Platyhelminthes

Question 1

what is a metazoan parasite

Answer 1

a multicellular animal which has a body made up of differentiated cells which are arranged into tissues and organs, includes all animals excluding sponges

Question 2

briefly outline the phylum platyhelminthes

Answer 2

a metazoan parasite made up of Cestodes, Treamatodes and monogenea which live inside their host
- worm like organisms which live and feed off living hosts disrupting the hosts nourishment absorption causing weakness and disease

Question 3

outline physical characteristics of platyhelminthes and which three classes are considered parasitic

Answer 3

simple, bilateral with unsegmented invertes
acoelomate(no body cavity)
no specialised circulatory or respiratory organs

Cestoda
Trematoda
Monogenea

Question 4

outline the class cestoda in the phylum platyhelinthes

Answer 4

common name= Tapeworms
= adults live in digestive tract of vertebrates
= juviniles often live in tissues of animals
= made up of a scolex (head) which can have bothria (tenticles), sucking cups and hooks for attachment
made up of proglottids (body) composed of successive segments

Question 5

outline the class trematoda in the phylum platyhelminthines

Answer 5

made up of two subclasses
1) Digenea= syncitial tegument, no body cavity, anterior and posterior suckers, obligate parasxites of molluscs and fish, 6000 spp to date

2) Aspidogastrea= between 80-100 spp, obligate parasites of molluscs, turtles and fish

Question 6

outline the class monogenea in the phlum platyhelminthes

Answer 6

• small parasite flatwrom less than 20cm
• ecotoparasitic on skin/gills of fish
• marine forms larger than those on fresh water hosts
• lack respiatory, skeletal and circulatory systems
• no/weakly developed oral suckers
• attaches using hooks/clamps
• able to elongate and shorten as they move

Question 7

how are cestodes aka tapeworms transmitted

Answer 7

the consumption of infected tissue e.g. unprepared meat

consumption of infective eggs

Question 8

outline the anatomy of a cestode/tapeworm

Answer 8

body composed of successive segments called proglottids which are very thin which use flame cells for excretion. Proglottid segments contain both male and female reproductive parts and mature further down the organisms with mature proglottids being released at the posterior end leaving in host faeces

scolex makes up the head which can have accessory parts such as hookers/suckers to bind to host

Question 9

how do cestodes gain nutrients

Answer 9

once anchored to the hosts intestinal wall they absorb nutrients through the skin as the food being digested by the the host flows past it and the organism grows with proglottids containing their own digestive ad reproductive tract

Question 10

briefly outline the Lifecyle of cestodes

Answer 10

eggs or gravid proglottids passed to feces where eggs survive for days/ motnhs
cattle and pigs become infected when they ingest contaminated vegetation
in animal intestine oncospehres hatch and invade intestinal wall, migrating to striated muscles where they develp into cysticerai where they can survive for years
human then eats raw/undercooked meat

Question 11

outline the medical importance of human cysticercosis caused by tapeworms

Answer 11

most people with a tapeworm infection have no symptoms but patients with T.aginata tend to have more compared to those with T.solium as it is larger in size
can cause ab pain, appetite loss, weight loss or upset stomach
can result in human cysticercosis where parasite forms cysts in muscles

Question 12

how are cestodes/tapeworms treated and diagnosed

Answer 12

diagnosed: microscopic examination of eggs in stool using iodine stains , passing of proglottids, abdominal pain

treatment= drug called praziquantel which interrupts calcium receptors in tegument paralysing worm allowing it to be passed by normal peristaltic moevment

Question 13

what three species cause human taeniasis

Answer 13

1) beef tapeworm = T.saginata = doesnt cause cysticercosis
2) pork tapeworm= T.solium = causes cysticercosis
3) Asian tapeworm = T.asiatica
humans = only defintive host = unclear if it causes

Question 14

what is human echinococcosis aka hydatid disease

Answer 14

caused by larval stages of genus echinococcus from the class cestodes
E.granulosus causes cystic echinococcus
E. multicocularis causes alveolar echinococcus
= IT IS LARVAL STAGES WHICH CAUSE THIS DISEASE

Question 15

How is Echinococcus treated and controlled

Answer 15

• control of dog population e.g. shooting or poison
• dog worming = control the adult echinoccuccs
• sterilise sheep organs before feeding to dogs
  = CONTORL
• humans= surgery or chemotherpay

Question 16

outline the anatomy of the class trematode from the phylum platyhelminthes

Answer 16

typicall two vertical suckers one on anterior and one ventral, oral sucker surrounds mouth and ventral blind to muscular organ

syncitical tegument = large membrane filled with cytoplams which surrounds the animal which may help prevent host digestive enzymes from killing the organisms

2 testes and 1 ovary usually

Question 17

outline trematode/fluke biology

Answer 17

• possesses a terminal or subterminal mouth where a muscular pharynx provides the force for ingesting food
• has a forked, blind digestive system consisting of two tubular sacs called caeca
• pinocytosis/phagocytosis by syncytial tegument
• graze on the contents of the lumen and food ingested by the host, bile and mucus across mucosal wall

Question 18

outline trematode biology

Answer 18

molluscan intermediate host which is an obligate stage in the life history, without the molluscan host no parasite can occur

vertebrates are the definitive host

Question 19

compare the subclass Digenea from trematodes to monogenean

Answer 19

D= two attachment points, oral and ventral suckers
indirect life cycle- one definitive host and at least one intermediate host
up to six larval stages possible

M= one organ of attachment at the haptor with arrangement of hooks, clamps or suckers
direct life cycle one host only
usually one larval form

Question 20

what are blood flukes

Answer 20

a type of trematode unlike other digenean trematodes which live in the alimentary canal with a molluscan intermediate host

humans= S.mansoni, S.haematobium, S,intercalatum, s.mekongi and S.japonicum

snail intermediate host = Biomphalaria spp and Bulinus spp

Question 21

how do blood flukes infect humans

Answer 21

when skin comes in contact with contaminated fresh water as the infectious form of parasite known as cercarie emerge from snails contaminating water aka swimmers itch

Question 22

outline how Schistosoma manosni species from blood flukes/treamatodes reproduce

Answer 22

not hermaphrodites, separate sexes
the female is larger and male lives in a grove beneath the female providing sperm

Question 23

outline the monogenean lifecycle

Answer 23

direct lifecycle with the parasite being free living so no intermediate host
produces operculate eggs which contaminate next host

Question 24

what are the two subclasses of monogeneans based on their body plan

Answer 24

1) monopisthocotylea
2) ployisthocotylea
based on the complexity of their body plan

Question 25

what is a haptor

Answer 25

an attachment organ on the monogenean parasites located on posterior end of the organisms