Unit 2: Plathyhelminthes: Trematoda, Monogenea, Cestoidea Flashcards
Flatworm Structure
Bilaterally symmetrical and triploblastic (3 cell layers)
No body cavity other than gut (have to be flat, gut is highly branched, respire by diffusion)
No anus
Only one opening to ingest food and expel waste
Class Trematoda (Digenea)
Also called flukes
All forms are parasitic
Specialized for parasitism in animal tissues
Parasitic in one, two or more intermediate hosts
Adults parasitize a definitive host
Class Monogenea
Usually hermaphrodite
The male reproductive system develops before the female
Direct life-cycles with no asexual repro (unlike Digenea)
Larval stage is generally ciliated (called oncomiracidium) that is responsible for transmission from host to host
Eat blood, mucus, and epithelial cells of host
Ectoparasites on gills
Class Cestoda
Tapeworms
Intestinal parasites in vertebrates
Humans are usually definitive hosts (juveniles are worse to have)
Flukes
Most common and abundant parasitic worm of all vertebrates
Parasitize nearly every organ
At least two hosts (first is a mollusc)
Many have have second or third intermediate hosts
Infect domestic animals and humans
Stages of development for Digenea larvae (6)
- Egg - from the host to outside in water
- Miricidium - hatches from egg, has cilia that can allow it to swim in water, free living
- Sporocyst - develops in the snail - many cells develop
- Redia - asexual reproduction in the host
- Cercaria - outside of snail (free living) - has a type of tail
- Metacercaria - free living - has to be eaten by host
Where do flukes parasitize?
Digestive tract, liver, pancrease
Some in lungs, trachea, kidney, bladder, blood vessels
Some in eyes, nose, under the skin, and even brain (rare)
Monostome
Only an oral sucker
Amphystome
Has oral sucker and acetabulum at the posterior end of the body
Distome
Oral sucker on the anterior end and acetabulum is elsewhere on the ventral surface of the body
Fasciola hepatica
Sheep liver fluke
Can be found in liver of other animals and humans too
Parasite resides in the bile ducts inside the liver rather than the liver itself
Schistosoma sp.
Reside in the veins of the definitive host (can block them and cause problems)
Sexes are separate (dioecious)
No second intermediate hosts (only the snail)
Can be pathogenic to humans
Eggs escape from the body by penetrating the walls of the veins, small intestine, or urinary bladder
Dioecious
2 separate sexes
3 Species of Schistosoma
S. mansoni
S. haematobium
S. japonicum
How are the 3 species of Schistosoma each passed out of the body?
S. mansoni = in feces
S. japonicum = in feces (rarely in urine)
S. haematobium = in urine (rarely in feces)
Gynecophoral canal
In schistosomes
The ventral groove on the male where the female worm levels
Adaptation so that they can find a mate really easily
Clonorchis sinensis
Chinese or oriental liver fluke
Infects a lot of animals - dogs, cats, pigs, and rodents - can serve as reservoirs
Clonorchis sinensis infection
Worm causes irritation of the bile ducts which become dilated and deviated
Liver enlarges, becomes necrotic and tender - function may be impaired
Adults feed on bile, so indigestion of lipids
Modest vs Heavy infections of clonorchis sinensis infections
Modest: indigestion, epigastric discomfort, weakness, weight loss
Heavy: anemia, liver enlargement, slight jaundice, edema, diarrhea
Treatment for Clonorchis sinensis
Praziquantel or albendazole (treat all flukes)
Cook fish well before consumption
Treat sewage before disposal
Paragonimus westermani
Lung fluke in Asia, Africa and South America
Plump reddish brown oval worm
Symptoms of paragonimus westermani
Dry cough, followed by the production of blood stained sputum
Pulmonary pain and pleurisy may develop
Worms may migrate to brain where they lay eggs and cause a granulomatous abscess resulting in symptoms similar to epilepsy
Treatment of paragonimus westermani
Praziquantel taken orally
Adequate cooking of crustaceans
Improved sanitary conditions
Fasciolopis buski symptoms
Epigastric pain, nausea, and diarrhea - especially in the morning
In heavier infections, can get edema and ascites (accumulation of fluid in the peritoneal cavity)
Treatment of fasciolopis buski
Praziquantel
Avoid water chestnuts from contaminated areas
Treat sewage before disposal
Monogenea body structures
Have haptor (attachment organ - little hooks) on posterior part of body in early life stages Some adults have prohaptor (for feeding) and opisthaptor (for attachment)
Gyrodactylus salaris
Ectoparasite mainly lives on skin of freshwater Atlantic salmon
Haptor is situated at the parasite’s posterior end
When feeing, the parasite glues the mouth end to the salmon - everts pharynx through the mouth and releases a digestive solution with proteolytic enzymes to dissolve skin
Gyrodactylus salaris treatment
Rotenone (indiscriminate so not very good)
Dosing small volumes of aqueous aluminium and sulfuric acid into the river (kills parasite without harming the host)
Gyrodactylus elegans
viviparous (produces living offspring, not eggs)
4 generations are born out of one ova
Adult gives birth to one young - it contains an embryonic form - which has another - which has another
Diplozoon paradoxum
Lives on gils of fish
Polystoma integerrimum
Frog bladde fluke
Its reproductive cycle is in harmony with the frogs
Larval parasites live on the gills of the frogs tadpoles
See slides
Gyrocotyle sp.
Class cestodia
Related to tapeworms and monogenetic trematodes
Parasites of the intestinal tracts of chimaeroid fish
Subclass Eucestoda (tapeworms)
Have scolex (holdfast) and proglottids (strobila)
All vertebrates can get infections
Life cycles involve two or more hosts
Adult found in definitive host (small intestine) - much better to be definitive hosts than intermediate
Immature forms (in intermediate host) are called metacestodes
Structure of tapeworms
Scolex, neck and proglottids
proglottids develop in neck, get pushed back, and grow - separate from each other
Only have repro system - nutrients and oxygen diffuse
Monozoic
Tapeworms that have only one proglottid
Polyzoic
Most tapeworms
Bodies consist of a chain of independent proglottids
Taenia saginata
Beef tapeworm
Long and broad
4 suckers but no hooks or neck (that is visible)
Several hundred segments
Peripheral radial striations and its embryo has 3 hooklets
Taenia solium
Pork tapeworm
Globular scolex with 4 suckers and a circular row of hooks (solar appearance)
Slightly smaller than T saginata
Tapeworm symptoms
Light infections remain asymptomatic
Heavier infections may produce: abdominal discomfort, epigastric pain, vomiting, diarrhea
Will see shedding proglottids - crawl out of anus or in feces
Cysticercosis
T solium eggs can infect humans and cause cysts in lung, liver, eye and brain
Can result in blindness and neurological disorders
Symptoms due to inflammatory/immune responses
Tapeworm Treatment
Praziquantel!
Have to make sure scolex is out
Inspection of beef and pork
Adequate cooking or freezing of meat
Diphyllobothrium latum
Fish or broad tapeworm
Worldwide distribution
Get it from eating raw or improperly cooked fresh water fish
Diphyllobothrium latum morphology
Longest tapeworm in humans (3-10 m) with more than 3000 proglottids
Scolex looks like two almond shaped leaves
Proglottids are broader than they are long
Eggs are 30x50micrometers and embryos has 3 pairs of hooklets
Diphyllobothrium latum symptoms
May be mild depending on the number of worms (abdominal discomfort, loss of weight, loss of appetitie and malnutrition)
Anemia and neurological problems associated with vitamin B12 deficiency are seen in heavily infected individuals
Diphyllobothrium latum treatment
Praziquantel is the drug of choice
Freezing for 24 hours, thorough cooking, pickling fish
Fish reservoirs have to be kept free of raw sewage
Hymenolepis nana
reservoir, infection mode, light vs heavy infections
Dwarf tapeworm
Infects children
Rodents are reservoir
Infection by the oro-fecal mode
Cross infection and auto infection by eggs in feces is normal
Light infects produce vague abdominal disturbanes, heavier infections may cause enteritis
Hymenolepis nana Treatment
Nicolsamide (NOT praziquantel)
Hygiene is the best control
2 Species of Echinococcsis (hydatid)
E. granulosus and E. multilocularis
Can cause hydatid cysts - same as cystecerci
Echinococcus granulosus
morphology
Smallest of all tapeworms (3-9 mm long)
Only 3 proglottids
Forms cysts - has an outer anuclear hyaline cuticula and an inner nucleated germinal layer containing clear yellow fluid
Echinococcus granulosus symptoms
Comparable to those of a slowly growing tumor depend upon location of the cyst
-Large abdominal cysts produce increasing discomfort
-Liver cysts obstructive jaundice
-Peribronchial cysts produce pulmonary abscesses
-Brain cysts produce intracranial pressure and epilepsy
-Kidney cysts cause renal dysfunction
Contents of a cyst may produce anaphylactic responses
Echinococcus granulosus Diagnosis
Clinical symptoms of a slow growing tumour accompanied by eosinophilia
Intradermal test with hydatid fluid
Can see calcified cysts with X rays
Detect antibodies with ELISA
Echinococcus granulosus Treatment
Surgical removal of cyst
Inactivation of hydatid sand by injecting 10% formalin and then removal
High doses of Mebendazole
Avoiding contact with infected dogs and cats and eliminating their infection
Echinococcus multilocularis (intermediate host, cyst structure, treatment, prevention)
Similar to E. granulosus - similar morphology and life cycle except RODENTS are its intermediate host
Cysts are multilocular (many chambers)
Resistant to praziquantel - need high doses of Albendazole
Surgery to remove cyst and rodent control for prevention
