No abstract

Recent bacteriological investigations of freshwater mussel mortality events in the southeastern United States have identified a variety of bacteria and differences in bacterial communities between sick and healthy mussels. In particular, Yokenella regensburgei and Aeromonas spp. have been shown to be associated with moribund mussels, although it remains unclear whether these bacteria are causes or consequences of disease. To further understand the role of bacteria in mussel epizootics, we investigated mortality events that occurred in the upper Midwest in the Embarrass River (Wisconsin) and the Huron River (Michigan). For comparison, we also studied mussels from an unaffected population in the St. Croix River (Wisconsin). Diverse bacterial genera were identified from these sites, including Y. regensburgei from moribund mussels in the Embarrass River (Wisconsin). This bacterium has also been consistently isolated during ongoing mortality events in the Clinch River (Virginia). Subsequently, we developed and validated molecular assays for the detection of Yokenella to use in future investigations of mussel mortality events and to identify environmental reservoirs of this bacterium.

In January 2020, a mortality event was documented in endangered Pallid Sturgeon (Scaphirhynchus albus) at the Neosho National Fish Hatchery (Neosho, MO, USA). Moribund fish appeared emaciated, with hemorrhages on the fins and rostrums. Mortality steadily increased, prompting an investigation into the cause. No viral or bacterial pathogens were detected; however, a high number of the novel Gyrodactylus sp. was identified on the fins and body surface of the affected fish. Treatment of the parasites with a formalin product was effective, and mortality decreased. Herein, we describe the novel species Gyrodactylus conei using a combination of morphological and molecular data. Due to the listing of the host as an endangered species, the concept of parasite conservation is also discussed.

Lactic acid bacteria (LAB) in the order Lactobacillales are a ubiquitous group of Gram-positive bacteria found in terrestrial and aquatic environments, urogenital and gastrointestinal tracts of animals and humans, and fermented products (

In July of 2018 and 2019, wild fish health surveys were conducted along the Wisconsin and Minnesota portions of the upper Mississippi River. Spring viremia of carp virus (SVCV) was isolated from Common Carp Cyprinus carpio as well as a newly identified host species, the Quillback Carpiodes cyprinus. Sanger sequencing of the gene encoding for the G protein revealed a high similarity of the Quillback isolate to various SVCV isolates identified from Common Carp that were collected during earlier wild fish health surveys and mortality events in the USA. Despite annual monitoring, this virus has been infrequently identified. The speculative role of native fish and invertebrates in allowing the virus to persist for long periods without detection is discussed.