Lesson 2 - Nematodes Flashcards
Nematodes
Common name: Giant Roundworm/Ascariasis
Ascaris lumbricoides
Most common and largest nematode. Soil-transmitted helminth (STH)
Ascaris lumbricoides
Habitat: small inestine
Ascaris lumbricoides / Necator americanus, Ancylostoma duodenale / Strongyloides stercoralis / Capillaria philippinensis
Transmitted by embryonated eggs (embryonated eggs are infective stage)
Ascaris lumbricoides
Diagnostic test for Ascaris lumbricoides
- Direct fecal smear
- Kato-katz technique
Pathogenesis:
- Major damage occurs during larval migration
- Principal site of tissue reaction is the lungs, where inflammation with an eosinophilic exudate occurs
- Heavy worm burden > malnutrition
Ascaris lumbricoides
Lung Phase (L3 > L5):
- Hypersensitivity pneumonutus (Loefeller’s Syndrome)
Intestinal phase (L5 > Adult Worm):
- acute intestinal obstruction
- malabsorption syndrome
- nutrient deficiencies
Wandering Worms:
- Due to erratic behavior of adult worms
- Hepatobiliary ascariasis
- Pancreatitis, appendicitis
Ascaris lumbricoides
Treatment of choice for Ascaris lumbricoides
Albendazole (has greater larvicidal activity than mebendazole)
Hookworm (Miner’s Anemia, “tunnel disease”, Wakana disease, “brickmaker’s anemia”, “Egyptian chlorosis”
Necator americanus / Ancylostoma duodenale
Soil-transmitted helminth (STH)
Blood-sucking nematodes
Differentiated based on character of buccal spsears of filariform larvae
Necator americanus / Ancylostoma duodenale
Transmission is by skin penetration by filariform larva (L3)
Necator americanus / Ancylostoma duodenale
Diagnostic Stage: Eggs in feces.
Diagnosed by:
- Direct fecal smear
- Kato-katz technique
- Harada-Mori culture
Necator americanus / Ancylostoma duodenale
The major damage is due to the loss of blood at the site of attachment in the small intestine (0.1 - 0.3 mL/worm/day).
Blood is consumed by the worm and oozes from the site in response to an anticoagulant made by the worm.
Necator americanus / Ancylostoma duodenale
Cutaneous phase:
- Penetration of L3 to the skin
- Ground itch
- Cutaneous larva migrans (creeping eruption)
Lung Phase:
- Lung migration of L3
- Simply Lung eosinophilia (Loeffler’s syndrome)
Intestinal Phase:
- L3 > L5
- Up to 200mL of blood may be lost per day. Iron deficiency (microcytic hypochromic) anemia - weakness and pallor
- Protein malnutrition (hypoalbuminemia)
Necator americanus / Ancylostoma duodenale
Treatment of choice for Necator americanus / Ancylostoma duodenale
Albendazole
Common name: Whipworm
Trichuris trichiura
Soil-transmitted helminth (STH)
Inhabits the large intestine. Transmitted by ingestion of embryonated eggs.
Trichuris trichiura
Diagnostic stage: unembryonated eggs
Diagnostic test:
- Direct fecal smear
- Kato-katz technique (lemon-shaped or barrel-shaped eggs with bipolar plugs/football-shaped eggs)
Trichuris trichiura
Burrow their hairlike anterior ends into the intestinal mucosa.
Does NOT cause significant anemia.
Trichuris trichiura
Symptoms:
- Diarrhea
- Rectal prolapse (from increased peristalsis to expel the worms)
Trichuris trichiura
Treatment for Trichuris trichiura
Mebendazole
Common name: Pinworm/Seatworm/Enterobiasis/Oxyuriasis
Enterobius vermicularis
Soil-transmitted helminth (STH)
Life cycle is confined to humans.
MC STH in developed countries. A cosmopolitan worm.
Habitat: Large Intestine
Enterobius vermicularis
Transmitted by ingestion of embryonated eggs
Enterobius vermicularis
Diagnostic stage: Eggs on perianal folds.
Diagnostic test:
- Graham’s scotch / cellulose tape test (D-shaped ovum with thin colorless cell wall)
Enterobius vermicularis
Female releases thousands of fertilized eggs on perianal skin
Eggs develop into larvae, causing anal pruritus.
Autoinfection can occur.
Enterobius vermicularis
Spectrum of disease:
- Pruritus ani
- Eosinophlic enterocolitis
- Vulvovaginitis
- Salpingitis
- Appendicitis (oxuriasis)
Enterobius vermicularis
Treatment of choice for Enterobius vermicularis
Pyrantel Pamoate
Common name: Strongyloidiasis
Strongyloides stercoralis
Soil-transmitted helminth (STH)
Facultative parasites
Only helminth that causes greater pathology in AIDS patients
Strongyloides stercoralis
Transmitted by skin penetration of filariform larva (L3)
Strongyloides stercoralis
Diagnostic stage: Rhabtidiform (L1)
Diagnostic Test:
- Harada-Mori culture
(distinguished by their prominent genital primordium and a pointed tail)
Strongyloides stercoralis
Larvae penetrate intestinal wall directly without leaving host and migrate to the lungs (autoinfection)
Strongyloides stercoralis
Cutaneous Phase:
- Penetration of L3 to the skin
- Acute: Ground Itch
- Chronic: serpiginous track (larva currens)
Lung Phase:
- Lung migration of L3
- Acute: Loeffler’s syndrome
- Chronic: Paradoxical asthma
Intestinal Phase:
- Mild watery diarrhea
- Burrowing into the mucosa and submucosa - ulceration and sloughing - duodenitis
Disseminated strongyloidiasis: hyperinfection syndrome (in immunocompromised)
Strongyloides stercoralis
Common worm: Pudoc Worm / Capillariasis / Mystery Disease / Wasting Disease
Capillaria philippinensis
Intestinal nematode
Only nematode whose life cycle involves a migratory bird
Capillaria philippinensis
Transmitted by ingestion of infected fish with L3 larvae
Capillaria philippinensis
Diagnostic stage: Unembryonated egg
Diagnostic test:
- Direct fecal smear
- Kato-katz technique (Peanut-shaped eggs with flattened bipolar plugs)
Capillaria philippinensis
Embryonated eggs can cause autoinfection and hyperinfection
Ulcerative and compressive degeneration of enterocytes - severe malnutrition
Capillaria philippinensis
Acute disease:
- Borborygmi - fever, abdominal pain, eosinophilia
Chronic disease:
- Chronic watery diarrhea
- Edema, wasting
- Protein-losing enteropathy
- Hypogammaglobulinemia
Capillaria philippinensis
Treatment of choice for Capillaria philippinensis
Albendazole
Disease: Filariasis
Blood and tissue nematode
Most delibitating nematode infection.
Wuchereria bancrofti / Brugia malayi
Transmitted by mosquito bite. Infective stage: third-stage larva (L3)
Diagnostic stage: Microfilariae (L1)
Diagnostic test:
- Thick blood smear - curved or kinky microfilariae
- Specimen collection - best done at night between 8 PM and 4 AM - nocturnal periodicity
- DEC provocation test
Wuchereria bancrofti / Brugia malayi
Pathogenesis: Adult worms in the lymph nodes > inflammation > lymphatic obstruction > lymphedema
Wuchereria bancrofti / Brugia malayi
Acute disease:
- Acute adenolymphangitis
- Filarial fever
- Nocturnal wheezing (tropical pulmonary eosinophilia)
- Expatriate syndrome
Chronic disease:
- Hydrocele
- Elephantiasis
- Milky Urine (chyluria)
Wuchereria bancrofti / Brugia malayi
Treatment of choice for Wuchereria bancrofti / Brugia malayi
Diethylcarbamazine
Disease: Trichinosis
Trichinella spiralis
Tissue nematode. IH: Pigs
Transmitted by undercooked pork. Infective & Diagnostic stage Encysted larvae.
Trichinella spiralis
Diagnostic test:
- Muscle biopsy - most definitive; larvae within striated muscle
- Elevated CPKs
- Xenodiagnosis
- Bentonite Flocculation test
Trichinella spiralis
Pathogenesis:
- Intestinal stage - liberated from pork by gastric juices
- Muscle stage - disseminated hematogenously to striated skeletal muscle > encysted within a host-derived cell (nurse cell)
Trichinella spiralis
Mild Disease:
- Fever, muscle pain (myalgia)
- Periorbital edema
- Eosinophilia
- Hemorrhagic phenomena (subconjunctival splinter)
Severe Disease:
- Myocarditis
- Encephalitis
- Pneumonia
- Respiratory myositis
Trichinella spiralis
Treatment of choice for Trichinella spiralis
Thiabendazole
Found in: Sorsogon, Albay, Samar, Mindoro, Leyte, Marinduque, Palawan, Romblon, Camarines, All of Mindanao
Bancroftian Filariasis
