WEBVTT 00:00:00.000 --> 00:00:03.560 Okay, so let's unpack this. We're looking at 00:00:03.560 --> 00:00:06.820 a microscopic entity today. One that basically 00:00:06.820 --> 00:00:09.679 has the capacity to completely dismantle multi 00:00:09.679 --> 00:00:12.099 -million dollar global industries from the inside 00:00:12.099 --> 00:00:14.900 out. It really does. It's this hidden biological 00:00:14.900 --> 00:00:16.899 crisis taking place right beneath the surface 00:00:16.899 --> 00:00:19.899 of the water. So today's deep dive focuses on 00:00:19.899 --> 00:00:23.480 the infectious salmon anemia virus. ISAV. Right, 00:00:23.500 --> 00:00:25.859 widely known in scientific and aquaculture circles 00:00:25.859 --> 00:00:29.559 as ISAV. And this deep dive is tailored specifically 00:00:29.559 --> 00:00:31.660 for you, the listener. We know you're looking 00:00:31.660 --> 00:00:33.859 to synthesize complex systems without getting 00:00:33.859 --> 00:00:35.939 bogged down in all the dense jargon. Exactly. 00:00:36.100 --> 00:00:38.219 So we've pulled together the comprehensive data 00:00:38.219 --> 00:00:41.560 on ISAV to explore, well, not just what it is, 00:00:41.579 --> 00:00:44.539 but its taxonomic structure, its internal mechanics 00:00:44.539 --> 00:00:47.560 within the host, its oceanic spread. and its 00:00:47.560 --> 00:00:50.460 deep, deep ties to our global food supply. And 00:00:50.460 --> 00:00:52.060 I think it's important to establish right up 00:00:52.060 --> 00:00:54.840 front that the stakes surrounding this pathogen, 00:00:55.299 --> 00:00:57.520 they're difficult to overstate. Yeah. There's 00:00:57.520 --> 00:00:59.840 not just some localized agricultural nuisance. 00:01:00.520 --> 00:01:02.859 ISAV has been a world organization for animal 00:01:02.859 --> 00:01:06.560 health notifiable disease since 1990. Wow, 1990. 00:01:06.719 --> 00:01:08.540 So they've been tracking this globally for a 00:01:08.540 --> 00:01:11.120 long time. Absolutely. When an outbreak occurs, 00:01:11.640 --> 00:01:13.579 international regulatory bodies are immediately 00:01:13.579 --> 00:01:16.159 alerted. In the European Union, it's classified 00:01:16.159 --> 00:01:19.459 under extremely stringent regulations, monitored 00:01:19.459 --> 00:01:22.459 heavily by the European Community Reference Laboratory 00:01:22.459 --> 00:01:25.299 for Fish Diseases. So it's a massive deal. It 00:01:25.299 --> 00:01:27.879 is, because studying ISF -V isn't just an exercise 00:01:27.879 --> 00:01:31.379 in virology. It forces us to look at the profound 00:01:31.379 --> 00:01:35.640 economic, biological, and ecological interconnectedness 00:01:35.640 --> 00:01:38.000 of our world. It highlights the sheer fragility 00:01:38.000 --> 00:01:40.140 of the systems we've built to feed... billions 00:01:40.140 --> 00:01:42.719 of people. Exactly. So to understand how a system 00:01:42.719 --> 00:01:44.799 like that breaks down, we really need to start 00:01:44.799 --> 00:01:47.560 at the molecular level. Let's look at the taxonomy 00:01:47.560 --> 00:01:50.680 of this virus because it occupies a very specific, 00:01:50.859 --> 00:01:53.519 almost solitary space in the viral family tree. 00:01:53.760 --> 00:01:57.200 It does. Taxonomically, ISAV is a segmented RNA 00:01:57.200 --> 00:02:00.379 virus. A segmented RNA virus. Right. Now being 00:02:00.379 --> 00:02:03.180 a segmented RNA virus is crucial to its evolutionary 00:02:03.180 --> 00:02:05.790 potential. It means the viral genome isn't just 00:02:05.790 --> 00:02:08.710 one long continuous strand. It's broken up into 00:02:08.710 --> 00:02:11.250 distinct separate pieces. Kind of like chapters 00:02:11.250 --> 00:02:13.569 in a book rather than one long skull. That's 00:02:13.569 --> 00:02:16.069 a good way to put it. But what makes Isav truly 00:02:16.069 --> 00:02:19.729 unique is that it is the absolute only species 00:02:19.729 --> 00:02:22.550 in the genus Isavirus. The only one. The only 00:02:22.550 --> 00:02:24.949 one. It sits entirely alone in that specific 00:02:24.949 --> 00:02:26.979 classification. But, and here's where it gets 00:02:26.979 --> 00:02:31.000 wild. It belongs to a much broader and frankly 00:02:31.000 --> 00:02:34.400 much more infamous family, the Orthomixaviridae 00:02:34.400 --> 00:02:36.780 family. Yes. And for anyone familiar with human 00:02:36.780 --> 00:02:39.259 virology, that family name carries a whole lot 00:02:39.259 --> 00:02:41.580 of weight. It really does. Because it means ISAV 00:02:41.580 --> 00:02:44.539 is fundamentally related to the influenza viruses. 00:02:44.680 --> 00:02:47.919 It is essentially an aquatic flu. It shares a 00:02:47.919 --> 00:02:50.259 distinct structural and functional lineage with 00:02:50.259 --> 00:02:53.360 influenza, yes. And much like influenza, that 00:02:53.360 --> 00:02:55.819 segmented genome we mentioned provides a massive 00:02:55.819 --> 00:02:57.780 evolutionary advantage because of how it can 00:02:57.780 --> 00:03:00.560 mix and match exactly if two different strains 00:03:00.560 --> 00:03:02.879 of the segmented virus happen to infect the same 00:03:02.879 --> 00:03:05.599 host cell simultaneously they can shuffle their 00:03:05.599 --> 00:03:07.900 genetic deck right they swap entire segments 00:03:07.900 --> 00:03:10.439 of their genome in a process called reassortment 00:03:10.439 --> 00:03:12.939 reassortment and that's dangerous because because 00:03:12.939 --> 00:03:15.699 this can lead to the sudden emergence of a completely 00:03:15.699 --> 00:03:19.639 novel highly pathogenic hybrid strain almost 00:03:19.639 --> 00:03:22.960 overnight just bypassing the slower process of 00:03:22.960 --> 00:03:25.500 standard mutation entirely. Precisely. And that 00:03:25.500 --> 00:03:28.259 rapid shifting is exactly why flu viruses in 00:03:28.259 --> 00:03:30.960 humans require constant vaccine updates, right? 00:03:31.060 --> 00:03:33.639 That's the exact same mechanism. And genetically, 00:03:34.020 --> 00:03:36.580 IS baby is highly adapted. We are looking at 00:03:36.580 --> 00:03:39.620 a genome that encodes at least 10 distinct proteins. 00:03:39.680 --> 00:03:41.639 Right, which might not sound like a lot to us. 00:03:42.120 --> 00:03:44.780 But in the viral world, 10 proteins represent 00:03:44.780 --> 00:03:47.699 a highly sophisticated toolkit. It's built for 00:03:47.699 --> 00:03:50.240 hijacking host cellular machinery and evading 00:03:50.240 --> 00:03:52.919 immune responses. It is. And how it utilizes 00:03:52.919 --> 00:03:55.879 that toolkit leads us to a fundamental biological 00:03:55.879 --> 00:03:58.759 difference between aquatic and terrestrial vertebrates. 00:03:58.979 --> 00:04:01.000 This is the part that blew my mind in the research. 00:04:01.080 --> 00:04:04.520 It's fascinating. So to replicate, a virus needs 00:04:04.520 --> 00:04:06.699 access to a cell's transcriptional machinery. 00:04:07.020 --> 00:04:09.379 The genetic factory, so to speak. Right. In humans 00:04:09.379 --> 00:04:13.300 and most mammals. mature red blood cells or erythrocytes 00:04:13.300 --> 00:04:15.719 are enucleated. Meaning they don't have a nucleus? 00:04:16.079 --> 00:04:18.920 Exactly. They shed their nucleus and their DNA 00:04:18.920 --> 00:04:22.720 during maturation to maximize the space available 00:04:22.720 --> 00:04:24.839 for hemoglobin. Because their whole job is just 00:04:24.839 --> 00:04:27.639 to carry oxygen. Exactly. Making them highly 00:04:27.639 --> 00:04:29.949 efficient at transporting oxygen. Which means 00:04:29.949 --> 00:04:33.129 human red blood cells are essentially evolutionary 00:04:33.129 --> 00:04:35.889 dead ends for a virus looking to replicate. There's 00:04:35.889 --> 00:04:38.569 no DNA factory inside them to hijack. Not at 00:04:38.569 --> 00:04:41.290 all. But here is the biological quirk that makes 00:04:41.290 --> 00:04:44.870 salmon so incredibly vulnerable. Teleostphish, 00:04:45.029 --> 00:04:47.790 which includes Atlantic salmon, retain the nucleus 00:04:47.790 --> 00:04:50.730 in their mature red blood cells. Yes. Their oxygen 00:04:50.730 --> 00:04:53.810 carrying cells still contain DNA. And that retention 00:04:53.810 --> 00:04:56.350 changes the entire dynamic of the viral infection. 00:04:56.800 --> 00:04:59.819 The red blood cells at the salmon are not just 00:04:59.819 --> 00:05:03.199 vehicles for oxygen anymore. They remain viable, 00:05:03.639 --> 00:05:07.449 active targets for viral replication. ISIVs evolved 00:05:07.449 --> 00:05:09.930 to exploit this specific physiological trait. 00:05:09.990 --> 00:05:12.269 It's so efficient. Extremely. It doesn't have 00:05:12.269 --> 00:05:14.870 to navigate deep into complex organ tissues immediately. 00:05:15.170 --> 00:05:17.629 It can directly infect the erythrocytes circulating 00:05:17.629 --> 00:05:20.290 continuously throughout the entire vascular system 00:05:20.290 --> 00:05:22.750 of the fish. So it sets up its replication factories 00:05:22.750 --> 00:05:24.769 right inside the very cells required to keep 00:05:24.769 --> 00:05:27.189 the fish oxygenated. Exactly. But the literature 00:05:27.189 --> 00:05:30.430 points out that ISIV isn't a monolith. The research 00:05:30.430 --> 00:05:33.610 broadly categorizes the virus into two main distinct 00:05:33.610 --> 00:05:36.560 strains. A European strain and a North American 00:05:36.560 --> 00:05:39.699 strain. And within those, the virulence varies 00:05:39.699 --> 00:05:43.300 wildly. Some are highly pathogenic, causing catastrophic 00:05:43.300 --> 00:05:46.300 disease, while others circulate without causing 00:05:46.300 --> 00:05:48.839 apparent harm. The variation in pathogenicity 00:05:48.839 --> 00:05:51.420 is often linked to specific mutations in those 00:05:51.420 --> 00:05:53.360 viral proteins you mentioned earlier. The 10 00:05:53.360 --> 00:05:56.360 proteins. Yes. Some strains might bind more efficiently 00:05:56.360 --> 00:05:59.660 to the host cells, or replicate faster, or trigger 00:05:59.660 --> 00:06:03.050 a more severe immune overreaction. When a highly 00:06:03.050 --> 00:06:06.069 pathogenic strain of ISAVI takes hold in a population 00:06:06.069 --> 00:06:08.930 of Atlantic salmon, the physiological cascade 00:06:08.930 --> 00:06:11.949 is rapid and devastating. Let's track that cascade, 00:06:12.089 --> 00:06:14.550 because when we look at the pathology of an infected 00:06:14.550 --> 00:06:18.029 Atlantic salmoseller, the primary result of this 00:06:18.029 --> 00:06:20.810 erythrocyte infection is severe anemia. And since 00:06:20.810 --> 00:06:23.310 you, our listener, are well -versed in the mechanics 00:06:23.310 --> 00:06:26.410 of disease, we know anemia involves a critical 00:06:26.410 --> 00:06:29.629 drop in functional red blood cells. But the physical 00:06:29.629 --> 00:06:32.069 manifestation of this in the water is really 00:06:32.069 --> 00:06:34.790 alarming. The clinical signs are a direct reflection 00:06:34.790 --> 00:06:37.850 of hypoxia. Oxygen starvation at the tissue level. 00:06:38.110 --> 00:06:41.310 Exactly. Because the virus is causing the destruction 00:06:41.310 --> 00:06:44.949 of the red blood cells, the fish develop exceptionally 00:06:44.949 --> 00:06:48.750 pale gills. They lose that healthy rich red coloration. 00:06:48.910 --> 00:06:51.990 They do. And you will often observe infected 00:06:51.990 --> 00:06:54.389 fish swimming abnormally close to the surface, 00:06:54.829 --> 00:06:58.579 literally gasping or gulping air. Just a futile 00:06:58.579 --> 00:07:02.100 attempt to oxygenate a failing vascular system. 00:07:02.120 --> 00:07:04.519 It is. And while that is happening on the surface, 00:07:04.680 --> 00:07:07.120 the post -mortem findings detail systemic internal 00:07:07.120 --> 00:07:09.720 collapse. The organs responsible for filtering 00:07:09.720 --> 00:07:11.779 and managing blood, specifically the liver and 00:07:11.779 --> 00:07:14.920 the spleen, take massive damage. They become 00:07:14.920 --> 00:07:17.519 severely swollen, congested with fluids, and 00:07:17.519 --> 00:07:19.980 in the later stages of the disease, the tissue 00:07:19.980 --> 00:07:22.540 becomes fully necrotic. And that necrosis is 00:07:22.540 --> 00:07:25.160 a critical point. Dead tissue. Yes, the tissue 00:07:25.160 --> 00:07:29.000 is dying while the animal is still alive. Furthermore, 00:07:29.560 --> 00:07:33.259 ISAV heavily impacts the endothelial cells lining 00:07:33.259 --> 00:07:35.579 the blood vessels. So the pipes themselves are 00:07:35.579 --> 00:07:37.980 breaking down. That's a good analogy. This leads 00:07:37.980 --> 00:07:41.000 to vascular breakdown. The circulatory system 00:07:41.000 --> 00:07:43.490 begins to hemorrhage. You see a condition where 00:07:43.490 --> 00:07:45.449 the blood becomes contaminated with cellular 00:07:45.449 --> 00:07:47.810 debris. From the bursting red blood cells. Right. 00:07:47.949 --> 00:07:50.089 The surviving erythrocytes become incredibly 00:07:50.089 --> 00:07:53.189 fragile, prone to rapid lysis or bursting. So 00:07:53.189 --> 00:07:55.370 the fish's body tries to compensate, right? It 00:07:55.370 --> 00:07:58.750 does. The hematopoietic organs attempt to compensate 00:07:58.750 --> 00:08:01.509 by releasing immense numbers of immature red 00:08:01.509 --> 00:08:03.410 blood cells into the bloodstream. But it's just 00:08:03.410 --> 00:08:06.149 a losing battle against a highly pathogenic strain. 00:08:06.250 --> 00:08:08.730 It is a complete systemic breakdown. Yet, despite 00:08:08.730 --> 00:08:11.370 this massive internal trauma, one of the most 00:08:11.370 --> 00:08:14.089 terrifying aspects of ISAV for the aquaculture 00:08:14.089 --> 00:08:16.910 industry is its stealth capability. The stealth 00:08:16.910 --> 00:08:19.649 factor is huge. Right, a highly pathogenic strain 00:08:19.649 --> 00:08:22.490 doesn't always broadcast its presence, and infected 00:08:22.490 --> 00:08:25.589 fish might show absolutely zero external signs. 00:08:25.769 --> 00:08:28.449 None at all, initially. It could maintain a completely 00:08:28.449 --> 00:08:31.670 normal appetite, swimming and schooling naturally 00:08:31.670 --> 00:08:34.570 right up until the moment it suffers sudden mortality. 00:08:35.110 --> 00:08:37.909 And that asymptomatic progression is precisely 00:08:37.909 --> 00:08:40.909 why outbreaks can become so entrenched before 00:08:40.909 --> 00:08:42.929 they're even detected. Because everything looks 00:08:42.929 --> 00:08:45.759 fine. Exactly. A farm manager might be looking 00:08:45.759 --> 00:08:49.279 at a pen of seemingly healthy feeding fish, entirely 00:08:49.279 --> 00:08:52.220 unaware that the viral load in the water is climbing 00:08:52.220 --> 00:08:54.620 exponentially. And by the time the sudden mortalities 00:08:54.620 --> 00:08:57.259 begin, the pathogen has already disseminated 00:08:57.259 --> 00:09:00.379 throughout the local environment. Yes. When a 00:09:00.379 --> 00:09:03.220 highly virulent strain hits that critical threshold 00:09:03.220 --> 00:09:06.019 in a dense farming environment, the mortality 00:09:06.019 --> 00:09:10.320 rates can approach 100%. 100%. Which brings a 00:09:10.320 --> 00:09:13.500 massive ecological complication into focus. The 00:09:13.500 --> 00:09:15.840 Atlantic salmon is the primary victim here, but 00:09:15.840 --> 00:09:17.639 the sources highlight that they are not the only 00:09:17.639 --> 00:09:19.980 actors in this epidemiological web. No, they 00:09:19.980 --> 00:09:22.039 aren't. We have to look at the other species 00:09:22.039 --> 00:09:24.519 acting as reservoirs, what we might colloquially 00:09:24.519 --> 00:09:27.639 think of as asymptomatic carriers. The ecology 00:09:27.639 --> 00:09:30.399 of the virus extends well beyond somocellar. 00:09:30.899 --> 00:09:33.480 Research indicates that serine brown trout, or 00:09:33.480 --> 00:09:36.340 somotruda, as well as rainbow trout on Corynchus 00:09:36.340 --> 00:09:39.720 miciss, are highly susceptible to infection. 00:09:39.899 --> 00:09:42.220 But they have a crucial immunological difference, 00:09:42.460 --> 00:09:45.059 right? They do. They get infected, but they don't 00:09:45.059 --> 00:09:47.460 develop the disease. They don't suffer the severe 00:09:47.460 --> 00:09:50.759 anemia, the necrotic organs, or the massive die 00:09:50.759 --> 00:09:52.779 -offs that we see in Atlantic salmon. Exactly. 00:09:53.000 --> 00:09:56.179 They act as natural reservoirs. A reservoir species 00:09:56.179 --> 00:09:58.879 can harbor the pathogen, allow it to replicate, 00:09:59.399 --> 00:10:01.980 and continuously shed the virus into the surrounding 00:10:01.980 --> 00:10:04.279 aquatic environment without succumbing to the 00:10:04.279 --> 00:10:06.480 illness. They're essentially typhoid marys of 00:10:06.480 --> 00:10:09.500 the sea. That's a perfect comparison. This complicates 00:10:09.500 --> 00:10:12.139 disease management immensely because you have 00:10:12.139 --> 00:10:15.379 seemingly healthy wild populations acting as 00:10:15.379 --> 00:10:17.759 constant unseen vectors. And the research doesn't 00:10:17.759 --> 00:10:20.159 stop at brown and rainbow trout. It specifically 00:10:20.159 --> 00:10:22.500 points out that several species of Pacific salmon 00:10:22.320 --> 00:10:24.919 can also carry these highly pathogenic strains 00:10:24.919 --> 00:10:27.840 of ISAV. Yes, that is a major concern. They can 00:10:27.840 --> 00:10:30.159 harbor the absolute worst strains without displaying 00:10:30.159 --> 00:10:33.320 any ISAV -related symptoms. The interaction between 00:10:33.320 --> 00:10:37.000 ISAV and Pacific salmon is a subject of intense 00:10:37.000 --> 00:10:40.669 virological scrutiny right now. Currently, These 00:10:40.669 --> 00:10:43.570 specific species exhibit a high relative resistance 00:10:43.570 --> 00:10:46.370 to the disease. Why is that? Well, their cellular 00:10:46.370 --> 00:10:49.450 receptors or their innate immune responses manage 00:10:49.450 --> 00:10:52.269 to suppress the viral replication just enough 00:10:52.269 --> 00:10:55.629 to prevent systemic collapse. But the sources 00:10:55.629 --> 00:10:58.649 include a very explicit biological warning regarding 00:10:58.649 --> 00:11:01.470 that resistance. While Pacific salmon are currently 00:11:01.470 --> 00:11:04.710 asymptomatic carriers, the potential for ISAV 00:11:04.710 --> 00:11:07.809 to adapt to them is a documented reality. It 00:11:07.809 --> 00:11:10.250 is a fundamental principle of virology, particularly 00:11:10.250 --> 00:11:12.509 with segmented RNA viruses like this one. Because 00:11:12.509 --> 00:11:15.200 they mutate so fast. Exactly. When a pathogen 00:11:15.200 --> 00:11:17.100 is constantly circulating within a reservoir 00:11:17.100 --> 00:11:20.159 population, it is subjected to continuous evolutionary 00:11:20.159 --> 00:11:22.960 pressure. Every replication cycle is an opportunity 00:11:22.960 --> 00:11:25.320 for mutation. So it's just a numbers game. It 00:11:25.320 --> 00:11:27.879 is. The concern is that a genetic shift could 00:11:27.879 --> 00:11:30.039 suddenly allow the virus to bypass the Pacific 00:11:30.039 --> 00:11:32.000 salmon's natural resistance. And if that happens? 00:11:32.279 --> 00:11:35.179 If that adaptation occurs, we could witness an 00:11:35.179 --> 00:11:37.940 epidemiological catastrophe in the Pacific basin 00:11:37.940 --> 00:11:40.559 that mirrors the devastation already seen in 00:11:40.559 --> 00:11:42.799 the Atlantic. And to understand what that devastation 00:11:42.799 --> 00:11:45.679 actually looks like, we need to trace the historical 00:11:45.679 --> 00:11:48.940 epidemiology. We really need to map how this 00:11:48.940 --> 00:11:52.139 pathogen moved from a localized anomaly to a 00:11:52.139 --> 00:11:54.820 global crisis. The timeline is very revealing. 00:11:54.970 --> 00:11:57.370 The chronological tracking begins in the autumn 00:11:57.370 --> 00:12:01.629 of 1984. In 1984, the aquaculture industry in 00:12:01.629 --> 00:12:04.929 Norway was expanding rapidly. It was on the southwest 00:12:04.929 --> 00:12:07.889 coast that farm managers first observed an entirely 00:12:07.889 --> 00:12:11.230 novel, highly lethal disease sweeping through 00:12:11.230 --> 00:12:13.009 farmed Atlantic salmon. And they didn't know 00:12:13.009 --> 00:12:14.809 what it was at first. They didn't. It didn't 00:12:14.809 --> 00:12:16.629 behave like the bacterial infections they were 00:12:16.629 --> 00:12:18.809 used to managing. It caused mortalities of up 00:12:18.809 --> 00:12:21.190 to 80 percent in some of the affected hatcheries. 00:12:21.330 --> 00:12:24.139 80 percent. That is staggering. The severity 00:12:24.139 --> 00:12:27.100 of the die -offs forced a rapid regulatory response. 00:12:27.440 --> 00:12:30.580 By June of 1988, the Norwegian Ministry of Agriculture, 00:12:30.919 --> 00:12:33.580 Fisheries and Food officially classified it as 00:12:33.580 --> 00:12:36.419 a notifiable disease. A necessary step. But containing 00:12:36.419 --> 00:12:39.379 a marine pathogen is incredibly difficult, and 00:12:39.379 --> 00:12:41.360 the narrative quickly jumps across the Atlantic 00:12:41.360 --> 00:12:45.940 Ocean. In the summer of 1996, a severe disease 00:12:45.940 --> 00:12:48.840 suddenly begins ravaging Atlantic salmon farms 00:12:48.840 --> 00:12:51.159 in New Brunswick, Canada. The mortality rates 00:12:51.159 --> 00:12:54.139 in New Brunswick were staggering as well. And 00:12:54.139 --> 00:12:56.139 the veterinary community there was initially 00:12:56.139 --> 00:12:58.659 baffled. Because it looked different. Well, because 00:12:58.659 --> 00:13:02.200 telea fish utilize their kidneys as a primary 00:13:02.200 --> 00:13:05.340 hematopoietic organ, meaning it's heavily involved 00:13:05.340 --> 00:13:08.480 in blood cell production. The viral damage to 00:13:08.480 --> 00:13:11.200 the circulatory system presented strongly there. 00:13:11.220 --> 00:13:14.480 I see. So researchers initially labeled the outbreak 00:13:14.480 --> 00:13:17.220 hemorrhagic kidney syndrome. Entirely unaware 00:13:17.220 --> 00:13:19.820 of its true etiology. Right. They thought it 00:13:19.820 --> 00:13:21.960 was a new disease. It's a fascinating look at 00:13:21.960 --> 00:13:24.500 the scientific process. You have infectious salmon 00:13:24.500 --> 00:13:27.039 anemia in Norway and hemorrhagic kidney syndrome 00:13:27.039 --> 00:13:30.419 in Canada. They appear to be two geographically 00:13:30.419 --> 00:13:33.519 isolated distinct pathologies. But science eventually 00:13:33.519 --> 00:13:35.909 connected the dots. As international researchers 00:13:35.909 --> 00:13:38.070 began collaborating, sequencing the pathogens 00:13:38.070 --> 00:13:41.710 and comparing the histopathology, the truth emerged. 00:13:42.289 --> 00:13:45.169 They conclusively proved that the pathogen decimating 00:13:45.169 --> 00:13:48.750 the Canadian farms was the exact same virus that 00:13:48.750 --> 00:13:51.809 had emerged in Norway over a decade earlier. 00:13:52.090 --> 00:13:54.470 And that discovery fundamentally altered the 00:13:54.470 --> 00:13:57.049 global understanding of biosecurity in aquaculture. 00:13:57.419 --> 00:14:00.220 Because the ocean is huge. Exactly. It proved 00:14:00.220 --> 00:14:02.840 that vast oceanic distances were not a sufficient 00:14:02.840 --> 00:14:06.399 barrier. And the spread continued. In May of 00:14:06.399 --> 00:14:09.799 1998, the virus was identified in Scotland. Specifically 00:14:09.799 --> 00:14:12.200 at a salmon farm at Loch Nevis on the West Coast. 00:14:12.200 --> 00:14:14.779 Yes. And it aggressively expanded from that initial 00:14:14.779 --> 00:14:17.960 site. By the end of 1998, the outbreak had breached 00:14:17.960 --> 00:14:20.779 containment and spread to 15 separate farming 00:14:20.779 --> 00:14:23.120 operations, extending outward to the islands 00:14:23.120 --> 00:14:25.620 of Skye and Shetland. and the Shetland region 00:14:25.620 --> 00:14:28.460 experienced a resurgence a decade later, in 2008. 00:14:28.779 --> 00:14:31.259 That 2008 Shetland incident is notable for the 00:14:31.259 --> 00:14:33.799 regulatory response, isn't it? It is. The virus 00:14:33.799 --> 00:14:36.809 was detected in fish at a single site. Even though 00:14:36.809 --> 00:14:38.909 there was no immediate evidence of transmission 00:14:38.909 --> 00:14:41.490 beyond that specific location, the authorities 00:14:41.490 --> 00:14:44.309 ordered the complete preemptive emptying of two 00:14:44.309 --> 00:14:47.149 nearby cages belonging to Scottish sea farms. 00:14:47.389 --> 00:14:49.710 Just preemptively wiping them out. Right. It 00:14:49.710 --> 00:14:52.330 demonstrates a shift toward highly aggressive 00:14:52.330 --> 00:14:54.990 preemptive culling to break the chain of transmission. 00:14:55.289 --> 00:14:56.690 Because they knew what was coming if they didn't. 00:14:56.929 --> 00:14:59.090 Exactly. But if we really want to examine the 00:14:59.090 --> 00:15:01.809 ultimate worst case scenario of an ISFV outbreak, 00:15:02.269 --> 00:15:05.250 we have to analyze the Chilean collapse. The 00:15:05.250 --> 00:15:07.889 sources note that Iosevi was actually first isolated 00:15:07.889 --> 00:15:11.230 from a farm in Chile back in the 1990s and formally 00:15:11.230 --> 00:15:14.769 described in the literature in 2001, but it remained 00:15:14.769 --> 00:15:17.230 relatively quiet for years. Because the mere 00:15:17.230 --> 00:15:19.490 presence of a pathogen does not guarantee an 00:15:19.490 --> 00:15:22.830 epidemic. Environmental conditions, host density, 00:15:23.269 --> 00:15:25.730 and viral strain variations all play a role. 00:15:25.830 --> 00:15:29.350 It's a complex formula. It is. However, the ecological 00:15:29.350 --> 00:15:31.669 balance in Chile shifted catastrophically in 00:15:31.669 --> 00:15:35.320 June of 2007. The industry suffered a profound 00:15:35.320 --> 00:15:38.639 and rapid outbreak of highly pathogenic ISAV. 00:15:39.159 --> 00:15:41.980 It ignited at an Atlantic salmon facility in 00:15:41.980 --> 00:15:44.340 the Chilliway Archipelago within the Los Lagos 00:15:44.340 --> 00:15:47.299 region. Yes. And from there, it didn't just spread, 00:15:47.480 --> 00:15:49.919 it cascaded southward through the complex network 00:15:49.919 --> 00:15:52.600 of fjords and channels into the Aisin region. 00:15:52.840 --> 00:15:55.759 To understand the impact of that 2007 Chilean 00:15:55.759 --> 00:15:58.299 epidemic, you really have to look beyond the 00:15:58.299 --> 00:16:01.440 biology and examine the socioeconomic dominoes. 00:16:01.480 --> 00:16:05.399 The human cost. Exactly. Chile had built a massive 00:16:05.399 --> 00:16:07.659 portion of its regional economy around salmon 00:16:07.659 --> 00:16:10.570 aquaculture. When the virus swept through, it 00:16:10.570 --> 00:16:13.029 didn't just kill fish, it forced the permanent 00:16:13.029 --> 00:16:16.029 closure of numerous high -density farming operations. 00:16:16.309 --> 00:16:18.370 And the ripple effects of those closures were 00:16:18.370 --> 00:16:20.509 devastating. It wasn't just farm owners taking 00:16:20.509 --> 00:16:23.590 a financial hit, the entire supply chain collapsed. 00:16:23.889 --> 00:16:26.070 Everything from processing to transport. The 00:16:26.070 --> 00:16:28.149 processing plants lost their input, the transport 00:16:28.149 --> 00:16:30.549 networks lost their cargo, and the specialized 00:16:30.549 --> 00:16:32.789 feed manufacturers lost their primary buyers. 00:16:32.889 --> 00:16:36.269 This resulted in staggering rates of sudden localized 00:16:36.269 --> 00:16:38.799 human unemployment in regions that lacked diverse 00:16:38.799 --> 00:16:42.799 economic alternatives. It drastically altered 00:16:42.799 --> 00:16:46.000 the global supply of farmed salmon, driving up 00:16:46.000 --> 00:16:49.120 worldwide market prices and completely reshaping 00:16:49.120 --> 00:16:51.320 the geopolitical dominance of the industry. It 00:16:51.320 --> 00:16:54.159 is a stark reminder of how deeply human economies 00:16:54.159 --> 00:16:56.899 are tethered to biological stability. Absolutely. 00:16:57.360 --> 00:16:59.440 And North America continued to grapple with it 00:16:59.440 --> 00:17:02.840 as well. In 2011, there was significant anxiety 00:17:02.840 --> 00:17:05.980 in British Columbia when preliminary tests suggested 00:17:05.980 --> 00:17:08.420 the virus might be present in wild Pacific salmon. 00:17:08.700 --> 00:17:10.539 Though subsequent extensive culturing by the 00:17:10.569 --> 00:17:13.769 Canadian Food Inspection Agency, the CFIA failed 00:17:13.769 --> 00:17:16.369 to confirm viable virus at that time. Right, 00:17:16.390 --> 00:17:19.009 but 2012 proved to be a brutal year on the Atlantic 00:17:19.009 --> 00:17:22.029 coast. Nova Scotia confirmed an outbreak that 00:17:22.029 --> 00:17:25.450 led to the destruction of up to 750 ,000 salmon. 00:17:25.829 --> 00:17:28.289 And mere months later, Newfoundland and Labrador 00:17:28.289 --> 00:17:30.569 suffered an outbreak requiring the culling of 00:17:30.569 --> 00:17:33.869 450 ,000 fish. The sheer biomass involved in 00:17:33.869 --> 00:17:36.490 those calls over a million market -ready fish 00:17:36.490 --> 00:17:39.109 represents a logistical and financial nightmare. 00:17:39.789 --> 00:17:42.650 of that much infected biological material securely 00:17:42.650 --> 00:17:44.950 without further contaminating the environment 00:17:44.950 --> 00:17:47.329 is a massive undertaking. Which makes an event 00:17:47.329 --> 00:17:50.470 that occurred in mid -2012 in Nova Scotia so 00:17:50.470 --> 00:17:53.240 incredibly fascinating. The paradox. The Nova 00:17:53.240 --> 00:17:55.759 Scotia paradox, yeah. The source's detail and 00:17:55.759 --> 00:17:59.220 outbreak were 240 ,000 fish tested positive for 00:17:59.220 --> 00:18:02.660 the virus. But the CFIA did not order a call. 00:18:02.900 --> 00:18:05.740 They didn't? Instead, they allowed those infected 00:18:05.740 --> 00:18:08.559 fish to remain in the water, mature to full market 00:18:08.559 --> 00:18:11.640 size, and in early 2013, they were harvested, 00:18:12.119 --> 00:18:14.900 processed, and sold to the public for human consumption. 00:18:15.180 --> 00:18:17.900 On the surface, authorizing the sale of a quarter 00:18:17.900 --> 00:18:20.339 million virus -infected animals seems like a 00:18:20.339 --> 00:18:22.559 staggering regulatory failure. Or a massive public 00:18:22.559 --> 00:18:25.339 health gamble. Right. But the CFIA's decision 00:18:25.339 --> 00:18:28.809 was rooted in precise molecular virology. The 00:18:28.809 --> 00:18:32.589 tissue tropism of ISV, meaning the specific cells 00:18:32.589 --> 00:18:35.069 and receptors a virus has evolved to bind to, 00:18:35.410 --> 00:18:38.089 is entirely incompatible with human biology. 00:18:38.349 --> 00:18:40.549 The virus physically cannot unlock our cells. 00:18:40.690 --> 00:18:43.230 Exactly. We don't possess the necessary sialic 00:18:43.230 --> 00:18:46.130 acid receptor configurations, nor do our enucleated 00:18:46.130 --> 00:18:48.549 red blood cells offer the transcriptional machinery 00:18:48.549 --> 00:18:50.349 the virus requires. We covered that earlier, 00:18:50.509 --> 00:18:53.690 right? So, despite ISIV's taxonomic relationship 00:18:53.690 --> 00:18:57.230 to the human influenza virus, it poses zero threat 00:18:57.230 --> 00:19:00.460 to humans. human health. The CFIA held the fish, 00:19:00.839 --> 00:19:02.779 inspected them, and determined the flesh was 00:19:02.779 --> 00:19:05.440 safe. It highlights a crucial intersection of 00:19:05.440 --> 00:19:08.779 science and policy. Regulatory bodies have to 00:19:08.779 --> 00:19:11.619 balance catastrophic economic losses against 00:19:11.619 --> 00:19:14.200 actual biological risks. It's a tough call to 00:19:14.200 --> 00:19:17.240 make. But if the pathogen cannot leap the species 00:19:17.240 --> 00:19:20.059 barrier to humans, destroying viable protein 00:19:20.059 --> 00:19:22.980 out of an abundance of caution becomes economically 00:19:22.980 --> 00:19:25.680 indefensible. Makes sense. Yet the march of the 00:19:25.680 --> 00:19:28.140 virus into new territories hasn't stopped. By 00:19:28.140 --> 00:19:30.779 2016, the virus was finally and conclusively 00:19:30.779 --> 00:19:33.279 discovered in both farmed and wild salmon in 00:19:33.279 --> 00:19:35.359 British Columbia. Across the continent. This 00:19:35.359 --> 00:19:37.680 relentless spread forces us to ask, how is this 00:19:37.680 --> 00:19:40.839 pathogen navigating vast oceanic distances and 00:19:40.839 --> 00:19:43.400 breaching supposedly secure aquaculture facilities? 00:19:44.079 --> 00:19:45.960 We need to analyze the transmission mechanics 00:19:45.960 --> 00:19:48.240 and the vectors. The baseline transmission of 00:19:48.240 --> 00:19:51.039 ISAV occurs horizontally. Meaning from fish to 00:19:51.039 --> 00:19:55.089 fish. Yes. This involved direct, physical contact 00:19:55.089 --> 00:19:58.750 between a shedding, infected fish, and a naive, 00:19:59.009 --> 00:20:02.109 uninfected host. It also occurs through exposure 00:20:02.109 --> 00:20:04.750 to viral particles shed into the water column 00:20:04.750 --> 00:20:08.250 through mucus, feces, or the sheer decay of necrotic 00:20:08.250 --> 00:20:10.710 tissue. Fomite transmission is also a massive 00:20:10.710 --> 00:20:13.170 factor, right? Absolutely. Contaminated farming 00:20:13.170 --> 00:20:15.880 equipment, shared nets, or even the boots of 00:20:15.880 --> 00:20:18.099 personnel moving between pens without rigorous 00:20:18.099 --> 00:20:20.920 biosecurity protocols can easily introduce the 00:20:20.920 --> 00:20:23.259 virus to a sterile environment. Just walking 00:20:23.259 --> 00:20:26.839 from one pen to another. Just that. But the environmental 00:20:26.839 --> 00:20:29.079 resilience of the virus itself is perhaps the 00:20:29.079 --> 00:20:32.549 most daunting variable. ISAV possesses a robust 00:20:32.549 --> 00:20:35.089 survival capacity in seawater. It doesn't just 00:20:35.089 --> 00:20:37.630 wash away. No, it doesn't instantly degrade when 00:20:37.630 --> 00:20:40.009 shed from the host. Which turns the ocean currents 00:20:40.009 --> 00:20:43.289 into an active delivery system. The hydrodynamic 00:20:43.289 --> 00:20:45.450 flow of the water means that simple physical 00:20:45.450 --> 00:20:48.069 proximity is a primary risk factor. Exactly. 00:20:48.230 --> 00:20:50.410 If an uninfected farm is situated downstream 00:20:50.410 --> 00:20:52.569 from an active outbreak, the virus can be carried 00:20:52.569 --> 00:20:55.150 directly into their pens. No shared equipment 00:20:55.150 --> 00:20:57.450 or personnel is required. The ocean does the 00:20:57.450 --> 00:21:00.160 work. The hydrodynamics explain the passive spread 00:21:00.160 --> 00:21:02.920 through the water column. But we must also address 00:21:02.920 --> 00:21:06.680 a highly specialized biological vector that complicates 00:21:06.680 --> 00:21:09.839 the epidemiology exponentially. The creepy courier. 00:21:10.019 --> 00:21:12.819 We must examine the role of the parasitic copod, 00:21:13.079 --> 00:21:16.440 Lepia ferris summonus. The sea louse. For anyone 00:21:16.440 --> 00:21:19.140 unfamiliar, this is a marine crustacean that 00:21:19.140 --> 00:21:22.319 survives as an obligate ectoparasite. It attaches 00:21:22.319 --> 00:21:24.500 itself directly to the exterior of the salmon. 00:21:24.660 --> 00:21:27.140 Grazing on the epidermal tissue, the scales, 00:21:27.539 --> 00:21:29.980 and the protective mucus layer of the fish. And 00:21:29.980 --> 00:21:32.619 laboratory research has definitively proven that 00:21:32.619 --> 00:21:35.200 Lepia therisomonas functions as a mechanical 00:21:35.200 --> 00:21:37.660 vector for the infectious salmon anemia virus. 00:21:37.799 --> 00:21:40.529 So it's physically moving it. Right. As it feeds 00:21:40.529 --> 00:21:43.410 on an infected host, it accumulates viral particles 00:21:43.410 --> 00:21:45.990 on its external carapace and within its digestive 00:21:45.990 --> 00:21:48.509 tract. When the modal stages of the louse detach 00:21:48.509 --> 00:21:51.190 and swim to a new healthy host, they carry the 00:21:51.190 --> 00:21:53.269 pathogen with them. It essentially acts as a 00:21:53.269 --> 00:21:56.269 swimming biological syringe, passively transferring 00:21:56.269 --> 00:21:58.630 the virus from one host to another. That's a 00:21:58.630 --> 00:22:01.369 vivid but accurate description. But the sources 00:22:01.369 --> 00:22:04.630 point to an area of ongoing research that suggests 00:22:04.630 --> 00:22:08.569 a much darker possibility. The critical unresolved 00:22:08.569 --> 00:22:10.849 question in the literature right now is whether 00:22:10.849 --> 00:22:14.390 ISIV is capable of true biological replication 00:22:14.390 --> 00:22:17.450 within the sea louse. Meaning the louse wouldn't 00:22:17.450 --> 00:22:19.990 just be passively carrying the virus on its shell, 00:22:20.089 --> 00:22:23.130 it would be an active incubator. Precisely. In 00:22:23.130 --> 00:22:25.349 terrestrial virology we see this mechanism frequently 00:22:25.349 --> 00:22:28.750 with arboviruses. Arthropod -borne viruses. Right. 00:22:28.890 --> 00:22:31.529 Pathogens like the dengue virus or West Nile 00:22:31.529 --> 00:22:34.640 virus. actively replicate within their mosquito 00:22:34.640 --> 00:22:37.299 vectors before being transmitted to a human host. 00:22:37.920 --> 00:22:40.839 Similarly, the African swine fever virus replicates 00:22:40.839 --> 00:22:43.619 within ticks. If Lepaeifderis salmonus acts as 00:22:43.619 --> 00:22:46.960 an active secondary vector for ISAV, it fundamentally 00:22:46.960 --> 00:22:49.279 changes the biosecurity landscape. It changes 00:22:49.279 --> 00:22:51.559 everything. Aquaculture facilities already spend 00:22:51.559 --> 00:22:54.000 millions trying to manage sea lice infestations 00:22:54.000 --> 00:22:56.380 simply because the physical damage the parasites 00:22:56.380 --> 00:22:59.460 cause weakens the fish. Yes. But if those sea 00:22:59.460 --> 00:23:02.019 lice are simultaneously breeding and amplifying 00:23:02.019 --> 00:23:05.180 a lethal orthomixovirus, eradication of the parasite 00:23:05.180 --> 00:23:07.519 becomes the absolute highest priority in disease 00:23:07.519 --> 00:23:10.440 control. And controlling the vector becomes paramount. 00:23:10.599 --> 00:23:13.700 Because the harsh reality of ISAVI management 00:23:13.700 --> 00:23:16.319 is the complete absence of therapeutic interventions. 00:23:16.799 --> 00:23:18.940 That brings us to the protocols for treatment 00:23:18.940 --> 00:23:22.539 and control. And it's grim. Once an Atlantic 00:23:22.539 --> 00:23:25.019 salmon is infected with a pathogenic strain of 00:23:25.019 --> 00:23:28.119 ISAVI, there is no antiviral drug. There is no 00:23:28.119 --> 00:23:31.569 cure. None. The focus shifts entirely from saving 00:23:31.569 --> 00:23:33.869 the infected stock to containing the pathogen. 00:23:34.029 --> 00:23:36.089 This is where regulatory frameworks like the 00:23:36.089 --> 00:23:38.509 European Union's list one classification come 00:23:38.509 --> 00:23:40.869 into play. Right. When a disease is designated 00:23:40.869 --> 00:23:44.630 as list one, it triggers a mandatory non -negotiable 00:23:44.630 --> 00:23:47.730 response protocol designed to eliminate the pathogen 00:23:47.730 --> 00:23:49.670 from the environment entirely. It triggers the 00:23:49.670 --> 00:23:52.150 nuclear option. It does. The protocol mandates 00:23:52.150 --> 00:23:54.990 the total eradication of the entire fish stock 00:23:54.990 --> 00:23:57.410 upon the confirmed presence of the disease. It 00:23:57.410 --> 00:23:59.490 doesn't matter if only a handful of fish in a 00:23:59.490 --> 00:24:02.529 single pen test positive, the entire facility's 00:24:02.529 --> 00:24:04.849 population must be called. And the rationale 00:24:04.849 --> 00:24:07.470 behind total eradication is grounded in the stealth 00:24:07.470 --> 00:24:10.009 nature of the virus we discussed earlier. Because 00:24:10.009 --> 00:24:12.769 they could all be infected. Because asymptomatic 00:24:12.769 --> 00:24:15.769 carriers can shed the virus extensively before 00:24:15.769 --> 00:24:18.950 clinical signs appear. Leaving any fish alive 00:24:18.950 --> 00:24:22.130 in a confirmed positive zone guarantees the continued 00:24:22.130 --> 00:24:24.509 presence and evolution of the pathogen. So the 00:24:24.509 --> 00:24:26.910 only way to break the epidemiological chain is 00:24:26.910 --> 00:24:29.529 to remove the hosts entirely. Exactly. But the 00:24:29.529 --> 00:24:32.089 execution of that mandate creates the massive 00:24:32.089 --> 00:24:35.130 socioeconomic fallout we saw in Chile and Canada. 00:24:35.710 --> 00:24:37.890 Culling hundreds of thousands of fish destroys 00:24:37.890 --> 00:24:40.150 the capital investment of the farm. It interrupts 00:24:40.150 --> 00:24:42.329 the global supply chain. And devastates local 00:24:42.329 --> 00:24:44.529 economies reliant on the aquaculture sector. 00:24:44.970 --> 00:24:47.799 The financial cure is often as ruinous as the 00:24:47.799 --> 00:24:51.099 viral disease. It is a draconian but necessary 00:24:51.099 --> 00:24:53.460 measure in the absence of absolute prevention. 00:24:53.950 --> 00:24:56.309 However, the scientific community isn't just 00:24:56.309 --> 00:24:59.069 giving up. They are actively developing preventative 00:24:59.069 --> 00:25:01.730 strategies to reduce the reliance on mass cullings. 00:25:02.130 --> 00:25:04.769 There are glimmers of hope. Yes. Research focusing 00:25:04.769 --> 00:25:07.410 on wild North American Atlantic salmon populations 00:25:07.410 --> 00:25:09.970 has revealed that individuals capable of surviving 00:25:09.970 --> 00:25:12.930 an eye -savvy infection do generate a robust 00:25:12.930 --> 00:25:15.349 neutralizing antibody response. Their immune 00:25:15.349 --> 00:25:17.710 systems can successfully map the virus and fight 00:25:17.710 --> 00:25:20.339 it off naturally. They can. And scientists are 00:25:20.339 --> 00:25:22.500 utilizing that immunological data to develop 00:25:22.500 --> 00:25:25.180 commercial vaccines. The literature indicates 00:25:25.180 --> 00:25:27.920 that while vaccines may not offer absolute sterilizing 00:25:27.920 --> 00:25:30.539 immunity, they have been demonstrably effective 00:25:30.539 --> 00:25:33.180 in significantly reducing the rate and severity 00:25:33.180 --> 00:25:35.900 of infection. And vaccination programs are increasingly 00:25:35.900 --> 00:25:38.299 being paired with advanced selective breeding 00:25:38.299 --> 00:25:41.160 initiatives. QTL mapping, right? Exactly. Quantitative 00:25:41.160 --> 00:25:44.779 trait loci mapping. By utilizing this, geneticists 00:25:44.779 --> 00:25:47.599 can identify specific lineages of Atlantic salmon 00:25:47.599 --> 00:25:50.259 that naturally possess a higher innate resistance 00:25:50.259 --> 00:25:52.960 to ISAV. So they're breeding the toughest fish. 00:25:53.460 --> 00:25:56.000 By prioritizing these resilient genetic lines 00:25:56.000 --> 00:25:58.700 in commercial brood stock, the industry is slowly 00:25:58.700 --> 00:26:01.960 attempting to cultivate a more robust virus -resistant 00:26:01.960 --> 00:26:05.130 population. So we're using modern molecular genetics 00:26:05.130 --> 00:26:07.430 and immunology to secure the future of these 00:26:07.430 --> 00:26:10.589 populations, but one of the most compelling pieces 00:26:10.589 --> 00:26:12.829 of this puzzle lies in the past. The origins. 00:26:12.970 --> 00:26:15.390 Yeah. To fully understand how this virus operates 00:26:15.390 --> 00:26:17.490 globally, we have to look at the evolutionary 00:26:17.490 --> 00:26:20.230 history of the pathogen, which reads like an 00:26:20.230 --> 00:26:23.150 epidemiological cold case. It really does. The 00:26:23.150 --> 00:26:25.289 genetic divergence of the two primary strains, 00:26:25.390 --> 00:26:27.349 the European and the North American, provides 00:26:27.349 --> 00:26:30.329 a fascinating timeline. How so? By analyzing 00:26:30.329 --> 00:26:34.150 the mutation rates across the viral genome, phylogeneticists 00:26:34.150 --> 00:26:38.009 can construct a molecular clock. This clock indicates 00:26:38.009 --> 00:26:40.089 that the European and North American strains 00:26:40.089 --> 00:26:42.829 diverged from their most recent common ancestor 00:26:42.829 --> 00:26:45.950 sometime around the year 1900. The year 1900 00:26:45.950 --> 00:26:48.740 is the critical anchor point here. Because a 00:26:48.740 --> 00:26:51.759 few decades prior to that divergence, human industry 00:26:51.759 --> 00:26:54.839 initiated a massive, unprecedented biological 00:26:54.839 --> 00:26:57.079 exchange across the Atlantic Ocean. The Victorian 00:26:57.079 --> 00:27:00.640 era. Right. Starting in 1879, the Victorian era's 00:27:00.640 --> 00:27:03.759 drive to acclimatize species globally led to 00:27:03.759 --> 00:27:06.220 the mass transatlantic shipping of live fish. 00:27:06.440 --> 00:27:08.779 The logistics of that era involved moving immense 00:27:08.779 --> 00:27:11.619 quantities of eggs and live specimens, particularly 00:27:11.619 --> 00:27:14.079 rainbow trout from North American waters to Europe 00:27:14.079 --> 00:27:16.900 via steamship. And concurrently, various European 00:27:16.900 --> 00:27:19.319 salmonid species were being transported and introduced 00:27:19.319 --> 00:27:21.480 into North American river systems. And as we 00:27:21.480 --> 00:27:23.519 established earlier, rainbow trout are exceptionally 00:27:23.519 --> 00:27:26.720 capable asymptomatic reservoirs for ISAV. They 00:27:26.720 --> 00:27:28.799 can carry the virus without succumbing to the 00:27:28.799 --> 00:27:31.660 disease. Exactly. So we have an era of massive 00:27:31.660 --> 00:27:34.900 unregulated transatlantic fish shipping peaking 00:27:34.900 --> 00:27:37.220 right before the genetic divergence of the virus 00:27:37.220 --> 00:27:40.440 in 1900. Which presents phylogeneticists with 00:27:40.440 --> 00:27:43.559 an unsolvable paradox. The blurred origin. The 00:27:43.559 --> 00:27:46.079 intense bi -directional movement of potential 00:27:46.079 --> 00:27:49.180 reservoir species immediately preceding the viral 00:27:49.180 --> 00:27:53.220 divergence has completely obscured the true geographical 00:27:53.220 --> 00:27:56.299 origin of ISOV. We literally cannot decipher 00:27:56.299 --> 00:27:59.200 the biological history. Did the ancestral virus 00:27:59.200 --> 00:28:02.559 evolve in North America and did humans inadvertently 00:28:02.559 --> 00:28:05.099 export it to Europe inside the holds of steamships 00:28:05.099 --> 00:28:07.640 carrying rainbow trout in the late 19th century? 00:28:07.940 --> 00:28:10.440 Or did it originate in European waters only to 00:28:10.440 --> 00:28:12.519 be shipped to North America during the same period? 00:28:12.680 --> 00:28:15.380 The human intervention was so massive that it 00:28:15.380 --> 00:28:17.539 permanently erased the evolutionary footprints. 00:28:17.660 --> 00:28:20.460 It is a profound demonstration of how globalized 00:28:20.460 --> 00:28:23.640 trade doesn't just move commodities, it redistributes 00:28:23.640 --> 00:28:26.049 and accelerates the evolution of pathogens. And 00:28:26.049 --> 00:28:28.390 this is not merely a historical curiosity is 00:28:28.390 --> 00:28:32.500 it? No, not at all. We see the exact same anthropogenic 00:28:32.500 --> 00:28:35.000 mechanism driving the modern spread of the disease. 00:28:35.299 --> 00:28:37.700 The epidemic that shattered the Chilean aquaculture 00:28:37.700 --> 00:28:41.279 industry in 2007 is the perfect modern parallel. 00:28:41.900 --> 00:28:44.279 Genetic sequencing tracked the origins of the 00:28:44.279 --> 00:28:46.799 specific pathogenic strains responsible for that 00:28:46.799 --> 00:28:49.319 collapse. And the data proved unequivocally that 00:28:49.319 --> 00:28:52.220 the virus did not spontaneously emerge or evolve 00:28:52.220 --> 00:28:54.880 in South America. The phylogenetic analysis mapped 00:28:54.880 --> 00:28:56.759 the transmission directly back to the northern 00:28:56.759 --> 00:29:00.009 hemisphere. The specific strains that Chile were 00:29:00.009 --> 00:29:03.710 introduced from Norway between 1995 and 2007. 00:29:03.950 --> 00:29:06.029 The movement of the virus was entirely driven 00:29:06.029 --> 00:29:08.710 by the logistical networks of the modern aquaculture 00:29:08.710 --> 00:29:11.069 industry. We ship the hosts, we ship the eggs, 00:29:11.190 --> 00:29:13.369 we ship the equipment and the virus just hitches 00:29:13.369 --> 00:29:16.490 a ride adapting to the new high density environments 00:29:16.490 --> 00:29:19.240 we provide. It's a sobering realization of how 00:29:19.240 --> 00:29:21.740 much influence we have over microscopic evolution. 00:29:21.940 --> 00:29:24.119 It really is. When we synthesize all of this 00:29:24.119 --> 00:29:26.339 data, the scale of what we are dealing with becomes 00:29:26.339 --> 00:29:28.960 incredibly clear. We are looking at a highly 00:29:28.960 --> 00:29:31.619 adaptable orthomixovirus that has evolved to 00:29:31.619 --> 00:29:34.539 exploit the nucleated erythrocytes of tele -est 00:29:34.539 --> 00:29:36.930 fish. It operates with a terrifying stealth, 00:29:37.150 --> 00:29:40.309 capable of utilizing asymptomatic reservoir species 00:29:40.309 --> 00:29:43.250 to spread across vast marine environments aided 00:29:43.250 --> 00:29:46.289 by ocean currents and parasitic vectors. And 00:29:46.289 --> 00:29:49.289 when a highly pathogenic strain breaches a dense 00:29:49.289 --> 00:29:52.269 aquaculture facility, it has the power to trigger 00:29:52.269 --> 00:29:55.289 total stock eradication mandates, collapsing 00:29:55.289 --> 00:29:57.829 local economies and disrupting global food supplies. 00:29:58.009 --> 00:30:01.089 Exactly. The broader implications of ISA extend 00:30:01.089 --> 00:30:03.509 far beyond the specific mechanics of fish farming. 00:30:03.640 --> 00:30:06.819 This pathogen serves as a vital case study in 00:30:06.819 --> 00:30:09.359 the fragility of modern agricultural monocultures. 00:30:09.720 --> 00:30:12.599 We put all our eggs in one basket. We do. It 00:30:12.599 --> 00:30:15.140 illustrates the relentless, unseen biological 00:30:15.140 --> 00:30:17.500 arms races occurring constantly within our oceans, 00:30:18.119 --> 00:30:20.220 and it underscores how human industrial practices 00:30:20.220 --> 00:30:23.099 fundamentally dictate the evolutionary trajectory 00:30:23.099 --> 00:30:25.369 of the pathogens we share this planet with. And 00:30:25.369 --> 00:30:27.950 that evolutionary trajectory leads us to one 00:30:27.950 --> 00:30:30.789 final, deeply provocative concept to consider 00:30:30.789 --> 00:30:33.210 based on the literature. We've established that 00:30:33.210 --> 00:30:35.730 wild salmon populations that survive an outbreak 00:30:35.730 --> 00:30:38.349 generate natural antibodies, navigating this 00:30:38.349 --> 00:30:40.789 biological threat through raw natural selection. 00:30:41.009 --> 00:30:44.130 Survival of the fittest. Right. Conversely, the 00:30:44.130 --> 00:30:46.910 massive commercial aquaculture industry relies 00:30:46.910 --> 00:30:50.190 on immense artificial interventions, lab -developed 00:30:50.190 --> 00:30:53.450 vaccines, and highly specific selective breeding 00:30:53.450 --> 00:30:56.200 programs to build... resistance. Artificial selection. 00:30:56.940 --> 00:30:59.400 But navigating the waters between these two distinct 00:30:59.400 --> 00:31:01.819 environments are the asymptomatic carriers like 00:31:01.819 --> 00:31:04.779 the Pacific salmon and the rainbow trout. They 00:31:04.779 --> 00:31:07.180 are continuously carrying and shedding highly 00:31:07.180 --> 00:31:11.019 pathogenic strains without falling ill. The immunological 00:31:11.019 --> 00:31:14.019 dynamic creates an incredibly tense scenario. 00:31:14.299 --> 00:31:16.720 It does. Because if we're heavily reinforcing 00:31:16.720 --> 00:31:19.519 one population with artificial vaccines, while 00:31:19.519 --> 00:31:21.819 another population relies on natural immunity, 00:31:22.259 --> 00:31:24.579 we have to question the evolutionary pressures 00:31:24.579 --> 00:31:27.619 we are applying to the pathogen itself. By constructing 00:31:27.619 --> 00:31:30.500 vast artificial walls of biosecurity and vaccination, 00:31:30.660 --> 00:31:32.839 are we simply forcing the virus into a corner? 00:31:32.920 --> 00:31:35.960 That's a very valid concern. In terrestrial virology, 00:31:36.039 --> 00:31:38.259 we've seen scenarios like Marek's disease in 00:31:38.259 --> 00:31:41.630 poultry, where imperfect or leaky vaccines prevent 00:31:41.630 --> 00:31:43.650 the host from dying, but still allow the virus 00:31:43.650 --> 00:31:45.930 to replicate and shed. Right, which is dangerous. 00:31:46.329 --> 00:31:48.670 This intense pressure can actively drive the 00:31:48.670 --> 00:31:51.410 evolution of hypervirulent strains that would 00:31:51.410 --> 00:31:54.009 otherwise kill their hosts too quickly to spread. 00:31:54.789 --> 00:31:57.630 So if ISD is continuously circulating within 00:31:57.630 --> 00:32:00.349 asymptomatic Pacific salmon, bouncing against 00:32:00.349 --> 00:32:03.049 the artificial immunity of farmed Atlantic populations, 00:32:03.470 --> 00:32:06.029 are we inadvertently operating an evolutionary 00:32:06.029 --> 00:32:08.559 pressure cooker? That is the big question. Are 00:32:08.559 --> 00:32:11.279 we actively driving the virus to adapt, mutate, 00:32:11.440 --> 00:32:14.019 and eventually shatter the natural relative resistance 00:32:14.019 --> 00:32:17.119 of the Pacific species entirely? It's a complex, 00:32:17.440 --> 00:32:19.339 unsettling question regarding the long -term 00:32:19.339 --> 00:32:21.920 consequences of our intervention in natural systems, 00:32:22.460 --> 00:32:24.279 something to critically ponder the next time 00:32:24.279 --> 00:32:26.200 you consider the delicate balance of the ocean 00:32:26.200 --> 00:32:28.500 or the profound science behind the salmon on 00:32:28.500 --> 00:32:28.880 your plate.