Viruses, wildfowl, ice and the ‘African Sea’
If fish farmers want to look into the near future to prevent the next ‘big issue’, they could do well to keep an eye on the work of Angela McLean, Professor of Mathematical Biology at Oxford University and co-director of the Institute for Emerging Infections.
She and her colleagues were displaying their work, on the emergence and mutation of HIV viruses across the planet, at the Royal Society Summer Science Fair (RSSF) in London. WF asked her whether their work could throw any light on viral haemorrhagic and white spot diseases which have been a curse for fish farmers. The white spot problem has not been made any easier with the banning of the use of malachite green for treatment, because of the malachite green’s carcinogenic properties.
Prof McLean said she was fascinated by the question, and her response was that the fish industry needs to look at the broader front and the issue of crossover transmissions of animal viruses to humans. Her research work includes HIV, flu viruses and scrapie, the latter being a form of “mad cow” disease (bovine spongiform encephalopathy caused by the prion protein) but in sheep.
The bottom line, as WF sees it, is how you protect your stock from diseases which affect different species (eg fish and wildfowl) which coexist in a common environment or pool. At its simplest, if you use feed which has been contaminated by an animal or human virus and that virus can learn to cross over and survive in a new host then you might possibly set up a series of infections through the food chain.
Viruses have great potential to mutate fast. So making sure the potential transmission or crossover points are minimised to deprive viruses or bacteria or certain proteins (as in the case of BSE) of an onward route, is a clear benchmark to be maintained when setting up and operating either cage or pond farms.
McLean said that eventually “all flu comes from waterfowl”. The fact that at the moment bird flu viruses, which end up in the water when infected fowl defecate, does not mean that the viruses cross over to the fish.
Perhaps one reason, she said, is that the flu virus attacks the respiratory tract (remember the outbreak of SARS – Severe Acute Respiratory Syndrome) and fish do not have lungs, and the gills are of a different tissue type.
But rather than waiting for something to happen, planned prevention should be to reduce the possibility of a virus jumping over the species barrier, whether to another animal or a human.
One should also always keep a close eye, and demand to know, feed composition and origin. The other potential ‘breeding’ ground for mutation could also be accumulations of faecal waste below farmed stock.
In terms of dangerous prion proteins getting into the fish food chain, Italian studies (www.biomedcentral.com) have tackled the issue of whether humans could get them by consuming fish which historically had been fed with mammalian meat and bone meal (MBM).
High doses of mouse-adapted scrapie prions (139A) were fed to farmed rainbow trout and turbot, and they took tissues from that fish to try to infect other mice.
They found this did not appear to cause the ‘mad’ symptoms of spongiform encephalopathy in fish or mice, although there were some brain lesions in a few of the mice. They said “scrapie 139A, and possibly BSE, is quickly removed from fish tissues despite evidence of a prion like protein in fish and of a specific binding of PrPSc [scrapie prions] to the mucosal side of fish intestine”.
Prion-caused disease can take years to emerge, so the researchers only say: “With all the cautions due to the difference between the 139A and the BSE strains, and that in this experiment fishes were observed for no more than 90 days after infection, it is tentatively possible to assume that the consumption of fish fed with BSE-infected MBM should not pose any substantial threat to public health”.
So, WF would say: “Never say never!” and certainly McLean suggested that the aquaculture industry should not let down its guard. She was quite clear that if there is poor management in the fish farming sector, bearing in mind the history of disease ravaging the industry in various countries, the potential is there for something to go seriously wrong.
Ice worries skippers fishing towards the Poles. Readers will remember the Greenland company run by two Inuit friends. Their crews cope with ice and bergs all the time, and they had two of the world’s most advanced ice trawlers in their 15-strong fleet.
The good news is that Cryosat-2 launched in April, using radar, is telling us down to a centimetre the thickness of ice and its volume around Antarctica and Greenland, and it is particularly good where marine ice meets calving icebergs, for example at Ilulissat.
The 1,400 scientists and experts at the Living Planet conference were told its orbit is covering 4.6 million sq km (bigger than the EU) more than earlier satellites.
The European Space Agency (ESA) which runs Cryosat-2 has also signed an agreement with the European Maritime Safety Agency to make more satellite data available to enhance maritime safety and monitor pollution from shipping.
It is official: parts of Africa are splitting apart and the seas will pour in and create a new ‘African Sea’.
Seven universities, who exhibited at the RSSF, have been monitoring underground tectonic shifts and volcanic eruptions, spurred on by a 60km-long segment of plate boundary which cracked open up to eight metres wide over 10 days in 2005 in Ethiopia’s Afar desert.
The cracking has continued sporadically ever since, but the average seems at least one metre per year.
Apparently the Red Sea was created like this. But don’t start thinking applying for quota licences yet. It could take 10 million years to fill up!
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