Trematodes (Flukes)

Question 1

Life stages

Answer 1

• Operculum: Lid or covering on egg
• Miracidia: Free-living ciliated larva
• Cercariae: Tadpole-like larvae; final and free swimming
• Metacercariae: Encysted resting stage

Question 2

Features of Trematodes

Answer 2

• Dorso-ventrally flattened (leaf-like)
• Oral and ventral suckers for attachment
• Incomplete alimentary tract (no anus)
• Hermaphroditic
• Indirect life cycle: Aquatic snails as IH

Question 3

Life cycle

Answer 3

• Eggs are passed in the DH’s feces, urine, sputum
• Miracidium develops in egg, released into fresh water
• Snail development: Miracidium enters snail, Develops into sporocyst, Develops redia (daughter sporocysts)
• Cercaria leave the snail
• Cercaria encyst on plant or animal 2nd IH, become metacercariae
• Metacercariae are ingested by DH and become adult flukes

Question 4

Paragonimus kellicotti

Answer 4

• Common name: Lung fluke -FH: Dog, cat, carnivores
• IH: Snails (1st), Crayfish (2nd)
• SOI: Lung parenchyma
• Signs: Lung cysts, Intermittent cough; Heavy infection causes severe cough, pneumonia, death
• Diagnosis: Thoracic radiograph, Fecal sedimentation, Transtracheal wash
• Treatment: Praziquantel

Question 5

Nanophyetus salmincola

Answer 5

• Common name: Salmon poisoning fluke
• FH: Dogs, cats, mink, raccoons, fish-eating mammals (including humans)
• IH: Snails (1st), Salmonid fish (2nd)
• SOI: Small intestine
• Signs: Extremely pathogenic, Neorickettsia helminthoeca causes “salmon poisoning”
• Diagnosis: Fecal sedimentation
• Treatment: Praziquantel, Fenbendazole, Tetracycline for Neorickettsia

Question 6

Alaria spp.

Answer 6

• Common name: Intestinal flukes
• FH: Dog, cat, fox, mink
• IH: Snails (1st), Tadpoles (2nd)
• PH: Frogs, snakes, mice, rats, birds, reptiles, wild boar, humans (zoonosis)
• SOI: Adults in small intestine, Immature stages in lungs
• Signs: Typically none, Migrating mesocercariae cause pulmonary hemorrhage
• Diagnosis: Fecal sedimentation
• Treatment: Praziquantel

Question 7

Platynosomum fastosum

Answer 7

-Common name: Lizard poisoning
-FH: Cat
-IH: Snail (1st), Crustacean (2nd)
-PH: Lizards, Toads
-PPP: 3mo
-SOI: Bile ducts
Signs: Hyperplastic bile ducts; “Lizard poisoning” causes palpable liver, icterus, and death
-Diagnosis: Double centrifugation with sugar, Liver biopsy
-Treatment: Praziquantel, Prevent lizard eating

Question 8

Fasciola hepatica

Answer 8

• FH: Cattle, sheep, goats, other ruminants, horses, zoonotic
• IH: Snails
• SOI: Bile ducts
• Signs: “Pipestem liver”, Anemia, Inappetance, “Bottle jaw”, Decreased production
• Diagnosis: Fecal sedimentation, Bulk milk ELISA testing (dairy herd), Necropsy, Elevated globulin, elevated albumin, elevated GGT
• Treatment: Flukicides (Sept. in SE, Mar. in NW), Snail control, Drain/fence off wetland

Question 9

Fascioloides magna

Answer 9

• Common name: Deer fluke
• FH: White tailed deer, elk, caribou, wild cervids
• DEH: Cattle, moose, horses, sika deer, bison, pigs
• AH: Sheep, goats
• IH: Snails
• SOI: Liver
• Signs: Deer and cattle - parasite encapsulated by host minimizes clinical effects (no hole in cattle), Sheep and goats - continuous migration of immature flukes in liver results in death before patent
• Diagnosis: Fecal sedimentation (FH), Necropsy (DEH/AH)
• Treatment: Flukicides against immature flukes, Snail control, Drainfence off wetland, No deer near livestock in endemic areas

Question 10

Paraphistomum spp.

Answer 10

• Common name: Rumen fluke, Stomach fluke
• FH: Cattle, sheep, goat, deer, buffalo, antelope
• IH: Snail
• PPP: 7-10wk
• SOI: Duodenum (immature), Rumen/stomach (adult)
• Signs: Relatively non-pathogenic, Large number of migrating juveniles leads to severe enteritis, diarrhea, dehydration, anemia, “bottle jaw”, can lead to secondary infections with Clostridium spp. which can cause death
• Diagnosis: Young animals with grazing history, Eggs usually not found
• Treatment: Oxyclozanide (mature/immature), Niclosamide (immature)