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Looming flea plague: Serious suffering ahead

October 2005

Our looming flea plague: Serious suffering ahead

Very soon New Zealand will face its annual flea plague.

Warm and moist conditions are now triggering one of the country’s biggest home insect invasions.

Serious skin infections, resulting from fleabites and reactions to the insects’ saliva, will see hundreds of 1 to 14 year-olds hospitalised.

The nation’s animals will also suffer everything from discomfort to skin infections and anaemia – as newly emerged adult fleas suck up to 15 times their bodyweight in blood.

Medical authorities say most of the children’s suffering can be avoided.

In a study published last November, the Capital and Coast and
Hutt Valley district health boards (DHBs) and Wellington Regional Public Health, pointed to fleas causing some of the rising number of children admitted to hospitals with cellulitis. That’s an umbrella description of a range of serious skin infections, some resulting in advanced diseases requiring extensive surgery.

In the Wellington region, the number of child hospital admissions for cellulitis rose 61%, from 119 to 191, in the seven years between 1996-97 and 2002-2003.

The figures are described as “the tip of the iceberg” and under report the problem, the Wellington report says, because they don’t capture all ages, all conditions or the burdens the community carries as a result of disease.

The hospitalisation rate increased from 15.4 per 10,000 to 23.9 per 10,000.

In 2002 / 2003, “cellulitis” was the sixth or seventh most common cause of avoidable hospitalisation out of about 32 “avoidable” conditions.

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The seven-year cumulative cost to the two Wellington region DHBs alone, just for those admissions counted, was estimated to be over $2 million.
For true cellulitis, Wellington and New Zealand (12.5 and 12.9 per 10,000 respectively in 2002/03) had about twice the hospitalisation rate of Australia (2001/02) and the USA (2002) – 6.8 and 6.5 per 10,000 respectively.

For most years, especially in recent years, the highest number of admissions has been occurring between January and March.

One impact of the often-avoidable problem – which Wellington health authorities want to cut by 30% in two years ending November 2006 – is postponement of other types of elective surgery.

Health authorities say the problem is being driven, among other things, by living and social conditions which allow insects to thrive and the problems they inflict to go untreated for too long.

The funny little flea – the subject of joke sites across the internet, a source of mirth at flea circuses in days gone by, and of amazement at the fact they can make the equivalent of a 300 metre leap by a two metre tall human, is inflicting a serious toll on people and animals.

Some 22 species of flea will feed off humans (though only one exclusively seeks people as hosts) as a result of our association with their primary animal hosts.

Those at the front line of the flea fight know they have as an adversary an insect which has at least a 100 million year history. The battle is to control. Eradication, even in the nation’s homes, is most unlikely.

The animal health company Merial, which last month made its billionth dose worldwide of FRONTLINE®, an anti-flea treatment for animals, says the area from Taupo north will suffer the most as temperatures go into the “optimum” range of 17 to 18 deg C, and humidity reaches 45% or more.

To understand how to break the flea lifecycle and reduce household infestations and resulting irritation and disease for both humans and animals, Merial’s technical advisor veterinarian, Maureen Forsyth, who also practices in Auckland, says New Zealanders need to know why they can be suddenly swarmed by adult fleas.

“You’ll often hear of people telling how they’ve walked into a room – especially in a holiday home that hasn’t been used for some time – and had their legs turned black in seconds with fleas,” she says.

That’s because a simple footstep, a minute rise in the level of carbon dioxide, from the breath of a human or animal, and a variation in light (from the shadow cast by a moving person or animal) can trigger a remarkable transformation:

The flea eggs, laid earlier at the rate of 40 to 50 eggs a day for up to 21 days by a single female, which have turned into larvae, then protected themselves in a chemically-impervious cocoon as pupae, will take the weather and other triggers to hatch – and leap for a host and blood.

Incredibly, the adult flea can leap up to 600 times an hour – for up to three consecutive days if necessary – in the hope of finding a host.

It needs to hook into a victim within three days, or it will die.

The blood-sucking fleas deposit blood-rich faeces (black dirt) which drops into the nests of their hosts (animal blankets, deep pile carpet, even New Zealand’s matted kikuyu grass). The eggs also fall into these areas and larvae eat the faeces, before turning into pupa – and awaiting the optimum conditions which are nearly upon us.

The whole life cycle can be condensed into seven to 21 days in optimum conditions.

But Forsyth says recent research has established the pupa can survive in their cocoons for almost a year, nearly three times as long as previously thought.

For animals, Merial has now expanded the anti-flea armoury to include a chemical “double whammy”: one to not only kill adult fleas – but also stunt and deform eggs and larvae.

The only product on the market to do this (using the trade name FRONTLINE Plus), Forsyth says the “adulticide” interferes with an adult flea’s nervous system. It effectively gets excited and dies of over activity.

A chemical called s-methoprene is also used to mimic the flea’s naturally occurring growth hormone and can stop most eggs developing into pupae. Those that do make it are deformed, providing the first single-application chemical to totally disrupt the flea’s lifecycle.

Forsyth says clinical trials showed FRONTLINE Plus killed 100% of fleas on the animals within 18 hours of being applied, and 98 to 100% of new fleas within eight hours of reinfestation.

She warns people to be aware that some so-called ‘natural’ anti-flea products contain pyrethoids which are known for their toxic potential in cats.

The SPCA is also warning pet owners to take care. On its web site, it says: “Not only are the older products less effective than the new generation of flea treatments, they are also up to 200 times more toxic.”

The new products, like FRONTLINE Plus, are also waterproof. Applied onto the back of an animal’s neck, it is carried right across the body by natural skin oiling systems. It doesn’t enter the animal‘s bloodstream. And will stay there while the lucky dog – or unfortunate cat – goes for a dip this flea plague season.

At up to 50 eggs for 21 days, that’s 1050 per female. Just how many are lurking at your place for the arrival of warmer weather – or the vibration of your footstep at your holiday home?


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