5_Helminthes 2

Question 1

Nematodes (Round worms):

characteristics

Answer 1

• cylindrical
• structure
  
  • body wall composed of outer cuticle, thin hypodermis, and musculature
  • tubular intestine w/ excretory gland
• sexual reproduction: testes & ovaries; copulation is necessary for fertilization

Question 2

pathogenesis of Nematodes

Answer 2

1. diseases are caused by direct damage from worm activity and immune rxn to them
2. large worms can physically block the intestine
3. Infxn is related to the # adn the infective stages encountered

Question 3

how do humans respond to infxn by Nematodes?

Answer 3

• children are more susceptible than adults
• waning of immune competence w/ age increases infxn
• Immunosuppressive therapies may inc. susceptibility
• immune defense thru production of IgE and action of mast cells and eosinophils

Question 4

what are the common nematodes to know?

Answer 4

• Pinworm (Enterobius cermicularis)
• Trichinella (Trichinella spiralis)
• Toxocariasis (Toxocara canis, Toxocara cati)
• Whipworm (Trichuris trichura)
• Ascariasis (Ascaris lumbricoides)
• Hookworm (Necator ameicanus, Ancylostoma duodenale)

Question 5

lifecycle for Enterobius vermicularis (Pinworm)

Answer 5

Question 6

life cycle of Trichinella spiralis

Answer 6

Question 7

name 2 worm infxns that one can contract by eating undercooked pork?

Answer 7

Taenea (tapeworm) and Trichinellosis

Question 8

which two species cause Toxocariasis,

and which animal causes it?

Answer 8

• Toxocara canis from dogs
• Toxocara cati from cats (less common)

Question 9

Life cycle of:

Toxocara species

Answer 9

Question 10

the eyes are affected by which worm infections?

Answer 10

• Toxocariasis - granuloma, ocular larva migrans
• Trichinella spiralis - swelling

Question 11

Which worm can cause splinter hemorrhages of the fingernails , or a cough?

Answer 11

Trichinella spiralis worm movement

Question 12

life cycle and transmission:

Trichuris trichiura

Answer 12

Question 13

life cycle of:

Ascaris lumbricoides

Answer 13

Question 14

which of the following nematode (round worms) infect w/in the GI tract only?

1. Pinworms
2. Whipworms
3. Trichinellosis
4. Ascariasis

Answer 14

Pinworms, and Whipworms

Question 15

Where do adult Schistosoma mansoni reside and is it in a round worm?

Answer 15

Veins that drain the intestine

S. mansoni is a type of flatworm (*NOT a roundworm)

Question 16

Hookworm infection:

causal agents,

how frequent?

transmission?

Answer 16

• causal agents:
  
  • Necator americanus - predominates in the Americas (north, central, and south america) and australia
  • Acylostoma duodenale - occurs in the middle east , southern europe, and north america
• 2nd most common human worm infection
• transmssion: soil-transmitted helminth (STH) - often occur in areas where human feces are used as fertilizer, or where degacation onto soil happens

Question 17

Life cycle of Hook worm

Answer 17

Question 18

Hookworm:

presentation

Answer 18

• infxn is not common in adults
• cutaneous larva migrans - red, intensely pruruitic (itchy), very painful, creeping eruption, ambiguously known as “ground itch”
  
  • usually heals spontaneously over wks to months
  • scratched may allow a secondary bacterial infxn to develop

Question 19

High intensity Hookworm:

affects which groups?

which symptoms?

Answer 19

• *High intensity hookworm infxns: occur in school-age children
• Sxs: development of anemia & protein deficiency caused by blood loss @ site of intestinal attachment
  
  • When continuously infected by many worms, children have loss of iron and protein, can lead to retarded growth and mental development

Question 20

Zoonotic hookworms?

key characteristics

Answer 20

• Common in puppies/kittens, esp in areas w/ wamrer climates
• Causal agents: Ancylostoma braziliense, A. caninum, A. tubaeforme
• Transmitted in dog & cat feces, w/ warm, moist conditions hatch into larvae after several days
  
  • larvae of dog hookworms –> can infect people
  • larvae penetrate skin while people walk barefoot, or w/ exposed skin contact w/ contaminated soil/sand
  • larvae –> cutaneous larval migrans –> which don’t usually develop into adult hookworms in people –> larvae will die in the skin after several weeks w/o developing any further
    *

Question 21

Strongyloidiasis:

1. etiologic agent, hx
2. transmission

Answer 21

1. causal agent: Stronglyoides stercoralis –> described in French troops stationed in Vietnam during the late 19th century
2. Transmission: thru exposed skin, e.g. barefeet

Question 22

Strongyloidiasis:

typical manifestation

Answer 22

• Manifestation: most infected people remain asymptomatic/undiagnosed
• Larva currens: intensely itchy creeping raised rash, also known as ground itch
  
  • Allergic response to migrating filariform larvae
  • Appears recurrently along the thighs and buttocks, the site of skin penetration & intradermal migration
  • May last hours to days but in autoinfxn cycles can recur over weeks, months, & years
• Tracheal irritation & dry cough: as larvae migrate from the lungs up thru the trachea
• GI disturbance: abdominal pain, intermittent diarrhea/constipation, fecal occult blood, massive colonic and gastric hemorrhage

Question 23

Strongyloidiasis:

more serious manifestation

Answer 23

• More serious manifestations: larvae invades numerous organs
• Severe life-threatening forms of disease (fatality approaches 90%)
• Affects pts receiving high-dose corticosteroids for the tx of asthma or COPD, and in patients getting immunosuppressive drugs bc of transplants (due to impaired host immunity à accelerated autoinfxn & # of migrating larvae)
• Pulmonary infiltrates, acute respiratory distress syndrome (ARDS), small bowel obstruction, & multisystem organ system, & rapid clinical decline

Question 24

Which of the helminths cause pneumonia by migration to the lung is a step of the life cycle?

1. Ascaris lumbricoides
2. Anclyostoma duodenale
3. Trichinellaosis (Trichinella spiralis)
4. Toxocariasis (Toxocara canis, Toxocara cati)
5. Strongyloidiasis (Strongyloides steroiralis)

Answer 24

1, 2, and 5

• Ascaris lumbricoides
• Anclyostoma duodenale
• Strongyloidiasis (Strongyloides steroiralis)

Question 25

Guinea worm disease: life cycle

Answer 25

Question 26

**Guinea worm:** causal agent, epidemiology, sxs, complications

Answer 26

Question 27

Prevention and control of ## Footnote **Guinea worm disease**

Answer 27

* **Safe water --\>** using water filters * Health education and community mobilization * teaching communities about the disease and how it's spread * chemically killing worms in water * identifying infected person w/in 24 hours of worm emerging * person should receive proper tx and **case management** by local health provider * w/in 7 days of worm emerging, GWEP supervisor determines that above criteria has been met

Question 28

Which of the following worms enter orally and move outside of GI tract? 1. Ascariasis 2. Hookworm 3. Strongyloides 4. Guinea worm

Answer 28

* Ascariasis * Guinea worm

Question 29

**Lymphatic Filariasis - Elephantiasis** life cycle and transmission

Answer 29

Question 30

**Lymphatic Filariasis-Elephantiasis:** causal agent, epidemiology transmission

Question 31

**Lymphatic Filariasis-Elephantiasis:** symptoms, prevention and control

Answer 31

Sxs: Lymphedema of limbs, hydrocoele, chyluria * Majority of pts are asymptomatic, but virtually all of them have subclinical lymphatic damage * As many as 40% have kidney damage, w/ proteinuria & hematuria * Recurrent acute attacks – extremely painful, accompanied by fever Prevention/Control: take precaution when traveling to an area w/ lymphatic filariasis * Sleep in air-conditioned room or under mosquito net; wear long-sleeves & trousers * Use mosquito repellant on exposed skin between dusk and dawn * Global campaign to eliminate lymphatic filariasis --\> annual mass tx, and controlling mosquito

Question 32

Round worms are not transmitted by insect bites: TRUE/FALSE

Answer 32

False, can be via insect bites, but can also be transmitted thru soil (e.g. Filariasis-Elephantiasis)

Question 33

# Define: Neglected parasitic infections What are the top 5?

Answer 33

* NPI: relatively little attention has been devoted to surveillance, prevention, and/or tx * Incl: 1. **Chagas disease** 2. **cysticercosis** 3. **toxocariasis** 4. **toxoplasmosis** 5. **trichomoniasis**

Question 34

Which of the following worms infect by skin penetration? * Schistosoma haematobium * Dracunuculus medinensis (GWD) * Anclyostoma duodenale (Hookworms) * Anclyostoma braziliense (Dog hookworm) * Stronglyoides steroralis

Answer 34

* Schistosoma haematobium * Anclyostoma duodenale (Hookworms) * Anclyostoma braziliense (Dog hookworm) * Stronglyoides steroralis (All except Dracunulus medinensis (GWD), which is transmitted by infected copepods in unfiltered water)