Wednesday, September 18, 2013

Three things I learned: facts about fleas

Phil interrupts a photo session to scratch a flea-induced itch. He's tiny, he's white, he's just the right flea-jump height, so he's a walking version of the so called "white-sock test". [You can try it at home but prepare for a shock. Put on some white socks and walk through your house slowly. Count the number of fleas - they are positively phototactic, meaning they love light and white!].
It wasn't my intention to institute a flea theme this week, but the Australian Small Animal Veterinary Association hosted an excellent webinar with Dr Geoff Gibbons on fleas last night. I meet fleas daily in practice, I see the irritation and misery they create and I've even sprung them sinking their teeth into my furry family.

In animals they cause pruritis, flea bite hypersensitivity, tapeworm (Dipylidium caninum) and, in severe infestations in puppies and kittens, clinically significant anaemia (I've transfused a kitten for severe flea-induced anaemia). Alongside mosquitoes, the rabbit flea transmits myxomatosis. 
I took this photo of a cat flea (Ctenocephalides felis) under a microscope using a smartphone. Ectoparasites are impossibly beautiful up close. You can see the blood inside the well as some flea faeces building up the abdomen. The larvae feed on flea faeces.
In humans they spread rickettsial diseases, bartonella and the plague (which Dr Gibbons reminded us killed more people than all wars combined). Oh yes, and also worms (Hymenolepis nana and Dipylidium caninum).

They're filthy, but they're fascinating and they are hardcore. For example, they can jump a distance of 33cm and a height of 18cm (I am not mathematically gifted enough but proportionally speaking I know I can't jump that high).

So what did I learn? Well, it was the review of the life cycle and features of the life stage that I found most useful.
  1. Adult fleas constitute only 5% of the infection. The eggs make up 50%, larvae 35% and pupae 10 per cent. I've never really broken it down numbers-wise before, but this reinforces the point: an adult flea on an animal is a SIGNIFICANT finding. That is the tip of the flea iceberg. Take home message: if you see a single flea, you need to treat an infestation.
  2. The reproductive break point (RBP) is the time after the application of a flea product when the drug's concentration has declined to a level at which fleas are not killed prior to egg laying (egg laying occurs around 24-48 of the flea's first feed). Because the speed of the kill is proportional to the concentration of product administered, the RBP is reduced in very big dogs at the upper end of the dose range. Interestingly, most chemicals have an RBP of around three weeks. Take home message: regular flea control is vital.
  3. The main reasons for poor control of fleas, or outbreaks of fleas, are irregular treatment, not treating all in-contact animals (including strays/wildlife), applying most of the product to fur (versus applying to skin), some product being sucked back into tube [I'd not heard of this but apparently when you squeeze the tube you should not release it while it still has contact with the animal as some product can be sucked back in], underdosing, poor environmental control and failing to attack all stages that CAN be attacked (adults, larvae, eggs - the pupae are almost indestructible). So far there is no evidence of resistance to the chemicals available on the Australian market (though some delegates disagreed based on their experience), so the main cause of fleas continuing to stick around despite treatment was inappropriate treatment. Take home message: there are a gazillion ways to misuse flea control. Use it the right way. 
I must confess that fleas tend to take advantage of my frequent spells from vacuuming. They know their enemie's weaknesses well. 

Dr Gibbons reminded us that, aside from good flea prevention, the vacuum cleaner should be used daily in flea affected areas. Sigh.