1. CURRENT ADVANCEMENT IN
PARASITE TREATMENT AND
CONTROL
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2. INTRODUCTION
 Often said that we are living in ‘post-genomic era’.
1) Vaccination
2) DNA/ RNA technology
- Antisense DNA and RNA
3) Nanotechnology
4) Quantum dots
5) Remoting Sensing (RS) and GIS technology
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3. VACCINES AGAINST PARASITIC DISEASES
 Drugs may provide a complete cure for an infection but
reinfection is often an almost certainty.
 Wherever parasite exposure is regular occurrence, long
lasting protection can only come from the development of
protective immune response.
 The purpose of vaccination is to stimulate a protective
immune response without the risks associated with a
natural infection.
3

4.  For parasite vaccination effectiveness, we need to
understand the biology and life cycle of parasite and also
how the immune response is mounted against it.
 For example: anti-sporozoite vaccine.
- would block new infections with malaria
- very useful for people who have never been exposed to
the disease and are visiting an endemic region
- reduce the chances of those already infected from
acquiring more serious infection through repeated
challenges.
- however, it will not help to cure an existing infection 4

5.  The nature of the host immune response to parasite
challenge is a crucial factor in the development of an
effective vaccine
 More complex organism, and much more difficult to
determine suitable target for vaccine preparations
5

6. TYPES OF VACCINES
1) Attenuated – live non-virulent organism
2) Killed – Dead pathogen
3) Sub-unit – Antigenic pathogen
4) Toxoid – Inactivated toxin
5) DNA – specific gene (s)
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7. ATTENUATED VACCINES
 Utilise live organisms that are biologically the same as the
‘wild type’ pathogen but do not induce disease or only
cause mild symptoms.
 Can be obtained
1) through the selection of non-pathogenic strains
2) through treatment of the wild type with mutagens or
passage through laboratory animals or cell cultures.
 The injected organism will grow and multiply within the
host thus exposing it to a variety of different life cycle
stages. 7

8.  Elicit an immune response similar to that of the pathogen
but without its associated pathology.
 More likely to induce a T cell-mediated immune response
than a killed vaccine and this is important for combating
intracellular parasites.
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9.  Problem
1) the real concerns over whether attenuated pathogen might
revert back to ‘wild type’ and revert disease.
2) Many organisms cannot be grown in culture
3) Those that can be cultured change their phenotype over
successive generations so that they become less like the
‘wild type’ and genetically more dangerous.
 Example – a vaccine against Ancylostoma caninum was
developed in the 1960s and entered commercial production
in 1970s.
 Gave up 90% protection but was withdrawn because
sometimes give rise to patent infections
 Also due to expensive production costs and short shelf life 9

10.  Example of vaccines:
1. An anti-Leishmania attenuated vaccine
2. An anti-Theileria annulata vaccine to treat cattle
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11. KILLED VACCINES
 Involve growing the pathogen in culture and then killing it
before using it as a vaccine.
 Obviously overcomes some of the safety worries
associated with live vaccines.
 If the pathogen produces toxin, this must be removed
during vaccine preparation.
 This vaccine only limited to those parasites that can be
grown under culture conditions 11

12.  Depend on the biochemically characterizing the pathogen
 Then testing different component for their ability to induce
an immune response
 Once candidate has been identified, it can purified from
cultured parasites.
 Example – Vaccine against Plasmodium, Leishmania,
Neospora caninum, Toxoplasma gondii, Cryptosporidium
parvum.
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13. SUB UNIT/ RECOMBINANT VACCINES
 Enable large amount of specific antigens to be produced
without the problems of parasite culture.
 Particularly useful for protozoan life cycle stages that can
normally only obtained in very small numbers and for
helminth parasites.
 The antigen are isolated from the rest of the pathogen
and therefore they are potentially much safer than ‘live’ or
‘killed’ vaccines.
13

14.  For cestode, recombinant sub-unit vaccines have been
developed but for various reasons they not yet enter
commercial production.
 For example, there is an effective recombinant antigen
vaccine that prevents the development of the cysticerci of
Taenia ovis in sheep.
 This vaccines was develop to reduce the prevalence of
cycticercosis in older lambs before there were sent to
slaughter.
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15. TOXOID VACCINES
 Toxoid or anti-toxin vaccines are used where the toxins
produced a pathogen are the main virulence factor.
 The vaccine is prepared by isolating the toxin and then
inactivating it, for example using treatment formaldehyde.
 Because the chemical mimics the toxin biochemically, but
it is not actually active, it is called a ‘toxoid’.
 Example the diphtheria and tetanus toxoids in DPT
vaccine.
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16.  Parasite normally release antigenic excretory/secretory
products that have been explored as potential vaccine
candidates.
 These are the complex mixtures that often contain
cysteine proteases which play an important part in the
nutrition and the pathology they cause.
 Example: Vaccines using cycteine proteases have been
designed against protozoa Trypanosoma cruzi, trematode
Fasciola hepatica, nematode Haemonchus contortus and
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Ostertagia ostertagia.

17. DNA VACCINES
 Prepare by cloning a gene that codes for a specific
antigen into bacterial plasmid or recombinant viral factor
that is then injected into subject.
 Promoter sequences are also incorporated into the
plasmid to boost the production of antigen.
 The immune response to DNA vaccination has been
investigated using mice but not clear whether similar
response are generated in other animals.
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18.  The DNA vaccine stimulating both cellular and humoral
immune response.
 Cheaper to develop and than ‘live’ attenuated and subunit
vaccines.
 Relatively more stable and can be stored at room
temperature.
 Vaccines are formulated with a variety of substances that
help to preserve the active ingredient and have
immunostimulatory properties. 18

19.  Quite difficult to transfer candidate vaccine from
laboratory situation to the field.
 This is because DNA vaccines not generating as strong
response in humans and domestic animals as they do in
mice.
 However progress was being made in the development of
DNA vaccines against protozoa Plasmodium and
Leishmania, trematode Schistosoma japonicum,
nematode Haemonchus contortus and arthropod
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Boophilus microplus.

20. VACCINE ADMINISTRATION
 Normally are given as an injection that may be:
- intravenous
- intramuscular
- intradermal
 Injections are seldom popular because they cause painful or
systemic flu-like reactions
 Some can be swallowed e.g oral polio vaccine  increasing on
the possibility of delivering vaccines as nasal spray
 Oral vaccines and nasal spray are much more ‘patient friendly’
20

21.  New technique – using accelerated liquids or powder
grains.
 The injection takes as little as 40 msec using a high
pressure jet
 This cause a little damage to underlying tissues, reduces
the risk of needle borne-contamination and, virtually pain-
free.
 Needle-free injections often provide a greater antibody
response than conventional injections 21

22.  Example: anti-malaria vaccine.
 Gene-guns are needle free delivery systems used to
deliver DNA or RNA attach to gold nanoparticles.
 The gold nanoparticles are accelerated to supersonic
speed in a stream of helium gas and forced into
subcutaneous skin.
 Using gene gun gave an equivalent response to
intramuscular injections. 22

23. DNA/ RNA TECHNOLOGY
 One of the fundamental discoveries in recent years is that epigenetic
mechanisms are responsible for many aspects of cell regulation.
 Epigenetic factors are the those mechanisms that regulate genetic
expression without changing the DNA sequence .
 Epigenetic regulation is important in all organisms and has particular
relevance for host parasite relationships because its governs:
1) The host’s immune response
2) The parasite’s life cycle
3) Virulence
4) Ability to overcome the host’s immune system
5) Adapt to drug
 Potential target because may prove possible to selectively target
unique epigenetic pathways in parasites without harming the host.
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24.  Epigenetic factors include
1. DNA methylation
2. histone modification
3. regulatory RNA molecules.
 DNA methylation occurs through the addition of methyl groups
to cytosine to produce 5-methylcytosine.
 Normally takes place at CpG sites (cytosine-phosphate-
guanine).
 Extensive methylation of CpG sites within a gene sequence
results in the gene being silenced. 24

25.  Chromatin consists of DNA wrapped around the large
structural protein histone.
 If the sequence of amino acids that comprise histone is
modified, it alters the three dimension shape of the
molecule
 This affects the expression of gene activity of the
associated DNA.
 Histone modification can occur in several different ways
e.g acethylation or methylation
 These have different effects on gene expression.
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26.  There are variety of single and double stranded RNA
molecules and small non-coding micro RNA molecules
that are involved in the regulation of gene expression at
the level of translation such as RNA interference (RNAi).
 RNAi regulates gene activity and is also part of cell’s
natural means of protection against virus.
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27.  Specific double-/ stranded RNA is cleaved by ribonuclease
enzyme called ‘dicer’ to form small (short) interfering RNA
(siRNA) consisting 20-25 nucleotides
 The siRNA is then assembled to form an ‘RNA-induced
silencing complex’ (RISC) that includeds the antisense
strand of the target mRNA and endonuclease enzyme.
 The silencing complex binds to the mRNA and then the
endonuclease enzyme (‘Argonaute’) brings about its
degradation.
 mRNA not translated and the protein is codes for it not
formed.
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28. 28

29. ANTISENSE DNA AND RNA
 Within a cell, the first step in the production of a protein is
when the gene coding for it in the cell’s DNA is
transcribed into a sequence of messenger RNA (mRNA)
oligonucleotides.
 The single-stranded mRNA molecule then moves to
ribosomes where it is translated into a sequence of amino
acids.
 The ‘mRNA’ is referred to as a ‘sense’ strand while its
non-coding complementary strand is the ‘antisense
strand’.
 For example if the ‘sense’ strand had the sequence 5’-
AACGAAUUAC-3’, its antisense strand would be 3’-
UUGCUUAAUG-5’ 29

30.  If sense and antisense strands came into contact,  bind
together to form a non-functional duplex molecule.
 Consequently the sense strand would not be translated
and the protein molecule is coded for would not be
formed.
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31. NANOTECHNOLOGY
 Nano materials are solid colloidal particles 1-100 nm in
diameter.
 Can be manufactured from elements such as gold, silver
and carbon, from compounds such as iron oxide as well
as from organic polymers such as chitosan.
 For example, gold nanoparticles have been used as a
carrier of hydrophobic drugs and by conjugating an
antibody to the surface of the particles, they can used to
target specific cells.
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32.  Raman reporters or ‘Raham tags’ are molecules that are
excited when stimulated by specific wavelenghts.
 When Raman reporters are attached to gold nanoparticles,
they can be visualised after administration using a technique
called Surface Enhanced Raman Spectroscopy.
 Consequently, the location of parasite can be determined using
gold nanoparticles bearing the appropriate antibodies and
Raman reporters.
 Certain type of gold nanoparticles convert absorbed light into
near infra-red radiation and have potential for laser
photoablation
 The basic of this approach is that the nanoparticles are
targeted to specific cell types, then a laser beam is directed
onto them. 32

33.  This approach was used to kill tachyzoites of Toxoplasma
gondii.
 Alternatively, a laser can deliver a specific wavelenghts
that stimulates gold nanoparticles that have reached their
target to release bound molecules, such as drugs.
 This ensures that the target cells experience a sudden
therapeutic dose of the drug.
 However most potential applications are still at the
experimental stage.
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34. Diagram of the silica-encapsulated surface- Diagram of the SERS-based sandwich immunoassay.
enhanced Raman spectroscopy (SERS) tag. Antibody-conjugated SERS tags serve as labels for the
biological analyte and are captured by
superparamagnetic beads which are also functionalized
with antibodies specific to the analyte. A Raman laser
34
strikes the SERS tags, generating a unique spectrum
that easily identifies analytes.

35.  Some issues:
1. Difficult to handle in both liquid and dry formation
2. Substances are safe in particular size range may
become poisonous or carcinogenic at another size
3. Silver is toxic metal, and silver nanoparticles could
potentially affect microbial and invertebrate communities
4. Gold nanoparticles could accumulate through food
chains
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36. QUANTUM DOTS
 Quantum dots are nanocrystal semiconductor that are of
great interest for their electronic and optical
characteristics
 In biology, they have many potential uses for bioimaging
because they can be attached to molecules or cells
 Thereby their movements to be tracked in real time.
 For example, quantum dots have been used to monitor
the invasion of erythrocytes by Plasmodium falciparum
and as tools to identify Plasmodium-infected erythrocytes
using flow cytometry.
 Can be delivered gene silencing RNA (riRNA).
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37.  Also prove useful in the treatment of parasitic diseases.
 However, more information is required on their
toxicological properties.
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38. Quantum dot (QD) labelling on P. falciparum-infected erythrocytes showing that only late-stage iRBCs are
labelled.
Early-stage (ring) iRBCs (A) are not labelled by the QD, while the late-stage trophozoite (B) and segmented
schizont (C) iRBCs are both labelled.
The parasites were stained with Hoechst 33324 (in red, first column from the left) and PCQD (in green, 38
second column).
Phase contrast images (third column) and merged images (fourth column) are also shown. Bars, 5 mm.

39. REMOTING SENSING (RS) AND GIS TECHNOLOGY
 Remote sensing (RS) satellite data and Geographic
Information Systems (GIS) technology
 useful for monitoring the epidemiology of parasites
 forecasting the risk of disease outbreaks
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40. REMOTE SENSING (RS)
 RS is a means of monitoring the environment without actually
making physical contact with it
 Commonly achieve through satellite technology using
combination of passive and active monitoring devices.
 Passive detectors emit particular wavelengths that are emitted
or reflected from land beneath.
 Active detectors emit particularly wavelengths and measure
the time taken for them to return
 RS can be useful to monitor:
 temperature
 ground cover
 forestation
 etc
 A variety of RS satellite datasets are available including 40
LANDSAT, MODIS, NDVI, and SRTM DEM.

41. GEOGRAPHIC INFORMATION SYSTEMS (GIS)
 GIS are means of capturing, storing, updating, retrieving,
analyzing, and displaying any form of geographically-
referenced digital information.
 It is not a single entity but a collection of computer
hardware, software, and geographical data.
 Very useful for parasite surveillance and simulating the
consequences of particular intervention strategies or
changes in the environment.
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42.  To map simultaneously one or more of the following on
either a regional, national, or global scale:
 the occurrence of the parasite
 the disease it causes
 its host
 vector/ intermediate host
 co-infections
 environmental variables
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43.  For example, disease maps are quick and simple means
of visualising spatial and temporal ‘hot spots’ of
- where disease is clustering
- the linkages between parasite distribution and
environmental variables
- the effectiveness of the control measures
 Can identify those environmental variables that promote
the breeding of vectors and the intermediate hosts and
therefore where problems are likely to arise.
 GIS software  e.g DIVAGIS  already used to identify
areas suitable for colonisation by the snail intermediate 43
hosts of Fasciola hepatica

44. Fasciola gigantica potential distribution and abundance in the IGADD sub-
region based on a GIS constructed from FAO CVIEW agroecologic zone map
files, 30-year-average monthly climate databases, a modification of the LSU 44
climate based parasite forecast system, a base life cycle development
temperature of 16°C and known irrigation zones.