Three swans have died from suspected botulism in Verulamium Lake due to the excessive build up of silt.
Hundreds of water fowl died from avian botulism last year and concerns have been voiced that it might return again if the lake is not cleared.
Avian botulism is a paralytic disease caused by the bacteria (clostridium botulinum) produced from silt in warmer temperatures.
A number of dead ducks have been spotted in recent weeks but the district council will not confirm the deaths are caused by botulism.
Now three swans, which were retrieved by Swan Rescue Hertfordshire working with the Swan Sanctuary, have died, while another is currently in their care.
There are two further swans that are thought to be at risk which will be re-located later this week.
Steve Knight, a Swan Sanctuary trustee, said that he was very sure that botulism was the cause of the swan deaths, despite the fact that there have been no official tests yet.
Steve said that he did not understand how the council could deny that it was botulism.
He said: “We’ve been doing this for over 30 years. It is a bit like when you know your child has a cold, it is as simple as that. We are a registered vet practice at the end of the day as well as being a charity.”
Following calls from members of the public two swans were retrieved from Verulamium Lake on Sunday (17), and a further two on Monday (18). Two of the four were already dead and another has since died with the fourth on a drip and other medication.
Steve added: “It takes them a long time to recover.”
St Albans council’s head of community services, Richard Shwe, said: “We are aware that a Swan Rescue official has suggested the swans may have contracted botulism which can emerge during very hot weather.
“However, that is only speculation and they have not carried out any tests to try and determine this.
“We are monitoring the health of the park’s wildlife and looking at ways to improve their welfare, particularly the water quality of the lakes.”
The council is planning to remove 60 tonnes of silt, but has maintained it will not dredge the lake.
Mr Shwe added: “In the longer term, we are working with the Environment Agency on a scheme to restore the River Ver to its more natural state.”
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