The seroprevalence of Rocky Mountain spotted fever in shelter dogs in Harris County

Rocky Mountain spotted fever (RMSF) is a tick-borne illness caused by the bacteria Rickettsia rickettsii, with infections occurring in humans and dogs. The prominent tick vector of RMSF, Dermacantor variabilis, and another potential vector, Rhipacephalus sanguineus, are prevalent in Texas. The goal of this study was to determine the prevalence of past infections by testing for IgG antibodies to R. rickettsii in dogs in an animal shelter in Harris County using an immunofluorescence assay (IFA) test. We found that 12.6% (24) of 191 dogs tested had a positive IFA test at 1:64 serum dilution, indicating infection at some time in the past. We also sampled the ticks present on dogs in the animal shelter to understand the prevalence of potential vector species. Of a total of 58 ticks, 86% were D. variabilis and the remaining 14% were R. sanguineus. The results of this study demonstrate that RMSF has the potential to be, and may already be, endemic to the Harris County area. Public health actions such as heightened surveillance and education that RMSF is present would be appropriate in the Harris County area.^

Whole genome analysis of Fusobacterium nucleatum, Rickettsia typhi and Francisella tularensis

The genomes of Fusobacterium nucleatum subspecies polymorphum strain ATCC 10953, Rickettsia typhi strain Wilmington, and Francisella tularensis subspecies holarctica strain OSU18 were sequenced, annotated, and analyzed. Each genome was then compared to the sequenced genomes of closely related bacteria. The genome of F. nucleatum ATCC 10953 was compared to two additional F. nucleatum subspecies, subspecies nucleatum and subspecies vincentii. This analysis revealed substantial evidence of horizontal gene transfer along with considerable genetic diversity within the species of F. nucleatum. R. typhi was compared to R. prowazekii and R. conorii. This analysis uncovered a hotspot for chromosomal rearrangements in the Spotted Fever Group but not the Typhus Group Rickettsia and revealed the close genetic relationship between the Typhus Group rickettsial species. F. tularensis OSU18 was compared to two additional F. tularensis strains. These comparisons uncovered significant chromosomal rearrangements between F. tularensis subspecies due to recombination between insertion sequence elements. ^