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Rats carry fleas. Fleas may carry plague. The plague may spread to humans, the dread bubonic plague of the middle ages.
--The Road to Health: A Short History of the Seattle King County Health Department. Seattle: Seattle-King County Department of Public Health, 1954

After bubonic plague claimed a Seattle life in 1907, bounties of five and later ten cents per rat were set for each rat trapped and returned to the Health Department. Special inspectors, regulations and a laboratory were set up to curb the threat posed by infected rodents. In addition to these rat abatement measures, the development of better waste management processes helped to reduce the prevalence of rats and flies in Seattle and King County. By the 1950s rodent control focused on prevention and rat-proofing buildings.

In 1946 rodent and pest control operations were consolidated into one unit. While mosquitoes did not pose a major public health crisis, they were considered a nuisance. The Department used a number of mosquito control substances throughout the years including oil, larvacides, and DDT. By 1946 an aerosol generator that produced a fog containing either DDT or diesel oil was used. Spraying equipment and vehicles included a knapsack-type sprayer, a three-wheeled motorcycle, and a shallow draft boat to reach swamps, a 4-wheel drive truck, and a helicopter. In 1964 the Department acquired a new mosquito-fogging machine and a new "orchard type" trailer-mounted sprayer.

As part of the mosquito control program, the Department's Education Division conducted a public education campaign throughout May 1962. This initiative included television announcements, a radio interview, newspaper publicity, and distribution of mosquito control brochures.

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