Introduction - Worldwide distribution , common in children and institutionalized individuals. - Most common helminthic infection globally. - Reservoir : Humans
Introduction - Worldwide distribution , common in children and institutionalized individuals. - 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 - Eggs in Perianal Region Gravid female migrates to perianal skin at night to lay sticky eggs . - Eggs cause intense itching (pruritus ani) . - Scratching transfers eggs to fingers, nails, clothing, beddings . - Egg Ingestion & Hatching Eggs are ingested from contaminated surfaces (hands, beddings, clothing, food). - Hatch into larvae in the intestine (ileum). - Larval Development & Maturation Larvae migrate to caecum and colon , where they mature into adults . - Maturation takes 2 weeks to 2 months . - Male worms die after mating and are passed in stool . - Female worms migrate at night to lay 5,000–15,000 eggs on perianal skin . - Reinfection & Autoinfection Autoinfection occurs when eggs are transferred from hands to mouth . - Retroinfection occurs when eggs hatch on perianal skin and larvae migrate back into the colon . Eggs become infective within 6 hours and remain viable for weeks in the environment. Pathogenesis & Clinical Features 1. Perianal & Perineal Symptoms - Pruritus ani (Itching at night) due to female migration. - Scratching → Skin irritation & bacterial superinfection . 2. Sleep Disturbances - Nocturnal restlessness & irritability due to crawling sensation . 3. Genitourinary Involvement (in females) - Vulvovaginitis , mucoid vaginal discharge . - May reach the uterus, fallopian tubes, and peritoneum causing: Chronic salpingitis . - Cervicitis & recurrent UTIs . 4. Appendicitis & Gastrointestinal Symptoms - Worms found in the appendix during appendectomy. - Abdominal pain, nausea, mild diarrhea in heavy infections. Diagnosis 1. Demonstration of Eggs - Fecal examination is NOT reliable (eggs are laid perianally, not in stool). - Best method: Collection of perianal eggs using adhesive tape or swabs. a) NIH Swab Method - Glass rod with transparent cellophane swabs the perianal area. - Swab is placed on a slide and examined microscopically. b) Scotch Tape Method (Preferred method) - Transparent adhesive tape pressed on the perianal skin early morning. - Transferred onto a glass slide with a drop of toluene. - Microscopy shows oval, flat-sided eggs with a larva inside . 2. Demonstration of Adult Worms - Adult worms visible on stool surface . - Can be seen crawling out of the anus at night. - May be found in appendix during appendectomy. Treatment First-Line Drugs (Single-dose therapy) - Albendazole → 400 mg once , repeat after 2 weeks . - Mebendazole → 100 mg once , repeat after 2 weeks . - Pyrantel pamoate (Safe in pregnancy) → 11 mg/kg (max 1 g) once . Alternative Treatment - Piperazine citrate → Daily for 7 days . Important Considerations All family members should be treated simultaneously to prevent reinfection. Second dose after 2 weeks ensures elimination of newly hatched larvae. Prevention & Control Personal Hygiene - Frequent hand washing . - Short, clean nails to prevent egg accumulation. - Avoid nail-biting & thumb-sucking . Environmental Sanitation - Frequent washing of nightclothes, bed linen, and underwear . - Daily bathing & changing underclothes . - Keep toilets & bathrooms clean . Mass Drug Administration (MDA) - Regular deworming of school-aged children in endemic areas. Critical Notes & Additional Points Pinworms do not cause significant anemia (unlike hookworms). Eggs can survive in dust, furniture, and clothes for weeks , leading to reinfection. Retroinfection (hatching on perianal skin & migrating back) is unique to pinworms. Enterobiasis is the most common helminthic infection in developed countries due to indoor transmission . Pinworm infection does not require soil contact , unlike hookworms and Ascaris. High recurrence rates due to autoinfection , so treatment should include all household members . Can cause chronic appendicitis, recurrent UTIs, and gynecological complications in females. Eggs are light and can become airborne , making transmission possible via dust inhalation. Pinworm (Enterobius vermicularis) Introduction - Enterobius vermicularis (pinworm) is the most common parasitic infection worldwide, especially among children. - Adult worms inhabit the cecum, appendix, and adjacent portions of the ascending colon. Life Cycle - Host: Humans (monoxenous, meaning it completes its entire life cycle in one host). - Infective form: Embryonated eggs containing larvae. - Mode of transmission: Ingestion of embryonated eggs via contaminated fingers, fomites, or food. - Autoinfection by scratching the perianal area and transferring eggs to the mouth. - Retroinfection occurs when eggs hatch on the perianal skin, and larvae migrate back into the colon. - Development in the human body: Eggs are ingested and hatch in the intestine. - Larvae migrate to the cecum and mature into adult worms. - After mating, males die, while gravid females migrate to the perianal region at night to lay eggs. - Eggs become infective within a few hours and are spread via contact with contaminated objects. Pathogenicity and Clinical Features - Common in children and more prevalent in females. - Symptoms: Perianal and perineal pruritus (itching), particularly at night. - Sleep disturbances due to itching. - Female worms may migrate to the vulva and vagina, causing vaginal irritation and mucoid discharge. - Chronic infections may lead to appendicitis, recurrent urinary tract infections, or peritonitis. Diagnosis - Demonstration of Eggs Eggs are rarely found in feces but can be collected from the perianal skin using: NIH swab method: A transparent cellophane swab is rolled over the perianal area and examined under a microscope. - Scotch tape method: Adhesive tape is pressed against the perianal skin and transferred to a slide for microscopic examination. - Eggs may also be found under fingernails. - Demonstration of Adult Worms Adult worms may be seen in stools or crawling out of the anus, especially at night. Treatment - First-line drugs: Pyrantel pamoate (11 mg/kg once, max 1 g). - Albendazole (400 mg once). - Mebendazole (100 mg once). - Alternative: Piperazine (daily for 1 week). - Repeated treatment after 2 weeks is necessary to eliminate reinfection. - Family-wide treatment is recommended due to the high risk of transmission. Prevention and Control - Maintain strict personal hygiene (frequent handwashing, short fingernails, regular bathing). - Wash bedding and nightwear frequently to remove eggs. - Avoid scratching the perianal area to prevent autoinfection. - Deworming of infected individuals and household members. --- Roundworm (Ascaris lumbricoides) Introduction - Ascaris lumbricoides is the largest human intestinal nematode and one of the most common helminths globally. - Highly prevalent in areas with poor sanitation (up to 80–100% in some rural populations). - Habitat: Small intestines (85% in jejunum, 15% in ileum). Life Cycle - Host: Humans (monoxenous). - Infective form: Embryonated eggs containing rhabditiform larvae. - Mode of transmission: Ingestion of contaminated food, water, or soil. - Poor sanitation (e.g., use of human feces as fertilizer). - Airborne transmission (eggs in dust). Development in Soil - Eggs passed in feces are not immediately infective . - They mature in moist, warm, shaded soil (20–30°C) over 10–40 days , developing into infective larvae. - Eggs are highly resistant and can survive in soil for several years. Development in Humans - Swallowed eggs hatch in the duodenum, releasing larvae. -