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Parsitology Lecture 3
Terms in this set (55)
objective measurement for example: (temp)
subjective measurement for example :(pain)
Set of signs and symptoms that are characteristic of the disease
can be defined as any alteration in the normal function of a cell, tissue, organ or organism
are those without overt signs or symptoms
The likelihood of overt disease is due to 3 factors
•Host immune competence
•Virulence of pathogen strain
All infectious diseases follow a certain course, a step by step progression that can be charted
•Convalescence or Death
Direct parasitic Damage entails
•Replication of parasites often directly leads to host damage
•Damage can be purely mechanical
•Example Case : Echinococcus cysts
90% of cysts occur in
•in the lung or liver or both.
May present as upper right quadrant pain and the liver may be enlarged/palpable.
Biliary obstructive jaundice
is possible due to cyst growth.
Mortality is around 2%
•Mortality is around 2% with E. multilocularis being slightly higher.
is life threatening and will present among classical lines as
Swelling of lips, tongue, vocal cords, bronchial airways, skin reactions, drop in blood pressure etc.
Direct Parasitic damage can come from?
•Direct damage can also be caused by tissue destruction.
Example: Entamoeba histolytica
•Distributed worldwide with most cases in tropical or subtropical countries with poor sanitation
•Prevalence is around 50 million worldwide
Humans and primates are the hosts and transmission is via the fecal oral route
Entamoeba histology mainily occurs in
90% are mainly asymptomatic
10% develop amoebic dysentery
How is dysentery affected the protoza in Entamoeba histolytica?
Protozoa invade into the intestinal epithelium causing cell death and tissue necrosis leading to bloody stools (dysentery)
Not only does Entamoeba histolytica cause dysentery but ulceration explain....
•Ulceration may continue and develop into fulminant amoebic colitis (FAC) which perforates the bowel and is highly leathal
Secondary bacterial infections are common
•Pathology can result in alteration of cell growth and division
Alteration of Cell Growth involves Hypertrophy:
Hypertrophy is an increase in cell size
•Well known result of parasitic infection
Leishmania - monocyte hypertrophy
•Trypanosoma cruzi - cardiomyocyte hypertrophy
increase in cell numbers
normal cell morphology
Fasciola Hepatica is a liver fluke that ......
resides in the bile duct and induces a proliferation of duct cells which feeds the fluke
Change from one differentiated cell type into another
•Often occurs to protect cells from constant inflammation or irritation
•Can but may not necessarily increase risk of cancer
is known to induce urinary tract metaplasia
•Dysregulated cell division (cancer)
•Benign or malignant based on presence of invasion
•Urinary metaplasia caused by
Schistosoma has been linked to cancer but not shown to be a definitive cause
Examples of neoplasia are
found in other mammals (dogs = Spirocerca lupi)
The intestinal protozoan
Giardia lamblia can have devastating effect on the host's nutrition especially in young children.
•Giardia lamblia proliferates
in the small intestines, attaching to the vili via its sucking disk
If the colony is large
it can lead to decreased host absorption of nutrients, particularly lipids
•This explains the oily stools seen in giardiasis
In host mal in child malnutrition causes
Decreased lipid absorption can also lead to deficiencies in lipid soluble vitamins
•Unlike bacterial pathogens
eukaryotic parasites rarely rely upon toxins to cause directed damage to the host.
For years toxin based damage was thought to be a critical
Trypanosoma infections but recent data makes this seem less likely
are the source of the disease malaria
Plasmodium parasites replicate in
red blood cells and produce hemozoin as a waste product from hemoglobin metabolism
When hemozoin is released into the blood it is phagocytosed by macrophages but
they can not degrade it. It builds up in the phagocyte and cripples it's ability to continue phagocytosis
What parasitic pathogens induce significant immune damage?
Plasmodium, Leishmania, Trypansoma, Toxoplasma, Schistosoma, Wuchereria
Immunopathology is referred to as
This immune driven damage
An example of immunopathology is
Plasmodium utilizes a number of pathogenic strategies which are
RBC hypertrophy, hemazoin secretion etc
Plasmodium falciparum is the
most virulent species, activates TLRs on vascular endothelial cells to induce cytokine driven damage in the brain called Cerebral Malaria.
Cerebral Malaria consist of
is the most serious possible P. falciparum complication
Misshapen, P. falciparum infected RBCs stick in the narrow passages of the capillary beds of the brain. This blocks blood flow and leads to ischemic tissue damage
P. falciparum DNA activates
•P. falciparum DNA activates TLR8 and TLR9. These TLRs promote vascular permeability which allows RBCs to leak through the capillaries into the brain leading to paralysis, coma and death.
In Granulomas formation , granulomas are
a common strategy when the immune system cannot destroy or remove large foreign objects or pathogens from the host.
Granulomas are a form of delayed hypersensitivity response and are constructed by
both the innate and adaptive arms of the immune system
•Chronic activation of the inflammatory response leads activated T cells and Macrophages to
damage local tissue and create a barrier of scar tissue
Granuloma Formation has a bacterial pathogen called
Mycobacterium tuberculosis is the classic example of a granulomatous disease
What often lead to granuloma formation?
Tissue embedded cysts or eggs of eukaryotic pathogens.
Granulomas cause significant ?
local tissue damage, scarring and can lead to organ failure
•Schistosoma eggs lodged in the liver are surrounded by
a thick granuloma capsule, replacing healthy liver tissue with inactive scar tissue and resulting in liver failure
Schistosoma eggs secrete their own chemokine that suppresses
the immune response against the egg (smCKBP)
Some parasites dysregulate the immune system to such an extent that they trigger an autoimmune disease in the host
Trypanosoma cruzi elicits an
an antibody response from the host. These anti-T. cruzi antibodies cross react with cardiomyoctes
After the parasite has been cleared by the immune system and or medical treatment
these autoimmune antibodies continue to attack the cardiac tissue
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