"The particularly cold temperatures experienced around the time of the virus release could also have prevented the virus from spreading as hoped. Flies, in particular, play an important part in helping the virus to spread and of course they drop off when the temperature dips," he said.
"This virus was never going to be a silver bullet for rabbit control, which is why more traditional control methods need to be maintained."
Mr Bailey said testing of rabbit carcasses would also help the council identify if the newly discovered European rabbit calcivirus, known as RHDV2, is in the Waikato.
RHDV2 was recently confirmed in the Bay of Plenty after testing of two wild rabbits found on a Rotoehu farm.
RHDV2 affects European rabbits and at least two species of hares and can cause mortality in young animals from 11 days onwards.
Vaccines for the viruses have been imported into New Zealand and are available through veterinarians for pet rabbits.