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INTERNATIONAL
PRIORITIES
AND PERSPECTIVES
Short Plenary
Presentations and Panel Discussion
The Fish Health Section of the American Fisheries Society
in 2010:
Organizational and Professional Activities with an International
Perspective
Patricia A. Barbash*
The American Fisheries Society - Fish Health Section (AFS-FHS) is
made up of an array of professionals who have provided the framework for
modernized diagnostic methodology, disease management, and government
regulation. Our membership includes nearly 300
professionals. Although primarily
located in the United States and Canada, members originate from eleven other
countries worldwide. A third of
FHS members are represented by academic professionals and students. More than 60 members represent private
industry as practitioners, consultants, diagnosticians, and non-profit research
organizations. Approximately 50
members are employed by federal agencies including the U.S. Fish and Wildlife
Service, U.S. Geological Survey, National Oceanic and Atmospheric
Administration, the U.S. Department of Agriculture, Department of Fisheries and
Oceans (Canada), and the Department of Primary Industries (Australia). Many members work for state agencies,
tribal organizations, and provincial governments.
Asian
Fisheries Society - Fish Health Section
Ikuo Hirono*
Professor, Tokyo University of
Marine Science and Technology, 4-5-7 Konan, Tokyo, 108-8477, Japan hirono@kaiyodai.ac.jp
The Fish Health Section (FHS) of the Asian Fisheries Society (AFS) was formed on 30 January 1989 during the Third Asian Fish Health Network (AFHN) Meeting, held at the Faculty Fisheries and Marine Science, Universiti Pertanian Malaysia (UPM). The Section's goal is to improve regional knowledge on fish health management and to develop awareness among Asian aquaculturists towards establishing a sustainable aquaculture industry.
promote effective interaction and
cooperation among persons involved in fish health research;
encourage and promote
investigation and advances in knowledge of fish health;
focus attention on fish health
problems by disseminating technical and other information on all aspects
of fish health; and
promote the proper implementation
of effective fish health protection practices in the region.
The Fish Health Sections realizes these objectives by:
holding, on a regular rotational
basis, a triennial "Symposium on Diseases in Asian Aquaculture,"
a meeting of members to discuss broad issues and specific topics related
to fish health;
compiling and disseminating
proceedings, notes and abstracts of Section-sponsored fish disease
conferences and workshops, and other relevant information on fish health
to Section members and to the general public;
compiling and submitting a report
to the parent Society covering the period since the last Triennial General
Meeting, containing a summary of the activities of the Section (in the
region), the status of fish health problems, significant progress made
towards their control, and recommendations for Society action, as
appropriate; and
promoting the development and use
of standardized, internationally accepted techniques for the detection and
diagnosis of diseases of aquatic animals determined to have regional
importance.
Symposium on Diseases in Asian Aquaculture
The Fish Health Section of the Asian Fisheries Society is tasked with publishing both academic and technical information on aquatic animal health as well as promoting the development and use of standardized, internationally accepted techniques for the detection and diagnosis of diseases of aquatic animals of regional importance. The FHS also holds a triennial “Symposium on Diseases in Asian Aquaculture” (DAA) where members and aquatic animal health professionals meet to discuss broad issues and specific topics related to aquatic animal health.
There
have been seven previous Symposia, the first one in Bali, Indonesia, 1990;
second in Phuket, Thailand, 1993; third in Bangkok, Thailand, 1996; fourth in
Cebu, Philippines, 1999; fifth in Gold Coast, Australia, 2002; the sixth in
Colombo, Sri Lanka, 2005, and the seventh in Tapei, Taiwan, 2008. Each of these
Symposia brought together more than 200 aquatic animal health scientists,
students, government researchers and industry personnel from some 30 countries
to discuss disease related problems affecting aquaculture production and to
find solutions for them. The
Eighth Symposium – DAA VIII – is expected to attract many
participants from around the world to discuss their work and develop strategies
for improving aquatic animal health in Asia. DAA VIII will be held in
Mangalore, India.
AFS-FHS Executive Committee
(2009-2011):
Chairperson: Professor Chu-Fang
Lo (Taiwan), Vice Chairperson:
Professor Chadag Vishnumurthy Mohan (India), Secretary/Treasurer: Dr. Suppalak Lewis (Thailand), Past
Chairperson: Professor Takashi Aoki (Japan).
Committee Members:
Dr. Celia Lavilla-Pitogo
(Philippines), Dr. Brian Jones
(Australia), Dr. Mangalika
Hettiarachchi (Sri Lanka), Mr.
Arun Padiyar (India), Dr. Jianhai
Xiang (China), Dr. Nguyen Huu Dung
(Vietnam), Professor Myung-Joo Oh
(Korea)
Official
website:
European Association of Fish
Pathologists (EAFP)
Sven M. Bergmann*, Stephen W. Feist, David Bruno, Lone
Madsen, Roy Palmer and José Garcia
The “European Association
of Fish Pathologists (EAFP)” was established on October 25th 1979 in
Munich, Germany. It represents an interdisciplinary society, embracing all
aspects of aquatic disease in fish, shellfish and crustaceans, in aquaculture
and in wild stocks. Additionally, amphibians and reptiles are included. Members
come from all disciplines, biologists, microbiologists, veterinarians, fish
farmers and aquaculture engineers. The objective of the EAFP is to promote the
rapid exchange of experience and information on aquatic disease problems and
related topics. These aims are pursued mainly through regular regional and
international meetings, support for training courses in laboratory techniques
and the publication of the Bulletin of the EAFP, a fully citeable journal
listed in ASFA, Current Contents and Science Citation Index. The EAFP web site, www.eafp.org provides online access to archive EAFP Bulletins, information
on the EAFP conference and other events, workshop reports and a members message
board is also available. At the conferences, histological workshops are
organised, and the outcome of these workshops are later published on CDs.
Ruth
Francis-Floyd*
Kazuo Ogawa1 and Mamoru Yoshimizu2*
1 Department of Aquatic
Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo,
Bunkyo-ku, Tokyo 113-8657, Japan aogawak@mail.ecc.u-tokyo.ac.jp
2 Laboratoryof Biotechnology and Microbiology, Faculty of Fisheries Sciences, Hokkaido
University,
Hakodate, Hokkaido 041-8611, Japan yosimizu@fish.hokudai.ac.jp
In Japan, annual capture
fishery production has gradually declined from 5.3 to 4.3 million tons over the
last decade (1999-2008), whereas aquaculture production (fish, shellfish and
seaweed) has been stable during the same period, fluctuating annually between
1.2 and 1.3 MT. Despite no major change in production, the Japanese aquaculture
industry has been adopting different strategies in an effort to obtain higher
profits from their products. These include developing disease resistant
strains, better quality meat of cultured species, and culturing challenging new
species like Pacific bluefin tuna Thunnus
orientalis.
National Shellfisheries Association: Priorities and Perspectives from the Shellfish Side
Roxanna
Smolowitz*
The National Shellfisheries Association (NSA) is an
international organization of scientists, management officials and members of
industry. The focus of the
organization is biology, ecology, production, economics and management of
shellfish resources - clams, oysters, mussels, scallops, snails, shrimp,
lobsters, crabs, among many other species of commercial importance. The NSA’s
goals are: to encourage research on molluscs, crustaceans, and associated
organisms with an emphasis on species of economic importance known as
“shellfish”; to gather and disseminate scientific and technical information on
shellfish; to promote and advance shellfisheries research and the application
of results to the shellfish industry. There are currently 608 paid members. While a majority of the NSA members are from the U.S.,
Canada and Mexico, the NSA is an international association with total
membership representing 40 countries from around the world. Membership is open to all individuals
who actively support the objectives and purposes of the NSA. The organization
provides an important method of communication between its members that include
the regulators and aquaculturists, as well as researchers. An annual meeting is held each year
that promotes these important interactions.
PLENARY
SPEAKERS
FULL ABSTRACTS
Viral Hemorrhagic
Septicemia Virus: An Old Virus With New Tricks
Viral hemorrhagic septicemia virus (VHSV) is the
causative agent of the fish disease known as viral hemorrhagic septicemia
(VHS). This was first described as
a disease of freshwater-reared rainbow trout in Europe in 1938, and it has
continued to cause severe losses in the European trout farming industry since
the 1950s (Wolf, 1988; Smail, 1999, Skall et al., 2005). The virus causes acute
systemic disease and hemorrhagic lesions among juvenile rainbow trout with
mortality rates as high as 90%. Until the late 1980s, VHSV was thought to be geographically limited to
continental Europe. In 1988 VHSV
was isolated for the first time in western North America from asymptomatic
adult Coho salmon and Pacific cod showing extensive hemorrhagic lesions
(reviewed in Meyers and Winton, 1995). Surveys of wild fish in the North-east Pacific showed an extensive
reservoir of VHSV in many marine species. Although experimental challenge studies indicated the Pacific Ocean VHSV
was not virulent for rainbow trout, the virus is not apathogenic as several VHS
epidemics have been documented in wild Pacific herring and sardines (Meyers
& Winton, 1995; Hedrick et al., 2003). Subsequently, marine fish surveys in
waters around Europe found an extensive marine reservoir of VHSV, again
involving many host species (Skall et al., 2005). VHSV has also been isolated
from wild and farmed olive flounder (Paralichthys olivaceus) in Japan and Korea
(Nishizawa et al., 2002; Kim et al., 2003). Thus, until 2005 our understanding of VHSV was that it was a
marine virus with a broad host range, endemic to many marine host species in
the North Atlantic and Pacific Oceans. The historical role was thought to be due to adaptation of an ancestral
marine virus to cultured rainbow trout in Europe, where it has been endemic and
epidemic for many decades.
VHSV has recently emerged in the Great Lakes region
of North America. This represents
a geographic invasion of an extensive ecosystem, and it is the first time VHSV
has caused large-scale epidemics in free-ranging freshwater fish populations.
The emergence of VHS in the Great Lakes began with the isolation of VHSV from a
diseased muskellunge (Esox masquinongy)
from Lake St. Claire in 2003 (Elsayed et al., 2006), and a large-scale fish
kill in freshwater drum (Aplodinotus
grunniens) in Lake Ontario in 2005 (Lumsden et al., 2007). In 2006 and 2007 there were numerous
large fish kills throughout the lower Great Lakes, often involving multiple
host species. VHSV has now been
isolated from 28 Great Lakes host species from a wide diversity of taxonomic
families, including several important aquaculture and recreational species such
as muskellunge, walleye, Chinook salmon, and whitefish. Geographically it has spread into Lake
Huron, Lake Michigan, and several inland lakes and waterways of New York, Ohio,
Michigan, and Wisconsin. Most
disturbingly, it has been isolated recently in the Ohio River watershed, which
is not within the Great Lakes basin but instead drains into the Mississippi
River. In 2008-2010 there have
been fewer reported fish kills due to VHSV in the Great Lakes, but several
surveillance studies found VHSV frequently in both fish and water samples from
numerous sites, indicating the virus persists (Bain et al., 2010). To date, Great Lakes VHSV has spread to
all five of the major Great Lakes, but it has been isolated only from free
ranging fish, and it has not been found in aquaculture.
VHSV is a member of the genus Novirhabdovirus,
within the family Rhabdoviridae (Tordo et al., 2004). The genome of VHSV is a
linear single-stranded, negative-sense RNA molecule of approximately 11,000
nucleotides, with six genes in the order 3’-N-P-M-G-NV-L-5’ (Schüetze et al.,
1999). Extensive genetic typing of hundreds of VHSV field isolates has revealed
divergence into phylogenetic sub-groups. Prior to the emergence of VHSV in the Great Lakes, phylogenies of N and
G gene sequences by European researchers defined four genotypes of the VHSV
that appeared to be distributed geographically, rather than by host or year of
isolation (Snow et al., 2004; Einer-Jensen et al., 2004). Genotypes I, II and III are found in
marine fish in waters around Europe, and within genotype I, all VHSV isolates
from European freshwater trout farms fall into a sub-lineage called Ia. VHSV
genotype IV contains all VHSV isolates from the Pacific coast of North America,
as well as VHSV from Japan and Korea. When VHSV emerged in the Great Lakes, the first isolate obtained (strain
MI03 from Michigan in 2003) was typed by its glycoprotein gene sequence as
being most closely related to the North American VHSV genotype IV, and was
clearly distinct from the three European genotypes (Elsayed et al., 2006). Although MI03 was closest to genotype
IV, it differed from the closely related Pacific coast genotype IV isolates by
3.6–3.7% at the nucleotide level. Therefore the Great Lakes isolate was
placed in a distinct sub-lineage (IVb) of the phylogenetic tree, with the
Pacific coast VHSV isolates comprising sub-lineage IVa (Elsayed et al., 2006).
Four VHSV isolates from fish in brackish water off the Atlantic coast of Canada
have also been characterized and found to be within major genotype IV, closely
related to Great Lakes VHSV (Gagne et al., 2007).
The phylogenies of VHSV revealed evidence of
adaptation to cultured rainbow trout in the past, followed by long-term persistence
and economic losses in European trout aquaculture. It appears that an ancestral
virus from genotype I in marine hosts gained entry to cultured trout and
diverged into the prevalent sub-lineage Ia that has plagued European trout
farms since the 1950s (Einer-Jensen, 2004). This host jump into rainbow trout
is hypothesized to have resulted from use of unpasteurized fish by-products as
feed for juvenile fish in the early years of fish culture. The potential for
VHSV to adapt to cultured trout has been confirmed more recently by VHS
outbreaks in marine netpen-reared rainbow trout in Europe. Outbreaks in Sweden and Finland between
1998-2002 were found to be caused by genotype I subtypes Ia and Ib. In the most recent case in Norway
(Lyngstad et al., 2008) the disease epidemic diagnostic signs were typical for
VHSV genotype Ia, but genetic typing revealed that it was caused by a virus
from genotype III. This is the
first time a genotype III virus has been isolated from cultured trout. These
adaptation events are not numerous considering the number of years fish have
been cultured, but their consequences can be great, imposing genuine
limitations on trout aquaculture. Extensive experimental infection studies with
European VHSV isolates from genotypes I, II, and III have shown that marine
isolates are not virulent for rainbow trout (Skall et al., 2005), but they can
be for marine species such as turbot. VHSV outbreaks have been reported in cultured turbot in both Scotland
and Japan, suggesting that the presence of the marine reservoir of VHSV can be
a threat to the culture of this species.
At present, experimental infection studies show that
the new VHSV genotype IVb that is emerging in the Great Lakes region is not
currently virulent for rainbow trout, but it has an extremely broad host range,
and is virulent in Great Lakes species such as yellow perch. Lessons from Europe indicate that it
has the potential to adapt to cultured hosts. Since the initial detection of
VHSV in the Great Lakes numerous state, federal, and academic fish health
researchers have contributed great effort toward investigating fish kills and
surveying for the virus in Great Lakes fish. This has resulted in over 100 isolations of VHSV from
various fish species at a wide range of locations and at different times. Genetic typing indicates that the
genetic diversity of VHSV in the Great Lakes is extremely low at this early
stage in the emergence event, but there are indications of the beginning of
diversification. Genetic typing
has identified 12 different genotypes of Great Lakes VHSV by sequencing of a
669-nucleotide portion of the viral G gene. These genotypes appear randomly distributed among hosts and
over time, but there is evidence of early spatial patterns for the most common
types. The emergence of VHSV IVb in the Great Lakes represents the first time
this virus has become established in a freshwater ecosystem in North
America. The large-scale epidemics
that have ensued in free-ranging fish are typical of the interactions between a
newly introduced pathogen and naive host populations that have no prior
experience with the pathogen, and thus no immunity.
In nature, VHSV is transmitted both horizontally by
water-borne virus, and vertically as egg-associated virus (Wolf 1988; Smail,
1999). In salmonid aquaculture,
vertical transmission can be eliminated by egg disinfection with iodophore
compounds. Despite decades of
effort, there are no commercially available vaccines in common use against
these pathogens. Inactivated,
attenuated, and sub-unit vaccines can be effective, but have not proven
sufficiently consistent or safe for common application. DNA vaccines work well (Lorenzen and
LaPatra, 2005) but are not currently licensed in the U.S. or Europe, and at
present require injection delivery, limiting their use in juvenile fish. Thus the principle methods of
controlling VHSV remain destruction of infected fish and strict biosecurity
measures to prevent introduction of the pathogen to aquaculture
facilities. From a research perspective,
the most promising developments for enhancing our knowledge of both European
and North American VHSV include many advances in fish immunology, and the
generation of infectious clones of VHSV. Combined with studies of viral infections both in vivo and in vitro,
these tools will provide the next generation of tricks on the human side, for
dealing with the tricks of this adaptable virus.
References
Einer-Jensen K., Ahrens P., Forsberg R. &
Lorenzen N. (2004) Evolution of the fish rhabdovirus viral haemorrhagic
septicaemia virus. Journal of General Virology 85, 1167-1179.
Elsayed, E., Faisal, M., Thomas, M., Whelan, G.,
Batts, W., & Winton, J. (2006). Isolation of viral
haemorrhagic septiceaemia virus from muskellunge, Esox masquinongy (Mitchill),
in Lake St Clair, Michigan, USA reveals a new sublineage of the North American
genotype. Journal of Fish Diseases 29, 611-619.
Gagne N., MacKinnon A.-M., Boston L., Souter B.,
Cook-Versloot M., Griffiths S., and Olivier, G. (2007) Isolation of viral hemorrhagic septicemia virus
(VHSV) from mummichogs, sticklebacks, striped bass, and brown trout in eastern
Canada. Journal of Fish Diseases
30:213-233.
Hedrick, R.P., Batts, W.N., Yun, S., Traxler, G. S.,
Kaufman, J., & Winton, J.R. (2003). Host and geographic range extensions of
the North American strain of viral hemorrhagic septicemia virus. Diseases
of Aquatic Organisms 55, 211-220.
Kurath, G. (2008). Biotechnology and DNA vaccines for aquatic animals. Review, Scientific and Technical Office
of International Epizootics 27, 175-196.
Lorenzen N. & LaPatra S. E. (2005). - DNA
vaccines for aquacultured fish. Revue Scientifique Et Technique-Office
International Des Epizooties 24, 201-213.
Lumsden J.S., Morrison B., Yason C., Russell
S., Young K., Yazdanpanah A., Huber P., Al-Hussinee L., stone D., and Way K. (2007). Mortality event in freshwater drum (Aplodinotus grunniens)
from Lake Ontario, Canada, associated with viral hemorrhagic septicemia virus ,
Type IV. Dis. Aquat. Org.
76:99-111.
Lyngstad, T.M., Hogasen, H.R., Orpetveit, I.,
Hellburg, H., Dale, O.B., & Lillehaug, A. (2008). National Veterinary
Institute's report series No. 3. Scientific evaluation of the eradication
of viral hemorrhagic septicemia in Storfjorden. National Veterinary
Institute, Oslo, Norway.
Meyers T.R.
& Winton, J.R. (1995). Viral hemorrhagic septicemia virus in North America. Annual Review of Fish
Diseases 5, 3-24.
Nishizawa T., Iida H., Takano R., Isshiki T.,
Nakajima K., and Muroga K. (2002). Genetic relatedness among Japanese, American, and European isolates of
viral hemorrhagic septicemia virus (VHSV) based on partial G and P genes. Dis. Aquat. Org.
48:143-148.
Schütze, H., Mundt, M.,
& Mettenleiter, T.C. (1999). Complete genomic sequence of viral hemorrhagic
septicemia virus, a fish rhabdovirus. Virus Genes 19, 59-65.
Skall, H.F., Olesen.
N.J., & Mellergaard, S. (2005). Viral haemorrhagic septicaemia virus in marine fish
and its implications for fish farming -- a review. Journal of Fish Diseases 28,
509-29.
Smail, D.A. (1999). Viral Haemorrhagic
Septicaemia. Pages 123-146 In Fish Diseases and Disorders, Volume 3,
Viral, bacterial, and fungal infections. P.T.K. Woo & D. W. Bruno,
eds. CAB International, New York.
Snow M., Bain N., Black J., Taupin V., Cunningham
C.O., King J.A., Skall H.F., & Raynard R.S. (2004). Genetic population
structure of marine viral haemorrhagic septicaemia virus (VHSV). Diseases of Aquatic Organisms 61,
11–21.
Tordo, N., Benmansour, A., Calisher, C., Dietzgen,
R.G., Fang, R-X, Jackson, A.O., Kurath, G., Nadin-Davis, S., Tesh, R.B., &
Walker, P. (2004). Family Rhabdoviridae, In "The eighth report
of the international committee for taxonomy of viruses". Academic
Press, San Diego.
Wolf, K. (1988). Infectious hematopoietic necrosis
virus. Pages 83-114 in Fish Viruses and Fish Viral Diseases. Cornell University
Press, Ithaca, New York.
Status of Finfish Culture and
Parasitic Diseases in China
Tingbao Yang*
Historical records of fish culture and parasitic diseases
Finfish culture has a
very long history in China, as common carp were raised for food in freshwater
ponds as early as 1,000 years BC. The fish parasites and their detrimental effects were were paid
attention to by ancient fish farmers, as recorded in the book “Jottings of
Interrelationship of Things” written by Shushi, a writer in the Song Dynasty
(960 – 1279). Sushi noted that the white spot on fish, called lice, could
be eliminated by casting the balk of willow. Although the parasite referred to
was probably not what we would refer to as lice today, we can however deduce
that the ancient fish farmers had realized the impact of fish parasites, and
tried to prevent and treat them. Subsequently, Xu GuangQi in the Ming Dynasty
(1368 – 1644), wrote in his book “Nongzheng Quanshu (Agricultural Pandect)”,
that poor conditions in the fish pond resulted in infection with lice, which
are as round and as big as a soybean (Zhang et al, 1999).
The total inland water area in China is
about 17,600,000 hectares, and of this about 5,642,000 hectares (approximately
one third) can be used for aquaculture. The total area of coastal seawater in
China is similar to that of freshwater, and the area suitable for mariculture
before 2001 was some 1,330,000 hectares (Lu, 2001). In 2007, the total area of
water in China that supports aquaculture was actually 5,633,210 hectares,
4,301,000 hectares of which were freshwater, and 1,331,000 hectares of which
were for mariculture (Kuan, 2008).
A remarkable development
in fisheries in China has happened in the past 60 years. In 1949, the total
annual fishery catch was only 524,000 metric tons, and within 30 years (1978)
the catch reached 5,366,100 metric tons, ten times that in 1949. In the last
two decades, due to the country’s economic opening to the world, and the
adjustment of the structure of fisheries, the total annual fishery production
in China rose
ten times again, to its 2008 value of 48,956,000 metric tons
(Zhou & Li, 2009).
Finfish culture in China
The finfish culture
environments in China are highly diverse, because of the high diversity of
topographic conditions and water environments; from tropical warm water in the
south of the country, to the cold water in the north of the country; from
freshwater rivers and ponds, to brackish lakes, ponds and estuary water, to
stable sea water sites far from the coast which are now gradually used for
large scale net culture.
Government efforts to support aquaculture
Central to the growth of
aquaculture in China was significant government investment, and the
conscientious efforts of scientists and the fish farmers. In 1950’s there was
only one research lab and several extension stations for aquaculture
technologies in the coastal provinces. Subsequently, the government established
three fishery institutes (Yellow Sea, East China Sea and South China Sea), two
institutes of oceanography belonging to the academy of sinica (Institute of
Oceanography in Qingdao, and South China Sea Institute of Oceanography in
Guangzhou) and three fisheries institutes for the major rivers (Yangze River,
Pearl River and Heilongjiang River), and every districts or county had its own
institute of fisheries or aquaculture. By 1987, there were 107 fishery research
institutes with 6,700 scientists and staff doing research on fisheries or
aquaculture. By 2008, there were 13,217 stations established for extending
fishery and aquaculture techniques. Most of the institutes were fully sponsored
by the central government (9,085), some were partially sponsored by the central
government (2,809), and the remainders were privately funded. In 2008, there
were a total of 36,887 people working in these extension stations (Zhou &
Li, 2009).
Important parasitic pathogens
in aquaculture in China
Although more than 90
species of parasites have been reported as pathogens causing diseases of
freshwater fishes, only around 30 species of them were frequently found from
the 26 species of fishes most commonly cultured on a large scale. Until 2008, a
total of 28 kinds of parasitic diseases of fishes (freshwater and marine
fishes) were included on the list of aquaculture pathogens for national
surveillance (internal data).
Impact of
current and emerging parasite diseases on finfish culture
Outbreaks of disease in
aquaculture is the main factor restraining production of high quality aquatic
products. Parasites are very dangerous to hosts in confined environments such
as the cultured pan and densely-stocked ponds.
Management:
practices and infrastructure affecting fish health
The management and
control of parasitic diseases in aquaculture in China generally include
pretreatment of culture facilities, quarantine, scientific management of
aquaculture systems, surveillance of diseases, chemical treatments of diseased
fish, use of Chinese herbal medicines, and ecological approaches to prevention
of parasite infections.
Introduced fish and introduced parasites
Global exchange and
species introductions in aquculture have become very frequent. To date, there
are some 35 species of fish introduced from over the world, that are now
cultured in China. In some areas, the introduced species, such as tilapia, Oreochromis spp. and red drum, Sciaenops ocellatus, have become the
dominant species, and are now in large scale culture. Their native parasites
have been observed in China, such as the monogenea Cichlidogyrus sclerosus and Scutogyrus
longicornis from gills of a hybrid tilapia of Orechromis aureus (S.) ♂ and Orechromis niloticus (Wu et al., 2006). The influence of both native parasites, and the novel
parasites introduced with the introduced host fishes, on the local parasite
fauna are worthy of thorough investigation and evaluation, to support the
sustainable culture and protection of locally relevant species of fishes.
Fish parasites of public health importance
Not only are parasites of
importance for fish health, but some are also of concern for public health. In
freshwater fishes, the trematode Clonorchis
sinensis is notorious for causing the human disease of clonorchiosis or
fascioliasis. This is an important trematode in the biliary passages and
occasionally the pancreatic duct, of humans and fish-eating mammals of the
Orient, chiefly Japan, Korea, China and Indo-China (Lun et al, 2005). Many
species of freshwater fishes can be infected by the cercaria of this
trematode. Humans become
infected by eating raw or undercooked fish such as sashimi, fish porridge,
where the metacercaria of trematodes are found. There are 22 of 34 provinces in
China where this disease occurs, and it is estimated that the total number of
infected people in China is about 16,480,000. Clonorchiosis can cause severe
liver damage, and 60% of the patients have the diagnostic symptom of
hepatomegaly and mild pressing pain.
Conclusions
and future outlook
Parasitic pathogens of
cultured fishes are numerous and have caused huge economic losses in China.
However, our knowledge about these pathogens is still very fragmented. Therefore,
forcasting techniques based on the life cycle and epidemiology of the
pathogens, and simple, precise and rapid dignostic techniques, are important
tasks for scientists.
Guo
Y.H. Qi J.W. & Bao H.M. (1995) Situation of studies on parasitic diseases
of fishes in China. Chinese Journal of
Veterinary Parasitology 3 (1): 59-61. (In Chinese)
Novel Discoveries on the
Immune System of Teleost Fish, and Their Impact Into the Future Development of
Mucosal Vaccines
2. DISCOVERY OF PHAGOCYTIC B LYMPHOCYTES IN FISH
2.2 B cells of
fish: Until
very recently, the little knowledge we had from fish B lymphocytes pointed to
the notion that these cells were essentially restricted to adaptive immunity
(5)
and that they resembled mammalian B-1 B cells, that is, they expressed
membrane IgM as a monomer and secreted soluble IgM as a polymer
(6, 7)
. However, we have
recently unearthed the existence of a novel B cell lineage in fish that
uniquely expresses surface IgT
(8)
, a teleost immunoglobulin that was identified 5 years ago
(9)
. Moreover, it appears that catfish contain a B cell subset that
expresses only IgD
(10)
, thus suggesting the existence of at least three different B cell
subsets in teleosts.
2.3 B
lymphocytes are active phagocytes in teleost fish: Up until recently, the dogma dictated that normal cells of
lymphoid origin (i.e., B cells, T cells) were not able to perform phagocytosis
(3)
. Contrary to this belief, recent studies in our laboratory have shown
that large subsets of trout IgM+ B cells are capable of efficient
phagocytosis
(11)
. In contrast T-cells and thrombocytes were devoid of such capacity.
Importantly, the phagocytic ability of trout IgM+ B cells was
enhanced by opsonization of bacteria with trout complement or IgM. After
particle internalization, trout IgM+ B cells were found to initiate
degradative pathways through phagolysosome formation. Significantly, phagocytic
B cells were found to have the capacity to effectively kill internalized
bacteria. We identified this phagocytic activity in the majority of IgM+ B
cells from trout and catfish blood, head kidney and peritoneal cavity. This
represented the first time that such phagocytic activity has been described in
normal B cells from any animal species. These findings were reported in Nature
Immunology
(11)
and made the cover of the 2006 October issue. Recent reports have
confirmed our finding in other fish, thus showing the presence of phagocytic B
cells in Atlantic salmon and cod
(17)
. Moreover, we have recently reported that the newly discovered IgT+ B cell lineage is also phagocytic and microbicidal
(8)
.
2.4
Significance for the area of fish health: The main role assigned up until recently to B
cells in fish was the secretion of antibodies (IgM) upon antigenic stimulation.
However, our new findings also point to a very important role of these cells in
innate immunity; more specifically, in the phagocytosis and killing of microbes
(11)
. We hypothesize that the capacity of fish B cells to ingest large
particles will also have an impact on adaptive immune processes such as those
related with the processing and presentation of the phagocytosed antigen.
Therefore this previously unanticipated and novel role of B cells in phagocytic
processes is likely to fundamentally change the way we view innate and adaptive
immunity in fish. From an applied
perspective, this finding has important implications for the design of fish
immunotherapeutics. In that regard, a
significant amount of research in fish immunotherapeutics is devoted to the
development of immunostimulants that can stimulate innate and/or adaptive
immune mechanisms
(18)
. Thus, one could envision the search of substances or compounds that
stimulate the phagocytic activity of fish B cells. On one hand, such substances
would be likely to stimulate innate immunity by enhancing microbe uptake and
killing, while on the other hand, adaptive immunity would be enhanced through
increased B-cell specific processes of antigen uptake and presentation. Another
area that we anticipate will greatly benefit from these findings relates to the
design of fish vaccines. Since a very large percentage of fish B cells are able
to ingest particles, we believe that particulate antigen-delivery systems in
fish would be more effective than those based on the delivery of soluble
antigens. Accordingly, one could foresee research on technologies that focus on
antigen-coating of particles that have been previously shown to be avidly
uptaken and phagocytosed by B cells. Thus, future research in that area may open an avenue for the development
of more effective fish vaccines based on particulate antigen-delivery systems
that target B cells, in addition to other known antigen presenting cells.
3. IGT, A TELEOST FISH IMMUNOGLOBULIN SPECIALIZED IN MUCOSAL IMMUNITY
While IgD-like molecules have been cloned in several
teleost species
(19, 27)
, its role in fish immunity is unclear.
3.2 Structural
and functional characterization of IgT: Up until recently, nothing was known about the
protein structure of IgT, and its distribution and production by putative B
cells. More importantly, its function was an enigma. This year we have reported
the structural and
functional characterization of IgT
(8)
. We have produced polyclonal and monoclonal antibodies against IgT
that have enabled us to identify and characterize IgT from different fish body
fluids. At the protein level we have shown that IgT is a monomeric
immunoglobulin in serum. However in the gut mucus, IgT is chiefly polymeric and
is more abundantly expressed than in serum. Importantly, we have also provided
direct evidence for the existence of a novel B cell lineage uniquely expressing
surface IgT. This new lineage represents the predominant B cell subset in the
gut-associated lymphoid tissue (GALT) of rainbow trout. More critically, our
functional studies have indicated that IgT behaves as a mucosal intestinal
immunoglobulin. Thus, we have shown that rainbow trout IgT responses against C. shasta, an intestinal parasite, were
only detected in the gut, whereas IgM responses were confined to serum. This finding
shows for the first time in a fish, a compartmentalized response of
immunoglobulin isotypes into mucosal and systemic areas in response to
pathogenic challenge: while IgM plays a predominant role in systemic responses,
IgT plays a dominant role in intestinal mucosal surfaces
(8)
.
One of the hallmarks of mucosal IgA in the gut of humans is its ability to coat a large percentage of luminal bacteria. This IgA coating plays a key role in immune exclusion at mucosal surfaces (28, 29), thus, the IgA-coated bacteria are prevented from attaching and invading the gut epithelium (28, 29). Similar to mammals, the lumen of fish contains high densities of bacteria (30). Supporting the role of IgT in mucosal immunity, we found that a majority of trout intestinal bacteria were found coated with IgT. Our findings collectively point to the first reported non-tetrapod immunoglobulin specialized in mucosal immunity. These findings have recently been published in the 2010, September issue of Nature Immunology (8) and they have made its cover.
3.3
Significance for the area of fish health: From an applied
perspective, our findings are expected to have a profound impact in the
area of fish health and vaccinology. In that regard, IgM has been considered up
until now, the only functional immunoglobulin in teleost fish. Our findings challenge this current view since we show that
teleost fish contain not one, but two functional immunoglobulins IgM and IgT
that respond to pathogenic challenge. Significantly, all studies carried out in teleost fish during the last
few decades have missed to examine the specific contribution of IgT in
protecting fish. Thus, our new capability of measuring not only IgM but also
IgT responses, will greatly facilitate the evaluation and understanding of fish
immune responses as well as the protective effects of fish vaccines. Consequently,
this new knowledge is likely to influence the future design of more efficacious
fish vaccine formulations that not only stimulate systemic (IgM responses), but
also mucosal immunity (IgT responses).
4. ACKNOWLEDGMENTS
This work
was supported by the National Science Foundation (NSF-MCB-0719599 to J.O.S.),
and the United States Department of Agriculture (USDA-NRI 2006-01619 and
USDA-NRI 2007-01719 to J.O.S.).
5.
REFERENCES
1. Desjardins, M., M. Houde,
and E. Gagnon. 2005. Phagocytosis: the convoluted way from nutrition to
adaptive immunity. Immunol Rev 207:158-165.
21. Warr, G. W. 1997. The
adaptive immune system of fish. Dev Biol
Stand 90:15-21.
Infectious Salmon Anemia in the Chilean
Salmon Farming Industry: Origins and Impacts
Alicia Gallardo Lagno*
General Background. Infectious Salmon Anemia (ISA) is a
disease caused by an RNA virus belonging to the family Orthomyxoviridae. It
mainly affects Atlantic salmon (Salmo
salar). The ISA virus was
first diagnosed in Norway in 1984; later the infection was confirmed in New
Brunswick, Canada (1996), Scotland (1998), USA (2000) and the Faroe Islands
(2000). In all these countries, outbreaks of ISA have caused serious economic
losses due to high mortalities, and the culling of sick animals at affected
sites.
Surveillance and control actions. As control measures, the National Fisheries
Service (Sernapesca), established in August 2007, a specific program of surveillance
and control of caligidosis. As a
result of the program, prevalence was determined to be close to 90% in salmon
farms and sea estuaries. Within
this program of parasite control, Sernapesca promoted the medicated baths
(pyrethroid, deltamethrin), which added to oral treatments using benzoate
emamectin. During the first stage
of implementation of the program, loads were reduced by 50%. In addition, after the outbreak,
Sernapesca established a contingency plan based on existing ISA programs in other
countries. In 2008, the following
regulations were implemented:
• Additional and complementary measures
concerning the importation of eggs.
• Establishment of a technical standard
for solid waste management and plant effluent disinfection process fish salmon
fishing from areas quarantined for ISA.
• Implementation of a
formal system of controlled export by implemented by issuing a health
certificate (given previous analysis ISAV negative.)
Results of the ISA Surveillance Program. The incidence of ISAV
from sea farms peaked in 2008, and then decreased in 2009 and 2010. The decline was associated with the
elimination of infective cages, and eliminating susceptible individuals. Freshwater (lake) monitoring revealed
the presence of viral genome compatible with the ISA virus in breeding farms
rearing fry and smolts. Although
these specimens did not show the disease, they were eliminated as a precautionary
measure, since you do not know their real impact on the epidemiology of the
disease, potentially coming from the eggs of positive individuals. To date, there are no outbreaks of
disease and the variant of the predominant virus is avirulent (HPR0) in both
freshwater (breeding) and sea.
Conclusions. According to the
history of the cases reviewed during surveillance, Infectious Salmon Anemia is
regarded as prevalent in southern Chile. With an understanding of the stressors that exist for farmed salmon, is
expected that new cases of the disease will be observed in different regions,
based on the experience of other countries regarding the behavior of this
disease.
Short and Long Term Implications for Ecosystem Health in the North Central Gulf of Mexico following the Deepwater Horizon Oil Spill
George
Crozier*
From the continued exploitation of these ecosystem services provided by the Gulf of Mexico have come a number of human-induced challenges to the ecological health of the Fertile Crescent. The persistent cumulative impacts of these anthropogenic insults have brought many to hypothesize that the Gulf of Mexico has been brought to a tipping point in which much of the what the Gulf of Mexico once provided in abundance could be lost if additional perturbations are added to this already stressed ecosystem.
Situation and
Need
On April 22, 2010, the semi-submersible drill platform Deepwater Horizon sank in nearly 1,200 m of water in the northern Gulf of Mexico. After several attempts to close a failed blowout preventer valve, it became clear that estimates of 600 m3 (with unofficial estimates as high as 4,000 m3) of oil were being released each day. Pre-approval of chemical dispersants (CorexitTM) was made based on knowledge of the dispersant application over limited areas and for limited time at the sea surface. However, in this case, an unprecedented volume of dispersant has been applied both at the surface and through direct injection into the wellhead leak at 1,200 m depth. While (primarily) Federal agencies (NOAA, EPA, USCG/DHS) are seeking rapid answers to the toxicities of the dispersants used at these concentrations, with duration and depth constructs considered, emphasis is now focused on discerning how the dispersants impact finfish, shellfish, turtle and bird safety and health. (http://www.noaanews.noaa.gov/stories2010/20100511_sciencechief.html)
Moreover, reactive dispersants are held as trade secrets, though generally these have both solvent and surfactant fractions known to carry toxicity. To date there is no plan for understanding functional ecosystem shifts as a consequence of this magnitude of application of dispersants or the resulting re-distribution of oil or released compounds within the water column.
At this moment, we should be more impressed by what we don’t know than what we do know. Improved documentation and understanding of the physical and chemical impacts of unintended release and dispersal of oil and natural gases, along with the currently employed management strategy of applying chemical dispersants to reduce the areal extent of the oil slicks, is key to achieving a balance between the need to effectively manage our nations dwindling coastal resources and the need to meet the petroleum-based requirements of our nations recovering economy.
The “incident” was initially described with the terms “pre-spill” and “post-spill” but the duration was of such great length that the process of assessing impacts became much more complicated. The chaotic nature of the incident itself was almost overshadowed by the unprecedented interplay between the federal government, local government and BP as the “Responsible Party.” The predictable hysteria generated by the “abundance of enthusiasm” from the media, globally, exacerbated all impacts, particularly in the human dimension of the coastal communities associated with the region bounded by the Mississippi River mouth and Cape San Blas to the East.
