Liver Parasites

Question 1

Explain the life cycle of Capillaria hepatica

Answer 1

Unusual life cycle
A rodent is infected through ingestion of a infective egg -> Egg hatches: L3-adult development happens during larval migration (intestine into the liver via HPV) -> Adult sits in the liver and produces eggs -> Adult dies in the liver and eggs stay in the liver -. next one of two things can happen:
1) Rodent or dead rodent is ingested by a carnivore -> eggs pass through and are passed out in faeces as embryonated eggs.
2) The rodent dies, decomposes releasing eggs -> embryonated eggs on the ground which can be picked up by rodent or carnivore host.

Question 2

What is the main reservoirs for Capillaria hepatica?

Answer 2

Rodents (Brown rat) and Lagomorphs

Question 3

What pathology is caused by Capillaria hepatica?

Answer 3

• Hepatomegaly
• Liver fibrosis
  Inflammatory cell infiltration

Question 4

What 4 anthelmintics can be used to treat Ascaris suum?

Answer 4

Ivermectin
Albendazole (inhibits embryonation)
Piperazine
Pyrantel

Question 5

Describe the life cycle of the Cestoda, Echinococcus granulosus

Answer 5

Definitive Host: Dog, Intermediate Host = Herbivore, Accidental Host = Human
Adult worm sits in SI of dog -> Passes out embryonated eggs (INFECTIVE STAGE) -> Egg is ingested by intermediate host (sheep, swine, cow etc.) -> ONCOSPHERE hatches which penetrates intestinal cells -> Forms a hydatid cyst in the lung, liver or other organ (DIAGNOSIS) -> Animal dies and the hydatid cyst is ingested by the dog -> Protoscolex from the cyst is released -> Scolex ataches to the S. intestine -> develops to adult.

Question 6

Explain what happens in humans if they a) ingest infective Echinococcus granulosus egg and b) if they ingest a Echinococcus granulosus hydatid cyst

Answer 6

Infective egg -> hydatid cyst will form inside the human

Hydatid cyst ingested -> nothing happens as the worm cannot develops in the human

Question 7

What are the intermediate hosts and definitive hosts for Echinococus multilocularis? How can the parasite affect humans?

Answer 7

IH = Rodent
DH = Dog
Humans = Causes cysts, spread easier in humansthan E. granulosus
Cysts are multilocular

Question 8

Name the 3 Fascioliidae of veterinary importnace

Answer 8

Fasciola hepatica
Fasciola gigantica
Fasciola magna

Question 9

Explain the general life cycle of Fasciola spp.

Answer 9

Adult fluke sits in liver of host -> Eggs shed in faeces -> Hatch into Miracidium which penetrates a snail -> Miracidia becomes sporocyct or Redia (within the snail) -> Redia become cercaria (free living larval stage used by the parasite to leave IH and reach DH) -> Forms into metacercaria on grass -> Ingested by DH, migrates to liver where matures.

Question 10

What is a miracidium?

Answer 10

Ciliated larval stage of Fasciola spp., used to infect snail

Question 11

What is a cercaria?

Answer 11

Free swimming larval stage of a parasite, has a tail

Question 12

What is a metacercaria?

Answer 12

Encysted cercari, waiting for ingestion by DH

Question 13

Explain the epidemiology and pathology of Fasciola magna

Answer 13

Known as Deer Liver Fluke - can infect other species
Cattle/Camelids = Dead-end host, little pathology, no eggs passed
Sheep/Goats = Aberrant host with incomplete lifecycle however huge migration causes significant disease
Deer = True definitive host, adults are encapsulated and little pathology

Question 14

What species does Fasciola gigantica mainly effect?

Answer 14

Cattle
Buffalo also (show strong resistance)
Mainly in Africa and Asia

Question 15

Explain the life cycle of the lesser fluke, Dicrocoelium dendriticum

Answer 15

NO LARVAL STAGE -> Infects herbivores (Cattle)
Adult worm sits in herbivores bile duct -> egss passed and are infective -> Miricidium ingested by snail -> leaves snail as cercaria deposited in snail slime -> Ants eat the slime and thus cercaria -> metacircaria encysts in the ant -> DH ingests the an -> migrates to bile duct

Question 16

Explain in detail the life-cycle of Fasciola hepatica

Answer 16

Adult fluke resides in the bile duct of sheep and lays eggs -> Fluke eggs are passed in faeces -> Eggs hatch to Miracidium -> Miracidium infect Lymnaeidae spp. of snail (Europe = Lymnaea truncatula) -> Snail releases cercaria -> Ceraria encysts on vegetation to metacercaria -> Ingested by ruminants -> Juvenile fluke migrates through the liver (causing pathology) -> reaches bile duct where it matures to an adult.

Question 17

How would you diagnose a suspected Fasciola hepatica infection?

Answer 17

FEC
Clinical exam -> reveals poor BCS and D++
Serum conentrations of liver enzymes AST, GGT and GLDH would be high
High eosinophils in the blood
ELISA now avilable

Question 18

What are the three stages of Fasciola hepaticq infection?

Answer 18

Acute
Sub-Acute
Chronic

Question 19

What will you observe in acute fasciliosis?

Answer 19

Sudden death (aug-Oct)
Liver damage/haemorrhage
Animal won’t be grazing but wont be dead either

Question 20

What will you observe in sub-acute Fasciliosis?

Answer 20

Rapid loss of BCS
Poor fleece quality 
Depression
Poor appetite
Inability to stand
Liver enzymes high
Happens in winter mstly

Question 21

What will you observe in Chronic fasciliosis?

Answer 21

Bottle jaw
Poor BCS
Poor fleec condition
Death @ Lambing
Eggs in faeces
Adult flukes in bile ducts (PM)

Question 22

What is infectious necrotic hepatits?

i.e. what causes it, pathology, clinical signs

Answer 22

Known as Black Disease -> seen in cattle and sheep
Caused by Clostridium novyi -> animal ingests these spores
Only cause pathology in areas of liver necrosis caused by migrating liver flukes -> Clostridium novy will multiply and release tissue toxins causing sever damage to the liver -> No clinical signs just sudden death.

Question 23

Explain how you would treat Fasciola hepatica and prevention/control methods?

Answer 23

Treat with Triclabendazole (Sep-Jan) -> additional treatment in wet years
Treat adults in May and June to reduce pasture contamination
Isolate and treat any new animals bought in
Triclabendazole resistance is building therefore prevent is better:
- Fence of wet areas and increase soil drainage
- Legally control wildlife vector Lymnaea truncatula
- Try and reduce contact animals will have with Lymnae truncatula

Question 24

Explain the epidemiology of Fasciola hepatica

Answer 24

• Spread is linked directly to the Lymnaea snail
• Increase in wet conditions will cause a spread of the snail and thus the fluke
• Massive increase in the UK recently with every infected animal production being reduced by 10-15% from loss of milk, wool, meat and liver condemnation -> also poor reproduction