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. 2022 Jun 9;16(6):e0010405.
doi: 10.1371/journal.pntd.0010405. eCollection 2022 Jun.

National surveillance of hookworm disease in China: A population study

Hui-Hui Zhu  1 , Ji-Lei Huang  1 , Ying-Dan Chen  1 , Chang-Hai Zhou  1 , Ting-Jun Zhu  1 , Men-Bao Qian  1   2 , Mi-Zhen Zhang  1 , Shi-Zhu Li  1   2 , Xiao-Nong Zhou  1   2
Affiliations

National surveillance of hookworm disease in China: A population study

Hui-Hui Zhu et al. PLoS Negl Trop Dis. .

Abstract

Background: Hookworm disease is endemic in China and is widespread globally. The disease burden to humans is great.

Methods: The study described the national surveillance of hookworm implemented in 31 provinces/autonomous regions/municipalities (P/A/Ms) of China in 2019. Each P/A/M determined the number and location of surveillance spots (counties). A unified sampling method was employed, and at least 1000 subjects were investigated in each surveillance spot. The modified Kato-Katz thick smear method was employed for stool examination. Fifty samples positive with hookworm eggs were cultured in each surveillance spot to discriminate species between A. duodenale and N. americanus. Twenty-five soil samples were collected from each surveillance spot and examined for hookworm larva. The 2019 surveillance results were analyzed and compared with that of 2016-2018.

Results: A total of 424766 subjects were investigated in 31 P/A/Ms of China in 2019, and the overall hookworm infection rate was 0.85% (3580/424766). The weighted infection and standard infection rates were 0.66% (4288357/648063870) and 0.67% (4343844/648063870), respectively. Sichuan province had the highest standard infection rate (4.75%) in 2019, followed by Chongqing (2.54%) and Hainan (2.44%). The standard infection rates of other P/A/Ms were all below 1%, with no hookworm detected in 15 P/A/Ms. The standard hookworm infection rate in the males and the females were 0.61% (2021216/330728900) and 0.71% (2267141/317334970), respectively, with a significant difference between different genders ([Formula: see text] = 17.23, P<0.0001). The highest standard hookworm infection rate (1.97%) was among age ≥ 60 years, followed by 45~59 years (0.77%), 15~44 years (0.37%), and 7~14 years (0.20%). The lowest standard infection rate was among the 0~6 years age group (0.12%). A significant difference was observed among different age groups ([Formula: see text] = 2 305.17, P<0.0001). The constitute ratio for N. americanus, A. duodenale, and coinfection was 78.70% (1341/1704), 2.03% (346/1704), and 1.00% (17/1704), respectively. The detection rate of hookworm larva from soil was 3.45% (71/2056).

Conclusion: The national surveillance showed that the hookworm infection rate has been decreasing annually from 2016 to 2019, and it is now below 1%. China has made significant progress in controlling hookworm. The national surveillance system is an important way to understand the endemic status and provide important information in this process and thus needs to be continually optimized.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Distribution of national surveillance spots of STH in 2019.
(https://www.webmap.cn/mapDataAction.do?method=forw&resType=5&storeId=2&storeName=%E5%9B%BD%E5%AE%B6%E5%9F%BA%E7%A1%80%E5%9C%B0%E7%90%86%E4%BF%A1%E6%81%AF%E4%B8%AD%E5%BF%83&fileId=BA420C422A254198BAA5ABAB9CAAFBC1).
Fig 2
Fig 2. Distribution of hookworm infections in different P/A/Ms from 2016 to 2019 according to the national surveillance in China.
A. Infection rate; B. Weighted infection rate; C. Standard infection rate. (https://www.webmap.cn/mapDataAction.do?method=forw&resType=5&storeId=2&storeName=%E5%9B%BD%E5%AE%B6%E5%9F%BA%E7%A1%80%E5%9C%B0%E7%90%86%E4%BF%A1%E6%81%AF%E4%B8%AD%E5%BF%83&fileId=BA420C422A254198BAA5ABAB9CAAFBC1).
Fig 3
Fig 3. Spatial distribution of hookworm infections from 2016 to 2019 according to the national surveillance in China.
A. Infection rate; B. Weighted infection rate; C. Standard infection rate. (https://www.webmap.cn/mapDataAction.do?method=forw&resType=5&storeId=2&storeName=%E5%9B%BD%E5%AE%B6%E5%9F%BA%E7%A1%80%E5%9C%B0%E7%90%86%E4%BF%A1%E6%81%AF%E4%B8%AD%E5%BF%83&fileId=BA420C422A254198BAA5ABAB9CAAFBC1).
Fig 4
Fig 4. Gender distribution of hookworm infections from 2016 to 2019 according to the national surveillance.
A. Infection rate; B. Weighted infection rate; C. Standard infection rate.
Fig 5
Fig 5. Age distribution of hookworm infections from 2016 to 2019 according to the national surveillance.
A. Infection rate; B. Weighted infection rate; C. Standard infection rate.
Fig 6
Fig 6. Educational distribution of hookworm infections from 2016 to 2019 according to the national surveillance.
A. Infection rate; B. Weighted infection rate; C. Standard infection rate.
Fig 7
Fig 7. Occupation distribution of hookworm infections from 2016 to 2019 according to the national surveillance.
A. Infection rate; B. Weighted infection rate; C. Standard infection rate.
Fig 8
Fig 8. Constitute ratio (%) of infection intensity from 2016 to 2019.
Fig 9
Fig 9. Constituent ratio (%) of hookworm species in China from 2016 to 2019.
See this image and copyright information in PMC

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