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Parasites of Dogs and Cats: Trematodes

Exam 2
STUDY
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Alaria spp:
Taxonomy
-Class: Trematoda
-Order: Digenea
-Family: Diplostomatidae
-Genus species: Alaria spp.
-Common Name: Intestinal Flukes
Alaria spp:
Hosts
-Final Hosts: Dogs, cats, foxes and minks
-Intermediate Hosts: Freshwater snails and frogs (tadpoles)
-Paratenic Hosts: Frogs, snakes, mice, rats, birds and other small mammals (raccoon, opossums), reptiles, humans
-Zoonosis
Alaria spp:
Identification
-Adults: 10mm, pink or brown, oral and ventral suckers and cylindrical hind part
-Egg: large 130um, oval, honey color, medium thick shell, operculum distinct
Alaria spp:
Life Cycle
-Eggs passed in feces and hatch in water
-Miracidia emerge, penetrate the snail (first IH) and emerge as cercaria
-Cecariae encyst in frogs (second IH) as mesocercariae
-Paratenic host ingests infected frog with mesocercariae
-FH ingest second IH or PH, the mesocercariae penetrates the gut wall, migrates to the lungs and develop to juvenile fluke
-Juvenile fluke migrates to trachea, is swallowed and matures in the small intestine
Spirometra spp:
PPP
5 weeks
Spirometra spp:
Sites of Infection
-Adults in small intestine
-Immature stages in lungs
Spirometra spp:
Pathogenesis and Lesions
-Heavy infections of adults cause severe duodenitis in FH
-Lung migration causes clinical illness
Spirometra spp:
Clinical Signs
Usually not evident in FH, but can be serious in paratenic host
Spirometra spp:
Diagnosis
Fecal sedimentation for detection of eggs
Spirometra spp:
Treatment and Prevention
-Praziquantel
-Other cestocide (even though it is a trematode)
Nanophyetus salmincola:
Taxonomy
-Class: Trematoda
-Order: Digenea
-Family: Troglotrematide
-Genus species: Nanophyetus salmincola
-Common Name: Salmon poisoning fluke
Nanophyetus salmincola:
Hosts
-Final Hosts: Dogs, cats, minks, raccoons, skunks, coyotes and other fish eating mammals
-Intermediate Hosts: Snails and fish
-Zoonosis
Nanophyetus salmincola:
Identification
-Adults: ovoid, creamy white, up to 2mm
-Egg: oval, yellowish brown, thick shell, 80um
Nanophyetus salmincola:
Life Cycle
-Eggs passed in feces and hatch in streams and become miracidia and pentrate the snail
-Cercariae emerge from snail to penetrate a fish to form metacercariae in various tissues (primarily kidneys, muscles, fins) and live up to 5 years
-Final host ingest the IH, the juvenile fluke encysts and matures in the small intestine
Nanophyetus salmincola:
PPP
1 week
Nanophyetus salmincola:
Sites of Infection
Adults in small intestine
Nanophyetus salmincola:
Pathogenesis and Lesions
-Extremely pathogenic
-Flukes are vectors of a rickettsial organism which causes severe hemorrhagic enteritis in dogs only (salmon poisioning)
Nanophyetus salmincola:
Clinical Signs
-Large numbers may cause diarrhea
-Salmon poising disease causes hemorrhagic enteritis, lymoh node enlargement, sudden onset fever, vomition, diarrhea, weight loss and high mortality
Nanophyetus salmincola:
Diagnosis
Fecal sedimentation for detection of eggs
Nanophyetus salmincola:
Treatment and Prevention
-Trematocidal anthelmintics
-Treat rickettsial organisms with tetracyclines
Paragonimus kellicotti:
Taxonomy
-Class: Trematoda
-Order: Digenea
-Family: Paragonimidae
-Genus species: Paragonimus kellicotti
-Common Name: Lung Fluke
Paragonimus kellicotti:
Hosts
-Final Hosts: dogs, cats and other carnivores
-Intermediate Hosts: snails and crayfish
-Zoonosis (10 species of Paragonimus which infect humans)
Paragonimus kellicotti:
Identification
-Adults: Ovoid, 16mm, reddish brown, occur in pairs and look like coffee beans with spiny cuticle
-Cysts: soft to solid, dark red-brown to gray, up to 50mm diameter, most commonly in the right caudal lung lobe
-Eggs: oval, yellowish brown, up to 110um with distinct operculum
Paragonimus kellicotti:
Life Cycle
-Eggs pass from pulmonary cyst containing flukes to a bronchiole and are swept up tracheaobronchial tree, swallowed and passed out in feces
-Eggs hatch in water to become miracidia and penetrate the snail
-Cercariae emerge from snail, infect a crayfish and encyst as metacercariae (infective)
-FH ingests the crayfish and juvenile cyst excysts to the lungs and mature in lung parenchyma
-Pairs are found in cysts and adults live for up to 4 years
Paragonimus kellicotti:
PPP
4-10 weeks
Paragonimus kellicotti:
Sites of Infection
In cysts in the lung parenchyma
Paragonimus kellicotti:
Pathogenesis and Lesions
Developing flukes cause formation of a cyst
Paragonimus kellicotti:
Clinical Signs
-Absent but intermittent cough can occur
-Heavy infection lead to more severe cough, pneumonia and death
Paragonimus kellicotti:
Diagnosis
-Radiographis lesions reveal cysts in lungs
-Egg in fecal flotation, but frequently distorted by the solution
-Sedimentation is the method of choice
Paragonimus kellicotti:
Treatment and Prevention
-Praziquantel effective
-Access to hosts difficult to prevent, not easy to control
Platynosomum fastosum:
Taxonomy
-Class: Trematoda
-Order: Digenea
-Family: Dicrocoeliidae
-Genus species: Platynosomum fastosum
Platynosomum fastosum:
Hosts
-Final Hosts: cats
-Intermediate Hosts (2): First is a snail and Second is a crustacean
-Paratenic Hosts: Lizards, toads, geckos and skinks
Platynosomum fastosum:
Identification
-Adult: 8mm in length
-Eggs: oval, brownish, up to 50um, medium tick shell, operculate
Platynosomum fastosum:
Life Cycle
-Eggs pass in feces into water
-Snails ingest eggs and devlop into miracidia and become cercariae
-Cercariae emerge from snails which infect crustaceans
-Metacercariae encyst in crustaceans
-PH ingest the crustacean
-FH ingest the IH or PH and they develop into juvenile flukes, which migrate up the bile ducts
Platynosomum fastosum:
PPP
3 months
Platynosomum fastosum:
Pathogenesis and Lesions
Cause hyperplasia of the bile ducts, thickened bile ducts with obstruction
Platynosomum fastosum:
Clinical Signs
-Mild infection tolerated
-Heavy infection results in "lizard poisoning": cirrhosis, jaundice, diarrhea, vomitting, lethargy, enlarged palpabel liver with distended abdomen, emaciation and death
Platynosomum fastosum:
Diagnosis
-Eggs on fecal sedimentation exam
-If bile ducts are obstructed there will be no eggs in feces
Platynosomum fastosum:
Treatment and Prevention
-Cestocidal drugs used with mixed results
-Surgery