Parasitology: Trematodes

Front 1

What are the 2 different Orders of Trematodes?

Back 1

Monogenea
Digenea

Front 2

General characteristics of Monogenean Trematodes.

Back 2

They are ectoparasites of fish and other aquatic animals.
They have a prominent attatchment called a haptor.
They have a direct life cycle.
Affects both farmed and wild fish.

Front 3

General characteristics of Digenean Trematodes.

Back 3

Endoparasites of humans, domestic, and wild animals.
Collectively referred to as “FLUKES”.
They have complex indirect life-cycles using mollusk intermediate hosts.
Most obvious external features are ventral and oral suckers.
Mouth leads to a muscular pharynx which pumps food into 2 blind ending caecae.
Most species are Hermaphodites:
Individuals cross fertilize.

Front 4

Describe the fluke tegument.

Back 4

It is metabolically active.
It provides protection until the predilection site is reached.
Plays an important role in the evasion of host immunity.

Front 5

Life cycle stages of Fasciola.

Back 5

Egg
Miracidium
Sporocyst
Redia
Cercaria
Metacercaria
Immature fluke :
“Marita”
Adult fluke

Front 6

Schistosomidae

Back 6

Schistosoma spp.
aka blood flukes
Found in the tropics.
Causes schistosomiasis in humans.
Sexes are separate.
No metacercariae stage: on release, the cercariae swim in water and actively seek their final host.

Front 7

Dicrocoelidae

Back 7

Dicrocoelium dendtriticum
Small fluke found in the bile ducts of ruminants and other herbivores.
2 intermediate hosts: land snails and wood ants.

Front 8

Paramphistomidae

Back 8

Paramphistomum spp.
Severe losses in ruminants in the wet tropics.
Plump, cylindrical adult attaches to wall of rumen without causing serious damage.
Eggs similar to Fasciola.
Intermediate host: water snails
Disease occurs when metacercariae are eaten in large numbers.
Enteritis and diarrhea result when immature flukes migrate along the small intestine toward rumen.

Front 9

Troglotrematidae

Back 9

Nanophyetus salmoncola
Parasitize small intestine of piscivorous carnivores of the Northwest.
Hosts become infected by eating infected salmon.
Hosts can be dogs, cats, coyotes, foxes, bears, raccoons, or minxes.
Host to rickettsial agent Neorickettsia helminthoeca which causes salmon poisoning.
Does not seriously affect humans.

Front 10

Which parasites cause Fasciolosis?

Back 10

Fasciola hepatica- sheep, cattle, rabbits, and sometimes horses. Can cause painful abdominal disease in humans.
Fasciola gigatica- in tropical regions.
Fascioloides- trematode of deer, fatal in sheep

Front 11

What is the intermediate host of Fasciola hepatica?

Back 11

A mollusk.
Usually a mud snail:
Lymnaea trunculata

Front 12

Acute Fasciolosis

Back 12

Sudden death, usually Sept – Nov.
Enlarged, pale, friable, hemorrhagic liver with >1000 immature flukes in liver parenchyma.
RARE in cattle.

Front 13

Subacute Fasciolosis

Back 13

Rapid weight loss over 1-2 weeks, usually Oct-Dec.
Anemia, enlarged liver w/hemorrhage; >500 flukes, 50/50 immature and adult.

Front 14

Chronic Fasciolosis

Back 14

Progressive weight loss over weeks or months, Jan – Mar
Anemia, hypoalbuminemia  edema
Small distorted cirrhotic liver; enlarged bile ducts; >250 adult flukes
CATTLE: calcification of bile-ducts

Front 15

Subclinical Fasciolosis

Back 15

In sheep:
Fleece weight and fiber quality affected even with small burdens.
Reduced reproductive performance?
Liver condemnations at slaughter.
Beef cattle:
Longer finishing times to slaughter weight.
Reduced carcass value, liver condemnation.
Dairy cows:
Reduced milk yield and quality.

Front 16

Describe the migration of fasciola.

Back 16

Metacercariae excyst  immature flukes in small intestine  migrate across peritoneal cavity (1 week)  liver  eat their way through liver parenchyma for 6-7 weeks (growing and becoming more destructive) enter bile ducts.
PPP 10-12 weeks
Bile ducts: adults (2-5cm long) in bile ducts feed on epithelium and blood  chronic inflammatory repsonse  fibrosis of bile duct wall (in cattle: calcification)

Front 17

What causes Acute and Chronic Fasciola?

Back 17

Acute disease: large numbers of metacercarie ingested over a short period of time.
Chronic disease: smaller number of metacercarie ingested over a longer period of time.

Front 18

Black Disease

Back 18

aka Infectious Necrotic Hepatitis
Occurs in sheep and occasionally cattle.
Caused by the toxins produced by Clostridium novyi.
Characterized by sudden death.
The migration of flukes creates ideal conditions for C. novyi.
Called "Black Disease" because of the So-called because of the black discoloration of subcutaneous tissues due to congestion and hemorrhage seen at post-mortem

Front 19

Schistosomatidae: life cycle

Back 19

EGGS- snail eats EGGS or MIRACIDIA penetrates snail-asexual multiplication in body of snail-CERCARIAE forms-CERCARIAE penetrates skin of definitive host- ADULT form in definitive host.

Front 20

Fasciolidae: life cycle

Back 20

EGGS-snail eats EGGS or MIRACIDIA penetrates snail- asexual multiplication in body of snail-CERCARIAE forms-METACERCARIAE forms, encysted on vegetation- definitive host ingests METACERCARIAE on vegetation- ADULT forms in definitive host.

Front 21

Opisthorchidae, Heterophyidae, Troglotrematidae: life cycle

Back 21

EGGS- snail eats EGGS or MIRACIDIA penetrates snail-asexual multiplication in body of snail-CERCARIAE forms-METACERCARIAE forms and encysts in fish, crayfish, etc.- definitive host ingests fish/crayfish with encysted METACERCARIE- ADULT develops in definitive host.

Front 22

Dicrocoelidae

Back 22

EGGS- snail eats EGGS or MIRACIDIA penetrates snail-asexual multiplication in body of snail-CERCARIAE forms-METACERCARIAE forms in ant- ant carrying METACERCARIAE is ingested by definitive host- ADULT develops inside definitive host.