Field study of the safety of abate for treating potable water and observations on the effectiveness of a control programme involving both abate and malathion.

Abate is a larvicide for Aedes aegypti, a vector of yellow fever, dengue, and haemorrhagic fever. It is less toxic than malathion or DDT. Tests in human volunteers had previously indicated it would be safe to add to drinking-water where the mosquito often breeds.In a 19-month test in Puerto Rico, Abate was added to the drums and cisterns in which a community of about 2000 persons stored their drinking-water. This use of Abate and other insecticidal measures (malathion spraying) gradually achieved control of A. aegypti during the first 4 months of treatment and control was maintained thereafter although the test area was surrounded by active breeding-sites. There was no accumulation of Abate in the water in spite of monthly additions of the compound. With minor exceptions, residents readily accepted this use of Abate. Careful surveillance failed to reveal any illness or significant side-effects attributable to measures adopted in the control programme. Abate is considered safe for full-scale field use according to directions.