Wild-rodent-flea control in rural areas of an enzootic plague region in Hawaii; a preliminary investigation of methods.

Preliminary field tests were carried out to develop methods for controlling fleas on wild rodents in the enzootic plague region of the Island of Hawaii. Among several designs, a metal hood-type DDT bait-box was developed which was simple in design, low in cost, easy to transport to and maintain in the field, protected the insecticide from the elements, and attracted all species of field rats inhabiting a gulch in the Hamakua District. These rats-Rattus rattus (and its subspecies), R. norvegicus, and R. hawaiiensis-readily fed in the DDT bait-boxes and were dusted with 10% DDT powder (in pyrophyllite) on contacting hanging cloth sacks, containing the insecticide, when entering and leaving the bait-boxes. The results indicate that a reduction of the plague-vector fleas, Xenopsylla cheopis and X. vexabilis hawaiiensis, may be obtained both on rats and within their burrows and nests, by the use of DDT bait-boxes. It is suggested that the use of such bait-boxes for wild-rodent-flea control may constitute a valuable method in the prevention of epizootics of plague in the Hamakua District, Hawaii.