Thursday, April 10, 2014

Three things I learned: rethinking flea control (or, HELP! there’s a biomass in my carpet!)

Fleas are the number 1 cause of pruritis (itchiness) in dogs and cats that I see in practice. By a mile.

Not sure if you’re noticed, but fleas are going INSANE this month and they can be a nightmare to control. One of the biggest challenges of managing fleas is managing the expectations of owners – and maybe vets too.

Fleas caught when I bathed Phil and flea combed him. (He is on several reputable flea products - how can it happen? Read on).

ProfessorMichael Dryden, or Dr Flea as he is known in the business (not to be confused with Flea from the Red Hot Chilli Peppers), is a world expert on fleas and has played a pivotal role in development of some of the more commonly used antiparasiticides (say that with a mouth full of cereal). He presented a webinar last week on flea biology which was entertaining. (The webinar was hosted by MSD Animal Health, and it should be declared that MSD has just launched a new flea product in Australia).

You would think vets would get sick of continuing education on fleas, but actually they are one of the commonest woes of our patients, causing everything from alopecia (hair loss) to fulminant dermatitis to behavioural changes and lack of sleep (for the owner and the animal). One of my goals in life is to fight fleas more effectively - but that ain't no humble goal.

Dr Flea's take on fleas is a bit different to others I have heard. I often instruct owners to treat their environment because fleas on the animal represent the tip of the iceberg of infestation.

Dr Flea says this: By the time a pet owner notices fleas, immature flea stages have been developing in the home for the previous 1-2 months. (The fleas came from pupae, which came from larvae, which came from eggs 1-2 months before).

The “biomass” (what a creepy concept) of immature flea stages in the home environment will continue to re-infest pets. Most of us are in denial about the biomass in our carpet. And if the word biomass doesn't make you feel like Sigourney Weaver taking on aliens, I don't know what will. It elevates the battle against fleas to intergalatic warfare.

As pet owners we want the infestation over yesterday (amen) but it isn’t biologically possible to eliminate that biomass overnight. You can kill the fleas on your pet, but more young fleas will emerge from this biomass, continuing to do so for 3-8 weeks, up to three months in some homes. Up to 95 per cent of the biomass will develop and complete its emergence within about two months.

If the product you are using effectively prevents flea reproduction, you need around a three month timeline (with variation between individual households due to temperature and household conditions).

With the release of decent spot-on treatments in the 1990s we moved away from blasting homes with chemicals to using products to break the flea life cycle, either killing fleas before they reproduce on animals or directly inhibiting reproduction.

The initial speed of kill of any residual insecticide is directly proportion to its concentration. The longer the product is on, the longer the speed of kill (the residual speed of kill) – until eventually the speed of kill slows down enough to allow fleas to lay viable eggs before they die (they only need 24-48 hours).
This is the reproductive break point. The ideal product kills fleas before they lay eggs, or actually destroys eggs.

Dr Flea went into great detail about the way he performed flea studies, a methodology he has refined over decades. So where do flea researchers go for their field studies?

Tampa,Florida, it turns out. This is the flea capital of the US. Temperatures vary from 27 to 35 degrees C with 75-85% humidity. Flea heaven. Some of the infestations he described (>250 adult fleas visible on pets) made me wince. 

Even Dr Flea said it isn’t ethical to use placebos in his studies because the infestations in this area are life-threatening (heavily infested animals die from anaemia or flea-borne infectious disease).

He looks for fleas in an interesting manner. He combs certain areas – for example the dorsal midline, base of the tail, lateral thorax on left and right and the inguinal region. The number of fleas he sees in these areas represent 23 per cent of the total adult flea burden on that animal (try this at home). 

For those of you who feel like fleas are worse than ever you might be on to something. Dr Flea has observed a gradual steady increase in flea infestations since 1997. He added that no flea product can kill every single flea before it can feed.

You can read more about Dr Flea's research on fleas on his website which is a treasure trove of fact sheets, flea research info and even videos of fleas if you so desire. (He is also a keen hiker and photographer).