Measuring exposure to Schistosoma japonicum in China. III. Activity diaries, snail and human infection, transmission ecology and options for control

Yuesheng Li, Adrian C. Sleigh, Gail M. Williams, Allen G.P. Ross, Y. Li, Simon J. Forsyth, Marcel Tanner, Donald P. McManus

    Research output: Contribution to journalArticlepeer-review

    23 Citations (Scopus)

    Abstract

    We used activity diaries and snail detection to relate water contact and Schistosoma japonicum infection among a cohort of 178 residents on two islands in the Dongting Lake, China. Water exposure to each of 12 mapped water zones around the islands was calculated (m2 min/day) for each subject. Infected Oncomelania hupensis hupensis snails in this area are focal and were found in only five of the 12 zones, with the highest rate being 5.7%. Thirty- one subjects (17%) were re-infected with a mean intensity of 63.2 epg. Mean water contact was 7.9 m2 min/day; 98% of water exposure was due to economic activity and only 2% due to swimming or bathing, washing and other necessities of daily life. Males had more exposure and infection than females (P < 0.05). Infected subjects had more exposure (10.2 m2 min/day) than those not infected (7.44 m2 min/day) (P < 0.05). Compared with uninfected subjects, those infected had 2.9 times more exposure in infected-snail zones (P < 0.01). Also, human infection intensity (epg) correlated well with exposure to infected snail zones (r = 0.552, P < 0.01). People < 20 years old had the highest re-infection (21.4%) and intensity (3.77 epg). Median exposure for 20-49-year-olds (9.00 m2 min/day) was nearly double that of those aged < 20 or > 50 years old (5.5 m2 min/day). We conclude that map- referenced water contact and snail evaluation boosts accuracy of activity- diary measurements in large transmission foci for the Asian schistosome. Protecting against faecal contamination of snail inhabited sites, and against occupational exposure for island residents, should be a priority of future research. Potential strategies for migrating buffaloes and families living on visiting fishing boats are explored. (C) 2000 Elsevier Science B.V.

    Original languageEnglish
    Pages (from-to)279-289
    Number of pages11
    JournalActa Tropica
    Volume75
    Issue number3
    DOIs
    Publication statusPublished - 31 May 2000

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