Studies on plague in the eastern Cape Province of South Africa.

Investigations were carried out in the area of a human plague outbreak in March 1982 at Coega in the eastern Cape Province of South Africa. Trapping revealed that rodent populations were high owing primarily to a population increase of the four-striped mouse, Rhabdomys pumilio. Flea populations were low and had been declining in the eastern Cape Province since October 1981. The results of a serological survey from March to October 1982 showed haemagglutinating antibody to Yersinia pestis in 0.35% of 5938 dog sera and 0.53% of 1132 small mammal sera. Plague antibody was detected in two small mammal species, R. pumilio and the vlei rat, Otomys irroratus. There was thus evidence that a small, limited rodent epizootic preceded the human plague cases and it appears that at least one human case was contracted from an infected domestic cat. The extent of the enzootic area was confined to a coastal belt north of Port Elizabeth and showed a close correlation with river courses. It was concluded that the Port Elizabeth-Uitenhage focus was in an inter-epidemic phase and that the human plague outbreak was an isolated incident.