Trematodes - Trematoda Flashcards
General trematode life stage
Adult –> egg –> miracidium –> sporocyst/redia –> cercaria –> metacercaria –> adult
Adult life stage
- found in DH
- variable size
- pair of suckers (oral and ventral)
- monoecious (except schistosomes)
- egg laying stage
Egg life stage
Operculated!
- unembryonated vs embryonated
Miracidium life stage
Ciliated with penetration glands
- could be very host specific
Cercaria life stage
Mollusk intermediate host
- bores thru snail tissue
Metacercaria life stage
Encysted in environment or in an IH
- encyst on vegetation: Fasciola hepatica, Fascioloides magna, Paramphistomum
- encyst on IH: Dicrocoelium dendriticum (ants), Platynosomum fastosum (lizards), Paragonimus kellicotti (crawfish), Nanophyetus salmincola (salmon), Alaria (mesocercariae, frogs)
Fasciola hepatica
Liver fluke, liver rot, fascioliasis
- DH: ruminants, pigs, horses, wide range of mammalian wildlife
- IH: lymnaeid snails
- metacercariae encyst on vegetation
- site in DH: bile ducts, liver
Fasciola hepatica prevalence
Worldwide
- gulf coast, SE states, pacific northwest, rocky mountains, eastern Canada
Fasciola hepatica life cycle
DH ingests metacercariae –> excyst in SI, juvenile fluke penetrates gut, abdominal cavity to liver by 4-6 days –> liver migration for 6-8 wks –> to bile duct and matures to adult –> unembryonated eggs in bile to intestine, shed in feces to water in environment –> in 10-12 days miracidia hatch in water –> penetrates lymnaied snail, undergoes asexual repro –> cercariae emerge attach to vegetation and encyst as metacercariae
Fasciola hepatica pathology
Immature flukes - hepatitis - fibrotic tracts - hemorrhage - anemia Adults - anemia - proliferation of bile duct epithelium - cholangitis - necrosis of duct walls - fibrosis (bile duct lamina propria, calcification)
Fasciola hepatica - acute disease
Primarily in sheep and goats that ingest large numbers of metacercariae
- inappetence, decrease weight
- abdominal pain
- anemia
- jaundice
- ascites
- depression
- sudden death
Fasciola hepatica - subacute disease
Massive infection from accumulated exposure/ingestion over time
- decrease weight
- hemorrhagic anemia
- liver failure
- death
Fasciola hepatica - chronic disease
Moderate infection, subtle loss
- decreased feed intake
- decreased weight
- decreased milk production
- anemia
- emaciation
- submandibular edema
Fasciola hepatica diagnosis in ruminant host
Eggs - fecal sedimentation - oval, operculated, yellow Adults - bile ducts - conical anterior end (cephalic cone) and shoulders Juveniles - liver parenchyma
Fasciola hepatica treatment
- triclabendazole (cattle and sheep only)
- albendazole (sheep, cattle, goats) –> valbazen (adult flukes)
- clorsulon (cattle) –> curatrem (immature adult flukes) –> ivomec plus (adult flukes)
Fasciola hepatica control
Avoid introduction of infected animals and hay (metacercariae)
- snail control: molluscicides (none approved in US), avoid snail habitats
Fasciola hepatica human infections
Rare in US
- symptoms: acute, epigastric pain, prolonged fever, enlarged liver, anemia, jaundice, liver fibrosis
- diagnosis: patent (4 months, ova in feces), ab testing, psuedofascioliasis (common in ppl who eat livers)
Fascioloides magna
- DH: primarily cervids (white tailed deer!)
- IH: lymnaeid snails
- metacercariae site: vegetation
- aberrant hosts: sheep, goats
- accidental/dead end hosts: cattle, pigs, llamas, horses, moose
Fascioloides magna prevalence
New world parasite common to north america
Fascioloides magna life cycle
DH ingests metacercariae –> excyst in SI, juvenile fluke migrate in abdominal cavity –> to liver, extended migration –> matures to adults in cysts in bile ducts (pairs) –> unembryonated eggs in bile to intestine, shed in feces to water in environment –> miracidia hatch in water –> penetrates lymnaeid snail, undergoes asexual repro –> cercariae emergy, attach to vegetation, form metacercariae
Fascioloides magna pathology - cervids
Natural definitive hosts (reservoirs)
- no pathology unless heavy infection
- flukes in thin walled cysts
- eggs leave cysts by channels to bile duct
Fascioloides magna pathology - accidental hosts
Large bovids (cattle), suids, llamas, horses, moose
- unapparent
- closed cysts
- no trematode ova in feces –> no channels to escape!!
- liver condemned (diffuse black pigment)
Fascioloides magna pathology - aberrant hosts
Sheep and goats
- uninterrupted migration
- no cysts, adults, or eggs
- highly pathogenic, traumatic hepatitis (hemorrhaging, necrosis, adhesive peritonitis)
Fascioloides magna diagnosis
Cervids - fecal sedimentation - adults encysted in liver Cattle - encapsulated, dead or empty calcified capsules Sheep and goats - adults not present - severe liver damage
Fascioloides magna treatment
- oxyclozanide (WTD)
- albendazole (sheep)
- clorsulon (sheep and cattle)
Fascioloides magna control
Avoid grazing on deer inhabited land
- exclude deer
- snail control (wetlands)
Paramphistomidae
Rumen flukes
- DH: cattle, goats, sheep
- problem in the tropics
- adults in rumen and reticulum
- IH: aquatic snail, metacercariae on vegetation
- usually non pathogenic, more pathogenic in young (diarrhea, enteritis)
- have a sucker on both ends
Paramphistomum life cycle
DH ingests metacercariae –> excysts in upper SI –> juveniles migrate to abomasum, reticulum, rumen –> matures to adults in rumen –> unembryonated eggs passed in feces –> miracidia hatch, penetrate aquatic snail, asexual repro –> cercariae released –> cercariae encysts, form metacercariae on vegetation
Paramphistomum diagnosis
Adults - in rumen/reticulum - stubby, pear shaped - incidental finding at necropsy Eggs - fecal sedimentation - oval, operculated, gray
Paramphistomum treatment
Usually not treated
- clorsulon
- levamisole
Dicrocoelium dendriticum life cycle
DH ingests ant with metacercariae –> excyst in SI, juvenile fluke migrate thru common bile duct and liver –> adults in bile duct. liver, gallbladder –> embryonated eggs in feces –> eggs ingested by land snail –> miracidia hatches from egg in snail, asexual repro –> cercariae released in slime ball –> ants ingest slime ball with cercariae –> metacercariae form in abdomen/brain, affect behavior, ants climb grass
Dicrocoelium dendriticum pathology
Mild to inapparent
- advanced infections: hepatic cirrhosis, proliferation of bile duct epithelium, condemned liver
- sheep: anemia, edema, decreased wool production and lactation
Dicrocoelium dendriticum diagnosis
Eggs - fecal sedimentation - brown, oval, operculated, embryonated Adults - flat, lancet shaped
Dicrocoelium dendriticum treatment/control
- treatment: usually not treated, abldendazole or fenbendazole
- control: avoid grazing early morning/late evening, eliminate IH
Dicrocoelium dendriticum human infections
- rare in humans: middle east, kenya, czech republic
- accidental ingestion of ant
- symptoms of liver bile duct involvement (mild)
- diagnosis: eggs in feces
- treatment: praziquantel
Platynosomum
- worldwide, southeastern US, Hawaii, central/south america
- DH: domestic and wild cats –> bile and pancreatic ducts, liver, gallbladder
- 1st IH: land snail
- 2nd IH: isopods (pill bugs), woodlice, cockroaches
- 3rd IH: lizards, toads, geckos
Platynosomum life cycle
Cat ingests infected lizard/amphibian with metacercariae –> excyst and move up SI to common bile duct to bile ducts and gallbladder –> adults in cat bile and pancreatic ducts, gallbladder –> embryonated eggs in feces –> land snail ingests eggs (w/ miracidia), asexual repro (cercariae develop) –> cercariae shed in sporocysts –> sporocysts with cercariae ingested by isopods, metacercariae form –> lizard/amphibian ingests isopod with metacercariae
Platynosomum pathology
Asymptomatic
- cumulative infection: “lizard poisoning”, proliferative cholangitis, cirrhosis
- anorexia, diarrhea, vomiting, weight loss
- liver: enlargement, fibrosis, jaundice
Platynosomum diagnosis
Eggs - fecal sedimentation - oval, brown, operculated - contain miracidia Adults - ultrasound - liver biopsy - necropsy
Platynosomum treatment/control
- praziquantel
- prevent predation of IH
