Rodent Disease Updates

Laboratory staff conducted three surveys of wild rodents in the months of July and August. The surveys took place in Montara on July 17th and 18th, at Water Dog Lake park in Belmont on August 15th and 16th and Eaton and Big Canyon parks in San Carlos on August 29th and 30th.  Blood samples were taken from captured rodents by a subocular bleed with a microcapillary tube and ear punches were also taken from the rodents at Water Dog Lake, Eaton and Big Canyon parks.

At Montara, only Peromyscus maniculatus mice were sampled. Blood samples and mouse carcasses were sent to California Department of Public Health (CDPH) for hantavirus testing. This was a follow-up to a previous rodent survey in May, when four of ten P. maniculatus mice tested positive for hantavirus. However, all twelve P. maniculatus mice collected this July tested negative for hantavirus. The reduction in the number of positive animals might be an outcome of the initial small sample size, which was one reason for a follow-up survey, or could be caused by ecological factors that are unclear.

The blood and ear tissue samples from Water Dog Lake and Eaton and Big Canyon parks will be tested in our District laboratory for Borrelia bacteria that cause Lyme disease and other infection. These rodent surveys were part of a larger study to examine tick control along trails by using baited tubes lined with a tick and flea control product to target ticks directly on wild rodents.