Exam I - Taenia spp.

Question 1

Which species of Taenia are we likely to observe in cats?

Answer 1

Taenia taeniaeformis

Question 2

Name the intermediate host(s) forTaenia taeniaeformis

Answer 2

Mice & rats (and rarely humans)

Question 3

What is the PPP for Taenia taeniaeformis?

Answer 3

6 weeks

Question 4

Which life stage of *Taenia taeniaeformis *is ingested by the intermediate host?

Answer 4

oncosphere

Question 5

What is the organ of predilection in the intermediate host for Taenia taeniaeformis?

Answer 5

the liver

Question 6

In what organ of the final host will you find the adult Taenia taeniaeformis?

Answer 6

small intestine

Question 7

Describe some common clinical signs you might see with* Taenia taeniaeformis *

Answer 7

Infection in the final host is usually asymptomatic.

Question 8

Describe the life cycle of *Taenia taeniaeformis *

Answer 8

1. Segments are shed from the carnivore final host
2. Segments release eggs, which develop into oncospheres
3. Oncosphere is ingested by intermediate host (mouse & rat) & migrates to the liver (the organ of predilection)
4. Develops to the second-stage larva (strobilocercus), which is infective to final host
5. FInal host ingests the strobilocercus in the liver
6. strobilocercus is digested and develops in the small intestine to an adult tapeworm

Simplified

Segments are shed & release eggs –> oncospheres –> ingested & migrate to liver of IH –> develop to strobilocercus –> IH is ingested by FH –> strobilocercus digested & develops to adult

Question 9

*Taenia taeniaeformis *reach up to ___ cm in final host

Answer 9

Taenia taeniaeformis reach up to 60 cm in final host

Question 10

*Taenia taeniaeformis *eggs are ____ µm in size

Answer 10

Taenia taeniaeformis eggs are 25-40 µm in size

Question 11

What is/are the final host(s) for Taenia crassiceps?

Answer 11

Foxes and dogs

Question 12

What is/are the intermediate host(s) for Taenia crassiceps?

Answer 12

small rodents

Question 13

Describe the appearance of the Taenia crassiceps adult

Answer 13

Adult cestodes with scolex and 4 suckers up to 2 m long. Segments rectangular with unilateral genital pores alternating irregularly from one side to the other

Question 14

Describe the appearance of the Taenia crassiceps egg

Answer 14

Eggs are taeniid type with brown color, radial striations in the shell, and presence of 6 embryonic hooks. Morphologically indistinguishable from Echinococcus spp.

Eggs are not easily seen on fecal flotation because they are usually in segments when they leave the host.

Question 15

Decribe the life cycle of Taenia crassiceps

Answer 15

Gravid taeniid segments are shed from the carnivore final host through the anus. Segments release eggs in the environment, which develop to oncospheres. The oncosphere is ingested by the intermediate host, enters the wall of the small intestine, and migrates to its organ of predilection (the abdominal cavity).

Here, it develops to a 2nd stage larva (cysticercus), which is infective to the final host. Usually 1 oncosphere develops into 1 larval tage, the cysticercus, but T. crassiceps has asexual multiplication which results in many cysticerci surrounded by a single host tissue capsule.

After the final host ingests the cysticercus, it is digested and develops in the small intestine to an adult tapeworm. PPP is 6-9 weeks.

_Simplified _

Segments shed in feces –> eggs released in environment –> oncospheres –> ingested by intermediate host & migrates to abdominal cavity –> multiple 2nd larval stages (cysticerci) –> final host digests cysticerci –> digested & develops in SI to adult. PPP is 6-9 weeks.

Question 16

In which organ would you expect to find Taenia crassiceps adults?

Answer 16

small intestine

Question 17

In which organ would you expect to find Taenia crassiceps larvae?

Answer 17

larval stages (cysticerci) in abdominal cavity of intermediate hosts (small rodents)

Question 18

Why is infection of Taenia crassiceps in humans potentially serious?

Answer 18

Infection of Taenia crassiceps in humans is potentially serious because of the proliferative nature of the cysticerci. When a human ingests the oncosphere from dog feces, a cysticercus can develop and often infects the eye, leading to blindness

Question 19

What are some clinical signs associated with* Taenia crassiceps*?

Answer 19

Infection in the final host is usually asymptomatic

Question 20

What is/are the final host(s) for Taenia pisiformis?

Answer 20

dogs, wolves, and foxes

Question 21

What is/are the intermediate host(s) for Taenia pisiformis?

Answer 21

rabbits

Question 22

Describe the life cycle of Taenia pisiformis

Answer 22

Gravid taeniid segments are shed from the carnivore final host. Segments release eggs in the environment, which develop to oncospheres. The oncosphere is ingested by the intermediate host (rabbits), enters the wall of the small intestine and migrates to its organ of predilection, which is the liver and peritoneum.

Here it develops to a second-stage larva (cysticercus), which is infective to the final host. After the final host ingests the cysticercus, it is digested and develops in the small intestine to an adult tapeworm. PPP is 56 days.

Question 23

What is the PPP for Taenia pisiformis?

Answer 23

~ 56 days

Question 24

What is/are the site(s) of infection for Taenia pisiformis?

Answer 24

Adult tapeworm in small intestine of the final host. Larval stage (cysticercus) in liver and peritoneum of intermediate host.