Trematodes Flashcards
what are the 3 trematodes we looked at?
- fasciola hepatica
- platynosomum concinnum
- heterobilharzia americana (schistosome)
Trematodes
flukes (worms)
the 3 phylums of helminths
- platyhelminthes = flatworms
- Acanthocephala = thorny headed worms
- nematoda
general life cycle of fluke
- egg released in feces of DH. egg will contain a miracidium.
- miracidium ingested by snail where it grows and develops
- reaches cercaria stage - leaves snail and goes to IH or attach to vegetation where it waits to be eaten by DH.
life stages of trematode (fluke)
- egg
- miracidium
- sporocyst
- rediae (not necessary)
- cercariae
- metacercaria (infective stage!)
how to diagnose trematode (fluke) infections
fecal sedimentation - look for ova
faciola hepatica: general characteristics
liver fluke
- large animal fluke lives in bile ducts of cattle, goats, sheep
- most pathogenic fluke in US!!
- IH is aquatic snail (no 2nd IH)
- they have “broad shoulders”
- major reason of condemnation of slaughter houses due to fascioliasis, liver rot, liver fluke disease
fasciola hepatica: life cycle
- adults in bile ducts - operculated eggs shed in feces
- eggs contact water and hatch - a miracidium emerges
- miracidia penetrate 1st IH - aquatic snail. sporocysts develop
- cercariae develop, emerge from snail, settle at bottom of pond
- metarcercariae are ingested by DH
- metacercariae excyst in duodenum - juvenile flukes
- penetrate intestinal wall, enter abdominal cavity and contact liver capsule
- penetrate capsule, burrow into liver parenchyma ~ 2 months
- enter bile ducts, sexually mature in ~ 1 month
fasciola hepatica: transmission
seasonal: in cold climates they are common during warm season; while in warm climates they are common during the cold season; in tropical climates they are common during rainy season.
metacercariae are short lived on pasture; die within 30 days of snail’s departure. total fluke population, all stages survive summer months inside DH
Faciola hepatica: pathology
- no damage from juveniles.
- primary lesions = liver parenchyma or bile ducts
- can get acute, subacute and chronic fascioliasis
- more serious in small ruminants
- cattle = low grade, chronic disease
- sheep = acute disease
Acute Fascioliasis
- seen mostly in sheep
- traumatic hepatitis caused by large migration of juvenile flukes and extensive destruction of liver parenchyma
- death seen in several days due to intra-abdominal hemorrhage due to massive exposure (500+) to juvenile flukes
- lethal infections prepatent
- ## NOT seeing eggs in feces in acute fascioliasis bc they dont make it to adulthood
Subacute fascioliasis
less sudden onset of anemia, hypoproteinemia
- massive blood sucking by large number of newly adult flukes in bile ducts
- death less common
- eggs WILL be present in feces differentiate from acute fasciatitis
Chronic fascioliasis
- normally seen in cattle and sheep
- gradual onset of anemia
- moderate number of adult flukes present
- WILL see eggs in feces
- hepatic fibrosis caused by migration of juvenile flukes
- clinical signs in sheep: lack of vigor, diminished appetite, bottle jaw, emaciated
- clinical signs in cattle: constipated, digestive disturbances, emaciated
Platynosomum concinnum: general characteristics
“the lizard poisoning fluke” - trematoda
- infects liver, bile duct and pancreatic duct of cats
- found mostly in Fl
- 2 intermediate hosts: terrestrial snails, anoils spp. lizards (also toads, geckos, skinks) and pill bugs
life cycle of platynosomum concinnum
- excyst - migrate to bile ducts/liver and mature
- adults in bile duct of cats - operculated eggs leave the host via feces
- eggs contain a miracidium are ingested by 1st IH - terrestrial snail
- miracidium hatches - sporocyst & sporocyst-cercariae
4b. sporocyst-cercariae can be leave snail to be ingested by 2nd IH but not necessary - IH/cercariae are ingested by 2nd and 3rd IH
- cercariae encyst - metacercariae in bile ducts of lizard
- metacercariae remain in lizard until ingested by the DH - the cat
