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Author(s): Vernon Carruthers, Ph.D., Cary Engleberg, M.D., D.T.M.&H., 2009 License: Unless otherwise noted, this material is made available under the terms.

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Presentation on theme: "Author(s): Vernon Carruthers, Ph.D., Cary Engleberg, M.D., D.T.M.&H., 2009 License: Unless otherwise noted, this material is made available under the terms."— Presentation transcript:

1 Author(s): Vernon Carruthers, Ph.D., Cary Engleberg, M.D., D.T.M.&H., 2009 License: Unless otherwise noted, this material is made available under the terms of the Creative Commons Attribution 3.0 License: We have reviewed this material in accordance with U.S. Copyright Law and have tried to maximize your ability to use, share, and adapt it. The citation key on the following slide provides information about how you may share and adapt this material. Copyright holders of content included in this material should contact with any questions, corrections, or clarification regarding the use of content. For more information about how to cite these materials visit Any medical information in this material is intended to inform and educate and is not a tool for self-diagnosis or a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional. Please speak to your physician if you have questions about your medical condition. Viewer discretion is advised: Some medical content is graphic and may not be suitable for all viewers.

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3 Helmintic Infections M1 Infectious Diseases Sequence Vernon Carruthers Cary Engleberg Spring 2009

4 Infection vs. disease successful parasites live in, but do not kill their hosts protozoa multiply within hosts expression of disease depends on host factors helminths do not multiply within hosts severity of disease depends on parasite burden and immunologic response to parasites 3

5 Helminth forms Egg Cyst Larva Adults 4 C. Engleberg/V. Carruthers

6 Helminth modes of entry Ingestion (eggs or cysts) Arthropod bites (larvae) Penetration of intact skin or mucous membranes (larvae) 5

7 Spread and tropisms Some parasites must migrate to certain locations within the host in order to complete their life cycle Non-human parasites, in humans, often fail to migrate properly and become “dead-end infections” 6

8 7 Cary Engleberg

9 Mechanisms for evading the host response antigenic variation - trypanosomes, malaria, giardia intracellular infection - malaria, toxoplasma encystation* - Toxoplasma, cestodes camouflage - schistosomes cleavage of ABs or C’ components - amoebae, leishmania suppression/redirection of the cellular immune response - malaria, leishmania, schistosomes * “cyst” has multiple meanings 8

10 Tissue damage and host response direct destruction of tissue hypersensitivity reactions eosinophila – occurs with helminths, not protozoa – results from tissue migration 9

11 Classification of helminths Nematodes (roundworms) Platyhelminthes (flatworms) Trematodes (“flukes”) Cestodes (“tapeworms”) 10 C. Engleberg/V. Carruthers

12 Helmintic diseases Intestinal – Others – Strongyloides Invasive – Trichinosis – Filaria – Schistosomiasis – Cysticercosis – Echinococcus (autoinfection cycle) (muscle pain, uncooked carnivores) (worms in lymphatics or under skin) (liver or urinary tract granulomas and fibrosis) (cysts in brain, seizures) (massive cysts in liver or lung) roundworms flukes tapeworms 11

13 Intestinal nematodes Larvae pass through lungs Larvae penetrate through intact skin strongyloides hookworm Eggs ingested Trichiuris (whipworm) Enterobius (pinworm) Larvae enter bloodstream ascaris Adult worms in the the intestine Eggs Larvae hatch from eggs 12 C. Engleberg/V. Carruthers

14 Strongyloides life cycle Adult worms in the the intestine Eggs 1st stage larvae hatch from eggs Larvae penetrate through intact skin Larvae enter bloodstream Larvae pass through lungs Larvae molt twice to form filariform larvae (infectious) Autoinfection 13 C. Engleberg/V. Carruthers

15 14 Source Undetermined

16 Strongyloides - clinical features uncomplicated – GI upset autoinfection hyperinfection – rash – bronchspasm, chest X-ray infiltrates – diarrhea – profound eosinophilia – recurrent Gram-negative bacteremia 15

17 Trichinosis 16

18 Trichinella spiralis - life cycle “cycle of carnivorism” among hogs and rats humans ingest encysted larvae in infected, undercooked pork larvae exist in stomach and burrow into small intestinal mucosa adult males and female reemerge and produce larvae which penetrate intestine and circulate in bloodstream larvae enter skeletal muscle cells and encyst 17

19 18 Source Undetermined

20 Trichinosis cases, by source of infection, U.S.,1981 Pork products sausage93 other44 unspecified 9 Non-pork products hamburger18 bear10 other wild animals 7 Unknown 7 188 19

21 Clinical features of trichinosis Most common sxs: – muscle pain and tenderness – fever +/- chills – edema (often periorbital) >10% eosinophilia (often ~50%) elevated creatine phosphokinase (CPK) +/- chronic neurologic/myocardial sxs self-limited (2% mortality) 20

22 Treatment of trichinosis antihelmintic (albendazole) to kill any intestinal adults steroids to relieve inflammatory reactions antipyretics 21

23 Filaria 22

24 Life cycles of two types of filaria Arthropod vector Adult worm pairs Larvae (microfilariae) Lymph- mosquitoes peripheral circulate dwelling lymphatics in bloodstream (e.g, Wuchereria bancroftii ) Skin- biting flies skin nodules migrate through dwelling or migratory dermis 23

25 Microfiliaria found in the blood of lymph dwelling species 24 Armed Forces Institute of Pathology

26 Long-term consequences of persistent lymph- dwelling filarial infection: Blockage of lymph drainage with chronic lymphedema (elephantiasis) 25 Source Undetermined

27 26 Source Undetermined

28 Life cycles of two types of filaria Arthropod vector Adult worm pairs Larvae (microfilariae) Skin- biting flies skin nodules migrate through dwelling or migratory dermis (e.g., Onchocerca volvulus & Loa loa ) Lymph- mosquitoes peripheral circulate dwelling lymphatics in bloodstream (e.g, Wuchereria bancroftii ) 27

29 Black fly: vector of Onchocerciasis 28 Source Undetermined

30 Snip site O. volvulus microfilaria (a skin- dwelling species) in skin snip Depigmentation due to chronic microfilarial production, degradation, and allergic host responses in the skin 29 Cary Engleberg Source Undetermined

31 30 Cary Engleberg

32 O. volvulus skin nodule removed and sectioned, showing cross-sections of male and female adult worms (source of microfiliariae) 31 Source Undetermined

33 Onchocerciasis (”River blindness”) 32 Source Undetermined

34 Role of endosymbiont Wohlbachia sp. in filiaria infection Rickettsia-like organisms required for fecundity and viability of filaria Wohlbachia-free worms produce less inflammation in tissue (? LPS) Implications for rx: – ivermectin kills microfilaria only – tetracycline may destroy adult worms 33

35 Schistosomiasis 34

36 Geographic distribution of schistosomiasis S. mansoni S. hematobium S. japonicum 35 Cary Engleberg

37 Schistosomiasis - life cycle S.m. S.h.S.j. Eggs Cercaria 36 Cary Engleberg (All other images) (snail) Pearson Scott Foresman, wikimedia commonswikimedia commons

38 S. mansoni S. haematobium S. japonicum 37 Source Undetermined

39 38 Source Undetermined

40 Events following cercarial penetration 1.Larva migrate to lungs and develop as “schistosomulae” (this may trigger a self- limited febrile illness). 2.Male and female schistomulae migrate to the abdominal venules: I.Superior mesenteric (S. japonicum) II.Inferior mesenteric (S. mansoni) III.Bladder plexus (S. hematobium) 3.Males and females pair off and egg production begins 4.Eggs migrate out of the body through visceral organs or become trapped and die in tissues. 39

41 Immune response to schistosoma infection 40 Source Undetermined

42 41 Source Undetermined

43 42 Source Undetermined

44 43 Source Undetermined

45 44 Source Undetermined

46 45 Source Undetermined

47 “pipestem” fibrosis 46 Source Undetermined

48 47 Source Undetermined

49 Schistosomiasis - pathogenesis egg granuloma (type IV reaction)--> fibrosis morbidity ~ worm (egg) burden concomitant immunity to schistosomula adult worms: invisible to the immune system (survive for years) 48

50 Schistosomiasis- clinical features Cercarial dermatitis Intestinal schistosomiasis (granulomas --> polyps, protein loss, malabsorption, strictures) Hepatosplenic schistosomiasis (portal hypertension --> ascites, varices, splenomegaly, normal hepatic function) Urinary schistosomiasis (hematuria, chronic infection, obstruction) Other (cardiopulmonary, CNS, etc.) 49

51 Drug treatment of schistosomiasis Praziquantel increases permeability of adult parasite to Ca ++. Tetanospasm --> death 50

52 Cestode infections 51

53 Tapeworms Definitive hosts: harbor adult worms Intermediate hosts: harbor tissue cysts (containing worm heads) Humans acquire infection two ways: – ingestion of eggs from feces (to acquire tissue cysts) – ingestion of tissue cysts in undercooked meat (to acquire a tapeworm) = Intermediate host = Definitive host 52

54 Taeniasis Tapeworm Cysticercosis poor hygiene poor sanitation ingestion of undercooked pork 53 Cary Engleberg (All other images) (pig) Martin von Nathusius, wikimedia commonswikimedia commons

55 54 Source Undetermined

56 55 Source Undetermined

57 56 Source Undetermined

58 57 Source Undetermined

59 CysticerciHydatid Cyst 58 C. Engleberg/V. Carruthers

60 Isolated cysticerciHydatid cyst 59 Source Undetermined

61 60 Source Undetermined Duane Newton

62 Echinococcosis Cystic Hydatid Disease contact with dogs ingestion of entrails ingestion of eggs in pastures 61 Cary Engleberg (All other images) (sheep) wikimedia commonswikimedia commons (dog) Abujoy, wikimedia commonswikimedia commons

63 62 Cary Engleberg

64 Treatment of cysticercosis and echinococcosis Antihelminthic therapy (e.g., albendazole, praziquantel) (Echinococcus only) – Surgical removal – Irrigation-evacuation of cysts 63

65 Comparison of pork tapeworm and Echinococcus life cycles Definitive hosts (adult tapeworms) Intermediate hosts (tissue cysts) Dead-end hosts Dog Sheep Human Pig Human 64 C. Engleberg/V. Carruthers

66 Slide 5: Cary Engleberg and Vernon Carruthers Slide 8: Cary Engleberg Slide 11: Cary Engleberg and Vernon Carruthers Slide 13: Cary Engleberg and Vernon Carruthers Slide 14: Cary Engleberg and Vernon Carruthers Slide 15: Source Undetermined Slide 19: Sources Undetermined Slide 25: Armed Forces Institute of Pathology, Slide 26: Source Undetermined Slide 27: Source Undetermined Slide 29: Source Undetermined Slide 30: Cary Engleberg (left) Sources Undetermined (right) Slide 31: Cary Engleberg Slide 32: Source Undetermined Slide 33: Source Undetermined Slide 36: Cary Engleberg Slide 37: (snail) Pearson Scott Foresman, Wikimedia Commons,; Cary Engleberg All other images) Slide 38: Sources Undetermined Slide 39: Source Undetermined Slide 41: Source Undetermined Slide 42: Source Undetermined Slide 43: Source Undetermined Slide 44: Source Undetermined Slide 45: Source Undetermined Slide 46: Source Undetermined Slide 47: Source Undetermined Slide 48: Source Undetermined Slide 54: (pig) Martin von Nathusius, Wikimedia Commons,; Cary Engleberg (All other images) Slide 55: Source Undetermined Slide 56: Source Undetermined Slide 57: Source Undetermined Slide 58: Source Undetermined Slide 59: Cary Engleberg and Vernon Carruthers Slide 60: Sources Undetermined Slide 61: Duane Newton, University fo Michigan Slide 62: (dog) Abujoy, Wikimedia Commons,, CC:BY-SA, sa/2.5/deed.en ; (sheep) Wikimedia Commons, ; Cary Engleberg (All other images) sa/2.5/deed.en Slide 63: Cary Engleberg Slide 65: Cary Engleberg and Vernon Carruthers Additional Source Information for more information see:

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