Parasitology: Platyhelminths Flashcards
General Characteristics of Phylum Platyhelmithes
- flat mostly
- hermaphrodites (have both sex organs)
- definitive host diagnosis– eggs
- at least 1 intermediate host (diagnosis is difficult)
- tapeworms and flukes
Which worms are associated with Class Cestoda?
Tapeworms
Characteristics of tapeworms
- segmented, often long
Where should we generally assume Cestodas are
in small intestine
T/F: tapeworms have an intestine
false; they do not, and they absorb nutrients across the surface
Tapeworms have at least 1 _____.
intermediate host
What are the segments of the Adult Tapeworm
- the scolex
- the neck
- Proglottids (segments)
What is the function of the Scolex?
the anterior end, has suckers and/or hooks that allow it to attach to gut wall, though they are capable of moving around
What is the importance of the neck in tapeworms?
it is the region of cell division, which gives rise to proglottids (segments)
these mature as they move down the chain
What are the Proglottids?
oldest segments of the tapeworm, located at the posterior end
Each segment of a tapeworm has at least _____
one set of all reproductive organs of both sexes
The segments of tapeworms are classifed as____ or _____
immature: fertilization cannot take place, will mature as it moves down the chain
Mature: fertilization can take place here.
A Gravid contains what?
fully developed eggs
What is a gravid?
a segment of Tapeworm that is full of eggs. Essentially, the uterus full of eggs. As soon as it comes out of the host, it is fully infective
What is the general term for a larval tapeworm?
metascestode
What is the general life cycle of tapeworms?
- Adult tapeworm lays eggs which are passed into environment.
- Infective eggs are eaten by the intermediate host.
- Metacestode/intermediate host eaten by the definitive host
What are the definitive and intermediate hosts of the family Taeniidae
vertebrates
What do the segments of Taeniidae look like?
square to rectangular in shape
Which stage is most important for disease and/or ecnomic loss?
the larval stage
Why don’t we see Taeniidae eggs in fecal samples
Because the eggs are located in the segments (gravid)
For the Family Taeniidae, the definitive host is generally a _____
predatory mammal
for the family Taeniidae, the intermediate host is generally a____
herbivore or carnivore
what are the two important larval forms of Taeniidae?
- Cystticercus
- Hydatid
What is cysticercus composed of?
- have fluid-filled bladder
- have an inverted, invaginated scolex
1 cysticercus will produce how many adult tapeworms in the definitive host
only 1
what is an infection with cysticercus called?
cysticercosis
What are some noteworthy taeniid species with canid or felid definitive hosts in the US.
- Taenia pisiformis
- Taenia taeniaeformis
- Taenia hydatigena
- Echinococcus mutilocularis
T. taeniaeformis is a common tapeworm of ____
hunting cats
What is the intermediate host of T. taeniaeformis? where are the larvae located?
- rodents
- the liver
What is the definitive host of T. pisiformis?
canids
What is the intermediate host of T. pisiformis?
rabbits
T/F: if a cat eats a rabbit infected with T. pisiformis, it will get a tape worm.
false
Clinical signs of tapeworms
- pretty benign, don’t cause many issues
- no diarrhea, no weight loss
T/F: fecal floats are good at detecting tapeworm eggs
false
How do you diagnose tapeworm infections?
segment or egg detection
T/F: tapeworm segments can move away from where they were dropped
true, to a short distance
how are tapeworm eggs dispersed from the segment?
segment dissolves or dries out, and the eggs are released
What is the definitive host of T. hydatigena
canids
What is the intermediate host of T. hydatigena
wild, domestic ruminants, pigs
Where are the cysticerci attached to in these intermediate hosts? When would these cause concern
on the peritoneal membranes; at slaughter of food animals
Why does Echinococcus have a different species name than other tapeworms?
its a different kind of tapeworm in its larval stage
Differentiate between Echinococcus spp. and Taenia spp.
Echinococcus spp. are much tinier than Taenia spp. (3-6 mm in length
- the host will have many small tapeworms rather than a few big ones
What is the metacestode stage of Echinococcus spp.
the Hydatid cyst.
T/F: Echinococcus spp. are zoonotic
true
What is the importance of the hydatid cyst asexual multiplication
multiple scoleces are formed, could potentially form thousands of scoleces
What are the two types of hydatid cysts?
- multilocular cysts, which continue to bud off new chambers (seen in E. multilocularis)
- unilocular hydatid cysts, which grows like a balloon as more buds form within it (seen in E. granulosus and others)
What is the definitive host of E. multilocularis
- foxes, but sometimes dogs and other canids (and rarely a cat)
What are the intermediate hosts of E. multilocularis?
small rodents, humans
What is the larval stage of E. multilocularis?
….. multilocular hydatid cyst
What is the clinical importance of E. multilocularis?
- ITS ZOONOTIC (hydatidosis)
- difficult to surgically remove because of invasive growth
T/F: Echinococcus multilocularis infection is easy to diagnose in dogs.
false, Hard af
What type of hydatid cyst do E. granluosus form?
unilocular hydatid cyst formed in intermediate hosts
What is the definitive host of E. granulosus? the intermediate host?
definitive: dogs
Intermediate: sheep
Should you expect your sheep guard dog to be infected with E. granulosus?
no, your guard dog shouldn’t be eating your sheep
Why don’t we worry about E. granulosus in US?
we don’t allow for the cycle to be completed. we remove the carcasses of sheep who die. The dogs therefore can’t eat them
What are the intermediate and definitive hosts of Taenia saginata?
definitive: humans
intermediate: bovines
What type of T. saginata larvae are present in the intermediate host? where in the host?
- cysticerci
- the muscles
Clinical importance of T. saginata
- causes mild abdominal discomfort
- occurs worldwide (was less of a problem in US, but prevalence likely rising due to immigrants from endemic areas and contaminated cattle feed)
How do you diagnose T. saginata?
- slaughter inspection: check masseter, tongue, heart incised, and other muscle examination
How do you treat T. saginata?
- none in cattle
- cysticerci killed by heating to 57 C or freezing to -10 C for 10 days
What are the definitive and intermediate hosts of Taenia solium?
Definitive: Humans
Intermediate: porcine
What are the concerns regarding T. solium infection in humans?
- humans can also be intermediate hosts for T. solium, The cysticerci can form anywhere in the body
- known as cysticercosis, neurocysticercosis
Clinical signs of cystercercosis/neurocysticercosis
- headache, confusion, seizures
- this is the leading cause of adult onset epilepsy
what are the intermediate hosts of Non-taeniid tapeworms
arthropods
What is the metacestode stage of non-taeniid tapeworms called?
cysticercoid
What does a cysticercoid look like?
a small cyst with an invaginated single scolex, no fluid filled bladder
What are the definitive and intermediate hosts of Dipylidium caninum?
- definitive: canids and felids
- intermediate: fleas
Dipylidium caninum lifecycle
- gravid segments released containing egg packets
- flea larvae ingest these egg packets, allowing cysticercoids to develop
- infection of definitive host follows ingestion of flea
What is the PPP of D. caninum
2 weeks
How do you diagnose D. caninum?
- tapeworm segments in perianal area
why can’t you see D. caninum eggs in a fecal float
the egg packets aren’t usually seen unless the segment has been broken up
What is the clinical importance of D. caninum infection?
infections are usually subclinical, may cause scooting
- can be zoonotic. Children are most likely to be infected, but this is very uncommon
What is crucial to breaking the D. caninum cycle?
year-round flea control
Anoplocephala perfoliata is the most common and important non taeniid tapeworm for which species?
horses
Moniezia spp. infect which host?
ruminants
What is the intermediate host of ruminant and equine tapeworms?
pasture mites
When are the definitive hosts of equine and ruminant tapeworms infected?
when they inadvertently ingest mites while grazing
What is the clinical importance of Anoplocephala perfoliata?
- while usually asymptomatic, this common infection can occasionally cause inflammation and ulceration.
- more severe cases, it can be associated with perforation, intussusception
T/F: it is difficult to diagnose Anoplocephala
true
T/F: horses are routinely treated at least once per year because Anoplocephala is hard to diagnose
true
T/F: Anaplocephala attach at the anterior end of the host GI tract.
false; they attach at the ileocecal junction
T/F: Anaplocephala is long, and horses are generally only infected with a few adults
false; they’re short and horses can be infected with many at once
T/f: Moniezia is a very common infection in ruminants, and is also easy to detect in fecal samples
true
What are the shapes of Moniezia spp. eggs in cattle and small ruminants?
- square shaped in cattle
- more triangular in small ruminants
Clinical significance of Moniezia infections?
- while it appears dramatic, it does not appear to have any significant effect on production
T/F: avian tapeworms can be pathogenic in large numbers
true
where would you expect to find cyclophyllidean tapeworms in birds?
in the small intestine
Which worm is associated with class Trematoda
flukes
Two orders of flukes
- Digenea (important flukes of domestic animals and humans)
- Monogenea (important external parasites of fish, reptiles, and invertebrates
Physical morphology of Order Digenea
- leaf-shaped
- unsegmented
- 1-2 suckers
Where are Digenea eggs passed?
in feces
How many intermediate hosts do Digenea flukes have?
- what is always the first intermediate host?
usually two
snails (which species of snail depends on which species of fluke)
Lifecycles of Trematode
- adult produces eggs
- egg hatches in water, ciliated larval stage hatches
- larvae swims to specific snail host, though some use land snails that ingest the egg
T/F: asexual development of Trematode occurs in the snail
true
What is the Trematode stage that emerges out of snails called
Cercaria
How do Cercaria reach their hosts?
- in water, they usually swim to it
- on land, they get ingested by the next host
What are larvae called when they are consumed by or attached to the second intermediate host?
metacercaria
How does the metacercaria get into the definitive host
ingestion
Where do the adults of Fasciola hepatica and Fascioloides magna live in their definitive hosts?
- Fasciola hepatica: liver and bile ducts of ruminants, rabbits, people, dogs, etc.
- Fascioloides magna: white-tailed deeer
Where do cercaria of F. hepatica encyst and become metacercaria?
on vegetation or debris. and they they wait to be consumed by the definitive host
After ingestion, where do larval flukes migrate?
- larval flukes migrate through intestinal wall to liver
- this migration in the liver may take several weeks
- Then enters bile duct and matures
Clinical importance of F. hepatica in cattle
can be a chronic disease, characterized by:
- anemia, hypoproteinemia
- weight loss, decreased milk production
- immunity will gradually develop
Why is clinical F. hepatica more severe in small ruminants than cattle?
- acute damage from larval migration can occur
- Black Disease (Clostridium)
What are the geographical US regions of clinical importance in regards to F. hepatica?
- Gulf Coast States
- Pacific northwest
- Hawaii
How is F. hepatica diagnosed?
- patient history and clinical signs
- fecal exam, using the SEDIMENT procedure (not very sensitive)
Control of F. hepatica
good management: drain, fence out wet areas to prevent spread of larval stages and snails
What geographical regions is Fascioloides magna more important in?
- Midwest and Northeast US
T/F: F. If a sheep or goat is infected with a magna larvae, it will continue to move around until the host dies
true
What is the 2nd intermediate host and definitive host of Nanophyetus salmincola
- 2nd host: fish
- DH: dogs
What is the importance of N. salmincola
it is a disease vector for a ricettsia organism that causes “salmon poisoning” in dogs
