PMC10106728_01
Computed tomographic (CT) transverse image centered on the mid-thorax reconstructed in a lung algorithm of an adult male Stenella frontalis. Diffusely, the pulmonary parenchyma has a severe increase in soft tissue attenuation and contains multifocal and ill-defined soft tissue attenuating nodules, some of which have mineral foci (black arrows).
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F1
CT images revealed that the pulmonary parenchyma had severely increased soft tissue attenuation bilaterally (Figure 1). Within the lungs there were numerous small, poorly-defined, rounded soft-tissue attenuating nodules, some with mineral attenuating foci (Figure 1).
Gross necropsy findings in an adult male Stenella frontalis included a 1.0 x 0.8 cm ulcerated lesion (white arrow) on the ventral aspect of the tongue (A), lungs with multifocal to coalescing white raised nodules (B) with necrotic debris within bronchi (black arrow), and thick mucus and 1 to 4 mm free floating white debris in the anterior trachea (C).
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F2
An ulcerated lesion was present on the ventral aspect of the tongue (Figure 2A). There were multifocal to coalescing regions of white, palpable nodules in the lungs (Figure 2B) that correlated to the nodules identified on CT, as well as thick mucus and white material in the anterior trachea (Figure 2C) and secondary bronchi.
Tissue sections and imprint cytology from an adult male Stenella frontalis. (A) Imprint of tongue lesion. Mixed bacterial infection with suppurative inflammation, characterized by extracellular and phagocytosed mixed bacilli, diplococci, and spirilliform bacteria (1000x; hematoxylin and eosin stain [HE]). (B) Imprint of tracheal mucosa. There is a dense mat of septate branching fungal hyphae and mixed bacilli (1000x; HE). PCR on frozen lung tissue identified the fungus as Aspergillus fumigatus. (C) Photomicrograph of leptomeninges in cerebral sulcus. Mixed leukocytes, with a predominant population of lymphocytes and histiocytes expand the leptomeninges (400x; HE). (D) Photomicrograph of the right midbrain. Apicomplexan protozoa (black arrow) are present in a focus of malacia and gliosis (600x; HE). (E) Photomicrograph of right frontal cortex. Apicomplexan bradyzoites (black arrow) are adjacent to a vessel in the gray matter. Increased numbers of glial cells are scattered throughout the neuroparenchyma (600x; hematoxylin and eosin stain). PCR on frozen central nervous system tissue identified Sarcocystis speeri within the samples. (F) Photomicrograph of tongue lesion. There is regional ulceration of the glossal mucosa with a underlying bed of cellular and necrotic debris, and intact and degenerate neutrophils. HE; 100x. [Inset] Large numbers of spirilliform bacteria are present throughout the ulcerative lesion (600x; Warthin-Starry stain). PCR on frozen tongue tissue identified the bacteria as a Treponema sp.
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F3
Cytologic findings based on tissue imprints stained with Wright-Giemsa (Harleco  EMD Millipore, Billerica, MA, USA) included reactive hyperplasia of the prescapular lymph node, and suppurative inflammation with squamous cell hyperplasia and mixed bacterial infection of the tongue lesion with abundant extracellular and phagocytized bacilli, diplococci, and spirilliform bacilli (Figure 3A). The tracheal mucosa had suppurative inflammation with respiratory epithelial cell hyperplasia, mixed bacilli, and dense mats of branching fungal hyphae (Figure 3B). Histologically, using standard hematoxylin and eosin staining methods, there was severe, chronic-active, suppurative bronchopneumonia with bronchiectasis and associated mixed bacilli and fungal hyphae, as well as chronic, lymphohistiocytic, meningoencephalomyelitis and gliosis with protozoa and rare protozoal cysts (Figures 3C-E). Marked chronic-active suppurative glossitis with ulceration and mixed bacteria, moderate lingual sialadenitis, and severe chronic-active suppurative prostatitis were identified, but considered of questionable significance regarding their role as contributing factors to cause of death (Figure 3F). Warthin-Starry staining of the tongue lesion highlighted the spirilliform bacteria noted on cytology that were not identifiable on routine hematoxylin and eosin stained sections (Figure 3F inset).
MAFFT alignment Bayesian phylogenetic tree representative of homologous 170 to 173 base pair 23S rRNA sequences of Spirochaetes closely related to a novel Treponema species identified from an ulcerative tongue lesion in a Stenella frontalis. The outgroup used was Spirochaeta thermophila (Genbank accession CP002903). Bayesian posterior probabilities are written in black, above the maximum likelihood bootstrap values, which are written in green. Both posterior probabilities and maximum likelihood bootstrap values were rounded to the nearest whole percent. The novel Treponema species (Candidatus Treponema stenella) is identified by a red arrow, Treponema spp. associated with bovids, humans, pigs or rabbits are identified by accompanying graphics of those species.
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F4
Maximum likelihood bootstrap values are shown on the Bayesian tree (Figure 4).