Platyhelminthes (Digeneans, Monogeneans, Cestodes)

Quiz 3 + Test 3

Platyhelminthes

-Has acoelomate

-Bilateral symmetry

-Definite anterior end

-Flattened dorso-ventrally (with exceptions)

-Hermaphroditic (with exceptions)

-Tegument (covers surface of worm)

Digeneans

Trematodes

Digenean

-Type of Platyhelminth

-Consists of flukes

-Polyembryony>sporocysts>cercariae

-Eggs have miracidium

-Sporocysts have rediae

Liver flukes

Consists of:
1) Fasciola

2) Dicrocoelium

3) Clonorchis

Liver flukes

These flukes infect the bile ducts. Larvae move through the lumen/tissue.

Fascioliasis (Liver rot)

What disease does Fasciola hepatica cause?

Ruminant (cow/sheep)

What is the definitive host for Fasciola hepatica?

Snail 

What is the intermediate host for Fasciola hepatica?

Fasciola hepatica

What parasite has this life cycle?

Accidental host

What do humans serve as in the life cycle of Fasciola hepatica?

Acute Fascioliasis

-Pre-adult migration

-Large number of metacercariae at once

-Hemorrhagic tracts and inflammation

-Sudden death during pre-patent period (~8 weeks)

-No clinical symptoms

Chronic Fascioliasis

->12 weeks

-Ingestion of moderate amount of metacercariae

-Damage in liver

-Fibrosis, blockage, inflammation

-Leads to anemia, “bottle jaw”, and progressive weakness

Dicrocoeliasis

What disease does Dicrocoelium dendriticum cause?

Dicrocoelium dendriticum

Parasite is also called little liver fluke/lancet fluke.

Dicrocoelium dendriticum

What parasite has this life cycle?

Dicrocoeliasis

-Uses common bile duct

-Duct becomes inflammatory

-Pathology is burden-dependent

-Granulomas/cirrosis

Clonorchis sinensis

Parasite also known as human liver fluke.

Clonorchiasis

What disease does Clonorchis sinensis cause?

Clonorchis sinensis

What parasite has this life cycle?

Cats

What can act as a reservoir host for Clonorchis sinensis?

Clonorchiasis

-Symptoms depend

-Pathogenesis: mechanical damage of the liver due to movement of worm

-Excretory-Secretory products>mitogenic>hyperplasia

-Immune-mediated

-Creates environment for cancer development

Heterophyes heterophyes

What parasite has this life cycle?

Heterophyiasis

What disease does Heterophyes heterophyes cause?

Heterophyiasis

-Ectopic infection in brain, lymph nodes, and myocardium

-Diarrhea and abdominal pain

-In Philippines, 15% myocardiatic

Ribeiroia ondatrae

What parasite has this life cycle?

Ribeiroia ondatrae

This parasite has an additive effect with pollution and causes frogs to grow additional limbs.

Blood flukes

Consists of:

-Cardicola

-Schistosoma

-Trichobilharzia

Blood flukes

These flukes are endoparasites that live in the circulatory system. They release eggs through blood vessels and create granulomas.

Schistosoma spp.

What parasite has this life cycle?

S. mansoni

This species of Schistosoma:
-Lives in mesenteric veins that connect to large intestine (eggs shed in feces)

-RH=Monkeys and rodents

-Range:Africa, Caribbean, South America

S. japonicum

This species of Schistosoma:

-Lives in mesenteric venules that connect to small intestine (eggs shed in feces)

-RH=Horses, dogs, cats, etc.

-Range=Asia

S. haematobium

This species of Schistosoma:
-Lives in veins of urinary bladder and uterus (eggs shed in urine)

-No RH

-Range=Africa

Gastropods

Immune evasion in ________:

-Immunosuppression

-Molecular mimicry of host antigens

Vertebrates

Immune evasion in ________:

-Eggs use granulomas to survive and move through walls of gut via degradation of host tissues to exit

Schistosomiasis

What disease does Schistosoma spp. cause?

Migratory phase

What disease phase of Schistosomiasis is being described below:

-Penetration of cercariae

-Cutaneous allergy to parasite’s products (hives, dermatitis)

-Migration of schistosomules to lung capillaries

-May be asymptomatic

Acute phase

What disease phase of Schistosomiasis is being described below:

-Maturation of parasite

-Oviposition

-Can be asymptomatic or symptomatic

-Signs include fever, diarrhea, prostration

-Immune response

Chronic phase

What disease phase of Schistosomiasis is being described below:

-Cell mediated response to eggs creates granulomas

-Can cause fibrosis, hepato-splenomegaly, ascites

PZQ, yes

What is the only drug available for Schistosomiasis? Is there resistance?

Cercal dermatitis (Swimmer’s itch)

What disease is being described:

-Humans serve as unsuitable definitive hosts

-Penetrates skin and creates itching rash

-Present throughout the world

Haptor

What is the morphological feature for Monogeneans?

Gyrodactylus spp.

All Monogeneans are oviparous, except for which spp.?

Oncomircidium

What life cycle stage is unique to Monogeneans?

Monogeneans

Consists of:

-Dactylogyrus spp.

-Gyrodactylus spp.

-Diplozoon spp.

Polystomes

Consists of:
-Pseudodiplorchis americanus

Dactylogyrus spp.

-DH=Freshwater or marine fishes

-Distrubution=Worldwide

-Habitat=Gills

-Pathogenesis=Mucus on gills, acute infections (short period of dyspnea)

-Oviparous

Gyrodactylus spp.

-DH=Salmon, eels, etc.

-Habitat=Skin, gills, fins

-Pathogenesis=Mucous, epithelium

-Ovoviviparous

Diplozoon spp.

-Fused adults (two diporpa fuse into 1 adult)

-DH=Cyprinid fish (freshwater)

-Habitat=Gills

-Distribution=Europe, Africa

Pseudodiplorchis americanus

-DH=Spadefoot (desert) toad

-Habitat=Urinary tract

-Life cycle of parasite is synced with host’s

-Oncomiracidium live in lungs/respiratory system when host is a tadpole, then migrate to urinary tract as host becomes an adult frog

Monogenean

-Type of Platyhelminth

-1 oral sucker

-Blind bifurcated intestine

-Monoxenous

-Oviparous (with exception)

-Hermaphroditism

Cestode

-Type of Platyhelminth

-All mesoparasites

-All intestinal worms as adults

-All parasitic

-DH=Vertebrates

-Habitat=Intestinal

-No digestive tract

Scolex

What is the morphological feature of cestodes?

Cestodes

Tapeworms

Proglottid

What is the segments of a tapeworm called?

Coracidium

Free-living hexacanth (only in aquatic species)

Humans

These parasites infect who? :

-Taenia saginata 

-Taenia solium

Animals (Zoonosis)

These parasites infect who? :

-Echinococcus granulosus

-Diphyllobothrium latum

-Diphyllobothriid spp.

Taenia saginata

This Taenia spp. uses a cow as its intermediate host.

Taenia solium

This Taenia spp. uses pigs as its intermediate host.

Taenia spp.

What parasite has this life cycle?

Taenia solium

What Taenia spp. causes Cysticercosis?

Taeniasis

-Caused by ingesting raw or undercooked meat

-Can be asymptomatic or symptomatic based on burden

-Passage of migrating proglottids

Cysticercosis

-Caused by humans ingesting eggs of parasite

-Humans act as accidental, unsuitable “intermediate” hosts

-Cysticerci develop in brain and lead to neurocysticerci

-Re-emerging disease

Diphyllobothrium latum

-DH=fish-eating mammals

-Broad fish tapeworm

-Two IHs

-Stages include procercoid and plerocercoid

Intermediate/Paratenic host

What do humans serve as in the life cycle of Diphyllobothrium latum?

Diphyllobothriasis

What disease does Diphyllobothrium latum cause?

Diphyllobothriasis

-Can be asymptomatic

-Vague abdominal discomfort

-Diarrhea

-Avitaminosis B12 (pernicious anemia)

Diphyllobothrium latum

What parasite has this life cycle?

Sparganosis

-Caused by drinking water contaminated with infected copepods

-Zoonosis disease

-Caused by migrating sparganum

-Can be cutaneous or cerebral

-Inflammation

Echinococcus granulosus

What parasite causes hydatid disease?

Echinococcus granulosus

What parasite has this life cycle?

Intermediate hosts

What do humans serve as in the Echinococcus granulosus life cycle?