parasitology platyheminths

Question 1

2 classes of platyhelminthes

Answer 1

cestoda (tapeworm)
trematoda (flukes)

Question 2

platyhelminthes general characteristics

Answer 2

Flat mostly
Hermaphrodites
Definitive host diagnosis: eggs
At least 1 intermediate host

Question 3

cestoda

Answer 3

phylum platyhelminthes (Flat mostly, Hermaphrodites, At least 1 intermediate host)
TAPEWORM
Segmented (can cut up and they will live), often long
Adults in host GI tract, almost always small intestine
Worms have no intestine, absorb nutrients across surface
Adults often nonpathogenic but people repelled

Question 4

cestoda adults body divisions

Answer 4

Scolex (holdfast)
* Suckers and/or hooks NO MOUTH
* Attaches to gut wall

Neck
* Region of cell division, gives rise to proglottids

Proglottids (segments)
* Segments mature as they travel down the chain
* Oldest segments at the posterior end

Question 5

cestoda segments

Answer 5

Each segment has at least one set of all reproductive organs of both sexes
Classified as:
* Immature
* Mature
* Gravid: contains fully developed eggs

Maturation occurs as moves down the chain
Common tapeworms shed gravid segments

Question 6

Metacestode

Answer 6

General term for larval tapeworm
each species has its own name for this
INFECTIVE STAGE

Question 7

cestodes general lifecycle

Answer 7

1. eggs from adult tapeworm in definitive host passed into environment
2. eggs eaten by intermediate host
3. metacestode in intermediate host eaten by definitive host

Question 8

taeniidae family

Answer 8

cestoda (platyhelmith)
Vertebrates are definitive and intermediate hosts
* Definitive host: predator mammal
* Intermediate host: herbivore or omnivore mammal—prey

Segments square to rectangular in shape
In general, larval stages (metacestode) most important, adults have little significance
Eggs passed from the host in segments
* Usually infection recognized from seeing segments
* Eggs seen infrequently in fecal exams
* Look the same for all family members
* Fecal flotation often negative because eggs in the segments

Two common/important metacestodes:
* Cysticercus
* Hydatid

Question 9

non taeniidae families

Answer 9

cestoda (platyhelminths)
Invertebrate intermediate host, vertebrate definitive host

Question 10

Cysticercus

Answer 10

metacestode (infective larvae) of taeniidae
Fluid-filled bladder
1 Inverted, invaginated scolex
1 Cysticercus produce 1 adult tapeworm in the DH
Infection/disease called cysticercosis

Question 11

Hydatid

Answer 11

metacestode (infective larvae) of taeniidae
Fluid-filled bladder lines by a delicate parasitic membrane
Heads detach from wall into cyst fluid
Secondary cysts are formed as invaginations on the walls
1 hydatid produces up to thousands adult tapeworms
Infection/disease called hydatidosis

Question 12

Taenia taeniaeformis

Answer 12

taeniidae (platyhelminths)
Common tapeworm of hunting cats
Eggs shed in segments
IH: Rodent, metacestode (Strobilocercus) in liver

CAT- MOUSE

Question 13

Taenia pisiformis

Answer 13

taeniidae (platyhelminths)
Definitive host: canids
Egg shed in segments
IH: Rabbits

DOG- RABBIT

Question 14

Echinococcus

Answer 14

taeniidae (platyhelminths)
Very small adults: 3-6 mm
* only 3 segments

Metacestode stage: Hydatid
Undergoes asexual reproduction
1 egg= Multiple scoleces formed
Potential for thousand of scolices to form

Question 15

Echinococcus multilocularis

Answer 15

echinococcus, taeniidae (platyhelminths)
Life cycle
* Definitive host: Fox, sometimes dog, rarely cat
* Intermediate host: Small rodents, including lagomorphs
* Humans, dogs, and pigs: aberrant or accidental IH
* Metacestode: alveolar cyst (multilocular cyst)

Difficult to remove surgically because grows invasively

this is his fav parasite :)

Question 16

Taenia saginata

Answer 16

5-15 m
Human/cattle
Cysticerci in bovine muscle (0.6 mm)

HUMAN-CATTLE

Question 17

T/F? Tapeworms use their suckers for feeding?

Answer 17

F

Question 18

What is the general name used for cestode larval stages?

Answer 18

metacestodes

Question 19

Where will you find metacestodes?

Answer 19

intermediate host

Question 20

Non taeniids

Answer 20

platyhelminths, cestodes
Belong to several different families (we’ll only see Dipylidiidae and Anoplocephalidae)
Use arthropod as intermediate hosts
Metacestode stage called cysticercoid: small cyst with invaginated single scolex, no fluid filled bladder

Question 21

cysticercoid

Answer 21

Metacestode stage of non taeniids
small cyst with invaginated single scolex, no fluid filled bladder

Question 22

Dipylidium caninum

Answer 22

non taeniid (cestode, platyhelminth)
15-70 cm
Most common tapeworm of dogs and cats in the US
Gravid segments released containing egg packets
Indirect life cycle, IH: fleas. Lice an uncommon IH
Flea larvae ingest egg packets, cysticercoid develop before flea become adult
Infection of DH follows ingestion of flea
PPP: 2-3 weeks
usually non pathogenic

Question 23

diagnosis of Dipylidium caninum

Answer 23

but tapeworm segments in perianal area or around feces, where animal sleeps
eggs not seen on fecals

Question 24

Dipylidium caninum - Clinical importance

Answer 24

Infection generally subclinical
Zoonotic, young children most likely to be infected, but very uncommon
Flea control critical to prevent reinfection

Question 25

Ruminant and equine tapeworm life cycle

Answer 25

1. **Gravid segments released** containing eggs 2. Eggs are ingested by the **IH: Oribatid mites** in pasture (coprophages) 3. **Cysticercoid in mites** 4. DH infected when **ingest infected mites** while grazing

Question 26

Anoplocephala perfoliata

Answer 26

**equine tapeworm** Very common infection Short tapeworm cluster at **ileocecal junction** Usually **asymptomatic** * Occasionally causes inflammation and ulceration * In most severe cases associated with perforation, intussusception **Difficult to diagnose** * Surprisingly, segments not seen in manure * Eggs usually not present on fecal exam * Because diagnosis is difficult, horses routinely treated at least once/year * Infection can’t practically be prevented

Question 27

Moniezia benedeni

Answer 27

cattle tapeworm non taeniiae

Question 28

Moniezia expansa

Answer 28

small ruminant tapeworm non taeniiae

Question 29

ruminant tapeworms

Answer 29

Moniezia benedeni (Cattle) and Moniezia expansa (Small ruminants) Very common infection Diagnosis * Frequently see **segments in manure**, especially young animals * **Eggs in fecal exams**: shape square M. benedeni: square M. expansa: triangular

Question 30

trematoda

Answer 30

platyhelminths flukes

Question 31

dignena

Answer 31

trematoda (flukes), platyhelminths **Leaf shaped** Unsegmented 1-2 suckers Operculated eggs passed in feces: usually diagnosed with fecal exam Usually 2 IH, **first IH is ALWAYS a snail**

Question 32

trematode life cycle

Answer 32

1. Most **fluke eggs must hatch in water** 2. Larvae (miracidium) swim to specific **snail host** 3. Some flukes use land snails, egg ingested by snail 4. **Asexual development in snail** (sporocysts and redias) 5. Next **larval stage produced by snail (cercaria)** 6. Usually swims to pasture 7. Become the **infective stage (metacercaria)** – **sometimes in environment, sometimes in second IH** 8. Metacercaria can be ingested by a paratenic host 9. **DH is infected when ingests metacercaria** | eggs > miracidium > sporocyst> redias > cercaria > metacercaria >DH

Question 33

miricidium

Answer 33

1st larval stage of trematodes swim to snail

Question 34

Fasciola hepatica and Fascioloides magna

Answer 34

**ruminant liver flukes** Adults in **liver and bile ducts** of host Fasciola: **ruminants**, rabbits, humans, dogs, others Fascioloides: white-tailed deer

Question 35

Fasciola hepatica - Life cycle

Answer 35

trematode, platyhelminth 1. Adults **release eggs that hatch in water** 2. **First IH: Lymnaeid snails** (asexual reproduction) 3. **Cercariae encyst** on vegetation and become in **metacercaria** 4. **Ingested by DH** 5. Larval fluke migrate to **liver** 6. After several weeks **enter bile and mature** **PPP: 3-4 months**

Question 36

Fasciola hepatica - Clinical importance

Answer 36

In ruminants can cause **chronic poor doing** May have **acute disease** (especially small ruminants) associated with **liver migration** (mechanical damage) Diagnosis by egg detection—sedimentation technique Control difficult because hard to eradicate snails

Question 37

Fascioloides magna

Answer 37

trematode, platyhelminth **normal host: deer** Larvae cause **serious disease in sheep and goats** because keep migrating around liver until animal dies Sheep and goats are abnormal hosts Hard to control