Field tests of hexabutyldistannoxane (TBTO) in slow-release formulations against Biomphalaria spp

Our plain-English summary of Field tests of hexabutyldistannoxane (TBTO) in slow-release formulations against Biomphalaria spp, by B. Gilbert, L.A. Paesleme, A.M. Ferreira, et al (Bulletin of the World Health Organization, 1973).

The study

• Authors: B. Gilbert, L.A. Paesleme, A.M. Ferreira, M.S. Bulhões, C. Castleton
• Journal: Bulletin of the World Health Organization
• Published: 1973;49(6):633-6
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Abstract

Hexabutyldistannoxane (TBTO) in an asphalt base was found to retain molluscicidal activity for more than a year in the field. It was not deactivated by immersion in mud or by drying and exposure to the sun. Complete elimination of planorbid snails was achieved and maintained when repopulation pressure was sporadic, but control of a continuously entering population was not practicable. Fixing the product at the site is important, and a formulation in fragments of rubber that floated failed after 1-2 months. TBTO apparently acts cumulatively in snails, but is only initially toxic to aquatic insects and fish, which return to repopulate treated areas that remain snail-free.

In plain English

This 1973 article reported field tests in Brazil of a snail-killing chemical, hexabutyldistannoxane (TBTO), in slow-release forms against Biomphalaria snails, which carry schistosomiasis. It was not a study of asbestos or of human health. Asbestos appeared only as an ingredient of one carrier, Underseal, which the authors described as an asphalt-rubber-asbestos-clay paste. The authors coated stones with TBTO mixed into Underseal and placed them in snail sites. They also spread TBTO-soaked rubber granules over marshes, testing eight sites in all. At one still-water site, control with the Underseal form was complete for 1 year. A stone removed after a year still killed snails in laboratory and tank tests. Where snails kept arriving from upstream, control broke down after 1 month. The rubber granules worked for only 1 to 2 months, which the authors suggested might reflect their small size. Fish died at three sites. The authors concluded that complete elimination was achieved and maintained when snails returned only sporadically, but that control of a continuously entering population was not practicable.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field trial of molluscicide formulations at 8 sites, with laboratory and outdoor-tank tests of a treated stone's remaining toxicity
• Who was studied: Snails (Biomphalaria tenagophila, B. straminea, B. glabrata) at 8 field sites in Brazil (Sao Paulo, Guanabara, Rio Grande do Norte and Espirito Santo states). No people were studied. Dates are not given.
• Exposure: Snails were exposed to TBTO in two carriers: Underseal paste containing 17-20% TBTO, coated on stones; and synthetic butadiene-styrene rubber granules. Underseal is described as an asphalt-rubber-asbestos-clay paste. No asbestos exposure of people or animals was studied.
• Main results:
  • At site 3, a limited stationary water body, control with the TBTO-Underseal formulation was complete for 1 year.
  • A treated stone removed after 1 year in the field killed 100% of 100 B. glabrata snails in 24 hours on first immersion. In a 1.6 cubic metre outdoor tank it killed 95% in 10 weeks.
  • A similar stone from site 4, kept in mud and water for 18 months, showed the same remaining toxicity.
  • At site 1, the concrete tank with a very high application rate, activity was retained for 2 years.
  • At site 2, a slowly running ditch, snails arriving from upstream outpaced the kill after 1 month and control broke down.
  • The rubber-granule formulation was active for only 1 to 2 months. The authors said this may be attributed to the small particle size.
  • Fish deaths were seen at sites 1, 2 and 3. At site 4, fish and aquatic insects appeared normal after 1 month.
  • Measurable tin was found in watercress 2 m downstream of the application point at site 2.
• The authors' conclusion: The authors concluded that complete elimination of snails was achieved and maintained when snails returned only sporadically, but that controlling a continuously entering population was not practicable. They also concluded that fixing the product at the site is important.
• Limitations the authors state:
  • At sites 4 and 6-8, no sufficiently similar untreated habitats were available nearby to serve as controls.
  • The very high application rates that gave prolonged control might only be practicable in foci of marked epidemiological importance.
  • Flow rates at the sites were too variable to define precisely.

Topics

Medical terms in this study, explained in our Lexicon: Fluorescence In Situ Hybridization (FISH).

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