GIT MODULE Intestinal Infections with Parasites Two Lectures

GIT MODULE Intestinal Infections with Parasites (Two Lectures) By Prof. Dr. Zainalabideen A. Al-Abdulla, MRCPI, DTM&H. , Ph. D. , FRCPath. (U. K. )

Learning objectives 1. Understand infection arising from Nematodes: Enterobius, Trichuris, Ascaris, Ancylostoma, Necator, Strongyloides, and Toxocara. 2. Understand infections caused by Cestodes: Taenia, and Hymenolepis nana, as well as: - Trematode: Fasciola 3. Recognize the life cycle, morphology, laboratory diagnosis, epidemiology, immunity, and treatment for each parasite.

Intestinal Nematodes Cylindrical, tapered bodies, and covered with cuticles; infect > 25% of human race: 1. Enterobius vermicularis (pinworm) 2. Trichuris trichiura (whipworm) 3. Ascaris lumbricoides (large roundworm) 4. Necator americanus (hookworm) 5. Ancylostoma duodenale (hookworm) 6. Strongyloides stercolaris

Enterobius vermicularis (Pinworm, Threadworm; Disease: Enterobiasis) Life cycle • Adults (male & female): Inhabit colon/caecum • Female transits anus at night to deposit eggs (sticky/resistant) on perineum; causing itching • Eggs infectious to host and others shortly; Ingested eggs hatch and larvae mature to adults in intestine in 1 month; adults live 2 months.

Manifestations - Nocturnal pruritus ani - Females: Genito-urinary infection Diagnosis - Perianal cellophane tape test (for ova) Treatment - Pyrantel pamoate - Mebendazole • All members of the family; repeat in 2 weeks

Trichuris trichiura (whipworm) - Anterior 2/3 thread-like (whip-like) - Tail: Male coiled; Female straight Life cycle - Attach by anterior end to colonic mucosa - Adults inhabit caecum and release eggs - Eggs mature in soil & become infective in 15 to 30 days (may be shorter). - Ingested eggs, hatch in duodenum, larvae released; mature at small intestine in 1 month; migrate to cecum and ascending colon.

Epidemiology - Associated with defecation on soil and warm, humid climate - Adult worms may live for years usually for 1 year, but may extend to 4 - 8 Y) Pathogenesis & immunity - Local ulceration and hemorrhage (5 µl/worm/ day causing anemia); leading also to bacteremia - CMI and Ig. E-mediated mucosal immunity

Manifestations - Anemia, and “dysentery syndrome” due to colonic damage causing pain and diarrhea - Colonic or rectal prolapse in heavy worm load Diagnosis - Stool examination for eggs (low power lens) - Eosinophilia Treatment - Mebendazole (drug of choice), Albendazole - Cure rate 60 -70%; Prevention: Good sanitation

Ascaris lumbricoides - Short-lived (6 -18 months); most common, - 15 -40 cm in length. Life cycle See the Figure Pathogenesis & Immunity - Partially protective immunity - Pulmonary immediate hypersensitivity to larval migration leading to tissue damage.

Clinical manifestations - Asymptomatic with small worm loads - Respiratory symptoms (larval migration) - Malabsorption and occasional intestinal obstruction with heavy worm load

Diagnosis - Stool examination for eggs - Sputum: Larvae and eosinophils (pulmonary phase) Treatment - Albendazole, Mebendazole, Pyrantel Pamoate - Community mass-therapy; at 6 months intervals can be repeated.

Hookworms (Ancylostoma duodenale and Necator americanus) - Pinkish-white, 10 mm, head curved (hooked) - Species differ by morphology of oral cavity: • A. duodenale: 4 sharp tooth-like • N. americanus: Dorsal/ventral cutting plates Life cycle: See Figure - Eggs: 4 - 8 celled

Epidemiology - Worldwide; Limited to tropical areas mainly - Larvae require hot, moist conditions Pathogenesis and Immunity - Blood loss: Significant (Iron deficiency Anemia) A. duodenale = 0. 2 ml/day N. americanus= 0. 03 ml/day - Adults live 2 -14 Y in the gut - Eosinophilia: Gut and blood - Humoral immunity and immediate hypersensitivity

Manifestations - Asymptomatic mostly - Pruritus and rash at skin penetration - IDA due to intestinal blood loss & complications Diagnosis - Stool examination for eggs Treatment and prevention - Pyrantel pamoate, mebendazole, albendazole - Correct anemia - Sanitation, wearing shoes for prevention

Strongyloides stercoralis - Complex life cycle - 2 mm length (smallest intestinal nematode) - Eggs not important in diagnosis (why? ) - Larvae differ from those of hookworm (how? )

Life cycle 1. Primary cycle resembles hookworm except larvae develop in human gut 2. Filariform stage in gut: Auto-infection 3. Adult develop in soil: Sustained life cycle Epidemiology Similar to hookworm, but less common

Manifestations - Pulmonary and intestinal manifestations can be similar to hookworm and Ascaris infections - External auto-infections causes lesions over buttocks, abdomen, and back - Massive hyper-infection occurs in immunosuppressed patients, but uncommon in AIDS - Strongyloidiasis should be considered before immunosuppression of patients at risk

Diagnosis - Finding rhabditiform larvae in stool or duodenal aspirate - Sputum examination for larvae - Serology (e. g. ELISA) for antibodies may be helpful in subclinical autoinfection

Treatment • Uncomplicated: - Ivermectin: 2 oral doses • Hyper-infection: - Ivermectin: 1 week (extended) 6 m. in immunocompromised • Cure rate: About 100%

Taenia (Cestodes) 1. T. saginata (Beef tapeworm) 2. T. solium (Pork tapeworm) Epidemiology - T saginata: Common in the Middle East - T. solium: Common in the USA/Europe Laboratory diagnosis - Adhesive cellophane tape technique - Stool examination: Detect eggs & proglottids

Tapeworm structures 1. Taenia saginata. 3. Taenia solium. scolices; gravid proglottids; ) ova (indistinguishable between species).

Treatment and Prevention - Praziquantel or Niclosamide: Single dose, oral - Check after 3 months - Sewage disposal, meat inspection, and adequate cooking

Hymenolepis nana - “Dwarf tapeworm”; 4 cm long - Transmitted directly human-to-human - Eggs ingested via fecal-oral route - Embryo released and invade intestinal wall - Re-enter the gut lumen as adult worms - Asymptomatic, or diarrhea, abdominal pain Treatment: As other tape worms

Egg of Hymenolepis nana: Oval with inner membrane of two poles, from which 4 -8 polar filaments spread out between these two membranes.

Fasciola hepatica (sheep liver fluke) - It is a Trematode - Adults survive decades in biliary tract Life cycle: See the Figure Diagnosis: Eggs (Urn-like, knob on the wide pole) in feces and duodenal aspirate Treatment: Praziquantel, and albendazole

Toxocara canis (Dog Round Worm) - Soil contaminated with ova deposited by domestic dogs - Children are often infected - Infection is more common than disease # See Figure for life cycle - “Visceral larva migrans” occurs by migratory larvae in different human tissues.

Visceral larva migrans - Skin rash, enlarged spleen, asthma, pulmonary infiltrate, abdominal pain, sleep & behavioral changes, focal neurological defects, and seizure - Invasion of eyes in older children and adults result in “ocular larva migrans” - Lasts weeks to months & may result in death: • Human dead end host • Larvae migrate to different tissue causing damage and NO adult worm developed

cont. /… Visceral larva migrans” Diagnosis - Tissue biopsy and sero-diagnosis by EIA Treatment and Prevention • Corticosteroid + Albendazole - Disposal of pet feces - Deworming of dogs (every 3 months in first year, then every 6 months) - Avoid geophagia (eating earth or soil)