Practice 6 structured short- and long-answer medical questions on Enterobius vermicularis and Ascaris lumbricoides. Review model answers for exam revision.
Answer: ## Introduction - **Distribution**: Worldwide, common in children and institutionalized individuals. - **Prevalence**: Most common helminthic infection globally. - **Reservoir**: Humans (no intermediate host). - **Habitat**: Adult worms reside in the caecum, appendix, and ascending colon. ## Life Cycle - **Type**: Monoxenous (entire cycle in one host). - **Infective form**: Embryonated eggs containing larvae. - **Mode of Infection**: Fecal-oral route (ingestion of infective eggs). - **Autoinfection**: Scratching the perianal area and transferring eggs to the mouth. - **Retroinfection**: Larvae hatch on perianal skin and migrate back into the colon. ### Life Cycle Stages
Answer: Model answer pending
Answer: Model answer pending
Answer: ## Pathogenesis and Clinical Features - **Pruritus ani**: Itching at night; may lead to bacterial superinfection from scratching. - **Sleep Disturbances**: Nocturnal restlessness and irritability. - **Genitourinary Involvement**: In females, can cause vulvovaginitis, salpingitis, cervicitis, and recurrent UTIs. - **Gastrointestinal**: May cause appendicitis if worms enter the appendix; abdominal pain and nausea in heavy infections. ## Diagnosis - **Stool examination**: Not reliable as eggs are laid perianally. - **Scotch Tape Method (Preferred)**: Transparent adhesive tape pressed on perianal skin in the morning. Microscopy shows oval, flat-sided eggs. - **NIH Swab Method**: Glass rod with cellophane used to swab the perianal area. - **Adult Worms**: Visible on stool surface or crawling from the anus at night. ## Treatment - **First-Line (Single dose)**: Albendazole (400 mg), Mebendazole (100 mg), or Pyrantel pamoate (11 mg/kg). - **Note**: Repeat dose after 2 weeks to kill newly hatched larvae. Treat all family members simultaneously. # Roundworm (Ascaris lumbricoides) ## Introduction - **Characteristics**: Largest human intestinal nematode. - **Habitat**: Small intestines (primarily jejunum). - **Transmission**: Ingestion of eggs from contaminated food, water, or soil. ## Life Cycle - **Development in Soil**: Eggs mature in moist soil over 10–40 days to become infective. - **Larval Migration**: Swallowed eggs hatch in the duodenum -> penetrate mucosa -> portal circulation -> liver -> heart -> lungs. - **Pulmonary Phase**: Larvae molt in lungs, ascend the respiratory tract, and are swallowed back into the intestine to mature into adults. ## Pathogenicity and Clinical Features
Answer: Model answer pending
Answer: - **Intestinal Obstruction**: Due to high worm burden. - **Ectopic Ascariasis**: Migration into bile ducts (biliary obstruction), pancreas (pancreatitis), or liver (abscess). ## Diagnosis - **Stool Microscopy**: Detection of fertilized or unfertilized eggs. - **Larvae Detection**: Found in sputum or gastric washings during the pulmonary phase. - **Imaging**: X-ray, Ultrasound, or ERCP for biliary complications. ## Treatment - **Medications**: Albendazole (400 mg once), Mebendazole (100 mg BID for 3 days), or Pyrantel pamoate (11 mg/kg). - **Pregnancy**: Avoid Albendazole/Mebendazole; Pyrantel pamoate is considered safe. - **Surgery**: Required for complete intestinal or biliary obstruction.