Teles Horacio Manuel Santana, Ferreira Cláudio Santos, de Carvalho Maria Esther, de Lima Valquíria Rosa, Zacharias Fabiana
Laboratório de Malacologia, Coordenação dos Laboratórios de Referência e Desenvolvimento Científico, Superintendência de Controle de Endemias, São Paulo, SP, 01027-000, Brasil.
Mem Inst Oswaldo Cruz. 2002;97 Suppl 1:37-41. doi: 10.1590/s0074-02762002000900009.
We conducted monthly snail captures in Bananal, State of São Paulo, Brazil, between March 1998 and February 2001, to identify Schistosoma mansoni vectors, estimate seasonal population changes, and delimit foci. We also evaluated the impact of improvements in city water supply and basic sanitation facilities. We identified 28,651 vector specimens, 28,438 as Biomphalaria tenagophila, 49 of them (0.2%) infected with S. mansoni, and 213 as B. straminea, none of the latter infected. Vectors predominated in water bodies having some vegetation along their banks. Neither population density nor local vegetation could be linked to vector infection. We found the first infected snails in 1998 (from March to May). Further captures of infected snails ocurred, without exception, from July to December, when rainfall was least. Irrespective of season, overall temperature ranged from 16.5 degrees C to 21 degrees C; pH values, from 6.0 to 6.8. Neither factor was associated with snail population density. Frequent contact of people with the river result from wading across it, extracting sand from its bottom, fishing, washing animals, etc. Despite a marked reduction in contamination, cercaria shedding persists. Whatever the location along its urban course, contact with river Bananal, particularly of the unprotected skin, entails risks of infection.
1998年3月至2001年2月期间，我们在巴西圣保罗州的巴纳纳尔岛每月进行一次蜗牛捕捉，以确定曼氏血吸虫的传播媒介，估计季节性种群变化，并划定疫源地。我们还评估了城市供水和基本卫生设施改善的影响。我们共鉴定出28,651只传播媒介标本，其中28,438只为嗜卷阿勇蛞蝓，其中49只（0.2%）感染了曼氏血吸虫，213只为淡黄阿勇蛞蝓，后者均未感染。传播媒介主要集中在岸边有一些植被的水体中。种群密度和当地植被都与传播媒介感染无关。我们在1998年（3月至5月）首次发现感染的蜗牛。此后，感染蜗牛的进一步捕获无一例外地发生在7月至12月，即降雨量最少的时候。无论季节如何，总体温度在16.5摄氏度至21摄氏度之间；pH值在6.0至6.8之间。这两个因素都与蜗牛种群密度无关。人们经常通过涉水过河、从河底采砂、捕鱼、清洗动物等方式与河流频繁接触。尽管污染明显减少，但尾蚴的排放仍然存在。无论在其城市河道的哪个位置，与巴纳纳尔河接触，尤其是未受保护的皮肤接触，都有感染风险。
