VET 350 Sections 5.3.4-5.4.2 PowerPoint-1

Echinococcus and Tapeworms Overview

  • Examines Echinococcus and other Cyclophyllidean and Pseudophyllidean tapeworms

Echinococcus Species

  • Major Species:

    • Echinococcus granulosus

    • Echinococcus multilocularis

  • Adult Length: about 0.5 cm

Metacestodes

  • Hydatid Cyst (E. granulosus)

    • Fluid-filled bladder with brood capsules containing inverted tapeworm heads.

  • Alveolar Cyst (E. multilocularis)

    • Forms daughter cysts that bud off externally, leading to mass formation in host tissue.

Cystic Echinococcosis (CDC) Process

  1. Adult in Small Intestine

    • Released from hydatid cysts in definitive host.

  2. Definitive Host Ingestion

    • Ingestion of cysts/eggs (via organs or feces).

  3. Intermediate Host

    • Embryonated eggs in feces.

  4. Hydatid Cysts

    • Develop in various organs (commonly liver and lungs).

  5. Diagnostic Stage

    • Hydatid cyst presence spotted through examination.

Hydatid Disease

  • Cystic Echinococcosis

    • Occurs when hydatid cyst develops in the body.

  • Range of cyst sizes: tennis ball to football.

  • Dogs serve as final hosts, with cysts acting as space-occupying lesions.

Epidemiology of Echinococcus

  • Host variability based on geographic location:

    • Dog-Sheep Strain

      • Dogs eat sheep, releasing segments/eggs in environment.

    • Dog-Horse Strain

      • Cysts only develop in horses.

Alveolar Hydatid Disease

  • Echinococcus multilocularis mainly in northern hemisphere.

  • Common hosts: dogs, cats (adult tapeworm carriers).

  • Main cycle: fox as final host, shrews/voles as intermediate hosts.

  • Infectious to various mammals, including humans; can be lethal.

Anoplocephala

  • Anoplocephala perfoliata

    • No scolex hooks; contains swellings (lappets).

    • Length: about 5 cm, found in cecum near ileo-cecal junction.

    • Potential issues: colic, ileal impaction, intussusception.

    • Egg identification: pyriform apparatus with chitinous ring.

    • Intermediate hosts: oribatid or pasture mites.

Moniezia

  • Generally not clinically significant.

  • Proglottids found in feces; segments wider than long.

  • Oribatid mites act as intermediate hosts.

Dipylidium

  • Dipylidium caninum

    • Size: about 0.5 meters, with multiple rows of hooks on scolex.

    • Proglottids are oval, having two lateral genital pores.

    • Symptoms: anal irritation, potential diarrhea.

    • Intermediate host: fleas; flea larvae consume Dipylidium eggs.

Poultry Cestodes

  • Davainea proglottina

    • Small size (4-9 segments), found in poultry and pigeons' duodenum.

    • Can cause hemorrhagic enteritis; intermediate hosts include slugs and snails.

Diphyllobothriid Tapeworms (CDC)

  1. Infected crustacean ingestion leads to plerocercoid larva invasion.

  2. Small fish ingests infected crustaceans; plerocercoids invade fish tissue.

  3. Numerous fish-eating mammals/birds serve as definitive hosts.

  4. Infection cycle involves embryonated eggs passed in feces/water.

Important Pseudophyllideans

  • Diphyllobothrium latum

    • Zoonotic; main definitive hosts are humans, while fish serve as second intermediate hosts.

    • Found predominantly in colder, northern regions.

  • Spirometra mansonoides

    • Zoonotic; potential human infection via intermediate host leading to sparganosis.

    • Primarily found in cats in North America; utilizes copepods and various vertebrates as intermediate hosts.