Evaluation of isothermal molecular proves to identify Leishmania infantum chagasi infection in dogs and sand flies

• Grant number: 21/08912-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: January 01, 2022
• End date: June 30, 2024
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Preventive Veterinary Medicine
• Principal Investigator: Rodrigo Martins Soares
• Grantee: Geovanna Vioti
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

A relevant problem for the control of Visceral Leishmaniasis (VL) is the lack of laboratory tests with good accuracy to diagnose the infection, particularly in dogs. Dogs are the main reservoir and source of infection of the causing agent of VL in urban areas in Brazil, Leishmania infantum chagasi. Therefore, VL control in urban areas is based on actions taken on these hosts. To identify infected dogs, serological methods are the most used, due to their low cost and ease of execution. However, these tests have insufficient diagnostic sensitivity and do not necessarily detect animals that are transmitting the agent. Thus, tests based on direct detection of the agent have been widely indicated and, among them, molecular tests which are capable of detecting the parasite's DNA, stand out. PCR and its variations are tests of high sensitivity and could have enormous applicability to be used in official VL control programs, were it not for its high cost. PCR has a high cost due to input prices and the complexity of the laboratory facilities it requires. For this reason, the project we are proposing aims to evaluate and standardize molecular tests for the diagnosis of VL in dogs based on isothermal amplification of the parasite's DNA. Unlike PCR and its variations, isothermal DNA amplification methods require much cheaper laboratory inputs, in addition to requiring much less sophisticated equipment, which is why they are more suitable for use in official disease control programs, when large amounts of samples are analysed in a short period. In this project, samples of naturally infected dogs and sand fly vectors experimentally contaminated with L. infantum chagasi will be tested by two isothermal tests, LAMP (Loop mediated isothermal amplification) and PSR (Polymerase spiral reaction). The analytical and diagnostic performance of the isothermal tests will be estimated by comparing their results in samples tested by other methods of detection of infection by L. infantum chagasi, such as serological tests, conventional PCR and parasitological tests.