Echinococcus Echinococcus granulosusgranulosus (and (and multilocularis)multilocularis)

Sarah RichardsSarah Richards

Max KarpyakMax Karpyak

Three SpeciesThree Species

Echinococcus granulosusEchinococcus granulosus: causing : causing hydatid diseasehydatid disease

Echinococcus multilocularisEchinococcus multilocularis: causing : causing alveolar hydatid diseasealveolar hydatid disease

Echinococcus vogeliEchinococcus vogeli: causing hydatid : causing hydatid diseasedisease

Echinococcus multilocularisEchinococcus multilocularis vs vs Echinococcus granulosusEchinococcus granulosus

Both produce hydatid Both produce hydatid disease in many disease in many mammals, including mammals, including rodents and humansrodents and humans

Unlike Unlike E. granulosusE. granulosus, , E. multilocularisE. multilocularis produces many small produces many small cysts that spread cysts that spread throughout the throughout the infected animalinfected animal

Geographic DistributionGeographic Distribution

WorldwideWorldwide Higher prevalence in South America Higher prevalence in South America

(Argentina, Uruguay), Europe (Argentina, Uruguay), Europe (Mediterranean bassin), Northern Africa, (Mediterranean bassin), Northern Africa, Middle East, South Central and East AsiaMiddle East, South Central and East Asia

Larvae Stage Larvae Stage

E. granulosusE. granulosus Hydatid cysts are large, Hydatid cysts are large,

roughly spherical, fluid roughly spherical, fluid filled hollow bladders filled hollow bladders containing numerous containing numerous protoscolices.protoscolices.

They vary in size; those They vary in size; those found in the liver are found in the liver are aprox. 20 cm in diameter, aprox. 20 cm in diameter, but those found in the but those found in the peritoneal cavity are peritoneal cavity are usually largerusually larger

E. multilocularisE. multilocularis The cyst grows invasively The cyst grows invasively

by external budding, by external budding, forming a diffuse growth forming a diffuse growth through the infected through the infected organ, replacing that organ, replacing that organs tissues. In organs tissues. In contrast to E. Granulosus contrast to E. Granulosus this growth is very rapid, this growth is very rapid, infective prosocialises infective prosocialises being present only 2 to 3 being present only 2 to 3 months. months.

Adult StageAdult Stage

E. multilocarisE. multilocaris Slightly smaller than Slightly smaller than

E. granulosusE. granulosus (max. (max. length of aprox 4 mm length of aprox 4 mm and consisting of 4-5 and consisting of 4-5 proglottids). proglottids).

E. granulosusE. granulosus The adult parasites in The adult parasites in

the dog represent one the dog represent one of the smallest of the of the smallest of the tapeworms (3-9 mm tapeworms (3-9 mm in length, usually with in length, usually with 3 proglottids). 3 proglottids).

Scolex is globular in Scolex is globular in shape and has a shape and has a prominent rostellumprominent rostellum

Definitive HostsDefinitive Hosts

E. granulosusE. granulosus DogsDogs CoyotesCoyotes WolvesWolves

E. multilocularisE. multilocularis Mostly foxesMostly foxes

Intermediate HostsIntermediate Hosts

E. granulosusE. granulosus SheepSheep HorsesHorses CamelsCamels PigsPigs HumansHumans

E. multilocularisE. multilocularis Small rodentsSmall rodents

Life Cycle: Life Cycle: E. granulosusE. granulosus The adult is in the small bowel of the definitive hostThe adult is in the small bowel of the definitive host Gravid proglottids release eggs that are passed in the fecesGravid proglottids release eggs that are passed in the feces In the intermediate host the egg hatches in the small bowel In the intermediate host the egg hatches in the small bowel

and releases an oncosphere and releases an oncosphere The oncosphere penetrates the intestinal wall and moves The oncosphere penetrates the intestinal wall and moves

through the circulatory system to various organsthrough the circulatory system to various organs In the organs they develop into cysts and enlarge graduallyIn the organs they develop into cysts and enlarge gradually The cysts produce protoscolices and daughter cystsThe cysts produce protoscolices and daughter cysts Definitive host eats the infected organs and becomes Definitive host eats the infected organs and becomes

infectedinfected After ingestion, the protoscolices evaginate, attach to the After ingestion, the protoscolices evaginate, attach to the

intestinal mucosa and develop into adult stagesintestinal mucosa and develop into adult stages In 32-80 days, the cycle starts overIn 32-80 days, the cycle starts over

Life Cycle: Life Cycle: E. multilocularisE. multilocularis

The life cycle is basically the The life cycle is basically the same E. same E. granulosusgranulosus

ExceptExcept There are different definitive There are different definitive

and intermediate hostsand intermediate hosts Larval growth in the liver Larval growth in the liver

remain indefinitely in the remain indefinitely in the proliferative stage, which proliferative stage, which causes invasion of the causes invasion of the surrounding tissues surrounding tissues (sometimes this can take over (sometimes this can take over the whole organ)the whole organ)

Life Cycle (cont’d)Life Cycle (cont’d)

DiagnosisDiagnosis

Diagnosis in the definitive host is difficult by Diagnosis in the definitive host is difficult by ordinary microscopy because it will look a lot ordinary microscopy because it will look a lot like like TaeniaTaenia and and Echinococcus Echinococcus eggseggs

Detection of antigens in feces by ELISA is Detection of antigens in feces by ELISA is currently the best available techniquecurrently the best available technique

Newer techniques like polymerase chain Newer techniques like polymerase chain reaction (PCR) is also used to identify the reaction (PCR) is also used to identify the parasite from DNA isolated from eggs or fecesparasite from DNA isolated from eggs or feces

TreatmentTreatment

Surgery: with the goal of leaving the cyst Surgery: with the goal of leaving the cyst intact so new cysts do not formintact so new cysts do not form

Mebendazole can be taken over a long Mebendazole can be taken over a long period of time at low dosagesperiod of time at low dosages

PraziquantelPraziquantel

PreventionPrevention The best way to keep The best way to keep

dogs from being infected dogs from being infected is to prevent them from is to prevent them from eating infected feces, or eating infected feces, or contaminated meatcontaminated meat

The best way to avoid The best way to avoid human infection is to human infection is to avoid ingesting food or avoid ingesting food or other substances other substances contaminated with dog contaminated with dog fecesfeces

Prevention (cont’d)Prevention (cont’d)

The best method is to disrupt the lifecycleThe best method is to disrupt the lifecycle Basic hygiene practices Basic hygiene practices Avoid feeding raw offal (internal organs of Avoid feeding raw offal (internal organs of

butchered animals) to dogsbutchered animals) to dogs By doing this hydatids have been virtually By doing this hydatids have been virtually

eliminated in New Zealand (a once common eliminated in New Zealand (a once common place for this parasite)place for this parasite)

QUESTIONSQUESTIONS

1. What are the main differences 1. What are the main differences between the larvae stage of between the larvae stage of E. E. granulosus granulosus andand E. multilocularis? E. multilocularis?

E. granulosusE. granulosus Hydatid cysts are large, Hydatid cysts are large,

roughly spherical, fluid roughly spherical, fluid filled hollow bladders filled hollow bladders containing numerous containing numerous protoscolices.protoscolices.

They vary in size; those They vary in size; those found in the liver are found in the liver are aprox. 20 cm in diameter, aprox. 20 cm in diameter, but those found in the but those found in the peritoneal cavity are peritoneal cavity are usually largerusually larger

E. multilocularisE. multilocularis The cyst grows invasively The cyst grows invasively

by external budding, by external budding, forming a diffuse growth forming a diffuse growth through the infected through the infected organ, replacing that organ, replacing that organs tissues. In organs tissues. In contrast to E. Granulosus contrast to E. Granulosus this growth is very rapid, this growth is very rapid, infective prosocialises infective prosocialises being present only 2 to 3 being present only 2 to 3 months. months.

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

E. granulosusE. granulosus DogsDogs CoyotesCoyotes WolvesWolves

E. multilocularisE. multilocularis Mostly foxesMostly foxes