Nematodes + Cestodes

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Nematodes + Cestodes
2011-09-19 20:39:00

Lessons 1-3
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  1. Which parasite has the highest worldwide mortality rate? a) Ascariasis b)Trichuriaisis c) Schistosomiasis d) Hookworm
    c) Schistosomiasis (280,000 deaths/yr), as opposed to hookworm (65,000), Ascariasis (60000), and Trichuriaisis (10000).
  2. True/False: Although helminth infections are deleterious to the host, most species will protect the host from infection by other species of helminth infections.
    False: One species does not protect against another; in fact it is rare for a patient to be infected by only one helminth species at a time.
  3. True/False: A common symptom of intestinal helminth infection is diarrhea.
    False: Absence of diarrhea is a way of distinguishing helminth infection from protozoan infection.
  4. Wearing shoes can help prevent infection by which two types of nematodes?
    Hookworms and Strongyloides (penetrate through skin)
  5. What is the magic bullet treatment for nematode infection?
    Albendazole (400mg PO x 1 day)
  6. What is the life cycle of Strongyloides after it has infected the human host? What other nematode has a similar life cycle?
    • Skin penetration --> lungs --> gut
    • Hookworm
  7. What is the life cycle of Ascaris after it has been ingested?
    Gut --> liver --> lungs --> gut
  8. Helminth infections are associated with high: a) IgG b) neutrophils c) eosinophils d) mast cells e) liquifactive necrosis
    c) eosinophils (and also high IgE)
  9. Loeffler's syndrome is characteristic of this kind of infection:
    Ascaris (Loeffler's syndrome refers to eosinophilic pneumonitis due to infiltration of ascaris into lung tissue)
  10. A patient presents with chronic iron-deficiency anemia and a high eosinophilic blood count. What type of helminth infection might you suspect?
    Hookworm (Hookworms latch on to the intestinal wall and suck blood directly. In patients with high worm burdens, a common finding is iron-deficiency anemia).
  11. What two types of intestinal nematodes are capable of autoinfection?
    Capillaria and strongyloides
  12. Perianal itching is characteristic of what kind of infection?
    Enterobius vermicularis (pinworm)
  13. True/False: If a helminth infection is treated in a baby, stunted growth and development will often self-correct.
    True: studies show that treatment can put underweight children back onto a normal growth chart
  14. How could you distinguish a Trichuris egg from a capillaria egg?
    Both are doubly- operculated, but the Trich egg is more football shaped (rounded, not rectangular), and the operculi are more prominent than the capillaria egg.Trichuiscapillaria
  15. Identify this egg:
  16. What type of nematode is shown here?
  17. Which type of hookworm has 'cutting plates', and which type has 'teeth'?
    • Necator americanus has cutting plates
    • Ancylostoma duodenale has teeth.
  18. Filarial parasites use what intermediate host? a) pigs b) cows c) dogs d) insects
    d) Insects.
  19. Lymphatic filariasis is transmitted by a mosquito vector. What is uncommon about its transmission?
    Most mosquito-borne parasites can only be transmitted by one or two species of mosquito, but LF can be transmitted by pretty much any species.
  20. Your patient has a high eosinophil count as well as mild scleritis. You suspect Loa loa and want to take a blood sample to confirm your diagnosis. What time of day should you take it?
    Daytime: Loa loa microfilaria circulate in the blood during the daytime, as opposed to lymphatic filariasis, which circulates at night.
  21. Your patient present complaining of progressive loss of vision and skin nodules. You notice severe keratinitis on the cornea (see picture). What diagnosis do you give, and how should you treat it?
    Onchocerciasis (characteristics are eye keratinitis and nodules with rash).Treat with Ivermectin 150mg/kg every 3-12 months.Key point: Ivermectin, not DEC; ongoing treatment, since you can't kill the adult worms.
  22. Which type of taenia tapeworm has four suckers, but no rostellar hooks?
    taenia saginata. (t. solum has four suckers and two rows of hooks. They can also be distinguished by proglottid uterine size: T. solum has fewer, larger uterine branches than T. saginata)
  23. What are three of the main tissues in which cysticerci from T. solium often encyst?
    subcutaneous, CNS, and eyes (although they can encyst in any tissue type- these are the most common).
  24. Treatment using PAIR (puncture, aspirate, introduce Protocolicide, reaspirate) refers to which kind of cestode infection?Echinococcus granulosus.
    Echinococcus granulosus.
  25. Proglottids shed in a patient's feces are noted to have rosette-shaped uteruses. You should suspect infection by: a) hymenolpis diminuta b) Echinococcus granulosus c) diphyllobothrium latum d) Taenia solium e) strongyloides
    c) diphyllobothrium latum. This is one of the hallmark characteristics of D. latum.