Transcript Sex and Behaviour * Immune Response to Parasites

Sex and behaviour:
Macroparasites & Microparasites
CfE Advanced Higher Biology
Unit 2: Organisms and Evolution
SQA mandatory key area
• Macroparasites: endoparasitic amoebas,
platyhelminths, nematodes. Ectoparasitic
arthropods. Ectoparasitic Transmission through
direct contact, consumption of secondary hosts or
endoparasitic transmission by vectors.
Schistosomiasis and malaria.
• Microparasites: viruses and bacteria. Human
diseases: influenza, HIV/AIDS and tuberculosis.
• Viral structure and replication. Antigenicity.
• RNA retroviruses and reverse transcriptase.
MACROPARASITES
Endoparasites and Ectoparasites
Transmission of
macroparasites of main body cavities
• Ectoparasites and endoparasites of the main
body cavities, such as the gut, are generally
transmitted by direct contact or through
consumption of secondary hosts.
Consumption of
secondary host
• Eg. Larval helminths:
Direct
contact
Transmission of macroparasites of the
body tissues
• Macroparasitic endoparasites of the body tissues
(e.g. trematodes e.g shistosomiasis (flukes,
Platyhelminthes), parasitic protozoa – eg.
Plasmodium - malaria) are often transmitted by
vectors.
•
http://www.biology.ualberta.ca/parasites/ParPub/themes/attach/l080502.htm
Macroparasites vs microparasites
• The main distinction between microparasites and
macroparasites is whether they “multiply” within
their definitive host or not.
• Microparasites do “multiply” in their definitive host,
and macroparasites do not “multiply” in their
definitive host.
• This distinction is important because it influences the
ecology and epidemiology of micro and
macroparasitic infections.
Multiply vs reproduce
• Both microparasites and macroparasites may
reproduce in the definitive host.
• However, in macroparasites, reproduction usually
leads to the production of eggs or larval stages that
then leave the definitive host. That is, reproduction
occurs, but the host does not end up with more
parasites.
• Microparasites use direct reproduction; reproduction
leads to an increase in the number of parasites
within the host.
Macroparasite – endoparasite vs
ectoparasite
• 1. ECTOPARASITE
• Parasites that live on the outside of the host,
either on the skin or the outgrowths of the
skin, are called ectoparasites.
• (Your gut is actually, developmentally speaking, the
outside of your body so the parasites that inhabit the
gut can also be considered ectoparasites).
2. Endoparasites
• Those that live inside the host are
called endoparasites (including all parasitic
worms). Endoparasites can exist in one of two
forms:
• intercellular parasites (inhabiting spaces in
the host’s body)
• intracellular parasites (inhabiting cells in the
host’s body).
Macroparasite example: Platyhelminth
http://upload.wikimedia.org/wikipedia/commons/4/4
d/Metagonimus_LifeCycle.gif
Macroparasite example: Schistosomiasis
http://upload.wikimedia.org/wikipedia/commons/f/
fb/Schistosomiasis_Life_Cycle.png
Vectors
• You will have noticed that the two previous
examples are spread by a vector, an organism
that does not cause disease itself but which
spreads infection by conveying pathogens
from one host to another.
• Which organism would be the vector in each
case?
Microparasites
• A microparasite completes a full life cycle within
one host and can be transmitted directly
to conspecific hosts. They often reproduce within
a host's cells and are generally too small to be
seen with the naked eye.
• Most are viruses, bacteria and fungi with a
smaller number being protists.
• Microparasite examples: viruses and bacteria.
Human diseases: influenza, HIV/AIDS and
tuberculosis.
Viruses
• Viruses are infectious agents that can only replicate
inside a host cell. Viruses contain genetic material in the
form of DNA or RNA, packaged in a protective protein
coat.
• Some viruses have a lipid membrane surround derived
from host cell materials. The outer surface of a virus
contains antigens that a host cell may or may not be able
to detect as foreign.
• RNA retroviruses use the enzyme reverse transcriptase to
form DNA, which is then inserted into the genome of the
host cell. This virus gene forms new viral particles when
transcribed.
How do
viruses
replicate?
http://www.nature.com/nrmicro/jou
rnal/v1/n3/images/nrmicro775-i1.gif
Viruses can also replicate within bacteria – phage
virus
Activity H
Macroparasites vs microparasites
Suitable search engines to use:
http://www.sciencedirect.com/
http://scholar.google.co.uk/
Challenges in Treatment and Control
• Key Areas:
• Challenges in the design of vaccines and drugs
including rapid antigen change and similarities
between host and parasite metabolism.
• Sanitation and vector control: overcrowding,
natural disasters, tropical climates, developing
countries, child mortality.
Tutorial – Challenges in Treatment and
Control
• Prevention of population cycles by parasitic
removal
• Article you need for the tutorial:
• http://www.sciencemag.org/content/282/539
7/2256.full