Sadly, the days when there was a “flea-free season” from autumn through to spring are long gone. Nowadays, fleas are present – and active – on our pets all year round. So, those winter fleas you’ve seen aren’t an anomaly – it’s the usual situation!
Why do we always think of fleas as being seasonal?
Ultimately, it all comes down to the flea life cycle. Only 1% of the fleas in a household are on the dog (or the cat, or whatever). The remainder are living in the environment – as eggs, larvae and pupae.
Eggs are, as the name suggests, the tiny eggs laid by the female fleas, lying around unnoticed in the environment. In cold conditions, they don’t hatch, but wait until it warms up.
Larvae are like tiny little maggots, crawling around in the dust and, usually, in the carpets. They gradually mature, becoming bigger and bigger until they pupate (like a chrysalis but with a less pretty occupant!). The colder the temperature, the slower this process is.
Pupae are the cocoons the larvae form; inside, they reorganise themselves and develop into adults. Then they wait, potentially for months or even years. The adults will only emerge if:
1. There is air movement or heightened carbon dioxide concentrations
2. There is vibration
3. The temperature is high enough
As a result, they lay in wait like tiny biological landmines, waiting for a warm blooded animal to come wandering past. Then they hatch and jump on board, hungry for blood.
Dog- and cat fleas are primarily adapted as parasites of mammalian carnivores – they have evolved to leave their eggs and larvae in the warm nests and dens that wolves and wild cats make. When we adopted dogs and cats as helpers, friends and pets, we brought them inside our houses. However, for thousands of years, fleas remained seasonal because our houses still got too cold over the winter for the flea life cycle to complete – how many of us remember ice on the inside of the windows in winter when we were growing up?!
So why is it different now?
Ultimately, there is one major change that has occurred in the last fifty years or less – central heating. We now heat our houses much more effectively than ever before, so now the average temperature, even in the winter, is high enough for the fleas to complete their life-cycle.
In addition, over recent years the weather patterns have changed, giving us warmer winters and wetter summers. This is important because the other major limiting factor in the survival of flea eggs and larvae is humidity – if the relative humidity drops below 50%, they start to die. So, wetter weather, warmer houses – it all leads to 24/7/365 fleas!
So what can we do about it?
Simple – you need to maintain an effective flea control programme all year round. That means using an effective adulticide (a drug that kills adult fleas) all the time – most products last about a month, although some prescription-only medications last longer. The most effective drugs are only available on prescription, so give us a call if you’re struggling and one of our vets will be able to help you select the most appropriate and effective product.
You also need to remember to treat the environment (otherwise you’re letting the other 99% of fleas get away!). This can be in the form of medication (there are a number of products which will help break the flea life-cycle), or household treatment. The most effective form is regular vacuuming (the air movement and vibration will wake the pupae) followed promptly by spraying with an insecticide (to kill them as they hatch).
If you need advice on flea control, give us a ring and talk to one of our vets or nurses. Remember, what works for one dog, or one household, won’t necessarily work for another, but we will be able to provide a programme tailored to your pets, your home and your lifestyle.
It’s not just dogs that can have fleas in winter, cats too can carry these unwanted guests this video from our You Tube channel explains more.