Nematodes are roundworm parasites that infect humans through ingestion of eggs or larvae from contaminated food, water or soil. They can infect the gastrointestinal tract, tissues, or lymphatic system. Common nematode infections include ascariasis, trichuriasis, hookworm infection, strongyloidiasis and trichinellosis. Diagnosis involves examining stool samples under a microscope for eggs or larvae. Treatment involves anthelmintic medications like mebendazole or albendazole. Follow up is important for cases of strongyloidiasis to prevent hyperinfection from chronic autoinfection.

1. Summary Nematodes

2. Habitat
• Trichuris trichura.
• Entrobius vermicularis.
Large intestine Nematode
• Ascaris lumbricoides
• Ancylostoma duodenale/ Necator americanus (hookworms)
• Strongloydes sterclosis
• Trichinella spiralis
• Capillaria phillpeninsis
Small intestine Nematode
• Wuchereria bancrofti
• Brugia malayi
• Loa loa
• Onchocerca volvulus
• Mansonella ozzardi/perstans
Tissue nematode
Soil transmitted nematodes: Ascaris, anclystoma/nector, and trichuris

3. Nematode Geographical Distribution
Trichuris trichura. Worldwide
Entrobius vermicularis. Worldwide
Ascaris lumbricoides Worldwide, (Most common helminthic human infection)
Ancylostoma duodenale Worldwide, Tropics & subtropics and some temperate zones. (2nd most common helminth after Ascaris)
Necator americanus Worldwide, North and South America, Central Africa, Indonesia, islands of the South Pacific, and parts
of India
Trichinella spiralis Worldwide
Capillaria phillpeninsis Philippines, Thailand and Southeast Asian
Strongloydes sterclosis Tropical and Subtropical areas
Geographical Distribution:

4. Species D.H. I.H. I.S D.S.
T. trichura Human is the only host N/A Embryonated eggs Immature (Non-Embryonated) eggs
E. vermicularis Human is the only host N/A Embryonated eggs Embryonated eggs
A. lumbricoides Human is the only host N/A Embryonated (mature) egg
Containing a (L2) 2nd stage Rh larva
Immature (Non-Embryonated) eggs:
Fertilized, unfertilized and/or
decorticated
A. duodenale/N.
americanus
Human is the only host N/A Flariform larva L3 Immature eggs
T. spiralis Human/pigs N/A Encysted larva in pigs Encysted larva in straited muscles
C. phillpeninsis Human Freshwater fish Flariform larva L3 ASK PROF Embryonated eggs
S. sterclosis Human is the only host N/A Flariform larva L3 Rhabditiform larva L2
Hosts: The only nematode with intermediate host is capillaria

5. Nematode Mode of Transmission
T. trichura Ingestion of the (mature) eggs in contaminated food, water & hands by human feces. (Feco-oral)
E. vermicularis Heteroinfection: Ingestion of contaminated food or water with mature eggs
External autoinfection: using contaminated hands with eggs to mouth for eating (feco-oral)
Retroinfection: eggs hatch larva in perianal area and migrates back through anaus
Airborne: eggs in dust inhaled & swallowed
A. lumbricoides Ingestion of the (mature) eggs in contaminated food, water & hands by human feces. (Feco-oral)
N.B: eggs passed in soil are not immediately infectious  needs 18-30 d to embryonate and maturate in humid & aerobic environment
Hookworms L3 larvae penetration of the skin or mucus membrane. [eggs passed in soil are not immediately infectious  larvae hatch in 1-2 d &
become rh larva L2  L2 grow in feces and/or the soil after 5-10 days  become L3 larvae that can survive 3-4 w in environments (I.S.)]
N.B: Infection by A. duodenale may probably also occur by the oral and the transmammary route.
T. spiralis Ingestion of undercooked meat containing encysted larvae (pigs)  After exposure to gastric acid and pepsin, the larvae are released
from the cysts  then invade the small bowel mucosa where they develop into adult worms.
C. phillpeninsis Heteroinfection: Ingestion of raw or undercooked fish containing larvae
Internal autoinfection: females can produce embryonated eggs lacking shells that hatch inside D.H. causing internal autoinfection and may
lead to hyperinfection if the worms load is very high.
S. sterclosis Heteroinfection: Filariform larvae in contaminated soil penetrate human skin when skin contacts soil  migrate to the small intestine
External autoinfection: Rhabditiform larvae in the gut become infective filariform larvae  penetrate the skin of the perianal area.
Internal autoinfection: Rhabditiform larvae in the gut become infective filariform larvae  penetrate the intestinal mucosa
N.B.: Once the filariform larvae re-infect the host, they are carried to the lungs, pharynx and small intestine or disseminate throughout the body. The
significance of autoinfection in Strongyloides is that untreated cases can result in persistent infection, even after many decades of residence in a non-endemic
area, and may contribute to the development of hyperinfection syndrome.
Mode of Transmission: Soil transmitted nematodes: Ascaris, anclystoma/nector, and trichuris

6. Nematode Main Diagnosis Additional Testing/Comments
T. trichura Coproscopy:
Immature eggs
CBC will show:
• Trichocephalic Anaemia: (microcytic Hypochromic: due to blood suction by
parasite + bleeding) and Macrocytic Hyperchromic: by worms Toxic by-products
• Persistent Eosinophilia ASK PROF
E. vermicularis • Perianal preparation (Paddle test) or anal swabs:
best yield samples, detects 95%.
• Coproscopy: only detects 5%.
• Anal examination for adult worms.
• Eggs can be found accidently in urine
• Enterobiasis should be suspected in patients with anal pruritis, particularly
school-aged children.
A. lumbricoides • Coproscopy: mature or immature (all forms)
• Larva could be found in gastric aspirates,
endoscopy samples or sputum. (during pulmonary
migration)
• Adults could be found per rectum, or nose/mouth
• CBC will show: Eosinophilia in acute stage (larval migration to lungs)
• Plain X-ray: adults may be visible, gas filled loops
• Barium meal: filling defect by adult
• US, CT, and/or ERCP will reveal adults + inflammatory pathology in biliary tree.
Hookworms Coproscopy:
Immature eggs
• Fecal egg excretion becomes detectable about eight weeks after dermal
penetration of N. americanus infection and up to 38 weeks after dermal
penetration of A. duodenale
• CBC will show: Eosinophilia in acute stage (larval migration to lungs); microcytic-
hypochromic anemia
Diagnosis:

7. Nematode Main Diagnosis Additional Testing/Comments
T. spiralis • History: food poisoning like disease + Muscle pain
, eyelid edema
• Serology: EIA detects Trichinella-specific
antibodies (best sensitivity), ELISAs, dot-ELISAs,
indirect immunofluorescence, and latex
agglutination.
• Antigen test: have relatively poor sensitivity <50%
• Muscle biopsy: A definitive diagnosis may be
established by identifying larvae on muscle biopsy.
• Skin test (bakhman test)
• CBC will show Eosinophilia
• Positive serology sensitivity in serum samples of 80% to 100% of patients with
clinically symptomatic trichinellosis.  results confirm with a Western blot
• Antibody levels are often not detectable until 3 to 5 weeks post-infection. (paired
samples is important if initial is negative)
• Antibody development is affected by the infecting dose of larvae  the higher the
infecting dose, the faster the antibody response will develop.
• IgG, IgM, and IgE antibodies are detectable in many patients; however, tests based
on IgG antibodies are most sensitive. Antibody levels peak in the 2nd or 3rd month
post-infection and then decline slowly for several years.
C. phillpeninsis • Coproscopy: eggs, larvae and/or adult worms
• Intestinal biopsy: eggs, larvae and/or adult worms
No valid serologic testing is available for diagnosis.
• A protein-losing enteropathy can develop which may result in complications such
as cardiomyopathy, severe emaciation, cachexia, and death.
• Unembryonated eggs are the typical stage found in the feces.
• In severe infections, embryonated eggs, larvae, and even adult worms can be
found in the feces.
S. sterclosis • Coproscopy: Rh larvae.
• Dudenal aspirate: Rh larvae (>sensitive than stool)
• Sputum or Lower RT sample: FL Larvae
• Eosinophilia in acute stage (larval migration to
lungs)
• Agar plate culture: culture of sample 48% 
detect FL larvae.
• Serology: ELISA, IFA gelatin particle agglutination,
and immunoblot for IgG. (high NPV)
• PCR or LAMP: variable performance
• Sensitivity of coproscopy is relatively low (<50 %) given intermittent larval
excretion. (Serial examination > 7 samples, the sensitivity approach 100 %)
• Larvae may be detectable in stool three to four weeks after dermal penetration.
• Agar plate culture (most sensitive), sedimentation concentration, Baermann
concentration with charcoal culture, and Harada-Mori filter paper technique
increase the sensitivity of stool examinations.
• Disadvantages of serology: Cross-reactivity with filaria or other soil-transmitted
helminths, diminished sensitivity in patients with hematologic malignancy or
human T-lymphotropic virus type I infection, inability to distinguish between
current and prior infection, and lack of standardization across centers
Diagnosis: Triad of trichinellosis: periorbital edema, myositis, and eosinophilia

8. Treatment:
Nematode Treatment Comments
T. trichura • Mebendazole (adults and children: 100 mg orally twice daily
for three days) OR
• Albendazole (adults and children: 400 mg orally once daily
for three days)
• For patients with heavy infection (at least 1000 Trichuris eggs/g stool), a longer duration of
albendazole (five to seven days).
• Give antidiarrheal before treatment
E. Vermicularis • Albendazole (adults and children: 400 mg orally once on
empty stomach, repeat in two weeks) OR
• Mebendazole (adults and children: 100 mg orally once,
repeat in two weeks) OR
• Pyrantel pamoate (adults and children: 11 mg/kg, maximum
1 g; repeat in two weeks)
• Repeat the dose after 2-3 weeks because the drug will kill the adults only. To avoid autoinfection.
• Treat the family
• White oxide of mercury ointment preffered to perianal region: relieve itching, kill females &
prevent egg dispersal.
A. lumbricoides • Mebendazole (adults and children: 100 mg orally twice daily
for three days or 500mg one dose) OR
• Albendazole (adults and children: 400 mg orally one dose;
can be extended for three days)
• Pyrantel pamoate (adults and children: 11 mg/kg, maximum
1 g; repeat in two weeks) for pregnant.
All drugs have high cure rate (>96%)
• Intestinal obstruction should be managed conservatively, with NG suction and repletion of fluids
and electrolytes; once bowel motility is restored, anthelminthic therapy should be administered.
• Indications for surgery: complete obstruction with inadequate decompression, lack of clinical
response within 24 to 48 hours, volvulus, intussusception, appendicitis, or perforation.
• Anthelminthic therapy helps reduce morbidity associated with Ascaris infection but does not
prevent reinfection and active against adult worms but not against larvae.
Hookworms • Mebendazole (adults and children: 100 mg orally twice daily
for three days or 500mg one dose) OR
• Albendazole (adults and children: 400 mg orally one dose;
can be extended for three days)
• Pyrantel pamoate (adults and children: 11 mg/kg, maximum
1 g; repeat in two weeks) for pregnant.
• Iron replacement for anemia

9. Treatment:
Nematode Treatment Comments
T. spiralis • Most infections is uncomplicated and self-limited. For mild
infection, antiparasitic therapy is not required; symptomatic
treatment with analgesia and antipyretics is appropriate.
• For systemic disease: (with CNS involvement)
• Mebendazole (200 to 400 mg TID for 3 days, then 400 to 500
mg TID for 10 days) OR
• Albendazole (400 mg with fatty meal BID for 10 to 14 days) +
• Prednisone in severe cases (30 to 60 mg/day for 10 to 15d)
C.
phillpeninsis
• Albendazole (400 mg on empty stomach once daily, often
given for 30 days [minimum 10 days]) OR
• Mebendazole (200 mg twice daily for 20 to 30 days)
• Supportive therapy with fluids and nutritional supplements may be required.
• Relapse is common (because autoinfection), particularly if patients do not complete the full
course of therapy; in such cases, retreatment may be necessary
S. sterclosis • Uncomplicated disease:
• Ivermectin (200 mg/kg/day 1 dose for 1-2 days) DOC OR
• Thiabendazole (25 mg/kg per day for 3 days) OR
• Albendazole (400 mg orally BID for 3-7 days)
• Severe (hyperinfection) disease:
• Stop immunosuppressive therapy.
• Ivermectin 200 mg/kg/day 1 dose (until stool and or sputum
are negative for 2 weeks)
• Combination of ivermectin and albendazole (WHO)
• Broad spectrum antiboitcs
• Treatment for all symptomatic and asymptomatic, regardless of immune status.
• The goal of treatment is cure, in order to prevent development of severe disease in the context of
chronic autoinfection.
• Repeat dose at 0,1,2 months for all treatment. ASK PROF
• Among patients with hyperinfection/disseminated infection, the mortality rate is up to 70 to 100
percent; Factors that increase the likelihood of mortality include concomitant
immunosuppression, bacteremia, and delayed diagnosis.
Follow Up notes is important (see next slide)

10. FOLLOW UP IN STRONGLOYDIASIS CASES