Incidents of snake fungal disease caused by the fungal pathogen Ophidiomyces ophidiicola in Texas

Abstract

The pathogen Ophidiomyces ophidiicola, widely known as the primary cause of snake fungal disease (SFD) has been detected in Texas's naïve snakes. Our team set out to characterize O. ophidiicola's spread in eastern Texas. From December 2018 until November 2021, we sampled and screened with ultraviolet (UV) light, 176 snakes across eastern Texas and detected 27. O. ophidiicola's positive snakes using qPCR and one snake in which SFD was confirmed via additional histological examination. Upon finding the ribbon snake with clear clinical display, we isolated and cultured what we believe to be the first culture from Texas. This cultured O. ophidiicola TX displays a ring halo formation when grown on a solid medium as well as cellular autofluorescence as expected. Imaging reveals individual cells within the septated hyphae branches contain a distinct nucleus separation from neighboring cells. Overall, we have found over 1/10 snakes that may be infected in East Texas, gives credence to the onset of SFD in Texas. These results add to the progress of the disease across the continental United States.

Keywords: Ophidiomyces ophidiicola; Texas; UV fluorescence; fungal Infection; snake fungal disease.

Figure 1

Distribution of O. ophidiicola in Texas. Texas State and locations positive for O. ophiodiicola are shown as red dots on the map ( Table 1 ).

Figure 2

Clinical Signs of Snake Fungal Disease in the Field. Photos of collected Western Ribbonsnake (Thamnophis proximus). Panel (A), comparison between the gross lesions on the right eye (“R” in red), and unaffected eye (“L” in white). Panel (B), lesions on ventral scales of the specimen (“Sc” in red). Panel (C), over the top view of lesions on head. Panel (D), side view of right eye lesions and panel (E), View of gross lesions under the chin (“Ch” in red) of the specimen (Snakes handled by first author, Alan Lizarraga, granted permission for photo).

Figure 3

Ultraviolet Fluorescence. The infected deceased Western Ribbonsnake from Figure 2 under UV light (365nm) lamp, images shown are dorsal side (A) and ventral side (B). Areas of intensity signal are evidence of the pathogen, O. ophiodiicola. (C), Transilluminator readings of UV fluorescence between strains O. ophidiicola FL (UAMH #10769) and O. ophidiicola TX. Lane 1, Buffer alone, lane 2, O. ophidiicola TX, Lane 3, O. ophidiicola FL. (D), Confocal microscope imagery of O. ophidiicola TX in light phase and Texas found strain. (E), UV fluorescence after excitement at 358 nm and its emission at 460 nm (blue). Bars: (D, E) = 30 μm.

Figure 4

Colony and Microscopic Features of O. ophidiicola FL. Comparison of colony formation SDA plates: O. ophidiicola FL (A) Light microscope images of hyphae phase: O. ophidiicola FL (B, C). Bars: B = 150 μm; C = 75 μm.

Figure 5

Colony and Microscopic Features of O. ophidiicola TX. Comparison of colony formation SDA plates: O. ophidiicola TX (A) Light microscope images of hyphae phase: O. ophidiicola TX (B, C). Bars: B = 150 μm; C = 75 μm.

Figure 6

Nuclear Staining of O. ophidiicola Hyphae. Comparison of merged bright transparent field and fluorescence nuclear staining (Green) between O. ophidiicola FL panel (A) and O. ophidiicola TX panel (B). Lower set of panels show the hyphae branch point of O. ophidiicola TX first in the light field panel (C) then nuclear orange staining panel (D). Black and white of nuclear staining and defined septate hyphae panel (E). Bars: A and B = 10 µm; C, D, and E = 5 µm.