Fig 1.
Environmental contamination in the localized infectious zone (LIZ).
Pictures captured during an anthrax outbreak associated with wildlife in West Texas in 2019 representing the high number of flies feeding on a carcass (A), flies contaminating leaves (B), fly deposits on rocks (C), and fly deposits on leaves near an anthrax carcass (D) that is typical of anthrax outbreaks in this area. Insets magnify fly deposits on rocks (E) and leaves (F).
Fig 2.
A comparison of diameters between laboratory experiments and samples collected from the outbreak in Texas.
(A) Averages of droplet volume spotted onto petri dishes in controlled experiments. (B) Averages of fly droplets and emesis on leaves (12 spots from 7 yaupon leaves, 20 spots from 9 oak leaves and 6 spots from3 persimmon leaves) and rocks (10 spots from 2 rocks at site one and 10 spots from 3 rocks at site 2) collected during the 2019 anthrax outbreak in Texas where viable B. anthracis spores were isolated.
Fig 3.
Bacillus anthracis vegetative cell viability on leaf and rock surfaces over a 7-day period.
The number of vegetative cells recovered from leaves (triangles) and rocks (circles) are reported for (A) Ames (UF00738), (B) Ames-like (UF01106), (C) Vollum (UF00980), (D) Vollum-like (UF01103), and (E) Sterne (34F2), illustrating vegetative cell persistence for at least 7 dpi. Results are shown as the mean ± SEM and graphed on a log scale. Significance between days for each strain was determined by Kruskal-Wallis and Dunn’s multiple comparisons tests with leaf temporal differences identified by † = ρ < 0.05 and rock temporal differences identified by # = ρ < 0.05, ## = ρ < 0.01. Significance between surface types on a single day were determined by Mann-Whitney U tests with * = ρ < 0.05.
Fig 4.
Bacillus anthracis spore viability on leaf and rock surfaces over a 7-day period.
The number of spores recovered from leaves (triangles) and rocks (circles) are reported for (A) Ames (UF00738), (B) Ames-like (UF01106), (C) Vollum (UF00980), (D) Vollum-like (UF01103), and (E) Sterne (34F2), illustrating spore persistence for at least 7 dpi. Results are shown as the mean ± SEM and graphed on a log scale. Significance between days for each strain was determined by Kruskal-Wallis and Dunn’s multiple comparisons tests with leaf temporal differences identified by † = ρ < 0.05, †† = ρ < 0.01 and rock temporal differences identified by # = ρ < 0.05, ## = ρ < 0.01. Significance between surface types on a single day were determined by Mann-Whitney U tests with * = ρ < 0.05.
Fig 5.
Differences in spores and sporulation rates from leaves and rocks over 7 days between Sterne strain and fully virulent strains of B. anthracis.
(A) Total spores recovered from leaves, (B) total spores recovered from rocks, (C) sporulation rates on leaves, and (D) sporulation rate from rocks for the Sterne (green), Ames (UF00738, dark blue), Vollum (UF00980, light blue), Ames-like (UF01106, red) and Vollum-like (UF01103, orange) strains are presented as the mean ± SEM. Sporulation rates (spores/day) were calculated from the slope of the lines between each timepoint and graphed on a linear scale. Significant differences in total spores between the Sterne strain and all fully virulent strains were determined by Kruskal-Wallis and Dunn’s multiple comparisons tests with differences identified by * = ρ < 0.05, ** = ρ < 0.01. Significant differences in sporulation rates between days were determined by Kruskal-Wallis and Dunn’s multiple comparisons tests with leaf temporal differences identified by † = ρ < 0.05, †† = ρ < 0.01.
Fig 6.
Comparing spores and sporulation rates between grouped fully virulent laboratory-adapted and wild B. anthracis strains on leaf or rock surfaces over 7 days.
Grouped laboratory-adapted strains (blue) are the averaged spore titers from Ames (UF00738) and Vollum (UF00980) and grouped wild strain values (red) are the averaged spore titers from the Ames-like (UF01106) and Vollum-like (UF01103) strains. Sporulation rates (spores/day) were calculated from the slope of the lines between each timepoints and graphed on a linear scale. Data are presented as the mean ± SEM for (A) total spores recovered from leaves, (B) total spores recovered from rocks, (C) sporulation rate from leaves, and (D) sporulation rate from rocks. The significant differences between laboratory-adapted and wild strains at each time point were determined by Mann-Whitney U tests with * = ρ < 0.05 and ** = ρ < 0.01. Significant differences in sporulation rates between days were determined by Kruskal-Wallis and Dunn’s multiple comparisons tests with leaf temporal differences identified by † = ρ < 0.05.
Table 1.
The comparison of sporulation rates between laboratory-adapted and wild strains at each time points on leaf and rock surfaces.