Visceral Leishmaniasis in China: an Endemic Disease under Control

Abstract

Visceral leishmaniasis (VL) caused by Leishmania spp. is an important vector-borne and largely zoonotic disease. In China, three epidemiological types of VL have been described: anthroponotic VL (AVL), mountain-type zoonotic VL (MT-ZVL), and desert-type ZVL (DT-ZVL). These are transmitted by four different sand fly species: Phlebotomus chinensis, P. longiductus, P. wui, and P. alexandri. In 1951, a detailed survey of VL showed that it was rampant in the vast rural areas west, northwest, and north of the Yangtze River. Control programs were designed and implemented stringently by the government at all administrative levels, resulting in elimination of the disease from most areas of endemicity, except the western and northwestern regions. The control programs consisted of (i) diagnosis and chemotherapy of patients, (ii) identification, isolation, and disposal of infected dogs, and (iii) residual insecticide indoor spraying for vector control. The success of the control programs is attributable to massive and effective mobilization of the general public and health workers to the cause. Nationally, the annual incidence is now very low, i.e., only 0.03/100,000 according to the available 2011 official record. The overwhelming majority of cases are reported from sites of endemicity in the western and northwestern regions. Here, we describe in some depth and breadth the current status of epidemiology, diagnosis, treatment, and prevention of the disease, with particular reference to the control programs. Pertinent information has been assembled from scattered literature of the past decades in different languages that are not readily accessible to the scientific community. The information provided constitutes an integral part of our knowledge on leishmaniasis in the global context and will be of special value to those interested in control programs.

FIG 1

Typical topography of sites of endemicity for leishmaniasis in western and northwestern China. (A) Areas of flat plains, a site with AVL (Ma'anshan City, Anhui); (B) Kashgar alluvial plain, a site of AVL (Kashgar City, Xinjiang); (C) mountainous area with MT-ZVL (Lanzhou City, Gansu); (D) diversifolious poplar tree (Populus diversifolia) in desert with DT-ZVL (Korla City, Xinjiang); (E) branchy tamarisk bush (Tamarix ramosissima Ledeb) in desert with DT-ZVL (Changji City, Xinjiang); (F) pebble desert with DT-ZVL (Turpan, Xinjiang); (G) sacsaoul bush (Haloxylon ammodendron) in desert, Karamay, Xinjiang; (H) pebble desert (Karamay, Xinjiang). Original pictures were contributed by M.-S.W.

FIG 2

Distribution of sand fly vectors in China reported between 1916 and 1983. The distribution of the four sand fly vectors is colored-coded in the map based on data from references , , and . Abbreviations for provinces: AH, Anhui; BJ, Beijing; GS, Gansu; GZ, Guizhou; HN, Henan; HeB, Hebei; HuB, Hubei; HuN, Hunan; IM, Inner Mongolia; JL, Jilin; JS, Jiangsu; LN, Liaoning; NX, Ningxia; QH, Qinghai; SC, Sichuan; SD, Shandong; SHX, Shaanxi; SX, Shanxi; XJ, Xinjiang; XZ, Xizang (Tibet); ZJ, Zhejiang.

FIG 3

Distribution of foci of endemicity and outbreaks of visceral leishmaniasis (VL). Violet triangle, provinces of VL endemicity reported in 1951 (67). Circles, current foci of endemicity (red, anthroponotic visceral leishmaniasis [AVL]; green, mountain-type zoonotic visceral leishmaniasis [MT-ZVL]; yellow, desert-type zoonotic visceral leishmaniasis [DT-ZVL]). Green and pale blue, provinces where VL presently is and is not endemic, respectively (14, 71, 75). Brown area, a focus of cutaneous leishmaniasis (CL) endemicity at Karamay, Xinjiang (4). Inset, expanded Kashgar region showing the sites of recent outbreaks (red triangles) (76, 77). For abbreviations for provinces, see the legend to Fig. 2.

FIG 4

National total incidence of visceral leishmaniasis (1951 and 1984 to 2011). From 1980 to 2011, detailed data are available and thus are graphed on an expanded scale. The broken line from 1950 to ∼1980 indicates the trend of decrease in incidence, since the data for this period are incomplete or not available (12, 67–69).

FIG 5

National incidence of visceral leishmaniasis in total number per year reported from 2002 to 2011. The data shown are from the Ministry of Health of the People's Republic of China (2002 to 2011) (69).

FIG 6

Age distribution (in years) of visceral leishmaniasis reported between 2005 and 2010. The data shown are from reference . Abbreviations: AVL, anthroponotic visceral leishmaniasis; MT-ZVL, mountain-type zoonotic visceral leishmaniasis; DT-ZVL, desert-type zoonotic visceral leishmaniasis. Age distributions for all VL types (left panel) and for specific VL types (right panel) are shown.

FIG 7

Occupation distribution of visceral leishmaniasis cases reported between 2005 and 2010. The data shown are from reference . Distributions for all VL types in regions where VL is not endemic (left panel) and in regions where it is endemic (right panel) are shown.

FIG 8

Gender distribution of visceral leishmaniasis reported between 2005 and 2010. The data shown are from reference .

FIG 9

Relative efficacy of insecticide spray for sand fly control and dog control programs against visceral leishmaniasis at various sites of endemicity in Xinjiang, Sichuan, and Gansu. See references to , , and for details of the control programs. Shown are the total number of cases of visceral leishmaniasis per year in relation to the use of different control measures, as indicated, in the following sites of endemicity: Kashgar City, Xinjiang (A); Wenchuan county, Sichuan (B); Lixian county, Sichuan (C); Jiuzhaigou county, Sichuan (D); Wenxian county, Gansu (E); and Heishui county and Maoxian county, Sichuan (F). Vertical axes, number of VL cases; horizontal axes, year; areas framed by dotted lines, duration of sand fly or dog control programs and their outcomes, as indicated in the line graph for the changes of VL; numbers along line graph, number of VL cases recorded in the specific year.