Echinococcus granulosus (and multilocularis)

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					Echinococcus
granulosus (and
multilocularis)

Sarah Richards
Max Karpyak
Three Species

  Echinococcus granulosus: causing
   hydatid disease
  Echinococcus multilocularis: causing
   alveolar hydatid disease
  Echinococcus vogeli: causing hydatid
   disease
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
Geographic Distribution

  Worldwide
  Higher prevalence in South America
   (Argentina, Uruguay), Europe
   (Mediterranean bassin), Northern Africa,
   Middle East, South Central and East Asia
Larvae Stage

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

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

 E. granulosus   E. multilocularis
  Dogs           Mostly foxes
  Coyotes
  Wolves
Intermediate Hosts

 E. granulosus   E. multilocularis
  Sheep          Small rodents
  Horses
  Camels
  Pigs
  Humans
 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
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)
Life Cycle (cont’d)
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
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
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
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)
QUESTIONS
 1. What are the main differences
  between the larvae stage of E.
  granulosus and E. multilocularis?
 E. granulosus                  E. multilocularis
   Hydatid cysts are large,        The cyst grows invasively
    roughly spherical, fluid         by external budding,
    filled hollow bladders           forming a diffuse growth
    containing numerous              through the infected
    protoscolices.                   organ, replacing that
   They vary in size; those         organs tissues. In
    found in the liver are           contrast to E. Granulosus
    aprox. 20 cm in diameter,        this growth is very rapid,
    but those found in the           infective prosocialises
    peritoneal cavity are            being present only 2 to 3
    usually larger                   months.
2. What are the definitive hosts for each
  parasite?
E. granulosus   E. multilocularis
 Dogs           Mostly foxes
 Coyotes
 Wolves

				
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