Abstract:

Objective To understand the current endemic status of visceral leishmaniasis in Hancheng City and provide basis for the establishment of endemic surveillance and control measures. Methods The endemic information and survey reports of visceral leishmaniasis in Hancheng City in 2017 were collected from the Disease Surveillance Reporting System of the Chinese Center for Disease Control and Prevention. Blood was collected from the patients. Six villages that have reported cases since 2012 were selected as the survey spots, including the Chengjiadong Village, Yangwan Village, and Shuicaota Village in Sangshuping Town, Caojiashan Village in Xizhuang Town, Dongjia Village in Zancun Town, and Xiyuan Village in Longmen Town. The former four villages located in the hilly regions while the latter two in the Loess plateau area. Based on the family information on disease incidence, anticoagulation and normal blood samples (3 ml each) were collected randomly from residents and domestic dogs. Bone marrow was collected from suspected dogs. Dogs with positive serological results were sacrificed to collect bone marrow swab. The sandfly density was monitored manually from middle June to late September. The rK39 immunochromatographic test strip and ELISA kit were used to detect the antibody for Leishmania in human serum and dog serum, respectively. The positive samples were further confirmed by rK39 immunochromatographic test strip. The dog bone marrow underwent pathological testing. DNA was extracted from blood, bone marrow and sandfly specimens. PCR was performed for kinetoplast target gene of Leishmania spp. The positive samples were further used for amplification of internal transcribed spacer 1（ITS-1） sequence, small subunit ribosomal RNA（SSU rRNA） and DNA repeats, and cluster analysis was made to identify the species. Result A total of 10 cases of visceral leishmaniasis in Hancheng City were reported in 2017, of whom 8 were workers from other cities and 2 were indigenous kids. The positive rate of visceral leishmaniasis among residents was 3.1% （7/224）. No positive results of PCR were found in the asymptomatic residents. The positive rate of visceral leishmaniasis in dogs was 34.3% (115/335), which was higher in hilly mountain area （51.5%, 105/204） than that in plain area（7.6%, 10/131）（χ² = 68.000, P < 0.05）. The average sandfly density from June to September was 16.7/man hour, with a peak of 122/man hour. The average sandfly density in the hilly area was 23.6/man hour, significantly higher than 0.3/man hour in plateau area (t = 2.19, P < 0.05). A total of 366 sandflies were captured, including 168 males and 168 females, and 228 were identified, of which 29.4% (67/228) were Phlebotomus chinensis. The positive rate of Leishmania in sandflies was 1.5% as revealed by PCR. Leishmania was isolated from the bone marrow samples from 1 dog and 2 patients, and identified as Leishmania infantum by ITS-PCR, SSU rRNA-PCR and reiterated DNA sequence. Conclusion Leishmania infection is present among residents, dogs and sandflies in Hancheng City. The infection rate in hilly areas is higher than that in the plain areas.

Key words: Visceral leishmaniasis, Epidemiologic investigation, Leishmania infantum, Shaanxi