Parasites Flashcards
What is the definition of Mutualism? Commensalism? Parasitism?
Mutualism: relationship where both organisms benefit
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 organism
What is the difference between a definitive host and an intermediate host?
Definitive host: a host in which a parasite attains sexual maturity
Intermediate host: a host which a parasite passes one or more of its
What is the definitive hsot and intermediate host of Taenia solium (pork tapeworm)?
Definitive host: Humans
Intermediate host: Cattle and pigs
What is the lifecycle of Taenia solium?
Eggs are excreted from host in feces → environment
Cattle and pigs eat, as as intermediate hosts
Oncosphere hatch and penetrate intestinal wall, circulate to muscle → develop in muscle
Humans infected by ingesting raw or undercooked infected meat
Scolex attaches to intestine
Adults in small intestine
What happens when humans are the intermediate host of Taenia?
Human consumes eggs from human feces and becomes the intermediate host
Tapeworms segments may be passed from the intestine into the stomach where oncospheres may hatch and migrate to the tissue, muscle, viscera or CNS
This results in more danger to the intermediate host human
How do humans become the definitive host for Taenia solium?
From eating infected pork, human become definitive host, tapeworms live int eh intestine, reach 2-7 m in length
What is the cause of Cysticercosis and what are the symptoms?
Cause is larvae that penetrates the intestinal wall and disseminated in the blood
Either no symptoms or abdominal pain
Cause cysts in brain → headaches, confusion, seizures, epiilepsy, vision changes
What about Taenia helps it bury into the intestine?
Hooks
What about Taenia helps it acquire nutrients?
Flat body for increased surface areas (no mouth)
What are 2 reasons that there is only one tapeworm that survives?
Hemaphrodite, can fetilize itself
Produces a lot of eggs but outcompetes with the other tapeworms until there is only one
What are the names for the eggs of Taenia solium eggs?
Proglottis → Gravids → release eggs or detach from tapeworm
How long do Taenia eggs survive? Adult tapeworms?
Eggs survive for weeks- months in the environment
Adult tapeworms can live up to 25 years
Why is it important to treat sewage for parasite even in non-endemic areas?
Because travellers can brings back these parasites and if they get into the water system ( through feces) they need to be treated to prevent infection
How do you prevent Taenia solium?
Inspect Cook thorouhgly Freezing at -1 for 5-10 days Proper sewage disposal Some used for weight loss
What are the definitive and intermediate shots of Echinococcus spp?
Definitive: dogs and carnivores (Ingest the cysts)
Intermediate: sheep, goats, swim etc ( ingest eggs)
Explain the cycle of Echinococcus spp, and how humans can get infected?
Definitive host: dogs and carnivores (ingests cysts)
Gravid proglottids (tapeworms segments containing eggs gravid proglottids) or free eggs passed in feces
Intermediate hosts: sheep, goats, swine, etc (ingests eggs)
Larval stage and infectious elements develop and cause cystic echinococcosis (CE)
Cycle complete if infected host is eaten by suitable carnivore
Human infection is accidental ingestion of eggs passed into the environment with feces from defintive hosts (dogs more of concern)
How do you get rid of Echinococcus eggs?
They are resistant to environmental conditions, a nd remian infective for months (up to a year in a moist environment at lower ranges)
Sensitive to dedication( <25% humidity)
Heating 60-80C will kill in less than 5 minutes
Can survive freezing temperatures
What is the infection like for Echinococcus? What are the disease aspects
An incosphere (larval form of a tapeworm) penetrate the intestinal mucosa and enters the bloodstream– liver/organs→ cyst development
Liver, lungs, spleen, kidneys, heart, bone, CNS
2-15 year incubation
E. multicularis cysts behave like invasive cancer and are almost impossible to remove surgically when detected late→ 70% of untreated cases become fatal within 5 years
What are the intermediate hosts and definitive host of Diphyllobothrium spp?
2 intermediate hosts: zooplankton and fish
1 definitive host: piscivorous mammals or birds
How are most infected with Diphyllobothrium?
Closely linked to consumption of raw or undercooked freshwater or marine fish
Explain the life cycle of Diphyllobothrium?
Adult tapeworms infect dogs, cats, bears, humans, seals and otters
Immature eggs are based in feces of mammalian host → consumed by fresh water crustacean→ procercoid larvae
Crusteacean is consumed by second suitable intermediate host (fish)–> plerocercoid larvae→ infectious for definitive host (humans)
Distribution: where raw fish is eaten
What are the common symptoms of Diphyllobothrium?
Symptoms (mild): diarrhea, abdominal pain, vomting, weight loss, fatigue, constipation
Vitamin B12 deficiency
Unique affinity for vitamin B12→ absorb 80% of hosts intake→ pernicious anemia
Chronic vitamin B12 can damage the brain and nervous system
Needs to be infected for mayn years until neurological symptoms appear
How do you prevent Diphyllobothrium?
Fish that is thoroughly cooked, brined, or frozen at -10C for 24-48 hours can be consumed without risk
What are the domestic and intermediate hosts of Trichinella spp?
Intermediate stage: pigs, bears
Definitive: pigs an bears, humans
What are the lifecycles of Trichinella spp?
Domestic (pigs due to meat scapes, cannibalism)
Sylvatic (Bears-predators/scavengers/cannibalism)
Mice also help with this
Larvae get eaten and bury into the SI then live in muscle
What are the symptoms?
Animals are symptomatic, only humans show signs of clinical disease
How do humans acquire the disease?
Consumption of raw or poorly cooked meat from bear, walrus, horse , badger, dog, cougar, turtles
What is Trichinellosis? What are the symptoms?
The infection fro Trichinella spp.
Symptoms appear 5-15 days after
Fever, GI upset, headaches, muscle pain, facial swelling, rash
Inflammation of heart and muscle and the brain, are serious
Acute phase could turn into a chronic phase
Very chronic, stays for years (up to 40)
How do you prevent Trichinella infections?
Surveillance
Control program
inspection of meat plants
Prohibition to feed meat and meat by products to swine
Consumer
Proper cooking of meat, all wild game meat, pork and horse should be cooked to internal 71C
Curing, drying, smoking, microwaving does not consistently kill infective larvae
Freezing for atleast 3-4 weeks kills some Trichinella species, but not all
Wild game meat must be cooked thoroughly
What is the life cycle of Anisakis?
Eggs hatch in saltwater, (free swimming) larvae eaten by crustaceans→ eaten by fish or squid→ nematodes burrow through the intestine for form cysts on outside of organs, sometimes the muscle of beneath the skin
Fish eaten my marine mammal or human and the meatotode forms a cyst in the intestine → releases eggs into seawater via host feces
Who is at risk for Anisakis?
Anyone who eats raw or undercooked fish is potentially at risk (especially homemade sushi)
Many cases go undetected
What are the definitive and intermediate hosts?
Definitive host: mammals (including humans)
Intermediate host: crustaceans and then small fish/squid (that ate the crustacean)
What are the symptoms and treatment fo Anisakis?
Symptoms: abdominal pain, nausea, vomiting, diarrhea, obstruction of small intestine
Treatment: remove larvae through surgery (if obstruction), likely to die within weeks
How do you prevent Anisakis?
Cooking seafood to an internal temperature of 63C Freezing fish ( -20 for 7 days or -35 until solid, store at -35 for 15 hours/-20 for 24 hours)
What are the definitive and intermediate hosts of Toxoplasma gondii?
Definitive host: wild and domestic cats
Intermediate hostL most species of warm-blooded animals (birds, mice, squirrels, rabbits)
Cows, chicken, moose, sheep, horse, pig, mice, cariboo, possum
Explain the life cycle of T. gondii.
Oocysts are zygotic stage of life cycle, excreted from cat feces
Sporulate in 3 days
Asexual cycle occurs when consumption fo oocysts results in the infection of the intestine→ tachyzoite in the intestine, multiply until cell ruptures and systemic infection results→ infects new cells in the body- cardiac/CNS
Bradyzoites can form in the tissus, if ingested by felid→ sexual cycle occur
What are Tachyzoites?
Cause acute Toxoplasmosis
Invade all nucleated cells and occur in groups
Rapid multiplication and lyses cell
What are Bradyzoites?
Latent toxoplasmosis
Tissue cysts contain slow growing trophozoites as bradyzoites
Most common in brain, skeletal msucle and cardiac muscle
Remain for the life of the host
Recrudescence of infection in immunocompromised hosts
Where does T. gondii normally occur?
Infects all mammals, birds → all tissues → one of the most common human infections thorughout the world
High prevalnence in Inuit populations of northnern Canada (
North America (30-35%), Quebec (80%)
High in France due to eating undercooked meat
How do oocysts survive?
Cats are difinitve hosts
Shed oocyst for only 1-2 weeks following infection
Sporulate and become infective in 24-48hours
Only shed once
Oocyst survival
Potential to remian viable in the soil fro many years
Can be washed into the water system
Can sporulate in water and remain infectious for mice for up to 6 months
What are the 4 Toxoplasmosis?
Acute Tocoplasmosis
Caused by invasion of tachyzoites
Majority of cases are asymptomatic
Mild fever, sore muscles, swollen glands and lymph
Cerebral Toxoplasmosis
Immunocompromised individuals are at greater risk
Bradyzoites can transform into tachyzoites and start propagating
Ocular Toxoplasmosis
Infection in young children or immunosuppressed individuals commonly results in damage to eyes
Ocular symptoms include: strabismus, retinochoroiditis, inactive retinal scarring, panuveitis, uveitis, and neuroretinis
Congenitival Toxoplasmosis
Pregnant womens fetus are at risk if the mother acquires the first infection during pregnancy
May lead to spontaenous abortion, still born, child with severe physical or metal diabilit
The baby is only at risk if a woman receives her first exposure to toxoplasmoss while pregnant
A woman with no previous exposure should aovid eating and handling raw meat, exposure to cat feces, and gardening ( cat feces common)
What are the risks of Toxoplasmosis when pregnant?
Only about 30-40% of women who are infected with Toxoplasma for the first time trasmit the infection to the baby
Risk of infecting the fetus is realted to the trimester at whcih acquired
Greatest in the third trimester (70%)
Early pregnancy is only 15%
Severity is inversely related
Most severe in first trimester
Least severe in last trimester
Common defects: blindness, seizures, intellectual disability, hydrocephalus
Is T. gondii waterborne?
YES
How is T. gondii transmitted?
Humans can becom infected by sevreal routes
Eating raw or undercooked meat
Food or water contaminated with cat feces
Contaminated environmental samples (feca
Blood transfusion
Transplacentally
How do you prevent T. gondii?
Wash hands Throuhly cook meat Wash and peel fruits and vegetables Clean littler box daily Feed cat commercial dry food (never raw meat) Cover outdoor sandbozes
What can Cryptoporidiosis survive?
Oocysts shed in feces of the host, can survive for long periods under coold moist conditions
Waterborne route is numerically most important
Water, food, travel , communities, HIV → how it is tranmitted, more at risk
Explain the three groups that are at risk for Cryptosporidiosis?
In HIV individuals
Prevalence in HIV with diarrhea is 3-16%
C. parvum is primarily reponsible for watery diarrhea tha last for >30 days
Mortality of AIDS pateints is 42%
In children
Mayn children die of diarrhea
Parasites are leading agents of chronic or persistent diarrhea worsened by specific risk factors such as malnutrition or immune deficiency
Healthy Individuals
Self-limiting and usually last for 1-2 weeks, diarrhea, abdominal pain, weight loss, nausea, vomting, fever
How is Cryptosporidiosis transmitted?
Human-human
day cares, hospitals, households
Animal-human
Farm visits of school children, petting zoo, turkey farms, pet animals
WAter
Drinking water, recreational water, swimming pools
Food
Fresh produce, unpasterurized apple cider
How do you prevent Cryptoposridis?
Resistant to chlorine and disinfectants
Wash raw fruit and vegetables
Avoid swallowing recreational water
Avoid drinking untreated water or treat water before drinking
Avoid unpasteurized milk or fruit juices
Wash your hands after contact with farm animals
Use caution when travelling to countries where water supply might be unsafe
Explain the lifecycle of Giardia.
Cyst: infective stage
Cysts can survive inwater at 4C for 3 months
10 cysts are sufficient to infect humans
How widespread is Giardia?
Worldwide
Giardisis is a major diarrheal disease foudn throughout the world
Most common identified parasite in the US
Most common protozoal intestinal parasite isolated worldwide
Farm Prevalnce- cows can harbour asymptomatically
Dairy
Beef
What are the symptoms of Giardia infection?
Some people can carry giardia parasite without experiencing any symptoms
Symptoms start 1-2 weeks after exposure
Common symptoms: fatigues, nausea, diarrhea or GREASY stools, loss of appetite,vomitng, blatoing and abdominal carmaps, weight loss, excessive gas, headaches, abdonmial pain
Infectiosn last 6-8 weeks, but problems sucha s lactose intolerance persist post infection
How is Giardiasis transmitted?
Human to human Animal to human Resevoir: cats, dogs, cattles, sheep, pigs, rodents, beavers, bears Water Drinking water, recreational water Food Fresh produce (herbs, leafy greens)
How do you prevent Giardia?
It is chlorine resistant
Avoid drinking intreated water or treat water beofre drinking (boil for 1 minute)
Wash hands after handling soil or feces
Use caution when travelling to countries where water supply might be unsafe
Avoid swallowing recreational water
Wash raw fruits and vegetables before eating
Which parasites are resistance to Chlorine?
Giardia, Cryptosporidium
What are the common contamination route for parasites?
Contaminated water for irrigation, mixing pesticides, washing and processing
Application of manure or sweage 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
What are some Pre-harvest Control measures?
Use treated water for irrigation, washing hands/equipment
Monitor heatlh and hygiene of farm workers (education)
Improved on-farm sanitation
Use of properly composted manure
Restricted access by livestock and other animals
Environmetnal resistance of cysts/oocysts
What are some post-harvest Control measures?
Use of treated water for washing/processing produce and equipment
Monitoring health and hygiene of farm workers (education)
Chemical and physical disinfectants
What are some control measures for Food Handlers?
Good personal hygiene (handwashing
washing /rinsing of produce
Cooking and freezing
