Pest discoveries

Sharp-eyed backpacker does all the right things

Chris Inglis, Incursion Investigator (Plants and Environment)

In January this year, a man returning from backpacking around the beaches in Thailand discovered carpenter ants in his luggage. He noticed the ants coming out of a plastic bag containing his shoes and shirts when he was unloading his car.

Fortunately the traveller acted quickly. He resealed the plastic bag, squashing any visible ants and sprayed the car with insecticide before calling MAF's 0800 emergency hotline number.

On the advice of on-call investigator Chris Inglis, the man immersed both the plastic bag and the backpack in a chilly bin containing Dettol and left them there overnight. He also sent a sample to the IDC lab at Tamaki for identification.

In April this year, AntiAnts was contracted to carry out control and surveillance. They laid toxic baits within a 30 metre radius of the driveway where the car was parked and the surrounding habitat. A visual inspection followed by a night-time inspection (carpenter ants are nocturnal) and final inspection the next day found no more carpenter ants.

"Carpenter ants are very large and slow to establish," says Chris. "New Zealand resident ants tend to be pretty aggressive against any new species. Toxic baiting provides benefits as a long-term approach."

Chris says the informant was also very proactive in keeping an eye out for any additional carpenter ants following the initial discovery.

"The actions by the informant were very helpful indeed. He was extremely proactive, cooperative and aware of his responsibilities."

Kingfish investigated for virus

Rissa Williams, Incursion Investigator (Marine)

Rissa joined the Incursion Investigation team in July this year. She comes from South Australia and has recently completed a PhD on parasites in kingfish (see page 15).

Last month, Rissa was able to put her experience to good use by investigating a possible outbreak of nodavirus in land-based kingfish at a farm in Parengarenga Harbour which was closing down.

In 2005, the farm had reported neurological abnormalities in stocked fish. When the report was investigated the tests for nodavirus were negative and the symptoms and mortalities were attributed to environmental factors.

Nodavirus attacks the fish's central nervous system, especially the brain and retina. The clinical signs of this disease include uncoordinated darting, spiral or corkscrew swimming, wasting and high mortality rates of up to 100 percent. New Zealand is free of nodavirus and its establishment would be a major threat to our native fish.

"Because the farm was closing down, the leftover stock of about 14,000 fish were to be released into the wild or sold for crayfish bait," says Rissa. "This presented an opportunity to acquire a larger sample of fish and test more conclusively for nodavirus."

Brain material from 150 fish (mean weight 0.783 kg) was collected for virus isolation, and organ material (liver, kidney and spleen) was collected from 15 fish for general bacteriology. Tests for nodavirus were negative, and no significant growth was recorded from bacteriology.

Suprise in the wardrobe

Andrew McFadden, Incursion Investigator (Animals)

Investigators need to be prepared for the unexpected, and so it was for Andrew McFadden, who recently investigated a report of a live bat found in an Ashburton house.

The informant discovered the fruit bat, which was about the size of a small rabbit, in her wardrobe the day after guests had arrived from Taiwan.

"At first the woman suspected it may have been a pet belonging to the visiting kids," says Andrew. "But the kids themselves expressed horror and I don't think they knew it was there. The bat could have been entangled in a coat placed into the wardrobe after unpacking the luggage."

An AgriQuality field technician collected the bat from the informant. The bat was euthanased by a veterinarian and couriered to the IDC where it was packaged and couriered on to the Australian Animal Health Laboratory (AAHL) for testing.

On its own, a single bat does not pose an establishment threat. But bats can be vectors for other organisms and diseases, including some potentially fatal zoonotic pathogens.

The bat was tested for several exotic diseases of public health significance carried by bats, including Lyssavirus and Nipah/Hendra viruses. Tests for these viruses were all negative.

A Taiwanese bat researcher, using digital photographs, determined the species of bat to be Nyctalus velutinuss (vesper or evening bat).

Silverfish infestation stamped out

Graham Burnip, Incursion Investigator (Plants and Environment)

In June this year a suit company in Lower Hutt called MAF's 0800 hotline when they discovered silverfish insects while unpacking cardboard cartons at their warehouse. The cartons contained shirts from a supplier in Hong Kong.

Earlier this year, the suit company reported a silverfish incursion to IDC in a shipment from the same supplier. In both cases, the pest was identified as being within the Ctenolepisma genus, which contains at least three cosmopolitan species considered urban pests of some significance.

"The silverfish were identified by a colleague at Lincoln," says Graham Burnip. "We had a little bit of difficulty identifying them because when the silverfish escaped from the boxes and ran across the factory floor the easiest way for the workers to stop them was to stamp on them. So there were a couple of semi-squashed ones and others more akin to a thin film scraped off the floor."

The silverfish appear to be associated with the cardboard packaging, not the enclosed garments, which are individually plastic wrapped. As with the previous incursion, the most recent detection was contained. The cartons were fumigated the day after the find was reported and the immediate area was treated with contact insecticide.

The Lower Hutt building has also been more thoroughly treated with appropriate insecticides, including under-floor treatment to ensure floor ventilation grilles didn’t provide a refuge for the pests.

The suit company has undertaken to fumigate future consignments from the Hong Kong supplier and has volunteered to change suppliers if this issue is not addressed.

To address this entry pathway at source, IDC has provided the suit company with silverfish pest management options, including chemical names of appropriate insecticides. These have been passed on to the Hong Kong supplier.

"We're very happy with the cooperation from the suit company - they were very professional," Graham says. "They identified where the problem was and put the hard word on the cardboard box supplier to lift their game."

In fact, as well as the New Zealand suit company, the Hong Kong supplier has also been very receptive to suggestions for shutting down this pathway.

"Nobody wants this problem. They both see it as a potential blight on their good name and an unwanted additional cost through the need to fumigate," Graham says.

Back to Biosecurity Magazine - Issue 71

Page last updated: 30 April 2008