Cestodes 2

Question 1

What are the definitive hosts and intermediate host of Dipylidium caninum?

Answer 1

Dogs and cats: definitive

Fleas: Intermediate

Question 2

What is the metacestode of D. caninum?

Answer 2

Cysticercoid

Question 3

What are the morphological characteristics of D. caninum?

Answer 3

Adults up to 50 cm long, gravid segments (motile) appear in feces with genital pores on both sides, tapeworm baskets

Question 4

Describe the life cycle of D. caninum.

Answer 4

Gravid segments breakdown, releasing egg packets containing taeniid eggs; ingested by flea larvae; can also be transmitted by lice; 4-6 weeks required for development of infected metacestode (cysticercoid) in flea; definitive host infected through ingestion of fleas; adult in SI - maturity in 4-6 weeks

Question 5

What is the clinical significance of D. caninum?

Answer 5

Largely apathogenic - owner panic!

Occasional zoonosis

Question 6

What are the effective treatments for D. caninum?

Answer 6

Prazi and nicolasamide

Question 7

What are the characteristics of Echinococcus spp of tapeworms?

Answer 7

Carnivore definitive host, zoonotic implications, very small tapeworms of only 3-5 segments: ‘dwarf tapeworm’

Question 8

What are the metacestodes of Echinococcus spp?

Answer 8

Hydatid cysts

Question 9

Describe the life cycle of E. granulosus.

Answer 9

Embryonated egg in feces of definitive host; eggs either ingested by humans or ruminant intermediate host; hydatid cysts consumed by definitive host through consumption of intermediate host organs; protoscolex hatches from cyst in definitive host and attaches to wall of SI

Question 10

What are the E. granulosus subspecies to know?

Answer 10

E. granulosus granulosus, E. granulosus equinus, E. granulosus multilocularis, E. candensis

Question 11

What are the public health implications of Echinococcus?

Answer 11

Only some strains are zoonotic; cystic echinococcosis (single, but large cysts); alveolar echinococcosis (metastatic behavior)

Question 12

What are the control methods for Echinococcosis/Hydatidosis?

Answer 12

Dog helminth control, disposal of ruminant carcasses, care when foraging in areas where there are wild carnivores, checking pet passport for microchip, rabies vx, and anthelmintic treatment against Echinococcus within 3 days of entry

Question 13

Describe E. granulosus as a zoonotic agent.

Answer 13

Hydatid disease; about 10 known cases annually in GB

Control through education, regular dog deworming, and disposal of sheep feces

Question 14

Where are most clinical cases of E. multilocularis in North America?

Answer 14

Alaska and Canada

Question 15

Describe the life cycle of E. multilocularis.

Answer 15

Egg in feces of definitive host with oncosphere inside; ingested either by rodent intermediate host or humans as an accidental host; metacestodes in liver of intermediate host; ingested by fox, dog, or raccoon definitive host; adult in SI

Question 16

Describe the burden of alveolar echinococcosis.

Answer 16

Globally, loss of at least 600,000 DALYs annually; patients often present with advanced disease; metastasis and prolonged survival of cysts; risk of allergic response during surgery; prolonged therapy (albendazole), often surgery, sometimes liver transplantation

Question 17

What are the characteristics of Anoplocephala spp?

Answer 17

Tapeworms of horses, cluster around the ileo-cecal junction, eggs are distinctive due to the pyriform apparatus

Question 18

What are the Anoplocephala spp to know?

Answer 18

Anoplocephala perfoliata, Anoplocephala magna, Paranoplocephala mammilana

Question 19

Describe the life cycle of Anoplocephala tapeworms.

Answer 19

Proglottids containing eggs in feces of horse; eggs to cysticercoids in oribatid mites; mites consumed during grazing of horses; adults in ileo-cecal junction of definitive host

Question 20

Anoplocephala tapeworms have a ______ distribution.

Answer 20

Widespread

Question 21

How are Anoplocephala tapeworms diagnosed?

Answer 21

Egg-shedding intermittent - eggs do not float especially well; antibody ELISA available

Question 22

What are the clinical implications of clustering of Anoplocephala tapeworms around the ileo-cecal junction?

Answer 22

Potential for impaction, colic, and intussusception

Question 23

What is the treatment protocol for Anoplocephala tapeworms?

Answer 23

Twice yearly with pyrantel, (double dose) praziquantel, or if ELISA positive

Question 24

What are the characteristics of Moniezia expansa and M. benedini?

Answer 24

Small intestine of ruminants; like Anoplocephala: cysticercoids in oribatid mites and eggs similar in appearance; usually non-pathogenic - no specific treatment recommended

Question 25

What is the common name for Diphyllobothrium latum?

Answer 25

"Broad Fish Tapeworm"

Question 26

Where is the broad fish tapeworm along with other Diphyllobothrium spp found?

Answer 26

Scandinavia, Russia, Baltics, Pacific Northwest, Japan

Question 27

What is the clinical importance of the broad fish tapeworm?

Answer 27

Important zoonotic infection from fish; causes B12 deficiency - pernicious anemia; occasional cause of GIT disease in dogs, cats, Pacific Northwest, Canada, Alaska

Question 28

Describe the life cycle of Diphyllobothrium tapeworms.

Answer 28

Unembryonated operculate eggs passed in feces of definitive host and embryonate in water; coracidia hatch from eggs and are ingested by crustaceans; infected crustacean ingested by small fish; possible paratenic host of larger predator fish; fish-eating mammals, birds, and humans act as definitive hosts by ingesting plerocercoids in fish and attach to SI via grooves (bothria); PPP: 4-8 weeks

Question 29

What are the important poultry tapeworms?

Answer 29

Davainea, Rallietina, and Chaonotaenia

Question 30

What are the intermediate hosts of muscid tapeworms?

Answer 30

Invertebrate mollusks and muscid flies

Question 31

What is the clinical significance of poultry tapeworms?

Answer 31

Generally minor pathogenic importance; potentially require treatment - young birds, backyard flocks