Blood flukes Flashcards
What are 4 major differences between Schistosomes and other Trematodes?
- Seperate sexes (dioecious)
- Males have gynecophoric canal where females reside
- Absent cirrus
- No redial stage
- Acetabulum near mouth area
What are the 3 major Schistosome parasites discussed?
Schistosoma haematobium, S. mansoni, & S. japonicum
S. haematobium lives in veins of ___
urinary bladder
S. mansoni prefers the veins of the___
large intestine
S. japonicum prefers the veins of the___
small intestine
____eggs are passed in feces,have a large lateral spine, and measure 150 um in length
S. mansoni
___eggs are passed in the urine, have a prominent terminal end spine, and measure 150 um in length
S. haematobium
___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
S. japonicum
Give me the schistosoma life cycle
- Eggs passed in urine (S. haematobium) or feces (S. japonicum, S. mansoni) into fresh water.
- Miracidium hatches from egg, infects first intermediate host (a snail)
- Cercariae leave snail, penetrate skin of human who is in water
- Immature worm enters the blood stream and eventually ends up in veins near intestine (S. japonicum, S. mansoni) or bladder (S. haematobium).
- Worms reach sexual maturity in veins of abdominal cavity, females produce eggs, eggs enter intestinal tract or bladder
The infective stage of schistosoma is___
Cercaria
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%
S. mansoni and S. haematobium
____is the most common cause of bladder calcification, causing 50% of known bladder calcifications
Schistosomiasis
Urolithiasis is caused by___
Schistosomiasis
____is the single most important epidemiological factor in schistosomiasis
Human waste in water containing snail hosts
___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
S. mansoni
____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.
S. haematobium
How do humans get swimmers itch?
Humans are exposed to the dermatitis-producing cercariae. Humans are attacked by non human cercariae (bird blood flukes) that dont enter the blood stream
Describe the initial phase of schistosomiasis
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.
Describe the intermediate phase of schistosomiasis
. 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)
Describe the final phase of schistosomiasis
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
What Schistosome causes urogenital schistosomiasis? What are symptoms?
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
Why is Schistosoma japonicum the most dangerous form of schistosomas
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
What are 5 methods for control in areas endemic to schistosomiasis?
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
What are common symptoms of Schistosomiasis?
Hepatosplenomegaly ascites (fluid inside belly) -muscle atrophy, -pyrexia (fever), -anemia -haemorrhage from the gastrointestinal tract