Echinococcus multilocularis

Question 1

Structure

Answer 1

very short cestode (tapeworm) of small intestine, ~1-4mm
very little genetic variation

Question 2

Types

Answer 2

European, Alaskan, North American, Hokkaido (Japan)

Question 3

Definitive hosts

Answer 3

most canids and felids
-foxes, coyotes, domestic dogs, wild and domestic cats

Question 4

Intermediate hosts

Answer 4

rodents, monkeys, and pigs
dependent on variant

Question 5

Unique consequence

Answer 5

forms hydatid cysts-cysts that often form in the liver

Question 6

Is it zoonotic?

Answer 6

yes

Question 7

Hosts preferred by North American Variant

Answer 7

definitive: red foxes, coyotes, domestic dogs, cats
Intermediate: wild rodents and house mice

Question 8

Hosts preferred by Alaskan Variant

Answer 8

Definitive: foxes
Intermediate: wild rodents

Question 9

Host preferred by European Variant

Answer 9

Definitive: red foxes, wolves, raccoon-dogs, domestic dogs, cats
Intermediate: rodents, wild pigs, monkeys, domestic pigs, and dogs

Question 10

Host preferred by Hokkaido

Answer 10

Definitive: foxes, raccoon-dogs, domestic dogs, cat
Intermediate: wild rodents, pigs, monkeys, house mice

Question 11

Life cycle of Hydatid Cysts

Answer 11

very thin outer wall-> grows and infiltrates processes into surrounding host tissues
-high ability to bud and metastasize to other areas-> Metacestode form: fluid-filled, spherical, unilocular cyst that consists of an inner germinal layer of cells supported by a characteristic acellular, laminated membrane of variable thickness-> Alveolar or multilocular hydatid

Question 12

Transmission cycle

Answer 12

Shed eggs from strobila in definitive host’s feces-> highly resistant to environmental stressors

Question 13

Pathogenesis

Answer 13

Swallowed by intermediate hosts-> oncospheres hatch in stomach or small intestine-> penetrate mucosa-> enter circulation-> carried to liver-> new definitive host ingests alveolar larvae
Longer infections-> can see in spleen, mesentery, and peritoneum as well-> takes 6-8 weeks to reach maturity

Question 14

Influencing factors to transmission

Answer 14

habitat and soil type are important-> forest, level of humidity

Question 15

Clinical Signs

Answer 15

definitive hosts generally asymptomatic
Intermediate hosts can get sick: sudden death, distended abdomen, difficulty moving, jaundice, weight loss

Question 16

Pathologic Lesions

Answer 16

-Spongy, locally invasive masses in liver, lung, and spleen filled with clear or turbid fluid and occasional calcification around cyst
Microscopic: in liver parenchyma->inflammatory/granulomatous reaction or extensive peripheral necrosis and fibrosis

Question 17

Diagnostics

Answer 17

identification of adult worms in feces
On necropsy: Sedimentation and counting, Intestinal scraping
Coproantigen ELISA test, PCR

Question 18

Management

Answer 18

Anti-parasitic oral bait in high endemic areas
-clear carcasses of intermediate species when found-avoid allowing domestic species from consuming these
-discourage wild animals from entering human population locations
-make public aware and encourage hand washing after handling dogs or other canids