Trematodes - Trematoda

Question 1

General trematode life stage

Answer 1

Adult –> egg –> miracidium –> sporocyst/redia –> cercaria –> metacercaria –> adult

Question 2

Adult life stage

Answer 2

• found in DH
• variable size
• pair of suckers (oral and ventral)
• monoecious (except schistosomes)
• egg laying stage

Question 3

Egg life stage

Answer 3

Operculated!

- unembryonated vs embryonated

Question 4

Miracidium life stage

Answer 4

Ciliated with penetration glands

- could be very host specific

Question 5

Cercaria life stage

Answer 5

Mollusk intermediate host

- bores thru snail tissue

Question 6

Metacercaria life stage

Answer 6

Encysted in environment or in an IH

• encyst on vegetation: Fasciola hepatica, Fascioloides magna, Paramphistomum
• encyst on IH: Dicrocoelium dendriticum (ants), Platynosomum fastosum (lizards), Paragonimus kellicotti (crawfish), Nanophyetus salmincola (salmon), Alaria (mesocercariae, frogs)

Question 7

Fasciola hepatica

Answer 7

Liver fluke, liver rot, fascioliasis

• DH: ruminants, pigs, horses, wide range of mammalian wildlife
• IH: lymnaeid snails
• metacercariae encyst on vegetation
• site in DH: bile ducts, liver

Question 8

Fasciola hepatica prevalence

Answer 8

Worldwide

- gulf coast, SE states, pacific northwest, rocky mountains, eastern Canada

Question 9

Fasciola hepatica life cycle

Answer 9

DH ingests metacercariae –> excyst in SI, juvenile fluke penetrates gut, abdominal cavity to liver by 4-6 days –> liver migration for 6-8 wks –> to bile duct and matures to adult –> unembryonated eggs in bile to intestine, shed in feces to water in environment –> in 10-12 days miracidia hatch in water –> penetrates lymnaied snail, undergoes asexual repro –> cercariae emerge attach to vegetation and encyst as metacercariae

Question 10

Fasciola hepatica pathology

Answer 10

Immature flukes
- hepatitis
- fibrotic tracts
- hemorrhage
- anemia
Adults
- anemia
- proliferation of bile duct epithelium
- cholangitis
- necrosis of duct walls
- fibrosis (bile duct lamina propria, calcification)

Question 11

Fasciola hepatica - acute disease

Answer 11

Primarily in sheep and goats that ingest large numbers of metacercariae

• inappetence, decrease weight
• abdominal pain
• anemia
• jaundice
• ascites
• depression
• sudden death

Question 12

Fasciola hepatica - subacute disease

Answer 12

Massive infection from accumulated exposure/ingestion over time

• decrease weight
• hemorrhagic anemia
• liver failure
• death

Question 13

Fasciola hepatica - chronic disease

Answer 13

Moderate infection, subtle loss

• decreased feed intake
• decreased weight
• decreased milk production
• anemia
• emaciation
• submandibular edema

Question 14

Fasciola hepatica diagnosis in ruminant host

Answer 14

Eggs
- fecal sedimentation
- oval, operculated, yellow
Adults
- bile ducts
- conical anterior end (cephalic cone) and shoulders
Juveniles
- liver parenchyma

Question 15

Fasciola hepatica treatment

Answer 15

• triclabendazole (cattle and sheep only)
• albendazole (sheep, cattle, goats) –> valbazen (adult flukes)
• clorsulon (cattle) –> curatrem (immature adult flukes) –> ivomec plus (adult flukes)

Question 16

Fasciola hepatica control

Answer 16

Avoid introduction of infected animals and hay (metacercariae)
- snail control: molluscicides (none approved in US), avoid snail habitats

Question 17

Fasciola hepatica human infections

Answer 17

Rare in US

• symptoms: acute, epigastric pain, prolonged fever, enlarged liver, anemia, jaundice, liver fibrosis
• diagnosis: patent (4 months, ova in feces), ab testing, psuedofascioliasis (common in ppl who eat livers)

Question 18

Fascioloides magna

Answer 18

• DH: primarily cervids (white tailed deer!)
• IH: lymnaeid snails
• metacercariae site: vegetation
• aberrant hosts: sheep, goats
• accidental/dead end hosts: cattle, pigs, llamas, horses, moose

Question 19

Fascioloides magna prevalence

Answer 19

New world parasite common to north america

Question 20

Fascioloides magna life cycle

Answer 20

DH ingests metacercariae –> excyst in SI, juvenile fluke migrate in abdominal cavity –> to liver, extended migration –> matures to adults in cysts in bile ducts (pairs) –> unembryonated eggs in bile to intestine, shed in feces to water in environment –> miracidia hatch in water –> penetrates lymnaeid snail, undergoes asexual repro –> cercariae emergy, attach to vegetation, form metacercariae

Question 21

Fascioloides magna pathology - cervids

Answer 21

Natural definitive hosts (reservoirs)

• no pathology unless heavy infection
• flukes in thin walled cysts
• eggs leave cysts by channels to bile duct

Question 22

Fascioloides magna pathology - accidental hosts

Answer 22

Large bovids (cattle), suids, llamas, horses, moose

• unapparent
• closed cysts
• no trematode ova in feces –> no channels to escape!!
• liver condemned (diffuse black pigment)

Question 23

Fascioloides magna pathology - aberrant hosts

Answer 23

Sheep and goats

• uninterrupted migration
• no cysts, adults, or eggs
• highly pathogenic, traumatic hepatitis (hemorrhaging, necrosis, adhesive peritonitis)

Question 24

Fascioloides magna diagnosis

Answer 24

Cervids
- fecal sedimentation
- adults encysted in liver
Cattle
- encapsulated, dead or empty calcified capsules
Sheep and goats
- adults not present
- severe liver damage

Question 25

Fascioloides magna treatment

Answer 25

- oxyclozanide (WTD) - albendazole (sheep) - clorsulon (sheep and cattle)

Question 26

Fascioloides magna control

Answer 26

Avoid grazing on deer inhabited land - exclude deer - snail control (wetlands)

Question 27

Paramphistomidae

Answer 27

Rumen flukes - DH: cattle, goats, sheep - problem in the tropics - adults in rumen and reticulum - IH: aquatic snail, metacercariae on vegetation - usually non pathogenic, more pathogenic in young (diarrhea, enteritis) - have a sucker on both ends

Question 28

Paramphistomum life cycle

Answer 28

DH ingests metacercariae --> excysts in upper SI --> juveniles migrate to abomasum, reticulum, rumen --> matures to adults in rumen --> unembryonated eggs passed in feces --> miracidia hatch, penetrate aquatic snail, asexual repro --> cercariae released --> cercariae encysts, form metacercariae on vegetation

Question 29

Paramphistomum diagnosis

Answer 29

``` Adults - in rumen/reticulum - stubby, pear shaped - incidental finding at necropsy Eggs - fecal sedimentation - oval, operculated, gray ```

Question 30

Paramphistomum treatment

Answer 30

Usually not treated - clorsulon - levamisole

Question 31

Dicrocoelium dendriticum life cycle

Answer 31

DH ingests ant with metacercariae --> excyst in SI, juvenile fluke migrate thru common bile duct and liver --> adults in bile duct. liver, gallbladder --> embryonated eggs in feces --> eggs ingested by land snail --> miracidia hatches from egg in snail, asexual repro --> cercariae released in slime ball --> ants ingest slime ball with cercariae --> metacercariae form in abdomen/brain, affect behavior, ants climb grass

Question 32

Dicrocoelium dendriticum pathology

Answer 32

Mild to inapparent - advanced infections: hepatic cirrhosis, proliferation of bile duct epithelium, condemned liver - sheep: anemia, edema, decreased wool production and lactation

Question 33

Dicrocoelium dendriticum diagnosis

Answer 33

``` Eggs - fecal sedimentation - brown, oval, operculated, embryonated Adults - flat, lancet shaped ```

Question 34

Dicrocoelium dendriticum treatment/control

Answer 34

- treatment: usually not treated, abldendazole or fenbendazole - control: avoid grazing early morning/late evening, eliminate IH

Question 35

Dicrocoelium dendriticum human infections

Answer 35

- rare in humans: middle east, kenya, czech republic - accidental ingestion of ant - symptoms of liver bile duct involvement (mild) - diagnosis: eggs in feces - treatment: praziquantel

Question 36

Platynosomum

Answer 36

- worldwide, southeastern US, Hawaii, central/south america - DH: domestic and wild cats --> bile and pancreatic ducts, liver, gallbladder - 1st IH: land snail - 2nd IH: isopods (pill bugs), woodlice, cockroaches - 3rd IH: lizards, toads, geckos

Question 37

Platynosomum life cycle

Answer 37

Cat ingests infected lizard/amphibian with metacercariae --> excyst and move up SI to common bile duct to bile ducts and gallbladder --> adults in cat bile and pancreatic ducts, gallbladder --> embryonated eggs in feces --> land snail ingests eggs (w/ miracidia), asexual repro (cercariae develop) --> cercariae shed in sporocysts --> sporocysts with cercariae ingested by isopods, metacercariae form --> lizard/amphibian ingests isopod with metacercariae

Question 38

Platynosomum pathology

Answer 38

Asymptomatic - cumulative infection: "lizard poisoning", proliferative cholangitis, cirrhosis - anorexia, diarrhea, vomiting, weight loss - liver: enlargement, fibrosis, jaundice

Question 39

Platynosomum diagnosis

Answer 39

``` Eggs - fecal sedimentation - oval, brown, operculated - contain miracidia Adults - ultrasound - liver biopsy - necropsy ```

Question 40

Platynosomum treatment/control

Answer 40

- praziquantel | - prevent predation of IH