Parasitism

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Parasitism
Parasites are organisms that live in or on
another organism i.e. the host.
What do parasites gain?
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• Parasites gain -
• Nutrition - absorbed from the hosts tissues and
  fluids, or from the intestine itself

• Parasites can be -
• ECTOparasites - live on the outside of the body
  e.g. head louse (suck blood from the scalp of the
  host)
• ENDOparasites - live inside the host e.g. blood
  flukes, roundworms, tapeworms

• Hosts can be -
• Plants, animals and even bacteria (infected by
  bacteriophages)
• The host does not gain and can be harmed

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Characteristics of parasites

• Can penetrate the host to gain entry
• Can attach itself to the host
• Have protection against the immune system of the
  host
• Show degeneration of unnecessary organ systems
  e.g. gut
• Produce vast numbers of eggs to increase chance
  of reaching a new host
• Use a vector or intermediate host to reach a new
  host
• Produce resistant stages to survive outside the
  host

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Construct a chart to summarise 9 features - 1.
Name of parasite 2. Entry to host 3. Attachment
devices 4. Resistance to hosts immune system
5. Organ degeneration 6. Transfer to immediate
host 7. Reproduction 8. Method of feeding 9.
Symptoms and treatment
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Head louse - Pediculus
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1. Name of parasite - Pediculus (head louse) 2.
Entry to host - ectoparasite 3. Attachment
devices - claws for grasping hair, eggs (nits)
glued to base of hairs 4. Resistance to hosts
immune system - none 5. Organ degeneration -
wingless insect 6. Transfer to immediate host -
walk from one hair to another and transfer by
close hair to hair contact 7. Reproduction -
large numbers of eggs 8. Method of feeding - suck
blood form scalp capillaries 9. Symptoms and
treatment - itching of scalp/ insecticides in
lotions, creams, liquids
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Blood fluke - Schistosoma
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1. Name of parasite - Schistosoma (blood
fluke) 2. Entry to host - snail releases larvae
into water bore into skin
veins liver/lungs
capillaries of bladder/ intestine 3. Attachment
devices - suckers in adults 4. Resistance to
hosts immune system - thick cuticle 5. Organ
degeneration - no sense organs or respiratory
system 6. Transfer to intermediate host eggs
into water larvae hatch in water and enter
snails released into water from
digestive system 7. Reproduction - large number
of eggs released in faeces/ urine 8. Method of
feeding - red blood cells 9. Symptoms and
treatment - schistosomiasis/ bilharzia enlarged
spleenliver, intestinal damagebleeding,
lethargy / prescribed drugs
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Roundworm - Ascaris
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1. Name of parasite - Ascaris (roundworm) 2.
Entry to host - ingested eggs hatch into
larvae blood vessels
lungs/ alveoli penetrated coughed
up and swallowed gut 3. Attachment
devices - 3 lips around mouth 4. Resistance to
hosts immune system - thick cuticle 5. Organ
degeneration - no respiratory system 6. Transfer
to immediate host -eggs ingested from
faeces-contaminated food or water, from hands
contaminated from soil (usually found in
children) 7. Reproduction - large number of eggs
(200,000 per day) 8. Method of feeding - absorb
from blood and gut 9. Symptoms and treatment -
slow growth and slow weight gain, abdominal pain
/ prescribed drugs result in egestion
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Tapeworm - Taenia solium
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1. Name of parasite - Taenia solium (pork
tapeworm) 2. Entry to host - eating infected
uncooked meat (pork) 3. Attachment devices -
suckers and hooks into the gut wall 4. Resistance
to hosts immune system - thick cuticle and
inhibitory secretions to withstand intestinal
conditions e.g. acid 5. Organ degeneration - no
organs of movement or sense organs, simplified
digestive system, no respiratory system 6.
Transfer to immediate host - eggs have resistant
coats and are ingested from faeces by pigs
larvae develop in pig muscle and remain dormant
until eaten by human 7. Reproduction - large
number of eggs 8. Method of feeding - absorb from
the gut directly 9. Symptoms and treatment -
anaemia, diarrhoea, loss of weight, intestinal
pain / prescribed drugs and meat inspection