In a story of worldwide significance, foot and mouth disease spreads through Britain, and thousands upon thousands of farm animals are slaughtered. Farmers lose fortunes, millions are spent on economic relief and mitigation, and pundits question the very underlying principles of industrialized, contained animal husbandry. This is a true story from 2001, but the headlines in the British Isles were the same during foot and mouth epidemics in 1967, 1952, 1922, 1864, and when the disease first appeared in 1839.
Here in Maine the aquaculture industry is currently faced with a similar agricultural viral threat, and, under order of the state Department of Marine Resources and the federal Department of Agriculture, has had to destroy nearly 2.5 million fish in pens in Cobscook Bay. This direct loss of product will cost the farmers millions, as well as raising the prospect of lost jobs in Washington County. Furthermore there is the worry of possible transition of the disease to endangered wild Atlantic salmon (which could also negatively affect he industry under the provisions of the Endangered Species Act), and finally the specter of having to deal with this problem repeatedly in infected areas for years to come. The aquaculture industry and supporters are looking to Norwegian and Canadian scientists for answers, and while they recognize this as a serious problem, are dedicated to finding a workable solution. Aquaculture detractors, on the other hand, add up the viral and other environmental impacts and question if salmon farming is something we want to have in our waters at all. The future of Maine’s second most valuable marine resource — an industry worth over $60 million, placing it second only to lobster in economic impact. — hangs in the balance.
The disease
Infectious salmon anemia (ISA) is a viral disease affecting (predominantly farmed) Atlantic salmon. It is believed to have spread from Norway, where it was first diagnosed in 1984, to Canada, and now to Maine. Salmon farming is an international industry, and the spread of the disease has followed industry expansion into almost all major producing regions. New Brunswick was first struck in 1996, followed by Scotland and Nova Scotia in 1998, Chile in 1999, the Faroe Islands in 2000, and 2001 in Maine. British Columbia, alone of the world’s major Atlantic salmon farming regions, has been spared, but authorities and local environmental groups such as The Friends of Clayoquot Sound are on the lookout there for the virus, which could pose an added threat to the province’s significant wild salmon fisheries.
The virus can be carried by other species of fish, but has not been shown to cause the disease in them, and has not been shown to be transmittable from fish to humans. The disease causes severe anemia (low blood iron) in the fish, liver enlargement, internal hemorrhaging and death. Infected fish become lethargic and can sometimes be observed swimming at the surface of the nets. Mortality rates vary from 15 percent to 100 percent for the disease, but with eradication measures the mortality rate is of course always 100 percent. The fish is not rendered unfit for human consumption, but often times the slaughtered fish are too small for market, and are disposed of on shore. The blood and viscera from the processing facilities can also transmit the virus, so these facilities must take decontamination and proper disposal measures as well.
Currently there are two identified strains of the virus. The strain infecting Maine fish is called the New Brunswick strain, and fish in Norway have a distinct virus. This difference is not unusual, and the evolution of viral strains is often rapid, which leads to human flu vaccinations needing yearly changes as well.
Economic effects are significant and immediate, with companies having to eliminate their entire stocks in an infected area. With the fish taking three years to bring to market, the economic impacts last for years. Norway, the world’s largest farmed salmon producer at around 160,000 tons (compared to Maine at around 13,000 tons), has approached the infection problem as manageable, but has responded with millions in government assistance and subsidized insurance. Scotland has also put forward a nationally backed financial package for farmers, which was matched from the industry, and in New Brunswick the government provided approximately $10 million (Canadian) to mitigate an estimated $30 million financial loss from the disease. Here in the U.S., the Department of Agriculture has provided $8.3 million to implement an ISA control and indemnity program, which will assist the state with disease surveillance, depopulation and disposal of fish, and training for producers and veterinarians.
Cows, chickens, pigs and even buffalo
The history of viral outbreaks and other diseases of differing epidemiology in domesticated animals is a long and bloody story. But there have been successes in overcoming the problems of contained animal husbandry. Sandy Miller Hays, Director of Information for the Animal Research Service of the U.S. Department of Agriculture, could “think of no examples of cases where we just had to give up on raising a type of animal after an outbreak of disease, once we had approached the problem with science and good practices.”
Several of these diseases have been greatly reduced in recent years, such as brucellosis in cattle. According to Hays, this disease, which was not fatal to cows, but caused the spontaneous losses of calves by cows, was virtually eliminated thanks to the National Brucellosis Eradication Program, which began in 1934. This process was not quick, and Hays can remember dealing with this problem at the beginning of her career only 20 years ago. Unlike ISA, brucellosis can cause a human illness known as undulant fever, which can cause flu-like symptoms and has been known to lead to death. The eradication program has cost an estimated total (in 1997 dollars) of over $10 billion, and undulant fever is the main reason that virtually all dairy products in America are pasteurized today.
In a reversal of the situation with farmed and wild Atlantic salmon, brucellosis is potentially carried by wild bison and elk, and some fear the threat of transmission to domestic cattle herds. Buffalo containment is practiced outside of Yellowstone National Park for this reason. The only cases of undulant fever in humans in recent years have been tracked to infected Mexican goat herds, from which unpasteurized cheese had been made.
The “Asian bird flu,” which affects chickens and other fowl, has been in the headlines recently as well. Hong Kong recently ordered the slaughter of 1.2 million birds. Unlike the virus that causes ISA, this virus is transmittable and potentially dangerous to humans. In 1997 a three-year-old boy died from the bird flu, the first documented case of death from this particular strain. In the end six persons died and nearly two million chickens were destroyed. This toll on humans raises the memory of the Spanish Influenza pandemic of 1918, in which 25 million people were killed in a short time worldwide, from a viral strain that may have had its beginnings in pigs, then moved into chickens, and then to humans. (The 1918 pandemic is the worst case on record, and is offered only as an example of viral power, keeping in mind that infectious salmon anemia is not transmittable to humans and is not dangerous to human health.)
The 1918 pandemic may have originated in pigs, and indeed these animals are susceptible to a number of diseases. Modern veterinary medicine has advanced along with farming techniques, and today pigs are kept in concentrations unheard of just a few generations ago. Like cattle, they are susceptible to foot and mouth disease, but probably the most well known illness is classical swine fever, also known as hog cholera. This highly contagious disease does not affect humans, but has led to repeated outbreaks worldwide, with great loss of stock. After a 16-year campaign the United States eradicated the disease in 1978, along with 16 other countries. However, outbreaks continue in other countries. In 1997 Haiti and the Dominican Republic had devastating losses (both of which had been previously disease free for over a decade), and several European countries had outbreaks as well.
Even lobsters have been subject to diseases when contained in a restricted area. According to Professor Robert Bayer, University of Maine Professor of Aquaculture and director of the Lobster Institute, this has been a reoccurring problem for lobster pound operators, who can be struck with the bacteriological illnesses red tail (gaffkemia) and shell disease. These infections are contagious, and can quickly spread in the crowded conditions of the pound. These diseases are also present in the wild, but are less prevalent. Study of this problem has been a focus of the Lobster Institute.
Even wild schools of herring are subject to disease, and all other animals that are kept have incidence of devastating illness. Sheep can be brought down by encephalopathy, and the new game ranching industry in the west has had losses from a new and not completely understood condition called Chronic Wasting Disease.
Solutions
The ISA virus was first detected in Maine salmon in February 2001, which led to the order to eradicate almost a million fish. This first measure was unfortunately not successful in controlling the outbreak, and on January 7, 2001, all the remaining fish in Cobscook Bay were removed, and the bay was to be “fallowed” at least until the following spring. Although the cause of ISA has been positively identified, there is still no treatment for the condition other than eradication of the infected population.
The development of anti-viral technology (a vaccine or other treatment) is underway, but an effective solution is believed to be still some years away. The strain was first isolated and successfully replicated only in 1995. Norwegian fish pathologists lead much of the research, and while a treatment has not been identified, fish farms in that country have adopted a strict set of practices minimizing the possibility of further catastrophic outbreaks, guidelines that have now been adopted in Maine.
Age classes of fish are to be separated on different sites, and lease sites for pens are being allowed to lie fallow with no fish for differing periods of time. Along with early detection and immediate removal, this bay-by-bay management (separating groups of fish) seems to have significantly slowed the spread of the disease. According to spokespersons for Atlantic Salmon of Maine, the state’s largest producer of farmed salmon, these guidelines comprise a “best management strategy” that they have been following.
Implementing a policy of separating year classes of fish has been slowed, however, by the difficulty in obtaining enough geographically distant lease sites. These primarily proactive procedures will be combined with disease treatment as it is developed. The company points out that frunculosis, another infectious salmonid disease, threatened the industry a few years ago but has now been mainly eradicated. Spokesmen pointed out that these management practices will not eliminate pathogen exposure, as a typical teaspoon of sea water can contain from 50 thousand to 50 million viruses, but will allow for conditions where outbreaks cannot become endemic.
Other solutions proposed have included the elimination of salmon farming in Maine, or the institution of more expensive “closed” systems. Such systems do not raise the fish in open-ocean, floating netpens, but rather bring them up on land into raceway or pond structures. Much of the aquaculture in the world is done in this way, but predominantly for freshwater fish such as tilapia or catfish. Raising saltwater fish in this way would require pumping large quantities of water into the facilities, and treating the water upon discharge. This would increase costs by an undetermined amount (estimated in one study at 18 percent), and the industry says that in the global marketplace for salmon, even a small increase in costs can render a producer uncompetitive. Other “semi-open” systems are being investigated, but none has yet proved practical on large scale.
Along with disease, Maine salmon farmers have faced other hurdles in the last few months as well, including legislative moves make the lease process more difficult, the desire of some groups not to have any farming in their home waters, the recently imposed requirement to obtain federal waste water permits, and generally weak prices. For lessons in the management of salmon farms, the industry looks to the many other countries in the world raising these fish, hoping that this larger effort will result in better treatment and preventative schemes.