Final; Parasites Flashcards
Parasitic diseases are among the most prevalent diseases where
in developing countries
Parasitic infection is distinct from what
parasitic disease
What is parasitic disease a consequence of
porlonged, repeated, or high burden infection; usually subacute or chronic, rarely fatal (although there are exceptions)
Many parasitic infections are what
zoonosis; agents that infect animals
Many human parasites require what to complete their life cycles
human and nonhuman hosts; humans are dead-end hosts
What are the two types of parasites
protozoa (single cell)
helminths (multi-cell)
Disease is a consequence if parasite what is too high
replication; only a small amount is required to initiate infection
These are motile via flagella, parasitic form don’t have mito or golgi, most form cysts and are free living and solitary
mastiogophora
This caused an infection in Milwaukee via the drinking water
crytosporidum
These are mostly not motile, produce sporozoites which are important in transmission of infections, the entire group is parasitic
apicomplexa
These are multicellular animals including roundworms, and flatworms, and are extracelluar protected by a cuticle
helminths (worms)
In this type of host, the developmental stages take place out side of the host and in the host, the organism reaches maturity
definitive host
This type of host is required for replication
intermediate host
This is a non-infected asymptomatic carrier, not partaking in transmission
reservoir
Most helminths cause what in humans
chronic infections that are tolerated by the human host
This is NOT a consequence of parasitic replication
disease
This is due to the number of parasites that the host initially acquired from the environment
parasitic burden
How are parasitic infection resolved
not by most response, they spontaneously resolve when adult worm reaches senescence
What are the major groups of parasitic helminths
flatworms
roundworms (nematodes)
What are the subdivisions of flatworms
cestodes
trematodes
What are the majority of parasitic vectors
arthropods; involved in key parasitic life stages
Parasitic prevalence is dependent on what
local conditions favoring vector breeding
What can be examples of reservoirs
humans
animals
environment (soil contaminated with parasitized feces)
*How can the parasite gain entry
oral ingestion
penetration of the skin (unbroken)
arthropod0borne
*This type of parasitic entry involves ascariasis and amebiasis
oral ingestion
*This type of parasitic entry involves hookworms and schistosomes
penetration of the skin (unbroken)
*This type of parasitic entry involves bite wounds (malaria) and blood transfusions possibly
arthropod-borne
What is key to parasitic transmission
its dependent on parasitic life cycle and presence or absence of intermediate hosts; schistosomiasis required snails, they are not present in the US or Europe, therefore no schisto there
Disease manifestation of parasites is dependent on what
the size of the inoculum (and it varies for different parasites)
amoebiasis; large inoculum
crypto; few cysts
How are blood flukes able to evade the human antibody and cell mediated immune response
host plasma protein coasints
How are trypanosomes able to evade the human antibody and cell mediated immune response
surface antigen variation
How are leishmania able to evade the human antibody and cell mediated immune response
superoxide dismutase secretion
The life cycle of some parasites is determined by what
the species and tissue tropism
duffy factor antigen required for malaria and many black africans don’t have it = resistance
These type of changes can induce stage-specific transitions
temperature; some parasites only like certain temperatures, dictating where they live
Clinical damage due to parasites may be due to what
tissue damage
effect of host response
- may occur years after initial infection
This disease is caused by a trypanosomiasis and is transmitted via the kissing bug and found only in the americas
chagas disease
What are the symptoms of chagas disease
skin lesion
swollen eyelid
chronic infections = irreversible damage to organs
Eradication of chagas disease is only successful when one or more of these treatments are employed
chemoprophylaxis; preventative drugs
immunization
field control measures
Why is it difficult to immunize against parasites
many parasites coat themselves in host antigens
some rearrange their surface antigens
different proteins are displayed at different life cycles
This is the most important blood cell parasitic disease
malaria; most important of protozoan diseases
How many of the 156 names plasmodium protozoa are known to infect humans
4
Infection and subsequent development of malaria is driven by what in the US
travel
What is the only reservoir for plasmodia that can infect humans
infected humans
How do plasmodia infected humans transmit malaria
imported to new regions
induced via blood transfusions etc.
How is plasmodium spread in humans
sporocytes enter via mosquito bite and travels to liver
leave liver as merozoites
multiply in live and RBCs
How does malaria induce damage
paroxysm; simultaneous lysis of many RBCs and release of large number of merozoites
What can genetically predispose someone to be resistant to malaria
duffy blood group
sickle cell anemia
heterozygous individuals are carries
This drug targets the parasites food vacuole where hemoglobin is degraded, killing the parasite, but now, many parasites are resistant
chloroquine
This destroys RBCs and is endemic in the US and is transmitted the same as lyme disease
babesia
What is the life cycle of babesia
merozoites injected under skin by tick RBCs invaded no liver intermediate stage lyses RBCs ticks feed on infected RBCs to keep cycle
This is a common infection in humans, but disease is rare and it survives in macrophages
toxoplamsa
How is toxoplasmosis transmitted
consumption of inadequate cooked meat or food contaminated with cat feces
cyst penetrates the intestinal all and enters the blood stream
What does toxoplasma affect
can cause miscarriage
affects the amygdala in rats
may be linked to schizophrenia in humans
humans are 3 times more likely to die in a car crash
These are small protozoans transmitted by sandflies (middle east) which are rare in NA and Europe and has reservoirs in rodents, dogs, other animals, and humans
leishmania
What is the life cycle of leishmania
promastigote (flagellated) binds to macrophage and converts to amastigote (no flagella)
This causes african sleeping sickness and is transmitted via the tsetse flie
trypanosoma brucei
What are the reservoirs for african sleeping sickness
east africa; wild game
west africa; humans and domestic animals
What illness is caused by trypanosomes (african sleeping sickness)
systemic and chronic in blood stream
How does trypanosomes escape host immune detection
changing the dominant surface antigen
can infect for months and years
What is significant about the intestinal and vaginal protozoa
its varied based upon motility and replication
This has worldwide zoonosis with highly resistant cysts and is transmitted via ingestion of water contaminated by feces from animal carriers
giardia lamblia
What are the symptoms of giardia lamblia
intestional protozoan
mild, persistant diarrhea
do not invade; inflammation
This is a common vaginal flagellate, can cause vaginitis, can be transmitted via sex
trichomonas vaginalis
This is an amoebiasis, causes destruction of host tissue (colon), transmitted via fecal-oral, and may humans carry non-pathogenic amoebas
entamoeba histolytica
Hows does entamoeba histolytic invade and cause damage
adheres to cell receptors containing digalactose residues and kills on contact via pore forming proteins
What is required to eradicate entamoeba histolytica
cell mediated immunity; circulating antibodies not important
This is spread via zoonosis often in rural areas but also person to person via crowded urban environments
cryptosporidium
How is cryptosporidium spread
infectious oocytes produced in intestine and spread to other animals
does not invade intestinal epithelial or disseminate
This the most frequent intestinal helminth infection (south US)
ascaris
These intestinal helminths are common in temperate and tropical areas and prevalent in small children and institutions
pinworms
These eggs do not require maturation outside the body and are transmitted via fecal-oral, hatch in SI cause peri-anal itching
enterobius
What is the life cycle of a pinworm
person swallows egg eggs hatch in intestine larve mature to adult in a month mating females deposit eggs in anus anal scratching spreads eggs to others
These penetrate the skin as filariform larvae via soil contemned with stool
hookworms
What specific condition will lessen the chances of being infected via a hookworm
asthma
hookworms are able to reduce what
allergic reactions
How is the life cycle of the hookworm maintained
move from skin to heart then to lung then are either coughed or swallowed; can cause chronic anemia
These intestinal helminths perforate the intestinal wall producing septicemia and can reinfect the same host; especially in the immunocompromised
strongyloides stercoralis
These are long ribbon-like worms that can penetrate deep tissue and from infective cystic larvae and is acquired by eating raw or undercooked meat or fish
tapeworms
Who is the tapeworm life cycle
depended on humans and cattle, infection from eating feces or beef with larvae; all human create with consumption of undercooked/raw meat
Deep tissue infections of tapeworms produce what
severe diseases
cysticercosis
echinococcosis
With tissue and blood helminths what are the infections like
asymptomatic
encysted larva in striated/cardiac muscle
cysts calcify but worms viable for 30 years
How are tissue and blood helminths acquired
skin acquired each species (of schisto) has unique geographic distribution via snail intermediate host
How is schisto spread in the body
cercariae released from snails
burrow in skin of people with infected water
travel to blood and via portal venous system to mature
move in male/female pairs to the small/large intestine to reproduce
What does schisto eggs induce
formation of granulomas that undergo fibrosis that can produce disease symptoms years later
This is “river blindness” via black flies, elephantiasis via mosquitoes, and is not within the US due to geographic factors
filariasis
Where do filariasis larvae live
in subcutaneous tissues
