CBio 45006500

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CBio 4500/6500

• Medical Parasitology
• Spring Semester 2008

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Medical Parasitology

• Lectures on Tuesdays Thursdays in the second
  period 930-1045 a.m.
• Please initial the attendance sheet each class
• You may not miss more than 3 classes without
  detriment to your grade
• There will be 2 exams within the semester a
  final exam covering the entire material (30,30,
  40)
• striepen_at_cb.uga.edu, smoreno_at_cb.uga.edu

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Medical Parasitology

• The class web site can be viewed at
  http//webs.cb.uga.edu/striepen/medpara
• Please note that this is NOT WebCT
• The site features the syllabus schedule,
  lecture notes and links to further web resources

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Some book suggestions(for some of these titles
newer editions might be available)

• Roberts Janovy, Foundations of Parasitology,
  McGraw-Hill, 7th Ed. 2004
• Markell, John, Krotoski, Medical
  Parasitology,Saunders, 8th Ed. 1999
• Chiodine, Moody, Manser, Atlas of Medical
  Helminthology and Protozoology,Churchhill
  Livingstone, 4th Ed. 2001
• Peters Gilles, A Colour Atlas of Tropical
  Medicine Parasitology, Wolfe, 3rd Ed. 1989
• Bogitsh, Carter, Oeltmann, Human Parasitology,
  Elsevier, 3rd Ed., 2005

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Some book suggestions(for some of these titles
newer editions might be available)
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websites

• There are thousands of web sites providing
  information and images on parasites, not all of
  them are as trustworthy as one could wish
• Two excellent sites to look for general
  information and material for visual illustration
  are CDC Division of Parasitic Diseases, and WHO
  Tropical Disease Research Program (course web
  site provides links)

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Medical Parasitology

• Medical Parasitology focuses on parasites which
  cause disease in humans. Parasites are also of
  great importance in veterinary medicine.
• Several diseases falling it this field only occur
  in the tropics, but many parasite disease were
  very common in temperate climates until the
  beginning to mid 20th century
• Overall there is a much stronger association with
  the level of sanitation and general public health
  than climate. Parasitic diseases are in their
  majority the diseases of the poor around the globe

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Medical Parasitology
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Outline of class

• Brief introduction into concepts and terminology
  of parasitology, vector biology, immunology
  public health (4 lectures)
• Helminth diseases (flukes, tape worms round
  worms) (9 lectures)
• Diseases caused by unicellular eukaryotes often
  referred to as protozoa (e.g. sleeping sickness
  malaria) (13 lectures)
• Lectures will combine biology of the parasites
  and vectors, pathogenesis of the disease,
  treatment and prevention of diseases, and control
  efforts
• Where possible we will try to include new cutting
  edge science with a focus on new molecular
  concepts

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Parasitism - a way of life

• Parasite and Parasitism are ecological terms that
  define a way of life rather than a coherent and
  evolutionary related group of organisms
• Symbiosis, Commensalism, Mutualism, Parasitism

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Parasitism - a way of life

• Parasite and Parasitism are terms that define a
  way of life rather than a coherent and
  evolutionary related group of organisms
• Symbiosis Any two organisms living in close
  association, commonly one living in or on the the
  body of the other, are symbiotic, as contrasted
  with free living. De Bary 1879
• Commensalism Sharing the table. One partner
  benefits but the other is not hurt.
• Mutualism Both partners benefit.
• Parasitism One partner (the parasit) harms or
  lives on the expense of the other (host).

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Is the mighty lion a despicable parasite?

• The benefit in the relationship between lion and
  wildebeest seems highly skewed in favor of the
  lion

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Who is a parasite?

• Parasites are usually much smaller than their
  hosts, they also do no kill before eating.

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Is a mosquito a parasite?

• The border between parasitism and micro-predation
  is blurry
• Parasites usually live in a very intimate
  relationship with their host depending on more
  than food from it
• The host is food source and more or less
  permanent habitat at the same time
• Many parasites show strict specificity for a
  single host

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Parasites are found in all groups of organisms
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Parasites a very diverse set of eukaryotic
pathogens

• Parasitology historically covers a diverse
  collection of metazoan and unicellular eukaryotic
  organisms
• Protozoa unicellular eukaryotes (this is a
  historic term, protozoans are not really a
  monophyletic group)
• Platyhelminthes flatworms these include flukes
  and tape worms
• Nematodes elongated worms with rigid cuticula
• Arthropodes insects, ticks and mites which
  either are parasitic or transmit parasites as
  vectors
• (we only have time to discuss the most important
  groups causing human disease, there are many
  additional parasites outside these groups)

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Note that the phylogeny in this tree has flaws
and is just used to show diversity
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Ecto- Endoparasitism

• Ectoparasites live on, but not in their hosts
  (they can nevertheless cause severe illness). Ich
  a protozoan ectoparasite of the skin of a fish.
• Endoparasite live within the body and tissues of
  their hosts. Trypanosomes (which cause sleeping
  sickness) within the blood of an infected animal.

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Infection infestation

• Infectious diseases are caused by transmittable
  parasitic agents including bacteria, viruses,
  fungi, protozoa and a variety of metazoans
  commonly referred to as helminths or worms
• Infection usually implies replication of the
  agent resulting in a growing number of pathogens
• Infestation are characterized by a constant
  number of pathogens. Severity of disease often
  depends on infection dose.

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Obligate/facultative, and permanent/intermittent
parasites

• Most parasite are obligate parasites
• In some species only some life cycle stages, e.g.
  the larvae are parasitic, in others parasitic and
  free living generations can alternate depending
  on environmental conditions (Strongiloides
  stercoralis) .

Indirect
Direct
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Hosts and life cycles

• The definitive host is by definition the one in
  which the parasite reproduces sexually
• Additional hosts are then designated intermediate
  hosts
• Host which actively transmit parasites to humans
  are often called vectors
• In paratenic or transport hosts no parasite
  development occurs
• Reservoir host are alternate animal host from
  which the parasite can be transmitted to humans
  (zoonosis) or domestic animals
• Accidental host, not suitable for parasite
  development, but severe disease might ensue non
  the less

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Disease terminology
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Disease terminology

• Prepatency infected but parasite presence can
  not be detected yet
• Patency established infection, parasite stages
  can be detected (malaria parasites in blood
  smears, worm eggs in feces etc.)
• Incubation period time between infection and the
  development of symptoms
• Acute disease can lead to crisis which can
  resolve in spontaneous healing, chronic infection
  or death
• Convalescence Period after healing, absence of
  infectious agents, no symptoms, in certain case
  immunity to reinfection

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Number of people infected/affected by parasitic
diseases

• Diseases causing
• high mortality
• Malaria (400M)
• Sleeping Sickness (0.5 M)
• Chagas (18M)
• Visceral Leishmaniasis (4M)

• Diseases causing
• morbidity QL losses
• Geohelminths (2B)
• Water Foodborne Protozoans (1.5B)
• Schistosomiasis (200M)
• Lymphatic filariasis (120 M)
• Cysticercosis (?50M)
• Onchocerciasis (18M)
• Cutaneous Leishmaniasis (8M)
• Guinea worm (4M, now 60K)