Parasitology exam 2 review - pt 2? Trematodes? and some review q's

What are the two subclasses of class Trematoda (flukes)? Which one do veterinarians focus on/which is important for us?

subclass Monogenea and subclass Digenea. Digenetic flukes are usually what we focus on in vet med becayse they are the ones that parasitize domestic, and wild animals, and humans.

How would you describe a Trematode/some characteristics?

Trematodes are dorsoventrally flattened, unsegmented, and leaf-like parasites.

Flukes, or digenetic trematodes, do not possess an anus. They regurgitate their cecal contents back into the tissues or organs of the host upon which they have fed.

no sense organs, have 2 suckers, no GI tract

With the exception of the schistosomes, or blood flukes, all flukes are hermaphroditic; that is, each fluke possesses a complete set of both male and female reproductive organs.

What is the life cycle of the fluke?

● Fluke’s produce eggs that exit from the uterus through the genital pore, which is usually  passed out through the host's feces.

● If the egg makes contact with water, it will hatch and produce a motile stage called a miracidium. The miracidium swims using cilia to find an aquatic snail, which it penetrates through the skin and develops into a sporocyst.

● The sporocyst is just a sac where the next stage develops.

● The redia is the next stage and within the redia the cercaria develops.

● The Cercaria often has a tail and emerges from the snail and swims in the water.

From this point on, depending on the species the cercaria will go one of three ways.

1. It might directly penetrate the skin of the definitive host.

2. It might attach to vegetation, lose its tail, surround itself with a thick cyst wall, and then

develop into metacercaria. Then the metacercaria will be eaten along with the

vegetation by the definitive host.

3. Or it might lose its tail, penetrate a second intermediate host, surround itself with a thick

cyst wall, and then develop into a metacercaria. This metacercaria would then be

ingested with the second intermediate host by the definitive host.

What are the flukes of ruminants? (Cattle, sheep, goats, deer, etc).. 

Dicrocoelium dendriticum, Paramphistomum spp. and Cotylophoron spp., Fasciola hepatica, and Fascioloides magna. 

What are the flukes of small animals (What animals are they in dogs or cats)?

Platynosomum fastosum (cats), Nanophyetus salmincola (dogs), Heterobilharzia americana (dogs), Alaria spp. (dogs and cats), Paragonimus kellicotti (dogs and cats).

What are schistosomes?

Blood flukes.

Where do most flukes live and what is the exception? 

Most live in the intestinal tract, with only two exceptions (the lung fluke and the blood fluke.) 

What is the lung fluke- what animals does it affect, IH’s? 

Paragonimus kellicotti. it affects dogs and cats. 1st IH: aquatic snail, 2nd IH: crayfish. 

What is the blood fluke (Schistosome) - what animal does it affect, IH’s, what is unique about it from other flukes? 

Heterobilharzia americana. It affects dogs. IH is the aquatic snail, and it does not have a 2nd, the metacercariae enters directly through the dogs skin. This fluke has separate sexes of worms instead of the worm having both sexes in one worm. It is NOT hermaphroditic.

What 2 flukes are the only fluke that has a land snail as its IH?

Platynosomum fastosum (2nd IH is the lizard), and Dicrocoelium dendriticum (This worm has the ant as its 2nd IH.)

How are the ova of flukes similar?

• Large, oval, operculated (“lid” on one end)

• Golden brown or yellowish

• Heavy → they don’t float well (diagnosed by sedimentation)

• Contain miracidium (larval stage) when embryonated

What are the liver flukes? - DH?

Fasciola hepatica - DH ruminants

• “common liver fluke” of ruminants (sheep, cattle, goats).

  • Can contribute to black’s disease

Fascioloides magna - DH is white tailed deer!

• “giant liver fluke” of deer (aberrant infection in cattle, sheep).

How can you prevent liver flukes in ruminants?

Control snail population (the intermediate host 🐌).

Keep livestock away from wet, marshy areas.

Deworm with appropriate anthelmintics (e.g., triclabendazole).

What is “Black disease”? 

Caused by the bacterium Clostridium novyi type B. The spores of C. novyi can remain dormant in the liver until something creates a low-oxygen (anaerobic) environment—this is where liver flukes come in. The liver fluke (Fasciola hepatica) migrates through the liver tissue, causing damage and necrosis (tissue death). These damaged, oxygen-deprived areas of the liver allow Clostridium novyi spores to germinate. Once active, the bacteria release powerful toxins that cause massive liver necrosis and systemic toxemia—leading to rapid death.

Trematodes almost always have who as an IH? What is the mollusk?

Snails!

• Mollusk are soft bodied invertebrates like slugs

• Some species have a 2nd IH, like fish, crab, amphibian

Drugs to treat Cestodes, Trematodes, Rickettsia? 

Cestodes: Praziquantel

Trematodes: Febendazole, Praziquantel

Rickettsia: Antibiotics like Tetracyclines, or Chloramphenicol if Tetracyclines are contraindicated.

What is the most common small animal fluke?

For dogs: Nanophyetus salmincola

For cats: Platynosomum fastosum

Salmon poisoning fluke carries what organism?

The adult fluke inhabits the small intestine and serves as a vector for rickettsial agents that produce “salmon poisoning” and “Elokomin fluke fever” in dogs. Neorickettsia helminthoeca → causes Salmon Poisoning Disease in dogs (fatal if untreated).

What is the biggest fluke? What is the smallest?

The biggest fluke is Fascioloides magna. The smallest is Nanophyetus salmincola. 

Schistosoma spp - IH and DH?

• IH: fresh water snails

• DH: humans and birds and then Heterobilharzia americana is in dog

Fasciola spp. IH and DH?

• IH: 1st: aquatic snail; 2nd: none; cercariae encyst on aquatic vegetation

• DH: Ruminants

Echinococcus spp - IH and DH?

• IH: Sheep, cattle, humans, and other herbivores (E. granulosus)

  • Known as the smallest tapeworm (fewest segments) + zoonotic

• DH: Dogs (E. granulosus)

  • IH: rats, mice, humans and voles

• DH: Cats (E. multilocularis)

Paragonimus spp - IH and DH?

• 1st IH: snail

• 2nd IH: crayfish

DH:  Dogs and cats

Another life cycle of trematode but short?

• Egg (passed in feces; operculated)

• Miracidium hatches → penetrates snail (1st IH)

• In snail: sporocyst → redia → cercaria

• Cercaria leaves snail → encysts on vegetation or 2nd IH as metacercaria

• Definitive host eats vegetation or IH → adult fluke in organ (usually liver, lungs, or intestines)

How would you diagnose a fluke?

Fecal exam, Fecal sediment, antigen tests, PCR, necropsy (usually definitive diagnosis).

Which Taenia spp. are zoonotic? - How/transmission, IH and DH? 

• Taenia solium 

  • Pork measles (cysticercus cellulosa in larval stages

  • IH: pigs

  • DH: human

    • Transmitted by ingesting undercooked/raw pork

• Taenia saginata

  • IH: cattle

  • DH: humans

    • Transmitted by ingestion raw / undercooked beef

Life cycle of Dipylidium? (Think of tapeworm life cycle)…

Egg ➜ larvae of flea IH ingests egg packet ➜ Oncosphere ➜ Cystercercoid ➜ Adult worm and then infects DH

Life cycle of Taenia? Think of life cycle of tapeworm? 

Eggs / gravid passed in feces ➜ gravid proglottids dry up + release eggs ➜ eggs w/ hexacanth embryo ingest by mammal IH ➜ hexacanth embryo matures to cysticercus, coenurus, or hydatid cyst ➜ DH ingests IH containing metacestode stage ➜ metacestode stage attaches in intestine mucosa + matures to adult fluke ➜ Adult worm

Life cycle of Fasciola hepatica? Think of Trematode life cycle.

egg ➜ miracidium ➜ sporocyst ➜ rediae ➜ cercariae ➜ metacercariae.

Describe the eggs of flukes

• Digenetic flukes

  • Oval + large

  • Single operculum

Heavy and don’t float

Describe a cestode

Flat

Segmented

Ribbon like

Describe Monezia sp. Eggs

Usually angular (triangle / rectangle ) shape

Typically have a pryiform apparatus

Drugs to treat Taenia pisformis?

(Fluke) = Droncit (Praziquantel)

• Used in 4 wks or older - treats tapes 

  • Dipylidium caninum (IH: flea)

  • Taenia pisiformis (IH: rabbit)

  • Echinococcus granulosus (dog tapeworm)

Drug to treat Paragonimus kelliscoti (lung fluke dog + cat)?

Fenbendazole (Panacur)

Treats rounds, hooks, whips, and tapes

Drug to treat Fasciola hepatica (Cattle liver fluke)?

Triclabendazole (Valbazen)

Drug to treat Neorickettsia heminthoeca ( Causes salmon poisoning NOT the fluke)?

Doxycycline

Can treat most tick-borne Rickettsia infections w/ tetracyclines

Drug to treat coccidia?

Albon (Sulfadimethoxine) 

The hydatid cyst is the intermediate stage of what cestode?

Echinococcus granulosus

Taenia saginata causes what disease in the intermediate host?

Cattle measles

Cysticurcus celluloasae is the intermediate form of what parasite?

Taenia solium

Finding an ova in a fecal floatation from a patient that cannot host the adult parasite is called what type of infection?

Spurious

The most common intermediate host of Teanea pisiformis is? (Think hunting dog)

Rabbit/Hare

Tapeworm with ruminant as the definitive host?

Moniezia

Lyme’s disease us caused by what?

Borrelia burgdorferi

What liver fluke causes “blacks’ disease” in cattle?

Fasciola hepatica

The most common intestinal fluke of dogs, cats, foxes, and mink in the US; non-pathogenic

Alaria spp.

Worm-like fluke that inhabits blood vessels (often portal veins) of several different species?

Schistosoma

Smallest tapeworm (fewest segments) and is zoonotic?

Echinococcus

The snail lymnaea spp. is required intermediate host for?

Fasicola hepatica

Tapeworm of dogs which may cause CNS signs in sheep when they are the intermediate host

Multiceps (Taenia) multiceps

Ancanthocephalan that affects dogs

Oncicola canis

Which of the following life stages do not apply to the trematode

Cysticercus

Ova have hooklets and mammals as intermediate host

Taenia spp.

Ova have radial striations and an angular shape

Monezia spp.

Mice are the DH of this unique fluke? Tape? Common name?

Hymenolepsis spp. DWARF tapeworm!

Ova are found in lung secretions/sputum

Paragonimus spp.

Fish are intermediate hosts of this (wanna be tape). 

Diphyllobothrium spp.

Diffferent metacestodes and IH? 

CysticercoidInsect IH

CysticercusMammal (Taenia) IH

CoenurusMulticeps sp. (ovine/rabbit IH)

Hydatid CystEchinococcus sp. (3 rd segments)

Tetrahydium Mesocestoides sp. (hundreds of larvae inside ovaasexual reproduction multiply)