The spatial-temporal distribution of soil-transmitted helminth infections in Guangdong Province, China: A geostatistical analysis of data derived from the three national parasitic surveys

Abstract

Background: The results of the latest national survey on important human parasitic diseases in 2015-2016 showed Guangdong Province is still a moderately endemic area, with the weighted prevalence of soil-transmitted helminths (STHs) higher than the national average. High-resolution age- and gender-specific spatial-temporal risk maps can support the prevention and control of STHs, but not yet available in Guangdong.

Methodology: Georeferenced age- and gender-specific disease data of STH infections in Guangdong Province was derived from three national surveys on important human parasitic diseases, conducted in 1988-1992, 2002-2003, and 2015-2016, respectively. Potential influencing factors (e.g., environmental and socioeconomic factors) were collected from open-access databases. Bayesian geostatistical models were developed to analyze the above data, based on which, high-resolution maps depicting the STH infection risk were produced in the three survey years in Guangdong Province.

Principal findings: There were 120, 31, 71 survey locations in the first, second, and third national survey in Guangdong, respectively. The overall population-weighted prevalence of STH infections decreased significantly over time, from 68.66% (95% Bayesian credible interval, BCI: 64.51-73.06%) in 1988-1992 to 0.97% (95% BCI: 0.69-1.49%) in 2015-2016. In 2015-2016, only low to moderate infection risk were found across Guangdong, with hookworm becoming the dominant species. Areas with relatively higher risk (>5%) were mostly distributed in the western region. Females had higher infection risk of STHs than males. The infection risk of A. lumbricoides and T. trichiura were higher in children, while middle-aged and elderly people had higher infection risk of hookworm. Precipitation, elevation, land cover, and human influence index (HII) were significantly related with STH infection risk.

Conclusions/significance: We produced the high-resolution, age- and gender-specific risk maps of STH infections in the three national survey periods across nearly 30 years in Guangdong Province, which can provide important information assisting the control and prevention strategies.

Fig 1. Survey locations and observed prevalence in Guangdong.

(A)-(C) for A. lumbricoides; (D)-(F) for T. trichiura; (G)-(I) for hookworm, during the periods of 1988–1992, 2002–2003 and 2015–2016, respectively. The base layer derived from https://www.webmap.cn/mapDataAction.do?method=forw&keysearch=indexSearch with credit to National Catalogue Service For Geographic Information.

Fig 2. The geographical distribution of A. lumbricoide infection risk in Guangdong.

(A)-(C) present A. lumbricoide infection during the periods of 1988–1992, 2002–2003, and 2015–2016, respectively. (D)-(F) present the corresponding standard deviation of the estimated uncertainty. The base layer derived from https://www.webmap.cn/mapDataAction.do?method=forw&keysearch=indexSearch with credit to National Catalogue Service For Geographic Information.

Fig 3. The geographical distribution of T. trichiura infection risk in Guangdong.

(A)-(C) present T. trichiura infection during the periods of 1988–1992, 2002–2003, and 2015–2016, respectively. (D)-(F) present the corresponding standard deviation of the estimated uncertainty. The base layer derived from https://www.webmap.cn/mapDataAction.do?method=forw&keysearch=indexSearch with credit to National Catalogue Service For Geographic Information.

Fig 4. The geographical distribution of hookworm infection risk in Guangdong.

(A)-(C) present hookworm infection during the periods of 1988–1992, 2002–2003, and 2015–2016, respectively. (D)-(F) present the corresponding standard deviation of the estimated uncertainty. The base layer derived from https://www.webmap.cn/mapDataAction.do?method=forw&keysearch=indexSearch with credit to National Catalogue Service For Geographic Information.

Fig 5. The geographical distribution of any STH infection risk in Guangdong.

(A)-(C) present any STH infection during the periods of 1988–1992, 2002–2003, and 2015–2016, respectively. (D)-(F) present the corresponding standard deviation of the estimated uncertainty. The base layer derived from https://www.webmap.cn/mapDataAction.do?method=forw&keysearch=indexSearch with credit to National Catalogue Service For Geographic Information.

Fig 6. Probability contour maps of any STH infection risk in Guangdong.

(A)-(C) present the probability that prevalence exceeds the threshold for preventive chemotherapy (20%); (D)-(F) present the probability that prevalence exceeds the threshold of transmission control (1%), during the periods of 1988–1992, 2002–2003, and 2015–2016, respectively. The base layer derived from https://www.webmap.cn/mapDataAction.do?method=forw&keysearch=indexSearch with credit to National Catalogue Service For Geographic Information.