Summary

This document provides information about nematodes, focusing on classification, morphology, life cycles, and clinical presentations of different nematode species. The study includes intestinal and tissue nematodes. The intended audience seems to be students in undergraduate biology courses or medical students interested in parasitology.

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Nematodes II Classification I. Intestinal Nematodes: 1. Ascaris lumbricoides 2. Ancylostoma duodenale 3. Strongyloides stercoralis 4. Trichinella spiralis 5. Enterobius vermicularis 6. Tricocephalus trichiuris II...

Nematodes II Classification I. Intestinal Nematodes: 1. Ascaris lumbricoides 2. Ancylostoma duodenale 3. Strongyloides stercoralis 4. Trichinella spiralis 5. Enterobius vermicularis 6. Tricocephalus trichiuris II. Tissue Nematodes: 1. Wuchereria bancrofti Trichinella spiralis (Pork threadworm) Disease: trichinellosis or trichinosis (zoonotic disease) Epidemiology: Europe and USA Habitat: Adult worms inhabit small intestine. Encysted larvae live in striated muscle of the same host. Definitive and Intermediate Host: pigs, rats, man (accidental) ❖Adult worms and encysted larvae develop within a single vertebrate host, and an infected animal serves as a definitive host and potential intermediate host. ❖A second host is required to perpetuate the life cycle of Trichinella. ❖The domestic cycle most often involved pigs and anthropophilic rodents, but other domestic animals such as horses can be involved. ❖In the sylvatic cycle, animals most often associated as sources of human infection are bear, moose and wild boar. MOI: Trichinellosis is caused by the ingestion of undercooked meat containing encysted larvae 1. After exposure to gastric acid and pepsin, the larvae are released from the cysts 2. and invade the small bowel mucosa where they develop into adult worms 3. The life span in the small bowel is about four weeks. After 1 week, the females release larvae 4. that migrate to striated muscles where they encyst Morphology: Small Females are 2.2 mm in length; males 1.2 mm. Cellular esophagus Clinical Picture: 1. Intestinal Phase Diarrhea, nausea, vomiting 2. Muscle Invasion Phase Fever, facial edema, myalgia, eosinophilia. 3. Encapsulation Phase Fever and muscle weakness subside. Cysts calcify. The clinical disease is self-limited and usually lasts 2 to 3 weeks in light and 2 to 3 months in heavy infections. In severe cases, death due to heart/respiratory failure. Diagnosis: 1. Clinical manifestations 2. Laboratory diagnosis a) Muscle biopsy: identification of Trichinella larvae in biopsy muscle tissue b) Blood picture c) Antibody or Ag detection - Shape: ellipsoidal - Size: 0.5 mm - Color: white - Content: coiled larva - Place: near tendinous attachment Treatment: 1. Thiabendazole 2. Corticosteroids (in severe cases) - Prevention ?? Enterobius vermicularis (Pinworm) Disease: Enterobiasis Habitat: Large intestine Definitive Host (DH): Man Epidemiology: worldwide, 1 billion infected especially children Morphology 1-Small worms, 2. whitish in colour with a double bulbed Curved end, single oesophagus. copulatory spicule 3-Male worm is 5mm long. The posterior end is spirally curved ventrally and carries a single spicule. -Female worm is 10 mm long with posterior 1/3 tapering into pointed tail. Life cycle: ❖ After fertilization, male dies and female migrates towards the anal opening, depositing its eggs on the perianal region (diagnostic stage) especially at night. ❖ This causes irritation and itching and so, eggs are lodged on fingers and under the nails and become infective within few hours. ❖ Man gets infected by ingestion of larvated eggs (infective stage) on contaminated fingers either by autoinfection or through contaminated objects and with contaminated food or drinks. ❖ Ingested eggs hatch in the small intestine and liberated larvae become adults in the large intestine. Retrofection = retroinfection ❖ Infection may also occur by retrofection where hatching of eggs occur in the perianal region and larvae migrate back to the large intestine through the anus. Clinical Picture: 1. Pruritus ani Irritation and pruritus ani, especially at night, due to presence of the gravid females and eggs in the perianal region. Scratching may cause dermatitis and secondary bacterial infection. 2- Nervous irritability, restlessness and insomnia due to pruritus ani. 3-Abdominal pain may occur as adult worms may cause catarrhal inflammation of intestinal mucosa. 3-Worms present in appendix may cause appendicitis. 4-In female patients the worms may reach: a -The urethra and bladder causing urethritis, cystitis and nocturnal enuresis. b-The vagina causing vaginitis Diagnosis: 1. Clinical manifestations 2. Laboratory diagnosis a) Detection of the adult worm b) Recovery of the egg i. From perianal area ii. From stool (5%) NIH swab (National Institute of Health swab) : The perianal area is swabbed using a cellophane paper folded and tied to the tip of a glass rod and inserted in a test tube. The cellophane tape is then stretched on a slide and examined microscopically for eggs. Graham’s swab(adhesive Scotch tape): The tape is folded over a tongue depressor or glass slide with the sticky side outwards and pressed against perianal area, then spread on a glass slide. Size: 50 X 25 µ Shape: D-shaped Shell: Thick double walled Color: Transparent Content: may be unembryonated, mature, or immature. Treatment: 1. Mebendazole 100 mg single dose then repeated after 2 weeks. 2. Topical Ivermectin to skin of the perineum. 3. Group/family treatment. 4. Bedding cleaned every 3 days and underwear and pajamas washed daily for three weeks. Prevention: Treatment of patients and their families health awareness Improve sanitation (washing hands and avoid contaminated food) Trichocephalus trichiuris (Trichuris trichiura) (Human Whipworm) Disease: Trichuriasis Habitat: Human large intestine 1. Whip like worm with an anterior narrow part (3/5 of the worm) containing the cellular oesophagus and a posterior broad part (2/5 of the worm) containing rest of the organs. The male is about 4.5 cm long.Posterior end is curved ventrally and has a single long spicule within a spiny retractile sheath. The female is about 5 cm long. Posterior end is digitiform. It has a single genital system. Vulva is at the junction of narrow and broad parts. ❖ The unembryonated eggs are passed with the stool. ❖ In the soil, the eggs develop into a 2-cell stage , an advanced cleavage stage , and then they embryonate ; eggs become infective in 15 to 30 days. ❖ After ingestion (soil-contaminated hands or food), the eggs hatch in the small intestine, and release larvae that mature and establish themselves as adults in the colon. ❖ The adult worms (approximately 4 cm in length) live in the cecum and ascending colon. ❖ The adult worms are fixed in that location, with the anterior portions threaded into the mucosa. ❖ The females begin to oviposit 60 to 70 days after infection. ❖ Female worms in the cecum shed between 3,000 and 20,000 eggs per day. ❖ The life span of the adults is about 1 year. Clinical Picture: 1. Light infection Asymptomatic 2. Intermediate Infection Lower abdominal pain, bloody diarrhea Dysentry = blood, mucous, pus 3. Heavy Infection > 800 worm Chronic dysentery, malabsorption, anemia 4. Rectal Prolapse : part of the large intestine's lowest section (rectum) slips outside the muscular opening at the end of the digestive tract (anus). Diagnosis: 1. Stool Examination Egg > 10/smear 2. Blood picture 3. Proctoscopy - Shape: Barrel with 2 mucoid plugs (bulbs) - Size: 50 X 25 µm - Shell: thick - Color: brown - Content: unsegmented larva Treatment: 1. Albendazole 2. Mebendazole Prevention: 1. Avoid ingesting soil that may be contaminated with human feces 2. Wash your hands with soap and warm water before handling food. 3. Wash, peel, or cook all raw vegetables and fruits before eating, particularly those that have been grown in soil that has been fertilized with manure. Tissue Nematodes Wuchereria bancrofti Disease: Filariasis, may lead to Elephantiasis in later stages. Epidemiology: In Tropics, In Egypt, Nile delta. Definitive Host: Adults inhabit human lymphatic tissues of lower limbs & external genitalia. Intermediate Host: Female Culex Mosquito. Clinical Picture: 1. Acute inflammatory Stage Lymphadenitis Lymphangitis Fever 2. Chronic Obstructive Stage Rupture of lymphatics Elephantiasis Diagnosis: 1. Clinical manifestations 2. Laboratory diagnosis a) Wet mount: Detection of microfilaria in Shape: Thread like, anterior blood 10 pm-4 am end blunt, posterior pointed Size: 250-300 X 7-10 μm b) Serology: detection of Ag or Ab Shell: Redundant Color: white Content: nuclei arranged in rows. Both ends are devoid of nuclei. Treatment: 1. Diethylcarbamazine (DEC) 2. Antihistaminics 3. Surgical removal of elephantoid tissue

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