Rodent-Borne Disease Surveillance at San Bruno Mountain
Disease Surveillance Update

A captured Peromyscus maniculatus mouse is checked for ticks.

The District conducted two wild rodent disease surveys on San Bruno Mountain this year, and all test results have been received.  Each survey consisted of 100 Sherman traps placed along trails, targeting wild mice.  The first survey resulted in fifteen captured Peromyscus maniculatus mice and the second survey resulted in eleven captured P. maniculatus mice. The animals were tested for Hantavirus, plague (a flea-borne disease), and two tick-borne bacteria (Borrelia miyamotoi and Borrelia burgdorferi).  None of the animals tested positive for plague or the tick-borne bacteria.   In both surveys, three mice tested positive for hantavirus, for a total of six positive mammals this year at San Bruno Mountain.

Ealier this spring, hantavirus was detected from one mouse caught in a rodent survey in Montara, out of thirteen total mice sampled .  Both locations, Montara and San Bruno Mountain will have follow-up rodent surveys next year.  Because of the presence of hantavirus in San Mateo County among wild rodents, residents should be careful not to enter buildings that have been closed to air and sunlight in rural areas or near open space.  Peromyscus mice that have nested within the building can shed virus in droppings and urine, which persists in closed, dark spaces.  Hantavirus is not carried by house mice or domestic rats.