Genetic variation and geographic distribution of Leishmania orientalis and Leishmania martiniquensis among Leishmania/HIV co-infection in Thailand

Abstract Since 1999, the number of asymptomatic leishmaniasis cases has increased continuously in Thailand, particularly among patients with HIV who are prone to develop symptoms of cutaneous and visceral leishmaniasis further. The asymptomatic infection could play a key role in Leishmania transmission and distribution. Understanding population structure and phylogeographic patterns could be crucially needed to develop effective diagnoses and appropriate guidelines for therapy. In this study, genetic variation and geographic distribution of the Leishmania/HIV co-infected population were investigated in endemic northern and southern Thailand. Interestingly, Leishmania orientalis was common and predominant in these two regions with common regional haplotype distribution but not for the others. Recent population expansion was estimated, probably due to the movement and migration of asymptomatic individuals; therefore, the transmission and prevalence of Leishmania infection could be underestimated. These findings of imbalanced population structure and phylogeographic distribution patterns provide valuable, insightful population structure and geographic distribution of Leishmania/HIV co-infection to empower prevention and control of transmission and expansion of asymptomatic leishmaniasis

Prevalence and risk factors associated with <i>Leishmania</i> infection in Trang Province, southern Thailand

<div><p>Background</p><p>Autochthonous cutaneous and visceral leishmaniasis (VL) caused by <i>Leishmania martiniquensis</i> and <i>Leishmania siamensis</i> have been considered emerging infectious diseases in Thailand. The disease burden is significantly underestimated, especially the prevalence of <i>Leishmania</i> infection among HIV-positive patients.</p><p>Methods</p><p>A cross-sectional study was conducted to determine the prevalence and risk factors associated with <i>Leishmania</i> infection among patients with HIV/AIDS living in Trang province, southern Thailand, between 2015 and 2016. Antibodies against <i>Leishmania</i> infection were assayed using the direct agglutination test (DAT). DNA of <i>Leishmania</i> was detected by ITS1-PCR using the buffy coat. Species of <i>Leishmania</i> were also identified.</p><p>Results</p><p>Of 724 participants, the prevalence of <i>Leishmania</i> infection was 25.1% (182/724) using either DAT or PCR assays. Seroprevalence of <i>Leishmania</i> infection was 18.5% (134/724), while <i>Leishmania</i> DNA detected by the PCR method was 8.4% (61/724). Of these, 24.9% (180/724) were asymptomatic, whereas 0.3% (2/724) were symptomatic VL and VL/CL (cutaneous leishmaniasis). At least five species were identified: <i>L. siamensis</i>, <i>L</i>. <i>martiniquensis</i>, <i>L</i>. <i>donovani</i> complex, <i>L</i>. <i>lainsoni</i>, and <i>L</i>. <i>major</i>. Multivariate analysis showed that CD4⁺ levels <500 cells/μL and living in stilt houses were independently associated with <i>Leishmania</i> infection. Those who were PCR positive for <i>Leishmania</i> DNA were significantly associated with a detectable viral load, whereas non-injection drug use (NIDU) and CD4⁺ levels <500 cells/μL were potential risk factors of <i>Leishmania</i> seropositivity.</p><p>Conclusions</p><p>A magnitude of the prevalence of underreporting <i>Leishmania</i> infection among Thai patients with HIV was revealed in this study. Effective public health policy to prevent and control disease transmission is urgently needed.</p></div

Number of <i>Leishmania</i> infections by DAT analysis with titers of ≥100 or by PCR assay (n = 724).

<p>Number of <i>Leishmania</i> infections by DAT analysis with titers of ≥100 or by PCR assay (n = 724).</p

Patients who were either seropositive by DAT analysis with titers of ≥100 or positive by PCR assay among 10 districts of Trang province.

<p>Patients who were either seropositive by DAT analysis with titers of ≥100 or positive by PCR assay among 10 districts of Trang province.</p

The unrooted phylogenetic tree inferred from the ITS1 sequences using the NJ method.

<p>The bootstrapping values < 50 are omitted. Dense lines indicate <i>Leishmania</i> species complexes.</p

Numbers of positive DAT analysis together with numbers of positive PCR results at the titers of 1:100 to 1:6400.

<p>Numbers of positive DAT analysis together with numbers of positive PCR results at the titers of 1:100 to 1:6400.</p