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TESTS/DETECTION
Traditional and Molecular Detection/Tests available
INTRODUCTION
Approx. 60,000 species have been identified. But identification does not mean that we know everything about them. And we believe that there are many thousands more…
Only very few parasites can be seen with the naked eye. Most of them are to be found in the group of the
MACROPARASITES... which are large and do not multiply in or on the host (Examples: tape worms, nematods, arthopods such as fleas, ticks, etc.)
MICROPARASITES ...which are small and multiply within the host (like the malaria parasites.)
HYPERPARASITES … are parasites that live in parasites
Why do we need parasite research and parasite identification?
1… to find new treatments an future vaccines
2… for epidemiology studies
3… for control measures
4… for fundamental research
PARASITE-INFECTIONS/INFESTATIONS ARE ON THE RISE…
Problems in the developing world:
Increasing population
Poor – nutrition, hygiene, water supply, treatment access, hospital access, lab equipment
Proliferation of old diseases
Emergence of new diseases in severe forms
Problems in the developed world:
Increasing population
High costs for chemotherapy
Multiple drug resistance
New pathogens emerging and evolving rapidly
Not enough research money available
 Picture: Triatomine bug, a Trypanosoma cruzi vector, defecating on the wound after taking a blood meal. Trypanosoma cruzi causes CHAGAS, the South/Central American Trypanosomiasis. (Image Library CDC, Center for Disease Control And Prevention, Atlanta)
DETECTION/TESTS
A)
Traditional detection (microscopy)
B)
Molecular detection
A)
Traditionally the diagnosis is dependent on finding the parasite, but new methods - which are being developed all the time - are looking into parasite-proteins/antibodies or go even into the molecular “zones”.
O & P Stool Analysis. The ova and parasite stool analysis can only detect those that live in the intestines and whose eggs are passed through faeces.
FRESH stool samples are essential! Many labs offer analysis where the patient/doctor has to send the stool-sample by mail, which reduces the detection rate dramatically, because the eggs and parasites may break down in unpreserved stool.
One common question: Are these parasitic worms I see in my own stool? Answer: In over 95% of all cases it is undigested food fibre. Only under the microscope can one see the characteristic structure of a worm (like digestive organs).
The problems with traditional diagnosis:
- Some parasites are hidden in the host tissue
- There is a low sensitivity
- Some parasites are morphologically indistinguishable
B)
There are three methods of molecular detection:
1)
Biochemical
This test is looking for enzyme patterns. Advantages: the technique is simple; a large number of typing enzymes is available, morphologically similar enzymes can be distinguished. Disadvantages: tissue is needed for analysis (very often from liver and spleen); the detection technique is slow and can take days; higher risk of incorrect diagnosis.
2)
Immunological (antibodies)
These tests rely on the identification of a specific antibody. Advantages: rapid tests; individual and mass population screening is possible (pandemics); Disadvantages: The test cannot distinguish between past and present infections; it cannot distinguish between similar morphologies of parasites; One classical test is the Enzyme-linked immunosorbant assay.
In future, non-invasive antibody tests might be available (saliva, excreta).
3)
DNA based molecular diagnosis
The PCR (Polymerase Chain Reaction) amplifies target sequences and increases sensitivity. Advantages: It is highly specific for single species of parasites. The tests have clear results, because parasites and hosts have unique DNA. The probes can be designed with flexibility – a) specific to identify a single parasite species and b) less specific to detect a group of parasites. Disadvantages: the DNA probe does not distinguish between a dead and a living parasite.
Our lab analyses skin-scratch, urine, stool and sputum samples as well as vaginal and rectal swabs. We use diagnostic microbiology and immunology tools like the PCR (polymerase chain reaction), which is widely used in biology research. A typical PCR procedure is designed to amplify DNA about 1 billion-fold. This allows the visualization of a single DNA molecule obtained from a single fungus or bacteria or parasite cell. PCR is also extremely useful for identifying viral and intracellular infections.
Tests are done through:
MSML - Microbiologial and
Special Medical Tests
Office address: Integrated Medicine Centre
121 Crawford Street
London W1U 6BE
to go to the MSML-Laboratories.com website CLICK HERE
Prices depend on which tests are necessary. General tests can be very inaccurate (and test only for limited types of parasites, bacteria, viruses, fungi).
Therefore an initial consultation is crucial.
Microfilaria of Wuchereria bancrofti, from a patient seen in Haiti. Thick blood smears stained with hematoxylin. The microfilaria is sheathed, its body is gently curved, and the tail is tapered to a point. The nuclear column (the cells that constitute the body of the microfilaria) is loosely packed, the cells can be visualized individually and do not extend to the tip of the tail. The sheath is slightly stained with hematoxylin. (Image Library CDC, Center for Disease Control And Prevention, Atlanta) |
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