This is the first confirmation of human disease associated with the SFGR 364D, which was likely transmitted by D. occidentalis. Although the patients described here presented with a single cutaneous eschar as the principal manifestation, the full spectrum of illness associated with 364D has yet to be determined. Possible infection with 364D or other SFGR should be confirmed through molecular techniques in patients who present with "spotless" Rocky Mountain spotted fever or have serum antibodies to R. rickettsii with group-specific assays.

Knowledge of the host-feeding behavior and extent of interactions with human hosts are important in evaluating the role and vector potential of invasive mosquitoes in transmission of native arboviruses. We collected blood-engorged females of the recently established exotic species Aedes japonicus japonicus from sites in New Jersey during 2000 to 2007 and identified the sources of vertebrate blood meals by sequencing portions of the cytochrome b gene of mitochondrial DNA. Over 1/3 (36%, n = 36) of the engorged mosquitoes acquired blood meals from humans. Other mammalian hosts included white-tailed deer (53%), fallow deer (5%), horse (3%), and Virginia opossum (3%). No avian, amphibian, reptilian, or mixed blood meals were identified. Our detection of a comparatively high prevalence of human bloodfeeding in Ae. j. japonicus in association with its local abundance, vector competence, and repeated detection of West Nile virus from field-collected specimens illustrates the potential for this invasive mosquito to serve as a "bridge" vector in transmission of West Nile and other mosquito-borne viruses in North America.

Rickettsia philipii (type strain “Rickettsia 364D”), the etiologic agent of Pacific Coast tick fever (PCTF), is transmitted to people by the Pacific Coast tick, Dermacentor occidentalis. Following the first confirmed human case of PCTF in 2008, 13 additional human cases have been reported in California, more than half of which were pediatric cases. The most common features of PCTF are the presence of at least one necrotic lesion known as an eschar (100%), fever (85%), and headache (79%); four case-patients required hospitalization and four had multiple eschars. Findings presented here implicate the nymphal or larval stages of D. occidentalis as the primary vectors of R. philipii to people. Peak transmission risk from ticks to people occurs in late summer. Rickettsia philipii DNA was detected in D. occidentalis ticks from 15 of 37 California counties. Similarly, non-pathogenic Rickettsia rhipicephali DNA was detected in D. occidentalis in 29 of 38 counties with an average prevalence of 12.0% in adult ticks. In total, 5,601 ticks tested from 2009 through 2015 yielded an overall R. philipii infection prevalence of 2.1% in adults, 0.9% in nymphs and a minimum infection prevalence of 0.4% in larval pools. Although most human cases of PCTF have been reported from northern California, acarological surveillance suggests that R. philipii may occur throughout the distribution range of D. occidentalis.

We describe methodology used for the laboratory colonization of Aedes japonicus japonicus, an exotic mosquito species native to eastern Asia and first collected in New Jersey as larvae in 1999. We created a free mating colony in 2000 that readily bloodfed on restrained bobwhite quail (Colinus virginianus). A larval diet of finely ground Purina Lab Diet dissolved in dechlorinated water has proven acceptable. This is the first report of Ae. j. japonicus colonization from mosquitoes collected in the United States.