Blood flukes

Question 1

What are 4 major differences between Schistosomes and other Trematodes?

Answer 1

• Seperate sexes (dioecious)
• Males have gynecophoric canal where females reside
• Absent cirrus
• No redial stage
• Acetabulum near mouth area

Question 2

What are the 3 major Schistosome parasites discussed?

Answer 2

Schistosoma haematobium, S. mansoni, & S. japonicum

Question 3

S. haematobium lives in veins of ___

Answer 3

urinary bladder

Question 4

S. mansoni prefers the veins of the___

Answer 4

large intestine

Question 5

S. japonicum prefers the veins of the___

Answer 5

small intestine

Question 6

____eggs are passed in feces,have a large lateral spine, and measure 150 um in length

Answer 6

S. mansoni

Question 7

___eggs are passed in the urine, have a prominent terminal end spine, and measure 150 um in length

Answer 7

S. haematobium

Question 8

___eggs are passed in the feces, have a vestigial, nubby, lateral spine, more rounded than the other 2 species, and measure ~100 um in length

Answer 8

S. japonicum

Question 9

Give me the schistosoma life cycle

Answer 9

1. Eggs passed in urine (S. haematobium) or feces (S. japonicum, S. mansoni) into fresh water.
2. Miracidium hatches from egg, infects first intermediate host (a snail)
3. Cercariae leave snail, penetrate skin of human who is in water
4. Immature worm enters the blood stream and eventually ends up in veins near intestine (S. japonicum, S. mansoni) or bladder (S. haematobium).
5. Worms reach sexual maturity in veins of abdominal cavity, females produce eggs, eggs enter intestinal tract or bladder

Question 10

The infective stage of schistosoma is___

Answer 10

Cercaria

Question 11

Egypt has one of the highest cases since both_____and__ occur with great frequency. In the population of some endemic areas of the Nile Valley, the infection rate > 80%

Answer 11

S. mansoni and S. haematobium

Question 12

____is the most common cause of bladder calcification, causing 50% of known bladder calcifications

Answer 12

Schistosomiasis

Question 13

Urolithiasis is caused by___

Answer 13

Schistosomiasis

Question 14

____is the single most important epidemiological factor in schistosomiasis

Answer 14

Human waste in water containing snail hosts

Question 15

___is found in many countries in Africa, South America (Brazil, Surinam and Venezuela), the Caribbean (including Puerto Rico, St Lucia, Guadeloupe, Martinique, Dominican Republic, Antigua and Montserat) and in parts of the Middle East. Reservoir hosts are not important for this species of schistosome

Answer 15

S. mansoni

Question 16

____is found in large parts of Africa, parts of the Arabia, the Middle East, Khuzestan Province in Iran, Madagascar and Mauritius. Reservoir hosts are not thought to be of importance for this species.

Answer 16

S. haematobium

Question 17

How do humans get swimmers itch?

Answer 17

Humans are exposed to the dermatitis-producing cercariae. Humans are attacked by non human cercariae (bird blood flukes) that dont enter the blood stream

Question 18

Describe the initial phase of schistosomiasis

Answer 18

4-10 wk after infection, during which migration takes place from lungs to liver to hepatic portal system.

Fever and allergies (frequently skin rashes), abdominal pain, bronchitis, enlargement of the liver and spleen, and diarrhea are common symptoms.

The most serious damage is done by the eggs in all 3 spp.

Question 19

Describe the intermediate phase of schistosomiasis

Answer 19

. Intermediate phase: is much longer, lasting 2 months to many years after infection. Bloody stools result as intestines are most notably affected (S. japonicum & S. mansoni).
Hematuria (blood in urine) is common due to passage of S. haematobium eggs via urinary bladder. Other symptoms include frequent urination and dysuria (painful urination)

Question 20

Describe the final phase of schistosomiasis

Answer 20

Final phase: most serious; characterized by severe intestinal, renal, and hepatic pathology, caused primarily by rx. of the host to the eggs. Eggs lodged in venuoles act as foreign bodies and cause inflammatory rxs, even cirrhosis and anemia. These finally become small fibrous nodules which are also called granuloma or pseudotubercles

Small abscesses occur, leading to necrosis and ulceration

A marked enlargement of the liver and spleen (hepatosplenomelagy) occurs

Repeated infection of S. haematobium, as encountered in Egyptian farmers, commonly lead to bladder cancer

Question 21

What Schistosome causes urogenital schistosomiasis? What are symptoms?

Answer 21

Schistosoma haematobium.

range of signs and symptoms including lesions of the cervix and vagina, vaginal bleeding, pain during sexual intercourse and nodules in vulva

Bladder and ureteral fibrosis and hydronephrosis (swelling of kidneys due to backup of urine) are common findings in advanced cases

Question 22

Why is Schistosoma japonicum the most dangerous form of schistosomas

Answer 22

because it produces up to 3,000 eggs per day, ten times greater than that ofS. mansoni

it has a very wide range of species it infects, 31 different species

2/3 of the eggs of S. japonicum are not excreted, leads to fibrosis in chronic cases

Question 23

What are 5 methods for control in areas endemic to schistosomiasis?

Answer 23

5 methods of control:

• prevention of water contact
• mass chemotherapy
• destruction of snails (chemical: iron phosphate, aluminium sulfate, etc.), biological agents (crayfish, etc.))
• alteration of habitats
• sanitary disposal of feces, urine

Question 24

What are common symptoms of Schistosomiasis?

Answer 24

Hepatosplenomegaly
ascites (fluid inside belly)
-muscle atrophy, 
-pyrexia (fever),
-anemia
-haemorrhage from the gastrointestinal tract