Plague appeared in Thailand in 1904 and has been endemic ever since. Two epidemics of plague, one at the end of 1951, and the other early in 1952, prompted the Thai Department of Health to establish permanent laboratories for plague detection and control in each of the three known plague areas of Thailand. Routine procedures of control and prevention were used.
The present report discusses the work of these laboratories between February, 1952, and September, 1953, during which period a total of 48,553 domestic rats, Rattus exulans concolor, were obtained by live-trapping. These and some animals collected from the fields and forests were tested for the presence of plague which was detected only in R. exulans and its flea, Xenopsylla cheopis. Indices of this vector were computed monthly and an attempt was made to treat with DDT all villages, cities, or sections of cities, whenever the local X. cheopis index rose above 1.0. The major city in each area was studied in detail; wide oscillations were observed in the flea populations which may or may not have been due to the DDT treatment. Notes are given on the other species of rodents associated with R. exulans.