Disease

Dicrocoeliasis

 

Introduction

Dicrocoeliasis is a disease of the liver caused by the liver flukes, Dicrocoelium dendriticum and Dicrocoelium hospes.  While relatively rare in humans, the disease is fairly common in grazing mammals throughout the world.  In humans it is generally not fatal, unless infections of the liver are very severe.  However, in animals it can be a serious problem as they can accumulate large numbers of the parasites in their bile ducts, eventually leading to cirrhosis.

 

Classification and taxonomy

Kingdom

Animalia

Phylum

Platyhelminthes

Class

Trematoda

Order

Plagiorchiida

Family

Dicrocoeliidae

Genus

Dicrocoelium

Species

D. dendriticum

D. hospes

[1]

 

Synonyms

This parasite is also known as the lancet liver fluke, or simply the lancet fluke [2].

 

History of discovery

Much of what is presently known about D. dendriticum is the result of the work of the naturalist Wendell Krull.[3]  While D. dendriticum was discovered by Rudolphi in 1819 and D. hospes was discovered by Loos in 1899, the full life cycle was not known until Krull and C.R. Mapes published a series of papers from 1951-1953 detailing their observations and experiments. It was known that D. dendriticum affected sheep, but everything else was a mystery. The first link in the chain was the discovery of the first intermediate host, the land snail Cionella lubrica [4].  Next came the discovery that the slime balls coughed up by the snails could be a potential method of transfer of the parasite [5].  Shortly thereafter, the ant, Formica fusca was found to be the second intermediate host by which sheep were infected [6].  The knowledge they generated is the foundation of our understanding of the parasite today. 

 

Clinical Presentation in Humans

D. dendriticum along with D. hospes are part of a group of trematodes that can infect the bile ducts of humans.  Because the bodies of these parasites are long and narrow, infections are generally confined to the more distal parts of the bile ducts.  As a result most D. dendriticum infections of the biliary tree produce only mild symptoms [7].  These symptoms can include biliary colic and general digestive disturbances, including bloating and diarrhea [8].  However, in heavier infections, bile ducts and the biliary epithelium may become enlarged in addition to the generation of fibrous tissue surrounding the ducts, and as a result, hepatomegaly and inflammation of the liver (cirrhosis) may occur [9].  In one unique case, an infection with D. dendriticum was associated with acute urticaria [10].

 

Transmission

Due to the highly specific nature of this parasiteŐs life cycle, human infections are generally rare [11].  Ruminants such as cows and sheep are usually the definitive host, but humans and other herbivorous mammals can also serve as definitive hosts through ingestion of infected ants [12].  One definitive case involved a man who ingested bottled water contaminated by infected ants [13].

 

Reservoir

The main reservoirs for D. dendriticum are sheep, cows, land snails and ants.  However, D. dendriticum has also been found in goats [14], pigs [15] and even llamas and alpacas [16].

The first intermediate host of D. dendriticum, the land snail [17]

 

The second intermediate host of D. dendriticum, Formica fusca [18]

 

Vector

There is no currently identified vector for D. dendriticum [19].

 

Incubation period

The incubation period for D. dendriticum is currently unknown [20].

 

Morphology

Morphology of D. dendriticum. OS stands for oral sucker, AC for acetabulum, TE for testes, VT for vitelline glands and UT for uterus [21]

 

D. dendriticum has a similar morphology to Chlonorchis sinensis, the Chinese liver fluke [22].  D. dendriticum is distinguished by lobed tested in the anterior of the body, as opposed to C. sinensis whose testes are located in the posterior [23].  They both are flat and have a characteristic taper at the anterior and posterior ends. The anterior is distinguished by an oral sucker at the point, an acetabulum and the testes. The posterior is where the uterus lies [24]. In the parasiteŐs mid-section lie the vitelline glands that are involved in egg formation [25].

 

Life cycle

D. dendriticum life cycle [26].

 

  1. Fully embryonated eggs are passed in the feces and spread in manure.
  2. The first intermediate host, land snails, ingest the eggs, which hatch once in the intestines and develop into miracidia.  These miracidia migrate to the liver where they become sporocysts.  The sporocysts then migrate to the digestive gland, where daughter sporocysts are produced.  The sporocysts in turn produce cercariae, which migrate to the snailŐs respiratory chamber.  In a defensive mechanism, the snail forms a slime ball around the parasites, walling them off.
  3. The snails sheds the parasites through coughing out the slime balls.
  4. The second intermediate hosts, ants, ingest the slime balls that are left behind by the snails. Once in the ant, the cercariae develop into metacercariae in the antŐs hemocoel.  From there, the metacercariae migrate through the body to the nerves that control the mandible.  From here, a single metacercariae remains in the nerve while the rest return to the abdomen and encyst.  The metacercaria that remains takes over control of the antŐs mandible, forcing it to exhibit uncharacteristic behavior.  As the temperature drops at night, rather than return to the colony, infected ants climb upwards to the top of a blade of grass, where they clamp on to the tip in order to increase the likelihood of ingestion by a grazing mammal.  Should the night pass without ingestion, the ant will return to the ground and rejoin the colony in order to evade exposure to sunlight and heat, which may kill the metacercariae.  The ant will repeat this cycle until it is ingested.
  5. Once ingested by the definitive host, the metacercariae excyst in the small intestine.
  6. The metacercarie migrate to the biliary tree, where they mature into adults and produce eggs.
  7. Humans can only become infected via the accidental ingestion of an infected ant.  However, once infected they can also serve as definitive hosts.

[27, 28]

 

Diagnostic tests

Tradtionally, diagnosis for dicrocoeliasis infection involves the identification of D. dendriticum eggs in the feces of a human or animal.  However, in humans, eggs in the stool may be a result of ingesting raw infected animal liver and may not in fact indicate dicrocoeliasis [29].  Therefore, examining bile or duodenal fluid for eggs is a more accurate diagnostic technique [30].

 

In animals, diagnosis has traditionally involved stool examination or post-mortem examination of the liver.  Recently, an ELISA using a D. dendriticum antigen was able to identify cases of dicrocoeliasis in sheep in Italy 28 days earlier than traditional methods [31].

Wet mount of D. dendriticum eggs [32].

 

Management and Therapy

Because human infections with D. dendriticum are so rare, there are multiple suggestions for treatment.  The standard treatment is with Praziquantel at 25 milligrams per kilogram three times a day for one day [33].  In one German patient 600 mg of Praziquantel administered three times a day for three days also proved to be successful in eliminating the parasite from the body [34].  Treatment with triclobendazole has also shown to be effective [35].  One treatment that has proven to be successful in both humans, sheep and goats was 2 capsules of Mirazid (300 mg) for six days [36].

 

Epidemiology

Dicrocoeliasis is believed to be endemic or potentially endemic in 30 countries. D. dendriticum is found throughout Europe (former U.S.S.R., Switzerland, Italy, Germany, Spain, Turkey), the Middle East (Iran), Asia (China, Japan, Vietnam), Africa (Ghana, Nigeria, Sierra Leone) and in North and South America and Australia.  The parasite tends to be found in areas that favor the intermediate hosts, such as fields with dry, chalky and alkaline soils [37].

Worldwide distribution of Dicrocoeliasis [38].

 

Public Health Prevention Strategies

Current public health prevention strategies have involved the condemnation of contaminated livers so as to eliminate any possibility for food-borne infection [39].

 

In addition, in 2007 the World Health Organization included Dicrocoelium dendriticum on its list of organisms to target with its Foodborne Disease Burden Epidemiology Reference Group [40].

 

References

  1. "Infectious Diseases: Dicrocoeliasis: Agent." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  2. "Infectious Diseases: Dicrocoeliasis: Synonyms." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  3. Esch, Gerald. Parasites and Infectious Disease Discovery by Serendipity and Otherwise (Parasites and Infectious Disease). New York: Cambridge UP, 2007.
  4. Krull, W. H., and C. R. Mapes. "Studies on the biology of Dicrocoelium dendriticum (Rudolphi, 1819) Looss, 1899 (Trematoda: Dicrocoeliidae), including its relation to the intermediate host, Cionella lubrica (MĚ¼ller). II. Collection of the snail, Cionella lubrica, and its maintenance in the laboratory." Cornell Vet 41 (1951): 433-44.
  5. Krull, W. H., and C. R. Mapes. "Studies on the biology of Dicrocoelium dendriticum (Rudolphi, 1819) Looss, 1899 (Trematoda: Dicrocoeliidae), including its relation to the intermediate host, Cionella lubrica (MĚ¼ller). III. Observations on the slimeballs of Dicrocoelium dendriticum." Cornell Vet 42 (1952): 253-76.
  6. Krull, W. H., and C. R. Mapes. "Studies on the biology of Dicrocoelium dendriticum (Rudolphi, 1819) looss, 1899 (Trematoda: Dicrocoeliidae), including its relation to the intermediate host, Cionella lubrica (MĚ¼ller). VII. The second intermediate host of Dicrocoelium dendriticum." Cornell Vet 42 (1952): 603-04.
  7. John, David T., and William A. Petri. Markell and Voge's Medical Parasitology. Philadelphia: Saunders, 2006. 173.
  8. Jack, J., E. Adusu, and T. Jelinek. "Human infection with Dicrocoelium dendriticum." Deutsche medinizische Wochenshrift 129 (2004): 2538-40.
  9. John, David T., and William A. Petri. Markell and Voge's Medical Parasitology. Philadelphia: Saunders, 2006. 178.
  10. Sing A, Tybus K, Fackler I. Acute urticaria associated with Dicrocoelium dendriticum infestation. Indian J Med Microbiol 2008;26:97-8
  11. John, David T., and William A. Petri. Markell and Voge's Medical Parasitology. Philadelphia: Saunders, 2006. 177.
  12. "Dicrocoeliasis." Division of Parasitic Diseases. 2009. Centers for Disease Control. 20 Feb. 2009 <http://dpd.cdc.gov/dpdx/Default.htm>.
  13. Drabick, J. J., and J. E. Egan. "Dicroceliasis (lancet fluke disease) in an HIV seropositive man." Journal of the American Medical Association 259 (1988).
  14. Ansari-Lari, Maryam, and Mohammad Moazzeni. "A retrospective survey of liver fluke disease in livestock based on abattoir data in Shiraz, south of Iran." Preventive Veterinary Medicine 73 (2006): 93-96.
  15. Capucchio, Maria T. "Natural trematode infestation in feral Nebrodi Black pigs: Pathological investigations." Veterinary Parasitology 159 (2009): 37-42.
  16. "Prevalence and significance of gastrointestinal helminths and protozoa in South American Camelids in Switzerland." Berl Munch Tierarztl Wochenschr 119 (2006): 291-4.
  17. "Dicrocoeliasis - Image Library Page 3." Microsoft Internet Information Server. Centers for Disease Control. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il3.htm>.
  18. "Echinostomiasis - Image Library Page 3." Microsoft Internet Information Server. Centers for Disease Control. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il3.htm>.
  19. "Infectious Diseases: Dicrocoeliasis: Vector." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  20. "Infectious Diseases: Dicrocoeliasis: Incubation period." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  21. "Dicrocoeliasis - Image Library Page 2." Microsoft Internet Information Server. Centers for Disease Control. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il2.htm>.
  22. John, David T., and William A. Petri. Markell and Voge's Medical Parasitology. Philadelphia: Saunders, 2006. 177.
  23. John, David T., and William A. Petri. Markell and Voge's Medical Parasitology. Philadelphia: Saunders, 2006. 177-78.
  24. "Dicrocoeliasis - Image Library Page 2." Microsoft Internet Information Server. Centers for Disease Contro. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il2.htm>.
  25. "Vitellarium -- Encylopedic Reference of Parasitology." Parasitology Research & Encyclopedic Reference of Parasitology. 20 Feb. 2009 <http://parasitology.informatik.uni-wuerzburg.de/login/n/h/1537.html>.
  26. "Dicrocoeliasis - Image Library Page 4." Microsoft Internet Information Server. Centers for Disease Control. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il4.htm>.
  27. Zimmer, Carl. Parasite Rex Inside The Bizarre World Of Natures Most Dangerous Creatures. New York: Free P, 2000. 87-88.
  28. "Dicrocoeliasis - Image Library Page 4." Microsoft Internet Information Server. Centers for Disease Control. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il4.htm>.
  29. El-Shiekh Mohamed, A. R., and V. Mummery. "Human dicrocoeliasis. Report on 208 cases from Saudi Arabia." Tropical and Geographical Medicine 42 (1990): 1-7.
  30. "Infectious Diseases: Dicrocoeliasis: Diagnostic tests." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  31. Broglia, A., J. Heidrick, P. Lanfranchi, K. Nockler, and R. Schuster. "Experimental ELISA for diagnosis of ovine dicrocoeliosis and application in a field survey." Parasitology Research 104 (2009): 949-53.
  32. "Dicrocoeliasis - Image Library Page 1." Microsoft Internet Information Server. Centers for Disease Control. 20 Feb. 2009 <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/Dicrocoeliasis/body_Dicrocoeliasis_il1.htm>.
  33. "Infectious Diseases: Dicrocoeliasis: Typical adult therapy." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  34. Jack, J., E. Adusu, and T. Jelinek. "Human infection with Dicrocoelium dendriticum." Deutsche medinizische Wochenshrift 129 (2004): 2538-40.).
  35. Karadag, Berrin. "An unusual case of biliary obstruction caused by Dicrocoelium dentriticum." Scandinavian Journal of Infectious Diseases 37 (2005): 385-88.
  36. Massoud, A., T. A. Morsy, and F. M. Haridy. "Treatment of Egyptian dicrocoeliasis in man and animals with Mirazid." Journal of the Egyptian Society of Parasitology 33 (2003): 437-42.
  37. Infectious Diseases: Dicrocoeliasis: Worldwide distribution." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  38. "Infectious Diseases: Worldwide distribution: Map." 2009. GIDEON. 20 Feb. 2009 <http://web.gideononline.com/web/epidemiology/?gdn_form=dmlldz1HZW5lcmFsJmRpc2Vhc2U9MTA2MTA=>.
  39. Ansari-Lari, Maryam, and Mohammad Moazzeni. "A retrospective survey of liver fluke disease in livestock based on abattoir data in Shiraz, south of Iran." Preventive Veterinary Medicine 73 (2006): 93-96.
  40. WHO Initiative to Estimate the Global Burden of Foodborne Diseases: First formal meeting of the Foodborne Disease Burden Epidemiology Reference Group (FERG). Geneva: World Health Organization, 2007.