Oyster bed

There’s no need to worry – oyster herpes is not transferable to humans by eating “the food of love”.

This incurable, not to mention deadly, virus is a grave concern to the fishing communities in Europe. Oyster herpes is on the rise in Europe, and could go on spreading itself out even further, should the seas continue to get warmer, experts warn.

This past July farmed oysters were tested and the first known United Kingdom cases of herpes was detected in shellfish. This virus has already made its mark, killing somewhere between 20 and 100 percent of the breeding pacific oysters in some French beds from 2008 until 2010, according to, Ifemer, the French Research Institute for Exploitation of the Sea.

The reason that oyster herpes has been emerging more in Pacific oysters off of England still has scientists stumped, however many are speculating that Global Warming has something to do with it.

A new strain of Oyster herpes (Ostreid herpesvirus), remains dormant until the temperature of the water exceeds 16 degrees Celsius. UK waters reach this temperature in the height of summer, according to a member of the British government’s Fish Health Inspectorate, Kevin Denham.

Keeping that fact in mind, the director of Ifemer’s genetic and pathology lab, Tristan Renault, has commented that global warming “could be an explanation of the appearance of this particular type of virus.”

Though all of the herpes strains are DNA-based viruses, herpes, which infects everything from elephants to chickens to monkeys, comes in an astonishing number of species, each with their own distinct set of symptoms.

In humans, the best known forms of herpes are the Herpes simplex viruses, which spread through close contact and can produce symptoms such as oral and genital blisters.

Ostreid herpes viruses have been shown to affect not only oysters, but also scallops, clams and other scallops, explains Renault.

New Oyster Herpes

Shellfish who are infected with herpes are not new to the scientific world, however, in 2008 – the first year where there was a marked increase in the mortality rates detected in France – Ifremer stumbled upon a new strain of the virus.

Much like the other strains of the oyster herpes virus which infect mollusks, this new strain singles out younger oysters during the breeding season when the bodies of the mollusks’ are focusing all their energy on producing sperm and eggs, leaving them without enough energy to maintain their immune system Renault explains.

However, this new strain of oyster herpes is “more virulent than strains we have identified before,” Renault continued, adding that the virus is extremely efficient when it comes to killing its hosts, and can eradicate 80 percent of the oysters in a bed inside a week.

The most starting thing about this new strain of oyster herpes, is that the only visible sign there is something amiss, is the mortality rate, because oyster herpes does not have any visible symptoms, and can only be diagnosed through a lab test.

Viral hemorrhagic septicaemia (VHS) is a disease caused by a negative-sense single-stranded RNA virus of the genus Novirhabdovirus. Infected fish suffer from haemorrhaging of their internal organs, skin and muscles. Symptoms that can be observed from the outside includes reddened eyes, gills, skins and fin, opens sores, a bloated abdomen, and bulging eyes, but some fish show no outward signs at all.

The virus can spread through water transfer and through the consumption of infected eggs or fish, which means that baitfish can introduce the fish to new localities. A fish that manages to survive the disease can become a lifelong carrier of the virus, excreting it through its urine and sperm or ovarian fluids. In Europe, the gray heron is known to spread the virus without being infected; the virus appears to remain inactive as long as it resides in the digestive tract of the bird.

Different strains with different properties

Historically, VHS was associated with Western Europe where it was documented as a pathogenic disease among cultured salmonids as early as the 1950s. In 1963, the viral cause of the disease was discovered by M. H. Jenson. Until late 1988, VHSv Type I was the only known strain of the disease and it appeared to be contained within freshwater fish farms in continental Europe, affecting primarily rainbow trout and only occasionally brown trout and pike.

In 1988 the first case of VHS was reported from the United States and the culprit turned out to be a distinct, more marine-stable strain of VHSv than the European variant. The virus was present in salmon returning to Washington State from the Pacific Ocean. Today, we know of four different main strains and except for type IV, all of them are endemic to Europe.

The type IV virus can be divided into two subtypes: IV-a and IV-b. IV-a has been reported from marine fish living in the Northwest Pacific, along the North American north Atlantic coast, and along the shores of Japan and Korea. IV-b is the type causing problems for freshwater fish in the North American Great Lakes region.

The IV-b strain was first isolated from fish living off Canada’s Atlantic coast where it did not cause any high mortality rates. This strain is capable of infecting not only salmonids but a long row of warm-water freshwater species previously assumed to be resistant to VHS. The European strains are particularly deadly do rainbow trout, but the IV-b strain only have a mild affect on this species. It is on the other hand capable of killing fish such as chinook salmon, lake trout, steelhead trout, gobies, emerald shiners, yellow perch, walleye, muskies and whitefish.

A team of U.S. scientists has documented the first transmission of the lethal phocine distemper virus from the Atlantic Ocean to a population of sea otters living along the coast of Alaska.

The presence of phocine distemper virus has been confirmed in nasal swabs take from live otters and through necropsies conducted on dead otters found along the Alaskan coast. The findings also indicate that the virus was passed between seal species across Northern Canada or Arctic Eurasia before reaching the otters in Alaska’s Kachemak Bay.

Prior to this study, PDV had never been identified as the cause of illness or death in the North Pacific Ocean and researchers suggest that diminishing Arctic sea ice may have opened a new migration route for both animals and pathogens.

The study was carried out by researchers from two California universities and the Alaskan branch of the U.S. Fish and Wildlife Service. It has been published in ”Emerging Infectious Diseases”, a journal published by the U.S. Centers for Disease Control and Prevention.

What is phocine distemper virus (PDV)?

Phocine distemper virus (PDV) is a paramyxovirus of the genus Morbillivirus. It is dangerous for pinniped species, especially seals, and is a close relative of the canine distemper virus (CDV).

PDV was first identified in 1988 when it caused the death of approximately 18,000 harbour seals, Phoca vitulina, and 300 grey seals, Halichoerus grypus, in northern Europe. In 2002, the North Sea lost approximately 21,700 harbour seals in new a PDV outbreak – estimated to be over 50% of the total population.

Infected seals normally develop a fever, laboured breathing and nervous symptoms.

Several types of commonly used fish egg disinfectants increase the risk of swim bladder disorder in fish, a new study from Israel reveals.

In an effort to prevent fungal growth, many fish breeders use various chemicals, such as methylene blue, hydrogen peroxide, acriflavine and chloramine-T to aquariums where eggs are kept. This practise is especially common among breeders who will not let the parents stay with eggs and fry. Many fish species carry out parental care and eggs from such species often depend on one or both parents gently fanning fresh water over them and manually removing any unfertilized eggs from the batch. Without such parental care, the eggs easily succumb to fungi unless the fish breeder adds some type of fungicide to the water.

The new Israeli study, which focused on Angelfish (Pterophyllum scalare), revealed that some of these chemicals may be responsible for a swim bladder disorder in developing fish. In fish suffering from this type of disorder, the swim bladder can not inflate properly and the fry fails to develop into a fully free-swimming adult. Among aquarists, such fish are commonly known as “belly sliders” due to their peculiar way of moving around the fish tank.

Methylene blue

Eggs hatched in the presence of 1, 2 and 5 ppm methylene blue exhibited significant increases in swim bladder non-inflation (11%, 9% and 33%, respectively; none in controls).

Time of exposure to methylene blue was a key factor. Exposure for up to 1 day post-hatch did not affect swim bladder non-inflation, but exposure from 2 days onwards significantly increased swim bladder non-inflation.

Hydrogen peroxide

Hydrogen peroxide at 250 ppm significantly increased swim bladder non-inflation (65% comparing to 27% in the control). Higher concentrations resulted in 100% mortality.

Acriflavin

Exposure to acriflavin at 2.25 ppm, but not 1.25 ppm, significantly increased swim bladder non-inflation (75% and 52% respectively; 20% in controls).

Chloramin-T

Chloramine-T did not significantly affect swim bladder non-inflation.

For more information, see the paper “C. Sanabriaa, A. Diamantb and D. Zilberga (2009) – Effects of commonly used disinfectants and temperature on swim bladder non-inflation in freshwater angelfish, Pterophyllum scalare (Lichtenstein)”. The paper has been published in the journal Aquaculture.

A Taiwan research team has successfully extracted a brain-boosting nutrient from squid skin, according to an announcement made by the Council of Agriculture’s Fisheries Research Institute.

The nutrient in question is phospholipid docosahexaenoic acid, commonly known as PL-DHA, a substance known to improve a persons memory and enhance learning ability.

According to the institute official, PL-DHA is superior to TG-DHA another form of docosahexaenoic acid commonly found in deep-sea fish oil — when it comes to inhibiting degradation of the intellect since PL-DHA can cross the blood brain barrier and be absorbed directly by the brain.

Researchers at the institute have also showed that PL-DHA is effective in reviving neural cells and enhancing the content of three oxidation-resistant enzymes — GSH, CAT and SOD. In addition to this, the fatty acid will moderate the oxidative damage to neural cells that can be induced by free radicals in the body, which means that it will decrease the pace of plaque and tangle accumulation in brain cells.

Quoting medical reports, the institute official stressed that Alzheimer’s and other forms of senile dementia is known to be associated with the accumulation of plaque and tangles in the brain.

A new disease has been discovered; a disease that effects both Leafy seadragons (Phycodurus eques) and Weedy seadragons (Phyllopteryx taeniolatus).

The disease, which as now been described by veterinary pathologists, is a type of melanised fungus that causes extensive lesions and necrosis of the gills, kidneys and other areas of the body in seadragons. The disease was discovered in seadragons kept in aquariums.

Experts from the Department of Pathobiology and Veterinary Science at the University of Connecticut has identified the presence of both Exophiala angulospora and an undescribed Exophiala fungus in sick seadragons.

You can find more information in the paper[1] by Nyaoke et al published in the Journal of Veterinary Diagnostic Investigation[2] in January this year.

The Leafy seadragon (Phycodurus eques) and the Weedy seadragon (Phyllopteryx taeniolatus) are both marine fish species belonging to the same family as seahorses and pipefish. The Leafy seadragon is covered in long leaf-like protrusions that serve as camouflage, while the Weedy seadragon is camouflaged by weed-like projections. Both species are native to Australian waters.