Dicrocoelium dendriticum By Carolynn Peter & Ryan Hamm

Classification Kingdom Animalia Phylum Platyhelminthes Class Trematoda Order Plagiorchiida Family Dicrocoeliidae Genus Dicrocoelium Species dendriticum

Background Family Dicrocoeliidae use land snails as first intermediate host Family Dicrocoeliidae use land snails as first intermediate host Known as the “lancet fluke” or “small liver fluke” Known as the “lancet fluke” or “small liver fluke” Causes the disease dicrocoellosis Causes the disease dicrocoellosis Favors dry conditions Favors dry conditions Human infection is rare, but can occur Human infection is rare, but can occur

Morphology 6 to 10 mm long by 1.5 to 2.5 mm wide 6 to 10 mm long by 1.5 to 2.5 mm wide Widest near the middle Widest near the middle Body is pointed at both ends Body is pointed at both ends Lobate testes lie directly behind acetabulum Lobate testes lie directly behind acetabulum Loops of the uterus fill most of the body behind ovary Loops of the uterus fill most of the body behind ovary

Hosts Definitive Host: Definitive Host: Ruminants are the usual definitive hosts Ruminants are the usual definitive hosts Sheep, cattle, goats, deer Sheep, cattle, goats, deer Accidental Host: Accidental Host: other herbivorous animals, carnivores, and humans can serve as a host other herbivorous animals, carnivores, and humans can serve as a host Intermediate Host: Intermediate Host: Land snail (Cionella lubrica) Land snail (Cionella lubrica) An ant (Formica fusca) An ant (Formica fusca)

Geographic Range Found in: Found in: Most of Europe and Asia Most of Europe and Asia North America North America Australia Australia Northern Africa Northern Africa

Life Stages Miracidium- first larval stage of a digenetic trematode Miracidium- first larval stage of a digenetic trematode Mother sporocyst- asexual stage of development that forms more sporocysts Mother sporocyst- asexual stage of development that forms more sporocysts Cercariae- Juvenile digenetic trematode, produced by asexual reproduction within a sporocyst 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 Metacercariae- stage between cercaria and adult in the life cycle of most digenetic trematodes D. dendriticum egg containing a miracidium.

Life Cycle be.com/watch?v=l GSUU3E9ZoM be.com/watch?v=l GSUU3E9ZoM be.com/watch?v=l GSUU3E9ZoM be.com/watch?v=l GSUU3E9ZoM

Life Cycle in the Land Snail (1 st intermediate host) Adult flukes live in the bile ducts within the liver. Adult flukes live in the bile ducts within the liver. Eggs leave the liver and are passed with the feces. Eggs leave the liver and are passed with the feces. The eggs contain a miracidia. The eggs contain a miracidia. A land snail must eat the egg before it will hatch. A land snail must eat the egg before it will hatch. In the small intestine of the snail, the egg hatches and releases miracidia 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. The miracidia penetrates the gut wall and develops into a mother sporocyst in the digestive gland. Mother sporocysts produce daughter sporocysts which produce cercariae. 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. 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. The mucous surrounds the cercariae and expels the cercariae in the slime ball as it crawls along.

Life Cycle in the Ant (2 nd intermediate host) Fluke development continues when the cercariae are eaten by the second definitive host an ant. 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 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). 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 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. 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. 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. 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. 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 metacercariae excysts in the duodenum. Once eaten by a definitive host the metacercariae excysts 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. 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 mature in 6 to 7 weeks Flukes reproduce by hermaphroditism Flukes reproduce by hermaphroditism Eggs are produced and released in feces of definitive host Eggs are produced and released in feces of definitive host

Symptoms No trauma to the gut wall or liver parenchyma resulting from migrating juveniles No trauma to the gut wall or liver parenchyma resulting from migrating juveniles Biliary dysfunction Biliary dysfunction Bile duct inflammation Bile duct inflammation Fibrosis Fibrosis Hepatocyte damage Hepatocyte damage Anemia Anemia Edema Edema Emaciation Emaciation

Diagnosis Traditionally eggs of D. dendriticum are found in feces of infected animals Traditionally eggs of D. dendriticum are found in feces of infected animals Post-mortem examination of liver Post-mortem examination of liver ELISA using D. dendriticum antigen can catch the disease early on ELISA using D. dendriticum antigen can catch the disease early on

Treatment Praziquantel Praziquantel Benzimidazoles Benzimidazoles Albenzole Albenzole Fenbenazole Fenbenazole Mebendazole Mebendazole

Control Animal husbandry practices Animal husbandry practices Do not allow ruminants to graze in the early morning or at night Do not allow ruminants to graze in the early morning or at night Try and control the intermediate hosts Try and control the intermediate hosts Use chickens, geese or ducks Use chickens, geese or ducks

Quiz Time 1. What are the two intermediate hosts? A. Land Snail and an Ant 2. What is the geographic range of D. dendriticum? A. Most of Europe and Asia, North America, Australia, Northern Africa 3. Who are the accidental host? A. Other herbivorous animals, carnivores, and humans 4. What life stage is a juvenile digenetic trematode? A. cercariae 5. During the evening and morning hours, what unusual behavior does the ant display? A. Ants climb and cling to top of grass at night or early morning 6. How is D. dendriticum diagnosed? A. Fecal exam for eggs, autopsy of liver, ELISA

References Janovy, John Jr. and Roberts, Larry S., Foundations of Parasitiology, 8th Edition, 2009 Janovy, John Jr. and Roberts, Larry S., Foundations of Parasitiology, 8th Edition,