Influx of exotic flies and ticks a continuing challenge
Dr Allen Heath.
The discovery of a male Asian tiger mosquito (Aedes albopictus) at the port of Auckland in late March highlighted the constant threat to New Zealand from exotic pests. An analysis by one of New Zealand's leading experts indicates this country could be at risk from a number of new species of mosquitoes, blowflies, biting midges and ticks. As well as biting humans and livestock, causing myiasis (fly strike) and contaminating food, some of these pests could also be vectors for diseases.
The work was carried out by Dr Allen Heath, who has spent the best part of the last 40 years researching ectoparasitology at AgResearch's Wallaceville Animal Research Centre. He is widely recognised as the country's leading expert on ticks and has expertise on flies as well.
His risk assessment for New Zealand compares pest incursions in other countries with similar climates and conditions to our own. He is particularly interested in the mode of entry and country of origin of the invading pests.
It is estimated that New Zealand has between 150 and 170 different species of exotic flies which have been accidentally introduced. Many of them (including Lucilia sericata, Calliphora vicina, Musca domestica and Fannia canicularis) arrived from Europe in the nineteenth century, often via ships laden with livestock, decaying meat and animal waste.
More recently, there have been arrivals of flies from Australia, Southeast Asia or the Pacific (Lucilia cuprina, sheep blowfly) in the late 1970s; North America (Pollenia pseudorudis, cluster fly) in the early 1980s; Southeast Asia or the Pacific (Chrysomya megacephala, Oriental latrine fly) in late 1980s; and Australia (Aedes camptorhynchus, salt marsh mosquito) in the late 1990s.
Between 1955 and 2006, there were 237 border interceptions of exotic flies and 100 border interceptions of ticks; 66 of the fly interceptions were of species already established here. Allen says it's often difficult to know exactly what new pests are present in New Zealand until they have had time to become established.
"A female fly has the potential to lay 2,000 eggs in a 10-day period, so it doesn't take a lot of them to establish a population here. Ticks are similarly prolific," he says.
He believes there are ways to maintain barriers against flies. Being aware of the country of origin is important, as is focusing on fishing boats which could be a potential haven for some unwanted species of blowflies.
Traps at seaports and a nationwide trapping programme could also be employed to see which species may already be here that have been overlooked, he suggests.
Throughout the world, there are about 850 species of ticks. In New Zealand, we have nine species, four of which are endemic. One particular species, the brown dog tick, has crossed our border at least three times in recent years and established viable populations which have successfully been eradicated. If this tick established, dogs would be put at risk from the tick-transmitted protozoan parasite Babesia gibsoni, among other diseases.
Between 1955 and 2005, 12 species of ticks were intercepted (100 actual cases), many of which were transported by dogs and humans. With over 4,000,000 human passengers arriving annually, plus over 4,000 dogs, Allen says more education is needed.
"We need to educate passengers on what to recognise so as not to bring ticks in, and make GPs more aware that ticks are not necessarily moles with legs!"
Half of the exotic ticks are transported by sea-birds but in one case, the cattle tick, it was transported by a human. The cattle tick already damages our deer, sheep and cattle industries by causing anaemia and affecting production, as well as causing deaths.
As part of the FRST-funded risk analysis, Allen is producing a database of ectoparasites that could establish here. He is also working with colleagues on the description of new species of mites from geckos intercepted at the border; new species of mites from mosquitoes in New Zealand are also being described.
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Page last updated: 2 July 2010