Transmission of Flukes and Tapeworms

Question 1

Flukes

Answer 1

1) attach and encyst on vegetation as metacercaria: FH infected by ingesting vegetation
2) penetrate 2nd IH and encyst as metacercaria; FH infected by ingesting 2nd IH
3) penetrate FH through skin or gut wall, omitting metacercarial stage

All veterinary fluke parasites use snails as 1st IH

Question 2

Fasciola hepatica

Answer 2

IH: snails of genus Lymnaea - requires water, but can spend most of the time out of it

FH ingests – excysts in small intestine of host – migrates through gut wall into peritoneal cavity – liver – wanders in liver tissue for 6 wks. – bile ducts – grows to adult

Question 3

Fasciola gigantica

Answer 3

Lymnaeid snails

Question 4

Fascioloides magna

Answer 4

Lymnaeid snails

Question 5

Paragonimus kellicoti-

Answer 5

IH I: water snails
IH II: crawfish
FH infected by eating crawfish containing metacerariae or by eating animals that have recently fed on crawfish. Prepatent period 1 month

Question 6

Paragoniums westermani

Answer 6

infected by ingesting improperly cooked crawfish or fresh-water crabs. (crustateans)

Question 7

Nanophyetus salmincola

Answer 7

IH 1: snails

IH 2: Salmonid fish (also other fish and amphibians)

Question 8

Metorchis conjunctus/Metorchis felis

Answer 8

. IH I: water snails

IH II: fish

Question 9

Clonorchis sinensis

Answer 9

IH I: water snails

IH II: fish

Question 10

Platynosomum fastosum

Answer 10

IH 1: Land snail
IH 2: crustacean
IH 3: lizards, frogs

Question 11

Dicrocoelium dendriticum

Answer 11

IH1: Land snail
IH2: Common brown ant in N. America. - Alter ant’s behavior-hang near tops of vegetation-
eaten by FH

Question 12

Alaria canis/Alaria americana

Answer 12

. IH 1: water snails
IH 2: amphibian, such as frog
Paratenic hosts possible-rodents, etc

Question 13

Schistosomatidae

Answer 13

IH- Water snail - cercariae penetrate skin of FH.

Question 14

Dipylidium caninum

Answer 14

flea tapeworm

Question 15

Taenia sp

Answer 15

eating infected meat

Question 16

Echinococcus granulosus

Answer 16

usually herbivores; also pig, man, and other mammals

Question 17

Echinococcus multilocularis

Answer 17

Usually rodents and insectivores; occasionally man

Question 18

Mesocestoides sp

Answer 18

IH I – coprophageous beetles; orabatid mites
IH II – vertebrates such as the rabbit – develop in pleural and peritoneal cavities
Small intestine in final host – no pathology

Question 19

Pseudophyllidean tapeworms

Answer 19

Egg hatches – free swimming ciliated coracidium (hexacanth embryo with ciliated coat) – must hatch in water environment and be ingested by copepod crustacean IH I within 24 hours or dies  develops into a solid elongate larva (procercoid)  copepod eaten by vertebrate IH II  procercoid migrates to muscles and other organs  develops into last larval stage (plerocercoid) – an elongated solid body with partly invaginated scolex from which adult tapeworm develops when 2nd IH ingested by FH. Sometimes IH III also.

Question 20

Diphyllobothrium latum

Answer 20

IH I – copepod crustaceans

IH II – most fresh-water fish

Question 21

Spirometra mansonoides

Answer 21

IH I: Water crustacean

IH II: Water snake, frog, rodent, etc.