Worms in humans

Introduction

Worm infestations in humans, also known as helminth infections, represent a significant global health problem, particularly in developing regions with poor sanitation and hygiene. They are caused by a wide range of parasitic worms that inhabit the human gastrointestinal tract and, in some cases, migrate to other organs such as the liver, lungs, or bloodstream. These infestations can lead to malnutrition, anemia, impaired growth in children, and chronic morbidity.

The major classes of helminths affecting humans are:

• Nematodes (roundworms) – e.g., Ascaris lumbricoides, Enterobius vermicularis, Ancylostoma duodenale

• Cestodes (tapeworms) – e.g., Taenia saginata, Taenia solium, Diphyllobothrium latum

• Trematodes (flukes) – e.g., Schistosoma species, Fasciola hepatica

Each type of worm has distinct life cycles, clinical manifestations, and management protocols.

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Common Types of Worms in Humans and Associated Diseases

1. Nematodes (Roundworms)

• Ascariasis (Ascaris lumbricoides)

  • Most common intestinal helminth worldwide.

  • Symptoms: abdominal pain, bloating, malnutrition, growth retardation in children, bowel obstruction in heavy infections.

  • Migration phase may cause Löffler’s syndrome (cough, wheezing, pulmonary infiltrates).

• Enterobiasis (Pinworm, Enterobius vermicularis)

  • Extremely common in children.

  • Symptoms: intense perianal itching, especially at night; disturbed sleep.

• Hookworm (Ancylostoma duodenale, Necator americanus)

  • Penetrate skin, travel to lungs, and then the intestines.

  • Cause chronic intestinal blood loss, leading to iron-deficiency anemia.

• Trichuriasis (Whipworm, Trichuris trichiura)

  • Symptoms: chronic diarrhea, rectal prolapse in heavy infections.

• Strongyloidiasis (Strongyloides stercoralis)

  • May cause persistent diarrhea, abdominal pain, and in immunocompromised patients, life-threatening hyperinfection syndrome.

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2. Cestodes (Tapeworms)

• Taeniasis (Taenia saginata and Taenia solium)

  • Acquired from undercooked beef (T. saginata) or pork (T. solium).

  • Usually asymptomatic or mild GI upset.

  • T. solium eggs can cause cysticercosis when larvae invade tissues, including the brain (neurocysticercosis → seizures, headaches).

• Diphyllobothriasis (Diphyllobothrium latum)

  • Fish tapeworm infection.

  • Associated with vitamin B12 deficiency leading to megaloblastic anemia.

• Hymenolepiasis (Hymenolepis nana)

  • The most common tapeworm infection in children.

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3. Trematodes (Flukes)

• Schistosomiasis (Schistosoma mansoni, S. haematobium, S. japonicum)

  • Transmitted via freshwater snails.

  • Symptoms: bloody diarrhea (S. mansoni), hematuria and bladder fibrosis (S. haematobium), hepatosplenic disease with portal hypertension (S. japonicum).

• Fascioliasis (Fasciola hepatica)

  • Liver fluke acquired from contaminated water plants.

  • Symptoms: fever, right upper quadrant pain, hepatomegaly.

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Diagnosis

• Stool Examination: Microscopy to detect eggs or larvae.

• Cellophane Tape Test (Scotch Tape Test): Used for Enterobius vermicularis.

• Blood Tests: Eosinophilia common in helminth infections.

• Serological Tests: Helpful in extraintestinal parasitic infections (e.g., cysticercosis, schistosomiasis).

• Imaging: CT/MRI in neurocysticercosis; ultrasound for liver flukes.

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Treatment

Treatment depends on the type of worm. The World Health Organization recommends anthelmintic drugs as first-line therapy.

Broad-Spectrum Anthelmintics

• Albendazole

  • Dose: 400 mg orally once daily for 1–3 days depending on infection.

  • Effective against Ascaris, Trichuris, hookworms, Enterobius.

• Mebendazole

  • Dose: 100 mg orally twice daily for 3 days, or 500 mg single dose (for many nematodes).

• Pyrantel Pamoate

  • Dose: 11 mg/kg orally as a single dose (max 1 g).

  • Used for pinworm, roundworm, hookworm.

Specific Treatments

• Enterobiasis (Pinworm):

  • Albendazole 400 mg single dose, repeat in 2 weeks.

  • All household contacts should be treated.

• Ascariasis:

  • Albendazole 400 mg once daily for 3 days OR Mebendazole 100 mg twice daily for 3 days.

• Hookworm:

  • Albendazole 400 mg daily for 3 days + Iron supplementation if anemia present.

• Strongyloidiasis:

  • Ivermectin: 200 μg/kg orally once daily for 1–2 days.

• Trichuriasis:

  • Mebendazole 100 mg twice daily for 3 days.

• Taeniasis (Adult Tapeworms):

  • Praziquantel: 5–10 mg/kg orally once.

• Cysticercosis:

  • Albendazole 15 mg/kg/day orally (divided doses) for 8–15 days + corticosteroids (prednisone 1 mg/kg/day) to reduce inflammation.

• Diphyllobothriasis:

  • Praziquantel 5–10 mg/kg orally single dose.

  • Vitamin B12 supplementation if deficient.

• Schistosomiasis:

  • Praziquantel 40 mg/kg orally in 2 divided doses in one day.

• Fascioliasis:

  • Triclabendazole: 10 mg/kg orally as a single dose (repeat after 12–24 hours if necessary).

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Precautions and Monitoring

• Albendazole/Mebendazole: Contraindicated in pregnancy (first trimester). Use with caution in liver disease; monitor liver enzymes during prolonged therapy.

• Praziquantel: May cause dizziness, abdominal discomfort; avoid in ocular cysticercosis.

• Ivermectin: Avoid in children under 15 kg and in pregnancy; CNS adverse effects in high doses.

• Iron Therapy: For hookworm-induced anemia, monitor hemoglobin and ferritin.

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Drug Interactions

• Albendazole + Dexamethasone: Increases albendazole sulfoxide levels.

• Albendazole + Cimetidine: Increases albendazole plasma concentrations.

• Praziquantel + Rifampicin: Rifampicin reduces praziquantel effectiveness.

• Ivermectin + CNS Depressants (benzodiazepines, alcohol): May increase CNS toxicity.

• Mebendazole + Metronidazole: Reported risk of Stevens–Johnson syndrome.

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Public Health and Prevention

• Improving sanitation and access to clean water.

• Regular deworming programs in endemic areas (Albendazole or Mebendazole given twice yearly to school-aged children).

• Hand hygiene and proper cooking of meat/fish.

• Health education campaigns to reduce reinfection.