Helminths

Question 1

Ascaria lumbricoides

Answer 1

*Ascariasis
Nematode (roundworm)
S/S: Transient cough, urticaria, abdominal pain, nausea, vomiting, worms in stool, fatigue, eosinophilia
Pathogenesis: Infective eggs ingested from fecal contaminated food/water
· Eggs –> larvae in small intestine
· Larvae penetrate intestinal walls into lymph, liver, blood, heart, lungs
· Become adults in large intestine
Organ damage due to infestation
· Bowel and bile/pancreatic duct obstruction
Lab Tests: ID eggs in stool; ID adult worms that exit mouth, nose, or anus
Imaging: Chest x-ray to ID pulmonary infiltrates (larvae in lungs)
Medication: Albendazole, Mebendazole, Pyrantel pamoate
Surgery: For appendicitis and other GI complications

Question 2

Taenia solium

Answer 2

*Pork tapeworm (Taeniasis)
Cestode (tapeworm)
Intestinal infection is most common
S/S: abdominal pain, loss of appetite, weight loss, nausea, diarrhea. Most patients are asymptomatic
Pathogenesis: Intestinal: Consume undercooked pork containing larvae –> tapeworm infection
Tissue infection: Humans ingest infective eggs. Transmission:
Hand to mouth; Person-to-person; Ingestion of water/food contaminated with fecal matter and eggs
Neurocysticercosis: Eggs migrate to brain and become cysts. This can cause seizures, dizziness, headaches.
Lab Tests: ID eggs or proglottids in stool
Imaging: MRI/CT scan for neurocysticercosis
Medication: Praziquantel
Surgery: Removal of cysts in brain tissue

Question 3

Enterobus vermicularis

Answer 3

*Pinworm
S/S: Nocturnal perianal itching, insomnia, restlessness, scratching.
Most patients are asymptomatic.
The worms come out at night (lower metabolic activity in host)
Transmission: Contact to perianal region of infected individual; Food/fomites contaminated;
Itching caused by females depositing eggs on perianal skin
Reinfection (autoinfection) can occur
Lab Tests: ID eggs on tape applied to perianal area under microscope; Nocturnal examination of perianal skin for adult worms
Medication: Pyrantel pamoate, Albendazole, Mebendazole
Therapy: Treat all close contacts to infected individual; Encourage good hygiene

Question 4

Schistosoma species

Answer 4

Common trematode name: blood flukes.
Common disease name: bilharzia
S/S : acute = fever, headache, cough, urticaria; rash
Intestinal: abdominal pain, diarrhea, hepatomegaly –> anorexia
Urinary: hematuria, dysuria
Transmission: Contact to freshwater containing infected snails
Body response can cause granuloma formation and inflammation –> fibrosis
Chronic infection = scarring of mesenteric blood vessels –> portal hypertension
Lab Tests: ID eggs from urine/stool smears; serologic tests e.g. ELISA
Procedures: Biopsy of rectum, colon, bladder to confirm disease
Medication: Praziquantel
Prevention: Avoid fresh water in endemic areas; Vigorous toweling after exposure
Follow-up: Examine for eggs every 3 months (up to a year) after therapy

Question 5

Trichinella spiralis

Answer 5

Common Nematode name: blood flukes.
Common disease name: bilharzia.
S/S: Most infections are asymptomatic.
GI: diarrhea, vomiting, abdominal pain
Systemic: fever, myalgias, periorbital edema, eosinophilia
Transmission: Ingestion of undercooked meat (most commonly pork)
Progression: Larvae freed from cyst walls –> small intestine; parasites travel via bloodstream to skeletal muscle –> cysts
Lab Tests: Elevated serum muscle enzymes; rising antibody titers, ELISA
Procedures: Muscle biopsy – larvae
Medication: No effective tx for full-blown trichinosis
Therapy: Analgesics, bed rest, antipyretics