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CBio 4500/6500
Medical Parasitology
Spring Semester 2012
Medical Parasitology
 Lectures on Tuesdays & Thursdays in the second period
9:30-10:45 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 during the semester & a final
covering the entire material (30%,30%, & 40%)
 [email protected], [email protected]
Medical Parasitology
 The class web site can be viewed at
http://www.striepen.uga.edu/medpara/schedule.html
 There is a link to this site through the UGA ELC site
 The site features the syllabus & schedule, lecture notes
and links to further web resources
 ‘Voices from the Vanguard’ lecture series (once a
month Tuesdays 6 pm in the Chapel)
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
Some book suggestions
(for some of these titles newer editions might be available)
Summer job for highly skilled and very
hard-working undergrad
Google: Biology of Parasitism and MBL
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 website provides links)
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 are/were very
common in temperate climates
 Overall there is a much stronger association with the
level of housing, nutrition, sanitation and general
public health than climate. Parasitic diseases are in
their majority the diseases of the poor around the
globe. Poverty is a major risk factor for disease – but
disease is also a major contributor to poverty.
Medical Parasitology
GNP
per capita
(1995)
$0-70
$0-70
$1941-2580
$1941-2580
Malaria
Index
00
33
Outline of the 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 cutting edge
science with a focus on new molecular concepts
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
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).
Is the mighty lion a
despicable parasite?
The benefit in the
relationship between
lion and wildebeest
seems highly skewed
in favor of the lion
Who is a parasite?
Parasites are usually
much smaller than
their hosts, they also
do not kill before they
eat.
Is a mosquito a parasite?
 The border between
parasitism and micropredation 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
Parasites are found in all
groups of organisms
“Parasites” a very diverse
set of eukaryotic pathogens
 Parasitology as a scientific discipline historically covers a
diverse collection of multi- 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)
Note that the phylogeny in this tree
has flaws and is just used to show diversity
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.
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.
Obligate/facultative, and
permanent/intermittent parasites
 Most parasites 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
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 nonetheless
Disease terminology
Disease terminology
 Patency, Incubation period, Acute & Chronic,
Convalescence
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
Number of people infected/affected
by parasitic diseases
Diseases causing
high mortality:
Diseases causing
morbidity & QL losses:
Malaria (400M)
Sleeping Sickness (0.5 M)
Chagas (18M)
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)
Visceral Leishmaniasis (4M)