Ectoparasites &Endoparasites Search the Web for Parasitology Submit or review link Author's Teaching Author's Research Home Page

              Ectoparasites and Endoparasites               

     The Fasciola Home Page

                   Learn about the Liver fluke from Dr. Clive Bennett     More pictures          Diagnostics page                Back to the index Page of  'Ectoparasites and Endoparasites'  

Where do you want to start? A life cycle diagram? The morphology of life stages are in the tables 1-7 below. Find out more about sex and survival of Fasciola hepatica

A life cycle with two hosts. How could that have happened? Read what I have to say on a parasite intricately adapted to survive in two hosts and twice in the outside world.

Learn about a parasite INSIDE and OUT with lots of state of the art pictures of the various stages of its cycle as I also undo the myths about liver flukes:

That they are boring, have an inexplicable life cycle with two hosts and an inert outer cuticle that neither metabolises or does anything to avoid the host's immune defences.

Links to general Fasciola sites are at the foot of the page. They include epidemiology and control: drugs, pharmacology, biochemistry, neurotransmitters and genetics.

Click on GOTO, where it appears below, to go to my original diagrams of internal structures. Link to other Fasciola species   Link to molluscan hosts of F. hepatica

                                                                                THE ADULT LIVER FLUKE: Fasciola hepatica

Fasciola hepatica is the causative agent of Fascioliasis (Fasciolosis) which can infect most mammals, but most commonly sheep and cattle, with consequent loss of

production in stock animals in  chronic cases and mortalities due to acute infections often in lambs as a result of ingesting a large numbers of (metacercarial) cysts.   

After eating its way through the gut and liver on entering the bile duct to become a mature egg laying, patent, adult fluke which achieves a length of ~ 20 to 30 mm and a

 width of ~ 10 - 14 mm. It is quite flat (it is a flatworm after all !)  Click on the life cycle bookmarks to  work through the stages and forms 1-7 below        

1. The Egg                                                       life cycle   

     Teaching advice: How to culture miracidia from fluke eggs.  


2. A Miracidium hatching from an egg     life cycle



 Liver fluke eggs some unembryonated, some with miracidia  (which have dense eye spots) one is unhatched, in another the operculum has blown open under pressure from the much expanded viscous cushion and finally to the right the miracidium emerges.

3. The Miracidium                                             life cycle                   

The miracidium which hatches from the egg on exposure to light is covered in cells

which have cilia that beat in unison. The cilia are orientated at a slight angle give the

miracidium a slight 'corkscrewing' forward movement.


 Publication details of the above scanning electron micrographs are given in block 4.

The miracidium is a free living stage which emerges from one of thousands of egs produced by adult flukes. These stages swim and locate young mud snails Lymnaea truncatula

by a process of increased turning when moving in an increasing concentration gradient of the chemicals released by a snail. This process which is not a taxis is referred to as a chemoklinokinesis.

Stages of contact and penetration :


Five miracidia, with their paired eyespots, are penetrating near to the eye of a snail. Initial attachment is followed by shedding of the ciliated cells near the snail and penetration into the snail tissue with the miracidia then transformed into sporocysts.

Intra-molluscan stages:

The redial stages, first grow within the sporocyst and then may generate a 2nd generation of rediae or cercariae within Lymnaea truncatula.

Image from Parasite Image collection Lincoln University

4. The cercaria                                          life cycle  

The cercarial body (contains all of the material which will secrete it's cyst).



Around the apical sucker are numerous sensory endings some with single cilia protruding.

There is an apical sucker connected to a pharynx and  paired penetration glands / caecae see:

See The cercaria  Diagram         

The cercaria swims my actively thrashing it's muscular tail.  

See  How the cercaria swims

Original Diagram



When it loses its tail, in the process which begins with attachment to a substrate (usually grass),

the lifecycle stage becomes known as a 'metacercaria'

But why should the tail have a twisted 'corkscrew-like' tip?

Could it play a part in escaping from the snail through its tegument ?

 Publications details of the above cercariae and miracidia (blocks 3 and 4) are from:   Bennett CE and Cambridge University Press

Journal of Helminthology 75 (1) pp 1-5

C.E. Bennett Fasciola hepatica: surfaces involved in movement of miracidia and cercariae

5. The Metacercaria                       life cycle

The quiescent stage: the metacercaria can survive for months at low temperatures and even freezing conditions.


Once ingested by a vertebrate host and at ~37C it begins to move as in the static picture below. The groups of bright spheres are excretory material built up during quiescence. These 'concretions' are ejected during activation and excystment.


bluespot.gif (912 bytes) GOTO Cyst structure  Original Diagram 

For Fasciola hepatica cysts contact Ridgeway Research


6. The Excysting juvenile fluke

Excystment occurs in the lumen of the gut of the host (sheep, cattle or other vertebrate host).

This image was taken in-vitro after simulating the conditions of passing through a vertebrate stomach and small intestine: (stomach acid, reducing conditions, 37C enzymes and bile)

The oral sucker and ventral sucker are clearly visible. Each sucker is surrounded by a group of sensory endings, with both exposed and enclosed single cilia, that detect contact with the host and the chemical environment.


The Newly Excysted Juvenile (NEJ) grows and develops in a migration through the

gut wall, peritoneal cavity on its way to the liver. (Some juveniles wander away from

the liver and may end up in inappropriate parts of the body where they cannot

mature and reach egg laying patency). Normally the maturing juvenile reaches the

bile ducts where the hermaphrodite* adults begin egg laying.


* hermaphrodite = has both female and male organs in the adult body allowing 

something like sexual reproduction to take place with the production of viable eggs.

The peripheral dark areas in the image below are vitelline glands that produce the

 raw materials, proteins that generate the tens of thousands of eggs (box 1) per day.


 7. The Newly Excysted Juvenile (NEJ)             life cycle

nej1.jpg (67604 bytes) 

  Dr. Clive Bennett 2013                                      Dr. Clive Bennett PhD thesis 1973

The newly excysted juvenile is around 0.1mm in length. This stage grows while it chews its way through the liver tissue. There is an oral sucker linked to the penetration glands bluespot.gif (912 bytes) GOTO Inside the oesophagus of the NEJ      Original Diagram

an independent mid positioned ventral sucker bluespot.gif (912 bytes) GOTO Inside the ventral sucker: (arrangement of musculature).    Original Diagram     and most posteriorly an excretory pore which links up to the typical flatworm excretory flame cells inside the body.

 The NEJ is also covered in rows of backwardly pointed spines  that keep it travelling forward as it rhythmically pulsates it's body. This  'vermiform' peristalsis squeezes the body contents into the apex whilst anchoring and re-anchoring with first the 'oral' sucker and then the mid-placed ventral sucker  (an entirely independent muscular organ).  

The Anterior surface of the newly excysted juvenile

(c.f. The same spines on maturation to an adult) > > > > > >


                                 Both images are Dr. Clive Bennett PhD thesis 1973

A single cilia (sensory ending) is seen between the spines which protrude from the surface tegument..

The 3D diagram shows the  cells below the tegument with spines in the tegument and the links between the anucleate surface and the 'cellular' regions with nuclei which lie below the longitudinal and circular musculature/ A flame cell and it's connecting excretory tubule is shown below these.

The syncytial surface of the juvenile shown here is maintained throughout development as seen in the surface of the adult to the right.

Secretory bodies, continually released onto the surface, are considered to be in part a response to the immune attack of the host.




8. The adult fluke                                        life cycle  


The dark areas around the sides of the adult  fluke below are the vitelline glands that supply the material for egg production. The dense redish area to the right is the uterus filled with eggs. To the right finally are the ventral and oral suckers

The Anterior surface of the adult liver fluke

Adult flukes have distally directed surface pines with multi-pointed spatulate appearance which are able to irritate the much thickened bile duct epithelium

Seen below is the fluke surface and its spines (photo taken in-situ).


The bile duct thickening, called hyperplasia, must provide nutrients by abrasion

from the spines. Other evidence suggests that chemicals such as proline, released from the fluke, directly promote the hyperplasia.


Dr. Clive Bennett 1974 Scanning Electron microscopy of adult anterior spines

Groups of sensory endings can be seen between the spines.

While the tegument continues to be involved in avoidance of the host immune defences it is also known, from physiological experiments, that this surface actively takes up nutrients of all kinds from amino acids to minerals by active transport and facilitated diffusion.


   Dr. Clive Bennett 1999 and 2013  and including copyright material from 1975 to 2013                                                                           


 The life CycleCEB posterscan.tif (1300344 bytes)


Chemotherapy specifically against Fasciola        

Alverin Plus   = Ivermectin and Clorsulon benzene sulfonamide

Baymec Gold = Ivermectin and Clorsulon benzene sulfonamide

Combinex  =     Triclabendazole with Levamisole

Fasimec   =       Ivermectin and Triclabendazole

Fasinex   =        Triclabendazole

Flukiver   =        Closantel

Ivomec Super = Ivermectin and Clorsulon  benzene sulfonamide

Nizan Gold   =   Levamisole and Oxyclosanide

Trodax          =   Nitroxynil

Valbazen       =   Albendazole

    Originating Drug Companies 

     Pfizer Animal Health (now Zoetis) 

     Valbazen  (Albendazole);   Distodin (Oxyclosanide) Alverin Plus (Ivermectin/clorsulon : benzene sulfonamide)   Startect  combination of Abermectin and Derquantel

Merial  Ivomec, (Ivermectin and Clorsulon : (benzene sulfonamide  )  Curatrem  Clorsulon;  Trodax = Nitroxynil,

Novartis Fasinex  (Triclabendazole),  and Combinex   (Levamisole hydrochloride with Triclabendazole) Fasimec (Ivermectin and Triclabendazole)

Bayer Animal Health  Baymec Gold  Combination of Ivermectin and Clorsulon (benzene sulfonamide)

Link to the next best Fasciola site:                Centre for Disease control USA
Diagnostic test from IDEXX


Control Measures

agent morphology history epidemiology transmission reservoir  symptoms diagnosis treatment public health

Links to other Fasciola sites:


Ectoparasites &Endoparasites Search the Web for Parasitology Submit or review link Author's Teaching Author's Research Home Page

Dr. Clive Bennett 1998 - 2013  Updated 29/11/2013