Dicrocoeliumdendriticum By Carolynn Peter & Ryan Hamm
Classification Kingdom Animalia PhylumPlatyhelminthes Class Trematoda Order Plagiorchiida Family Dicrocoeliidae Genus Dicrocoelium Species dendriticum
Background • Family Dicrocoeliidaeuse land snails as first intermediate host • Known as the “lancet fluke” or “small liver fluke” • Causes the diseasedicrocoellosis • Favors dry conditions • Human infection is rare, but can occur
Morphology • 6 to 10 mm long by 1.5 to 2.5 mm wide • Widest near the middle • Body is pointed at both ends • Lobate testes lie directly behind acetabulum • Loops of the uterus fill most of the body behind ovary
Hosts • Definitive Host: • Ruminants are the usual definitive hosts • Sheep, cattle, goats, deer • Accidental Host: • other herbivorous animals, carnivores, and humans can serve as a host • Intermediate Host: • Land snail (Cionellalubrica) • An ant (Formica fusca)
Geographic Range • Found in: • Most of Europe and Asia • North America • Australia • Northern Africa
Life Stages • Miracidium- first larval stage of a digenetic trematode • Mother sporocyst- asexual stage of development that forms more sporocysts • Cercariae- Juvenile digenetic trematode, produced by asexual reproduction within a sporocyst • Metacercariae- stage between cercaria and adult in the life cycle of most digenetic trematodes D. dendriticum egg containing a miracidium.
Life Cycle • http://www.youtube.com/watch?v=lGSUU3E9ZoM
Life Cycle in the Land Snail (1st intermediate host) • Adult flukes live in the bile ducts within the liver. • Eggs leave the liver and are passed with the feces. • The eggs contain a miracidia. • A land snail must eat the egg before it will hatch. • In the small intestine of the snail, the egg hatches and releases miracidia • The miracidia penetrates the gut wall and develops into a mother sporocyst in the digestive gland. • Mother sporocysts produce daughter sporocysts which produce cercariae . • Three months after infection the cercariae accumulate in the “lung” (mantle cavity) of the snail or on its body surface which causes the snail to produce thick mucus. • The mucous surrounds the cercariae and expels the cercariae in the slime ball as it crawls along.
Life Cycle in the Ant (2nd intermediate host) • Fluke development continues when the cercariae are eaten by the second definitive host an ant. • An ant will eat the slime ball and the cercariae become metacercariae • Most of the metacercariae (infective to definitive host) will encyst in the spaces between the organs of the ant where the blood circulates (hemocoel). • Some metacercariae migrate to the subesophageal ganglion of the ant and encyst there • These metacercariae (not infective to definitive host) are called “Brainworms” and will change the behavior of the ant. • In the evening the ants will crawl to the tops of grasses and other plants and hang from it's mandibles. • When the temperature warms up the ant returns to normal behavior. • On the grass and other plants the ant is susceptible to the definitive host during grazing.
Life Cycle in Definitive Host • Once eaten by a definitive host the metacercariaeexcysts in the duodenum. • It will migrate upstream to the bile ducts since it is attracted to bile and into the liver, mature and produce eggs. • Flukes mature in 6 to 7 weeks • Flukes reproduce by hermaphroditism • Eggs are produced and released in feces of definitive host
Symptoms • No trauma to the gut wall or liver parenchyma resulting from migrating juveniles • Biliary dysfunction • Bile duct inflammation • Fibrosis • Hepatocyte damage • Anemia • Edema • Emaciation
Diagnosis • Traditionally eggs of D. dendriticum are found in feces of infected animals • Post-mortem examination of liver • ELISA using D. dendriticum antigen can catch the disease early on
Treatment • Praziquantel • Benzimidazoles • Albenzole • Fenbenazole • Mebendazole
Control • Animal husbandry practices • Do not allow ruminants to graze in the early morning or at night • Try and control the intermediate hosts • Use chickens, geese or ducks
Quiz Time • What are the two intermediate hosts? • Land Snail and an Ant • What is the geographic range of D. dendriticum? • Most of Europe and Asia, North America, Australia, Northern Africa • Who are the accidental host? • Other herbivorous animals, carnivores, and humans • What life stage is a juvenile digenetic trematode? • cercariae • During the evening and morning hours, what unusual behavior does the ant display? • Ants climb and cling to top of grass at night or early morning • How is D. dendriticumdiagnosed? • Fecal exam for eggs, autopsy of liver, ELISA
References • Janovy, John Jr. and Roberts, Larry S., Foundations of Parasitiology, 8th Edition, 2009 • http://en.citizendium.org/wiki/Dicrocoelium_dendriticum • http://www.cdfound.to.it/html/dicro.htm • www.dpd.cdc.gov/dpdx/html/imagelibrary/Dicrocoeliasis_il.htm • www.suite101.com/content/dicrocoelium-dendriticum-a35177 • http://www.peteducation.com/article.cfm?c=2+2107+2255&aid=731