Parasitology Test 1 Flashcards
Parasitology is largely a study of____
symbiosis
Any organism spending a portion of all of its life intimately associated with another organism of a different species is known as a ___
symbiont
What are the 4 cateogires of symbiosis?
- Phoresis
- Commensalism
- Mutualism
- Parasitism
What is phoresis?
When 2 symbionts travel together but NEITHER is physiologically dependent on the other
In a phoresis, the host carries a smaller symbiont known as a __
phoront
What is commensalism?
When one symbiont (commensal) benefits from its relationship with host and the host doesn’t benefit or get harmed.
What is a big similarity between commensalism and phoresis?
Neither organism in symbiotic relationship is dependent on the other and CAN survive independently.
What is mutualism?
Both partners in symbiotic relationship are called mutuals and both benefit from the association. Both organisms DEPEND on each other physiologically. Mutuals CANNOT survive without eachother.
What is parasitism?
When symbiont harms its host or in some sense lives at the expense of the host; parasite is usually smaller than host and physiologically dependent on host.
Most parasites are considered___, as they are physiologically dependent upon host and usually cannot survive if kept isolated.
Obligate
What is a facultative parasite?
Not common, free living or not normally parasitic, but becomes so occasionally when accidentally eaten or encountered.
When a parasite enters or attaches to body of host different from its normal host, it is called an ___ or ___
accidental or incidental parasite
What is an ectoparasite?
If parasite lives on the surface of its host or superficially embedded in the body surface
What is an endoparasite?
If the parasite lives internally (alimentary tract, liver, lungs, urinary bladder)
What are the 3 types of host?
- Definitive host
- Intermediate host
- Paratenic host
Define a definitive host?
If the parasite attains sexual maturity and reproduces within host
Define intermediate host?
Some development of the parasite occurrs but in which it does not reach maturity
What is a paratenic?
A paratenic or transfer host is not required for the completion of the parasites life cycle but is utilized as a temporary refuge and a vehicle for reaching the definitive host in the cycle.
What is a reservoir host?
Infected animal that serves as a source of parasites for humans
A wild animal in the role of reservoir host is called a ____
sylvatic reservoir host
A disease of humans caused by pathogenic parasite found in wild and domestic vertebrate animals.
Zoonosis
Anything such as a invertebrate, vertebrate, or disease causing agent like water and air is a _
vector
A parasite that hosts other parasites example: protozoan plasmodium in a mosquito
Hyperparasitism
what does heterotrophic mean? How does it relate to parasites?
Parasites require energy in existing organic molecules and nitrogen in the form of amino acids
What is a coelozoic parasite? Give the major example
parasite that resides within lumen of intestine or hollow organs
example: flukes, tapeworms
What is a histozoic parasite? example?
- parasite that lives within tissues
example: some protozoans and nematodes
What are features of R-selection? (there’s 4)
- high fecundity
- high mortality
- short life-span
- effective dispersal mechanism
What type of environment and population does R-selection favor?
- R selection prevails when selective forces upon organisms are UNSTABLE
- R-selection favors population sizes that are BELOW the carrying capacity of the environment
Give an example of a parasite that is an r-strategist
Any trematode; their environment is HIGHLY VARIABLE with 2 or more different hosts, plus 2 free-swimming stages in water to complete their life-cycle
Most parasites are ___strategist
R-strategist, R-selection
When does K-selection or k-strategist parasites prevail? What sort of conditions?
K-selection prevails when selective forces upon the organisms are RELATIVELY STABLE over a period of time
What are features of K-selection? (there’s 4)
- low fecundity
- low mortality
- longer life-spans
What type of environment and population does K-selection or K-strategist parasites prefer?
-RELATIVELY STABLE population sizes that are CONSTANT over time and are usually below the carrying capacity of the environment
What is an example of a K-strategist parasite?
Free living flatworm
What are the two types of parasitic competition?
- Exploitation
- Interference
Describe the exploitation style of parasitic competition
-joint exploitation of a limiting resource within a host species by 2 or more parasite species
Give example of exploitation competition style
Ascaris and Trichuris may coexist
Describe Interference style of parasitic competition
Antagonistic or hostile mechanisms are used by one species to reduce survival of another or to displace it from a preferred site of attachment, probably caused by production of toxins
What is prevalence?
(%) number of host individuals infected by 1 parasite DIVIDED by # hosts examined
example: 1 person in a group of 5 who were examined was infected, the prevalence would be 20%
What is intensity?
Number of parasites in a single infected host
What is mean intensity?
-average of the number of parasites in infected parasites
What is incidence?
(%) # of new cases of a disease or infection appearing in a population within a given period of time DIVIDED by # of uninfected individuals in the population at the beginning of time period
What is density?
(abundance) # of individuals of a particular parasite per unit are, volume, or weight of infected host tissue or organ
What is infrapopulation?
all of the parasites of a particular species in the body of a single host
What is suprapopulation?
all individuals of a species of parasite in all stages of development within all hosts in an ecosystem
what is epidemiology?
The study of factors responsible for the transmission and distribution of disease
What are the 7 factors that influence epidemiology?
- age
- sex
- social (cultural) and economic status
- diet
- distribution and presence of vectors and reservoir hosts
- host specificity
- densities of host and parasite
Means of transmission of parasite from one host to another
Vector
What organizations monitor epidemiology world wide?
- World Health Organization (WHO)
- Tropical Disease Research Program (TDR)
How did ectoparasites evolve, give example to support this theory?
May have evoloved from non-parasitic omnivores,
Example: Moth in South East Asia that feeds on plant juices, but 1 species sucks tears from orbits of large mammals
How did endoparasites evolve, give an example to support this theory?
Probably found entrance through alimentary tract.
Example: Cyst-forming protozoa and nematodes protected by a tough cuticle most readily survived actions of gastric juices.
What happens as a parasite becomes progressively more specialized?
-It limits its potential host species; increases host specificity
Why study host parasite interactions?
Without knowing the biochemical differences, new chemotherapeutic drugs may not emerge or effective vaccines may not be produced
____is the ability of the host to withstand a parasitic infection and may develop in several ways
Resistance
Host defense mechanisms can be divided into what 3 groups?
- barrier
- constitutive
- inducible
___may result from presence of some physical/chemical barrier that prevents the parasite from penetrating/migrating in the host
Barrier Defense
What are the 4 types of defense barriers
- Anatomic
- Physiologic
- Endocytosis/phagocytosis
- Inflammatory responses
Anatomic barriers include_
- skin and mucus membranes; ciliated epithelial cells in respiratory and GI tracts
- saliva,tears, mucus secretions
Physiologic Barriers include__
temperature, pH, oxygen, Lysozymes
Endocytosis/Phagocytosis barriers include:
-non-specific cellular activities
Inflammatory response barriers include:
-Vasodilation and increased capillary permeability with resulting migration of phagocytic cells
What are constitutive defenses?
Defenses found in all healthy animals; they provide general protection against invasion, colonization, infection caused by pathogens. Nonspecific, directed toward general defense; may not be sufficient to protect the host against pathogens
What are inducible defenses?
Defense mechanisms that must be induced or turned on by host exposed to a pathogen during infection. They are not immediately available until after the host is appropriately exposed to the parasite. Very specific against an invading pathogen
__means the ability to resist infectious disease
Immune
___means relative state of resistance of the host to a specific pathogen
Immunity
Inducible defenses are functions of the immune system and the immune response and take time to develop. The type of resistance developed is called
acquired immunity
What are the two types of acquired immunity?
- Active Immunity
- Passive Immunity
Host undergoes an immunological response and produces cells/factors responsible for the immunity. This immunity can persist a long time in the host, up to many years in humans
Active Immunity
Host acquires immune factors which were produced in another animal; Passive immunity is typically short-lived and usually persists only a few weeks or months
Passive Immunity
Chemical substances that stimulates the immune system in animals
Antigens
A protein synthesized by WBC in response to a foreign substance
Antibody
What is molecular mimicry?
Parasite produces host-like molecules on its body surface or its surface becomes covered with host molecules so that the host accepts parasite as its own
Give an example of parasite that does molecular mimicry
Schistosoma
How does trypanosoma avoid host immune system
Trypanosoma expresses new version of glycoprotein coat called VSG (Variant surface glycoprotein) of >1000 VSG genes, only 1 is expressed at a time
How do plasmodium avoid host immune system? (2 ways)
- Plasmodium synthesize proteins that appear on RBC’s surface, causes anchoring of RBC’s to walls of blood vessels so they won’t be swept into and destroyed by host spleen
- Plasmodium periodically alters composition of surface proteins so they are no longer recognized by current crop of antibodies
How do flukes increase chance of attaching to definitive host?
Alter behavior of intermediate host in ways that increase chances of moving on to new definitive hose (increase snail movement that will attract birds attention)
How do parasites harm hosts?
- mechanical injury, boring holes inside the host
- deriving nutritive substances as blood, lymph, cytoplasm, or digesting and absorbing its tissue and hosts digested food
- poisoning host with toxic metabolic products
- MOST PARASITES INFLICT COMBINATION OF ALL CONDITIONS ON THE HOST
What is verminous intoxication? What are the symptoms?
- Verminous intoxication is the poisoning of the host with parasites waste products
- Symptoms: An infected individual may feel bloated, tired, hungry, have allergies, gas, unclear thinking
What are 2 main factors that influence disease from parasite?
- Number of parasites
- Hosts physiological condition
What are the 3 types of histopathological damage that occur in parasite injured tissues?
- Necrosis
- Fatty degeneration
- Albumin degeneration
____is the degeneration and death of cells or tissue from infection
Necrosis
Give example of parasite that causes necrosis
Trichinella spiralis larvae in mammalian muscle cause tissue necrosis
Entamoeba_______ of host’s intestine
lyse the epithelial cell lining of hosts intestine
__results in deposition of abnormal amounts of fat in cells. Imparts a yellowish color to the cells and is common among parasite-laden liver cells
Fatty degeneration
Give example of parasite that damages host tissue by means of fatty degeneration?
Plasmodium that cause malaria
_____condition results in swollen cells packed with albumin/fatty granules, indistinct nuclei, and pale cytoplasm. Affects liver, heart, muscle, kidneys, etc.
Albuminous degeneration
What are 4 types of tissue transformation that occur in parasite injured tissues?
- Hyperplasia
- Neoplasia
- Hypertrophy
- Metaplasia
What is hyperplasia?
-Body repair activity follows shortly after parasitic infection and results in inflammation
Give example of parasite that damages host tissue by hyperplasia?
Liver fluke Fasciola promotes bile duct’s thickening via excessive division of the duct’s epithelial cells
What is hypertrophy?
-An increase in cell or organ size due to presence of intracellular parasites
Give example of parasite that damages host tissue via hypertrophy
-Plasmodium causes enlargement of host’s parasitized red blood cells and spleen
What is metaplasia?
-Tissue conversion from 1 type to another
Give example of parasite that damages host tissue via metaplasia
Lung fluke paragonimus converts lung tissue into fibroblasts
What is neoplasia?
-refers to abnormal cell growth in tissue, forming new structures (TUMORS AHHHHH) tumor remains benign if localized with no invasion of adjacent tissues. Becomes malignant if invades adjacent tissues or spreads to other parts of body through the blood or lymph
Give example of parasite that harms host via neoplasia
Schistosoma may cause cancer of urinary bladder
What is the phyla of parasitic protozoa called?
P. Sarcomastigophora
What subphyla contains amoeba?
Sarcodina (amoeba)
What class of Platyhelminthes (flatworms) are parasitic?
Classes Trematoda and Cestoda
What is the term for the attachment organ of Cestoda (Tapeworm)
Scolex
What 7 species of amoeba are known to parasitize humans?
-Entamoeba histolytica
-Entamobea hartmanni
-Entamoeba coli
-Entamoeba polecki
Entamobea gingivalis
-Endolimax nana
-Iodamoeba butschlii
blunt ended pseudopodia of amoeba
lobopod
thread-like pseudopodia found in some amoeba
filopodia
___may be found distributed in the cytoplasm of some trophozoites, represents RNA, including ribosomes
helical bodies
Helical bodies clump up and become ____ in cysts
chromatoidal bars
How are chromatoidal bars shaped in E. histolytica?
Smooth rounded ends in E. hystolytica
How are chromatoidal bars shaped in E. Coli?
Pointed ends in E. coli
Who discovered E. hystolytica? how? when? where?
First discovered by D. F. Losch in St. Petersburg Russia in 1875, he infected dog with amoebas found in stool of young individual. Dissected dead dog and human and both revealed identical ulcers in intestinal mucosa of colon
What are the successive stages that occur in life cycle of Entamoeba histolytica?
trophozoites -> precyst -> cyst -> metacystic trophozoite
What gives rise to amoebic dysentery during infection with E. hystolytica?
Ulceration of intestinal wall
What is size range of trophozoites of entamoeba histolytica?
20-30 micrometers in diameter
What causes amoeba E. hystolytica to go from trophozoite -> precyst?
trophozoite amoebas are carried along when stool formation is in process, as fecal matter passes posteriorly and becomes dehydrate it is stimulated to encyst by extruding food vacuoles, shrink in size, and condense into sphere (precyst)
What are symptoms of acute intestinal amoebiasis?
-cramps, vomiting, headache, general weakness, liquid feces comprised of bloody mucus and 15-50 stools passed a day
What are symptoms of chronic amoebiasis?
continuous attacks of diarrhea with intervening periods of milder intestinal problems
Why is hepatic amoebiasis the most serious form of amoebiasis?
Abscesses formed may rupture the abdominal wall or extend through the diaphragm into the lungs, conditions are always fatal
How do you diagnose amoebiasis?
- microscopic fecal preparations and identification of trophozoites or cysts
- serological test to detect possible tissue invasions
- X-ray scans may reveal abscess of the liver
What are treatment reccomendations you would give for someone with amoebiasis?
- chemotherapy to destroy trophozoites and relieve symptoms
- prescribe metronidazole because of its efficiency and minimal side effects
- lots of rest and bland diet
How big are E. hartmanni cyst and trophozoite?
trophozoite: 12-15 micrometer
cyst: 5-9 micrometer
What entamoeba looks identical to E. hystolytica but is “smaller race” and non-pathogenic
Entamoeba hartmanni
What is the best way to identify E. coli?
It is very large, trophozoite diameter is 25 micrometer average and range of 15-40 micrometer
and cysts have 8 vesicular nuclei and chromatoidal bodies are splintered, also very large cysts 10-33 micrometers 17 average
Which amoeba is a parasite of pigs and monkeys but occasionally infects humans?
Entamoeba polecki
What is a good way to identify E. polecki?
- cyst only has 1 nucleus
- cysts range 9-18 micrometers and measure 11-15 micrometers
What does Iodamoeba infect normally?
Pigs and primates
How do you identify Iodamoeba buetschlii cysts?
Uninucleate with large vacuole containing glycogen
How do you contract Naegleria fowleri?
Throguh swimming in waer containing flagellated free living naegleria fowleri. They enter host through nasal passages
How do you diagnose PAM from naegleria fowleri?
Requires ID of motile amoebic trophozoite via microscope examination of fresh CSF fluid
How do you treat PAM from Naegleria fowleri?
Use drugs qinghausu and Amphotericin, somewhat work but usually identified during autopsy
How can you tell the difference between Acanthamoeba and Naegleria fowleri?
- Acanthamoeba doesn’t have flagellated trophozoite stage
- Naegleria pseudopod is single lobose pseudopod, moves rapidly. Acanthamoeba forms small spiky spine like filopods moves slowly
How large are Acanthamoeba?
25-40 micrometers
How do you treat someone suffering from chronic PAM from Acanthamoeba infection
sulfonamides have favorable responses
How do you contract Acanthamoeba?
Many victims contract through contact lenses and found to use home-made saline washes containing live Acanthamoeba
What is the only ciliate that infects humans, sometimes monkeys rats, and pigs ?
Balantidium coli
Describe B. coli trophozoites.
- inhabit caecum and colon of humans
- oblong/spherical
- measure 50-130 micrometers length and 20-70 micrometer length wide
- micronucleus and kidney shaped macronucleus
- yellowish greenish color
What is the largest protozoan parasite of humans?
B. coli
How does transmission by B. coli occur?
accomplished via round cysts measuring 40-60 micrometers
- encystation occurs in large intestine
- usually occurs through feces contact of pigs
How do you diagnose B. coli infection?
- clinically indistinguishable from Amoebic dysentery
- easy to diagnose by finding large, spherical cysts (40-60 micrometers in diameter) in host fecal preparation
How do you treat B. coli infection?
use metronidazole or oxytetracycline. Treatment depends on extent of infection and clinical symptoms last about 10 days
