Diseased animals have been detected in the Santa Monica mountains, foothills north of Fillmore, Ojai, and the Mt. Pinos-Frazier Mountain area. The most important wild rodent reservoirs of plague are ground squirrels and chipmunks. Other rodents that carry plague are squirrels, woodrats, mice, marmots and domestic rats. Plague is lethal to many rodents. Any sign of sick or dead rodents or a high flea population is a warning that plague may be in the area.
Domestic animals can acquire plague and pose a direct threat to humans.
Dogs rarely become ill but cats are highly susceptible and can suffer severe illness and possible death. The usual incubation period is 2 to 10 days. In septicemic stage, the bacteria has moved into the blood stream. In this stage the buboes are inconspicuous. In the pneumonic plague stage, the bacteria moves into the lungs and becomes airborne through normal respiration or when the patent sneezes or coughs.