What are the signs and symptoms of KHV?

Diseased fish become lazy and disoriented, and remain near the water surface prior to death. Among many symptoms, gill necrosis is the most common clinic sign could be noted as early as 2 days after infection and becomes more evident after 6 days and beyond. Other clinical symptoms include sunken eyes, pale patches on skin and gill (See figure 3 and 4). Mucus secretions increase at the early stages, but decrease as the disease progresses. However, all these signs are not specific to the KHV disease. Furthermore, diseased fish are vulnerable to secondary infections caused by parasites and bacteria. These often worsen the fish’s sickness and alter the symptoms, leading to a misdiagnosis.

Figure 3: Patches on the skin


Figure 4: Patches on the skin


(You can see picturs of gill necrosis and sunken eyes in http://koiclubsandiego.org/library/khv/)

Internal lesions and damages can be found in many organs such as the gills, kidneys, spleen, liver and the gastrointestinal system. The earliest and most prominent changes usually concentrate in gills and kidneys though. Gilad et al. claimed that viral DNA can be detected in various tissues as early as 1 day post virus exposure with real-time TagMan PCR assay.



Bibliography

Gilad O., Yun S., Zagmutt-Vergara F.J., Leutenegger C.M., Bercovier H., Hedrick R.P. (2004), Concentrations of a Koi herpesvirus (KHV) in tissues of experimentally infected Cyprinus carpio koi as assessed by real-time TaqMan PCR. Dis Aquat Org, vol. 60(3), 179–187

Gray W.L., Mullis L., LaPatra S.E., Groff J.M., and Goodwin A. (2002), Detection of koi herpesvirus DNA in tissues of infected fish. Journal of Fish Diseases, vol. 25, 171-178

Hartman K.H., Yanong R.P.E., Pouder D.B., Petty B.D. Francis-Floyd R., and Riggs A.C. (2004). Koi herpesvirus (KHV) disease, Fact sheet VM-149, Extension service, Institute of Food and Agricultural Sciences, University of Florida 2004

Hedrick R. P., Marty G. D., Nordhausen R.W., Kebus M. J., Bercovier H., Eldar A. (2000), An herpesvirus associated with mass mortality of juvenile and adult koi Cyprinus carpio. Fish, Health Newsletter, Fish Health Section, American Fisheries Society, vol.12 (1), 44-57

Ilouze M., Dishon A., and Kotler M. (2006), Characterization of a novel virus causing a lethal disease in carp and koi. Microbiology and Molecular Biology Review, vol.70(1), 147-156

Pokorova D., Vesely T., Piackova V., Reschova S., and Hulova J. (2005), Current knowledge on koi herpesvirus (KHV): a review. Veterinary medicine-Czech, vol. 50(4), 139-147