Helminthes Diseases

• Trematodes


  Flat, leaf-shaped and unsegmented flatworms that are hermaphroditic
• Nematodes


  Cylindrical worms with lips, teeth and dentary plates that are either male or female
• Cestodes


  Segmented, hermaphroditic tapeworms with a sucker and a projecting, hooked rostellum
• Trichinella spiralis life cycle

  1. Cycle of carnivorism among hogs and rats

  2. Humans ingest encysted larvae in infected, undercooked pork

  3. Larvae exist in stomach and burrow into small intestinal mucosa

  4. Adult males and female reemerge and produce larvae which penetrate intestine and circulate in bloodstream

  5. Larvae enter skeletal muscle cells and encyst
• Clinical features of trichinosis

  • Muscle pain and tenderness
  • Fever +/- chills
  • Abdominal pain
  • Edema (often periorbital)
  • +/- chronic neurologic/myocardial symptoms
• Diagnosis of trichinosis


  • Blood tests showing increase in eosinophils or antibodies
  • Muscle biopsy to look for larvae
• Treatment of trichinosis


  1. Antihelminthic (albendazole) to kill worms and larvae

  2. Steroids to relieve inflammatory reactions

  3. Antipyretics to relieve muscle pain
• Urinary schistosomiasis


  Caused by S. haematobium, symptoms include gross haematuria, dysuria, bladder/ureters/kidneys damage, bladder cancer
• Intestinal schistosomiasis


  Caused by S. mansoni and S. japonicum, symptoms include gradual enlargement of liver and spleen, hypertension of abdominal blood vessels, blood in stools
• Diagnosis of schistosomiasis


  • Microscopy of urine sediment or stool samples
  • Serology
  • Rectal biopsy
• Treatment of schistosomiasis


  1. Praziquantel: effective against all species

  2. S. haematobium: single dose (40 mg/kg)

  3. S. mansoni, S. japonicum: 2-3 doses of 30mg/kg
• Epidemiology of schistosomiasis


  • 200m people in 74 countries infected, 85% in sub-Saharan Africa
  • S. haematobium - Africa and middle east (most prevalent)
  • S. Mansoni - Africa and Latin America
  • S. japonicum – Pacific region
• Pathology of schistosomiasis


  Schistosoma eggs become trapped in tissues of urinary tract and intestines, causing inflammatory response and tissue damage
• Clinical features of schistosomiasis

  • Cercarial dermatitis
  • Intestinal schistosomiasis
  • Hepatosplenic schistosomiasis
  • Urinary schistosomiasis
  • Other (cardiopulmonary, CNS, etc.)
• Mechanism of praziquantel


  Increases permeability of adult parasite, causing tetanospasm and death
• Definitive hosts


  Harbor adult worms
• Intermediate hosts


  Harbor tissue cysts (containing worm heads)
• Ways humans acquire tapeworm infection

  • Ingestion of eggs from feces (to acquire tissue cysts)
  • Ingestion of tissue cysts in undercooked meat (to acquire a tapeworm)
• Intestinal taeniasis


  Caused by Taenia solium (pork tapeworm) or Taenia saginata (beef tapeworm), acquired by ingesting larvae (cysticerci) in raw/undercooked beef/pork
• Cysticercosis


  Caused by Taenia solium, acquired by fecal-oral ingestion of eggs from humans with intestinal taeniasis, can cause cysts in brain and seizures
• Epidemiology of cysticercosis


  • Approximately 50 million people worldwide are estimated to have cysticercosis infection
  • Endemic in many regions of Central and South America, sub-Saharan Africa, India, and Asia
• Treatment of cysticercosis


  Antihelminthic therapy (e.g., Albendazole+ corticosteroids, Praziquantel)
• Prevention of cysticercosis


  • Health education
  • Avoid pig eating human stool
  • Sanitary inspection of slaughter and sanitary disposal of night soil
• Treatment of echinococcosis


  1. Surgical removal

  2. Irrigation-evacuation of cysts

  3. Chemotherapy

  4. PAIR (percutaneous aspiration, injection of chemicals and reaspiration)
• Prevention of echinococcosis


  • Deworming of dogs
  • Slaughterhouse hygiene
  • Public education campaigns
  • Vaccination of lambs
• Lymphatic filariasis


  120m people infected in >80 countries, 95% cases due to Wuchereria bancrofti, causes severe lymphatic damage and elephantiasis
• Pathology of lymphatic filariasis

  Adult worms live in lymphatic vessels, causing severe disruption to the lymphatic system, leading to elephantiasis
• Stages of lymphatic filariasis

  • Asymptomatic stage
  • Acute stage - Filarial lymphangitis
  • Chronic stage - Elephantiasis
• Diagnosis of lymphatic filariasis


  • Microscopic examination of blood for microfilariae
  • Serology
• Treatment of lymphatic filariasis

  1. Diethylcarbamazine (DEC) to kill microfilariae and adult worms

  2. Add antihistamine and aspirin to manage allergic reactions
• Enterobiasis


  Caused by Enterobius vermicularis (pinworm), most common helminthic infection in US, primarily affects children 5-10 years old
• Trichiuriasis


  Caused by Trichuris trichiura (whipworm), mostly asymptomatic but can cause diarrhea, anemia, growth retardation in children
• Ascariasis


  Caused by Ascaris lumbricoides (roundworm), most common helminth infection worldwide, affects children in tropics/developing countries
• Clinical features of ascariasis

  • Early symptoms: dry cough, blood-tinged sputum, wheezing (Löffler syndrome)
  • Later symptoms: intestinal obstruction, malnutrition
• Diagnosis of ascariasis


  • Initial test: eosinophilia on CBC
  • Confirmatory test: stool sample showing worms or eggs
• Treatment of ascariasis


  Bendazoles and Pyrantel Pamoate