1. Fascioliasis
Leigh Tyndall
BIOL 402

3. What is Fascioliasis?
WHO has classified it as a neglected tropical disease
Zoonosis –started off as an animal disease and spread to humans
Largely effects the liver, specifically the bile ducts, but can occasionally end up in other random places…this is called ectopic fascioliasis
Still considered a rare disease in humans

4. Fascioliasis is caused by trematode worms
F. gigantica
F. hepatica
Hepatica – mm long and 13 mm wide
Gigantica – mm long and 12 mm wide
Adults are hermaphroditic and can produce thousands of eggs in a day

5. F. hepatica – Europe, America (specifically the south and west), Australia – more temperate areas
F. gigantica – Asia and Africa – more tropical areas (NOTE: this map seems to have gotten it backwards…all my other sources say it’s the other way around)
2.4 million people infected
180 million people are at risk
A lot of cases are probably not reported, especially in Africa (note question marks)
This is mostly in the developing countries, and not developed ones, as a neglected disease, it has largely been eliminated from the developed world and so is largely forgotten in the developing world

6. The Fasciola Life Cycle
Fluke eggs are contained in the feces of the infected organism.
Once it gets into the water by fecal contamination or washed out by heavy rains, the embryo (miracidium) begins to develop (and not before, though it can last for a while in the feces)
The eggs hatch to release larvae (called miracidium)
The larvae have to find a host immediately because they cannot survive longer than 24 hours on their own, so they infect snails (usually the Lymnaea)
Inside the snail, they transform into a sporocyst and migrate to the digestive gland, also known as the liver
when they hatch, they produce larvae (rediae) that are much more active than the sporocyte and so damage the liver considerably more.
Once fully developed into the third stage within the snail liver (cercariae), these organisms then escape inot the water
These cercariae encyst 1-2 minutes to 2 hours onto aquatic plants and develop into metacercariae.
Humans and animals are infected by eating these plants uncooked;
the immature flukes are released from the metacercariae cysts within an hour in the small intestine.
The flukes penetrate the intestinal wall and travel throught the abdominal cavity to the liver
It usually takes the flukes 4-6 days to reach the liver; after they do, the burrow into the liver where they grow in size
7 weeks into the infection, the flukes reach the bile ducts in the liver where they grow and mature into adults
8 weeks into the infection, eggs are found in the bile and then feces of the infected organism
NOTE: the more flukes that infect, the longer it takes them to mature

7. There are several ways to get infected…
raw aquatic plants- ingesting encysted forms of the fluke in water plants (such as raw watercress, water chestnuts, or bamboo shoots).
Drinking water with the unattached larvae in it or eating from dishes to which the larvae have connected
Fecal-oral transmission
Potential human-to-human transmission? (-WHO)
Reservoirs
aquatic plants
Snails (intermediate hosts)
domestic farm animals (pigs, cows, sheep, donkeys, horses, camels, goats etc)

8. There are several ways to get infected…
Fecal-oral transmission
raw aquatic plants- ingesting encysted forms of the fluke in water plants (such as raw watercress, water chestnuts, or bamboo shoots).
Drinking water with the unattached larvae in it or eating from dishes to which the larvae have connected
Potential human-to-human transmission? (-WHO)
Reservoirs
aquatic plants
Snails (intermediate hosts)
domestic farm animals (pigs, cows, sheep, donkeys, horses, camels, goats etc)

9. There are several ways to get infected…
Fecal-oral transmission
raw aquatic plants- ingesting encysted forms of the fluke in water plants (such as raw watercress, water chestnuts, or bamboo shoots).
Drinking water with the unattached larvae in it or eating from dishes to which the larvae have connected
Potential human-to-human transmission? (-WHO)
Reservoirs
aquatic plants
Snails (intermediate hosts)
domestic farm animals (pigs, cows, sheep, donkeys, horses, camels, goats etc)

10. There are several ways to get infected…
Fecal-oral transmission
raw aquatic plants- ingesting encysted forms of the fluke in water plants (such as raw watercress, water chestnuts, or bamboo shoots).
Drinking water with the unattached larvae in it or eating from dishes to which the larvae have connected
Potential human-to-human transmission? (-WHO)
Reservoirs
aquatic plants
Snails (intermediate hosts)
domestic farm animals (pigs, cows, sheep, donkeys, horses, camels, goats etc)

11. There are several ways to get infected…
raw aquatic plants- ingesting metacercariae forms of the fluke in water plants (such as raw watercress, water chestnuts, or bamboo shoots). –
Drinking water with the unattached larvae in it or eating from dishes to which the larvae have connected
And how do the worms get into the water in the first place?
Potential human-to-human transmission? (-WHO)
Reservoirs
Aquatic plants
Snails (intermediate hosts)
domestic farm animals (pigs, cows, sheep, donkeys, horses, camels, goats etc)
Next slide is gross

12. Fasciola (along with most helminths) easily evade the physical barriers to infection
Most physical immune barriers (mucus membranes, skin, gastric acid, body temperature) aren’t effective against Fasciola
- they are ingested usually
- gastric acid helps the worms excyst from the metacercariae

13. Fasciola have evolved several ways to avoid rest of the immune system as well.
First they go to the bile ducts in the liver. Once there, they is safe from any immune response and the liver bile protects any eggs or antigens that might present themselves as they travel away from the liver
Before then: the fluke has a one surface membrane covered by many glycoproteins. The composition of this glycocalyx changes as the fluke develop, most likely because of the changes in environment it goes through and also to present the antibodies with a constantly changing target. In juveniles, this happens every 3 hours or so.
Another theory is that the flukes secrete immunosuppressive proteins that regulate or modify the host immune response but these proteins have not yet been identified.
It could also be that the flukes secrete proteinases that cleave the antibodies sent to catch them

14. In the first phase of fascioliasis, the worms migrate across the liver
Called the acute phase
hemorrhaging and inflammation, fever, abdominal pain, gastrointestinal problems, occasionally coughing and chest pain
Lots of scarring where the migration has occured
Here you can see a lesion that’s migrating across the liver
There is also a latent phase, which is asymptomatic and can last for months or years

15. The chronic phase affects liver function
Chronic phase: can develop months to years after the initial infection
reach bile ducts – can get thickening and calcification of said ducts,
inflammation leads to thickening of ducts and gallbladder,
fibrosis – which is the creation of excess connective tissue in an attempt to heal
eventual blockage due to parasites or parasite fragments which results in biliary colic pain – similar to having a stone in your gall bladder
can also cause jaundice and anaemia
This is why they call it liver rot
It is assumed that humans are not the ideal host, because a lot of the flukes die in the liver parenchyma without reaching the bile ducts.
Very low mortality rate in humans- if they do die (a few cases have been reported) it’s usually because the bile duct is blocked
However, they can die of complications, such as bleeding from the haemmorhaging

16. Fascioliasis is usually diagnosed by finding eggs in the feces
Best test: Detecting eggs in stools is the best but this is difficult and unreliable in humans
- humans are not the ideal host and so flukes may exist but if they don’t grow to maturity, then they won’t release eggs
ultrasound, CT scans and MRI – these are very expensive though
Immunoserological tests(like some of the papers we’ve read) used to find it in your blood

17. Two doses of triclabendazole will treat both stages of fascioliasis
Triclabendazole at 10mg/kg body weight once
“drug of choice. The drug works by binding to the Beta tubulin and therefore preventing the polymerization of the molecule tubulin into the microtubules, which support the cell. This makes movement of secretory vesicles impossible and therefore the fluke can’t renew that glycoprotein coat and keep the integrity of the membrane. Also, the cells can’t move
For humans, the drug is called Egaten
OR bithionol at mg/kg every other day for doses (taken orally); might take two treatments
80-100% chance of being cured!
WHO and Novartis Pharma AG (pharmacy company) have an agreement where countries in need can apply for the drug and will receive it for free

18. There is already resistance to triclabendazole, though…
Resistance in Australia and Ireland
A paper came out in 2006 which showed some thought had gone into this issue, as triclabendazole is currently the only drug available for human treatment.
Think there might be different isotypes of Beta tubulin, In comparing proteins taken from susceptible and resistant flukes shows that resistant flukes have similar beta tubulin protein sequences as beta tubulin in nematodes resistant to their own version of bendazole.

19. Societal Effects
In places with unsafe water, poor sanitation, limited access to basic healthcare
like most of these neglected tropical diseases, once you get it you’re out of commission for a while
Detrimental to animal husbandry
High risk of reinfection because of contaminated pastures and it’s really hard to get rid of an infestation
This is a problem because, as previously mentioned, the methods of diagnosis are either unreliable in humans

20. Several molecules have been looked at as possible vaccines
Fatty Acid Binding Proteins
GST
Capthepsin L
Cerceriae – free-swimming larval stage of a Trematode
Interesting: when lymphoid cells were taken from vaccinated sheep and put into un-exposed sheep, they conferred resistance to infectioion
Irradiated attenuated cercariae and metacercariae
Effective in cattle and rats, not so much in sheep
Found antigens from sera from sheep injected with irradiated metacercariae:
1. Most promising: Fatty Acid Binding Proteins: found by George Hillyer in 1970s – protected from many flukes (including related S. mansoni)
involved in binding and transportation of hydrophobic lipids (bile acids!)
2. GST: glutathione S-transferases – cellular detoxification, found at high levels in all helminth parasites, so presumably it’s important for their survival and therefore a good target
3. Capthepsin L: protease, promotes tissue penetration, aids in acquiring nutrients, immune evasion
NOTE: None of these has been tried in humans

21. Measures should be taken to prevent infection by the flukes
Control of aquatic plant industry
Wash aquatic plants in vinegar
Health Education
Clean water

22. Image References Slides 2 and 3
Wikipedia: (copyright: Flukeman-
WHO:
Water Secrets Blog:
Parasites World:
Slide 4:
Slide 5: Food and Agriculture Organization of the UN: 004/T0584E/T0584E05.gif
Slide 6: CDC website:
Slide 7: Water Aid.org:
Slide 8: Nassau Lake:
Slide 9: Hardwood Bamboo Flooring:
Slide 10:Essentially England:
Slide 11: FAO website
Slide 12: (copyright: Flukeman-
Slide 13:
Slide 14:
Slide 15: (copyright: Flukeman-
Slide 16:
Slide 17:
Triclabenzadole: wiipedia
Vietnamese Institute of Malariology, Parasitology, and entomology quynhon: qn/vn/portal/InfoDetail.jsp?area=58&cat=1174&ID=2809
Slide 18: Tubulin: Brennan GP, Fairweather I, Trudgett A, Hoey E Understanding triclabendazole resistance. Experimental and Molecular Pathology 82:104-9.
Slide 19:
Patients coming for treatment:
Cows:
Cow with flukes
Slide 20: Vaccine:
Slide 21: Market: examiner.com: the-Vietnamese-highlands

23. Sources
Brennan GP, Fairweather I, Trudgett A, Hoey E., et al Understanding triclabendazole resistance. Experimental and Molecular Pathology 82:104-9.
Dalton JP, editor Fasciolosis. New York: CABI Publishing. 544 p.
Hanna REB Fasciola hepatica: Glycocalyx replacement in the juvenile as a possible mechanism for protection against host immunity. Experimental Parasitology 50(1):
UK’s Natural History Museum: day/fasciola-hepatica/index.html
Turkington C, Ashby B Encyclopedia of infectious disease. New York: Facts on File, Inc p.
WHO website: