A great blue heron in North Holland tested positive for West Nile virus. The virus is rare in the Netherlands. As the virus is transmitted by mosquitoes and the mosquito season when mosquitoes bite is almost over, there will probably be no more spread of the virus now. Unlike other domestic (agricultural) animals, horses can develop symptoms if they are infected with the virus.
The great blue heron was caught in a duck bait in mid-September. Erasmus Medical Center conducted research on avian flu here. In the vicinity of the positive heron, it is now investigating whether more birds have been infected with the West Nile virus. NVWA (Dutch Food and Consumer Product Safety Authority) is also conducting research on wintering mosquitoes in the area.
Western virus
The virus occurs in birds and is transmitted by mosquitoes that feed on the blood of infected birds. These mosquitoes spread the virus to other birds and sometimes to humans and mammals, such as horses. Over the past few decades, the virus has spread to much of the world, including southeastern and central Europe and Germany. In the Netherlands, West Nile virus was first found in 2020 in a canary, and the infection was subsequently detected in mosquitoes and 8 people that year.
Infection in humans
Most of the time, people don’t get sick from the West Nile virus. About 80% do not complain at all and 20% experience mild symptoms such as fever and flu-like ailments. Only a small percentage (1%) develop a serious disease, such as encephalitis or meningitis.
Infection in horses
Horses can also receive complaints, unlike other domestic (agricultural) animals. Just like in humans, an infection with West Nile virus occurs in most horses with no (visible) symptoms. About 20% show mild symptoms such as loss of appetite, lethargy and fever. About 10% of animals develop severe ailments. Vaccines are available for horses.
advance reporting
RIVM, NVWA and other parties are working closely to monitor the spread of the West Nile virus. In order to identify the virus early, RIVM and NVWA are conducting research on mosquitoes, among other things, and monitoring changes there. Erasmus MC (Erasmus University Medical Center) leads a national research consortium that tracks the risk of epidemics. RIVM and NVWA inform the public, so that people know what they can do for themselves when needed. This way we prevent mosquitoes from transmitting the virus and making people sick as much as possible.
See also the WUR infographic on West Nile virus in horses.
Bron: FNRS
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