Flukes / Trematodes

cystacanth

= encysted infective larva; of the Macracanthorhynchus hirudinaceus - has the ability to re-encyst in vertebrate (paratenic host) or re-encyst in DH, or develop to maturity in DH

Trematodes

= flukes - leaf-like shaped, no body cavity, dorso-ventrally flattened - indirect life cycle

Paragonimus kellicotti - characteristics, adult, egg stage

fluke of lungs - genital pore is located immediately posterior to the ventral sucker. - The testes lie opposite one another. - Adults usually in pairs in pulmonary cysts - Eggs: Yellow, large and vase-shaped eggs

What is the most important fluke that causes economical loss in cattle?

Fasciola hepatica

which trematodes are zoonotic? clinical signs (if any) will occur in humans?

Fasciola hepatica - Severe liver disease; blood-brain barrier leakages and neurological risk in the acute phase [DH] Dicrocoelium dendriticum - usually no clinical signs (bile ducts & gall bladder) [DH] Heterobilharzia americana - "swimmers itch" (abberant host) Nanophyetus salmincola - infection of small intestine (no signs in humans?) Paragonimus kellicotti - eosinophilic meningitis (DH) Alaria sp - Pulmonary hemorrhage

What are the flat worms?

Trematodes = flukes & Cestodes = tapeworms

T/F unless there is severe liver changes, an infected sheep with Dicrocoelium dendriticum is still edible?

True

T/F: in gulf coast states US cattle should be treated before the fall rainy season & again late spring for Fasciola hepatica?

True

Sporocyst

a non-ciliated elongated sac, containing germinal cells, developed from the germinal cells of the miracidia inside the snails' tissues. It has a mouth and a digestive system.

Dicrocoelium dendriticum - diagnosis

based on fecal examination for eggs (flotation or PCR), ELISA (serum) and necropsy findings.

Macracanthorhynchus hirudinaceus - characteristics (egg)

football shaped, multilayered, ornamented shell

Alaria diagnosis

identify large yellow-brown-greenish operculated eggs in feces

Nanophyetus salmincola - characteristics (adult, egg) locations / features

fluke of intestine ("minute") - genital pore is located immediately posterior to the ventral sucker. - The testes lie opposite one another. Adult: located in small intestine of carnivores & humans (via infected fish) Eggs: undevelped when passed in host feces

Fasciola hepatica: eggs characteristics

oval, operculate, yellow and large (150 x 90 um), about twice the size of a trichostrongyle egg.

Fascioloides magna: diagnosis

patent infections (eggs) in deer (rarely cattle, sheep and horses); necropsy

Fascioloides magna: adult characteristics

very large fluke (10 cm), with no anterior cone

Is Macracanthorhynchus hirudinaceus zoonotic?

yes - humans & non-human primates are accidental DH's

Paramphistomum- characteristics (adult / eggs)

"Rumen Fluke" - Adults are small, conical, maggot-like flukes, about 1.0 cm long (pink when fresh) - Oral sucker is situated on the tip of the cone and the ventral sucker at the base. - Eggs - large and operculated like those of F. hepatica, but clear

What disease does Fasciola hepatica cause?

"liver fluke" or Liver rot disease

Fasciola hepatica: adult characteristics (immature, mature, locations)

"liver fluke" or Liver rot disease - Young fluke (or Marita) - is lancet-like and has 1.0-2.0 mm body length; located in the liver parenchyma. Migration through the liver parenchyma causes significant pathology - Mature fluke - is leaf-shaped with a conical anterior end marked off by distinct shoulders from the body, grey-brown, 3.5 x 1.0 cm. The tegument is covered with spines. Located in the bile ducts.

Dicrocoelium dendriticum - characteristics (adult, egg)

'lancet fluke' - (< 1.0 cm long), distinctly lanceolate and semitransparent - 2 branched cecae resembling a tuning fork - The testes lie in a tandem position with the ovary immediately posterior, behind the ventral sucker - No spines on the cuticle - The egg is small (45 x 30 µm), dark brown and operculate, usually with a flattened side. It contains a miracidium and can survive several months on dry pastures.

Heterobilharzia americana - characteristic

- A parasite of raccoon, nutria, bobcat, rabbit, dogs and horses in Louisiana, Florida, Texas, and Kansas (U.S.). - The egg is spherical with a slight bump on one side

Heterobilharzia americana - clinical signs / pathogenesis

- Cercariae may cause "Swimmer's Itch" in humans!! - "canine schistosomiasis": granulomatous lesions (b/c of egg enzymes→hypercalcemia secondary to hypercalcitriolemia or parathyroid hormone-related protein synthesis → metastic mineralization), necrosis - liver dz, intestinal damage, cirrhosis - Chronic weight loss, vomiting, diarrhea, poor body condition

Heterobilharzia americana - diagnosis

- Demonstration of eggs in the feces (flotation or sedmentation): - Radiography & ultrasound (mineralization); - Serology (ELISA) and PCR - Ultrasound and radiology: Faint linear intestinal wall mineralization can be observed on abdominal radiographs, and multiple mineralized irregular foci are often visible ultrasonographically within the pancreas and hepatic parenchyma.

Dicrocoelium dendriticum - clinical signs, pathogenesis

- In older sheep - progressive hepatic cirrhosis & unprofitable (cachexia (chronic wasting), lowered wool production and decreased lactation) - The liver is relatively unaffected by infections with several thousand flukes, presumably due to the absence of a migratory phase. Usually, no clinical signs. - In heavier infections - fibrosis of the smaller bile ducts and extensive cirrhosis; sometimes the bile ducts become markedly distended. - In severe cases - anemia, edema and emaciation, cirrhosis

General characteristics of Fasciola & Fascioloides

- Large leaf-shaped flukes - The anterior end has a shape of cone with the oral sucker located on the end of the cone - The ventral sucker is located at the level of the 'shoulders' of the fluke. - The cuticle is covered in spines - The internal organs are branched

Macracanthorhynchus hirudinaceus - clinical signs

- Pigs may be asymptomatic. Diarrhea, emaciation, abdominal pain, and peritonitis are dependent on the depth of the proboscis in the intestinal wall, secondary (bacterial) infection and inflammation

Paramphistomum - diagnosis

- based on the clinical signs (young animals with a history of grazing around snail habitats during a period of dry weather). - Fecal examination is of little value, as the disease occurs during the prepatent period. - Confirmation by a postmortem examination and recovery of the small flukes from the duodenum

Fasciola hepatica: how do you diagnose?

- based primarily on clinical signs, seasonal occurrence, a previous history of fasciolosis or the identification of snail habitats, and post-mortem examination. - confirm: examination of the feces for fluke eggs (sedimentation technique); detection of coproantigens in cow pats - Routine hematological tests measuring two enzymes (glutamate dehydrogenase - GLDH, and gamma glytamyl transpeptidase - GGT). - Serum and milk for detection of IgG/IgM antibodies against antigens of the fluke (ELISA and the passive hemaglutination test); PCR (feces, tissues); necropsy.

Horse Fasciolosis

- fasciola eggs & occult blood & severe chronic fibrosing cholangiohepatitis w/numerous F. hepatica trematodes @ necropsy

Macracanthorhynchus hirudinaceus - characteristics (adult)

Acanthocephala - thorny headed worm (NOT a fluke) - Large, robust worms resembling ascarids. - pink in color when fresh - body is flattened and becomes cylindrical when placed in water - retractable spiny proboscis by which the parasite attaches itself to the intestinal wall of the host - no digestive tract -- Nutrients are absorbed through the tegument

Clostridium novyi

Black disease - minor liver trauma from a fluke infection can allow C. novyi to invade, multiply & secrete toxins - quick death of sheep

Macracanthorhynchus hirudinaceus - life cycle, DH, IH

DH = swine (small intestine); dogs, fox, squirrels, chipmunks, [humans (zoonotic!) & nonhuman primates = accidental hosts] IH = May beetles (or June bugs), dung and water beetles egg passed in feces of DH → larva developing into acanthor → ingested by beetle (IH) → acanthella stage into encysted infective larva (cystacanth) → can either re-encyst in vertebrate (paratenic host) or DH, or develop to maturity in DH

Fascioloides magna: Life cycle

DH = white-tailed deer and other wild ruminants; F. magna mature in thin-walled fibrous capsule within liver & eggs are voided in feces Aberrant host = ovines; often die of acute disease -- cannot complete migration within host Dead-end host = flukes reach liver, but do not mature (few eggs prouced) & do NOT reach small intestine a.k.a not voided = mouse, bovids, llamas, alpacas IH = snail

Fasciola hepatica: clinical signs / pathology

DH: - pathogenic in lambs, calves → growth retardation, high morbidity & mortality - lower milk production in adults - more pathogenic in sheep, goats, horses - severity depends on if w/ concurrent infection of Clostridium novyi "black disease"

Nanophyetus salmincola - life cycle (DH, IH)

DH: Dog, cat, coyote, red fox, bear, raccoon, raccoon dogs (Brazil), mink and humans get infected by eating salmon or trout containing metacercariae IH: snail, then salmonid fish miracadia need 3 mo to develop in eggs laid in water → hatch spontaneously → penetrate freshwater snail → cercariae develop in rediae → cercariae leave snail & penetrate skin of salmonid fish & salamanders encysting in various tissues as metacercariae → ingestion of 2nd IH by DH → shed undeveloped eggs in feces

Paragonimus kellicotti - life cycle (DH, IH)

DH: cats, dogs and many species of wild mammals (zoonotic - human cases reported - FOOD borne) IH: 1st: snail 2nd: cray fish → can directly infect DH via ingestion 3rd: crab or animals that feed on cray fish miracadia develop in eggs laid in water w/i 2 weeks → hatch & penetrate snail → cercariae develop viaone sporocyst and two redial stages → cercariae leave snail & encyst as metacercariae in crayfish → DH become infected by eating crayfish containing the metacercariae, or eating crabs or animals that have recently fed on crayfish → young flukes migrate to the lungs where they are encapsulated by fibrous cysts connected by fistulae to the bronchioles to facilitate egg excretion via feces

Paragonimus kellicotti - clinical signs, pathogenesis

DH: chronic cough, pulmonary distress, persistent pneumonia. Blood stained sputum. Death may also occur if cysts rupture - Eosinophilic meningitis in humans

Alaria spp. - life cycle, DH, IH

DH: dogs, cats, foxes and mink; adult infects small intestine IH (2): Fresh water snail & Frogs (tadpole) large, unembryonated egg is passed in the feces of the infected DH → In water a miracidium develops and hatches from the eggs (2 weeks) to penetrate a snail → cercariae develop in daughter sporocysts → Cercariae penetrate the skin of a tadpole and transforms into a mesocercariae → tadpole can be eaten by a frog, snake, or mouse (paratenic host) → DH ingests frogs (encysted mesocercariea) → flukes migrate extensively including passage through the lungs before returning to the small intestine (PPP = 3-5 weeks) Zoonotic in humans who eat infected, improperly cooked frog legs!! Mice and cats infected with mesocercariae transmit Alaria marcianae to their young through the milk (transmammary transmission). The sucklings will develop patent infections.

Dicrocoelium dendriticum - life cycle (DH, IH)

DH: humans(rare), sheep, cattle, deer, wapiti and rabbit; located in bile ducts and gall bladder, but sometimes in pancreatic ducts IH (2 required) 1st. land snails 2nd. brown ants Egg hatches after ingestion by 1st IH → 2 sporocyst generations → cercariae → released from snail via slime balls → ingested by ant → cercariae encyst in abdomen, but some go to brain - metacercariae (behavior modification to go high on grass blade) → ingestion by DH → excyst in duodenum → young flukes migrate to bile duct (& cause dysfunction)

Fasciola hepatica: life cycle

DH: most mammals (sheep & cattle); also in goats, horses, humans! IH: mud snails adult fluke produce 3,500 eggs /day (max in spring & noon) → eggs passed in DH feces → in water embryo develops inside egg & hatches (miracidium) -- temp.dependent → quickly find & penetrate tissue of snail → loss of cilia & develops into sporocyst → rediae grow from germinal cells → burst & invade tissue of snail → daughter rediae → cercariae (have long tail) → leave snail into water → attach to vegetation & shed tail/ encyst as metacercariae (survive for months) → ingested by grazing → mastication removed outer cyst wall → inner 1 by small intestine → young fluke (marita) penetrates intestine → liver → in bile duct mature to adult & lay eggs

Heterobilharzia americana- life cycle

DH: raccoon, nutria, bobcat, rabbit, dogs and horses IH: snail miracidium hatches after egg is release into the water and enters a freshwater snail → cercariae develop inside the daughter sporocysts → cercariae leave snail & penetrate the skin of the DH → migrate via lungs to the liver → development in the liver to mature males and females → to the mesenteric veins and mate → lay eggs → eggs passively move through the bowel wall to the lumen and escape with the feces; eggs induce a granulomatous reaction that eventually prevents their escape and favor their carriage to other organs-- with the consequent production and widely disseminated granulomas which may result in tissue alteration and necrosis.

Paramphistomum - life cycle

DH: ruminants; adults located in the rumen and reticulum; immature stages in the duodenum - IH: water snails Miracidia develop in eggs in water → hatch & invade snails → develop 1 sporocyst, 2 redial stages, & cercariae → emerge from snail → encyst as metacercariae on aquatic vegetation → ingested by DH excyst in upper small int & migrate via abomasum to the rumen

Macracanthorhynchus hirudinaceus - diagnosis

Demonstration of eggs in the feces. It is recommended to perform a sedimentation technique because the eggs are heavier than the specific gravity of flotation media.

Alaria spp. - clinical signs, pathogenesis

Heavy infections may cause a severe duodenitis in dogs and cats. Pulmonary hemorrhage has been reported in humans.

Paragonimus kellicotti - Diagnosis

Radiographs will demonstrable cysts ("signet rings") which develop in the lungs at 28 days, and eggs are first shed in the feces about one month after infection. Serology (ELISA) & PCR. - sedimentation of feces or sputum Tx (fyi): praziquantel- highly effective in removing the parasite from the lungs of cats, dogs and coyote. - Fenbendazole - may kill the worms too fast and rupture the nodules. It is recommended to administer lower dose + prednisone (nodules may take as long as 316 days to resolve).

Nanophyetus salmincola - clinical signs, pathogenesis

Rapid onset of diarrhea, lymphadenopathy, fever and death will occur if treatment of doxycyline is not immediately administered (dogs). ( due to bacterium)

Neorickettsia helminthoeca?

Salmon poisoning disease in dogs - this bacterial disease is found within Nanophyetus salmincola - causes hemorrhagic enteritis & lymph node enlargement usually fatal unless treated w/ doxycycline or tetracycline

Humans infection w/ Fasciola hepatica clinical signs

Severe liver disease; blood-brain barrier leakages and neurological risk in the acute phase - diarrhea, eosinophilia, fever, nausea, stomach ache, vomiting

Ovine Fasciolosis

caused by Fasciola hepatica - Acute: liver damage, hemorrhagic anemia, sudden death, dyspneaic, pale mm, ascites, complicated w/ C. novyi concurrent infection - subacute: cholangitis, similar to acute - (most common) chronic: subcutneous edema, hypochromic, macrocytic anemia w/ eosinophilia, hypoalbuminemia, emaciation, pallor, edema, ascites, polydipsia -- pale liver, granuloma-like reaction, hyperplastic cholangitis

Bovine Fasciolosis

caused by Fasciola hepatica Acute & Subacute may occur in calves Chronic: winter/early spring -- similar to sheep + calcification of bile ducts ("pipestem fibrosis"); enlargement of the gallbladder. ⮚ Aberrant migration of flukes may occur and encapsulated parasites are often seen in the lungs. ⮚ Transplacental migration induces prenatal infection of the fetus (rare). In heavy infections, severe anemia and hypoalbuminaemia + submandibular edema, loss of condition, emaciation, dry cough, loss of production in milking cows during winter with reduction in milk yield and quality, particularly of the solids-non-fat component, sometimes abortion.

Cercarie

developed from the germinal cells of the rediae inside the snails' tissues, they are young flukes with long tails, oral and ventral suckers, digestive and excretory systems, and primordial of the reproductive organs. They also have special secretory cells, alongside the pharynx, which secrete the cyst wall of the metacercarie. They penetrate the skin of the mammalian host or encyst on vegetation. these are produced via asexual reproduction

Rediae

developed from the germinal cells of the sporocysts inside the snail's tissues, they have an oral sucker, some flame cells, a simple gut, and germinal cells.

Nanophyetus salmincola - diagnosis

eggs in feces & clinical signs

Metacercariae

encysted cercariae after shedding their tails, in some species, attached to the vegetation. In other spp in the second intermediate host; the infective stage for definitive host.

Schistosomes (blood flukes)

exception -- adult worms reproduce sexually

Fluke eggs

have an operculum (lid) at one pole and contain an embryo.

general Reproductive system of flukes

hermaphrodite exception = schistosomes

Fascioloides magna: pathogenesis / clinical signs

in DH's: deer and cattle, the fluke can cause hepatic trauma when reaching the liver, but it rapidly becomes encapsulated by the host reaction and clinical effects are minimal deer = little pathology cattle = liver damage & economic loss - In sheep = severe liver damage, hemorrhage, necrosis of parenchyma; fatal -- economical losses.

Generalized life cycle of Flukes?

indirect Adult > egg > miracidium > sporocyst > rediae > cercariae > metacercaria > adult.

How do humans get infected with Fasciola hepatica?

ingestion of the metacecariae stage on vegetation

Alaria spp. - characteristics

intestinal fluke - Body divided into a flattened or spoon-shaped forebody (containing the attachment organs), and a cylindrical hind-body (containing the reproductive organs).

Why is fecal sedimentation used?

method of choice for Fasciola, Fascioloides and Paramphistomum fluke egg diagnostics. - EGGs are too heavy for float method - helps find the chronic infections

Acoelomate

no body cavity

Miracidium

pyriform (pair-shaped), ciliated larva with a pair of eye spots, rudimentary nervous and excretory systems, and germinal cells; it does not feed and must find a suitable snail within few hours; infective stage for the intermediate host (the snails)

Paramphistomum - pathogenesis / clinical signs

young flukes → severe duodenal mucosa erosions by feeding; heavy infection → enteritis w/ edema, hemorrhage and ulcerations. -Necropsy: clusters of brownish pink parasites attached to duodenal mucosa and occasionally in the jejunum and abomasum adults are well-tolerated - feeding on the wall of the rumen or reticulum. - In cattle, the outbreaks occur in young stock, as immunity develops after the first episode. - However, adults harbor low burdens of parasites, being an important reservoir of infection for snails. - Sheep and goat are susceptible throughout their lives. - In heavy duodenal infections: diarrhea, anorexia and intense thirst. Sometimes in cattle, there is rectal hemorrhage following a period of prolonged straining. Mortality in acute outbreaks can be as high as 90%.