08. Intestinal trematodes Flashcards
Is Fasciolopsis buski large or small?
large intestinal fluke
Is Heterophyes large or small?
small intestinal fluke
Is Metagonimus large or small?
small intestinal fluke
Is Echinostoma large of small?
small intestinal fluke
name three intestinal/digestive tract flukes
- Fasciolopsis buski
- Heterophyes heterophyes
- Metagonimus yokogowi
What is the largest intestinal fluke of humans?
Fasciolopsis buski
Where is Fasciolopsis buski common?
Asia and the Indian subcontinent - especially in the areas where humans raise pigs and consume freshwater plants
what is the common name for Fasciolopsis buski?
giant intestinal fluke
what is the DH of Fasciolopsis buski?
humans, dogs, pigs, rabbits
what is the first IH of Fasciolopsis buski?
water snail
what is the second IH of Fasciolopsis buski?
aquatic vegetation
what is the infective stage of Fasciolopsis buski?
encysted metacercariae
what is the diagnostic stage of Fasciolopsis buski?
eggs in feces
what is the size of Fasciolopsis buski?
length: 20-75mm
width: 20mm
which adult worm is Fasciolopsis buski similar to?
Fasciola hepatica
what is the difference in the life cycle of Fasciolopsis buski and Fasciola hepatica?
the adults inabit the intestinal tract rather than the liver
what are the common reservoir hosts for Fasciolopsis buski
dogs and pigs
what happens to Fasciolopsis buski after ingestion by the DH
the metacercariae excyst in the duodenum and attach to the intestinal wall
what happens when the metacercariae of Fasciolopsis buski excyst in the duodenum of the DH?
There they develop into adult flukes (20-75mm by 8-20mm) in approx.. 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs)
describe the life cycle of Fasciolopsis buski
1- Unembryonated eggs passed in feces
2- Embryonated eggs in water (embryonate in water)
3- Miracidia hatch, penetrate snail
4- Snail
a. Sporocyst
b. Rediae
c. Cercariae (shed from the snail into the environment)
5- Free-swimming cercariae
6- Metacercariae on water plant ingested by humans or pigs causing infection
7- Excyst in the duodenum
8- Adults in the small intestine
What are human infections of Fasciolopsis buski associated with?
Human infections are associated with eating metacercariae encysted on freshwater vegetation
what are common plants to be infected by the encysted metacercariae of Fasciolopsis buski?
- Common plants: are lotus roots, bamboo shoots and water chestnuts
- In regions in southeast Asia, this is common to eat and if it is not cooked properly you can become infected with F. buski metacercariae
what are the symptoms of infection with Fasciolopsis buski?
- Outward signs of infection are usually the abdominal symptoms (discomfort, nausea, diarrhea) associated with the inflammation of the gut wall caused by the presence of the parasite
- large numbers of flukes may obstruct the flow of the intestine
- Infected individuals may also suffer an immune sensitization caused by the foreign proteins present in the parasite, which presents as fluid build-up (oedema) in the face, abdomen and lower limbs. This occurs in rare cases
how is Fasciolopsis buski diagnosed?
- Microscopic identification of eggs from the feces
- These cannot be distinguished from Fasciola hepatica (unembryonated with distinct operculum)
what is Heterophyes heterophyes?
a very small intestinal fluke
what is the common name of Heterophyes heterophyes?
small intestinal flukes
what is the DH of Heterophyes and heterophyes?
humans, dogs, cats, birds (carnivores - eating fish that is not properly cooked or smoked)
what is the first IH of Heterophyes heterophyes?
fish
what is the infective stage of Heterophyes heterophyes?
encysted metacercariae
what is the diagnostic stage of Heterophyes heterophyes?
eggs in feces
What is the morphology of the eggs of Heterophyes heterophyes?
25-30x15-17µm yellow-brown color tick egg shell inconspicious oprculum embryonated (miracidium inside)
describe the life style of Heterophyes heterophyes
1- Embryonated eggs each with a fully-developed miracidium are passed in feces
2- Snail host ingests eggs, miracidia emerge from eggs and penetrate the snail’s intestine (a, b, c in snail tissue)
a. Sporocysts
b. Rediae
c. Cercariae
3- Cercariae released for snail
4- Cercariae penetrate the skin of fresh/brackish water fish and encyst as metacercariae in the tissue of the fish
5- Host becomes infected by ingesting undercooked fish containing metacercariae
6- Metacercariae excyst in the small intestine
7- Adult in small intestine
How can the DH become infected?
The definitive host becomes infected by ingesting undercooked or salted fish containing metacercariae
What happens after ingestion of the metacercariae of Heterophyes heterophyes? who ingests these?
the DH host ingest the metacercariae
After ingestion, the metacercariae excyst, attach to the mucosa of the small intestine and mature into adults (measuring 1.0 to 1.7mm by 0.3-0.4mm)
how is the diagnosis done for Heterophyes heterophyes?
microscopic identification of eggs from the feces
the eggs are indestinguishable from those of Metagonimus yokogawai and resemble those of Clonorchis and Opisthorcis
what is Metagonimus yokogawai?
a very small intestinal fluke?
what is the common name of Metagonimus yokogawai?
small intestinal fluke
what is the habitat of Metagonimus yokogawai?
small intestine
what is the definitive host of Metagonimus yokogawai?
humans, dogs, cats, canines
what is the first IH of Metagonimus yokogawai?
water snail
what is the second IH of Metagonimus yokogawai?
fish
what is the infective stage of Metagonimus yokogawai?
encysted metacercariae
what is the diagnotic stage of Metagonimus yokogawai?
eggs in feces
what shape is the egg of Metagonimus yokogawai?
ovoid
what is the morphology of the egg of Metagonimus yokogawai?
yellow-brown color
thick egg shell
inconspicuous operculum
embryonated (miracidium inside)
how does the DH become infected with Metagonimus yokogawai?
by ingesting undercooked or salted fish containing metacercariae
other than humans, which fish-eating mammals and other fish-eaters, can become infected by Metagonimus yokogawai?
cats and dogs, and birds
describe the life cycle of Metagonimus yokogawai
1- Embryonated eggs each with a fully-developed miracidium are passed in feces
2- Snail host ingest eggs, miracidia emerge from eggs and penetrate the snail’s intestine
3- Cercariae released from snail
4- Cercariae penetrate the skin of fresh/brackish water fish and encyst as metacercariae in the tissue of the fish
5- Host becomes infected by ingesting undercooked fish containing metacercariae
6- Metacercariae excyst in the small intestine
7- Adult in small intestine
8- Fish-eating mammals and birds can be infected as well (back to 1 in feces)
what happens when the Metagonimus yokogawai goes to the mucosa of the small intestine (pathology)
inflammation
where can the eggs migrate to other than the small intestine?
heart, brain
how is Metagonimus diagnosed?
- microscopid identificaton of the eggs
- The eggs are indistinguishable (somewhat) from those of Heterophyes heterophyes and resemble those of Clonorchis and Opisthorchis
- Specific diagnosis is based on identificstion of the adulk fluke evacuated after anthelminthic therapy, or found at autopsy
what two parasites have the following in common:
- life cycle, pathology, diagnosis, and treatment
Metagonimus yokogawai and Heterophyes heterophyes
what is the geographic distribution of Echinostoma?
worldwide
what is the common name of Echinostoma?
spiny fluke
what is the habitat of Echinostoma?
small intestine
what is the DH of Echinostoma
human, aquatic bird
what is the first IH of Echinostoma?
water snail
what is the second IH of Echinostoma?
clam, snail, leech, fish, or tadpole
what is the infective stage of Echinostoma?
encysted metacercariae
what is the diagnostic stage of Echinostoma?
eggs in feces
what is the disease caused by Echinostoma?
Echinostomiasis
what is observed on the eggs of Echinostoma?
an inconspicuous operculum
how are eggs of Echinostoma passed?
unembryonated in feces
describe the life cycle of Echinostoma
1- Unembryonated eggs passed in feces 2- Embryonated eggs in water 3- Miracidia hatch/penetrate snail 4- In snail tissue a. Sporocyst b. Rediae c. Cercariae 5- Free-swimming cercariae invade second intermediate host 6- Metacercariae in second intermediate host; eaten by humans, aquatic birds, etc. 7- Excyst in duodenum (bird/human) 8- Adults in small intestine
Echinostoma life cycle is similar to _____ except ______
Fasciolopsis; the metacerrcariae excyst in various snails, tadpoles, freshwater fish
describe the pathology of Echinostoma
- Found in the duodenum and jejunum of the small intestine. Causes a chronic inflammation
- Catarrhal inflammation often occurs due to the penetration of the sharp-spined collar into the intestinal mucosa
- In heavy infections, nausea, vomiting, diarrhea, fever and abdominal pain may occur
- Parasite is never life-threatening
How is Echinostoma diagnosed?
microscopic identification of eggs from the feces
Because the eggs are large, careful measurements must be taken to avoid confusion with the eggs of Fasciola of Fasciolopsis. Species-level identification cannot be done based on egg morphology and adults are needed for a definitive diagnosis
what is the treatment for Echinostoma?
praziquantel
what are the two freshwater flukes? (Lac st. Louis)
- Neascus spp. (black spot disease)
- Clinostomum spp. (yellow scrube)
What disease comes about from Neascus spp.? what is this?
black spot disease
- Ironically, theyre actually white. Dark pigment from where the fish encysts the flukes, making them look black.
- Definitive hosts are kingfishers, loons, etc.
- Adult worms live in the loon’s mouth where they produce eggs.
- The eggs are swallowed by the bird, pass through it’s digestive system unharmed and are released into the water with the loon’s feces
- The eggs hatch and enter aquatic sails
- After maturing, they leave the snails and infect fish
what is the yellow or white grub?
Clinostomum spp.
where does Clinostomum spend most of its life?
in the mouth of herons
what does Clinostomum do after leaving the heron?
invades snails and eventually a particular species of snail. Next it burrows into the muscle of a fish
