Outbreak of Aeromonas hydrophila bacterial dermatosepticemia in wild leopard frogs (Rana pipiens complex) in Mexico

This report presents a case of dermatosepticemia in ten wild leopard frogs (Rana pipiens complex) captured in Mexico, where the presence of Aeromonas hydrophila was confirmed. This polyphasic study included macroscopic, microbiological, histological, and molecular analyses. Externally, the specimens exhibited erythema, hemorrhage, and erosions on various body parts. Internal observations revealed hemorrhaging of the oral cavity and stomach, as well as sero-sanguineous ascites. Parasites were also identified, including Ochoterenella sp. in the mesentery, Glypthelmins sp. in the liver, Clinostomum sp. in the thigh muscles, and Opalina sp. and Glypthelmins sp. in the intestine. Histopathological analyses showed skin hemorrhaging, erosion and ulceration, myositis, coagulative myonecrosis with the presence of bacteria, and damage to internal organs with an abundant presence of bacteria. Aeromonas hydrophila was isolated in pure culture from the skin, muscle, mouth, heart, liver, and kidney of all ten frogs. The Mexican isolate (cos-ciesa 01) had high biochemical-enzymatic similarity to the strain A. hydrophila subsp. hydrophila CECT 4330. Additionally, the Mexican strain's 1 414 bp nucleotide sequence of 16S ribosomal RNA gene (GenBank Accession MN795652) showed high identity with A. hydrophila strain ATCC 7966. Ranavirus was not recovered in the cell cultures and PCR did not detect its DNA from paraffin-embedded tissues. These results suggest A. hydrophila as the causative agent of the dermatosepticemia disease outbreak.