
Hi everyone,
I've been testing the microbiomes of saltwater aquariums for about a year now, and one interesting thing I've noticed is that a reasonable fraction of reef tanks have one or more known fish pathogens. But they're not everywhere. I'm starting this thread to share these data with you, and discuss the possibility that undiagnosed bacterial infections may contribute to fish diseases and mortality in our aquariums.
The bacterial pathogens I have seen so far:
A few important caveats about these findings:
One finding I'd like to highlight is the wide range of abundance we see for some of these. For example, consider Vibrio fortis. This bacterium is present in over half the tanks I've tested, but typically at very low levels (median = 0.16% of the community). However, in one tank it made up 19% of the community, more than 100-fold higher in relative abundance than the median level. It seems plausible that this extreme variation could play a role in the extent of disease caused by these bacteria.
Another important factor to consider is resistance. Taking P. damselae as an example, research has shown that fish can become more resistant to this pathogen with age, and some fish show genetic advantages in resistance. So it is possible that fish in the tank are not affected, even if their species generally is susceptible.
My questions for the community:
1. Have you experienced fish diseases or deaths that you believe were primarily caused by bacterial infections?
2. What are your practices for managing bacterial pathogens in your tanks?
Thanks for reading, I'll be curious to hear your thoughts.
I've been testing the microbiomes of saltwater aquariums for about a year now, and one interesting thing I've noticed is that a reasonable fraction of reef tanks have one or more known fish pathogens. But they're not everywhere. I'm starting this thread to share these data with you, and discuss the possibility that undiagnosed bacterial infections may contribute to fish diseases and mortality in our aquariums.
The bacterial pathogens I have seen so far:
Pathogen | Prevalence (% of tanks) | Abundance, % of community median (range) | Disease (reference) | Known Susceptible Fish |
---|---|---|---|---|
Photobacterium damselae | 14% | 0.19% (0 - 1.3%) | Photobacteriosis and similar infections (Rivas et al. 2013, Andreoni & Magnani 2014) | Damsel family, others? |
Piscirickettsia salmonis | 1% | 0% (0 - 0.13%) | Piscirickettsiosis (Rozas & Enrique 2014) | Salmonids, others? |
Vibrio fortis | 57% | 0.16% (0 - 19%) | Enteritis (Wang et al 2016) | Seahorses, others? |
A few important caveats about these findings:
- Genetic Variation - there is a lot of variation within each bacterial species in terms of virulence. For example, in P. damselae there are different sub-species and types with known differences in virulence and host ranges. However, the marker used here can't resolve these beyond the species level. Still, since so many of the sub species and types in this group are pathogens for fish or humans, I feel comfortable listing it as a pathogen.
- Unknown Susceptibilities - these pathogens are typically discovered in aquaculture settings, where a single species is grown. As a result, the researchers don't immediately document the range of susceptible fish in the aquarium trade, so we lack this information for most of these pathogens.
One finding I'd like to highlight is the wide range of abundance we see for some of these. For example, consider Vibrio fortis. This bacterium is present in over half the tanks I've tested, but typically at very low levels (median = 0.16% of the community). However, in one tank it made up 19% of the community, more than 100-fold higher in relative abundance than the median level. It seems plausible that this extreme variation could play a role in the extent of disease caused by these bacteria.
Another important factor to consider is resistance. Taking P. damselae as an example, research has shown that fish can become more resistant to this pathogen with age, and some fish show genetic advantages in resistance. So it is possible that fish in the tank are not affected, even if their species generally is susceptible.
My questions for the community:
1. Have you experienced fish diseases or deaths that you believe were primarily caused by bacterial infections?
2. What are your practices for managing bacterial pathogens in your tanks?
Thanks for reading, I'll be curious to hear your thoughts.
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