1. Echinococcus granulosus (and multilocularis) Sarah Richards Max Karpyak

2. Three Species  Echinococcus granulosus: causing hydatid disease  Echinococcus multilocularis: causing alveolar hydatid disease  Echinococcus vogeli: causing hydatid disease

3. Echinococcus multilocularis vs Echinococcus granulosus  Both produce hydatid disease in many mammals, including rodents and humans  Unlike E. granulosus, E. multilocularis produces many small cysts that spread throughout the infected animal

4. Geographic Distribution  Worldwide  Higher prevalence in South America (Argentina, Uruguay), Europe (Mediterranean bassin), Northern Africa, Middle East, South Central and East Asia

5. Larvae Stage  E. granulosus  Hydatid cysts are large, roughly spherical, fluid filled hollow bladders containing numerous protoscolices.  They vary in size; those found in the liver are aprox. 20 cm in diameter, but those found in the peritoneal cavity are usually larger  E. multilocularis  The cyst grows invasively by external budding, forming a diffuse growth through the infected organ, replacing that organs tissues. In contrast to E. Granulosus this growth is very rapid, infective prosocialises being present only 2 to 3 months.

6. Adult Stage  E. multilocaris  Slightly smaller than E. granulosus (max. length of aprox 4 mm and consisting of 4-5 proglottids).  E. granulosus  The adult parasites in the dog represent one of the smallest of the tapeworms (3-9 mm in length, usually with 3 proglottids).  Scolex is globular in shape and has a prominent rostellum

7. Definitive Hosts E. granulosus  Dogs  Coyotes  Wolves E. multilocularis  Mostly foxes

8. Intermediate Hosts E. granulosus  Sheep  Horses  Camels  Pigs  Humans E. multilocularis  Small rodents

9. Life Cycle: E. granulosus  The adult is in the small bowel of the definitive host  Gravid proglottids release eggs that are passed in the feces  In the intermediate host the egg hatches in the small bowel and releases an oncosphere  The oncosphere penetrates the intestinal wall and moves through the circulatory system to various organs  In the organs they develop into cysts and enlarge gradually  The cysts produce protoscolices and daughter cysts  Definitive host eats the infected organs and becomes infected  After ingestion, the protoscolices evaginate, attach to the intestinal mucosa and develop into adult stages  In 32-80 days, the cycle starts over

10. Life Cycle: E. multilocularis  The life cycle is basically the same E. granulosus Except  There are different definitive and intermediate hosts  Larval growth in the liver remain indefinitely in the proliferative stage, which causes invasion of the surrounding tissues (sometimes this can take over the whole organ)

11. Life Cycle (cont’d)

12. Diagnosis  Diagnosis in the definitive host is difficult by ordinary microscopy because it will look a lot like Taenia and Echinococcus eggs  Detection of antigens in feces by ELISA is currently the best available technique  Newer techniques like polymerase chain reaction (PCR) is also used to identify the parasite from DNA isolated from eggs or feces

13. Treatment  Surgery: with the goal of leaving the cyst intact so new cysts do not form  Mebendazole can be taken over a long period of time at low dosages  Praziquantel

14. Prevention  The best way to keep dogs from being infected is to prevent them from eating infected feces, or contaminated meat  The best way to avoid human infection is to avoid ingesting food or other substances contaminated with dog feces

15. Prevention (cont’d)  The best method is to disrupt the lifecycle  Basic hygiene practices  Avoid feeding raw offal (internal organs of butchered animals) to dogs  By doing this hydatids have been virtually eliminated in New Zealand (a once common place for this parasite)

16. QUESTIONS

17.  1. What are the main differences between the larvae stage of E. granulosus and E. multilocularis?

18.  E. granulosus  Hydatid cysts are large, roughly spherical, fluid filled hollow bladders containing numerous protoscolices.  They vary in size; those found in the liver are aprox. 20 cm in diameter, but those found in the peritoneal cavity are usually larger  E. multilocularis  The cyst grows invasively by external budding, forming a diffuse growth through the infected organ, replacing that organs tissues. In contrast to E. Granulosus this growth is very rapid, infective prosocialises being present only 2 to 3 months.

19. 2. What are the definitive hosts for each parasite?

20. E. granulosus  Dogs  Coyotes  Wolves E. multilocularis  Mostly foxes