Improving understanding of a threatening toxin in Pacific fish

RNZ News

23-05-2025

Ciguatera is a seafood illness that's prevalent in all tropical and subtropical regions of the world, Dr Kirsty Smith says.
Photo:
123RF
Experts meeting at Nelson's Cawthron Institute this week hope to help the Pacific better handle the impact and threat of ciguatera poisoning.
Ciguatera, which is primarily contracted from reef fish, is considered a growing threat to food security, livelihoods, and public health in the region.
Cawthron Institute's Dr Kirsty Smith, an expert in molecular and algal ecology, told RNZ Pacific that identifying the source of ciguatera poisoning is difficult, but with better longterm data collection this can be improved.
(This transcript has been edited for brevity and clarity.)
Dr Kirsty Smith:
Ciguatera is a seafood illness that's prevalent in all tropical and subtropical regions of the world, and it's caused by the accumulation of toxins into fish species. So the toxins actually come from tiny, microscopic, micro algae that are then eaten by the fish species, and then toxins from the algae will accumulate in the fish. And then when humans eat the fish, they can get really sick from those toxins.
Don Wiseman: How sick can they get?
KS:
It can vary. The symptoms vary quite a lot, from kind of gastrointestinal illness right through to more neurological symptoms, where a common symptom is a reversal of the feeling of hot and cold, for example. That's quite a common symptom. Things that are usually hot feel cold and vice versa, and then right through to kind of more respiratory distress, and potentially can be fatal. If you receive a large dose, or you receive quite a few doses over your lifetime, then eventually they can become much worse over time, and eventually can lead to death, unfortunately.
DW: The presence of this ciguatera, or this cigatoxin, it's not apparent when you're in the process of preparing fish?
KS:
No, that's right, it doesn't seem to affect the fish at all themselves. You can't observe any differences between a non-toxic and a toxic fish just by looking at them. It's actually really, really difficult, and that's what makes it so much of a concern is that it's not very easy to diagnose a toxic fish.
Even in the laboratory setting or a testing laboratory setting, the method for detecting these toxins are really complicated and hard to do.
Cawthron Institute's Dr Kirsty Smith is an expert in molecular and algal ecology.
Photo:
Supplied / Cawthron Institute
DW: As far as the Pacific goes, it's a significant threat, isn't it, because the fish that get the ciguatira tend to be reef fish, and most Pacific Island countries have substantial reefs, don't they?
KS:
That's right, all Pacific countries really depend on their reef ecosystems for a food source. It's really important.
What makes it so sad is that the fish that are in the reef systems often do accumulate these toxins to quite high levels, but people can't really avoid eating fish, so they often will get sick numerous times in their lifetime.
They can't really avoid it because it's a fact of life that you're going to need to fish for your families and provide food for your family, so that makes it particularly heartbreaking.
The Pacific also has some of the highest rates of ciguatera in the world. About 80% of all cases come from the Pacific region. It's a really significant issue here.
DW: At the Cawthorn Institute this past week, you've had people from right across the Pacific looking at this issue and looking at, I suppose, what they do in their various countries, but also how they can improve the way in which they go about dealing with ciguatera.
KS:
That's right. We were hoping to bring together people from across the Pacific so we could all share our knowledge together and learn from each other, as well as kind of identifying what the biggest knowledge gaps are and where we should focus our efforts in the near future.
Whether that's helping provide training to different countries or developing new test methods or learning more about how people are sampling and testing in their countries.
It's been really, really valuable, and I think we've created a really strong network and relationships amongst the group.
Hopefully that will continue into the future, and we'll be able to work together to help solve some of these big knowledge gaps that exist with this illness.
DW: So you've been talking about these various things that people can do and the knowledge gaps and so on. So just how beneficial has it been?
KS:
It's been extremely beneficial because, we as scientists, I think it's important for us to learn from people in the community who are really experiencing the issues.
It's really important for us as scientists to hear from people in the community really impacted from this illness, and to really focus on the things that are going to make the most impact for them as well. Increasing our methods for detection and monitoring, are our high priority moving forward.
DW: I guess your detection is always going to be after the fact, isn't it? You're going to be detecting once someone has got the poison or not.
KS:
That's right. In the past, a lot of the monitoring has been reactive - when there's been outbreaks, then that will trigger monitoring and sampling to happen. But I think, after listening to everyone today, that we want to try and set up more longterm data gathering projects so that we can start coming up with indicators of outbreaks. So when we think outbreaks might be more common, we can set up more warning systems for people to prevent consuming fish at those more dangerous times.
If we can become more predictive around when we might think ciguatera will occur it will be really beneficial for communities.