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Flashcards in Schistosomiasis Deck (17)
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What causes Schistosomiasis

Schistosoma hematobium (blood fluke)


Symptoms of Schistosomiasis

-Fatigue, headache, chills, aching muscles, abdominal pain
-men have enlarge penis and impotent
-burning during urination
-Bloody urine, bladder ulcers


Transmission Cycle

1) Microscopic eggs of S. hematobium are found in urine
2) When passed into water, the larvae (mircadia) inside the eggs sense a change in environment and begin moving until they burst out and can move freely
3) Spinning torpedoes now looking for snails (Bulinas Truncatus)
-if suitable host is found the larvae plunges (mircadia) inside the intermediate host and begin asexual reproduction/multiplication
-if not suitable host snail isn't near by they spin out and run out of energy and die
5)Once the parasites are mature, cercariae emerge from the snails and hang out like jellyfish
6)Cercariae punctures skin
7) enters the bloodstream and goes to the heart first then makes it way to other tissues
8) Final destination is bladder where they begin producing eggs
9) eggs are excreted through urine


Who is the intermediate host

Snails-Bulinas Truncatus


When people started settlements how was this perfect for parasites (what factors)

-Trading among communities occurred
-sewage treatment was poor- spread human and animal waste as fertilizer on crop land
- Drinking water become more contaminated w/feces and intestinal parasites boomed
-Domesticated animals, which allowed parasites to be passed back and forth between human and animal


What role did Jericho City of Palms play in history of parasites?

-A town that had an oasis as only water source, and people nearby came to use water source
-water was used for drinking, bathing, cooking, and restroom which was the end all of community
-oasis was perfect environment for snails (Bulinas truncatus) to thrive thus intermediate parasite was present
-everyone was infected, and Joshua and Hebrews attacked the town leaving only Rahab and family who had chronic infection and the army moved on

Town was left uninhabited thus the parasite didn't have a host to attack, droughts could have dried up the oasis, and eventually this was the first time the spread of a parasite was stopped



Percentage of infected in population



highest number of parasites per individual
-number of parasite per individual


Mean intensity

Average number of parasites per individual in a population


Parasitic load

-Measure of the number and virulence of the parasites that a host harbors
-Hard to compare different populations because not all individuals are infected and the number of parasites found per individual vary greatly (skewed)


Parasite Diversity

Infection rate was dependent on the order in which the parasites are added, whether newly added parasites replaced other species or coexisted, and order the parasites were added
-If dangerous parasite is first on scene, it will be replaced when less dangerous are added thus decreasing the odds of host disease
-If dangerous parasite is added last, results in neutral effect or increase in disease

Bottomline: Increase parasite diversity almost always decreased the level of parasitic infection (Competition is good)


Flatworm parasite on frogs

causes malformed limbs and premature death
-larvae burrow in tadpole limbs and forms cysts that disrupt normal frog and toad leg development causing extra or missing limbs



Diseases that can be spread from vertebrae animals to humans


Live Fluke target

the flatworm targets ants


Liver fluke

behavior controlling parasite


Transmission cycle of Liver Fluke and ants

1) ants consume slime of passing snail
2) the slime is loaded with the eggs of the liver fluke
3) Liver fluke burrows in a part of the ants brain and orders them to carry them to their next host--grazing mammals ex: cow
4) Liver fluke can switch the ants behavior on and off caused infected ants to place themselves in easy to eat positions
5) Cows ingest fluke larvae
6) Worms burrow out of the stomach into the liver and develop into adults and eat liver tissue
7) worms lay eggs that are excreted from the liver into the bile duct and produced in the feces during defecation


Liver fluke symptoms