Trematodes - Blood Flukes
What does sexually dimorphic mean?
Males & females look different
What happens to female that is not paired to male?
She will not reach sexual maturity unless she is around a male
Name 5 major differences between schistosomes and other trematodes.
) Are dioecious o 2) Have non-operculated eggs o 3) Have no pharynx o 4) No redia or metacercaria stage o 5) Live in blood vessels
What is the common name of the Schistosoma?
Blood flukes
How do Schistosoma mansoni eggs exit the host?
Endothelial cells exclude egg from vein and a granuloma carries egg into intestinal lumen
What are the functions of the following cercarial glands?
Escape produce enzymes that allow cercaria to exit the snail post-acetabular produces mucus that allows for attachment pre-acetabular involved with penetrating the snail head adjusting to definitive host
In which of the following is the schistosome species correctly paired with one of its characteristics?
Schistosoma japonicum - main pathology caused by eggs
What is SEA?
Soluble Egg Antigen - released by miracidia through egg pores
Where can the eggs become trapped?
in gut/bladder wall or liver/spleen
What is Symmer's pipestem fibrosis?
o Accumulation of granuloma causes this o Occurs in the liver leads to hepatomegaly
How can kidney failure result from a S. haematobium infection?
o Accumulation of granuloma in urinary bladder damages ureters & bladder o Backpressure of urine reaches the kidney & causes kidney failure
What is it known as after the cercaria penetrates the DH?
o After losing tail & glycocalyx now known as Schistosomulum
What does artemether do to the worms?
o Artemether damages tegument & cecum of Schistosomes
Why don't adult worms have a pharynx?
o Because schistosomes feed on blood do not need pharynx to break down tissue
What are the benefits and costs of the granuloma to the host?
o Benefits granuloma protects the host against any toxins released from egg o Costs costly in terms of pathology to host Accumulation of granuloma can lead to Symmer's pipestem fibrosis
What pathology results from penetration of the cercariae into the definitive host?
o Cercarial dermatitis itchy rash
15. Describe some methods of controlling schistosome infections.
o Chemotherapy, waste disposal, distribution of boots/gloves to people in contact with water, education, vaccine o Schistosomiasis Control Initiative funded by Bill & Melinda Gates Foundation Provides Praziquantel to Sub-Saharan Africa
What is the granulomatous response?
o Eggs are antigenic - stimulate an immune response in response to the SEA produced by the miracidia o Host fibroblasts produce connective tissue that surrounds the egg eventually miradicia will die
How does hatching of the miracidium from the egg occur?
o Fresh water stimulates cilia of miracidium to beat rapidly o Causes miracidium to put pressure on suture (structure along eggshell) o Suture ruptures miracidia escape & enter water
What is the function of glutathione-S-transferase in schistosomes?
o GST glutathione-S-transferase - is a parasite enzyme for Schistosomes o Being used as possible vaccine will stimulate immune response in host
Where is the gynecophoral canal found and what is its function?
o Gynecophoral canal found in male schistosomes Holds female in canal male & female undergo continuous mating Necessary for female to be in gynocophoral canal to develop fully
What is hematuria?
o Hematuria blood in urine ("male menstruation")
What is the relationship of schistosome infections to cancer?
o Increased rates of bladder cancer where Schistosoma haematobium is common o Increased rates of colon cancer where Schistosoma mansoni is common
Describe how the eggs of schistosomes exit the body of the definitive host. Include in your description the following: migration of the mated pair, migration of the female, endothelial cells, miracidial SEA, eosinophils & macrophages, granuloma, wall, and lumen.
o Mated pair travels to smaller veins o Female will temporarily leave male & move into smaller veins until can't move any more Will lay eggs there & then return to male o Endothelial cells constantly moving over the eggs excluding them from vein lumen o Miracidium is fully developed within egg will release SEA (soluble egg antigen) through eggshell pores o SEA stimulates immune response from host - formation of granuloma around egg Granuloma host response that consists of eosinophils & macrophages (motile & host immune cells) o Granuloma moves egg to either intestine or bladder lumen Some eggs will be released in either urine or fecal material o Remaining eggs get trapped in gut/bladder wall or liver/spleen
What larval stages occur in a schistosome life cycle?
o Miracidia Sporocyst Cercaria Schistosomulum
What changes occur in the cercaria once it penetrates the definitive host?
o Once cercaria penetrate host lose tail & glycocalyx (for Schistosomes)
o Praziquantel
o Praziquantel damages tegument makes worm more vulnerable to immune responses
What is the treatment for schistosomiasis and how does the drug work?
o Praziquantel damages tegument makes worm more vulnerable to immune responses o Artemether also used damages tegument & cecum of Schistosomes
Is resistance to this drug developing?
o Resistance may be developing more emphasis on research/development of other drugs now
Which three species are of major human health importance?
o Schistosoma mansoni Large intestine; lateral spine o Schistosoma haematobium urinary bladder; terminal spine o Schistosoma japonicum small intestine; small lateral knob
For each of the human schistosomes, describe the morphology of the egg.
o Schistosoma mansoni lateral spine o Schistosoma haematobium terminal spine o Schistosoma japonicum small lateral knob
How are schistosome infections diagnosed?
o Schistosoma mansoni & Schistosoma japonicum look for eggs in feces o Schistosoma haematobium look for eggs in feces & urine Also look for symptom called hematuria
Trace the migration path of a schistosomulum in the definitive host.
o Schistosomulum penetrate into bloodstream migrate to lungs & live in pulmonary capillaries o After reaching young adults migrate to systemic circulation o Adult stage move to hepatic portal veins of liver - where they reach sexual maturity o After male & females will pair up & migrate to venules of mesentery
What is the function of the suture in the egg?
o Structure along eggshell that ruptures during hatching
Is schistosomiasis a major problem throughout the world?
o YES over 200 million people infected; 2nd to malaria
o Artemether
used damages tegument & cecum of Schistosomes
