Palić, 17.05.2021- Based on field findings collected during research and laboratory testing of fish samples, the Scientific Institute of Veterinary Medicine of Serbia confirmed the outbreak of herpesvirus hematopoietic necrosis (HVHN), caused by cyprinid herpesvirus-2 (CyHV-2), in Palić and Ludaš lakes. The full version of the report can be found HERE.

Fish kills affected only one species of fish, Prussian carp (Carassius gibelio), the so-called babushka. Other fish species and other non-fish species were not affected during outbreak of the disease.

CyHV-2 affected all age categories of Prussian carp and it caused its high mortality when the water temperature ranged between 20°C and 25°C. The fish mortality rates decline when water temperature rises above 25oC. Furthermore, secondary bacterial, parasitic and fungal infections were detected during the outbreak of the disease.

“It should be emphasized that CyHV-2, the causative agent of HVHN, is not known to be infectious to humans and warm-blooded animals and poses no direct health risk to the human population,” said Dr Marko Stojčić, deputy project manager of the Biodiversity and Water Protection Lake Palić and Lake Ludaš Project. Being in charge of investments, he added, “At the time of the outbreak of the disease in Lake Palić, the same disease with the mass mortality of the Prussian carp, caused by CyHV-2, was detected in the accumulation lake “Zobnatica” in the surrounding area at a distance of less than 50 km from Lake Palić. The intensity of the disease was high and with the mass mortality of all age categories of fish. CyHV-2 was detected, and mortality was present only in the Prussian carp. Since the mortality of the Prussian carp has been recorded in many locations in recent years, we can conclude that this virus is widespread in this area. Since the mortality of the Prussian carp has been registered in many locations in recent years, we can conclude that this virus is widespread in this area. Yet, due to the insignificant commercial value of the Prussian carp in aquaculture, it may have not been reported often. ”

Sampling and analysis were performed for Lake Palić, but the floating dead fish of a similar size could also be seen in Lake Ludaš at the same time. Based on this, a team of researchers concluded that the same causative agent was responsible for the fish mortality in Lake Ludaš.

During the mass sampling, juvenile fish positive for CyHV-2 with mild HVHN symptoms, but no mortality, were detected. This confirms the possibility that the virus can exist in the Prussian carp and that the result does not have to be death. The spread of the CyHV-2 virus can cause mass mortality when one or more stress factors, such as spawning or sudden temperature changes, occur.

“The general conclusion would be that the periodic deaths of the Prussian carp have nothing to do with the quality of water, but it has with the overpopulation of this invasive species and water temperature in the lake at the period of transition from spring to summer. It is to be expected that this phenomenon will recur year after year and also after the completion of the Ecolacus project and all investments because there is neither known protective vaccine nor effective chemotherapeutic for HVHN,” concluded Dr Stojčić.

About the Ecolacus project

Project financing funds are grants from the Government of Germany, managed by KfW – German Development Bank, amounted to 6.5 million Euros and one million Euros provided by the local government of the City of Subotica, which are used for the acquisition of land, compensation payments, and in-kind contributions.