Platyhelminthes - Diplostomidae

Question 1

What is the definitive host of the Diplostomes

Answer 1

Fish-eating organisms (piscivorous) such as birds or mammals

Question 2

What do Diplostomes use to attach to host?

Answer 2

Pseudosuckers on each side of the mouth with adhesive or tribocytic organ which secretes proteolytic enzymes

Question 3

______ sp. causes a symptom referred to as “black spot” in fish

Answer 3

Uvulifer

Question 4

How does Uvulifer sp. cause black spot?

Answer 4

Metacercaria enter outer muscle layers of fish and encyst. This causes melanin to build up in the cells surrounding it and results in black spots around the fish

Question 5

Describe the life cycle of Uvulifer ambloplitis

Answer 5

Definitive host is a bird, eggs passed in the bird’s feces. Develop in snail, then in fish. Fish is infected when cercariae penetrate skin. This is where they become neascus larva (metacercaria) and are eventually eaten by another fish.

Question 6

Describe the life cycle of Alaria americana, which is known for having a paratenic host in its life cycle

Answer 6

Definitive hosts are mammals such as foxes. Eggs are passed through feces into water, and miracidium hatches. Miracidium penetrates snail, sporocst develops and cercaria are released into the water. Cercaria penetrate tadpole and become mesocercaria.
Tadpoles CAN be ingested by mammals (they are infective), but most often they are ingested by water snakes that will eventually be eaten by mammals.
Once in the mammals, they migrate through gut wall into the coelom, entering the lungs, transforming into metacercaria, heading back down the esophagus and into the intestine where they become an adult.

Question 7

Alaria americana exhibits _____ migration once in the definitive host

Answer 7

Transpulmonary migration

Question 8

What is the very rare and unusual way in which humans may be infected with Alaria americana?

Answer 8

By eating undercooked frog legs

Question 9

F. hepatica is commonly known as _____. Why is this name misleading?

Answer 9

Sheep liver fluke - which is weird because it is found in cattle and humans as well

Question 10

F. hepatica causes a condition known as _____

Answer 10

Fascioliasis

Question 11

F. hepatica parasites live where? How do they cause pathology?

Answer 11

In the bile ducts inside the liver of mostly sheep and cattle. Cause pathology through migration through liver and bile ducts

Question 12

F. hepatica produces what symptoms?

Answer 12

Anaemia, inflammation, edema, cirrhosis of liver parenchyma, ulcers (if it leaves liver)

Question 13

What occurs when F. hepatica parasites leave the liver?

Answer 13

Cause ulcers, can get in many place such as brain and CNS

Question 14

Why is Fascioliasis infection in sheep and cattle important?

Answer 14

Results in low productivity (weight loss, low milk production), so no one will eat liver or meat from animal

Question 15

Briefly describe the general structure of F. hepatica parasites

Answer 15

Very large (up to 30mm), small but powerful oral sucker at cone on anterior end. Intestinal ceca are highly dendritic, and tegument is covered in spines. Ovaries and testes are highly dendritic. Form asymmetric eggs.

Question 16

Describe the general life cycle of F. hepatica

Answer 16

Worms reach sexual maturity in bile ducts with eggs passed in host feces. The miracidia then penetrate the first intermediate host (snail), reproduce asexually within snail into cercariae. Cercariae encyst on vegetation, resulting in a metacercaria which will then be ingested by herbivores.
Metacercaria “excyst” in the small intestine and burrow through intestinal tract into the liver

Question 17

How is F. hepatica treated?

Answer 17

Triclabendazole

Question 18

What romantic parasite only develop as pairs in capsules on a host liver?

Answer 18

Fascioloides magna

Question 19

Briefly describe the order Plagiorchiformes

Answer 19

Wide variety of vertebrate definitive hosts. Cercariae have unforked tail with dorsal finfold. encyst 2 intermediates hosts. Eggs are very small and must be eaten by snail host to hatch

Question 20

In the suborder Plagiorchiata the 2nd intermediate host is usually a _____

Answer 20

arthropod

Question 21

Briefly describe the appearance of the family Dicrocoeliidae within the Plagiorchiformes

Answer 21

Have a subterminal oral sucker, acetabulum anterior, and usually the body is pointed at both ends. The cecae are simple with testes in front of ovaries, uterus descending with ascending loop.

Question 22

What happens to the D. dendriticum cercariae after they enter a snail host?

Answer 22

They accumulate within lung or mantle cavity, where mucous accumulates around them. After a while the mucous is expelled from the snail and ants come along to eat the snot balls.

Question 23

Once D. dendriticum cercariae are ingested by ants, what happens?

Answer 23

Metacercariae can either enter the hemocoel and remain infective to next host, or enter the subesophageal ganglion and induce changes in behaviour (not infective). At night, the ants run out and clamp their jaws down on some grass and stay there all night (means that animals that usually wouldn’t eat ants may do so).

Question 24

How is possible for humans to ingest D. dendriticum

Answer 24

Through produce that may have ants on it or through directly eating ants

Question 25

How do carpenter ants infected by Brachylecithum mosquensis act “zombie-like”?

Answer 25

B. mosquensis encyst in the supra-esophageal ganglion and make the ant wander about aimlessly in the middle of the day, making them more likely to be eaten by the definitive bird host

Question 26

D. dendriticum infect what part of the body in definitive hosts? How severe can the infection become?

Answer 26

Encyst in small intestine, attracted by bile, then migrate to bile ducts and liver. Maturation takes 6-7 weeks can result in a parasite load over 40 000 per sheep

Question 27

How is D. dendriticum treated?

Answer 27

With benzimidizoles and praziquantel

Question 28

The primary definitive hosts of the family Brachylaimidae are the _____. What is the most astounding part of this organism’s life cycle?

Answer 28

Birds.
Brightly coloured sporocysts develop in snail (intermediate) host’s eye stalks and pulsate to make the snail more likely to be eaten by a bird. They also induce a behavioural change that causes the snail to move to the top of a leaf (positively phototactic).

Question 29

Briefly describe the life cycle of C. sinensis and how it affects humans

Answer 29

Eggs released with feces into water (often by deliberately fertilizing water with human waste). Snails eat eggs. Cercariae infect fish (usually aquaculture fish) and enter fish muscles. Humans can contract this by eating undercooked or uncooked fish (ex. seviche or sushi)