Mass Bird Mortality Event Under Investigation in South Australia Amid H5 Bird Flu Concerns

South Australian authorities are investigating a mass bird mortality event after more than 80 dead and sick birds were found off the state's south-east coast.

At this stage, the SA government said the birds were not being considered as "suspected cases" while they underwent testing for H5 bird flu in Adelaide.

State aerial surveillance detected 49 dead and 35 sick greater crested terns on an island called Baudin Rocks, about five kilometres south of Cape Jaffa on Friday.

SA Chief Veterinary Officer Skye Fruean said it would be "very unlikely" that testing of these birds would return negative results for the H5 strain.

"We do need to wait for the lab testing, but given it is an island that has a large number of crested terns and a large number of sick and dead crested terns, we are of course expecting that we would get some bad news from that situation in the coming days," Dr Fruean said.

"A mass mortality event doesn't have any particular defined number … mass mortality is essentially something that would be unusual and significant and I'd describe [these deaths] as that.

"We've known that this is going to happen at some point in time, unfortunately it appears to be escalating quite rapidly."

Dr Fruean said the island was surveyed two weeks ago when there was no evidence of sick or dead birds but "that situation has changed".

She said the aerial surveillance team had collected a small sample for testing but had not euthanised any birds on the island.

SA Environment Minister Emily Bourke said the mass mortality event "would provide a significant change in our response and our understanding on the impact on wildlife here in South Australia".

"What we are seeing now, this week particularly, is there has been a change in those numbers going from migratory to localised spread and now potentially into large numbers around our coastline," she said.

Suspected cases rise

CSIRO testing has confirmed 20 previously suspected cases of H5 bird flu in SA, including one seagull at Robe, the first confirmed detection in the species in Australia.

There are now 53 confirmed cases in Australia, 39 of which are in South Australia.

A further six suspected cases have been detected, including three in seagulls and one in a greater crested tern from Monarto.

Dr Fruean said while the Monarto case "was further inland" than other detections, the Monarto Safari Park nearby had "biosecurity protocols" in place to protect vulnerable species.

In a statement, Zoos SA chief executive Phil Ainsley said the Monarto detection was outside the safari park and it "doesn't change our response".

"We've been preparing for the potential arrival of H5 avian influenza for several years, and the precautionary biosecurity measures we've already implemented continue to do exactly what they were designed to do," he said.

Victoria also detected six more suspected H5 cases in the south-west of the state, which would now undergo further testing at CSIRO's Australian Centre for Disease Preparedness.

Earlier this week, local transmission of H5 bird flu occurred for the first time between a number of greater crested terns in South Australia.

But Australian Chief Veterinary Officer Beth Cookson said the threat level to agriculture and to humans remained low.

Responding to more cases

Dr Fruean said the mass mortality of birds off South Australia's south-east coast was "significant" but not surprising.

She said authorities would continue aerial surveillance and monitor the Emergency Animal Disease Hotline, but would stop testing samples from locations where bird flu had been present.

"At some point in time and we're not there yet, we will stop testing in areas where we know it [bird flu] is well established … because there is nothing we can do to stop the spread, we don't need to continue testing in an area that we know it is present," she said.

Ms Bourke also advised South Australians to keep their pets close to protect other species and wildlife.

"If you can keep dogs on leads when you're walking that would be ideal, particularly where there is wildlife, but also not having cats roaming in the evening as well because cats can get bird flu," she said.