Helminth Infections Flashcards
Pinworm - Pathogenesis and Presentation
Most common helminth infection in the US
Eggs ingested by fecal-oral route hatch in the small intestine and mate in the cecum; eggs are deposited and hatch in the peri-anal region causing anal pruritis
Pinworm - Diagnosis and Treatment
Diagnosed by Scotch Tape test
Treated with Mebendazole or pyrantel pamoate
Whipworm
Mostly seen in the rural South and Puerto Rico
Worm penetrates the large intestine causing infection that is mostly asymptomatic but may present with bloody diarrhea and anemia
Treated with Mebendazole or pyrantel pamoate
Ascariasis
Ova ingested from contaminated food; eggs hatch in the duodenum and travel in venous blood to pulmonary circulation; worms break into alveoli, travel into trachea, and are swallowed; worms lay eggs upon return to intestine 2-3 months later
Presents with pneumonitis (similar to asthma) + GI symptoms (obstruction, malabsorption)
Diagnosed by ova in stool
Treated with Mebendazole or Pyrantel Pamoate
Hookworm
Filariform larvae in soil penetrate human skin and travel through the blood to lungs and into airways; larvae are coughed up out of airways and swallowed, then penetrate the intestine; in the intestine they suck blood from intestinal walls
Presentation is asymptomatic or iron-deficiency anemia (with high worm burden)
Treatment - Mebendazole or Pyrantel Pamoate
Which helminth infections are coughed up from the trachea and swallowed?
Ascariasis
Hookworm
Strongyloides
Filariform larvae penetrate skin and infect mucosa of small intestine
Intestinal infection causes vomiting, diarrhea, epigastric pain; can disseminate in immunocompromised patients to lung, liver, brain
Diagnosed by ova in stool
Treated with Thiabendazole
Pork tapeworm
Ingestion of larvae encysted in undercooked pork causes intestinal infection via attachment of the scolex to the intestinal wall; can disseminate to skeletal muscle and brain (caysing cysticercosis / neurocysticercosis)
Primary intestinal infection mostly asymptomatic (adominal discomfort, hunger, indigestion); neurocysticercosis presents with cerebral edema, hydrocephalus, seizures, stroke
Treated with Albendazole
Fish tapeworm
Acquired from eating under-cooked fish which have ingested infected crustaceans containing larvae
Presents with megaloblastic anemia due to Vitamin B12 deficiency (worm competes for B12 uptake in the intestine)
Treated with Praziquantel
Praziquantel - Uses
Schistosomiasis
Intestinal pork tapeworm
Fish tapeworm
Dog tapeworm (Hydatid cyst)
Ingestion of eggs in food contaminated by canine feces
Eggs hatch in intestine and form slow-growing cysts in lung and liver
Treated with albendazole; because release of antigens may cause anaphylaxis, surgical removal of cysts requires pre-injection with ethanol to kill cysts
Trichinosis
Transmitted by larvae in undercooked pork and other wild animals (bears)
Larvae are freed by acid/pepsin in the stomach and mature in the small intestine; females release larvae into the blood which encyst in skeletal muscle
Presents with GI symptoms, fever, myositis, myalgia, and periorbital edema
Dx by muscle biopsy
Uses of Albendazole
Neurocysticercosis (pork tapeworm) Hydatid cyst (dog tapeworm)
Schistosomiasis - Pathogenesis
Infected humans deposit eggs in fresh H2O via urine/feces; eggs hatch and release miracidia, which infect snails; miracidia develop within snails into cercariae, which penetrate human skin and mature; they then migrate to the lung and liver
3 Clinical presentations:
- Dermatitis (“Swimmer’s Itch”)
- Katayama fever - acute phase inflammation due to immune-complex deposition
- Chronic fibro-obstructive sequelae
How does chronic schistosomiasis present?
Intestinal and liver disease, hepatosplenomegaly (S. mansoni and S. japonicum)
Painless hematuria, squamous cell carcinoma of the bladder (S. haematobium)
