Dunedin City Council says it is confident an outbreak of avian botulism which has killed 1200 birds at the Waikouaiti wastewater treatment plant north of Dunedin is contained.
The council said it is working closely with Otago Fish and Game, MPI, the Department of Conservation and Otago Regional Council to respond to the outbreak, first identified on January 21.
While unrelated to avian influenza, the council told 1News earlier this week it was being treated a “significant animal welfare issue”.
Deceased birds are now being recovered and buried to stop the spread and chain infection in and around the plant’s oxidation ponds, it said.
It believes 1200 birds have died, with the number expected to rise in the coming days.
Most are paradise shelducks, but native grey teals, mallards, Canada geese, black swans and black-backed gulls have also been affected.
Other nearby councils are also being contacted to discuss the outbreak, and both Otago Fish & Game and DOC are conducting further surveillance of birds for signs of any further spread.
“At this stage, although a small number of dead birds have been found in the area immediately around the oxidation ponds, within a few hundred metres, and the outbreak remains contained to that site.”
Bird deaths near Timaru
Further north, DOC Geraldine senior biodiversity ranger Ian Fraser told 1News about 40 black-backed gulls/karoro have died at the Waitarakao Washdyke Lagoon in Timaru.
“While Biosecurity New Zealand will test samples to rule out any exotic disease, it looks like avian botulism is the cause.”
“DOC is monitoring the situation and plans to collect and dispose of some of the carcasses to reduce the spread to other birds in the area.”
How is the disease caused?
Dunedin City Council said the disease begins when waterfowl eat the toxin produce by the clostridium botulinium bacteria.
“It is harmless until certain environmental factors occur, such as low oxygen and warm temperatures.”
Oxygen levels within the Waikouaiti wastewater treatment ponds routinely fluctuate each day as part of the plant’s natural system, depending on weather, time of day and other factors.
“Monitoring results show oxygen levels were normal before the outbreak was first detected, then dropped at the time the first deceased birds were found, which may be consistent with deceased birds disrupting the treatment process and the large number of birds present.
“There were no specific operational issues identified prior to the initial bird deaths.”
The disease poses “minimal risk” to the health of humans, the council added.
Sick or injured wildlife should be reported to DOC, and three or more sick or dead wild birds in a group should be reported to Biosecurity NZ’s Exotic Pest and Disease Hotline.
Advice for those visiting Waikouaiti estuary
- Don’t let your pets eat dead wild birds or fish
- Don’t touch or handle sick or dead wild birds or fish
- Don’t eat undercooked or improperly prepared waterfowl or fish. Heating the food properly will kill the toxin
- Don’t harvest birds that appear to be sick or dying
- Maintain good hand hygiene. Wash your hands either with soap and running water or use alcohol hand rubs often and thoroughly — especially before and after contact with animals and their environment.
