Lecture 20: Parasites Flashcards
a relationship where both organisms benefit
mutualism
commensalism
a relationship where one organism benefits while the other organism is not harmed
parasitism
a relationship where one organism benefits and causes harm to the other.
T or F: foodborne parasites are associated with large outbreaks
False; because they are endemic in many countries and so infections happen on a daily basis
what are cestodes (give just english meaning)
tapeworms
Taenia solium is a tapeworm associated with what animal
pork
tapeworm most associated with beef
taenia saginata
fish tapeworm
Diphyllobothrium latum
explain the microbial ecology of Taenia spp.
- eggs or gravid proglottids in feces and passed into environment
- cattle and pigs become infected by ingesting vegetation contaminated
- they hatch penetrate the intestinal wall and circulate in the musculature - oncosphere develop into cysterci in muscle
- humans are infected by ingesting raw or undercooked infected meat
- scolet attaches to intestine
- becomes this long gross tape like worm in small intestine
what is the difference between definitive and intermediate host
a definitive host = a parasite attains sexual maturity
intermediate host: a host in which a parasite passes one or more of its asexual stages, usually designated first and second, if there is more than one
describe the microbial ecology of T solium
- ingestion
- in the intestine the cysterci mature into adults attaching to the wall by their scolex.
- adult worms produce proglottids which become gravid; they may release eggs or detach from the tapeworms
- eggs or detached proglottids are passed from the host in feces
- pigs or humans are infected by ingesting embryonated eggs or gravid prog
- eggs develop into oncospheres, which penetrate the intestinal wall.
- oncospheres circulate to muscles and other organs and develop into cysticerci
explain the differences in t solium in humans as an intermediate or definitive host
There is more danger to human hosts if they are infected with T. solium as an intermediate host.
If humans acquire a T. solium infection from eating infected pork they become the definitive host where tape worms live in their intestine can reach 2-7 m in length
However, if humans ingest T. solium eggs from human excreta they become the intermediate host. If this happens, tapeworm segments may be passed from the intestine into the stomach where oncospheres (immature form of the parasite enclosed in an embryonic envelope) may hatch and migrate to the subcutaneous tissue, muscle, viscera or the CNS (cysticercosis).
what is cysticercosis
its when larvae penetrate the intestinal wall and disseminate into the bloodstream.
symptoms associated with cysticercosis
others will experience abdominal pain, nausea, bloating, diarrhea, weakness, weight loss, vitamin deficiencies and malnutrition. and if the cysts form in the brain (neurocysticercosis),
how does taenia survive in the intestine
hooks and suckers allow it to hold tightly to the wall of intestine. Its flat body gives it a large surface area to absorb nutrients. It has no need for a mouth or digestive tract as it absorbs already digested foods. It produces large number of eggs to increase chances of reaching another host.
It has both male and female sex organs so it fertilize itself
How to prevent tapeworm by
- cfia officers inspect meat in Canada before it is sold
- proper sewage disposal is important to prevent tapeworms from spreading
- cooking meat thoroughly
- freezing the meat at -10 deg C for 5-10 days
- treatment is available that causes tapeworm to let go of the intestinal wall and it gets flushed out with the feces.
- can still buy tapeworm eggs for weight loss
Microbial ecology of Echinococcus
- adult in small intestine
- embryonate egg in feces
- oncosphere hatches penetrates intestinal wall
- hydatid cyst in liver, lungs, etc
- protoscolex from cyst
- scolex attaches to intestine
echinococcus species require _____ mammalian hosts for completion of their lifecycles. explain
2; (definitive and intermediate hosts). The gravid proglottids (tapeworm segments containing eggs gravid proglottids) or free eggs are passed in the feces of the definitive host, a carnivore.
Eggs are ingested by intermediate hosts (many mammalian species), in which the larval stage (metacestodes) and infectious elements (protoscoleces) develop and cause cystic echinococcosis(CE)
The cycle is completed if an infected intermediate host is eaten by a suitable carnivore.
T or F: only one tape worm can be present within a human host
T
T or F: tapeworm eggs remain viable in the external environment only for a few hours
false; weeks to months
T or F: E granulosus of Echinococcus spp. can survive freezing temp
True
what is an oncosphere
larval form of a tapeworm, penetrate the intestinal mucosa and enter the bloodstream where they are distributed to the liver and other sites, where development of the cyst begins
The most common site for the development of hyatitid cysts are the;
liver (most common), followed by the lungs or spleen, kidney, heart, bone or CNS
E multilocularis cysts behave like ___
invasive cancer and are almost impossible to remove surgicallyt when detected late. 70% of untreated cases become fatal within 5 yrs.
name of fish tapeworm
Diphyllobothrium spp.
state the lifecycle-microbiology of diphyllobothrium
- unembryonated eggs passed in feces
- eggs embryonate in water
- coracidia hatch from eggs are ingested by crustaceans
- procercoid larvae in body cavity of crustaceans
- infected crustaceans ingested by small freshwater fish. Procercoid larva released from crustacean, develops into plerocercoid larva
- predator fish eats small fish
- human ingests that fish
- adults in small intestine
- proglottidis release immature eggs
The lifecycle of diphyllobothrium involves 2 ____ hosts and 1 ____ host
intermediate; definative
Immature diphyllobothrrium eggs are based in the feces of mammalian host and then consumed by a freshwater crustacean, where they develop into a
into a procercoid larvae
The infected crustacean is consumed by a suitable intermediate host there the larvae is released from the crustacean and migrate into the fish flesh, where they develop into
a plerocercoid larvae
The ___ larvae are infective for the definitive host
plerocercoid
what are some symptoms of diphyllobothriosis
diarrhea
- abdominal pain
- vomiting
- weight loss
- fatigue
- constipation
Fish tapeworm has a unique affinity for vitamin ____ and this can lead to what type of symptoms
- vitamin B12
- lead to pernicious anemia, chronic deficiency can damage the brain and nervous system.
how to prevent diphyllobothriosis
- cook fish thoroughly
- brine fish
- freeze at -10 for 24-48 houes
What are the 2 main nematodes
Trichinella and anisakis
reservoir hosts for trichinella
pigs, horses, bears and game animals
explain the microbial ecology of trichinella
- ingest the undercooked meat
- larvae released in small intestine
- adult in small intestine
- larva deposited in mucosa
- encysted larvae is striated in the muscle
Trichinella are maintained in nature either through ____ or ___ cycles
sylvatic or domestic
T or F: animals are generally asumptomatic with trichinella, and only humans show signs of clinical disease
T
the severity of trichinellosis is dependant upon what 3 factors
- the number of infected larvae ingested
- the species of trichinella
- the immune status of the human host
symptoms of trichinellosis
- fever
- headaches
- gastrointestinal upset
- muscle pain
- facial swelling
- skin rash
how is trichinella spp prevented
Surveillance:
The CFIA administers a Trichinella control program
Inspection of meat plants to ensure the destruction of Trichinella larvae (cooking, curing, freezing)
Prohibition to feed meat and meat by-products to swine
Consumer:
Proper cooking of meat. All wild game meat, pork and horse meat should be cooked to an internal temperature of at least 71°C
Curing (salting), drying, smoking or microwaving the meat does not consistently kill infective larvae
Freezing (at least -15 °C) for at least 3-4 weeks kills some Trichinella species but not all.
Wild game meat must be cooked thoroughly. The Trichinella species that typically infests wild game can resist freezing.
microbial ecology of anisakis
- marine mammals excreted unembryonated eggs
- eggs become embryonated in the water
2b. l2 larvae hatch from the eggs and free swim - free swimming larvae are ingested by crustaceans and they mature into l3 larvae
- infected crustaceans are eaten by bigger fish and squid, they migrate to muscles and upon predation infected from fish to fish
- fish and squid maintain L3 and are infective to humans and marine mammals – in humans if they eat this fish, they may show gastrointestinal issues
- when fish or squid containing L3 larvae are ingested by marine mammals, the larvae molt twice and develop into adult worms. adult worms may produce eggs that are shed in their feces
symptoms of anisakiasis
- abdominal pain
- nausea
- sometimes vomiting or diarrhea
- obstruction of the small intestine
what is a suitable treatment for anisakiasis
No recommended therapy other than removal of the larvae through surgery
If there is no obstruction, then surgical intervention can be avoided; the larvae will die within several weeks
anisakiasis spp. outbreaks are associated with what food product, most commonly
home made sushi
T or F: anisakiasis can be transmitted from human to human
F
how to prevent anisakiasis
- cook seafood to internal temp of 63 deg C
- freeze fish at -20degC for 7 days
- -35 deg C until solid and solid -35 deg C for 15 hours
- -35 deg C until solid and storing at -20 deg C for 24 hours
microbial ecology of T gondii
- definitive host (cat)
- oocysts are excreted in cat feces. contaminated soil is ingested by birds, mammals and humans
- bradyzoites encyst within the CNS and muscle of infected host
- tachyzoites infect all nucleated cells in the host, replicate and cause tissue damage
what are oocysts
are the zygotic stage of the life cycle, and are excreted from cat feces.
They sporulate in the environment in about 3 days
The ______ cycle occures when consumption of the oocysts results in the infection of the _____
asexual, intestine
when the intestine is infected with a T gondii cyst this results in the formation of a ___ and results in
tachyzoite. the tachyzoite multiply in the intestine until the cell ruptures and systemic infection results. Tachyzoites can infect new cells throughout the body including the cardiac muscle but the CNS is the most often affected.
____ can form in the tissue and if tissue is ingested by a felid then the sexual cycle can occur
bradyzoites
T gondii has a high prevelance amoung what population in Canada
the inuit populations in northern canada
T or F: T gondii oocysts have the potential to remain viable in the soil for several years
True
- cause acute toxoplasmosis
- invade all nucleated cells and occur in groups
- rapid multiplication and lyses cells
tachyzoites
what are some characteristics of bradyzoites
- cause latent toxoplasmosis
- tissue cysts that contain slowly growing trophozoites known as bradyzoites
- most common in the brain, skeletal muscle and cardiac muscle
- remain for the life of the host
- recrudescence of infection in immunocompromised hosts.
acute toxoplasmosis
caused by the invasion of tachyzoites. the majority of cases are asymptomatic
mild fever, sore muscles, swollen glands and lymph nodes.
cerebral toxoplasmosis
immunocompromized individuals are at greater risk. bradyzoites can transform
ocular toxoplasmosis
infection in young children or immunosuppressed individuals commonly results in damage to the eyes.
ocular symptoms include: strabismus, retinochoroiditis, inactive retinal scarring , panuveitis, uveitis and neuroetinitis
congenital toxoplasmosis may affect what population? what affects may this have?
pregnant women; fetus are at risk if the mother acquires the infection during pregnancy. this may lead to spontaneous abortion, still born or a child that is physically-mentally disabled.
name 2 foods that have been linked to T gondii outbreaks
rare hamburger, rare lamb, raw goats milk
how is T gondii infection acquired
- eating raw of undercooked meat of infected animals
- consuming food or water with cat feces
- contaminated environmental samples
- blood transfusions or organ transplantation
- mother to fetus
environmental microbiology of cryptosporidium spp.
infective phase, diagnostic phase, release of sporulated oocysts in the environment, contamination of food water and persons
what are the possible roots of contamination for cryptosporidium
water borne, person to person, foodborne, zoonotic
most important route of transmission for cryptosporidiosis
waterborne
Why may cryptosporidiosis survive in waterparks
resistant to chlorine and most disinfectant agents
how to prevent cryptosporidiosis
wash F&V avoid swallowing recreational water avoid drinking untreated water avoid unpasteurized fruit juices or milk wash hands after contact with farm animals
T or F: giardiasis is major diarheal diseased found throught the world and the most commonly identified intestinal parasite in the US
T
Giardiasis infections may last about _____
6-8 weeks but symtpms like lactose intolerance can persist after the infection clears up
