20 - Parasites Flashcards
Mutualism:
Commensalism:
Parasitism:
- a relationship were both organisms benefit
- a relationship where one organism benefits while the other organism is not harmed
- a relationship where one organism benefits and causes harm to the other organism
T or F: Globally parasites are very common and it is estimated that more than 2 billion people are infected with foodborne parasites worldwide
T
T or F: Foodborne parasites don’t tend to be associated with large outbreaks, but are endemic in most countries, and infections happen on a daily basis
T
Many parasitic infections remain ___________ for weeks, months or even years
asymptomatic
Cestodes (Tapeworms) include:
- Taenia (pork and beef)
- Echinococcus
- Dyphyllobothrium (fish)
___________: a host in which a parasite attains sexual maturity
definitive
______________: a host in which a parasite passes one or more of its asexual stages: usually designated first and second, if there’s more than one
intermediate
What are the 2 options/ 2 microbial ecology cycles associates with Taenia spp.
First option (humans = definitive host) :
1) Oncospheres develop in the muscles tissuesof pigs and cows
2) Humans eat the pig or the cow (undercook)
3) Replication in our GI tract (scolex attaches to intestine and grow)
4) When they reach sexual stage in our GI tract, we excrete the eggs in our feces and pass them into the environment
5) If feces are not treated and are used as pasture, the cows or the pigs eat the eggs (eggs go into their GI tract and muscle)
Second option: (humans = intermediate host)
If we eat something contaminated with feces that has the eggs, we become the intermediate hosts instead
T or F: There is more danger to human hosts if they are infected with T.solium as an intermediate host
T
If humans acquire T.solium infection from eating infected pork they become the ______________ where tape worms live in their intestine can reach 2-7m in length
definitive
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 _______ where oncospheres (immature form of the parasite enclosed in an embryonic envelope) may hatch and _______ to the subcutaneous tissue, muscle, viscera or the CNS (cysticercosis).
stomach
migrate
______________ is when larvae penetrate the intestinal wall and disseminate into the bloodstream
Cysticercosis (50-100 million people worldwide)
T or F: Cysticercosis is a reportable disease in Canada
T
T or F: with cysticercosis, many individuals will show no symptoms, others will experience abdominal pain, nausea, bloating, diarrhea, weakness, weight loss, vitamin deficiencies, and malnutrition
T
If the cysts form in the brain (___________________) it may lead to headaches, confusion, seizures, epilepsy, and vision changes
neurocysticercosis
A person usually has ________ tapeworm living in the intestines
one
In Taenia spp. new segments are produced at the _____ and older segments are pushed to the back and grow ______
neck
larger
In Taenie spp. each proglottid is an _______________
hermaphrodite (it has both male and female sex organs) and can fertilize itself because only one tapeworm can be present within a human host
Eggs of Taenia spp. remain viable in the external environment for ______ to ________
weeks to months
Adult tapeworms can live up to _____ in the host’s intestine
25 years
T or F: Taenia spp. is endemic in Canada
F, but imported cases are seen
How do you prevent tapeworms?
- CFIA officers inspect meat in Canada before it is sold
- Proper sewage disposal is important to prevent tapeworms from spreading
- Cooking meat thoroughly
- Freezing meat at -10C for 5-10 days
- Treatment is available that causes tapeworm to let fo of the intestinal wall and it gets flushed out with feces
- Can still buy tapeworm eggs for weight loss but be careful
Echinococcus species require ________________ for completion of their lifecycles (definitive and intermediate hosts)
2 mammalian hosts
(In Echinococcus species) The _________________ or free eggs are passed in the feces of the definitive host, a carnivore
gravid proglottids
In echinococcus species, the cycle is completed if ____________________
an infected intermediate host is eaten by a suitable carnivore
Infection of humans is due to accidental ingestion of E.granulosus eggs passed into the environment with _____ from definitive host (dogs are the main sources)
feces
T or F: Eggs of E.granulosus are highly resistant to environmental conditions and can remain infective for many months (up to about 1 year in a moist environment at lower ranges of temperatures of about +4°C to +15°C).
T
Eggs of E.granulosus are sensitive to _________
desiccation (killed within 4 days at RH 25% and within 1 day for RH 0%
T or F: E.granulosus eggs can survive freezing temperatures but when heated to 60-80C the eggs are killed in less than 5 mins
T
An ______________- larval form of a tapeworm, penetrate the intestinal mucosa and enter the bloodstream where they are distributed to the _____ and other sites, where development of the cyst begins
oncosphere
liver
*The liver is the most common site (more than 65%) followed by lungs (25%), or spleen, kidneys, heart, bone, or CNS
Incubation period for oncosphere in Echinococcus is :
2-15 years
E.multilocularis cysts behave like _________ and are almost impossible to remove surgically when detected late, 70% of untreated cases become fatal within 5 years
invasive cancer
Human infection with E. granulosus or E. multilocularis has not yet been reported in ____________
Canada
The lifecyle of ________________ involves 2 intermediate hosts (zooplankton and fish) - especially species that move between fresh and salt water, and a definitive host (piscivorous mammals or birds)
Diphyllobothrium
________________. The disease is closely linked to the consumption of raw or undercooked freshwater or marine fish
Diphyllobothrium
Immature eggs are based in feces of mammalian host, and then consumed by a freshwater crustacean, where they develop into a ______________________.
The infected crustacean is consumed by a suitable second intermediate host, where the larvae is released from the crustacean and migrate into the fish’s flesh where they develop into a _____________________
procercoid larvae.
plerocercoid larvae
The ____________________ are infective for the definitive host including humans (diphyllobothrium)
plerocercoid larvae
Symptoms of Diphyllobothriosis are generally mild and can include:
- diarrhea
- abdominal pain
- vomiting
- weight loss
- fatigue
- constipation
*many cases are asymptomatic for years and the host can be infected for years before the parasite is detected
- The fish tapeworm has a unique affinity for vitamin B12
- The parasite can absorb 80% or more of the host’s vitamin B12 intake
- Vitamin B12 deficiency can lead to pernicious anemia
- Chronic b12 deficiency can damage the brain and nervous system
- The host needs to be infected for many years until neurological symptoms appear
Diphyllobothrium - Diphyllobothriosis
T or F: Fish that is thorougly cooked, brined or frozen at -10C for 24-48 hrs can be consumed without risk of D.lactum infection
T
Nematodes (_____________-)
roundworms
Nematodes include __________ and __________
Trichinella spp. and Anisakis spp.
Trichinella are maintained in nature either through ___________ or _________ cycles
sylvatic (wild animals)
domestic
The ________ is widespread in nature, on all continents, and is maintained by cannibalism and scavenging in carnivorous or omnivorous animals
sylvatic
T or F: for Trichinella animals are generally asymptomatic, and only humans show signs of clinical disease
T
How do humans acquire Trichinella:
through the consumption of raw or undercooked meat from swine, bear, walrus, horse, badger, dog, cougar or turtles
How many types of Trichinella can be found in Canada?
2
T.Spiralis
T.nativa
Is Trichinellosis a reportable disease in Canada?
Yes
The severity of human trichinellosis is dependent upon the _____________________, the Species of Trichinella, and the immune status of the human host
number of infected larvae ingested
Symptoms which appear 5 to 15 days after exposure and which include: fever, GI upset, headache , muscle pain, facial swelling and skin rash is associated with __________
Trichinella
T or F: the acute phase of Trichinella can turn into a chronic phase
T
T or F: the CFIA administers a Trichinella control program
T
T or F: in Trichinella surveillance there is a prohibition to feed meat and meat by-products to swine
T
What can consumers do to prevent Trichinella spp.
- proper cooking of meat . All wild game meat, pork, and horse meat should be cooed to an internal temperature of at least 71C
- Curing (salting), drying, smoking or microwaving the meat does not consistently kill infective larvae
- Freezing (at least -15C) 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
What parasite is common in canadian waters:
Anisakis
Humans are incidental hosts in which parasite:
Anisakis
Humans become infected by eating raw or undercooked seafood, the parasite infection will clear up on its own:
Anisakis
Explain the microbial ecology of Anisakis spp.
1) Large marine mammals are the definitive hosts (dolphins, whales)
2) Excrete the unembryonated eggs
3) Eggs become embryonated in the water
4) Eggs are eaten by small crustaceans which are then eaten by larger fish
Anyone who eats raw or undercooked fish is potentially at risk of ________
Anisakis spp.
A. simplex larvae tend to penetrate the gastrointestinal wall, invading the _____________________
the abdominal cavity
Symptoms including abdominal pain, nausea, sometimes vomiting or diarrhea or obstruction of the small intestine correspond to :
Aniskakiasis
There is a high prevalence of Anisakis simplex in _______________
wild salmon
Can Anisakiasis be transmitted human to human?
No, and it is not reported
How can you prevent the presence of Anisakis?
- cook seafood to an internal temperature of at least 63C
- freeze the fish (-20 for 7 days for example)
Members of the family Felidae (wild and domestic cats) are the only known definitive hosts, while most species of warm blooded animals such (birds, mice, squirrels, rabbits, etc.) can be intermediate hosts
Toxoplasma gondii
_______________ are the zygotic stage of the life cycle, and are excreted from cat feces
Oocytes
The asexual cycle occurs when consumption of oocysts results in the infection of the intestine. This results in the formation of a _____________ in the intestine, which multiply until the cell ruptures and systemic infection results. ___________ can infect new cells throughout the body including the cardiac muscle, but the CNS is most often affected.
tachyzoites
________________ can form in the tissue, and if tissue is ingested by a felid then the sexual cycle can occur
bradyzoites
T or F: T. gondii infects all mammals and birds, and all tissues in each of them. It is also the most common human infections throughout the world
T
T or F: There’s a high prevalence of T. gondii in the Inuit populations of northern Canada
T
A high prevalence of T. gondii infection has been detected in France and Quebec due to _______________
a preference for eating raw or undercooked meat
_________ are the most important intermediate hosts in T. gondii
mice
T or F: cats shed oocysts for only 1-2 weeks following infection (only once in their life) and there shouldn’t be a problem if you change your cat litter box every 24 hours
T
T or F:
-oocysts have the potential
to remain viable in the soil for many years
-oocysts from cat feces can be washed into the water system
-T. gondii oocysts can sporulate in water and remain infectious in mice for up to 6 months
T
___________ cause acute Toxoplasmosis
Tachyzoites
Tachyzoites invade all ________________ and occur in groups
nucleated
Tachyzoites causes rapid __________ and _____ cells
multiplication
lyses
__________ are associated with latent Toxoplasmosis
Bradyzoites
Tissue cysts contain slowly growing trophozoites known as ___________
bradyzoites
Bradyzoites remain for the life of the host, there’s a recrudescence of infection in immunocompromised hosts and they are most common in ________, skeletal muscle and ________ muscle
brain
cardiac
Acute Toxoplasmosis:
- caused by invasion by ___________
- majority of cases are ___________
- mild fever, sore muscles swollen glands and lymph nodes
tachyzoites
asymptomatic
Cerebral toxoplasmosis:
- ______________ individuals are at greater risk
- ____________ can transform into tachyzoites and start propagating
immunocompromised
bradyzoites
Ocular Toxoplasmosis affects ___________ or immunocompromised individuals and results in damage to the eyes
young children
Congenital Toxoplasmosis occurs when ________
mother acquires the infection during pregnancy, the fetus is at greater risk
Congenital Toxoplasmosis may lead to _________ abortion, a still born, or a child that is physically or mentally severely disabled
spontaneous
T or F: The baby is only at risk if a women receives her first exposure to toxoplasmosis while pregnant
T
A women with no previous exposure to toxoplasmosis should avoid :
- eating and handling raw meat
- exposure to cat feces
- gardening
What is the most common defect in congenital toxoplasmosis:
-blindness
The risk of passing the infection to the unborn baby is greatest in the ______ trimester at 70%.
third
T or F: Severity of infection for the fetus is inversely related, causing the most severe effects in the first trimester and the least in the last trimester.
T
Why there are usually no outbreaks of T. gondii?
Because people are asymptomatic
How can humans become infected with T. gondii (what are the different routes)?
- eating raw or undercooked meat of infected animals
- consuming food or water contaminated with cat feces
- (Most common) by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat)
- blood transfusion or organ transplantation
- transplacentally from mother to fetus
What can you do to prevent T. gondii?
- wash hands and counter top thoroughly after preparing raw meat
- thoroughly cook meat
- wash and or peel fruits and vegetables
- clean litter box daily (it takes 1-5 days for the oocysts to sporulate and become infectious)
- feed cat commercial dry food, never raw meat (indoor cats can become infected this way)
- cover outdoor sandboxes
T or F: T. gondii can causes behavioral changes
T
What are the 2 Cryptosporidium species isolated from human cases and implicated in waterborne outbreak?
- C. hominis
- C. parvum
Thick-walled oocysts are associated with which parasite
Cryptosporidium
What parasite can you find in public pools?
Cryptosporidium
Routes of transmission for Cryptosporidium include:
- water-borne
- person-to-person
- zoonotic
- foodborne
T or F: for Cryptosporidium, oocysts are shed in the feces of the host and can survive for long periods under cool moist conditions
T
T or F: the waterborne route is numerically the most important means of transmission of cryptosporidiosis
T
Cryptosporidium is a ______________ and ____________ disease in Canada
waterborne and foodborne
Contamination of a water park and contamination of unpasteurized apple cider is associated with which parasite?
Cryptosporidium
_________ is primarily responsible for watery diarrhea that lasts for more than 30 days in 56 % if AIDS patients
C.parvum
Parasites such as ________________ and ________ are leading agents of chronic or persistent diarrhea worsened by specific risk factors such as malnutrition or immune deficiency
Cryptosporidium
Giardia
What does Cryptosporidiosis causes in healthy individuals?
- diarrhea
- abdominal pain
- weight loss
- nausea
- vomiting
- fever
- is self-limiting and usually lasts for 1-2 weeks
How can you prevent Cryptosporidiosis?
- use caution when traveling to countries where the water supply might be unsafe
- wash your hands after contact with farm animals
- avoid unpasteurized milk or fruit juices
- avoid drinking untreated water or treat water before drinking
- avoid swallowing recreational water
- wash raw fruits and vegetables before eating
T or F: Cryptosporidium is resistant to chlorine and most disinfectants
T
What is the life cycle of Giardia?
- The cysts is the infective stage
- Cysts can survive in water at 4C for at least 3 months
- 10 cysts are sufficient to infect humans
There are 7 genotypes in Giardia, they are classified in ______________
Assemblages A-G
*Assemblages A & B include humans
What parasite has a worldwide distribution, is a major diarrheal disease found throughout the world, is the most commonly identified intestinal parasite in the US and the most common protozoal intestinal parasite isolated worldwide
Giardia
T or F: there is a high prevalence for Giardia in dairy farms and beef farms
T
Some people can carry giardia parasites without experiencing any symptoms. Symptoms of giardiasis generally show up one or 2 weeks after exposure and symptoms include:
- greasy stools
- fatigue
- nausea
- weight loss
- vomiting
- loss of appetite
Giardiasis infections usually last about _________ weeks, but problems such as lactose intolerance can persist after the infection clears up.
six to eight
What animal is associated with Giardiasis?
-Beavers
T or F: Giardia is chlorine resistant
T
What can you do to prevent Giardia?
- Wash raw fruits and vegetables before eating
- Avoid swallowing recreational water
- Avoid drinking untreated water or treat water before drinking (boiling for 1 min is sufficient)
- Wash hands after handling soil or feces
- Use caution when traveling to countries where the water supply might be unsafe
Contamination of foods occurs through:
- contaminated water for irrigation
- application of manure or sewage to crop lands
- direct access to crops by wildlife and livestock
- contaminated equipment
- poor hygiene of infected food handlers / consumers
- cats contaminate crops and livestock feed and water
