Cutaneous Leishmaniasis due to Three Leishmania Species Among Syrian Refugees in Sanliurfa, Southeastern Turkey

Development of a novel immunoFET technology-based POC assay for detection of Leishmania donovani and Leishmania major

Leishmaniasis is considered as one of the 20 neglected tropical diseases. Current methods of leishmanial diagnosis depend on conventional laboratory-based techniques, which are time-consuming, costly and require special equipment and trained personnel. In this context, we aimed to provide an immuno field effect transistors (ImmunoFET) biosensor that matches the conventional standards for point-of-care (POC) monitoring and detection of Leishmania (L.) donovani/Leishmania major. Crude antigens prepared by repeated freeze thawing of L. donovani/L. major stationary phase promastigotes were used for ELISA and ImmunoFETs. Lesishmania-specific antigens were serially diluted in 1× PBS from a concentration of 10⁶ -10² parasites/mL. A specific polyclonal antibody-based sandwich ELISA was established for the detection of Leishmania antigens. An immunoFET technology-based POC novel assay was constructed for the detection of Leishmania antigens. Interactions between antigen-antibody at the gate surface generate an electrical signal that can be measured by semiconductor field-effect principles. Sensitivity was considered and measured as the change in current divided by the initial current. The final L. donovani/L. major crude antigen protein concentrations were measured as 1.50 mg/mL. Sandwich ELISA against the Leishmania 40S ribosomal protein detected Leishmania antigens could detect as few as 100 L. donovani/L. major parasites. An immunoFET biosensor was constructed based on the optimization of aluminium gallium nitride/gallium nitride (AlGaN/GaN) surface oxidation methods. The device surface was composed by an AlGaN/GaN wafer with a 23 nm AlGaN barrier layer, a 2 μm GaN layer on the silicon carbide (SiC) substrate for Leishmania binding, and coated with a specific antibody against the Leishmania 40S ribosomal protein, which was successfully detected at concentrations from 10⁶ to 10² parasites/mL in 1× PBS. At the concentration of 10⁴ parasites, the immunoFETs device sensitivities were 13% and 0.052% in the sub-threshold regime and the saturation regime, respectively. Leishmania parasites were successfully detected by the ImmunoFET biosensor at a diluted concentration as low as 150 ng/mL. In this study, the developed ImmunoFET biosensor performed well. ImmunoFET biosensors can be used as an alternative diagnostic method to ELISA. Increasing the sensitivity and optimization of immuno-FET biosensors might allow earlier and faster detection of leishmaniasis.

The current epidemiology of leishmaniasis in Turkey, Azerbaijan and Georgia and implications for disease emergence in European countries

Leishmania spp. are sand fly-borne protozoan parasites causing leishmaniasis in humans and animals. The aim of the study was to analyse the epidemiology of leishmaniasis in Turkey, Azerbaijan and Georgia from 2005 to 2020 and evaluate the associated risk for disease emergence in European countries. It is based on an analysis of WHO and OIE reported cases between 2005 and 2020, a review of scientific articles published in SCOPUS between 2009 and 2020 and a questionnaire survey to public health and veterinary authorities in these countries. Endemic Leishmania spp. include L. infantum in the three countries, L. major in Azerbaijan and Turkey and L. tropica and L. donovani in Turkey. Leishmaniasis is reported in humans, animals and sand flies and incidence is spatially and temporarily variable. In the southern Caucasus and particularly in Georgia, reported incidence of human visceral leishmaniasis by L. infantum remains high. However, whilst Georgia experienced a gradual decrease from >4.0 cases per 100,000 population in 2005-09 to 1.13 cases per 100,000 population in 2020, the period with highest incidence in Azerbaijan, which ranged between 0.40 and 0.61 cases per 100,000 population, was 2016-2019, and no cases have so far been reported for 2020. Visceral leishmaniasis in the Southern Caucasus affects mostly young children from deprived urban areas and its closely associated to canine leishmaniasis. Turkey reported cases of visceral leishmaniasis between 2005 and 2012 and in 2016 only, and incidence ranged between 0.02 and 0.05 per 100,000 population. In contrast, the reported annual incidence of cutaneous leishmaniasis in Turkey was much greater and peaked at 7.02 cases per 100,000 population in 2013, associated to imported cases from cutaneous leishmaniasis endemic Syria. Leishmaniasis by L. infantum in Azerbaijan and Georgia represents a regional public and animal health challenge that requires support to improve diagnosis, treatment and control. The unprecedented rise of cutaneous leishmaniasis and the spread of L. tropica and L. donovani in Turkey is an important risk factor for their emergence in Europe, especially in Mediterranean countries where competent vectors are widespread.