Category Archives: Disease Prevention

FAO issues alert over lethal virus affecting popular tilapia fish

Though not a human health risk, Tilapia Lake Virus has large potential impact on global food security and nutrition

26 May 2017, Rome–A highly contagious disease is spreading among farmed and wild tilapia, one of the world’s most important fish for human consumption.

The outbreak should be treated with concern and countries importing tilapias should take appropriate risk-management measures – intensifying diagnostics testing, enforcing health certificates, deploying quarantine measures and developing contingency plans – according to a Special Alert released today by FAO’s Global Information and Early Warnings System.

Tilapia Lake Virus (TiLV) has now been reported in five countries on three continents: Colombia, Ecuador, Egypt, Israel and Thailand.

While the pathogen poses no public health concern, it can decimate infected populations. In 2015, world tilapia production, from both aquaculture and capture, amounted to 6.4 million tonnes, with an estimated value of USD 9.8 billion, and worldwide trade was valued at USD1.8 billion. The fish is a mainstay of global food security and nutrition, GIEWS said.

Joyce Makaka tends her FAO-assisted fish farm in western Kenya.

Joyce Makaka tends her FAO-assisted fish farm in western Kenya.

Tilapia producing countries need to be vigilant, and should follow aquatic animal-health code protocols of the World Organisation for Animal Health (OIE) when trading tilapia. They should initiate an active surveillance programme to determine the presence or absence of TiLV, the geographic extent of the infection and identify risk factors that may help contain it.

Countries are encouraged also to launch public information campaigns to advise aquaculturists – many of them smallholders – of TiLV’s clinical signs and the economic and social risks it poses and the need to flag large-scale mortalities to biosecurity authorities.

Currently, actively TiLV surveillance is being conducted in China, India, Indonesia and it is planned to start in the Philippines. In Israel, an epidemiological retrospective survey is expected to determine factors influencing low survival rates and overall mortalities including relative importance of TiLV. In addition, a private company is currently working on the development of live attenuated vaccine for TiLV.

It is not currently known whether the disease can be transmitted via frozen tilapia products, but “it is likely that TiLV may have a wider distribution than is known today and its threat to tilapia farming at the global level is significant,” GIEWS said in its alert.

FAO will continue to monitor TiLV, work with governments and development partners and search for resources that can be explored in order to assist FAO member countries to deal with TiLV, as requested and as necessary.

The disease

There are many knowledge gaps linked to TiLV.

More research is required to determine whether TiLV is carried by non-tilapine species and other organisms such as piscivorous birds and mammals, and whether it can be transmitted through frozen tilapia products.

The disease shows highly variable mortality, with outbreaks in Thailand triggering the deaths of up to 90 percent of stocks. Infected fish often show loss of appetite, slow movements, dermal lesions and ulcers, ocular abnormalities, and opacity of lens.As a reliable diagnostic test for TiLV is available, it should be applied to rule out TiLV as the causal agent of unexplained mortalities.

TiLV belongs to the Orthomyxoviridae family of viruses, which is also the same family to which the Infectious Salmon Anaemia virus belongs, which wrought great damage on the salmon farming industry.

In May 2017, The Network of Aquaculture Centres in Asia-Pacific (NACA) released a TiLV Disease Advisory and the World Organisation for Animal Health (OIE) released a Disease Card. The WorldFish Center also released a Factsheet: TiLV: what to know and do, this month.

The importance of tilapia

Tilapias are the second most important aquaculture species in volume termsproviding food, jobs and domestic and export earnings for millions of people, including many smallholders.

Their affordable price, omnivorous diet, tolerance to high-density farming methods and usually strong resistance to disease makes them an important protein source, especially in developing countries and for poorer consumers.

China, Indonesia and Egypt are the three leading aquaculture producers of tilapia, a fish deemed to have great potential for expansion in sub-Saharan Africa.

Contact

Christopher Emsden
FAO Media Relations (Rome)
(+39) 06 570 53291
christopher.emsden@fao.org

 

Tilapia lake virus (TiLV): What to know and do?

Tilapia lake virus is a newly emerging virus that is associated with significant mortalities in farmed tilapia. With cases reported across Africa, Asia and South America, the virus represents a huge risk to the USD 7.5 billion global tilapia industry. All countries with a tilapia industry must be vigilant and act quickly to investigate cases of mortalities in farm.
Published by the CGIAR Research Program on Fish Agri-food Systems.

Scientists identify tilapia lake virus in Egypt

A new virus that has decimated tilapia populations in Ecuador and Israel has now been found in Egypt according to a new report from WorldFish in partnership with the University of Stirling, Scotland. Scientists are now trying to establish a firm link between the virus and a recent surge in mortalities in Egyptian farmed tilapia.

Tilapia Lake Virus (TiLV) is a global threat to the tilapia farming industry worth US$7.5bn per year.

In recent years fish farms in Egypt have seen increased mortality of farmed tilapia in the summer months, so-called “summer mortality”. Epidemiological surveys indicated that 37% of fish farms were affected in 2015 with an average mortality rate of 9.2% and an estimated economic impact of around US$100 million/year.

Identifying the cause of and preventing these fish deaths is of significant importance in Egypt, which relies on domestic aquaculture for 60% of fish consumed with tilapia making up 75% of that production. Tilapia is the cheapest form of animal protein in the country, so the findings have significant implications for the Egyptian people, particularly poorer consumers. The Egyptian aquaculture sector is the largest producer of farmed fish in Africa (1.17 million tonnes in 2015) and the third largest global producer of farmed tilapia after China and Indonesia.

Tissue samples from seven farms affected by ‘summer mortality’ were tested at the University of Stirling’s Institute of Aquaculture for TiLV with three of the seven samples testing positive.

Dr Michael Phillips, Director of Science and Aquaculture, WorldFish: “Tilapia were previously considered to have good disease resistance. While the report and the emergence of TiLV will likely not dent the species’ significance in global aquaculture it is a sign that greater efforts must be made to manage disease risks in tilapia farming. Research now needs to focus on finding solutions for this emerging challenge to the world’s tilapia farms.”

“Globally, there is no aquaculture system that is free from the risk of disease,” explains virologist Professor Manfred Weidmann from the University of Stirling. “Unless we are able to manage disease, minimize its impact, and bring down the prevalence and incidence of diseases we will not be able to meet future demand for fish.”

WorldFish scientists in collaboration with the University of Stirling will now work to establish whether TiLV is the primary cause of ‘summer mortality’ and, if that is the case, recommend rapid action to control the spread of the disease, including increased biosecurity in the short term. Longer-term strategies being studied by WorldFish and partners include vaccines and the genetics of disease resistance, that may open the way towards breeding of strains of tilapia that are resilient to TiLV.

Tilapia is an important species for aquaculture because it can be grown in diverse farming systems and is omnivorous, requiring minimal fishmeal in its feed. It has a naturally high tolerance to variable water quality and can grow in both freshwater and brackishwater environments. Tilapia are particularly important in developing world contexts where they are inexpensive and easy for small-scale farmers to grow for food, nutrition and income.

About WorldFish
WorldFish is an international, nonprofit research organization that harnesses the potential of fisheries and aquaculture to reduce hunger and poverty. Globally, more than one billion poor people obtain most of their animal protein from fish and 800 million depend on fisheries and aquaculture for their livelihoods. WorldFish is a member of CGIAR, a global research partnership for a food-secure future.

About CGIAR
CGIAR is a global research partnership for a food-secure future. Its science is carried out by the 15 research Centers that are members of the CGIAR Consortium in collaboration with hundreds of partners.

University of Stirling
The University of Stirling is ranked fifth in Scotland and 40th in the UK for research intensity in the 2014 Research Excellence Framework. Stirling is committed to providing education with a purpose and carrying out research which has a positive impact on communities across the globe – addressing real issues, providing solutions and helping to shape society.

Scientists net virus behind tilapia die-offs in Israel and Ecuador

An international scientific team led by researchers at Columbia University’s Mailman School of Public Health and Tel Aviv University has identified and characterized a novel virus behind massive die-offs of farmed tilapia in Israel and Ecuador, which threatens the $7.5 billion global tilapia industry. A paper in the journal mBio describes tilapia lake virus (TiLV) and provides information needed to fight the outbreak.

Known in its native Middle East as St. Peter’s fish and thought to be the biblical fish that fed multitudes, tilapia provides inexpensive dietary protein. The world’s second most farmed fish, tilapia is also the basis of aquaculture employment in developing countries in Asia, Latin America, and the Middle East. (The United States is the leading tilapia importer globally.) Since 2009, Israel has seen precipitous declines in tilapia, with annual yields plummeting as much as 85 percent–highly unusual considering the fish is known to be relatively resistant to viral infections. Similar die-offs have been seen in Ecuador and Colombia.

Diseased tilapia

Tilapia diseased from tilapia lake virus infection, Ecuador. Photo: Hugh Ferguson.

The scientists used high-throughput sequencing to determine the genetic code of the virus from tissue taken from diseased fish in Israel and Ecuador. This process would normally be sufficient to identify the culprit, but in this case, the resulting DNA sequences didn’t match any known virus, with the exception of a small genetic segment, that only remotely resembled a virus associated with the reproduction of influenza C.

Undeterred, the researchers employed other tools from their scientific tackle box, providing ample evidence that the genetic material was the same as the implicated virus dubbed TiLV. They used mass spectroscopy to characterize the proteins in cells growing the virus, which matched those they expected to see based on the genetic sequence. By analyzing the structure of viral DNA, they went on to observe 10 gene clusters with complementary endpoints, suggesting a circular form associated with a common type of viral reproduction involving a protein called a polymerase.

Finally and conclusively, healthy fish were exposed to TiLV cultured in a laboratory, resulting in disease that matched with what was seen in those countries: in Israel, the fish had swollen brains; in Ecuador, liver disease. In the coming weeks, the researchers will publish on the link between the TiLV and an outbreak of disease among tilapia in Colombia.

“The TiLV sequence has only minimal similarity in a small region of its genome to other viruses; thus, the methods we typically use to identify and characterize viruses through sequencing alone were insufficient,” says first author Eran Bacharach, a molecular virologist at Tel Aviv University.

“It appears to be most closely related to a family of influenza viruses called orthomyxoviruses; however, we still don’t understand much about its biology,” adds Nischay Mishra, associate research scientist at the Center for Infection and Immunity at Columbia’s Mailman School.

Importantly, the findings provide the genomic and protein sequences necessary for TiLV detection, containment, and vaccine development.

“We are shifting our focus now to implementing diagnostic tests for containment of infection and to developing vaccines to prevent disease,” says Avi Eldar of the Kimron Veterinary Institute in Bet Dagan, Israel.

The team of 18 researchers represent five institutions in four countries: the Center for Infection and Immunity and the New York Genome Center in the U.S., Tel Aviv University and Kimron Veterinary Institute in Israel; the University of Edinburgh, Scotland; and St. George’s University, Grenada, West Indies.

“The New York Genome Center was excited to join in characterizing this novel virus and contribute to this important environmental and globally impactful research,” says Toby Bloom, the Center’s deputy scientific director.

“Gumshoe epidemiology, molecular gymnastics and classical microbiological methods were required to link this new virus to disease,” says Ian Lipkin, senior author, director of the Center for Infection and Immunity and John Snow Professor of Epidemiology at the Mailman School. “Resolution of this mystery was only possible through the concerted efforts of this talented group of international collaborators.”

While best known for identifying viruses behind human disease, the Center for Infection and Immunity, pinpointed the virus beyond a disease that decimated salmon farms in Europe in 2010. They have done similar work with seals, sea lions, and Great Apes.

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The current research was supported by grants from the United States-Israel Bi-National Agricultural Research & Development Fund (BARD IS-4583-13), the Israel Ministry of Agriculture & Rural Development Chief Scientist Office (847-0389-14), U.S. National Institutes for Health (AI109761), USAID PREDICT, and a fellowship to J.E.K.T. from the Manna Center Program in Food Safety and Security at Tel Aviv University. The authors declare no conflicts.

Aquaculture Symposium to Focus on Infectious Diseases of Tilapia & Strip Catfish

Aquaculture Symposium taking place on 24 of March all day at Meeting Room 2 (3rd floor) of SECC in Ho Chi Minh City Vietnam which focus on Infectious diseases of Tilapia & Strip catfish invite 4 Fisheries experts from Veterinary Pathobiology, Faculty of Veterinary Science, Chulalongkorn University Bangkok, Thailand and the specialist in Tilapia from Vietnam to join the session.

The interesting topics are Franciscellosis, Streptococcosis, Columnaris disease in Tilapia and Strip catfish and Concurrent infection & Miscellaneous diseases, Antibiotic resistance in Aquaculture, Vaccine for Tilapia and Strip catfish and close session with Viral Nervous necrosis in Tilapia. This class is special for fish farmer to understand and study how to solve the infectious diseases of Tilapia and strip catfish in Vietnam. FAVA believe that this class will create the valuable knowledge for all delegate and the 120 seats are limited.

All conference program, please visit here

For more information of ILDEX Vietnam 2016, please visit www.ILDEX-VIETNAM.com