The Need for New Diagnostic Devices for Schistosomiasis, Malaria, and Hookworm :Implementation and Future Perspectives

Ayola Akim ADEGNIKASymposium of 13.01.2021

Malaria, hookworm and Schistosomiasis

Exposed• 41% world• 93% AfricaCases• 228 Mio World• 213 Mio AfricaDeath• 405000 World• 380000 Africa

Exposed• 700 MioCases• 240 MioMorbidity• FGS• MGS• Anemia• Cancer

Exposed• > 2 BioCases• >1.5 MioMorbidity• Anemia• MalnutritionDeath• 135000

Rationale• Affecting poorests • Limited ressources• Lack of education• Remotes areas• Critical health facilities>>> Need for effective control programme including:• Test• Treatment Determination of the prevalence and incidence • Prevention Effective, accessible and reliable diagnostic tools

Malaria diagnosis

MicroscopyGold standard method

Advantages • Cheap and easily deployable in the field

• Can be used to assess the efficacy of treatmentDisadvantages

P. falciparum trophozoites stages in Giemsa-stained thin blood films

Thick smear for quantitative diagnosis: parasite densities

P. falciparum trophozoites stages in Giemsa-stained thick blood films

Thin smear for qualitative diagnosis: species & stage identification

Disadvantages• Labour intensive • Time consuming : at least 60 min from specimen

collection to result • Need for well trained microscopists

Advantages• Simple to perform and to interpret• Fast: 15 -20 min from specimen collection to

result • Easily deployable in the field as kits can be

stored at ambient temperature• Relatively cheap

•

Disadvantages • Increasing reports of mutation in pHRP-2 leading to

false negatives• No quantification of parasites • Possibility of false positives due to the circulation of

pHRP-2 even after parasites clearance

Rapid Diagnostics Tests (RDTs)

• Based on detection of Histidine-rich protein II ( HRP-II)

• Plasmodium lactate dehydrogenase (pLDH) and Aldolase

Molecular diagnosis

Advantages • Highly sensitive and specific

• Reliably identify Plasmodium species especially in cases of co-infections

• High throughput

• Can be used to follow up treatment efficacy and detect drug resistant parasites

Disadvantages• Need for expensive equipment and skilled

personnel • Not easily deployable on the field • Time consuming: approx. 2 hours from

specimen collection to result

Advantages • Based on the detection of hemozoin • Sensitivity of 49-98% and specificity

of 82-97% (Tangpukdee et al, 2009)

Disadvantages • Labor intensive and need for

skilled personnel• Costly

Flow cytometry

Hookworm diagnosis

MicroscopyGold standard technique

Stool

Direct microscopy examination

MIF technique

Kato-katz technique

Coproculture & Harada Mori

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• Eggs

• Larvae

• Adult worm

• Species identification (very difficult)

Advantages

• Sensitive compared to direct examination;

• Rapid and cost effective

• Feasibility in areas with minimal infrastructure ;

• Quantitative => can be used in control programs

Kato Katz it the Gold standard “WHO”

Disadvantages

• Sensitivity especially for light infection.

• Requires fresh samples and competent readers

• Easy to detect hookworm eggs within 1 hour after

preparation

Advantage• They promote egg hatch and larval development

on medium liquid within in 7 days (Coproculture)

and 10 days (Harada Mori).

• Cost effective in resource limited settings; semi-

quantitative => can be used in control programs

Copro-culture & Harada Mori, McMaster Technique

Hookworm larvae

Disadvantages

• To detect larvae of Hookworm requires the use of fresh

stool sample (<= 2hrs old stool)

• Not suitable for refrigerated samples

• Time consumable

Molecular diagnostics

• Depending on the target interest and available resources the choice of the PCR can vary from a simple semi-quantitative to

quantitative real-time PCR.

Advantages• Increased sensitivity and specificity,

• Identify Species and strain of parasites,

• Molecular epidemiology to monitor the transmission

patterns

• Research oriented

Disadvantages

• Requires well equipped laboratory

infrastructure and well-trained personnel

• More expensive compared to the Kato-Katz

technique

• Contamination can lead to the false positive

Loop-mediated isothermal amplification (LAMP)

Diagnostics of Schistosomiasis

• Microscopy

• Gold standard technique to identify the eggs of S.haematobium and S.manoni.• Urine Filtration (S.haematobium) • Kato Katz (S.mansoni)

Direct examinations

• Advantages: quick, easy• Disadvantages: low sensitivities, sensitivitiesincreased with a multiple sampling

• Advantages: simples

• Disadvantages: low sensitivities, even

distribution of parasites in the stool

Indirect examinationsTechniques Advantages Disadvantages

Oliver Gonzales reaction or Circumova precipitation sensitive, species-specific need to obtain eggs by rearing or filtering

urine from a bilharzian

Pericercarian detachment sensitive, specific maintenance of strains in the laboratoryIndirect immunofluorescence sensitive, specific maintenance of strains in the laboratory

ELISA sensitive, specific egg antigensIndirect haemagglutination simple, sensitive lack of specificityElectrosyneresis, Immune

electrophoresis qualitative, analytique requires a lot of antigens. Specialised laboratories

Radio Immuno Assay (RIA), Radio Allergo Sorbent Test (RAST) Specific, sensitive Radioactive products. Little used

CCA RDT, specific sensitive to S. mansoni, time consumableCAA Specific, sensitive Non species-specific, time consumable

PCR Specific, sensitive High equipment costs, specialisedlaboratories

Perspectives: Mobile optical devices

• These devices have been shown as a proof of concept, for diagnosis of helminthic infections.• These innovative diagnostic devices are comparatively inexpensive,

sensitive, portable, simple to perform with options to store and share health care data making it suitable for survey of MDA programs• For malaria there is a strong interest to a non-invasive saliva based

diagnostic, detecting malaria parasite antigens

Conclusion and futures for endemic areas

• More reliable and simple diagnostic techniques are required• The smart phone devices, are more and more adapted (sensitivity and

specificity?)• Power less devices, are desirables in a limited setting areas in

endemic areas• RDT are limited in term of sensitivities and specificities and hence

required confrrmation with the gold standard technique• Non invasive techichiques using saliva will be preferable,• Affordable tests for all socio-economic status levels.

Thank you …..