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Diagnosis of Parasitic Diseases: Old and New Approaches

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Methods for the diagnosis of infectious diseases have stagnated in the last 20-30 years. Few major advances in clinical diagnostic testing have been made since the introduction of PCR, although new technologies are being investigated. Many tests that form the backbone of the "modern" microbiology laboratory are based on very old and labour-intensive technologies such as microscopy for malaria. Pressing needs include more rapid tests without sacrificing sensitivity, value-added tests, and point-of-care tests for both high- and low-resource settings. In recent years, research has been focused on alternative methods to improve the diagnosis of parasitic diseases. These include immunoassays, molecular-based approaches, and proteomics using mass spectrometry platforms technology. This review summarizes the progress in new approaches in parasite diagnosis and discusses some of the merits and disadvantages of these tests.
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Hindawi Publishing Corporation
Interdisciplinary Perspectives on Infectious Diseases
Volume 2009, Article ID 278246, 15 pages
doi:10.1155/2009/278246
Review Article
Diagnosis of Parasitic Diseases: Old and New Approaches
Momar Ndao
National Reference Centre for Parasitology, McGill University Centre for Tropical Diseases, Montreal General Hospital,
1650 Cedar Avenue R3-137, Montreal, QC, Canada H3G 1A4
Correspondence should be addressed to Momar Ndao, momar.ndao@mcgill.ca
Received 31 May 2009; Accepted 29 August 2009
Recommended by Herbert B. Tanowitz
Methods for the diagnosis of infectious diseases have stagnated in the last 20–30 years. Few major advances in clinical diagnostic
testing have been made since the introduction of PCR, although new technologies are being investigated. Many tests that form the
backbone of the “modern” microbiology laboratory are based on very old and labour-intensive technologies such as microscopy
for malaria. Pressing needs include more rapid tests without sacrificing sensitivity, value-added tests, and point-of-care tests for
both high- and low-resource settings. In recent years, research has been focused on alternative methods to improve the diagnosis of
parasitic diseases. These include immunoassays, molecular-based approaches, and proteomics using mass spectrometry platforms
technology. This review summarizes the progress in new approaches in parasite diagnosis and discusses some of the merits and
disadvantages of these tests.
Copyright © 2009 Momar Ndao. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Currently, the detection and diagnosis of parasite infections
rely on several laboratory methods in addition to clinical
symptoms, clinical history, travel history, and geographic
location of patient. The primary tests currently used to
diagnose many parasitic diseases have changed little since
the development of the microscope in the 15th century
by Antonie van Leeuwenhoek. Furthermore, most of the
current tests cannot distinguish between past, latent, acute,
and reactivated infections and are not useful for following
response to therapy or for prognosis.
Recent developments in new diagnostic tools, however,
have opened new avenues for a vast improvement in parasite
detection. Firstly, a number of newer serology-based assays
that are highly specific and sensitive have emerged, such
as the Falcon assay screening test ELISA (FAST-ELISA) [1],
Dot-ELISA [2,3], rapid antigen detection system (RDTS)
[4], and luciferase immunoprecipitation system (LIPS)
[5]. Secondly, molecular-based approaches such as loop-
mediated isothermal amplification (LAMP) [6], real-time
polymerasechainreaction[7], and Luminex [8] have shown
a high potential for use in parasite diagnosis with increased
specificity and sensitivity. Thirdly, proteomic technology has
also been introduced for the discovery of biomarkers using
tissues or biological fluids from the infected host.
The aim of this review is to highlight the poten-
tial for these new technologies in parasite diagnosis. For
convenience, old and new parasitic diagnostic tools are
summarized in Tables 1and 2. The diagnostic tools oered
by the CDC (Centre for Disease Control, Atlanta, USA)
and the NRCP (National Reference Centre for Parasitology,
Montr´
eal, Canada) are also highlighted in Tables 3and 4.
2. Microscopy
For many years, microscopy has been the only tool available
for the detection of parasites through inspection of blood
smears [1014], tissue specimens [1517], feces, lymph
node aspirates [18,19], bone marrow [20], and even cere-
brospinal fluid [21]. However, sample preparation for direct
observation is time-consuming, labour intensive, and proper
diagnosis depends on qualified laboratory technicians. In
the case of slide reading, a second independent reading is
preferable, but not always required for accurate diagnosis. If
need be, divided readings are resolved by a third reader. In
endemic regions, where resources are limited, this proves to
2 Interdisciplinary Perspectives on Infectious Diseases
Tab le 1: Diagnostic tools for the detection of specific blood-borne parasitic diseases.
African
trypanosomiasis Babesiosis Chagas
disease Leishmaniasis Malaria Toxoplasmosis
Trypanosoma
brucei
Babesia
microti
Trypanosoma
cruzi
Leishmania
species
Plasmodium
species
Tox oplas ma
gondii
MICROSCOPY [23][10][11][12][13]—
SEROLOGY-
BASED
ASSAYS
————
ELISA [24,25][26][2730]— — [31]
FAST-ELISA — [32,33]—
Dot-ELISA or
Dipstick [34]—[35][2,18]— —
RIPA-ELISA — [36,37]— —
DHA or IHA [38]—[18]— —
DFA or IFA [39][40,41]— — [42][43]
Immunoblot — [44,45]— — [46]
PRISM — [47]— —
RDT — [48]—[49]—
MOLECULAR-
BASED
ASSAYS
————
PCR [23][50,51][5254][55][56][57,58]
RT-PCR [59]—[6062][4,56][63]
QT-NASBA — [64][65,66]—
RT-QB-NASBA — [67]—
LAMP [68]—[69]—[7074]—
Luminex — [75]—
PCR-ELISA — [62,76][7779]—
OC-PCR [80]—[81]— —
PROTEOMICS — — — —
Mass
Spectrometry
(LDMS,
MALDI-TOF,
SELDI-TOF)
[82,83]— — —[8486]—
FAST-ELISA: Falcon assay screening test; RIPA-ELISA: radioimmunoprecipitation assay; DHA or IHA: direct or indirect hemagglutination assay; DFA or
IFA: direct or indirect immunofluorescence assay; RDT: rapid diagnostic test; LIPS: luciferase immunoprecipitation system; CATT: Card Agglutination test
for Trypanosomiasis; PCR: polymerase chain reaction; RT-PCR: real-time polymerase chain reaction; QT-NASBA: quantitative nucleic acid sequenced-based
amplification; RT-QT-NASBA: real-time quantitative nucleic acid sequenced-based amplification; LAMP: loop-mediated isothernal amplification; OC-PCR:
oligochromatography Polymerase chain reaction; LDMS: laser desorption mass spectrometry; MALDI-ToF: matrix-assisted laser desorption/ionization time
of flight; SELDI-Tof: surface-enhanced laser desorption/ionization time of flight, IFA: immunofluorescent assay, EIA: Enzyme immunoassay, RT-PCR: Real
time PCR, IB: immunoblot.
be dicult and misdiagnosis can significantly impact patient
care. In reality, all major intestinal helminth infections
are still solely dependent on microscopy for diagnosis. As
for other parasite infections, many are confirmed by the
use of microscopy in conjunction to other methods of
diagnosis including serology-based assays and more recently
molecular-based assays.
3. Serology-Based Assays
In situations where biologic samples or tissue specimens are
unavailable, serology alone is the gold standard for diagnosis.
Serology-based diagnosis tools can be divided into two
categories: antigen-detection assays and antibody-detection
assays. These include the enzyme-linked immunosorbent
assay (ELISA), also called enzyme immunoassay (EIA), and
all its derived tests such as the Falcon assay screening
test ELISA (FAST-ELISA) and the dot-ELISA. Other assays
include the hemagglutination (HA) test, indirect or direct
immunofluorescent antibody (IFA or DFA) tests, comple-
ment fixation (CF) test, and immunoblotting and rapid
diagnostic tests (RDTs).
Although the ease of use and turnaround times for
serologic assays are similar to microscopy, serology-based
Interdisciplinary Perspectives on Infectious Diseases 3
Tab le 2: Diagnostic tools for the detection of specific intestinal parasitic diseases.
PROTOZOA TREMATODES CESTODES NEMATODES
Cryptosporidiosis Fasciolosis Schistosomiasis Taeniasis/
Cysticercosis Hydatidosis Filariasis Strongylodiasis
Cryptosporidium
parvum, C. hominis
Fasciola
hepatica, F.
gigantica
Schistosoma
mansoni Taenia solium
Echinococcus
granulosus, E.
multilocularis
Wuchereria
bancrofti,
Brugia
malayi, B.
timori, Loa
loa
Strongyloides
stercoralis
MICROSCOPY [87][88][89]—[90][91][92]
SEROLOGY
BASED ASSAYS ——
ELISA [93,94][88,95][96,97][98101][102106][14][107111]
FAST-ELISA — [112][1]—
Dot-ELISA or
Dipstick —[113,114][115]—[116,117][118120]—
DHA or IHA [121]—[122][123][124]
DFA or IFA [93,125,126]— — —[127,128]
Immunoblot — [112][129][130,131][122]— [132]
LIPS — [133][134]
MOLECULAR-
BASED
ASSAYS
——
PCR [135,136]—[137,138][139,140]—[141143][144]
RT-PCR [145147]—[148,149]— — [150]
LAMP [151,152]— — [153]—— —
Luminex [154]———
PCR-ELISA — [155]—
OC-PCR — [156]————
PROTEOMICS —
Mass
Spectrometry
(LDMS,
MALDI-TOF,
SELDI-TOF)
—[157]—[158]—— —
Abbreviations: see Tab le 1.
Tab le 3: Diagnostic tools for the detection of specific blood-borne parasitic diseases oered by the CDC and the NRCP.
African
trypanosomiasis Babesiosis Chagas disease Leishmaniasis Malaria Toxoplasmosis
Trypanosoma
brucei species Babesia microti Trypanosoma cruzi Leishmania
species
Plasmodium
species
Tox oplas ma
gondii
CDC
DIAGNOSTIC
TOOLS
Microscopy Microscopy IFA,
PCR
Microscopy
culture, IFA, EIA
Microscopy,
Culture, IFA
Microscopy
PCR, IFA
Microscopy IFA,
EIA
NRCP
DIAGNOSTIC
TOOLS
Microscopy,
culture, CATT,
PCR
Microscopy, IFA
Microscopy,
culture, EIA,
RT-PCR
Microscopy,
Culture, IFA,
RT-PCR
Microscopy,
IFA, IB, PCR RT-PCR
CDC: Centre for Disease Control, Atlanta, Georgia, USA. NRCP: National Reference Centre for Parasitology, Montreal General Hospital, Montreal, Quebec,
Canada. Abbreviations: see Tab le 1.
4 Interdisciplinary Perspectives on Infectious Diseases
(a)
(b)
(c)
Figure 1: Microscopy. Comparison of Trypanosoma cruzi trypo-
mastogote (a) with Plasmodium malariae schizont (b) and with
microfilaria (c: Mansonella perstans) in squirrel monkey blood
smear. Giemsa stain: 70x oil-immersion objective (a) and (b)
and 27.2x objective (c), adapted with permission of Comparative
Medicine from [9].
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Optical density (492.6nm)
Negative
control (kit)
ELISA
negative
ELISA +/ELISA
positive
Positive
control (kit)
Figure 2: Serology-based assays: ELISA. Enzyme-linked
immunosorbent assay (ELISA) absorbance values for antibodies
to T. cruzi in monkey samples. Median values are indicated by
horizontal lines within the boxes; the 25th and 75th percentiles
are enclosed by the boxes; the 5th and 95th percentiles are
enclosed by the bars outside the boxes. Adapted with permission of
Comparative Medicine from [9].
M12345678
Figure 3: Molecular-based assay: PCR. Example of PCR results
obtained for seven monkey samples, using the TCRUZ primers.
BloodsampleswereprocessedasdescribedinMaterialsand
Methods. The PCR products were electrophoresed in a 2% agarose
gel and stained with ethidium bromide. The 168 bp band (arrow)
is the expected T. cruzi-specific product. The 360 and 550 bp are
also specific products resulting from amplification of two or three
of the 195 bp repeats found in tandem arrays in the T. cr uzi genome.
Lanes 1 to 6 contain the amplification products of DNA from
T. cruzi-infected monkeys; 7, blood from noninfected monkey; 8,
negative control (distilled water); and M, 100bp ladder, adapted,
with permission of Comparative Medicine from [9].
assays are more sensitive and specific. It becomes important
for individuals whose blood smears do not permit identifi-
cation of the parasite (e.g., dierentiating between Babesia
and Plasmodium)[159] or for patients exhibiting low-
parasitemia and/or who are asymptomatic (e.g., Chagasic
patients) [54]. Classifying an infected asymptomatic patient
as negative could lead to transmission of the parasite during
blood transfusions or organ transplants. In the case of
Fasciola infection, serology tests have also been shown to be
useful in the confirmation of chronic fascioliasis when egg
production is low or sporadic [112]. Finally, having these
tests readily available allows for the monitoring of parasite
clearance following therapy.
3.1. Falcon Assay Screening Test ELISA (FAST-ELISA). The
Falcon assay screening test ELISA (FAST-ELISA) consists
of using synthetic and recombinant peptides to evaluate
antibody responses to an antigen [1]. In the past, the method
has been applied to the study of malaria [32], fasciolosis
[112], schistosomiasis (reviewed in [160]), and taeniasis
[161]. However, this technique is subjected to the same
drawbacks as most serology-based tests. Antibodies raised
against a peptide from one parasite protein may cross-react
with proteins from other species. Moreover, antibodies raised
against a peptide may react in some assays but not in others
and some regions of a peptide may be more immunogenic
than others. No recent studies have been published on the use
of the FAST-ELISA for the diagnosis of parasitic infections.
Interdisciplinary Perspectives on Infectious Diseases 5
Tab le 4: Diagnostic tools for the detection of specific intestinal parasitic diseases oered by the CDC and the NRCP.
PROTOZOA TREMATODES CESTODES NEMATODES
Cryptosporidiosis Fasciolosis Schistosomiasis Taeniasis
Cysticercosis Hydatidosis Filariasis Strongylodiasis
Cryptosporidium
parvum, C. hominis
Fasciola
hepatica, F.
gigantica
Schistosoma
mansoni Taenia solium
Echinococcus
granulosus, E.
multilocularis
Wuchereria
bancrofti,
Brugia
malayi, B.
timori, Loa
loa
Strongyloides
stercoralis
CDC DIAG-
NOSTIC
TOOLS
Microscopy, EIA,
PCR, RT-PCR Microsocopy,
FAST-ELISA, IB Immunoblot, IB Microscopy,
EIA Microscopy, EIA
NRCP DIAG-
NOSTIC
TOOLS
Microscopy, EIA Microscopy,
EIA Microscopy, EIA IB EIA Microscopy,
EIA
Microscopy,
culture, EIA, IB
CDC: Centre for Disease Control, Atlanta, Georgia, USA. NRCP: National Reference Centre for Parasitology, Montreal General Hospital, Montreal, Quebec,
Canada.
3.2. Dot-ELISA. The main dierence between the regular
ELISA and the dot-ELISA lies in the surface used to bind
the antigen of choice. In the dot-ELISA, the plastic plate is
replaced by a nitrocellulose or other paper membrane onto
which a small amount of sample volume is applied. The
choice of binding matrix greatly improved the specificity and
sensitivity of the assay by reducing the binding of nonspecific
proteins usually observed when plastic binding matrixes
are used. The principle is similar to the immunoblot. The
dotted membrane is incubated first with an antigen-specific
antibody followed by an enzyme-conjugated anti-antibody.
The addition of a precipitable, chromogenic substrate causes
the formation of a colored dot on the membrane which can
be visually read [2]. The benefits of this technique include its
ease of use, its rapidity, and the ease of result interpretation.
It is fast, and cost-eective and more importantly can be used
in the field (e.g., as a dipstick). For all these reasons, the Dot-
ELISA has been and still is extensively used in the detection
of human and animal parasitic diseases, including amebiasis,
babesiosis, fascioliasis, cutaneous and visceral leishmania-
sis, cysticercosis, echinococcosis, malaria, schistosomiasis,
toxocariasis, toxoplasmosis, trichinosis, and trypanosomiasis
(all reviewed in [3]). In the last few years, published
studies have demonstrated the use of the dot-ELISA for the
detection of Fasciola gigantica [113], Haemonchus contortus
[162], Theileria equi [163], Trypanosoma cruzi [164], and
Trypanosoma brucei [34]. In the latter study the researchers
were able to demonstrate that the dot-ELISA had better
sensitivity and specificity than the ELISA in the detection
of antineurofilament and antigalactocerebrosides antibodies
in cerebrospinal fluid of subjects infected with African
trypanosomes. They attributed the greater sensitivity and
specificity of the dot-ELISA to the use of the nitrocellulose
membrane and showed that their assay was successfully
reproducible in the field.
3.3. Rapid Antigen Detection System (RDTS). Rapid antigen
detection tests (RDTs) based on immunochromatographic
antigen detection have been implemented in many diagnos-
tic laboratories as an adjunct to microscopy for the diagnosis
of malaria. RDTs consist of capturing soluble proteins by
complexing them with capture antibodies embedded on a
nitrocellulose strip. A drop of blood sample is applied to the
strip and eluted from the nitrocellulose strip by the addition
of a few drops of buer containing a labeled antibody. The
antigen-antibody complex can then be visualized directly
from the membrane [4].
Since the appearance of the first RDTs in the 990s, major
improvements have been made to the technique, making the
use of RDTs in rural endemic regions feasible. RDTs are
now rapid, stable at temperatures up to 40C, easy to use,
and cost-eective thereby providing many advantages over
traditional microscopic methods [165]. RDTs are useful in
the identification of P. falciparum and P. v iv a x infections but
cannot be used to identify P. ma l a r i a e and P. o v ale infections
[4]. In addition, they are useless at detecting very low-density
infections. PCR-based approaches remain the tool of choice
in that situation. More than 80 RDTs exist for the detection of
either histidine-rich protein (HRP) specific to P. falciparum
or species-specific isotypes of lactate dehydrogenase (LDH)
[49]. However, as reported by Murray et al. [165]only23
have met the WHO’s criteria for international marketing.
Malaria RDTs have recently been introduced in African
countries to help prevent misdiagnosis of malaria infections
and to subsequently reduce the practice of presumptive
treatment [49]. In fact, the tendency to treat slide-negative
samples with antimalarials is still a common phenomenon.
This practice causes concern not only for the patient’s
health care but also to the costs it generates in prescribing
the more expensive antimalarial sulfadoxine/pyrimethamine
and artemisinin-based combinations [165]. Finally, misuse
of antimalarials could lead to the appearance of drug-
resistant strains.
6 Interdisciplinary Perspectives on Infectious Diseases
3.4. Luciferase Immunoprecipitation System (LIPS). The
luciferase immunoprecipitation system (LIPS) is a modified
ELISA-based assay in which serum containing antigen-
specific antibodies can be identified by measuring light
production. Basically, an antigen of choice is fused to the
enzyme reporter Renilla luciferase (Ruc) and expressed as
a Ruc-fusion in mammalian cells to allow for mammalian-
specific posttranslational modifications. The crude protein
extract is then incubated with the test serum and protein
A/G beads. During the incubation, the Ruc-antigen fusion
becomes immobilized on the A/G beads, which allows the
antigen-specific antibody to be quantitated by washing the
beads and adding coelenterazine substrate and measuring
light production [5].
In recent years, LIPS has been successfully applied for
the identification of sera samples infected with Strongyloides
stercoralis (using a Ruc-NIE fusion) [134]andLoa loa (using
a Ruc-LlSXP-1 fusion) [133]. Some of the advantages of
the LIPS technology include its rapidity and accuracy in
detecting infected patients. Sensitivity is improved in part by
the use of mammalian cells which produce fusion antigens
free of contaminating bacterial proteins. In addition, low
backgrounds are produced compared to the ELISA. This
greatly facilitates the separation between negative and pos-
itive samples. In addition, the Strongyloides LIPS based on
the NIE antigen showed greater specificity than the ELISA
as no cross-reaction was observed with serum from filarial-
infected subjects [134].
A LIPS assay can be performed in 2.5 hours. Burbelo
et al. 2008 [133] were able to obtain 100% specificity and
sensitivity when performing an LIPS assay based on the
Loa loa SXP-1 antigen with only a small-degree of cross-
reactivity with a few Onchocerca volvulus-andWuchereria
bancrofti-infected patient sera. By decreasing the incubation
times of a normal LIPS assay, they were able to minimize
cross-reaction. Many of the O. volvulus sera samples tested
as positive with the LIPS assay were negative using this 15-
minute LIPS assay also called QLIPS. Of interest for the
application of this technique in the field is the observation
that blood obtained by finger-prick (contaminated with red
blood cells and other components) did not interfere with the
LIPS assay. Further studies will be useful in exploring and
validating the accuracy and potential usefulness of the LIPS
and QLIPS assays in the field.
As discussed, immunodiagnostics tests have some
serious limitations. Parasitic diseases such as amebiasis,
cryptosporidiosis, filariasis, giardiasis, malaria, cysticercosis,
schistosomiasis, and African trypanosomiasis do not have
commercially or FDA approved antibody detection tests
for their diagnosis. Experimental results have been too
variable due to the type of antigen preparations used (e.g.,
crude, recombinant purified, adult worm, egg) and also
because of the use of nonstandardized test procedures.
Cross-reaction leading to false-positives and misdiagnosis is
also a problem, especially in regions where more than one
parasite is endemic. Despite the fact that some parasites in
South America share common epitopes, it is common to see
coinfection with Trypanosoma cruzi and Leishmania species
[166]. It is also a problem in Africa, where cross-reactivity
exists between filarial and other helminth antigens [133]. To
a lesser extent but nonetheless important is the inability of
antibody-detection tests to dierentiate between past and
currently active infections [167]. Furthermore, antibody-
detection tests cannot be used in parasitic infections
that do not develop a significant antibody response.
This has been observed in some individuals carrying
Echinococcus cysts [168] or during cutaneous leishmaniasis
(http://www.dpd.cdc.gov/dpdx/HTML/Leishmaniasis.htm).
Similarly, in the case of African trypanosomiasis diagnosis,
such tests are of limited use because seroconversion occurs
only after the onset of clinical symptoms [83].
For all these reasons, there is still a need to improve on
the current diagnosis approaches available. Since the advent
of the polymerase chain reaction (PCR), parasitologists have
turned to molecular-based approaches in the hopes to better
the existing diagnosis tools.
4. Molecular-Based Approaches
4.1. Nucleic Acid-Based Approaches. The many limitations
of microscopy and serology-based assays have influenced
parasitologists towards the use of gene amplification meth-
ods made possible with the advent of the polymerase
chain reaction (PCR). Besides the traditional PCR, including
nested and multiplexed PCR, we have seen the implemen-
tation of the real-time PCR (RT-PCR) for the detection
of several parasitic infections. Newer technologies such as
loop-mediated isothermal amplification and Luminex-based
assays have also emerged as possible new approaches for the
diagnosis of parasitic diseases.
Molecular-based approaches based on nucleic acids oer
greater sensitivity and specificity over the existing diagnostic
tests. They permit the detection of infections from very
low parasitized samples including those from asymptomatic
patient’s samples [169]. Moreover, multiplexed PCR allows
for the detection of multiple sequences in the same reaction
tube proving useful in the diagnosis of several parasitic
infections simultaneously [170].
4.2. Real-Time Polymerase Chain Reaction (RT-PCR). RT-
PCR system unlike conventional PCR, allow for the quantifi-
cation of the original template’s concentration through the
use of various fluorescent chemistries, such as Sybergreen,
Taqman probes, fluorescence resonance energy transfer
(FRET), and Scorpion primers [7]. The concentration is
measured through comparison to standard curves. This
eliminates the need to visualize the amplicons by gel
electrophoresis thereby greatly reducing the risk of contam-
ination and the introduction of false-positives. When mul-
tiplexed, RT-PCR allows for the high-throughput analysis of
dierent sequences in one single-closed tube reaction [171].
Using multiplexed RT-PCR, Shokoples et al. [4]wereable
to identify the four human Plasmodium species (falciparum,
vivax,malariae,andovale) in a single reaction tube even in
very low parasitized samples. Running the multiplex assay
not only reduced the cost per test but also allowed for a
rapid turnaround time, the assay taking only three hours to
Interdisciplinary Perspectives on Infectious Diseases 7
complete. It is a clear advantage over microscopy which is
labour intensive and time-consuming with slow turnaround
times especially during high-throughput settings. Similarly,
multiplexed RT-PCR proved useful in dierentiating drug-
sensitive strains of malaria [172]. This is important for
proper antimalarial prescription. In another example, Diez
et al. [54]wereabletodetectthepresenceofT. cruzi infec-
tion following heart transplants using PCR. This allowed
immediate treatment of the patients before reactivation of
Chagas disease could occur. These examples demonstrate
that ecient and early diagnosis can directly impact patients
care and that PCR-based approaches have the potential to
help in making the right choice for treatment.
Although DNA-based methods have shown excellent
sensitivity and specificity, the introduction of these methods
in daily laboratory practice is still uncommon especially in
rural endemic regions. In addition, as observed with many
serology-based assays, PCR-based methods also suer by
the lack of standardization [22]. DNA extraction, choice of
primer sets, and use of various amplification protocols are
all factors that may cause this diversification in results [173].
Adding an automated DNA extraction step would certainly
improve PCR assays for use in the diagnosis of parasitic
diseases.
4.3. Loop-Mediated Isothermal Amplification (LAMP). Loop-
mediated isothermal amplification (LAMP) is a unique
amplification method with extremely high specificity and
sensitivity able to discriminate between a single nucleotide
dierence [6]. It is characterised by the use of six dierent
primers specifically designed to recognise eight distinct
regions on a target gene, with amplification only occurring if
all primers bind and form a product [174]. In the past, LAMP
has been successfully applied for the rapid detection of both
DNA and RNA viruses such as the West Nile [175]and
SARS viruses [176]. Recently, parasitologists have adapted
the LAMP approach for the detection of several parasitic
diseases including the human parasites Entamoeba [177],
Trypanosoma [68], Ta e n i a [153], Plasmodium [70], and
Cryptosporidium [152], the animal parasites Theilera [178]
and Babesia [178,179], and even to the identification of
vector mosquitoes carrying Plasmodium [73]andDirofilaria
immitis [180] parasites. Most of these studies have brought to
light the many advantages of this method over the common
PCR technique.
Unlike a regular PCR reaction, LAMP is carried out at
a constant temperature (usually in the range of 60–65C).
This unique feature not only results in higher yields, but also
eliminates the need to buy a thermal cycler and shortens
the reaction time by eliminating time lost during thermal
changes. In addition, the reaction can be carried out without
extracting the DNA from the collected samples as shown in
the case of RIME, a nonautonomous retroelement found in
Trypanosoma brucei rhodesiense and T. b. gam bie nse [68]. In
35 minutes, using a simple water bath, RIME LAMP was able
to detect both T. b. gam bie nse and T. b. rh o de sie nse directly
from blood, serum, and CSF samples. More importantly, the
study has shown reproducibility in the field. In addition to
the above advantages, LAMP reactions are easy to set up,
and results can readily be assessed. The sample of interest
is mixed with primers, substrates, and a DNA polymerase
capable of strand displacement in a microcentrifuge tube.
During the reaction, large amounts of pyrophosphate ions
are produced, leading to the formation of a white precipitate
[181]. This turbidity is proportional with the amount of
DNA synthesized therefore one can assess the reaction by
real-time measurement of turbidity or more importantly,
simply through the naked-eye.
For all these reasons, the future adoption of LAMP as
a diagnostic tool for parasite infections in rural endemic
regions shows promise. Furthermore, as more groups apply
LAMP to the field of parasitology, we will see the appear-
ance of LAMP-modified assays that meet specific detection
needs. For example, in a recent study on bovine Babesia
[182], a multiplex-LAMP (mLAMP) assay was developed to
simultaneously detect B. bovis and B. bigemina from DNA
extracted from blood spotted on filter paper. Similarly, Han
et al. [71] implemented a LAMP assay based on the 18S rRNA
gene for the detection of the four human Plasmodium species
(falciparum,vivax,malariae,andovale). LAMP had a similar
sensitivity and a greater specificity than nested PCR, yielding
similar results but at a faster turnaround time. Their results
are consistent with other studies demonstrating the rapidity
and the improved specificity and sensitivity obtained using
the LAMP assay.
4.4. Luminex xMAP Technology. Luminex technology
is a bead-based flow-cytometric assay that allows
the detection of various targets simultaneously
(http://www.luminexcorp.com/). The microsphere beads
can be covalently bound to antigens, antibodies, or oligonu-
cleotides that will serve as probes in the assay. Up to 100
microspheres are available each emitting unique fluorescent
signals when excited by laser therefore allowing the identifi-
cation of dierent targets [183]. Adapted to the study of par-
asites, the Luminex assay could identify multiple organisms
or dierent genotypes of one particular organism during the
same reaction utilizing very low volume. The approach could
prove useful in the study of antigenic diversity and drug-
resistance alleles and for the diagnosis of parasitic diseases.
Luminex was applied to the study of Cryptosporidium
[154]. C.hominis and C. parvum cannot be distinguished
using antigen detection or serology assays. Only DNA-based
approaches have been successful in doing so by exploiting
the single nucleotide dierence in the microsatellite-2 region
(ML-2) of both species [154]. Ultimately DNA sequencing is
the diagnosis tool of choice but it is costly, labour-intensive
and time-consuming. In a recent study, Bandyopadhyay
et al. [154] successfully detected and distinguished C.
hominis and C. parvum in 143 DNA extracts using Luminex
technology by using oligonucleotide probes specific to the
ML-2 regions of each species. Turnaround time was about
5 hours making this assay not only much faster but also
less expensive than PCR followed by DNA sequencing. It
also proved to be 100% specific and more sensitive than a
direct fluorescent antibody (DFA) test, a method routinely
8 Interdisciplinary Perspectives on Infectious Diseases
used to identify Cryptosporidium and Giardia species. Note
that DFA cannot dierentiate between C. hominis and C.
parvum.
Similarly in other research, Luminex technology was
able to detect all-blood stage parasite levels of the four
human Plasmodium species (falciparum,vivax,malariae,and
ovale) simultaneously [75]. This study demonstrated that
Luminex technology can improve the speed, the accuracy,
and the reliability of other PCR methods. For example,
the need for gel electrophoresis to dierentiate the LDR
products representing the four human Plasmodium species
is eliminated. Second, all samples are handled simultaneously
and continuously through a 96-well plate format from DNA
extraction all through data analysis. The process is auto-
mated and therefore uniformity can be achieved. Finally, the
high-throughput capability of the Luminex system confers it
a clear advantage over the use of labour-intensive microscopy
for large scale studies.
4.5. Proteomics. Since proteins are the main catalysts,
structural elements, signalling messengers, and molecular
machines of biological tissues, proteomic studies are able
to provide substantial clinical relevance. Proteins can be
utilized as biomarkers for tissues, cell types, developmental
stages, and disease states as well as potential targets for
drug discovery and interventional approaches. The next
generation of diagnostic tests for infectious diseases will
emerge from proteomic studies of serum and other body
fluids. Recent advances in this area are attributable largely
to the introduction of mass spectrometry platforms capa-
ble of screening complex biological fluids for individual
protein and peptide “biomarkers.” Proteomic strategy can
identify proteins in two ways: bottom-up and top-down
approaches. In the former, the proteins in a biological fluid
are proteolytically shattered into small fragments that can be
easily sequenced and the resultant spectra are compared with
those in established peptide databases. This is the protein
equivalent of “shotgun” genomics. Bottom-up strategies
are dicult to quantitate and cannot identify modified
molecules (e.g., alternately spliced, glycosylated). Since each
open reading frame in the human genome is thought to
generate at least 10 modified proteins, this issue is a major
limitation.
The classic top-down strategy is 2-dimensional gel
electrophoresis. Top-down strategies seek to identify proteins
and peptides (and their natural variants) in complex biologi-
cal fluids. Two-dimensional (2D) gel electrophoresis was first
described in 1975. With this method, proteins are resolved in
the first dimension based on pH (a process called isoelectric
focusing) and in the second dimension by their molecular
weight. This technique is labor intensive, and low throughput
and requires large amounts of sample. Such limitations
have encouraged the search for improved approaches. Other
techniques used for the expression analysis of proteins are
matrix-assisted laser desorption ionization time-of-flight
mass spectrometry (MALDI-TOF MS), surface-enhanced
laser desorption ionization time of flight mass spectrom-
etry (SELDI-TOF MS), liquid chromatography combined
with MS (LC–MS–MS), isotope-coded anity tags (ICAT),
and isotope tags for relative and absolute quantification
(iTRAQ).
The development of automated, high-throughput pro-
teomic technologies such as MALDI-TOF and SELDI-TOF
MS has enabled large numbers of clinical samples to be
analyzed simultaneously in a short time. These platforms
have made “population-based proteomics” feasible for the
first time (reviewed in [184]). All proteomics-based diag-
nostic eorts seek to identify biomarkers that, alone or in
combination, can distinguish between “case” and “control”
groups.
The main limitation of SELDI compared to MALDI
resides in the fact that SELDI has lower resolution and lower
mass accuracy. In addition, SELDI is unsuitable for high
molecular weight proteins (>100 kDa) and is limited to the
detection of bound proteins on to the ProteinChip Array.
Most studies published about parasitic diseases have
focused on SELDI. The SELDI, a derivation of MALDI,
allows sample binding to chemically active ProteinChip sur-
faces. Several types of ProteinChip arrays are available with
diering abilities to bind proteins with dierent chemical
(anionic, cationic, hydrophobic, metallic, and normal phase)
or biological (antibody, enzymes, receptors) properties,
thereby allowing the direct analysis of proteins from complex
biological samples without the need for prior separation
by 2D gel electrophoresis. The output of the SELDI is a
spectrum of mass-to-charge ratios (m:z values) with their
corresponding relative intensities (approximating to relative
abundance).
SELDI analyses were initially applied to the discovery
of early diagnostic or prognostic biomarkers of cancer
(reviewed in [185]). Recently, this technique has been applied
to the study of serum biomarkers of infectious diseases
such as Severe Acute Respiratory Syndrome [186], African
trypanosomiasis [83], fascioliasis [157], cysticercosis [158],
and Chagas diseases (Ndao et al., submitted). Such studies
have focused on identifying a distinctive configuration of
circulating serum proteins that are indicative of a specific
pathophysiological state, a so-called “proteomic fingerprint.
The real potential of proteomic fingerprinting is in
its use as a discovery tool for novel biomarkers that can
then be incorporated into simple bedside diagnostics based
on aordable technologies such as immunologically based
antigen-detection tests that could be implemented in dipstick
or cassette formats.
Acknowledgments
The author would like to thank the Public Health Agency
of Canada and the National Microbiology Laboratory for
supporting the National Reference Centre for Parasitology.
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... Indirect IFA has been employed for quantitative serology of besnoitiosis, trypanosomosis, toxoplasmosis [20], and some tick-borne infectious diseases caused by Ehrlichia canis, Anaplasma spp., Babesia spp. [21,22]. IFAT was reported to detect Toxoplasma gondii and Neospora caninum specific IgG antibodies in dogs in Brazil [23]. ...
... CFT is one of the most commonly used serologic assays and can efficiently detect parasitic infections such as anaplasmosis, babesiosis, trypanosomosis, and toxoplasmosis [21,22]. ...
... Latex agglutination test (LAT): Latex agglutination occurs when a sample containing the specific antibody (or antigen) is mixed with an antigen (or antibody) coated on the surface of latex particles. LAT has been used for diagnosis of Toxoplasma gondii [21,22]. Card agglutination for trypanosomosis tests (CATT) was initially developed for the diagnosis of Trypanosoma gambiense infection in man, later, the test was established for diagnosis of T. evansi (Surratex based on trypanosome-antigen detection in blood or serum) infection in animals using latex beads coated with RoT at 1.2 protein of T. evansi [33]. ...
Chapter
Conventional as well as current diagnostic techniques for evaluation of parasitic load of dogs and cats are discussed.
... Enzyme-linked immunosorbent assay (ELISA) is an important serology-based assay with different types like the Falcon assay screening test, ELISA, and dot-ELISA. Other serology-based tests used for identification of parasites include the hemagglutination (HA) test, the complement fixation (CF) test, the indirect immunofluorescent antibody (IFA) test, the direct immunofluorescent antibody (DFA) test, the immunoblotting test, and quick diagnostic procedures [53]. ...
... With the advancement in diagnosis, traditional PCR is updated to nested PCR (improving sensitivity and specificity), multiplexed PCR (amplification of several different DNA sequences at the same time), and real-time PCR (quantification of the product after each cycle). Luminex-based assays and loop-mediated isothermal amplification are new emerging techniques for the identification of parasitic infections [53,56]. The sensitivity and specificity of nucleic acid-based techniques are much higher than those of existing diagnostic assays. ...
Chapter
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Small ruminants, especially goats, play an important role in the livestock economy of the world. Parasitism is one of the major problems of the goat population around the world and is responsible for production losses. To control such kinds of losses and improve production, a timely diagnosis of parasitic infection is crucial. The improvement and development of conventional and molecular diagnostic tests help a lot for the early detection of parasitic infections. Strategies to use different control measures like chemotherapy, phytotherapy, pasture management, use of bioactive crops, biological control measures, and development of vaccines also help to improve the health and production of goats.
... Broadly, serological-based detection can be divided into two main categories: (a) antigen-based detection and (b) antibody-based detection. There are various ways to carry out the serological tests, including rapid diagnostic tests, Complement fixation tests, haemagglutination test (HA) and indirect haemagglutination assay (IHA), direct or indirect immunofluorescence antibody (DFA, IFA) and immunoblotting (Ndao, 2009). ELISA is the most commonly used test because it has higher sensitivity and specificity compared to microscopy and under field conditions use of dipsticks is more common (Sousa-Figueiredo et al., 2013). ...
... The overall advantage of serological tests is that they are easier to interpret and are also less time consuming. However, the main disadvantage of serological assays is that they involve examination of infections that occurred in the past and sensitivity varies during the course of infection (Ndao, 2009;Ricciardi and Ndao, 2015). ...
... Wildlife parasitology studies rely on efficient and sensitive detection methods to diagnose infections (Ndao 2009). The first step in wildlife disease studies as well as epidemiology is, arguably, to determine parasite prevalence, i.e. the proportion of parasitised individuals in a population of hosts (Ishtiaq et al. 2017). ...
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Prevalence studies of avian haemosporidian parasites frequently use microscopy and the nested polymerase chain reaction (PCR) protocols for detecting infections. Newer PCR protocols to detect parasites are being developed, with the distinct advantage of reducing screening cost and time, as well as increasing efficiency and sensitivity. The detection ability of micros-copy and nested PCR was compared against a real-time PCR (qPCR) protocol using genomic DNA extracted from 240 bird blood samples collected from three starling species (Cape Starling, the Greater Blue-eared Starling, and the Wattled Starling; family Sturnidae) in the Kruger national park, South Africa. All three protocols successfully detected avian haemosporidian parasites with the qPCR having a considerable edge against the other two methods. Fifteen unique cytochrome b lineages were identified of which seven were new lineages. Microscopy and nested PCR recorded similar prevalence (32.92% and 35.42% respectively). The qPCR protocol used here, although more sensitive (52.92% prevalence), is not able to differentiate between parasite genera but provides the opportunity to screen a large number of samples in large-scale studies within a specific region. This study recommends the development and adoption of new molecular protocols with increased sensitivity and accuracy in prevalence studies. Nevertheless, microscopy remains essential for the morphological description of parasites and for distinguishing between abortive and successful chronic infections. The PCR-based method displays the detection of the parasitic genome but does not reveal whether parasites have or will develop into a successful infection.
... 77 ELISA and other forms of EIA are routinely and reliably used in the diagnosis of parasitic infections such as cysticercosis, filariasis, gnathostomiasis, hydatidosis, schistosomiasis, strongyloidiasis, toxocariasis, toxoplasmosis, and trichinellosis. 78 Crude antigen preparation of A. cantonensis has shown some crossreactivity with other parasitic antigens, 52 whereas tests using the 31-kDa glycoproteins of A. cantonensis have shown specificity and sensitivity of 100%. 51 Some studies hypothesize that native antigen may be more effective at detecting patent infection in certain non-endemic areas 49,52 ; others attribute the dearth of serological testing to the lack of availability of native antigen 51,55,79,80 or lack of availability of the test itself. ...
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Angiostrongylus cantonensis is the leading cause of neuroangiostrongyliasis worldwide, and east Hawaii Island is a hotspot for the disease in the United States. A combination of glycoproteins with molecular weight of 31 kDa has been used as antigen to evaluate antibody response in human serum samples in Thailand with high specificity and sensitivity. In a previous pilot study, the Thailand-isolated 31-kDa proteins showed efficacy in dot-blot tests using serum samples from 435 human volunteers on Hawaii Island. However, we hypothesized that native antigen isolated from Hawaii A. cantonensis may exhibit higher specificity than the Thailand-isolated 31-kDa antigen due to potential minor variation in epitopes between isolates. In this study, 31-kDa glycoproteins were isolated by sodium dodecyl-sulfate polyacrylamide gel electrophoresis from adult A. cantonensis nematodes collected from rats captured on east Hawaii Island. The resultant proteins were purified by electroelution, pooled, bioanalyzed, and quantified. A subset of 148 samples from human participants of the original cohort of 435 was consented for this study, including 12 of the original 15 clinically diagnosed participants. Results of ELISA using the Hawaii-isolated 31-kDa antigen were compared with results of the same serum samples previously tested with both crude Hawaii antigen ELISA and Thailand 31-kDa antigen dot blot. This study shows a seroprevalence in the general population of East Hawaii Island of 25.0%, similar to previous findings of 23.8% seroprevalence in this cohort using crude antigen from Hawaii A. cantonensis and 26.5% using Thailand 31-kDa antigen.
... Unfortunately, these methods can be highly cumbersome, expensive, and difficult to perform in resource-limited settings. Furthermore, some of these modes of detection struggle with distinguishing between past, latent, acute, and reactivated infections, making it difficult to implement proper treatment regimens [9,10]. As a result, the continued development and improvement of point-of-care (POC) diagnostic tools such as rapid diagnostic tests (RDTs) have demonstrated great potential in resource-limited settings and hold much promise in disease diagnostics, active surveillance, and treatment [11,12]. ...
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Centuries of scientific breakthroughs have brought us closer to understanding and managing the spread of parasitic diseases. Despite ongoing technological advancements in the detection, treatment, and control of parasitic illnesses, their effects on animal and human health remain a major concern worldwide. Aptamers are single-stranded oligonucleotides whose unique three-dimensional structures enable them to interact with high specificity and affinity to a wide range of targets. In recent decades, aptamers have emerged as attractive alternatives to antibodies as therapeutic and diagnostic agents. Due to their superior stability, reusability, and modifiability, aptamers have proven to be effective bioreceptors for the detection of toxins, contaminants, biomarkers, whole cells, pathogens, and others. As such, they have been integrated into a variety of electrochemical, fluorescence, and optical biosensors to effectively detect whole parasites and their proteins. This review offers a summary of the various types of parasite-specific aptamer-based biosensors, their general mechanisms and their performance.
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Consisting of diverse groups of organisms, parasites are among the least studied pathogens despite their enormous impacts on humans, livestock, and wildlife. In particular, little is known about their host specificity and diversity in wildlife. Here, using multiple primer pairs and sequencing 18S rRNA genes of diverse groups of parasites, we aimed to investigate fecal parasitomes of carnivorous wildlife in Korea, namely, the raccoon dog (Nyctereutes procyonoides), the leopard cat (Prionailurus bengalensis), and the Eurasian otter (Lutra lutra). A total of 5 host-specific parasite species were identified, including 2 from raccoon dogs, 2 from leopard cats, and 1 from Eurasian otters. In addition, numerous parasite species of their prey animals were detected in their feces. It was found that the parasitome composition varied between host animals, and it was thought that the difference was attributed to the difference in prey animals, as numerous small mammal parasites were detected from feces of leopard cats inhabiting inland areas and fish parasites from feces of Eurasian otters and raccoon dogs inhabiting waterside areas. Furthermore, 5 zoonotic parasites known to infect humans were identified at the species level. Wildlife-associated zoonoses are expected to increase as the proximity between humans and wildlife increases due to urbanization. Vigilance may be necessary, such as by monitoring parasites in wildlife feces, as was done in this study.
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Water-associated or water-related infectious disease outbreaks are caused by pathogens such as bacteria, viruses, and protozoa, which can be transmitted through contaminated water sources, poor sanitation practices, or insect vectors. Low- and middle-income countries bear the major burden of these infections due to inadequate hygiene and subpar laboratory facilities, making it challenging to monitor and detect infections in a timely manner. However, even developed countries are not immune to these diseases, as inadequate wastewater management and contaminated drinking water supplies can also contribute to disease outbreaks. Nucleic acid amplification tests have proven to be effective for early disease intervention and surveillance of both new and existing diseases. In recent years, paper-based diagnostic devices have made significant progress and become an essential tool in detecting and managing water-associated diseases. In this review, we highlight the importance of paper and its variants as a diagnostic tool and discuss the properties, design modifications, and various paper-based device formats developed and used for detecting water-associated pathogens.
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New diagnostic tests are needed to facilitate the diagnosis of Plasmodium falciparum malaria in the returned traveler. We performed a blinded evaluation of a nonisotopic colorimetric PCR-based assay (Digene SHARP Signal System) and compared the results with those obtained by microscopy and nested PCR for the detection of P. falciparum malaria in 150 febrile travelers. By using nested PCR as the reference standard, the colorimetric assay had a sensitivity of 100% and a specificity of 95.4% far the detection of P. falciparum, This PCR-based nonisotopic assay is a rapid, sensitive, and specific method for the detection of falciparum malaria in returned travelers.
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SummaryA pilot study was carried out on the detection of trypanosome-specific antibodies in saliva for diagnosis of sleeping sickness. All twenty-three saliva samples of parasitologically confirmed Trypanosoma brucei gambiense patients tested positive in an indirect enzyme-linked immunosorbent assay, whereas all 14 saliva samples of a negative control group remained negative. Trypanosome-specific antibody levels in patient saliva correlated with antibody levels in serum, but were about 250-fold lower. Eight of 23 undiluted saliva samples of sleeping sickness patients tested positive in CATT/T. b. gambiense and two of 23 in LATEX/T. b. gambiense. All fourteen saliva samples of the negative control group were also positive in CATT/T. b. gambiense, as were four of 14 in LATEX/T. b. gambiense. CATT and LATEX were thus inappropriate for antibody detection in saliva. These results indicate that trypanosome-specific antibody detection in saliva is possible. This could lead to the development of a simple, non-invasive, reliable saliva field test for diagnosis of sleeping sickness.
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