When I first began the search for my microbe of the week, I decided to ask my Dad for some suggestions. He is a Fisheries Biologist for the Missouri Department of Conservation. For that reason I thought he might know about a bacterium that Dr. Westenberg does not. After a little bit of searching we decided upon Yersinia ruckeri.
Yersinia ruckeri is a gram-negative, rod shaped bacterial pathogen. It is a member of the Kingdom Eubacteria and in the same genus as the causative agent of the bubonic plaque. Most have a flagellum used for mobility. They contain no spores or capsules. It was discovered in the 1950’s in Idaho by Rucker, although it is unknown whether that is where it originated. It can now be found all around the world in areas such as the US, Europe, Canada, and South Africa among others.
Yersinia ruckeri is the causative agent of Enteric Redmouth (ERM) disease, found in salmonids, mainly rainbow trout. It is also know as Yersiniosis. It gets the name Redmouth from the reddening of the mouth. Other symptoms are: fish will stop eating and may isolate themselves, the fish become darker and their fins become inflamed, and the eyes become exophthalmic and may burst. The bacteria infect most tissues of the body, mainly well-vascularized areas, and can cause hemorrhaging. This can cause internal organs, such as the spleen, to also redden. ERM is spread from direct contact with contaminated fish or their feces.
Yersinia ruckeri can be detected in infected salmonids using fluorescent antibody tests and monoclonal ELISA assays. The following characteristics can also be observed; they are cytochrome oxidase negative, the produce acid not gas in glucose, and they react positively with ornithinc and lysine decarboxylase.
Because there are six different serotypes a vaccine has been difficult to develop. However, one has been developed by a company called AquaHealth, though it must be administered carefully. The temperature must be between 60 and 65 degrees Fahrenheit to shorten the days to maximum protection. For a longer duration of protection the fish must be vaccinated at a larger size. Also the fish must be exposed to a maximum quantity of the vaccine.
These small microbes can cause big dollar losses due to the loss of marketable fish with ERM. I just hope they cause a big grade.
Bibliography:
1. Peptidases of Yersinia ruckeri. http://merops.sanger.ac.uk/speccards/SPOO2134.htm. Accessed January 30, 2003.
2. Description of Yersinia ruckeri. http://hmsc.oregonstate.edu/classes/MB492/ERMdesiree/red.html. Accessed January 18, 2003.
3. Enteric Redmouth (ERM) Vaccination. http://www.ces.ncsu.edu/copubs/ag/aqua/trout/o14/. Accessed January 18, 2003.
4. Piper, et al. Fish Hatchery Management. Washington, D.C.: Fish and Wildlife Service. 1982, p.517.*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.
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