Observations on the current status of plague endemicity in the western Usambara mountains, north-east Tanzania.

Epidemiological investigations were executed at 6 locations in the western Usambara mountains in north-east Tanzania from November 1980 to May 1982. Rodent, human and dog sera were checked for agglutinating plague antibodies, using the passive haemagglutination test. Fraction I plague antigen was similarly tested for in rodent organ macerates. Bubo aspirates and rodent organ-smears were microscopically examined for plague bacilli. A total of 257 rodents and 191 fleas were collected. Rattus rattus, Praomys natalensis and Arvicanthis niloticus were the commonest rodent species. Flea ectoparasites mostly comprised of Xenopsylla brasiliensis and Dinopsyllus lypusus. Specific plague antibodies were detected in 2.8%, 10% and 2.9% of the rodents examined in November 1980, November 1981 and May 1982 respectively. Similarly, plague antibodies were found in 0.6%, 1.2% and 0.5% of the human sera tested in September 1981, November 1981 and May 1982 respectively. All the dog sera were negative. The results suggested past contact with plague and existence of a persistent plague focus in the area. Health education for villagers, maintenance of a plague surveillance programme and regular seminars for medical and health personnel in the area were recommended in order to prompt early detection, reporting and control of an outbreak.