Helminths

The Helminths section provides High Yield Information needed for USMLE, COMLEX, Medical School, Residency, and as a practicing Physician.

Cestodes

Diphylobothrium Latum

• Features:
  • Fish tapeworm
    
  • Largest tapeworm: up to 10 meters long
    
• Transmission:
  
  • – Eating raw or undercooked fish
    
• Presentation:
  
  • – Diarrhea
    
  • – Megaloblastic anemia: due to association with vitamin B12 deficiency
    
• Diagnosis:
  
  • – Stool ova and parasite test
    
• Treatment:
  
  • – Praziquantel
    
  • – Niclosamide

Echinococcus Granulosus

• Features:
  • Sheep tapeworm
  • Dogs: definitive host, sheep: intermediate
  • Humans: incidental host
• Transmission:
  • Dog feces
• Clinical presentation:
  • – Hydatid cyst in liver: Slow growing, egg shell calcification on liver CT
  • Rupture–> anaphylactic reaction and acute abdomen
• Diagnosis:
  • Eosinophilia
• Treatment:
  • – Surgery: inject cyst with ethanol or hypertonic saline to kill cells before attempting to remove cysts

Enterobius Vermicularis

• Features:
  • “Pinworm”
    
• Transmission:
  • Fecal oral
    
• Typically affects:
  • children
    
• Presentation:
  • itchy anus
    
• Diagnosis:
  • Scotch tape test
    
• Treatment:
  
  • – Pyrantel pamoate
    
  • – Albendazole

Taenia

• Features:
  • Taenia solium and saginata
  • solium- pig, saginata- beef
• Transmission:
  • – Eating cysts or larvae in undercooked meat–> GI problems
• Clinical presentation:
  • – Taeniasis-> GI problems ingestion of larvae or cyst
  • – Cysticercosis-> ingestion of taenia eggs – anywhere in the body
  • – Neurocysticercosis- taenia cestodes- drinking contaminated water with eggs. Seizures or Hydrocephalus. Swiss cheese on CT
• Diagnosis:
  • – Stool ova and parasite test
  • – T solium: hooks on proglottid
  • – T saginatum- no hooks
• Treatment:
  • – Praziquantel
  • – Albendazole

Nematodes

Ancylostoma and Necator

• Features:
  • Hookworms
    
  • Endemic to rural southern US
    
• Transmission:
  
  • – Walking barefoot- penetrate skin
    
  • – Bloodstream–> matures in intestines
    
• Presentation:
  • Severe iron deficiency anemia
    
• Diagnosis:
  • eggs in stool and high eosinophil count
    
• Treatment:
  
  • – Pyrantel pamoate
    
  • – Abendazole

Ascaris Lumbricoides

• Features:
  • Giant Round Worm
• Transmission:
  • – Eating eggs in contaminated food or water
• Clinical presentation:
  • – Some asymptomatic
  • – Malnutrition
  • – Respiratory problems
• Complication:
  • – Intestinal obstruction: common at ileocecal valve
• Diagnosis:
  • – Eggs in stool
  • – High eosinophil count
• Treatment:
  • – Albendazole

Dracunulus Medinensis

• Features:
  • Tissue nematode
    
• Transmission:
  
  • – Drinking contaminated water with copepods containing larvae
• Diagnosis:
  • Adult females emerging from painful ulcers in skin. Peripheral eosinophilia
    
• Treatment:
  
  • – Slowly extracting worm with a small stick
    
  • – Metronidazole

Loa Loa

• Features:
  • African Eye Worm
  • From the swamp
• Transmission:
  • Deer fly- vector
  • Deer fly migrates through subcutaneous tissue -> transient angioedema-> local subcutaneous swellings
• Presentation:
  • – Adult worms: conjunctivia
  • – Eosinophilia
• Diagnosis:
  • Microfilariae seen on blood smear
• Treatment:
  • – Diethylcarbamazine
  • – Albendazole

Onchocera Volvulus

• Features:
  • Onchodermatitis
• Transmission:
  • Black flies
  • Found in Rivers in Africa, Central and South America
• Clinical presentation:
  • – Scattered pruritic papules that become hyperpigmented
  • – Hypopigmented spots seen on shins of elderly patients
  • – Blindness due to microfilaria in eyes “Riverblindness”
  • – Eosinophilia
• Diagnosis:
  • – Microfilariae seen in skin biopsy
• Treatment:
  • – Ivermectin

Strongyloides Stercoralis

• Features:
  • Helminth/Nematode
    
• Transmission:
  
  • – Larvae penetrate skin of soles of feet – bloodstream–> lungs–> GIT
    
  • Immunocompromised: can lead to hyperinfection and dissemination of worms
    
• Diagnosis:
  
  • – Larvae in stool (Not eggs)
    
  • – High eosinophil count
    
• Treatment:
  
  • – Abendazole
    
  • – Ivermectin

Toxocara Canis

• Features:
  • Viscera larva migrans
    
• Transmission:
  • Contaminated food with dog or cat feces
    
  • Parasitic larvae doesn’t mature in humans. Continues to circulate in body for years
    
• Clinical presentation:
  
  • – Ocular larval migrans–> blindness
    
  • – Eosinophilia
    
• Treatment:
  • Albendazole

Trichinella Spiralis

• Features:
  • Intestinal nematode found in undercooked meat like pig and bear
    
• Clinical presentation:
  
  • Wide range of symptoms:
    
    • – Fever
      
    • – Vomiting
      
    • – Periorbital edema
      
    • – Severe myalgias and muscle aches: formation of cyst in striated muscle cells
      
• Diagnosis:
  
  • – Eosinophilia
    
• Treatment:
  
  • – Albendazole

Wuchereria Bancofti

• Features:
  • Elephantiasis: complication of long standing lymphedema
    
• Clinical Presentation:
  
  • – Cough from microfilariae in lungs: hypersensitivity reaction
    
• Transmission:
  
  • – Mosquito: vector
    
• Diagnosis:
  
  • – Thick blood smear
    
  • – Eosinophilia
    
• Treatment:
  
  • – Diethylcarbamazine

Trematode (Flukes)

Clonorchis Sinensis

• Features:
  • Chinese liver fluke
• Host:
  • snail
  • Worms in uncooked fish
• Transmission:
  • eating uncooked fish with worms
  • Resides in biliary system
• Presentation:
  • – Biliary tract fibrosis
  • – Pigmented gallstones
  • – Cholangiocarcinoma
• Diagnosis:
  • – operculated eggs in stool and ova parasite test
• Treatment:
  • – Praziquantel

Paragonimus Westermani

• Features:
  • Lung flukes
    
• Transmission:
  • consumption of raw or undercooked crabmeat that carry larvae
    
• Presentation:
  
  • – Chronic cough with bloody sputum especially if parasitic load is high
    
• Diagnosis:
  
  • – Stool ova and parasites: operculated eggs
    
• Treatment:
  
  • – Praziquantel

Schistosoma

• Features:
  • Trematode
• 3 species:
  • – Mansoni
  • – Japonicum
  • – Haematobium
• Causes:
  • schistosomiasis
• Transmission:
  • Cercaria penetrating skin in an aquatic environment –> blood stream
  • Migration against portal blood flow
  • Mansoni and japonicum reside in mesenteric veins
  • Hematobium reside in veins of bladder
  • Risk: swimmers
• Clinical manifestations:
  • – Swimmers itch
  • – Chronic infections: mansoni and japonicum: portal hypertension -> GI hemorrhage and abdominal pain–> cirrhosis and liver faliure haematobium: bladder related symptoms, migration against portal venous flow, hematuria, associated with bladder cancer
• Treatment:
  • – Praziquantel