Parasitology 12 Trematodes/Flukes

Hermaphroditic tissue fluke morphology

Leaf-shaped, oral/ventral suckers, blind GI tract

Sheep liver fluke

• intermediate host: snail

Fasciola hepatica

Intestinal fluke

• first intermediate host: snail

• second intermediate host: pig

Fasciolopsis buski

Liver fluke

• first intermediate host: snail

• second intermediate host: fish

Clonorchis sinensis

Lung fluke

• first intermediate: snail

• second intermediate host: crabs

Paragonimus westermani

How do humans get infected by hermaphroditic flukes?

Eating metacercariae of second intermediate host

Treatment for all hermaphroditic flukes?

Praziquantel

T/F: Hermaphroditic flukes do not multiply, so burden depends on inoculum

True

What species cause fascioliasis: bile duct block (gallstone disease) and possibly liver damage?

Fasciola hepatica, Fasciola gigantica

What is and is not effective against Fascioliasis

Triclabendazole

NOT Praziquantel

How do Fasciola spp. develop in snail tissue?

Sporocysts → rediae → cercariae

Fasciolopsiasis

• what species causes it

• symptoms

• associations?

Fasciolopsis buski

• ulcers, diarrhea, toxic reactions

• ingestion of water chestnuts or fresh-water plant-fed animals

Fasciola hepatica distribution (areas with what animal)

• areas with sheep/cattle

• Europe, Middle East, Asia

F. gigantica distribution

Asia, Africa, Hawaii

Fasciolopsis buski distribution (areas with what animal)

• areas with pigs

• China, Taiwan, SE Asia, Indonesia, Malaysia, India

Where are metacercarial cysts found for Clonorchis sinensis

uncooked freshwater fish

Diagnosis of Clonorchis sinensis

• eggs in stool or duodenal aspirate

• egg with operculum and shoulders

T/F: When bile duct is obstructed, eggs in stool are not excreted

True

Diagnosis of Fasciola spp.

• eggs in stool (big)

• egg with operculum

Clonorchis distribution

Asia (SE Asia, South Asia) and non-endemic areas

How do Clonorchis develop in snail

Miracidia → Sporocysts → Rediae → Cercariae

Clonorchis disease

• asymptomatic often

• inflammation, intermittent obstruction of biliary ducts

• acute: abdominal pain, nausea, diarrhea

• chronic: cholangiocarcinoma

Clonorchis treatment

praziquantel or albendazole

Paragonimus westermani distribution

Asia/SE Asia, India, Africa

How is paragonimus westermani transmitted?

eating metacercariae cyst from undercooked crab meat

What fluke causes granulomatous reaction leading to fibrosis?

P. westermani

Symptoms Paragonimus westermani

cough, pleurisy, pulmonary pain, hemoptysis

Diagnosis of P. westermani

• eggs in sputum, rarely in feces

• brown eggs

• operculum

How do P westermani develop in snails?

Sporocyst → Rediae → Cercariae

Where do cysts excyst in?

Duodenum

Paragonimus westermani eggs exit where?

sputum

What free-living amoeba causes primary amoebic meningoencephalitis?

Naegleria fowleri

What free-living amoeba causes granulomatous amoebic encephalitis

Balamuthia mandrillaris

Acanthamoeba spp.

What free-living amoeba cause keratitis

Acanthamoeba spp.

What species enter through offactory neuroepithelium?

Naegleria fowleri

What species enter through lower respiratory tract or through ulcerated skin?

Acanthamoeba spp. and Balamuthia mandrillaris

What species does this cyst, flagellate, and trophozoite belong to?

N. fowleri

Acute primary amebic meningoencephalitis

• cause?

• symptoms?

• who affected?

• enter how?

• Naegleria fowleri

• severe headache + meningeal signs; fever, vomit, neurological deficit

• immunocompetent kids and young adults

• contaminated fresh water

• enter brain via olfactory mucosa

Granulomatous amebic encephalitis

• cause

• symptoms

• who affected

• enter how

• Acanthamoeba or Balamuthia spp

• headaches, neurological deficit, altered mental status

• immunisuppressed people

• hematogenous spread from respiratory tract or ulcerated skin

• can be fulminant

What is this

Granulomatous amebic encephalitis

Keratitis

• caused by

• symptoms

• risks

• Acanthamoeba spp.

• corneal ulcers

• contact lens users more at risk if poor hygiene

Naegleria diagnosis

• CSF wet mount of giemsa stain

• usually autopsy

Acanthamoeba/Balamuthia diagnosis

• stained smear of biopsies (brain, skin, cornea)

• corneal scrapings

Do N. fowleri form cysts in human tissues?

No

What is this

N. fowleri trophozoite

What is this

N. fowleri trophozoite

What is this?

N. fowleri trophozoite

What is this?

• can be found in brain, skin, eyes, lungs

Acanthamoeba cysts

What is this?

• no flagellated

• pleomorphic

Acanthamoeba trophozoites

What is this?

Balamuthia mandrillaris cyst

What is this?

• no flagellated

Balamuthia mandrillaris trophozoite

Treatment for N. fowleri? Is it successful?

IV + amphotericin B in large doses; people rarely survive

Why is it that almost no one survives GAE?

• Acanthomeba spp and Balamuthia are resistant against amphotericin B