Survivors can be carriers.
Hobbyists and dealers can help protect themselves by:
Starting in the Spring of 2007, a course with more current and complete information and presented by very competent instructors will be made available through the sponsorship of AKCA's Project KHV (see announcements in July/Aug '06 and Sept/Oct '06 issues of KOI USA). This fact sheet was assembled to help bridge the gap between then and now.
First found in Israel in May 1998 (Hedrick, et al., 1999)
First found in the U.S. in fish from the East Coast in August, 1998 (Hedrick et al., 2000)
Virus first isolated and partially characterized in 2000 (Hedrick et al., 2000)
First PCR tests developed in 2002, Gilad and Gray produced different primers (Gilad et al., 2002 and Gray et al., 2002)
Has been found in most countries in the world where koi and/or carp are commonly raised or kept - (Pokorova, et al., 2005)
Others resist the classification as a herpesvirus and prefer the designation CNGV. (Dishon, et al., 2005)
Is highly contagious and can produce high (80% to nearly 100%) mortality in diseased populations of koi and common carp (Dishon et al., 2005)
Appears to cause disease and mortalities only in common carp and koi but the virus can also infect goldfish and crucian carp (Haenen et al., 2006 -Bergmann & Tinman presentations)
Infections are transmitted via virus in the water, in fecal material, in sediments and from fish to fish (Dishon et al., 2005; Hartman, et al. 2004)
The route of infection into the fish is likely thru the gills (Dishon et al. 2005) and the gut (Haenen et al., 2006 - Bergmann presentation)
Propagates mainly in intestine and kidney of infected fish (Dishon et al., 2005)
Deaths can start within 1 to 2 days following the onset of clinical signs (Hartman et al., 2004)
Infected fish usually die within 6 to 24 days (post infection) at permissive temperatures (Dishon et al., 2005)
Permissive temperatures are variously reported as 17-26°C; 18-27°C; 18-25°C; 22-26° C and 18-28°C (Haenen et al., 2004; Hartman et al., 2004; Ronen, et al., 2003; Perelberg et al., 2003 & Haimi, 2003 [plus several others], respectively)
Temperature ranges for optimum virus growth in cell cultures tend to be 2-3° C wider than those in fish (Gilad et al., 2003).
Can produce latency and/or a persistent low-level infection such that survivors can later become infectious (St-Hilaire et al., 2005)
Can survive off the fish for weeks, probably in sediments and/or filters (Haenen et al., 2006 -Bergmann presentations)
Survives in water for 4 hours but less than 18 hours (Perelberg et al., 2003)
Clinical signs seem to be arrested at >30° C and fish raised to this temperature can often survive the disease (Ronen et al., 2003)
Clinical signs seem to be arrested at <13° C (Hedrick et al., 2005)
Does not appear to cause disease at or below 13° C (55° F) - (Gilad et al., 2003)
Antibodies have been found in survivors up to a year post infection (Haenen et al., 2006 -Dixon presentation)
Virus found up to 7 months post infection in the base of the gills, the kidney, the spleen and the leukocytes (Haenen et al., 2006 - Bergmann presentation)
The entire viral genome has been sequenced (Haenen et al., 2006 - Aoki presentation)
There are several different strains (mutations) of the virus (Haenen et al., 2006 - Ito presentation)
There is no zoonotic concern with KHV. (Hartman et al., 2004; Southard et al., 2006)
Disease symptoms: (Hartman, et al., 2004; Goodwin, 2003; Groff, 1999- pers. comm.)
Not all diseased fish exhibit all symptoms
Pale and necrotic gills (gill rot) is the most common symptom - see Figure 1
Figure 1. Necrotic gills
(Photo by Duncan Griffiths)
Hyperplastic gills observed with or w/o bacterial infection (gill rot)
Lethargy and "hanging" in the water toward the end-stage of the disease
A notch in the "nose" of the fish - see Figure 2
Figure 2. Notch in "nose" (see arrow)
(Photo by Jeff Nicholson)
Heavy mucus at the start of disease
Lack of mucus later as disease progresses - skin feels like sandpaper
Patches of discolored skin
Group contains symptomatic koi and/or carp but other species show no symptoms
Testing - availability and tissues for sampling (partial listing):
KHV typically found in the kidneys first and longest over the course of the active disease so good tissue to test
Gills, spleen, fins and gut are also good tissue to test if the disease is suspected
PCR tests for viral DNA - commercially available (fee-for-service) in the US (TX, GA, FL, WA), Japan, UK, Germany, Israel as well as other countries
Serology tests for antibodies - commercially available in US (GA), UK (CEFAS), Israel
Histopathology - commercially available in US (GA)
Virus Isolation (in cell culture) - commercially available in US (GA)
ELISA tests for virus - not currently commercially available in US
ELISA test for antibodies to KHV - in US (UC Davis) and commercially in UK (CEFAS) and Israel
LAMP test for DNA - not currently commercially available in US, avail in UK
Tissue samples (e.g., gill, kidney, etc.) may be placed in rubbing alcohol (70% or 90%) for later PCR testing - (Goodwin, 2005- pers. comm.)
Droppings of infected fish have been shown to contain KHV that can be detected by PCR testing (Dishon, et al., 2005)
Cloacal swabs may be submitted to some labs for PCR testing (KHV DNA) - Dacron-tipped swabs are preferred over cotton-tipped swabs (Q-tips), (Colaizzi, 2006- pers. comm.)
If and where the virus exists for long periods when in the environment (outside the fish)
Testing that can determine if a specific fish carries the (internal) potential to become diseased or infectious (even if it "passes" quarantine), i.e., a test to determine latency
If there is a safe and effective way to rid latent or persistently infected fish of the virus or the potential to become infective
If there is a vaccine possible that will confer long term protection against KHV
An effective field test for KHV
An effective field test for KHV antibodies
If there is vertical transmission
Quarantine all new fish, and those returning to the facility, at 70° F to 75° F for at least three weeks.
Adding SPF (KHV naïve) fish to the quarantine group is probably helpful as naïve fish are more likely so show disease symptoms (Haenen et al., 2004)
Observe fish in quarantine system noting symptoms and behaviors, particularly those typical of KHV - see "Disease symptoms" in this fact sheet.
Use separate equipment to house and handle quarantined fish.
Thoroughly disinfect equipment if it is used between systems and/or between separate lots of fish.
Serology or antibody testing during quarantine can determine if fish have been exposed to KHV and/or a KHV simulating antigen (as in a vaccine) and have developed antibodies to the virus. This could identify potential carrier fish or it could simply indicate that a fish has been successfully vaccinated. Knowing the fish's history would be helpful in this event. Having a "marker" in the vaccine would be even better.
Disinfection of holding facilities and fish handling equipment may be accomplished using:
Care should be taken that disinfecting solutions are clean and active. Replace as necessary.
If KHV is confirmed, depopulation (killing all the infected and exposed fish) should be considered as carriers may exist in any survivors.
There are currently 6 groups reported to be working on vaccines for KHV. Immunizing "agents" are reported to include killed-virus, attenuated-live virus and DNA. Delivery techniques include oral, immersion and injectable. The groups include:
Koi Health Advisors
Antibodies - proteins produced by the immune system to fight specific bacteria, viruses, or other antigens.
Antigen - substance capable of inducing an immune response.
Base pairs (relative to DNA) - Pairs of complementary nitrogenous bases that interact to form the rungs of DNA's double helix "ladder" structure. Adenine (A) pairs with thymine (T); cytosine (C) pairs with guanine (G).
Benzalkonium chloride (alkyl dimethyl benzyl ammonium chloride) - an organic compound used as a disinfectant.
Cloaca - an organ into which an animal's digestive, urinary and reproductive systems empty, and that opens to the anus.
CNGV - carp interstitial nephritis and gill necrosis virus, a designation for the virus preferred by some in the scientific community.
Disease - an impairment of health or a condition of abnormal functioning.
Disinfection - the effective elimination of disease causing organisms.
DNA - deoxyribonucleic acid, the material inside the nucleus of cells that carries genetic information.
ELISA - Enzyme-Linked Immunosorbent Assay, a widely used immunochemical method for detecting antigens or antibodies. ELISA methods are carried out in microtitre plates and use colorimetric detection.
Genome - the complete set of genetic information of an organism including DNA and RNA.
Histology - the study of cells and tissue on the microscopic level.
Hyperplasia - an increase in the number of cells in a tissue or organ, excluding tumor formation.
Infect - to invade with a foreign organism, typically a pathogen.
Iodophor - a substance consisting of iodine and a solubilizing agent that releases free iodine when in solution.
Kilo base pairs - thousands of base pairs
Koi Health Advisor (KHA) - a koi hobbyists that has completed the training and continuing education required by the AKCA's KHA Program.
KHV - koi herpesvirus, the virus that causes KHV disease.
LAMP - Loop-mediated isothermal amplification is a test for DNA.
Latency (with regard to viral infections) - a dormant disease that can later become infective.
PCR - polymerase chain reaction; a technique for amplifying DNA, making it easier to isolate, clone and sequence.
Permissive temperatures - temperatures at which KHV disease is typically observed in fish.
Project KHV - an AKCA committee formed to solicit funding to support KHV research and education. see: http://www.akcaprojectkhv.org/index.htm
Quarantine: forced isolation
Quaternary ammonia compounds -disinfectants (e.g., benzalkonium chloride and Roccal ® )
SPF - specific pathogen free - in this context, meaning free of KHV infection or exposure, i.e., naïve to KHV
Serology - the branch of science dealing with the measurement and characterization of antibodies and other immunological substances in body fluids, particularly serum.
Serum - The clear liquid part of the blood that remains after blood cells and clotting proteins have been removed.
Vertical transmission - disease passed from parent to offspring through eggs or sperm.
Virus - a small particle that infects cells in biological organisms. Viruses are obligate intracellular parasites; they can reproduce only by invading and taking over other cells as they lack the cellular machinery for self reproduction.
Zoonosis - An infection or infestation shared in nature by humans and other animals that are the normal or usual host; a disease of humans acquired from an animal source.
Colaizzi E (2006) - Research Associates Laboratory, Dallas , TX .
Dishon A, Perelberg A, Bishara-Shieban J, Ilouze M, Davidovich M, Werker S, Kotler M (2005) Detection of Carp Interstitial Nephritis and Gill Necrosis Virus in Fish Droppings. Applied Environmental Microbiology 71(11):7285-7291.
Gilad O, Yun S, Andree KB, Adkison MA, Zlotkin A, Bercovier H, Eldar A, Hedrick RP (2002) Initial characteristics of koi herpesvirus and development of a polymerase chain reaction assay to detect the virus in koi, Cyprinus carpio koi. Diseases of Aquatic Organisms. 48:101-108.
Gilad O, Yun S, Adkison MA, Way K, Willits NH, Bercovier H, Hedrick RP (2003) Molecular comparison of isolates of an emerging fish pathogen, koi herpesvirus, and the effect of water temperature on mortality of experimentally infected koi. Journal of General Virology, 84: 2661-2668.
Goodwin A (2003) Differential Diagnosis: SVC vs. KHV in Koi. Fish Health Newsletter, AFH/FHS. 31: 1, 9-13.
Gray WL, Mullis L, LaPatra SE, Groff JM, Goodwin A (2002) Detection of koi herpesvirus DNA in tissue of infected fish. Journal of Fish Disease, 25:171-178.
Groff J (1999) - University California at Davis, CA
Haenen OLM, Way K, Bergmann SM, Ariel E (2004) The emergence of koi herpesvirus and its significance to European aquaculture. Bull. Eur. Ass. Fish Pathol., 24(6): 293-307.
Haenen O, Hedrick R (2006) Koi herpesvirus workshop. Bull. Eur. Ass. Fish Pathol., 26(1):26-37.
Haimi M, (2003), Lecture H3: "KHV Practical information?" - MAG NOY, Israel.
Hartman KH, Yanong RPE, Petty BD, Francis-Floyd R, Riggs AC (2004) Koi Herpes Virus (KHV) Disease, Univ. FL, IFAS Exten. Fact Sheet VM-149.
Hedrick RP, Marty GD, Nordhausen RW, Kebus M, Bercovier H, Eldar A (1999) A herpesvirus associated with mass mortality of juvenile and adult koi, Cyprinus carpio. Fish Health Newsletter, Fish Health Section, American Fisheries Society 27:7.
Hedrick RP, Gilad O, Yun S, Spangenberg JV, Marty GD, Nordhausen RW, Kebus MJ, Bercovier H, Eldar A (2000) A herpesvirus associated with mass mortality of juvenile and adult koi, a strain of common carp. Journal of Aquatic Animal Health, 12:44-57.
Hedrick, RP, Gilad O, Yun SC, McDowell TS, Waltzek TB, Kelly GO, Adkinson MA (2005) Initial Isolation and Characterization of a Herpes-like Virus (KHV) from Koi and Common Carp. Bulletin of Research Fisheries Agency, Supplement No. 2, Special issue: International Symposium on Koi Herpesvirus Disease, pp 1-7.
Herwig N (1979) Handbook of Drugs and Chemicals Used in the Treatment of Fish Diseases, Charles C. Thomas, Springfield, IL. p 192.
Noga, EJ (1996) Fish Diseases: Diagnosis and Treatment, Mosby-Yearbook, Inc. St. Louis, MO. p 281.
Pokorova, D, Vesely T, Piackova V, Reschova S, Hulova J (2005). Current knowledge on koi herpesvirus (KHV): a review. Vet. Med. - Czech, 50, 2005 (4):139-147.
Ronen A, Perelberg A, Abramowitz J, Hutoran M, Tinman S, Bejerano I, Steinitz M, Kotler M (2003) Efficient vaccine against the virus causing a lethal disease in cultured Cyprinus carpio. Vaccine 21: 4677-4684.
Saint-Erne N (2002) Advanced Koi Care, Erne Enterprises, Glendale, AZ. p160.
Southard GM, Fries TL (2006)
First Report of Koi herpesvirus in Texas.
Archive Number: 20060707.1867
St-Hilaire S, Beevers N, Way K, Le Deuff RM, Martin P, Joiner C (2005) Reactivation of koi herpesvirus infection in common carp Cyprinus carpio. Diseases of Aquatic Organisms, Vol. 67: 15-23.
Waltzek TB, Kelley GO, Stone DM, Way K, Hanson L, Fukuda H, Hirono I, Aoki T, Davison AJ, Hedrick RP (2005) Koi herpesvirus represents a third cyprinid herpesvirus (CyHV-3) in the family Herpesviridae. Journal of General Virology 86:1659-1667.
Way K., Beevers ND, Joiner CL, Longshaw CB, St-Hilaire S (2004). Koi herpesvirus in the UK: Detection in archive tissue samples and spread of the virus to wild carp. Abstract 6 th International Symposium on Viruses of Lower Vertebrates, Hakodate, Japan, Sept. 2004