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NEMATODES Faculty: SAMUEL AGUAZIM, M.D. Lange Chapter 56

NEMATODES Faculty: SAMUEL AGUAZIM, M.D. Lange Chapter 56. case. 4 year old female with constant scratching of her buttocks for 1 week. The mother says that the child has been very irritable, uncomfortable at night.

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NEMATODES Faculty: SAMUEL AGUAZIM, M.D. Lange Chapter 56

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  1. NEMATODES Faculty: SAMUEL AGUAZIM, M.D. • Lange Chapter 56

  2. case • 4 year old female with constant scratching of her buttocks for 1 week. The mother says that the child has been very irritable, uncomfortable at night. • On examination of her anal area: numerous scratch marks, erythematous and swollen.

  3. Pyrantel pamoate 2 doses • Recovered • Impression: Pinworm infection, secondary to Enterobius vermicularis

  4. Nematodes • are roundworms with a cylindrical body and complete digestive tract, including a mouth and an anus. • The body is covered with a noncellular, highly resistant coating called a cuticle. • Nematodes have separate sexes; thefemale is usually larger than the male

  5. Nematodes The medical important nematodes can be divided into two categories according to their primary location in the body to: IntestinalNematodes TissueNematodes

  6. Intestinal Nematodes Enterobius vermicularis most common helminthic infection in the United States Disease:Pinworm infection. Characteristics:Intestinal nematode.

  7. Enterobius vermicularis Life cycle: • confined to humans. • The infection is acquired byingesting the worm eggs. • The eggs hatch in thesmall intestine, where the larvae differentiate into adults and migrateto thecolon. • The adult male and female worms live in the colon, where mating occurs. • At night, females migrate from the anus and lay many thousands of fertilized eggs onperianal skinand in environment. • Embryo within egg becomes an infective larva within 4—6 hours. • Reinfection can occur if they are carried to themouth by fingersafter scratching the itching skin.

  8. Life cycle of Enterobius

  9. Enterobius vermicularis adult male and female 

  10. Enterobius egg(flattened side with larvae inside)

  11. MOT: ingestion of eggs Females lay eggs in the perianal area at night

  12. Enterobius vermicularis Transmission:Transmitted by ingesting eggs. Humans are the only hosts. Occurs worldwide. Pathogenesis:Worms and eggs causeperianal itching.Scratching predisposed to Secondary bacterial infection Laboratory Diagnosis:Eggs visible by “Scotch tape” technique. Eggs are not found in stool . Adult worms found in stool or near anus. Treatment:Mebendazole

  13. Memory Tool • On the bus (Enterobius), you sit on a pin (pinworm), and get an itchy bottom and use scotch tape to make it feel better.

  14. Trichuris trichiura Disease:Whipworminfection Characteristics:Intestinal nematode. The characteristic of“whiplike”apperance of the adult worm. Life cycle: • Humans ingesteggs,which develop into adults in gut. • Eggs are passedin feces into soil, where they embryonate, ie, become infectious.

  15. The characteristic of “whiplike” apperance of the adult worm.

  16. Trichuris trichiura Transmission: • More than 500 million infected. • Transmitted byfood or watercontaminated with soil containing eggs. • Humans are the only hosts. Occurs worldwide, especially in the tropics. Pathogenesis: • Worm in gut usually causeslittle damage. • The whipworm infects about 2 million children in the U.S. • Causesrectal pruritis and tenesmus, which often results inrectal prolapse.

  17. Infectious DiseasesWhipworm – Rectal Prolapse

  18. Infectious DiseasesWhipworm – Rectal Prolapse

  19. Trichuris trichiura Laboratory Diagnosis: • Eggs visible in feces. • The egg isbarrel-shape with a plug at each end, in the stool. Treatment:Mebendazole. Prevention:Proper disposal of human waste

  20. Trichuris trichiura eggs, a typical barrel shape two polar plugs, that are unstained 

  21. Trichuris trichiura • Tricksy (Trichuris) carries a whip and ate eggs which gave her rectal prolapse. Poor Tricksy!!!

  22. Ascaris Disease:Ascariasis. Characteristics:Intestinal nematode. Life cycle: • Humans ingest eggs, which form larvae in gut. • Larvae migrate through the blood to thelungs, where they enter the alveoli, pass up the trachea, and areswallowed. • In the gut, they become adults and lay eggs that are passed in the feces. • They embryonate, ie, become infective in soil. • The adult worms are the largest intestinal nematodes (25 cm or more).

  23. Ascaris Life Cycle 

  24. Ascaris adult male and female

  25. Erratic ascariasis

  26. Ascaris Transmission:food contaminated with soil containing eggs. Humans are the only hosts.Endemic in the tropics. Pathogenesis:Larvae in lung cancause pneumonia.Heavy worm burden can cause intestinal obstruction or malnutrition. Laboratory Diagnosis:Eggs visible in feces.Eggs are oval with irregular surface. Eosinophilia occurs. Treatment:Mebendazole Prevention:Proper disposal of human waste

  27. Eggs are oval with irregular surface

  28. Billy (biliary obstruction) drives his car (Ascaris) while eatingeggs and gets short of breath. Poor Billy!!! Add intestinal obstruction

  29. Strongyloides Disease:Strongyloidiasis Characteristics:Intestinal nematode. Life cycle: • Larvae penetrate skin, enter the blood, and migrate to thelungs. They move into alveoli and up the trachea and areswallowed. • become adults and enter the mucosa, where females produce eggs that hatch in the colon into noninfectious,rhabditiform larvaethat areusuallypassed in feces. • NOTE:the only helminth to secrete larvae (and not eggs) in feces

  30. Strongyloides • Occasionally, rhabditiform larvae molt in the gut to forminfectious, filariform larvaethat can enter the blood and migrate to thelung (autoinfection). • The noninfectious larvae passed in feces form infectious filariform larvae in the soil. • These larvae can either penetrate the skinor form adults. • Adults in soil can undergo several entire life cycles there. • This free-living cycle can be interrupted when filariform larvae contact the skin.

  31. Strongyloides Transmission:Filariform larvae in soil penetrate skin. Endemic in the tropics. Pathogenesis: • Little effect in immunocompetent persons. • In immunocompromised persons, massive superinfection can occur accompanied by secondary bacterial infections. Laboratory Diagnosis: Larvae visible in stool. Eosinophilia occurs. Treatment:Thiabendazole. Prevention:Proper disposal of human waste. Use of footwear

  32. Memory Tool • The strongman (Strongyloides) is brought down by a larvae penetrating his skin causing pulmonary distress and superinfection. Poor strongman!

  33. Ancylostoma duodenaleNecator Americanus Disease:Hookworm. Characteristics:Intestinal nematode.

  34. Ancylostomaduodenale • Filariform larvae in soil penetrateskin of feet, enter the blood, and migrate to thelungs. • enter alveoli, pass up the trachea, then areswallowed. • become adults in small intestine and attach to walls viateeth (Ancylostoma)or cutting plates (Necator). • Eggsare passed in feces and form noninfectious rhabditiform larvae and then infectious filariform larvae.

  35. Ancylostoma duodenale adult male and female 

  36. Ancylostoma duodenale Transmission:Filariform larvae in soilpenetrate skin of feet. Humans are the only hosts. Pathogenesis:Anemia due to blood loss from gastrointestinal tract. Laboratory Diagnosis: Eggs visible in feces.Eosinophilia occurs. Treatment:Mebendazole AND Iron therapy Prevention:Use of footwear. Proper disposal of human waste.

  37. ANCYLOSTOMA BRAZILIENSEANCYLOSTOMA CANINUM • DOG and CAT Hook worm • Forms/ Transmission. • Filariform larvae penetrate intact skin but cannot mature in humans • Disease/organ most affected • Cutaneous larvae migrans: intense itching • Tunnels through tissue • Diagnosis: clinical signs • Treatment- ivermectin

  38. Ancylostoma braziliensis(cutaneous larva migrans/creeping eruption) Pathognomonic: serpiginous tunnels Lacks hydrolytic enzymes to penetrate into the dermis; remains localized in the epidermis

  39. Ancylostoma braziliensis(cutaneous larva migrans/creeping eruption) Dog, cat hookworm Gulf states, South US freezing with liquid nitrogen/ethyl chloride; Mebendazole

  40. Trichinella Disease:Trichinosis. Characteristics:Intestinal nematode that encysts in tissue.

  41. Trichinella Life cycle: • Humans ingestunder cooked pork and other meatcontaining encysted larvae, which mature into adults in small intestine. • Female worms release larvae that enter blood and migrate toskeletal muscle or brain, where theyencyst. • Pigs:most important reservoirs of human disease in USA, except Alaska where bears are the ones.Reservoir hosts are primarily pigs and rats. • Humans are dead end hosts. • Occurs worldwide but endemic in eastern Europe and west Africa

  42. Trichinella life cycle

  43. Encysted larvae of Trichinella in pressed muscle tissue. The coiled larvae can be seen inside the cysts.CDC

  44. Trichinella Pathogenesis:Inflammation ofmuscle Laboratory Diagnosis: • Encysted larvae visible in muscle biopsy • Eosinophilia • Serologic tests positive. Treatment:Thiabendazole effective early against adults. None for established disease Prevention:Adequate cooking of pork  

  45. Memory Tool • A tricky (Trichinella) pig caused cysts in his owners muscles.

  46. Tissue nematodeDracunculus Disease:Dracunculiasis. Characteristics:Tissue nematode.

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