Bovis ISSN 2398-2993

Dicrocoelium dendriticum

Synonym(s): Common lancet fluke, small liver fluke

Contributor(s): Rob Kelly , Johannes Charlier

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Introduction

Classification

Taxonomy

  • Trematoda; Dicrocoeliidae; Dicrocoelium dendtriticum.

Etymology

  • Dicrocoelium dendriticum has a unique lifecycle that involves 3 hosts.
    • The two intermediate hosts are a snail and an ant.
    • Definitive host species include most herbivorous mammals. Definitive host species commonly infected include ruminants such as cattle, buffalos, small ruminants and cervids.
      • Equids, camelids pigs, rabbits and humans are infected extremely rarely.
  • Rarely pathogenic to cattle compared to Fasciola liver flukes.
  • Will occasionally cause cholangitis and fibrosis that may limit production in heavy infections.

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Clinical Effects

Epidemiology

Habitat

  • Epidemiology of D. dendriticum is dependent upon presence of 2 intermediate host species and definite host.
  • If detected in cattle bear in mind that if transported from elsewhere infection could have occurred elsewhere from current grazing.
  • Usually where the parasite is present it is uniformly present within the habitat due to the ubiquitous nature of intermediate hosts.
  • In Europe ants hibernate over winter until April/ May and definitive hosts can contract infections over the whole grazing season. Snails attain infection posy hibernation over winter from the start of spring onwards.

Lifecycle

  • Eggs are passed into the faeces of the definitive host onto pasture.
  • The miracidium is present at passage however it does not hatch until ingested by the intermediate snail host.
  • Snails feed around fecal pats thus facilitating transmission .
  • Within the snail intermediate hosts sporocyst development stages occur into cercarial stages.
  • The cercaria are secreted in the snails slime onto pasture forage where they await their second intermediate host.
  • The second intermediate host, Formica ants, ingest these “slime balls” which undergo further development stages within organs of the ant into metacercariae.
  • Some undergo development within the brain and affect the behavior of the ant. Causing the ants to migrate to the tips of forage, in twilight hours, to be ingested by their definitive hosts.
  • Once the infected Formica ant is ingested the metacercariae hatch in the small intestine of the definitive host.
  • Juveniles migrate up the main bile duct of the liver and onward into the smaller bile ducts along with the gall bladder (5-6 weeks post-infection).
  • The total pre-patent period (PPP) of the parasite is 10-12 weeks.
  • Note no parenchymal migration of the parasite occurs unlike Fasciola species.

Pathological effects

  • As there is no obligatory hepatic migratory phase within the lifecycle, there are few pathological effects and hence this parasite is usually of little concern to farmers.
  • Thus, economic losses resulting from D. dendriticum are less apparent than those caused by other liver flukes such (Fasciola hepatica). 
  • In heavy burdens parasites can cause fibrosis, cirrhosis and cholangitis of the liver that may result in production losses and liver condemnations in infected cattle.
  • Often the only change is mild distension of the bile ducts in cattle.

Other Host Effects

  • Clinical signs are usually absent.
  • In heavy burdens of D. dendriticum, where extensive pathological consequences are evident, weight loss, submandibular edema (bottle jaw) and anemia may occur.

Control

Control via animal

  • Other species, which may act as definitive hosts for D. dendriticum, might be of local ecological importance and should be considered in control strategies where applicable.

Control via chemotherapies

  • Albendazole (20mg/kg) and praziquantel Praziquantel (50mg/kg) are effective on adult stages of the parasite.
  • Fenbendazole Fenbendazole is also affective on adult stages of the parasite at a higher dose than normal (50mg/kg).
  • Repeat treatment maybe required where numerous cycles occur and with clinical infections where juvenile parasites are present.
  • In the UK, and many other countries, there are no drugs licenced to treat against for D. dendriticum. Therefore, remember to comply with local prescribing guidelines Cascade and medicines legislation.

Control via environment

  • Difficult as snails, ants and the eggs in the environment are reservoirs for the parasite.
  • The uniform distribution of the parasite, in ecological niches, where the intermediate hosts are present makes it hard to control.

Diagnosis

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Beck M A, Goater C P, Colwell D D & van Paridon B J (2014) Fluke abundance versus host age for an invasive trematode (Dicrocoelium dendriticum) of sympatric elk and beef cattle in southeastern Alberta, Canada. Int j parasitol parasites 3 (3), 263-268 PubMed.
  • Sargison N D, Baird G J, Sotiraki S, Gilleard J S & Busin V (2012) Hepatogenous photosensitisation in Scottish sheep casued by Dicrocoelium dendriticum. Vet parasitol 189, 233–237 PubMed.
  • Broglia A, Heidrich J, Lanfranchi P, Nöckler K & Schuster R (2009) Experimental ELISA for diagnosis of ovine dicrocoeliosis and application in a field survey. Parasitol res 104, 949–953 PubMed.
  • Otranto D & Traversa D (2002) A review of dicrocoeliosis of ruminants including recent advances in the diagnosis and treatment. Vet parasitol 107, 317–335 PubMed.
  • Manga-González M Y, González-Lanza C, Cabanas E & Campo R (2001) Contributions to and review of dicrocoeliosis, with special reference to the intermediate hosts of Dicrocoelium dendriticum. Parasitology 123 PubMed.

Other sources of information

  • Andrews A, Blowey R W, Boyd H & Eddy R G (2004) Bovine medicine: diseases and husbandry of cattle. 2nd edn. Oxford.
  • Taylor M A, Coop R L & Wall R L (2007) Veterinary Parasitology. 3rd edn. London. John Wiley and Sons Ltd.
  • Kaufmann K (1996) Parasitic infections of domestic animals. 1st edn. Basel, Birkhauser Verlag.

Organisation(s)

  • Royal (Dick) School of Veterinary Studies, University of Edinburgh, UK.

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