Leishmaniasis dipstick
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Accurate and rapid diagnosis of leishmaniasis is of great importance, i.e. to start early treatment and to prevent transmission, but remains problematic. Clinical diagnosis is difficult due to variable disease symptoms. Parasitological diagnosis relies on microscopical demonstration or culturing of Leishmania parasites from aspirates, but sample retrieval is painful and the microscopic identification in smears and biopsy sections requires experienced personnel and the isolation of parasites by culturing is time-consuming, difficult and expensive. As diagnostic procedures have often to be employed under harsh field conditions, serological tests should, besides having a very good sensitivity and specificity as all diagnostics tests, meet specific requirements like not requiring advanced equipment, electricity or a cold chain.
At present the direct agglutination tests (DAT and FAST) and the commercially available rK39 dipstick test are partly meeting these requirements, but may either be time consuming (DAT) or there is concern about the sensitivity/specificity of the test (rK39). Therefore, there is still a need for the development of diagnostic test for VL that is suitable for use in peripheral health services (simplicity), has a high sensitivity/specificity and is affordable.
Approach
KIT Biomedical Research aims at the development, and subsequent evaluation of simple robust diagnostic tests for the diagnosis of visceral leishmaniasis in humans and canine leishmaniosis in VL endemic countries. The work will pursue two test formats: (1) a latex agglutination test and (2) lateral flow test. These two test formats will be developed, because:
- The technological expertise to perform these types of tests is minimal
- Specialized laboratory equipment to perform the tests is not required
- A large number of samples can be processed quickly with minimum effort
- The result of testing will be available almost immediately
- A lateral flow or latex agglutination test may ultimately prove more cost-effective than currently used diagnostics, in particular, when used in mass-screening surveys
Recently KIT Biomedical Research has completed the development of a prototype dipstick test that can be used for the diagnosis of canine leishmaniosis. This prototype currently undergoes field evaluation in Portugal and Turkey and will serve as a model for the further development of human tests. Recently, a grant of WHO/TDR was obtained for further work on test development.
Focal points
- Development of simple diagnostic tests (lateral flow format or latex agglutination test) for the sero-diagnosis of leishmaniasis.
- Evaluation of developed tests in disease endemic countries
- Implementation studies
Example
A dipstick assay, based on Leishmania infantum antigen, for the rapid detection of Leishmania specific antibodies in canine serum samples was developed and evaluated. After determining optimal dipstick test conditions, test performance was compared with two existing serological tests, i.e. the direct agglutination test (DAT) and fast agglutination screening test (FAST). The work was carried out in close collaboration with scientists of Departamento de Ciências Veterinárias, Universidade de Trás-os-Montes e Alto Douro (Vila Real, Portugal).
The study demonstrated that the dipstick had a sensitivity of 99.2% and a specificity of 87.9%. DAT had a sensitivity of 97.7% and a specificity of 95.2%, whereas FAST had also a sensitivity of 97.7% and a specificity of 93.0%. Although the dipstick test is based on antigen of L. infantum (the causative agent of CanL in the Mediterranean region), it is also able to detect antibodies in serum samples of dogs infected with L. chagasi (Brazil). This enables the use of the dipstick in all major endemic regions of CanL. Furthermore, it also detected anti-Leishmania antibodies in import cases of CanL allowing the use of the dipstick in veterinary clinics in non-endemic countries. The high sensitivity and ease of performance make the dipstick test very suitable for surveillance surveys.
Projects
Publications
- Schallig, H.D. - Evaluation of the direct agglutination test and the rK39 dipstick test for the sero-diagnosis of visceral leishmaniasis.
- Schallig, H.D. - Development of a Dipstick Assay for Detection of Leishmania-Specific Canine Antibodies.