4_Helminths 1

Question 1

what are platyhelminths,

and what are the 2 major classes?

Answer 1

• flatworms = platyhelminths
  
  • trematodes (flukes)
  • cestodes (tapeworms)

Question 2

trematodes (flukes):

key characteristics

Answer 2

• symmetrical, non-segmental body
• possesses:
  
  • blind gut (mouth but no anus)
  • nerve cord
• sexual reproduction
• **looks like a leaf

Question 3

what is the parasitic disease (second to malaria) w/ the greatest economic impact?

Answer 3

Schistosomiasis.

Not found in US, but considered a Neglected Tropical Disease

Question 4

3 species of schistosoma, and respective locations

Answer 4

Question 5

what parasite can cause cercarial dermatitis?

what is necessary for transmission of this parasite?

Answer 5

• caused by certain species of schistosomes that parasitize in birds/mammals;
• human contact w/ water is necessary for infxn

Question 6

life cycle:

schistosoma species

Answer 6

• infective stage: cercariae (fluke)
• diagnosis stage: eggs

Question 7

Katayama fever is associated w/ which parasite?

Answer 7

acute infection caused by Schistosoma species;

sxs: fever, chills, cough, muscle aches

Question 8

Cercarial dermatits:

• caused by;
• transmission
• clinical presentation

Answer 8

• caused by: cercariae of certain species of Schistosoma, normal hosts are birds
• transmission: huamns are infected by contact in water
  
  1. infected birds secrete eggs in feces
  2. parasite hatches –> infects snails
  3. snails produce /release cercariae (the fluke)
  4. cercariae penetrates skin of swimmers
• clinical sxs:
  
  • tingling, burning, itching of the skin w/in min. to days after swimming in contaminated water
  • small reddish pimples that develop into small blisters
  • scratching the areas may result in secondary bacterial infxn
  • itching can last for 1 wk or more –> gradually will go away (self-limiting allergic rxn)
• tx: systemic antihistamines, topical corticosteroids to reduce sxs

Question 9

Cestodes (tapeworms):

key characteristics

Answer 9

• Scolex: anteria end bearing suckers and hooks
• Segmented body – absorbs nutrients through it’s skin
• Proglottid (segment) contains independent digestive system and repro tract
  
  • new segments are produced by neckpiece
  • older segments are pushed toward tip of the tail
  • segments that reach the end only have repro tract left (Gravid proglottids)
• Segment (sack of eggs) separates, carrying tapeworm eggs out of the host

Question 10

which cestodes are pathogenic to humans,

and therefore clinically important?

Answer 10

• Taenia solium (pork tapeworm)
• Taenia saginata (beef tapeworm)
• Diphyllobothrium latum (fish tapeworm)
• Hymenolepis nana (dwarf tapeworm)

Echinoccus granulosus (hydatid tapeworm)

Question 11

life cycle for:

taenia solium and taenia saginata

Answer 11

1. infective stage, and
2. diagnosis stage

Question 12

life cycle for:

diphyllobothrium

Answer 12

• Infective stage : larvae
• Diagnostic stage: eggs in stool

Question 13

prevention for tapeworms:

Answer 13

• Cook meat to safe temp;
• Wash hands w/ soap/water before handling food, after handling dogs
• When traveling to countries w/ likely contaminated food – wash/peel/cook all raw fruits/vegetables w/ safe water before eating

Question 14

Life cycle of Echinococcus granulosus

Answer 14

Diagnostic and infective stage