Prevalence and associated risk factors of Leishmania infection among immunocompetent hosts, a community-based study in Chiang Rai, Thailand
Authors: Sriwongpan Pamornsri , Nedsuwan Supalert , Manomat Jidapa , Charoensakulchai Sakarn , Lacharojana Kittiphat , Sankwan Jamnong , Kobpungton Natheeporn , Sriwongpun Taweesak , Leelayoova Saovanee , Mungthin Mathirut , Siripattanapipong Suradej , Ruang-areerate Toon , Naaglor Tawee , Eamchotchawalit Theethach , Piyaraj Phunlerd 
Published: July 2021

BackgroundLeishmaniasisis an emerging infectious disease reported in the north and south of Thailand of which patients with HIV/AIDS are a high risk group for acquiring the infection. A lack of information regarding prevalence, and the risk association ofLeishmaniainfection among asymptomatic immunocompetent hosts needs further investigation. Information on potential vectors and animal reservoirs in the affected areas is also important to control disease transmission.MethodsAn outbreak investigation and a cross-sectional study were conducted following one index case of cutaneous leishmaniasis (CL) caused byL.martiniquensisin an immunocompetent male patient reported in August 2015, Chiang Rai Province, Thailand. From September to November 2015, a total of 392 participants at two study areas who were related to the index case, 130 students at a semi-boarding vocational school and 262 hill tribe villagers in the patient’s hometown, were recruited in this study. The nested internal transcribed spacer 1-PCR (ITS1-PCR) was performed to detectLeishmaniaDNA in buffy coat, and nucleotide sequencing was used to identify species. Antibody screening in plasma was performed using the Direct Agglutination Test (DAT), and associated risk factors were analyzed using a standardized questionnaire. Captured sandflies within the study areas were identified and detected forLeishmaniaDNA using nested ITS1-PCR. Moreover, the animal reservoirs in the study areas were also explored forLeishmaniainfection.ResultsOf 392 participants, 28 (7.1%) were positive forLeishmaniainfection of which 1 (4.8%) wasL.martiniquensis, 12 (57.1%) wereL.orientalisand 8 (38.1%) wereLeishmaniaspp. Of 28, 15 (53.6%) were DAT positive. None showed any symptoms of CL or visceral leishmaniasis. Risk factors were associated with being female (adjusted odds ratio, AOR 2.52, 95%CI 1.01–6.26), increasing age (AOR 1.05, 95%CI 1.02–1.08), having an animal enclosure in a housing area (AOR 3.04, 95%CI 1.13–8.22), being exposed to termite mounds (AOR 3.74, 95%CI 1.11–12.58) and having domestic animals in a housing area (AOR 7.11, 95%CI 2.08–24.37). At the semi-boarding vocational school, sixSergentomyia gemmeasamples were PCR positive for DNA ofL.orientalisand oneS.gemmeawas PCR positive for DNA ofL.donovani/L.infantum. Additionally, onePhlebotomus stantoniwas PCR positive for DNA ofL.martiniquensis, and one black rat (Rattus rattus) was PCR positive for DNA ofL.martiniquensis.ConclusionThis information could be useful for monitoringLeishmaniainfection among immunocompetent hosts in affected areas and also setting up strategies for prevention and control. A follow-up study of asymptomatic individuals with seropositive results as well as those with positive PCR results is recommended.