Abstract:

Objective To investigate the population density of domestic dogs, the prevalence of Leishmania infection in domestic dogs, and the density of sandfy in the visceral leishmaniasis (VL) endemic areas in Shanxi Province. Methods The investigation was carried out in 2 to 6 villages randomly selected from suburbs of Yangquan City, Wuxiang County of Changzhi City, and Xiangning County of Linfen City in Shanxi Province from 2021 to 2022. The domestic dog population density was obtained through household survey in the survey areas. The sample size of domestic dogs was estimated based on the previous survey results. Venous blood sampls were collected from the selected dogs and their detailed information were recorded. The canine rk39 immunochromatographic test strip was used to detect serum anti-Leishmania antibodies in the sampled dogs. From each of 3 survey areas (county), 2 natural villages were selected, which had local case reports or no case reports over the last five years. The sandfy density was investigated by light trap method in 2 farmer's households and livestock barns, respectively, selected from each village. For calculation of mean sandfy density, the survey was conducted once at early and latter part of every month during May to September yearly. The VL case report data from Shanxi endemic areas were collected through the Population-based Healthcare System. Statistical analysis was performed using SPSS 25.0, and the chi-square test was used to compare the positive rate of anti-Leishmania antibody in domestic dogs in different years in 3 survey areas (counties). Results The average domestic dogs density in the 3 survey areas (counties) in Shanxi Province from 2021 to 2022 was 0.09 dogs per household. The mean domestic dog density in the outer suburbs of Yangquan City, Wuxiang County of Changzhi City and Xiangning County of Linfen City were 0.07, 0.16, and 0.13 dogs per household, respectively. A total of 1 149 blood samples were collected, of which 73 were positive for anti-Leishmania antibodies, resulting in a positivity rate of 6.4% (73/1 149). The positivity rate of anti-Leishmania antibodies in male dogs was 7.6% (41/542), and in female dogs the positivity rate was 5.1% (31/607), with no significant difference in the positivity rate of anti-Leishmania antibodies between sexes (χ² = 2.94, P > 0.05). Among the 1 093 dogs whose age was known, 75.6% (826/1 093) were aged four or younger. The positivity rate of anti-Leishmania antibodies in dogs aged five years was the highest (8.2%, 7/85), and there was no significant difference in the positivity rate of anti-Leishmania antibodies among different age groups (P > 0.05). A total of 25 537 sandflies were captured, of which 23 012 were females (accounting for 90.1%), and 2 525 were males (accounting for 9.9%). The mean density of sandflies was 26.1 flies per lamp-night, and the mean density of sandflies in the outer suburbs of Yangquan City, Wuxiang County of Changzhi City and Xiangning County of Linfen City were 3.9, 36.6 and 45.9 flies per lamp-night, respectively. A total of 57 cases of visceral leishmaniasis were reported in 3 districts (counties) of Shanxi Province from 2021 to 2022, with 45, 3 and 9 cases reported from the outer suburbs of Yangquan City, Wuxiang County of Changzhi City and Xiangning County of Linfen City, respectively. Conclusion In three survey areas (county) of Shanxi Province, the sandfly density and the infection rate of Leishmania in domestic dogs are relatively high.

Key words: Visceral leishimaniasis, Canine density, Sandfly density, Canine infection rate