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Evaluation of mammalian and intermediate host surveillance methods for detecting schistosomiasis reemergence in southwest China.

Carlton EJ, Bates MN, Zhong B, Seto EY, Spear RC - PLoS Negl Trop Dis (2011)

Bottom Line: Screening bovines for S. japonicum and surveys for the presence of O. hupensis had modest sensitivity (59% and 69% respectively) and specificity (67% and 44%, respectively).Older adults and bovine owners were at elevated risk of infection.Testing only these high-risk human populations yielded sensitivities of 77% and 71%, respectively.

View Article: PubMed Central - PubMed

Affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, California, USA. ejcarlton@berkeley.edu

ABSTRACT

Background: Schistosomiasis has reemerged in China, threatening schistosomiasis elimination efforts. Surveillance methods that can identify locations where schistosomiasis has reemerged are needed to prevent the further spread of infections.

Methods and principal findings: We tested humans, cows, water buffalo and the intermediate host snail, Oncomelania hupensis, for Schistosoma japonicum infection, assessed snail densities and extracted regional surveillance records in areas where schistosomiasis reemerged in Sichuan province. We then evaluated the ability of surveillance methods to identify villages where human infections were present. Human infections were detected in 35 of the 53 villages surveyed (infection prevalence: 0 to 43%), including 17 of 28 villages with no prior evidence of reemergence. Bovine infections were detected in 23 villages (infection prevalence: 0 to 65%) and snail infections in one village. Two common surveillance methods, acute schistosomiasis case reports and surveys for S. japonicum-infected snails, grossly underestimated the number of villages where human infections were present (sensitivity 1% and 3%, respectively). Screening bovines for S. japonicum and surveys for the presence of O. hupensis had modest sensitivity (59% and 69% respectively) and specificity (67% and 44%, respectively). Older adults and bovine owners were at elevated risk of infection. Testing only these high-risk human populations yielded sensitivities of 77% and 71%, respectively.

Conclusions: Human and bovine schistosomiasis were widespread in regions where schistosomiasis had reemerged but acute schistosomiasis and S. japonicum-infected snails were rare and, therefore, poor surveillance targets. Until more efficient, sensitive surveillance strategies are developed, direct, targeted parasitological testing of high-risk human populations should be considered to monitor for schistosomiasis reemergence.

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The age distribution of 4,279 residents from 53 villages in regions where schistosomiasis reemerged.
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pntd-0000987-g001: The age distribution of 4,279 residents from 53 villages in regions where schistosomiasis reemerged.

Mentions: There were few teenagers and young adults among the study population relative to other age groups (Figure 1). Residents reported many people, particularly younger populations, had left their villages to find work in urban areas. There is also a dip in the population corresponding with the birth years 1959 to 1961, the years of the Chinese famine. Travel outside of the village was common among study participants. Most young adults (aged 18–29 years) reported spending at least one month out of their village in the past year, as did 40% of adults aged 30–39 years and 26% of adults aged 40–49 years. Most of these individuals left to work as laborers. Some teenagers (aged 12–17 years) also reported living outside of their village for more than one month in the past year (21%), primarily to attend school.


Evaluation of mammalian and intermediate host surveillance methods for detecting schistosomiasis reemergence in southwest China.

Carlton EJ, Bates MN, Zhong B, Seto EY, Spear RC - PLoS Negl Trop Dis (2011)

The age distribution of 4,279 residents from 53 villages in regions where schistosomiasis reemerged.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3050915&req=5

pntd-0000987-g001: The age distribution of 4,279 residents from 53 villages in regions where schistosomiasis reemerged.
Mentions: There were few teenagers and young adults among the study population relative to other age groups (Figure 1). Residents reported many people, particularly younger populations, had left their villages to find work in urban areas. There is also a dip in the population corresponding with the birth years 1959 to 1961, the years of the Chinese famine. Travel outside of the village was common among study participants. Most young adults (aged 18–29 years) reported spending at least one month out of their village in the past year, as did 40% of adults aged 30–39 years and 26% of adults aged 40–49 years. Most of these individuals left to work as laborers. Some teenagers (aged 12–17 years) also reported living outside of their village for more than one month in the past year (21%), primarily to attend school.

Bottom Line: Screening bovines for S. japonicum and surveys for the presence of O. hupensis had modest sensitivity (59% and 69% respectively) and specificity (67% and 44%, respectively).Older adults and bovine owners were at elevated risk of infection.Testing only these high-risk human populations yielded sensitivities of 77% and 71%, respectively.

View Article: PubMed Central - PubMed

Affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, California, USA. ejcarlton@berkeley.edu

ABSTRACT

Background: Schistosomiasis has reemerged in China, threatening schistosomiasis elimination efforts. Surveillance methods that can identify locations where schistosomiasis has reemerged are needed to prevent the further spread of infections.

Methods and principal findings: We tested humans, cows, water buffalo and the intermediate host snail, Oncomelania hupensis, for Schistosoma japonicum infection, assessed snail densities and extracted regional surveillance records in areas where schistosomiasis reemerged in Sichuan province. We then evaluated the ability of surveillance methods to identify villages where human infections were present. Human infections were detected in 35 of the 53 villages surveyed (infection prevalence: 0 to 43%), including 17 of 28 villages with no prior evidence of reemergence. Bovine infections were detected in 23 villages (infection prevalence: 0 to 65%) and snail infections in one village. Two common surveillance methods, acute schistosomiasis case reports and surveys for S. japonicum-infected snails, grossly underestimated the number of villages where human infections were present (sensitivity 1% and 3%, respectively). Screening bovines for S. japonicum and surveys for the presence of O. hupensis had modest sensitivity (59% and 69% respectively) and specificity (67% and 44%, respectively). Older adults and bovine owners were at elevated risk of infection. Testing only these high-risk human populations yielded sensitivities of 77% and 71%, respectively.

Conclusions: Human and bovine schistosomiasis were widespread in regions where schistosomiasis had reemerged but acute schistosomiasis and S. japonicum-infected snails were rare and, therefore, poor surveillance targets. Until more efficient, sensitive surveillance strategies are developed, direct, targeted parasitological testing of high-risk human populations should be considered to monitor for schistosomiasis reemergence.

Show MeSH
Related in: MedlinePlus