Lecture 3: Pathogenesis of Parasitic Diseases Flashcards
How can location be used for information on life cycle of parasite
Egg are ingested
hatched larvae in intestines
eggs in feces
Milk spots in liver and lung damage indicate what life cycle stage for ascaris suum
Hatched larvae
What does the likelihood and severity of a parasitic disease depend on
- Status of host defenses
- Number of parasites present
- Parasite pathogenicity
Pathology may result from….
- Damage and or loss to 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
What are mixed infections
More than one parasite- Additive pathogenic effects on host and may occur with gastrointestinal parasites
What are three ways parasites can cause damage to and 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 distesion of structures by larval or adult worms
How do ancylostoma caninum (hookworm) cause damage to tissue
Results in blood loss during feeding and also produces anticoagulants
How does dirofilaria immitis (heart worm) damage host cells, tissues and organs
Blocks pulmonary vessels and can cause pulmonary hypertension and heart failure
How does the larval stage (Coenurus) of Taenia multiceps tapeworm damage sheep brain
Forms cysts, puts compression on brain, result in Gid (ataxia and circling)
how does Ostertagi ostertagi cause damage to and/or loss of host cells, tissues and organs
Larvae develop in gastric glands and damage abomasal mucosa
how can parasites alter host cellular growth patterns
- Cellular hypertrophy
- Hyperplasia
- Metaplasia
- Neoplasia
What is an example of a parasite that causes cellular hypertrophy
Trypanosoma Cruzi in cardiomyoctes
What type of parasite is Trypanosoma cruzi
Protozoan
What is an example of a parasite that causes hyperplasia
Ostertagia ostertagi acting on abomasal mucous neck cells
How does Ostertagia ostertagi cause hyperplasia in abomasum
Causes cells in gastric pits in abomasum to overgrow and can been seen post mortem as bumps on abomasum
What is an example of a parasite that causes metaplasia
Trichinella spiralis and skeletal muscle fibers
Where does trichinella spiralis act and what does it do to cells
Goes into skeletal muscle fibers and changes cell type so no longer functional muscle cell and becomes hypertrophied
What is an example of a parasite that causes neoplasia
Spirocera lupi causes esophageal sarcoma
What are three common examples of parasites that interfere with host nutrition
Ascaris suum, dibothriocephalus latus, and giardia
How does ascaris suum interfere with host nutrition
Ingestion of chyme
How does dibothriocephalus Altus interfere with host nutrition
Absorption of vitamins- B12 (anemia)
How does giardia interfere with host nutrition
Causes damage to microvilli and surrounding tissue causing decreased absorption of nutrients
What is a common toxin released by plasmodium (malaria)
Hemozoin
What is hemozoin
Crystallized dimmers of heme that impair macrophage phagocytic function
What is parasite induced immunopathology
Damage that occurs as a result of an inappropriate immune response to infection or infestation
What is an example of parasite induced immunopathology
Flea allergy dermatitis- hypersensitivity to allergens in flea saliva
Behavioral changes can ____transmission of parasites in taenia multiceps to canids
Facilitate
What is the definitive host for Taenia multiceps (tapeworm) and where is it found
Canids- found in gut
What is the intermediate host for taenia multiceps (tapeworm)
Sheep; other ruminants
What does taenia multiceps (tapeworm) cause in sheep
Larva migrate to sheep brain and cause “gid”—> ataxia, circling
How is taenia multiceps transmitted from sheep to canids
Sheep that are infected and become ataxic are easy prey for canids and transmission is facilitated upon ingestion
Behavioral changes are ____ of infection in oestrus Ovis in sheep
Side effects
**unlike taenia multiceps which causes ataxia in sheep making them easy targets therefore their behavioral changes make them easy targets for canids and transmission occurs*
What is oestrus ovis
Sheep nasal botfly
How is oestrus ovis transmitted to sheep
Adult flies deposit bot egg in sinus and larvae then infect nasal and paranasal sinuses
Oestrus ovis rarely migrates to brain to cause behavioral changes like taenia multiceps but if it does why does it not facilitate transmission
Although they are easy prey, the botflies die and therefore aren’t transmitted to predator
What are virulence factors
Traits that confer pathogenicity
How does hemozoin produced by plasmodium spp. (malaria) act as a virulence factor
Hemozoin inhibits phagocytic effect of macrophages therefore allowing plasmodium to survive
What does leishmania spp. use as virulence factor and how does that work
Proteases, causes tissue invasion, survival in macrophages, and immune modulation
What virulence factor is used by toxoplasma gondii and how does that work
Kinases- disrupt host cell signaling and cause immunomodulation
Are Plasmodium spp., Leishmania spp., and Toxoplasma gondii parasitic Protozoa or metazoan parasites
Parasitic Protozoa
What virulence factor do nematodes, tapeworms and trematodes take advantage of and how does that work
Proteases- tissue invasion and immune modulation
What virulence factordo ticks, mosquitoes and other ectoparasites take advantage of and how does that work
Proteases- diminish pain at bite wound
What virulence factor do blood-feeding helminths and ectoparasites use
Anticoagulants
What do helminths secrete to act as virulence factors and cause immune modulation
Proteins, glycoproteins, peptides, glycine, glycolipids, eicosanoids that function in immune modulation by the parasite (downregulate immune response)
Which age groups are most at risk for parasitic disease
Young and geriatric
Are males or females more likely to carry parasite
Males- because of androgens
What females are more susceptible to parasitic disease
Pregnant, postpartum and lactating females
How does nutrition impact likelihood of getting parasitic disease
Malnourishment causes decreased resistance and resilience, increasing likelihood
How does immunological competency impact likelihood of getting parasitic disease (4)
- Immunodeficiency vs immunocompetent
- Prior exposure gives partial immunity—> reduced number, migration, development and reproduction
- Premunition- partial immunity due to chronic, low level infection, protects host against superinfection and more severe
- Immunization status
How does genotype contribute to likelihood of developing disease
Hosts resistance to infection has a genetic component
What factors influence pathogenic potential of a parasite (6)
- Predilection site
- Migratory pathway
- Sites of parasite development
- Feeding habits
- Immunopathology
- Transmission of other infectious agents
What does osteratagia ostertagi cause in cattle
Chronic abomastitis in young cattle
What is the predilection site of ostertagia ostertagi
Abomasum
What is the migratory pathway for ostertagia ostertagi
Local (within abomasum)
What is the site of development for ostertagia ostertagi
Gastric glands of abomasum
What are the feeding habits of ostertagia ostertagi
Adults feed on abomasal contents and epithelial tissue
What is the immunopathology of ostertagia ostertagi
Inflammation induced by larvae and adults
Is there transmission of other infectious agents for ostertagia ostertagi
No
Parasitic development of ostertagia ostertagi In the gastric glands of abomasum does what to parietal (pH) and chief cells (pepsin)
Erodes parietal and chief cells therefore increasing pH (parietal secretes HCl) and decreased pepsin
What is the consequence of ostertagia ostertagi larva in gastric glands of abomasum
Impaired protein digestion and bacterial overgrowth (no pepsin and less acidic)
This results in diarrhea
What do the ostertagia ostertagi Adults damage in gastric glands of abomasum
Epithelium
What is the consequence of ostertagia ostertagi Adults
Loss of serum proteins- leaking out and causing diarrhea due to osmotic effect
The immunopathology of ostertagia ostertagi Results in inflammation and causes what 4 things
- Further loss of parietal and chief cells
- Mucous neck cell hyperplasia
- Parietal and chief cells are replaced by mucous neck cells (metaplasia)
- Increased vascular permeability, loss of serum proteins, diarrhea
In ostertagia ostertagi Parietal cells are replaced by mucous neck cells, what is this an example of
Metaplasia- parasite replaces cell types
**other example was trichniella spiralis in skeletal muscle
Overall ostertagia ostertagi Results in what 3 things
- Impaired protein digestion
- Bacterial overgrowth
- Diarrhea
