Schistosomiasis

Question 1

What is schistosomiasis?

Answer 1

snail fever caused by blood flukes that live in veins of DH (>200 million people infected worldwide)

Question 2

What are the 3 species in humans?

Answer 2

1. schistosoma mansoni 2. haematobium 3. japonicum

Question 3

What are the major differences between schistosomes & other trematodes?

Answer 3

1. dioecious (separate male & female) 2. live in blood vessels 3. nonperculated eggs 4. no redia stage 5. no metacercarial stage 6. not food borne

Question 4

Describe the life cycle of schistosome?

Answer 4

1. egg 2. hatching 3. miracidium (male or female infects snails) 4. sporocyst -> daughter sporocysts 5. no rediae 6. cercaria 7. schistomsomula 8. adults

Question 5

What happens during hatching?

Answer 5

stimulus is fresh water. cilia beat rapidly -> miracridium moves & spins. suture ruptures. miracidium escapes

Question 6

Describes the parts of the cercaria head.

Answer 6

1. glands: escape -> exit snail 2. post-acetabular: mucus -> attachment 3. pre-acetabular: enzymes -> penetration of host skin 4. head -> adjustment penetrating DH -> penetrates DH

Question 7

Describe some characteristics of schistosomula.

Answer 7

in bloodstream migrate to lung live in pulmonary capillaries: feed on RBCs, grow/develop, systemic circulation -> young adults

Question 8

Where do adults migrate to? What do they do here?

Answer 8

migrate to hepatic portal vein. reach sexual maturity, mate, pair migrates to venules of mesentery and live 10-30 years

Question 9

Describe the morphology of adults?

Answer 9

1. no phargnx -> ingest blood 2. dioecious - separate sexes 3. sexually dimorphic

Question 10

Where is the gynecophoral canal found and what is its function?

Answer 10

inside the males it holds the female (shisto = split soma = body) allows for continuous mating

Question 11

What happens to a female that is not paired to a male?

Answer 11

does not mature

Question 12

Describe how the eggs of schistosome exit the body of the DH.

Answer 12

1. pair migrated to smaller veins 2. female migrates to the smallest veins 3. lays eggs 4. miracidial SEA is released 5. stimulates granulome to form around egg 6. granulomas moves to gut/bladder & transports egg across wall & into lumen 7. granuloma cells disperse 8. eggs exit host (2/3 eggs don’t make it out)

Question 13

What pathology results form penetration of cercariae into the DH?

Answer 13

cercarial dermatitis - allergic rxn, itchy skin

Question 14

Where can the egg become trapped?

Answer 14

gut/badder wall, liver, spleen

Question 15

What is the granulomatous response

Answer 15

SEA

Question 16

What is SEA?

Answer 16

soluble egg antigen w pore in eggshell

Question 17

What are the benefits and costs of the granuloma to the host?

Answer 17

protects the host but has costly pathology (ex: liver - Symmer’s pipestem)

Question 18

What is Symmer’s pipestem fibrosis?

Answer 18

in the liver: poor circulation, hepatomegaly, normal function impared

Question 19

How can kidney failure result from a S. haematobium infection?

Answer 19

eggs in urine and feces

Question 20

What Sh?

Answer 20

bladder cancer: eggs in urine & feces & hematoria

Question 21

What is Sm

Answer 21

colon cancer: eggs in feces

Question 22

How are schistosome infections diagnosed?

Answer 22

eggs in urine and feces

Question 23

What is hematuria?

Answer 23

blood in urine

Question 24

What is the treatment for schistosomiasis and how does the drug work?

Answer 24

praziquantiel damages tegument -> more vulnerable to immune response

Question 25

What does artemether do to the worms?

Answer 25

antimalarial drug that damanges tegument and cecum

Question 26

What is the function of the glutathione-S-transferase in schistosomes? (GST)

Answer 26

parasite enzyme with detoxifying function. vaccine targets GST and reduces worm burden by 40-60%

Question 27

Describe some methods of controlling schistosome infections.

Answer 27

1. drugs to kill adult worms 2. sanitation 3. snail control 4. boots & rubber gloves 5. vaccine (GST) 6. Schistomiasis Control Initiative (Bill & Melinda Gates Foundation) gives of PZQ in sub-saharan Africa