What parasites do Flashcards
What do all parasites need to do for survival
Achieve transmission
Enter its host
Migrate to appropriate site or tissue
Maintain that position
Find a mate
Successfully reproduce
Release progeny
Develop inside host
Cope with physiology of host
Evade destruction
What is fundamental imperative for a parasite?
Transmission
why does transmission need to coccur
Needs to get into a new host
Other life cycle events cannot occur if it does not reach a host
The way a parasite moves from host to host
mode of transmission
-the specific way that parasite gets from one host to another
transmission used by intestinal protozoa and many intestinal helminths
Fecal-oral transmission
Describe fecal-oral transmission
Propagules are released in feces
-usually metabolically inactive eggs or cysts
In contaminate food or water consumed by host
Why in fecal-oral are the eggs inactive
Because the eggs need to survive in external environment till digested by host
-In a dormant state till right conditions occur
Giardia Lamblia fecal oral
Trophozoites live in host’s small intestines, actively feeding and reproducing by binary fission
Under specific physiological conditions within the host, the trophozoite may transform into a non replicating, dormant cyst
Cysts then can persist for a few months in the environment till entering a new host
Transmission from an intermediate to definitive host by consumption of infected individual
Trophic Transmission
Describe trophic transmission
-Transmission from an intermediate to definitive host by consumption of infected individual
-Takes advantage of the predator-prey relationship
-Often alternates with fecal-oral transmission
Hymenolepis diminuta (Rat tapeworm)
-Rat eggs pass in feces
-arthropod (intermediate host eats the eggs
-that being fecal-oral
-eggs hatch in digestive system releasing oncosphere
-Oncosphere penetrates the gut wall, where it develops into a cysticercoid in the body cavity
-Rat eats the insect (trophic transmission) this is wear the cysiceroids develop into tapeworms
Some parasites actively seek out their host and bore their way inside
Direct Penetration
Ichthyopthirius multifilis (Ich) cycle
-A parasitic ciliate the causes whiespots on fish
-Reproduction occurs in cyst like structures on bottom of water bodies
-50-1000 new trophozoites releases (tomites)
-Motile tomites contacts fish penetrate epithelium and feeds on dying cells in pustules
-Pustules rupture, releasing trophozited into environment
How does direct penetration make sure it finds a host and what happens if it doesn’t
Motile stages put themselves in a good position to be able to get a host easier/quicker
-Where hosts congregate
-They emerge at the right time of day and year
Most have a matter of hours to achieve transmission before the outside environment kills it
What is vector transmission
Most are arthropods
-Parasite has to be able to develop without killing the vector
-Leads to specific parasite-vector relationships
-The parasite will adapt the vector feeding activity so it eats more from a host
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