Pathogenesis of Parasitic Diseases Flashcards
Do all parasite infections result in disease?
no they can be subclinical
define subclinical infections
lack signs/symptoms
what does the likelihood and severity of parasitic disease depend on?
-status of host defenses
-number of parasites present
-parasite pathogenicity
What are mixed infections?
infections from multiple parasites at the same time
what effect do mixed infections have on the host?
additive pathogenic effects
what is this an example?
mixed infection
what might pathology result from in a parasite infection?
-damage to &/or loss of host cells, tissues, and organs
-alteration of host cellular growth patterns
-interference with host nutrition
-toxins released by the parasites
-host immune response to infection/infestation
How can parasites cause damage to &/or loss of host cells, tissues, and organs?
-destruction/loss due to migrating, developing, feeding, or reproducing stages
-obstruction of hollow structures by worms
-compression or distension of structure by larval or adult worms
How can parasites cause alteration of host cellular growth patterns?
cellular hypertrophy
hyperplasia
metaplasia
neoplasia
define cellular hypertrophy
an increase in cell size without an increase in cell number
define hyperplasia
increased cell production in a normal tissue or organ -> enlargement
define metaplasia
cells replaced with cells of another type
define neoplasia
uncontrolled, abnormal growth of cells or tissues in the body -> development of a tumor
what is a parasite that causes cellular hypertrophy? (name and location of condition)
cardiomyocytes and Trypanosma cruzi
what is a parasite that causes hyperplasia? (name and location of condition)
abomasal mucous neck cells and Ostertagia ostertagi
what is a parasite that causes metaplasia? (name and location of condition)
skeletal muscle fibers & Trichinella spiralis
what is a parasite that causes neoplasia? (name and location of condition)
esophageal sarcoma (dogs) & Spirocera lupi
what type of parasites causes hyperplasia, metaplasia, and neoplasia?
nematodes
How can parasites cause interference with host nutrition?
-diversion of nutrients to parasite
-malabsorption of nutrients
what is a parasite that diverts nutrients to itself? (Action and name)
ingestion of chyme - Ascaris suum
absorption of vitamins - Dubthricephalus latus & V B12
what is a parasite that causes malabsorption of nutrients? (name)
Giardia
what is a toxin that is produced by plasmodium (malarium)? what is it?
Hemozoin - crystallized dimers of heme
what does Hemozoin do to the host?
impairs phagocytic function
How is Hemozoin created within the host?
Plasmodium parasites absorb/digest hemoglobin and produce Hemozoin as a result
How does hemozoin impair phagocytic function?
macrophages and other phagocytes ingest hemozoin and become impaired
what are the types of cells that hemozoin infects?
phagocytes and RBCS
How can parasites cause host immune response to the infection/infestation that results in pathology?
-parasite-induced immunopathology
-flea allergy dermatitis
what is parasite-induced immunopathology?
damage that occurs as a result of an inappropriate immune response to infection or infestation
what is flea allergy dermatitis?
hypersensitivity to allergens in flea saliva
what type is hypersensitivity is flea allergy dermatitis?
types I, IV, cutaneous basophil
what is an example of a parasite that causes behavioral changes that facilitate transmission of parasites?
Taenia multiceps - tapeworm
How does Taenia multiceps cause behavioral changes that facilitate transmission of parasites?
Coenurus (larval stage) reside in the brain of the sheep -> gid (ataxia, circling, etc) -> easy prey for canids (facilitating transmission)
what are the two reasons for behavioral changes from parasites?
-facilitate transmission
-mere side effects of infection
what is an example of a parasite that causes behavioral changes that are a mere side effect of infection?
Oestrus ovis - sheep nasal botfly
How do Oestrus ovis cause behavioral changes?
larvae infect nasal/paranasal sinuses of sheep -> rarely migrate into brain -> false gid -> easy prey, but larval botflies die
Define virulence factors
factors that confer pathogenicity
what are examples of parasitic protozoa and their virulence factors?
Plasmodium spp. - hemozoin
Leishmania spp. - proteases
Toxoplasma gondii - kinase
How are proteases in Leishmania spp. a virulence factor?
tissues invasion -> survival in microphages -> immune modulation by parasite
How are kinases in Toxoplasma gondii a virulence factor?
disrupt host cell signaling, immunomodulation by parasite
what are examples of metazoan parasite and their virulence factors?
- nematodes, tapeworms, trematodes, ticks, mosquitoes, other ectoparasites -> proteases
- blood-feeding helminths & ectoparasites -> anticoagulants
-helminths -> excretory/secretory products
How are proteases a virulence factor in metazoan parasites?
-nematodes, tapeworms, trematodes -> tissue invasion; immune modulation
- ticks, mosquitoes, other ectoparasites -> diminish pain at bite wound
what are some of the excretory/secretory products of helminths?
proteins, glycoproteins, peptides, glycans, glycolipids, eicosanoids, etc.
How are excretory/secretory products of helminths a virulence factor?
function in immune modulation by parasite
what affects the likelihood and extent of parasitic diease?
host factors
What are some host factors affecting the likelihood & extent of parasitic disease?
age, sex/reproductive condition, nutritional state, immunological competency, genotype
what age of hosts are the most at risk for parasitic diseases?
young and geriatric hosts
what sex generally carries more parasites?
males
who is more susceptible to parasitic disease - pregnant, postpartum, & lactating females or non-reproductive females?
pregnant, postpartum, & lactating females
How does nutritional state affect the likelihood and extent of parasitic disease?
malnourishment -> decreased resistance & resilience
how does having prior exposure to a parasite affect the likelihood and extent of parasitic disease?
prior exposure -> partial immunity ->reduced number, migration, development, and reproduction of parasites
Define premunition
partial immunity do to chronic, low-level infection; protects host against superinfection and more severe pathology
define superinfection
Infectious process in which a second infection develops additionally
what are the factors that contribute to immunological competency?
-immunodeficient vs immunocompetent hosts
-prior exposure
-immunization statue
How does genotype effect the extent of parasitic disease?
a host’s resistance to infection has a genetic component
what are the factors that influence pathogenic potential of a parasite?
-predilection site
-migratory pathway
-sites of parasite development
-feeding habits
-immunopathology
-transmission of other infectious agents
what does Ostertagia ostertagi cause?
chronic abomastitis in young cattle
what is the predilection site of Ostertagia ostertagi?
abomasum
what is the migratory pathway of Ostertagia ostertagi?
local (w/in abomasum)
what is the site of parasite development of Ostertagia ostertagi?
gastric glands of abomasum
what are the feeding habits of Ostertagia ostertagi?
adults feed on abosmasal contents and epithelial tissues
what is the immunopathology of Ostertagia ostertagi?
inflammation induced by larvae & adults
what is the transmission of other infectious agents for Ostertagia ostertagi?
none
what phase of Ostertagia ostertagi grows in the parietal and chief cells?
larva
what does Ostertagia ostertagi do to the parietal and chief cells in the abomasum?
erodes parietal & chief cells -> inc pH, dec pepsin
what do emerging adults of Ostertagia ostertagi do to the abomasum?
further damage epithelium
what are the consequences of emerging adults of Ostertagia ostertagi in the abomasum?
loss of serum proteins, diarrhea
what are the consequences of larva of Ostertagia ostertagi in the abomasum?
consequences: impaired protein digestion, bacterial overgrowth, diarrhea
what does the inflammation of Ostertagia ostertagi result in?
-further loss of parietal & chief cells
-mucous neck cell hyperplasia
-parietal & chief cells replaced by mucous neck cells (metaplasia)
-inc vascular permeability -> epithelium becoming leaky -> loss of serum proteins, diarrhea
