Utilizing fluorescence in-situ hybridization to detect Streptococcus phocae in nasopulmonary mites and assess their role in respiratory disease transmission in Southern sea otters

Southern sea otters are frequently infested with nasopulmonary mites (NPMs), Halarachne halichoeri, obligate endoparasites that inhabit the respiratory tract and cause significant pathology. These mites can induce inflammation, mucosal irritation, epithelial damage, respiratory illness, and, in severe cases, death. Recent evidence suggests that NPMs can harbor numerous pathogens, including Streptococcus phocae, an opportunistic pathogen linked to pneumonia, septicemia, and severe abscessation in sea otters and other marine mammals. NPMs may facilitate infection by creating entry points through tissue damage, mechanically contaminating sites, or serving as biological hosts for bacterial propagation, but the specific role of mites in transmitting S. phocae remains unclear.

I hypothesize that NPMs may act as either mechanical or biological vectors of S. phocae. To explore this possibility, I will examine the anatomical localization of S. phocae within NPMs using single-cell fluorescence in situ hybridization (FISH). This technique employs fluorescently labeled RNA probes that specifically target S. phocae, enabling visualization of the bacterium’s presence and distribution within various regions of the mites.

If S. phocae is found only in the NPMs’ digestive tracts, it may indicate passive acquisition, while its presence in the mouthparts or systemically would suggest a higher transmission potential, supporting the role of mites as mechanical or biological vectors. By developing species-specific FISH probes for arthropod parasites, this study advances tools for investigating pathogen transmission in marine mammals. More broadly, it enhances our understanding of parasite-borne pathogen transmission and demonstrates how FISH can support wildlife disease research, conservation, and prevention efforts.