Roof rats (Rattus rattus) are common invasive pests in both urban and agricultural sites as well as a significant public health threat. The use of anticoagulant rodenticides to help control the rodent population poses a risk of developing resistance to these products. Several reports have associated the non-synonymous Single Nucleotide Polymorphism (nsSNP) Tyr25Phe (Y25F) of the vitamin K epoxide reductase subcomponent 1 (Vkorc1) gene to anticoagulant rodenticide resistance (Diaz et al. 2021). We conducted a nsSNP screen in the population of Rattus spp. in Orange County to determine the prevalence of the Y25F nsSNP in the sampled rodents. Thirty-seven live rat traps were set throughout the county and the species of each trapped rat was determined by sequencing the cytochrome oxide I (COI) gene using primers previously described in Goulois et al. (2015). Twenty specimens were identified as R. rattus and 12 as R. tanezumi (Asian house rat); the other five specimens were non-Rattus species. To further evaluate the rat species, we used tree-based methods using sequence alignments for three mitochondrial DNA regions, cytochrome b, COI, and non-coding displacement (D) loop using a different set of primers used by Robins et al. (2007). Sequences were aligned by Geneious Prime (v.2020.2.4), and maximum-likelihood phylogeny using 1,000 bootstrap replications was constructed using Mega (10.2.6). Sequences were compared to reference sequences in Robins et al. (2007) and Rattus norvegicus (Norway rat) was used to root the tree. Phylogenetic analysis confirmed the presence of R. tanezumi in our collected samples as well as two haplotypes of R. rattus. In addition to the concatenated data set, each gene was examined individually, and all phylogenetic trees generally agreed on topology. The Y25F nsSNP was present in both R. rattus (40%; 8 of 20) and R. tanezumi (16.67%; 2 of 12). Further genetic testing in Orange County and other areas of Southern California are needed to determine the extent of these Rattus populations and their hybridization as well as the presence of this adaptive trait.

Fleas infesting urban wildlife have been epidemiologically linked to the transmission of flea-borne rickettsial pathogens in urban and suburban areas of Orange County, California. To understand the prevalence of flea-borne rickettsioses caused by either Rickettsia felis or R. typhi, a survey of fleas from wildlife was conducted to determine the flea species composition of host animals and prevalence of rickettsial pathogens in fleas on host animals. This study reports flea abundance, species composition, and infestation intensity on unowned domestic cats and wildlife (i.e., coyotes, opossums, rabbits, skunks, squirrels, raccoons, and commensal rodents) collected in urban neighborhoods of Orange County. The survey revealed presence of the northern rat flea on eastern fox squirrels, and widespread distribution of the human flea on skunks and coyotes in Orange County. The flea index and prevalence of flea-bone rickettsioses in fleas has been used by the Orange County Mosquito and Vector Control District to guide decisions regarding risk management and intervention strategies to reduce and prevent the transmission of flea-borne pathogens. The prevalence of R. felis and R. typhi in fleas in Orange County was 8.94% and 0.39%, respectively. Roof rats, eastern fox squirrels, and striped skunks had the highest diversity of flea species, while the Virginia opossum had the lowest, as determined by the Simpson’s Diversity Index. The sticktight flea was found to have the highest diversity of mammal hosts. It is not known how flea species composition on hosts impacts the maintenance and persistence of rickettsial and other pathogens in fleas from urban wildlife in Orange County.

Lung cancer is the leading cause of cancer mortality worldwide and KRAS is the most commonly mutated gene in lung adenocarcinoma (LUAD). The 78-kDa glucose-regulated protein GRP78/BiP is a key endoplasmic reticulum chaperone protein and a major pro-survival effector of the unfolded protein response (UPR). Analysis of the Cancer Genome Atlas database and immunostain of patient tissues revealed that compared to normal lung, GRP78 expression is generally elevated in human lung cancers, including tumors bearing the KRAS^G12D mutation. To test the requirement of GRP78 in human lung oncogenesis, we generated mouse models containing floxed Grp78 and Kras Lox-Stop-Lox G12D (Kras^LSL-G12D) alleles. Simultaneous activation of the Kras^G12D allele and knockout of the Grp78 alleles were achieved in the whole lung or selectively in lung alveolar epithelial type 2 cells known to be precursors for adenomas that progress to LUAD. Here we report that GRP78 haploinsufficiency is sufficient to suppress Kras^G12D-mediated lung tumor progression and prolong survival. Furthermore, GRP78 knockdown in human lung cancer cell line A427 (Kras^G12D/+) leads to activation of UPR and apoptotic markers and loss of cell viability. Our studies provide evidence that targeting GRP78 represents a novel therapeutic approach to suppress mutant KRAS-mediated lung tumorigenesis.