Echinococcus granulosus (and multilocularis)

SUBMITTED BYSAKIRGR 21 SEM 7TH

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 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.

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

Definitive Hosts

E. granulosus Dogs Coyotes Wolves

E. multilocularis Mostly foxes

Intermediate Hosts

E. granulosus Sheep Horses Camels Pigs Humans

E. multilocularis Small rodents

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)

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

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.

2. What are the definitive hosts for each parasite?

E. granulosus Dogs Coyotes Wolves

E. multilocularis Mostly foxes

Echinoccocus

 is caused by infection with the larval stage of Echinococcus granulosus. CE is found in Africa, Europe, Asia, the Middle East, Central and South America, and in rare cases, North America. The parasite is transmitted to dogs when they ingest the organs of other animals that contain hydatid cysts. The cysts develop into adult tapeworms in the dog. Infected dogs shed tapeworm eggs in their feces which contaminate the ground. Sheep, cattle, goats, and pigs ingest tapeworm eggs in the contaminated ground; once ingested, the eggs hatch and develop into cysts in the internal organs. The most common mode of transmission to humans is by the accidental consumption of soil, water, or food that has been contaminated by the fecal matter of an infected dog. Echinococcus eggs that have been deposited in soil can stay viable for up to a year. The disease is most commonly found in people involved in raising sheep, as a result of the sheep's role as an intermediate host of the parasite and the presence of working dogs that are allowed to eat the offal of infected sheep.

Alveoccocus

is caused by infection with the larval stage of Echinococcus multilocularis. AE is found across the globe and is especially prevalent in the northern latitudes of Europe, Asia, and North America. The adult tapeworm is normally found in foxes, coyotes, and dogs. Infection with the larval stages is transmitted to people through ingestion of food or water contaminated with tapeworm eggs.