Eradication of southern saltmarsh mosquito a significant step closer

MAF Biosecurity New Zealand (MAFBNZ) says an important milestone has been reached in the programme to rid New Zealand of the southern saltmarsh mosquito with the completion this week of aerial treatments in the Wairau area in Marlborough.

Wairau is the last New Zealand location under treatment since activities began in 1998 with the discovery of the mosquito in Napier and then other subsequent locations. Elimination has so far been declared in 10 areas including Napier, Coromandel, Kaipara and Grassmere (also in Marlborough).

The MAFBNZ campaign to eliminate this mosquito has built on previous work undertaken by the Ministry of Health. Southern saltmarsh mosquito is known to carry Ross River virus which produces debilitating flu-like symptoms in humans. Furthermore, the southern saltmarsh mosquito is known for its vicious day time biting.

One of the treatment tools available has been the helicopter application of S-methoprene granules – an insect growth regulator designed to stop the mosquito pupae hatching into adults. In Wairau over the past four years, three-weekly aerial application has covered areas of suitable habitat. This has ranged from 150 hectares in the dry summer period to over 1600 hectares in the winter.

With no mosquito larvae finds in Wairau for over a year, and no adults trapped for more than two and a half years, MAFBNZ Incursion Manager David Yard says its Technical Advisory Group has recommended concluding the aerial treatments.

“This is a very good sign of positive progress being achieved,” says Mr Yard.
“For us to be confident, however, that the southern saltmarsh mosquito has been eradicated from this last New Zealand location, we need to continue normal ground based surveillance activities of trapping and checking for larvae until at least June 2010.

“If no more evidence of the mosquito is found during the next 12 months, we will be in a position to declare full eradication has been achieved,” says Mr Yard.