Liver Parasites Flashcards
Explain the life cycle of Capillaria hepatica
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.
What is the main reservoirs for Capillaria hepatica?
Rodents (Brown rat) and Lagomorphs
What pathology is caused by Capillaria hepatica?
- Hepatomegaly
- Liver fibrosis
Inflammatory cell infiltration
What 4 anthelmintics can be used to treat Ascaris suum?
Ivermectin
Albendazole (inhibits embryonation)
Piperazine
Pyrantel
Describe the life cycle of the Cestoda, Echinococcus granulosus
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.
Explain what happens in humans if they a) ingest infective Echinococcus granulosus egg and b) if they ingest a Echinococcus granulosus hydatid cyst
Infective egg -> hydatid cyst will form inside the human
Hydatid cyst ingested -> nothing happens as the worm cannot develops in the human
What are the intermediate hosts and definitive hosts for Echinococus multilocularis? How can the parasite affect humans?
IH = Rodent
DH = Dog
Humans = Causes cysts, spread easier in humansthan E. granulosus
Cysts are multilocular
Name the 3 Fascioliidae of veterinary importnace
Fasciola hepatica
Fasciola gigantica
Fasciola magna
Explain the general life cycle of Fasciola spp.
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.
What is a miracidium?
Ciliated larval stage of Fasciola spp., used to infect snail
What is a cercaria?
Free swimming larval stage of a parasite, has a tail
What is a metacercaria?
Encysted cercari, waiting for ingestion by DH
Explain the epidemiology and pathology of Fasciola magna
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
What species does Fasciola gigantica mainly effect?
Cattle
Buffalo also (show strong resistance)
Mainly in Africa and Asia
Explain the life cycle of the lesser fluke, Dicrocoelium dendriticum
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
Explain in detail the life-cycle of Fasciola hepatica
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.
How would you diagnose a suspected Fasciola hepatica infection?
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
What are the three stages of Fasciola hepaticq infection?
Acute
Sub-Acute
Chronic
What will you observe in acute fasciliosis?
Sudden death (aug-Oct)
Liver damage/haemorrhage
Animal won’t be grazing but wont be dead either
What will you observe in sub-acute Fasciliosis?
Rapid loss of BCS Poor fleece quality Depression Poor appetite Inability to stand Liver enzymes high Happens in winter mstly
What will you observe in Chronic fasciliosis?
Bottle jaw Poor BCS Poor fleec condition Death @ Lambing Eggs in faeces Adult flukes in bile ducts (PM)
What is infectious necrotic hepatits?
i.e. what causes it, pathology, clinical signs
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.
Explain how you would treat Fasciola hepatica and prevention/control methods?
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
Explain the epidemiology of Fasciola hepatica
- 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
