A 2015 outbreak of flea-borne rickettsiosis in San Gabriel Valley, Los Angeles County, California.

Although flea-borne rickettsiosis is endemic in Los Angeles County, outbreaks are rare. In the spring of 2015 three human cases of flea-borne rickettsiosis among residents of a mobile home community (MHC) prompted an investigation. Fleas were ubiquitous in common areas due to presence of flea-infested opossums and overabundant outdoor cats and dogs. The MHC was summarily abated in June 2015, and within five months, flea control and removal of animals significantly reduced the flea population. Two additional epidemiologically-linked human cases of flea-borne rickettsiosis detected at the MHC were suspected to have occurred before control efforts began. Molecular testing of 106 individual and 85 pooled cat fleas, blood and ear tissue samples from three opossums and thirteen feral cats using PCR amplification and DNA sequencing detected rickettsial DNA in 18.8% of the fleas. Seventeen percent of these cat fleas tested positive for R. felis-specific DNA compared to under two (<2) percent for Candidatus R. senegalensis-specific DNA. In addition, serological testing of 13 cats using a group-specific IgG-ELISA detected antibodies against typhus group rickettsiae and spotted fever group rickettsiae in six (46.2%) and one (7.7%) cat, respectively. These results indicate that cats and their fleas may have played an active role in the epidemiology of the typhus group and/or spotted fever group rickettsial disease(s) in this outbreak.

Life Histories and Other Biological Characteristics Enabling the Establishment of Aedes albopictus in the San Gabriel Valley, California.

Since Aedes albopictus was discovered in 2011 in the San Gabriel Valley it has become widespread despite the "harsh" environmental conditions and intense efforts to control or eliminate it. Species introduced into a new area may survive, thrive, or disappear depending on whether its new environment is suitable. The San Gabriel Valley Mosquito and Vector Control District expended considerable resources from 2011 to 2015 to eradicate this invasive species or, at a minimum, control and manage its spread. Despite the intense effort, the distribution of Ae. albopictus steadily expanded. Over those 5 years this increase shifted from a geometric to exponential pattern. What enabled Ae. albopictus to survive initially, become established, and then expand their distribution when ecological conditions in southern California were considered hostile for this invasive species? This study explores several biological characteristics including skip oviposition, installment egg hatching, and variable larval development that may have helped Ae. albopictus flourish in its new environment.