Unit 2: Plathyhelminthes: Trematoda, Monogenea, Cestoidea

Question 1

Flatworm Structure

Answer 1

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

Question 2

Class Trematoda (Digenea)

Answer 2

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

Question 3

Class Monogenea

Answer 3

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

Question 4

Class Cestoda

Answer 4

Tapeworms
Intestinal parasites in vertebrates
Humans are usually definitive hosts (juveniles are worse to have)

Question 5

Flukes

Answer 5

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

Question 6

Stages of development for Digenea larvae (6)

Answer 6

1. Egg - from the host to outside in water
2. Miricidium - hatches from egg, has cilia that can allow it to swim in water, free living
3. Sporocyst - develops in the snail - many cells develop
4. Redia - asexual reproduction in the host
5. Cercaria - outside of snail (free living) - has a type of tail
6. Metacercaria - free living - has to be eaten by host

Question 7

Where do flukes parasitize?

Answer 7

Digestive tract, liver, pancrease
Some in lungs, trachea, kidney, bladder, blood vessels
Some in eyes, nose, under the skin, and even brain (rare)

Question 8

Monostome

Answer 8

Only an oral sucker

Question 9

Amphystome

Answer 9

Has oral sucker and acetabulum at the posterior end of the body

Question 10

Distome

Answer 10

Oral sucker on the anterior end and acetabulum is elsewhere on the ventral surface of the body

Question 11

Fasciola hepatica

Answer 11

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

Question 12

Schistosoma sp.

Answer 12

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

Question 13

Dioecious

Answer 13

2 separate sexes

Question 14

3 Species of Schistosoma

Answer 14

S. mansoni
S. haematobium
S. japonicum

Question 15

How are the 3 species of Schistosoma each passed out of the body?

Answer 15

S. mansoni = in feces
S. japonicum = in feces (rarely in urine)
S. haematobium = in urine (rarely in feces)

Question 16

Gynecophoral canal

Answer 16

In schistosomes
The ventral groove on the male where the female worm levels
Adaptation so that they can find a mate really easily

Question 17

Clonorchis sinensis

Answer 17

Chinese or oriental liver fluke

Infects a lot of animals - dogs, cats, pigs, and rodents - can serve as reservoirs

Question 18

Clonorchis sinensis infection

Answer 18

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

Question 19

Modest vs Heavy infections of clonorchis sinensis infections

Answer 19

Modest: indigestion, epigastric discomfort, weakness, weight loss
Heavy: anemia, liver enlargement, slight jaundice, edema, diarrhea

Question 20

Treatment for Clonorchis sinensis

Answer 20

Praziquantel or albendazole (treat all flukes)
Cook fish well before consumption
Treat sewage before disposal

Question 21

Paragonimus westermani

Answer 21

Lung fluke in Asia, Africa and South America

Plump reddish brown oval worm

Question 22

Symptoms of paragonimus westermani

Answer 22

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

Question 23

Treatment of paragonimus westermani

Answer 23

Praziquantel taken orally
Adequate cooking of crustaceans
Improved sanitary conditions

Question 24

Fasciolopis buski symptoms

Answer 24

Epigastric pain, nausea, and diarrhea - especially in the morning
In heavier infections, can get edema and ascites (accumulation of fluid in the peritoneal cavity)

Question 25

Treatment of fasciolopis buski

Answer 25

Praziquantel Avoid water chestnuts from contaminated areas Treat sewage before disposal

Question 26

Monogenea body structures

Answer 26

``` 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) ```

Question 27

Gyrodactylus salaris

Answer 27

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

Question 28

Gyrodactylus salaris treatment

Answer 28

Rotenone (indiscriminate so not very good) | Dosing small volumes of aqueous aluminium and sulfuric acid into the river (kills parasite without harming the host)

Question 29

Gyrodactylus elegans

Answer 29

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

Question 30

Diplozoon paradoxum

Answer 30

Lives on gils of fish

Question 31

Polystoma integerrimum

Answer 31

Frog bladde fluke Its reproductive cycle is in harmony with the frogs Larval parasites live on the gills of the frogs tadpoles See slides

Question 32

Gyrocotyle sp.

Answer 32

Class cestodia Related to tapeworms and monogenetic trematodes Parasites of the intestinal tracts of chimaeroid fish

Question 33

Subclass Eucestoda (tapeworms)

Answer 33

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

Question 34

Structure of tapeworms

Answer 34

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

Question 35

Monozoic

Answer 35

Tapeworms that have only one proglottid

Question 36

Polyzoic

Answer 36

Most tapeworms | Bodies consist of a chain of independent proglottids

Question 37

Taenia saginata

Answer 37

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

Question 38

Taenia solium

Answer 38

Pork tapeworm Globular scolex with 4 suckers and a circular row of hooks (solar appearance) Slightly smaller than T saginata

Question 39

Tapeworm symptoms

Answer 39

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

Question 40

Cysticercosis

Answer 40

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

Question 41

Tapeworm Treatment

Answer 41

Praziquantel! Have to make sure scolex is out Inspection of beef and pork Adequate cooking or freezing of meat

Question 42

Diphyllobothrium latum

Answer 42

Fish or broad tapeworm Worldwide distribution Get it from eating raw or improperly cooked fresh water fish

Question 43

Diphyllobothrium latum morphology

Answer 43

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

Question 44

Diphyllobothrium latum symptoms

Answer 44

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

Question 45

Diphyllobothrium latum treatment

Answer 45

Praziquantel is the drug of choice Freezing for 24 hours, thorough cooking, pickling fish Fish reservoirs have to be kept free of raw sewage

Question 46

Hymenolepis nana | reservoir, infection mode, light vs heavy infections

Answer 46

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

Question 47

Hymenolepis nana Treatment

Answer 47

Nicolsamide (NOT praziquantel) | Hygiene is the best control

Question 48

2 Species of Echinococcsis (hydatid)

Answer 48

E. granulosus and E. multilocularis | Can cause hydatid cysts - same as cystecerci

Question 49

Echinococcus granulosus | morphology

Answer 49

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

Question 50

Echinococcus granulosus symptoms

Answer 50

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

Question 51

Echinococcus granulosus Diagnosis

Answer 51

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

Question 52

Echinococcus granulosus Treatment

Answer 52

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

Question 53

``` Echinococcus multilocularis (intermediate host, cyst structure, treatment, prevention) ```

Answer 53

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