1. Nematodes, Cestodes, Trematodes Slackers Facts by Mike Ori

2. Disclaimer The information represents my understanding only so errors and omissions are probably rampant. It has not been vetted or reviewed by faculty. The source is our class notes. The document can mostly be used forward and backward. I tried to mark questionable stuff with (?). If you want it to look pretty, steal some crayons and go to town. Finally… If you’re a gunner, buck up and do your own work.

3. Describe a nematode

4. Round spindle shaped worms that range in size from 1mm to 70cm. They undergo multiple larval stages. They are dioecious (separate sexes)

5. What are the three methods of nematode infection

6. 1.Ingestion of eggs 2.Ingestion of larva 3.Direct penetration of skin

7. Describe the relative frequency of nematode disease in children v adults

8. Children > adults

9. What are the intestinal nematoed and what are their common names

10. Enterobius vermicularis – pinworm Trichuris trichura – whipworm Ascaris lumbricoides – roundworm Necator americanus – hookworm Ancylostoma duodenale – hookworm Strongyloides stercoralis – none

11. What is the life cycle of Enterobius vermicularis

12. Ingested eggs hatch in small intestine Adults live in colon Eggs deposits in perianal region nightly by females

13. How is Enterobius vermicularis diagnosed

14. Sticky side out Scotch tape wrapped slide is pressed against perianal region. Tape is examined under microscope to identify the presence of eggs

15. What is the hallmark clinical sx for Enterobius?

16. Perianal pruritis

17. What is the lifecycle of Trichuris trichuria?

18. 1.Ingestion of embryonated eggs from contaminated dirt. 2.Larva hatch in small intestine 3.Adults mature in colon where they burrow into the surface 4.Eggs are passed in the feces 5.Egg embryonate in the soil over 2-4 weeks

19. What are the clinical sx of Trichuris

20. None if worm burden is low. Otherwise tenesmus with chronic mucoid diarrhea occurs. Rectal prolapse may occur

21. Why does rectal prolapse occur with Trichuris?

22. The adult worms burrow into the epithelium and weaken it.

23. Trichuris DX?

24. O and P for O

25. What is the lifecycle for Ascaris lumbricoides?

26. 1.Ingestion of embryonated eggs which hatch in intestines 2.Larva migrate to alveoli 3.L3 larva break through into the alveolar spaces 4.Larva migrate up trachea and are swallowed 5.Adults mature in small intestines 6.Eggs pass in feces 7.Embryonate in soil for 2-4 weeks

27. What is the relative size of ascaris?

28. They can range up to 70cm

29. Correlate the intensity of disease to Ascaris chracteristics

30. Disease intensity is dictated by worm burden. Higher burden results in greater likelihood of clinical sx.

31. Relate eosinophilia to Ascaris infection

32. Elevated when the worms are migrating to and especially when they are molting within the alveoli.

33. How does Ascaris cause disease in the intestines

34. Primarily through blockage

35. Describe Necator americanus lifecycle

36. 1.Eggs hatch in the soil and larvate 2.L3 larva directly penetrate the skin 3.Larva migrate to the lungs and pass through to the alveolar space 4.They are regurgitated and swallowed 5.Adults mature in the small intestines 6.Eggs pass in the feces

37. How dow Necator and Ancylostoma vary in their paths of infection?

38. Ancylostoma infection can also occur by direct ingestion of eggs in a manner akin to Ascaris. Wakana’s disease relates to ancylostoma infection by ingestion

39. Describe the clinical disease

40. Asthma from migration that is less sever than ascaris because molting does not occur. Anemia related adult repositioning every few days in the intestine coupled with anti- coagulant

41. What is the dx for Necator and Acylostoma

42. Direct microscopic observation of eggs passed in feces

43. What is Strongyloides lifecycle

44. 1.L3 larva penetrate skin 2.Larva migrate to lungs and break out of alveoli 3.Larva migrate up trachea and are swallowed 4.Adults mature in the small intestines 5.Eggs ebryonate and hatch in the host 6.L2 larva pass in feces 7.L3 larva reinfect host

45. How does Strongyloides infection differ from that of other intestinal worms?

46. Strongyloides eggs hatch within the host resulting in the potential for autoinfection.

47. Describe Strongyloides disease

48. 1.Pneomonitis 2.Moderate to severe watery, moucousy diarrhea 3.10-40% eosinophilia

49. Strongyloides

50. What dictates the level of eosinphilia between Ascaris, Necator, Ancylostoma, and Strongyloides

51. Ascaris has the highest reactivity because it molts L1-L2 and L2-L3 within the tissues. Thus eosinophilia is highest in ascaris.

52. Trichenella spiralis lifecycle

53. 1.Ingestion of encysted organisms in undercooked, non-frozen pork, bear meat, and rat. 2.Adults mature in the intestines. 3.Larva migrate to the skeletal muscles and encyst for up to 30 years.

54. What are the phases of Trichenellosis

55. Intestinal phase – non-specific gastroenteritis lasting 2-3 weeks Parental phase – myalgia, eosinophilia (20-90%)

56. What is cutaneous larva migrans

57. Ca and dog hookworm larva penetrate the skin but cannot enter the circulation. They persist for about 10 days before dying

58. What is visceral larval migrans

59. Toxacara canis and ascaris of dogs cannot break out of alveoli. Organism disseminates and encysts primarily in liver and eye.

60. What is filiariasis?

61. Infection with tissue nematodes transmitted by arthropods.

62. What are the agents of Filariasis?

63. Wuchereria bancrofti Brugia malayi Onchocerca volvulus Loa Acanthocheilonema perstans

64. How do the insect biting pattern and the worm levels in the blood compare in filariasis?

65. Worm levels increase in a way such that their levels coincide with the activity of their insect vectors. The mechanism is not understood.

66. Describe the role of antibiotics in the treatment of filariasis

67. Many filariasis agents have an endosybiont bacteria without whom they cannot live. Therapy directed against the bacteria can be beneficial

68. What are the vectors for filariasis

69. Mosquitoes – most organism Blood sucking flies – Onchocerca

70. What are the agents of elephantiasis?

71. Wucheria bancrofti and Brugia malayi

72. What is Loa Loa

73. A filariasis that migrates through the subcutaneous tissue of the eye.

74. What is the life cycle of Onchocercosis

75. 1.Blood sucking flies deposit larva in skin 2.Nodules form filled with organisms 3.Black flies ingest larva from nodule

76. Describe the role of the immune system in causing Onchocerca disease

77. The immune system largely ignores adults but reacts vigorously against the endosymbiotic bacteria (Wolbachia) contained within. It is believed the the immune response leads to disease.

78. What are tremetodes

79. Flukes of nature

80. List the tremetodes

81. Clonorchis sinensis – Chinese river fluke Fasciola hepatica – Sheep liver fluke Pargonimus westermani – Human lung fluke Schistosomes – blood flukes

82. Where do adult schistosomes live?

83. Depends on species. Mansoni, japonicum, mekongi live in mesenteric venules Maematobium in the venus plexus of the urinary bladder

84. Where do schistosomes lay their eggs and what happens to the eggs

85. Eggs are laid on the venous endothelium. They pass through the epithelium to be passed in urine or feces depending on speces

86. Describe the lifecycle of schistosomes

87. 1.Eggs hatch in fresh water to form miracidia 2.Miracidia pentrate snails and mature to cercariae 3.Cercariae leave snail and penetrate host. 4.Migrate to lungs and liver and mature to adults 5.Adults mate and migrate to venous plexus of mesentery or urinary tract. 6.Eggs are deposited into epithelium where they burrow through to the epithelium to pass

88. What is the origin of granulomatous disease in schistosomiasis

89. Eggs float to the liver instead of passing into the epithelium. In the liver they elicit a strong immune response that results in granuloma formation.

90. What are the time course of the diseases caused by schistosomiasis

91. Swimmers itch lasting a 2 days Katayama fever beginning 2-3 weeks after exposure Chronic schistosomiasis beginning 2+ years

92. What are cestodes

93. Tapeworms

94. List the cestodes

95. Taenia saginata – beef tapeworm Taenia solium – pork tape worm Diphyllobothrium latum – fish tape worm Echinococcus granulosus – dog tape worm

96. Describe the lifecycle of Taenia solium

97. 1. Ingested eggs hatch in cattle 2. Larva hatch in small intestines 3. Larva penetrate intestinal epithelium 4. Larva migrate to the skeletal muscle to encyst and develop to cystecerci 5. Encysted meat is improperly cooked and ingested. 6. Unencyst and develop into adults 7. Proglottids containing eggs break up and eggs pass in feces

98. Describe the clinical disease caused by the adult tapeworm

99. Usually only one worm present so there is no clinical disease. PT may notice proglottids in stool.

100. What is a proglottid

101. It is a segment of the worm that contains the eggs. It developed from a hermaphroditic segment that contained uterine and testes elements.

102. What is cystecercosis

103. Cystecercosis occurs when a human ingest the eggs of T. solium and thus becomes the intermediate host.

104. What are the clinical sx of cystecercosis

105. It depends on the worm burden. May form space occupying lesions in any organ system. Epilepsy can occur in if cystecerci form in the brain.

106. What is the difference between saginata and solium proglottids?

107. T. Saginata has 12+ lateral branches of the uterus vs 5-10 for T. solium

108. Does T. saginata cause cystecercosis?

109. No

110. What is interesting about the lifecycle of Diphyllobothrium latum?

111. It is very complicated and involves multiple fresh water hosts including crustaceans and fish.

112. What are the clinical sx of D. latum?

113. Usually none. Can have B12 deficiency.

114. What is the lifecycle of Echinococcus granulosus?

115. Sheen act as intermediate host. Dogs eat sheep muscle encysted with the organism. Adults develop.

116. How do humans enter the Echinococcus granulosus loop

117. Humans enter the loop by ingesting material contaminated with eggs.

118. What are the sx of Echinococcus granulosus

119. Large ( 20cm) fluid filled hydatid cysts form in the liver or viscera.

120. Describe the disease caused by Echinococcus granulosus

121. Usually these are mass forming issues due to the large size. The Echinococcus is unique in that it can replicate in the cyst form thus over time a number of cysts can form.

122. Describe the consequence of hydatid cyst rupture.

123. The fluid is allergenic and can cause anaphylaxis on rupture. Surgical tx must be done gingerly to prevent shock.