5.3 Biliogy of Parasites Flashcards
What are the two types of parasites?
Protozoa (unicellular) and Helminths (multicellular)
How are protozoa classified and give an example of each
By motlity Flagellate: Giardia Pseudopods: entemoeba histolytica Ciliates: Balantidium coli Coccidians: cryptosoridium
How are Helminths classified and give an example
Flatworms
- Trematodes: flukes
- Cestodes: tapeworm
Roundworms (nematodes)
- Blood tissue: Wuchereria boncrofti (elephantitis)
- Intestinal: PInworm, whipworm, hookworm, strongyloides stercoralis, ascaris lumbricodes
Define definitive host
parasite matures into adult form and undergoes sexual reproduction
Define intermediate host
parasite development occurs but parasite does not reach sexual maturity
define paratenic or transport host
parasite remains alive and infective but does not undergo any development
define incidental or dead end host
intermediate host that generally does not allow transmission to a definitive host
define host sensitivity
range of different hosts in which a parasite can mature
What is the process of parasitic disease in general>
Gain entry to the host (exogenous or endogenous)
Replicate/disseminate (intra or extracellular)
Cause damage to the host
Spread to a new victim
What factors affect infection, spread, replication and damage
Size
- Protozoa complete lifecycle in humans an usually have low infective dose
- Helminths severity usually related to size
Tissue tropism
Means of evading immune response
What are the general consequences of parasitic infection to the host?
Nutritional stress Mechanical or physical damage secondary infections toxicity immunopatholgical reactions
What is the lifecycle of giardia?
Exposure to stomach acids causes the release of four trophozoites
TZ colonise in small intestine
TZ undergo rapid asexual reproduction
Encystation occurs as transit through large intestine
What are the symptoms of giardia?
Asymptomatic Chronic diarrhoea Epigastric pain Nausea and vomiting Malabsorption Weight loss Symptoms typically 6-15 days after exposure
What is the pathophysiology of giardia?
Flattening of the villi and inflammation of mucus
Direct damage to intestinal brush border
Alteration of absorption
Alteration of small intestine function
Induction of a host immune response
What is the treatment for giardia?
Metronidazole