Toxicity of Clostridium Botulinum Type E Neurotoxin to Great Lakes Fish: Implications for Avian Botulism

Abstract

ABSTRACT:Since 1999, large-scale mortalities of fish-eating birds have been observed on the Great Lakes, and more specifically on Lake Erie. Type E botulism has been established as the primary cause of death. The mechanism of type E botulism exposure in fish-eating birds is unclear. Given that these birds are thought to eat live fish exclusively, it seems likely that their prey play a key role in the process, but the role of fish as potential transport vectors of botulinum neurotoxin type E (BoNT/E) to birds has not been adequately investigated. Between June 2003 and April 2004 a methodological model for exposing fish to Clostridium botulinum was developed and used to compare the sensitivity of rainbow trout (Oncorhynchus mykiss), round goby (Neogobius melanostomas), walleye (Stizostedion vitreum), and yellow perch (Perca flavescens) to four doses (0, 800, 1,500, and 4,000 Mouse Lethal Doses) of Clostridium botulinum type E neurotoxin. Each fish species expressed unique changes in both behavior and skin pigmentation prior to death. Yellow perch survived significantly longer (P,0.05) than the three other species at all toxin treatments. Results of this study suggest that live fish can represent a significant vector for transfer of BoNT/E to birds.

Persistence of Clostridium botulinum Neurotoxin Type E in Tissues from Selected Freshwater Fish Species: Implications to Public Health

“…Because many fish in our study were alive, even when harboring free toxin (i.e., in the positive BoNT/E nonfillet samples), our results suggest that similarly affected wild fish could represent a vector for BoNT/E transfer to fish-eating birds in nature. Other work in our lab (14,15) has confirmed that fish can survive for prolonged periods, even after consuming relatively high-and ultimately lethal-doses of toxin. The present study verifies that at least some of this toxin can be present as free toxin in affected fish, either during the living morbidity phase or after death.…”

“…The majority of fish expressed clinical signs that included equilibrium loss, pigmentation change, respiratory distress, and erratic swimming. A description of the onset of clinical signs and the number of fish expressing clinical signs is outlined in Yule et al (14). After death (as a result of BoNT/E intoxication, or, in the case of fish surviving to 10 days, by an overdose of tricaine methanesulfate MS-222), experimental fish were immediately double bagged and frozen at Ϫ20ЊC in a conventional freezer.…”

“…Since 1999, large-scale type E botulism epizootics have occurred in fish-eating birds on the Great Lakes, primarily Lake Erie. What is unique about these outbreaks is that the avian species mainly involved are known to consume only live fish, and it is hypothesized that the live fish are vectoring the toxin from its point of origin (most likely present as preformed free toxin in the food items eaten by these fish, such as in other smaller fish, invertebrates, sediment, or decaying organic material) to the birds (14,15). To fully understand the potential risk of consuming fish caught during type E botulism epizootics, and if the fish are vectoring toxin to the birds, it is necessary to determine if free BoNT/E is present in fish that have been exposed to BoNT/E.…”

Detection of Botulinum Type E Toxin in Channel Catfish with Visceral Toxicosis Syndrome Using Catfish Bioassay and Endopep Mass Spectrometry

“…This method can detect BoNT at levels comparable with or lower than levels detected with mouse bioassays. 1,2,[15][16][17] The use of fish bioassays to establish LD 50 s and sensitivities for botulinum has been described, 6,25,26 but no fish neutralization bioassays have been reported. This manuscript reports a catfish neutralization bioassay confirmed by Endopep-MS to link botulinum in the syndrome of VTC.…”

Biodiversity of Clostridium botulinum Type E Associated with a Large Outbreak of Botulism in Wildlife from Lake Erie and Lake Ontario

“…The round goby is a benthic fish that feeds on benthic organisms, including filter-feeding bivalves (8,10,21), and would therefore be exposed to bacteria, such as C. botulinum type E, that are found in lake sediments. One study (37) on round gobies that were experimentally intoxicated with type E botulinum toxin found that the fish exhibited pigmentation changes and displayed erratic swimming behavior. A reasonable hypothesis is that such changes make intoxicated fish easier prey for a piscivorous bird.…”