(trematoes) helminths quiz - microbio II (cls 542)

trematodes (general info)

• Location: liver, lungs, intestines, or blood stream

• Complex life cycle:

  • First intermediate host is ALWAYS a snail

  • Second intermediate host, if present, is usually a fish (or plant)

• Infective stage

  • Larval form found in fish or on plants

blood trematodes are known as what?

schistosomes / schistosoma

• Medically important species

  • Of worldwide concern:

    • Schistosoma mansoni

    • Schistosoma japonicum

    • Schistosoma haematobium

schistosomes (general info)

• Adult flukes live in veins

• Sexual reproduction → two sexes

• Looks like a flat roundworm

  • Think leeches

• Large, non-operculated ova with spines

• Only has 1 intermediate host: snail

schistosoma life cycle stages

• cercariae = infective stage (terror worm)

• miracidium = released from egg & infects intermediate host (second pic)

schistosoma life cycle

1. definitive host passes EMBRYONATED eggs in feces/urine

2. eggs hatch & release miracidia (1-3 weeks)

3. miracidia penetrate snail tissue (snail → cercariae takes 4-6 wks)

4. cercariae released by snail into water (72 hr lifespan)

5. penetrates skin of definitive host (humans)

6. cercariae loses tail and becomes schistomulae in human

7. migrates to portal blood and mature into adults

8. paired worms migrate to mesenteric venules of bowel or venous plexus of bladder

schistomiasis endemic region

• 200-300 million people infected worldwide

  • In Egypt, ~20% of the population is infected, some villages have 85% infection rates

  • Only about 10% of those infected have serious disease

  • Half of the remaining people have symptoms

• In parts of Africa: a rite of male passage into sexual maturity is the development of blood red urine, equated with female menstruation

  • Result of bladder infection

schistosomiasis symptoms/illness

• Serum sickness-like illness

• Marked peripheral eosinophilia → 30-60%

• Circulating immune complexes

  • Eggs are highly antigenic, adult flukes are not

• Acute symptoms resolve over several weeks

  • Bloody diarrhea, cramping, mimics appendicitis

• Adults schistosomes live for years; they coat themselves with host antigens

• Chronic/later stages:

  • Enlargement of liver and spleen, bulging of abdomen, emaciation

 

schistosoma mansoni

aka Manson’s blood fluke

• animal reservoirs: water buffalo

• Lives in portal veins of the intestines and liver

• Causes Bilharziasis

  • AKA hepatosplenomegaly

  • Stunted growth in children

  • Abdominal swelling due to liver enlargement

schistosoma mansoni eggs

• diagnostic stage

• very large, 116-180 x 45-58 um

• Thin, smooth shell

• Indistinct operculum

• Prominent lateral spine

• Embryonated when passed

schistosoma japonicum

• Blood fluke

• Adults found in superior mesenteric veins of the small intestines

• Endemic area: China, Indonesia, Philippines, Sulawesi

  • Eliminated from Japan

• Animal reservoirs

  • Water buffalo

  • Pigs

  • Dogs/cats

  • Wild rodents

schistosoma japonicum egg

• 75-90 x 60-68 um

• Round to slightly oval

• Small, rudimentary, lateral knoblike spine

  • Rarely visible

schistosoma haematobium

• Bladder fluke

• Adults mature in the liver

  • Migrate to venus plexus of bladder

  • Deposit ova in bladder wall

  • Eggs penetrate bladder wall to enter the urine

• Complications

  • Granulomas and pseudo-abscesses

  • Fibrosis & calcification

  • Bladder cancer

schistosoma haematobium egg

• 112-180 x 40-70 um

• Oval

• Prominent terminal spine

• Note developing embryo

• Usually found in urine

food-borne trematodiasis

• Infection occurs through consumption of contaminated freshwater fish, frogs, shellfish, snails, tadpoles, snakes, water plants, and other aquatic products eaten raw/insufficiently washed cooked

• Endemic areas based on presence of intermediate hosts

• Worldwide incidence:

  • Clonorchis sinensis → 35 million

    • Over ½ are Chinese

  • Paragonimus spp. → 20 million

  • Fasciola spp. → 2.4-17 million

  • Intestinal flukes (Fasciolopsis) → 40-50 million

non-blood trematodes

• includes everything else but the schistosomes

• Hermaphroditic (has both male and female organs)

• Flat & leaf-like with ventral suckers

• Divided by where adults live in the human body

  • Live in intestine / liver / lungs

• Have operculated eggs

(non-blood trematodes) clinical manifestations

• Adults do not replicate in the human host

• Morbidity is associated with the worm burden and the infection intensity

  • Eggs / grams of feces

• Inflammatory lesions and damage of tissues and target organs occurs

  • Damage related to worm burden

  • Complications such as cholangiocarcinoma (colon cancer)

(non-blood trematodes) human & economic impact

• Humans: long term, chronic, debilitating diseases

• Economic: loss of meat and milk products due to livestock infection

• Household pets: can be a source of infection and economic burden (treatment costs) to owners

(non-blood trematodes) general life cycle

• have complex life cycles

• Aquatic snails are intermediate hosts

• Up to 6 larval stages

• Alternative sexual and asexual reproduction between life cycle stages

(non-blood trematode life cycle) eggs relase from adult

• Into sputum--for Paragonimus sp

• Into feces for everyone else

• Large number of eggs produced per day

  • Clonorchis sinensis: 1,000-4,000/day for at least 6 months

  • Fasciolopsis buski: 16,000/day

• Eggs are passed unembryonated

  • Need ideal environmental conditions to embryonate

  • Temperature (air & water), moisture, humidity

  • eggs are operculated

(non-blood trematode life cycle) miracidium

• Eggs hatch into miracidium

  • Sac-like larvae

• Attracted by chemotaxis and chemokines to the snails

  • Ingested by snail or penetrate snail skin by boring

• Remain in snail for several weeks passing through various stages

  • Sporocyst, rediae, embryos, cercariae

(non-blood trematode life cycle) second intermediate host

• Young fish (have thinner skin) living in stagnant or slow-moving freshwater

• Highest density of parasite is found in the muscle

• Encysted form is the metacercariae

• Take 1 hour to several months to become infective

  • Depends on the species

(non-blood trematode life cycle) definitive host

• Humans, sheep, cattle, pig, donkeys, beaver, deer, elk, and rabbits/hare

  • Ingest raw, undercooked, or pickled aquatic products

• Gastric juices help with encystation

• Immature adult released

  • Migrates to target organ and matures

• Long life span

(non-blood trematode life cycle) co-infection and reinfection

• Individuals can be infected with multiple trematode species

  • Occurs when endemic areas overlap

• Reinfection occurs rapidly after treatment unless environment issues are addressed

(non blood trematodes) fasciolopsis buski

• Giant intestinal fluke—lives in small intestine

• Largest adult fluke

• Endemic area: Asia, China, India, Indonesia, Taiwan, Thailand, Vietnam

• Reservoir host: dogs, pigs, rabbits

• Intermediate host: snail and fish

fasciolopsis buski egg

• Hard to distinguish between Fasciola hepatica eggs

• 150 x 80 um

• Ovoid, yellow-brown staining

• Thin, smooth shell

• Usually, an indistinct operculum

• Unembryonated, material extends to shell margin

fasciolopsis buski life cycle

1. unembryonated eggs passed in feces

2. embryonate in water

3. miracida hatch & penetrate snail

4. undergoes numerous developmental stages

5. cercariae (terror tadpole) releases from snail

6. metacercariae encysts on water plants

7. water plants ingested by pigs/humans

8. encyst in duodenum of humans

9. adults live in small intestine

(non blood trematodes) fasciola hepatica

• AKA sheep liver fluke

• Worldwide distribution

• Reservoir: herbivores

  • Cattle, sheep, goats etc

• Eggs are identical to Fasciolopsis buski

  • Adults live in small intestine

fasciola hepatica egg

• very large ; 120-159 um x 80-85 um

• looks like F buski; hard to differentiate

• operculum present

• thin shelled

• ovoid & yellow/brown

• unembryonated

fasciola hepatica life cycle

same life cycle as Fasciolopsis buski except for reservoir host (cattle)

1. unembryonated eggs pass in feces

2. embryonate in water

3. miracidia hatch & penetrate snail

4. develops into multiple stages in snail

5. metacercariae release from snail

6. metacercariae lives on water plants (2nd int host) & are ingested by cattle, sheep or humans

7. metacercariae encysts in duodenem

   • metacercariae to adult takes 3-4 months

8. adults live in hepatic biliary ducts

fasciola infections

• Adult worm live in larger bile ducts of liver and gall bladder

• Causes these symptoms:

  • Inflammation

  • Fibrosis

  • Blockage

  • Colic pain

  • Jaundice

  • Eventually liver cirrhosis

(non blood trematodes) Heterophyes heterophyes & Metagonimus yokogawai

• Live in crypts of small intestine

• Asia, Egypt, Turkey, Far east

• Reservoir host: pigs, deer, mice, rats

• No intestinal symptoms unless infection is heavy

• Usually, self-limiting infection

• Must be able to differentiate Clonorchis & Opisthorchis

  • Analyze both eggs and adult worms

Heterophyes heterophyes & Metagonimus yokogawai egg

• 27-35 x 14-16 um

• Urn shaped

• Seated/shoulder operculum

• Small knob on aboperculum end

how to differentiate F buski and F hepatica?

need adult flukes to differentiate genera!!

(non blood trematodes) clonorchis sinensis & opisthorchis sp

aka oriental or Chinese liver fluke

• Found across Asian continent

• Reservoir: Dogs, cats, other fish-eating mammals

• Symptoms vary with worm burden

• These organisms are considered carcinogens

  • Bile duct cancer (cholangiocarcinoma)

clonorchis sinensis & opisthorchis sp egg

• 27-35 um x 11-20 um

• Shouldered operculum & abopercular knob

• Embryonated

clonorchis sinensis life cycle

1. embryonated eggs pass in feces

2. eggs ingested by snail (intermediate host)

3. evolve into multiple stages in snail

   • miracidia → sporocysts → rediae → cercariae

4. free-swimming cercariae encyst in skin/flesh of freshwater fish

5. metacercariae in flesh or skin of freshwater fish ingested by definitive host

   • 2nd int host; metacercariae in fish is infective stage

6. excyst in duodenum (human)

7. adults live in biliary duct of definitive host

clonorchis & opisthorchis infections

• Adult flukes live in the smaller bile ducts of the liver

• Symptoms:

  • Inflammation

  • Fibrosis

  • Non-specific gastrointestinal symptoms

  • Chronic infection can lead to cholangiocarcinoma

    • Bile duct cancer

(non blood trematodes) paragonimus sp

• Lung flukes…cough

• Worldwide distribution but species have specific endemic areas

• Second intermediate host: crustaceans (crayfish/crawdads, crabs, snails)

• Reservoir host: dogs & cats

• Eggs found in sputum and sometimes feces

  • Host coughs them up and swallows them

• Disease can be confused with TB

species of paragonimus

• >40 different species

• Primary pathogenic species:

  • P westermani—most common; primarily in Asia

  • P africanus—Western & Central Africa

  • P mexicanus

    • Central & South America

    • What we have in lab!

  • P kellicotti

    • North America

    • Well known pathogen of wild & domestic animals

paragonimus sp life cycle

1. unembryonated eggs pass in sputum

2. embryonate in water

3. miracidia hatch and penetrate snail

4. miracidia → cercariae (3-5 mo)

5. cercariae invade crustacean and encyst into metacercariae

   • cercariae → metacercariae takes 6-8 wks

6. humans ingest inadequately cooked or pickled crustaceans containing metacercariae

7. humans pass eggs in sputum / feces

8. encyst in duodenum but migrate to lungs; mature adults take 5-6 wks

paragonimus infections

• Symptoms

  • During larval migration--fever, malaise, diarrhea, epigastric pain

  • Once in lungs: pleuritic chest pain, pleural effusions (contain eosinophils), pneumothorax

    • Chest pain, dyspnea, cough, malaise

  • Chronic infections--mature adults in the lungs

    • Lung inflammation and fibrosis

    • Chocolate colored sputum

    • No fever or peripheral eosinophilia

paragonimus sp egg

• All species have basically same morphology

  • 80-120 x 48-60 um

  • Shaped like a chicken egg

  • Dark yellow brown

  • Thick smooth shell

  • Prominent shouldered operculum

  • Thickening of abopercular end

paragonimus kellicotti

• 2008 – 2017 13 cases in Missouri

  • 6 more cases elsewhere in the Mississippi drainage basin

  • 2017 – 3 cases of eosinophilic encephalitis reported in Missouri

• Patients had consumed raw crayfish from streams and rivers

• Only 7 cases reported in entire USA through 2007

  • All in the Midwest

paragonimus kellicotti egg

paragonimus kellicotti life cycle (pic)

how do we diagnose trematode infections?'

• direct exam diagnosis

• immunodiagnosis

• molecular methods

(diagnosing trematode infections) direct exam diagnosis

• Look for eggs in stool, sputum, or other body fluids

• AKA ova and parasite exam

• Limitations:

  • Low numbers of eggs released

  • Difficulty in speciating with just eggs, sometimes need an adult worm to entirely sure (Fasciolopsis buski & Fasciola hepatica!!!)

(diagnosing trematode infections) immunodiagnosis

• Indirect diagnosis

  • Intradermal tests

  • Indirect hemagglutination assays

  • Indirect fluorescent antibody tests

  • Indirect EIA tests

• No really good tests

• A lot of cross reactivity

• Intradermal test remain positive years after successful treatment

(diagnosing trematode infections) molecular methods

• PCR based methods look for DNA of eggs in fecal sample

• Very sensitive and specific

• Expensive & need lots of resources

  • Used by US military

• Complementary tools

  • Ultrasound

  • CT scan

  • MRI

answer the following about s mansoni / japonicum:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• egg is shed from the human; humans acquire by direct skin penetration

• embryonated

• n/a

• miracidia (s mansoni)

answer the following about s mansoni / japonicum:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate: snail ; reservoir: water buffalo / pigs/dogs /cats/rodents

• infective stage: cercariae

• direct skin penetration

• cercariae become schistomulae and migrate to liver

• adults (paired worms) live in mesenteric venules of bowel/rectum

answer the following about s haematobium:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• embryonated egg ; no larvae

• miracidium hatches from egg

• (s haematobium)

answer the following about s haematobium:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate host: snail ; reservoir: none

• infective stage: cercariae

• direct skin penetration

• cercariae → schistomulae → portal blood in liver

• adults → venous plexus of bladder

answer the following abt f buski:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• unembryonated egg shed in feces ; no larvae

• miracidia hatch from egg

answer the following abt f buski:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate: snail ; reservoir: pigs

• infective stage: cercariae (terror tadpole) / metacercariae

• humans ingest water plants w metacercariae

• excyst in duodenum

• adults: small intestine

answer the following about f hepatica:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• unembryonated eggs passed in feces ; no larvae

• miracidia hatch from egg (f hepatica)

answer the followng abt f hepatica:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate: snail & water plants ; reservoir: cattle/sheep

• infective stage: cercariae / metacercariae

• humans eat contaminated water plants

• excyst in duodenum

• adults: hepatic biliary ducts

answer the following abt c sinensis:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• embryonated eggs passed in feces ; no larvae

• eggs ingested by snail and then hatch into miracidia → sporocysts → rediae → cercariae (c sinensis)

answer the following abt c sinensis:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate host: snail & freshwater fish ; reservoir: dogs/cats, fish-eating mammals

• infective stage: metacercariae in fish

• humans eat freshwater fish contamined w the parasite

• excyst in duodenum

• adults: biliary duct

answer the following abt paragonimus sp:

• What form is shed/acquired from the human?

• If, an egg, is it embryonated or not?

• If it is a larvae, what kind of larvae?

• What hatches from the egg?

• unembryonated eggs in feces/sputum ; no larvae

• miracidia hatch from eggs (paragonimus)

answer the following abt paragonimus sp:

• intermediate host? reservoir host?

• What is the infective stage that gets back into the human?

• How does the infective stage get back into the human?

• General info about what happens once it gets back into the human.

• Where do adults live?

• intermediate host: snails/crustaceans ; reservoir: dogs/cats

• infective stage: metacercariae

• humans eat infected crustaceans w metacercariae

• excyst in duodenum & travel to lungs to lay eggs

• adults: lungs