicularis Diagnosis
Visualizaiton of the worm itself via scotch tape test repeated on consecutive days
Enterobius vermicularis Treatment
Albendazole x 1, Mebendazole x 1
Treat all household members and repeat in 2 weeks
Trichuriasis Parasitology
Life history begins with the ingestion of T. trichiura eggs with food or water. The eggs hatch in the small intestine releasing larvae that enter the crypts of Lieberkuhn, develop for about a week and re-enter the intestinal lumen. They migrate to the caecum, attach to the surface of the mucosa by their anterior end and mature to adult males and females.
Trichuriasis Clinical Manifestations
Mild infection <100 worms: Asymptomatic
Major infection: Chronic diarrhea with mucous/blood, abdominal pain, tenesmus, rectal prolapse
Trichuriasis Treatment
Albendazole x 1, mebendazole x 3 days
Capillaria philippinensis Parasitology
Female worms in the intestine of humans produce both eggs and larvae. Some larvae develop into sexually mature, reproducing, adults (auto-infection).
Capillaria philippinensis Transmission
Eggs that reach water are ingested by small fresh water fish that hatch, and the larva develops into the infective stage in the fish intestines. Fish eaten raw by humans, larvae escape from the fish intestine and develop into adults in the host's intestines in 10-14 days. Fish can also be eaten by birds who then defecate the larva into ponds, re-introducting the life cycle.
Auto infection is an important part of the life cycle, perpetuating the infection and increasing the number of worms.
Capillaria philippinensis Treatment
Albendazole x 10 days, Mebendazole x 20 days
Trichostrongyliasis Parasitology
Primarily parasites of herbivores but occasionally infect humans. Eggs are passed in the feces which embryonate in the environment. Prevalent in the Middle East and Asia. The use of sheep or cow manure as fertilizer contributes to the spread of infection in farming communities.
Trichostrongyliasis Transmission
Ingestion of larvae through manure contaminated water or food
Invasion through skin is possible
Adults reside in duodenum or upper jejunum
Trichostrongyliasis Clinical Manifestations
Asymptomatic
Symptomatic: Mild, with epigastric pain, flatulence
Trichostrongyliasis Treatment
Albendazole x 1
Mebendazole x 3 days
Intestinal Worms Key Points
1. Usually no eosinophilia: No invasion into bloodstream
2. Diagnosis is usually via stool examination for eggs since they reside in the intestine (except for enterobius vermicularis which is via scotch tape test)
Anisikiasis Transmission
Via consumption of raw fish
Anisikiasis Clinical Manifestations
Gastric: Severe epigastric pain few hours after eating infected fish with N/V and gastric bleeding 12-24 hours after eating. Usually pseudoterranova species

Intestinal: Like acute appendicitis, regional enteritis, SBO, perforation a few days after eating
Anisikiasis Diagnosis
Endoscopy (gastric) or surgical resection (intestinal)
Anisikiasis Treatment
Worm removal
Ascaris lumbricoides Stages of Infection
Infected eggs are ingested
Migrating larvae go from the gut to the liver, to the lungs, and then back down to the gut.
Adults then reside in the intestine and produce 200k eggs/day
Ascaris lumbricoides Transmission
Infection occurs when the infective eggs are ingested with contaminated food and water. The eggs hatch into larvae in the jejunum a few hours after being swallowed.
Ascaris lumbricoides Life Cycle
1. Larvae penetrate intestinal mucosa
2. Migrate via portal vessels/lymphatic system into the liver
3. Carried through the heart into the lungs
4. Penetrate capillary walls and enter lung alveoli
5. Move up bronchi and trachea to pharynx and swallowed
6. Migrate down esophagus
7. In small intestine, larvae form immature adult worms
8. Worms mature and copulation takes place
Ascaris lumbricoides Clinical Manifestations
MIGRATION
1. Loffler's syndrome: dry cough, fevers, bronchial asthma
2. Eosinophilia

ADULTS IN INTESTINE
1. Usually asymptomatic
2. Sometimes SBO, nutritional deficiencies
3. Eosinophilia resolves
Ascaris lumbricoides Diagnosis
Stool examination for eggs
Larvae in sputum
Adults in stool or vomit
Ascaris lumbricoides Treatment
Albendazole x 1
Mebendazole x 3 days
Two major types of hookworms
Ancylostoma duodenale
Necator americanus
Necator americanus Life Cycle
1. Larvae infect humans only through skin by secrete enzymes that degrade host connective tissue components.
2. Larvae penetrate into host venules and lymphatics
3. Larvae swept into lungs where rupture the capillary vessels to enter the alveolar spaces.
4. Migrate to upper respiratory tract to gastrointestinal tract.
5. Entry into small intestine stimulates molting of larvae to the adult stage.
Necator americanus Transmission
Via skin from feet and get into vasculature
Difference between necator americanus and Ancylostoma duodenale
Ancylostoma can skip the pulmonary vasculature part and can enter via fecal-oral ingestion and become adult worms via intestine only
Clinical Features of Hookworm Infection
ASYMPTOMATIC

DERMATOLOGIC
Ground Itch: Burning/stinging/itching with papulomacular rash at site of entry of larvae

GASTROINTESTINAL
Colicky abdominal pain with eosinophilia

PULMONARY
Pneumonitis with slight cough with light infection, infiltrates with heavy infection.

HEMATOLOGIC
Hypochromic microcytic anemia, hypoalbuminemia
Diagnosis of Hookworm Infection
Stool O+P for eggs
Treatment of Hookworm Infection
Albendazole x 1
Mebendazole x 3 days
Strongyloides stercoralis Stages of Infection
Infective: Filariform larvae
Migrating Larvae: Move from skin/gut to lungs to GI
Adults: Burrow between enterocytes in lower duodenum
Eggs: Hatch in intestines
Strongyloides stercoralis Transmission:
Direct penetration of skin from ground via feet
Autoinfection via movement of worms out of intestine into bloodstream again into lungs
Strongyloides stercoralis Clinical Manifestations
ACUTE:
Cutaneous: Linear urticaria, pruritis
Pulmonary: Loffler's syndrome
Intestinal: Epigastric pain, vomiting, loose stools
Hematologic: Eosinophilia

CHRONIC
Usually asymptomatic, sometimes get pruritis, larva currens, loose stools/epigastric discomfort/nausea

HYPERINFECTION
Severe infections can occur which lead to colitis, SBO, and result in GNR bacteremia/pneumonia/meningitis; these pts often have no eosinophilia
Strongyloides stercoralis Diagnosis
1. Stool examination relatively useless due to few numbers of eggs in stool unless large volume and multiple samples
2. Serologies sometimes useful
3. Plating onto agar to visualize the movement of worms
Strongyloides stercoralis Treatment
Ivermectin x 1-2 days
Albendazole x 3 days
Thiabendazole x 3 days
THIS SET IS OFTEN IN FOLDERS WITH...