Echinococcus Granulosus

''Echinococcus granulosus,'' also called the '''Hydatid worm''', is a Cyclophyllid Cestode that parasitizes the Small Intestine of Canids as an adult, but which has important Intermediate Host s such as Livestock and humans, where it causes Hydatid Disease . The adult Tapeworm is about 5 Mm long and has three Proglottid s ("segments") when intact. Like all cyclophyllideans, ''E. granulosus'' has four suckers on its Scolex ("head"), and ''E. granulosus'' also has a rostellum with hooks.

In canids, ''E. granulosus'' causes a typical tapeworm infection, and produces eggs that are passed with the dog's Feces . Intermediate hosts include herbivores such as Sheep , Deer , Moose , Kangaroo s, and Wallabies , and any other organism (including humans) that ingests dog feces. In the intermediate host, eggs hatch into oncosphere larvae that travel through the Blood and form hydatid cysts in the host's Tissue s. These cysts can grow to be the size of a Softball or Basketball , and may contain several smaller "balloons" inside the main cyst. In the related worm '' Echinococcus Multilocularis '', the outer cyst is not present. If the outer cyst ruptures, new cysts can form at a different location in the body. Each smaller section contains several juvenile worms, and dogs may eat millions of them, resulting in very heavy infections. Hydatid cysts occur in organs like the Liver , Brain and Lung s, not in Subcutaneous tissue. Though this has never been tested experimentally, it is assumed that infected animals make easier Prey for canids.

Symptoms can include liver enlargement, hooklets in Sputum and possible Anaphylactic Shock when the immune system reacts to ruptured cysts. A cyst diagnosis with Ultrasound , MRI , or Immunoelectrophoresis .

Hydatid disease is treated with surgery, taking special care to leave the cyst intact so new cysts do not form, and Mebendazole over a long period of time at low dosages.

The best way to keep dogs from being infected is to prevent them from eating infected meat. The best way to avoid human infection is to avoid ingesting dog feces.

SCREENING FOR ACTIVITY AGAINST ECHINOCOCCUS GRANULOSUS

(1) BALB/c mice infected with secondary equine E. granulosus

Parasitology. 1988 Apr;96 ( Pt 2):323-36
Echinococcus granulosus: the effects of praziquantel, in vivo and in vitro, on the ultrastructure of equine strain murine cysts.
Richards KS, Morris DL, Daniels D, Riley EM.

Praziquantel (500 mg/kg) administered orally to BALB/c mice infected with secondary equine E. granulosus daily for 21, 30 or 30 + 30 days without the drug
Ultrastructural examination of cysts showed increased vesiculation of the germinal layer leading, in many, to the loss of its integrity.
Increased mitochondrial numbers occurred frequently.
Longer drug treatments appeared to have greater effects on germinal layer
There was no detectable reestablishment of structural organization within 30 days after drug withdrawal.
Tissue from collapsed cysts was necrotic.
In an in vitro study at praziquantel concentrations of 1000 and 5000 micrograms/l over a 10-day period, most cysts showed ultrastructurally a time- and concentration-dependent loss of integrity identical to that seen in vivo

(2) Echinococcus granulosus in Gerbils
Morris DL, Taylor DH. ( J Helminthol. 1990)

Gerbils with well-developed peritoneal cysts of E. granulosus randomized to albendazole 50 mg/kg/day or untreated control.

Treated animals had less disease at post mortem after 3 months of treatment.

Cysts were then taken from both albendazole-treated and control animals and cultured in vitro either with or without albendazole sulphoxide (Alb Sx) 500 micrograms/L for 14 days.

Viability of cysts was then established by implantation of whole cysts into gerbils.

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Echinococcus Granulosus