5. 6/12/2013
1. CONDENSER lens
focuses light on the
specimen
2. Light then passes
through OCULAR &
OBJECTIVE lenses
Magnified Image
Bright field Microscope
9. 9
Visualization of Parasites
• Hand lens /magnifying glass
– helminth adults, arthopods
• Light Microscopy
– Low power x10 – helminth eggs
– High power x40 – protozoan cysts &
trophozoites
– Oil immersion x100 – protozoa eg. malaria
Technique depends on the degree of
magnification needed.
SIZE OF THE PARASITE
10. 10
Biological classification
Carolus Linnaeus – 18th century
(Systema naturae - 1735)
Grouped species according to
shared physical characteristics.
Introduced
Binominal classification:
Genus & species
eg. Homo sapiens
11. 11
First sorted into large groups and thereafter
subdivided to contain fewer and fewer organism
but sharing more and more common features
Biological classification - by Linnaeus - 18th century
Kingdom
Phylum
Family
Class
Order
Genus
species
Genus species
Binomial system
Plasmodium falciparum
Naming organism
Scientific names
italicize OR underline
13. 13
Virus = an infectious
agent, consisting of genetic
material DNA or RNA wrapped up
in a protein coat.
100 x smaller than bacteria
Invades living cells and uses
them to keep itself alive and to
replicate itself.
Some viruses can cause life-
long and chronic infections
eg. Herpes viruses
Viruses
14. Viral classification
• DNA or RNA
• Size and Morphology
• Susceptibility to physical & chemical agents
• Symptoms
• Pathology
• Host and tissue tropism
• Transmission
• Immunological properties
27. 27
• 200 million cases of malaria annually
• Killed more humans than any other disease.
• 1 million deaths /year. 90% in sub-Saharan
Africa, an African child dies of malaria every 30
sec.
• Over half the world's
population live in
malarious areas
Malaria
Finger prick screening for
MP = Malarial Parasite
33. 33
NEMATODES
Cylindrical
Sexes separate- male smaller
Muscular outer wall - organs are suspended in a
false body cavity (pseudo coelom)
4 moults in Life Cycle
INTESTINAL
TISSUE
cuticle
muscle layer
body
cavity
34. 34
Enterobius vermicularis
(kiri panuwa)
Transmitted from
person to person
GEOHELMINTHS
(soil transmitted worms)
Ascaris lumbricoides
Trichuris triciura
Strongyloides stercoralis
Hookworms–
Necator americanus (In SL)
Ancylostoma duodenale
Commonest helminthiases (worm infections) in SL
Nematodes
35. 35
Whipworm = Trichuris trichiura
Soil transmission similar to Ascaris
+ direct feco -oral
Trichiuris eggs Trichiuris adults Ascaris adults
40. 40
Features common to Cestodes 1
• Morphology: Flat, ribbon like.
• Location: Adults in intestinal tract of
vertebrates.
• Size
Echinococcus granulosus
Taenia
few milimeters 10 metres
41. 41
• Head: “Scolex”/ “Hold-fast” organ - attach to host’s
intestine
• Scolex: sucking grooves, hooks or suckers
• Hermaphrodite: segments have both testes &
ovaries (male & female together)
• No alimentary tract: absorption through body wall.
Features common to Cestodes 2
42. 42
Trematodes- flat & leaflike,
sexes not separate
(except in blood flukes)
• Water borne
[Schistosomes = blood flukes]
• Food borne
[tissue flukes]
43. 43
Class- Trematodes
• Blood Flukes• Tissue Flukes
Tissue flukes
hermaphroditic
Schistosomes
2 sexes are
separate
44. 44
ARTHROPODS 1
1. Mosquitos- transmit most important vector borne
diseases in Sri Lanka
2. Lice - Head louse & body louse
- Pubic louse
transmit Louse-borne relapsing fever, Epidemic typhus,
Trench fever
3. Fleas - transmit plague, murine typhus
4. Flies - sand fly – transmit leishmaniasis
CLASS INSECTA