Fleas are a problem both because of the effects they have on their hosts and in their ability to carry and spread disease. Dogs and cats share the same fleas so it is important to treat all the animals in the household. Controlling fleas in the environment is also part of successful flea elimination and an understanding of the flea life cycle is important to achieve this.
Life Cycle of Fleas
- There are 5 stages of the flea life cycle
- Only adult fleas are parasitic
- Adults account for only 5% of the flea population
- Most of the life cycle occurs away from the host
- 50% of the flea population are eggs on the ground
An adult flea requires a blood meal for food and for reproduction. Females lay eggs on the animal but these soon drop off onto the ground. A female can lay 40 eggs a day for her several week lifespan. Eggs account for 50% of the flea population and their hatching is favoured by heat and humidity.
These eggs will hatch into larvae anywhere from two days to two weeks after being laid, depending on the environmental temperature. The larvae feed on environmental debris and the faeces of adult fleas which is essential for their development. They dislike strong light but need moisture and so outdoors will seek out shady moist areas. Indoors they thrive in deep carpet fibres.
They undergo two moults and after the second moult, the larvae spin a cocoon which is called a pupae. The fleas can survive for months at this stage and they are resistant to many insecticides applied to the environment. This means they can emerge long after any environmental treatment has worn off.
If the environment conditions are right with sufficient heat and moisture, the adults emerge in as little as 5-10 days ready to start the cycle again. They must be stimulated by carbon dioxide, pressure or heat which indicates the presence of a host and they can only survive a few days without a blood meal. The whole cycle may be completed in as little as three weeks, or may take as long as two years depending on environmental conditions.
The adult fleas are attracted to light and emerge to the surface of the carpet, or ground cover if outside. They jump onto a passing host and attempt to stay there as long as possible as they begin to lay eggs, two days after the females first blood meal. In optimum humidity and temperature the whole life cycle can be completed in 2-3 weeks.
Ctenocephalides canis and Ctenocephalides felis are the types of fleas most important in the dog and cat. C. felis is more common and widespread and may also affect man. The common tapeworms in dogs and cats may be spread by these species of flea, and they are also thought to be largely responsible for causing allergic flea bite dermatitis in dogs and cats. Although fleas are thought to have host preferences, they will feed from a variety of mammals and birds.
A single female can feed on many times her own body weight in blood over her lifespan. This can be of particular importance in very young animals. Kittens with high flea burdens are very susceptible to fatal anaemia if fleas are not treated.
Signs of a Flea bite
The primary response to a flea bite is an itchy, raised, red ‘spot’ on the skin. This in itself is not normally a major problem. If an animal is bitten repeatedly over time, however, allergic flea bite dermatitis may develop. This is an allergy to substances within the flea saliva, and is normally worst at the time of year when fleas are at there most active, which in the UK would be summer. It is a much more itchy condition, and the animal may inflict self trauma in a quest to relieve the irritation. Often a moist dermatitis will result, following intense licking and chewing. The lesions seen are usually along the back, the stomach and the inner thighs. If treatment is not instituted and the condition carries on over time, the skin will become thickened and hairless.
In cats, the flea bite allergic condition is known as miliary dermatitis, and is very characteristic. Many small, brown ‘rice- grain’ crusts are present on the skin and easily felt. These are very itchy.
Diagnosis of fleas
Diagnosing an animal as having a flea infestation can be done either by the identification of fleas themselves, or by the identification of their faeces in the hair coat. The faecal particles appear dark brown but when placed on moistened tissue are actually a dark red, due to the blood that has been digested. Sometimes an animal with flea allergic dermatitis will not appear to have an actual infestation, but it is assumed due to the nature of the skin irritation. The allergy can be set off by only a bite or two and although it may not seem that a current infestation is present, treatment should still be instituted.
Sometimes treating the flea infestation is not enough to soothe the irritated skin seen with allergic dermatitis. Often short term steroids, antibiotics and possibly shampoos are required, depending on how chronic the condition has become.
Treatment of fleas
There are many products on the market for treatment of fleas. These include sprays, spot-on drugs, collars, injections and oral treatments. An important point to remember is that since much of the life cycle is spent away from the host, the environment should also be treated to ensure that the animal is not re-infested. Although certain products treat both the animal and its surroundings, this is not always the case. Consult your veterinary surgeon about the most effective products to use.
1) Treat the animal
2) Treat the environment
Frontline for your pet Indorex or Skoosh for your house
Be wary of using over the counter products without veterinary advice. Do not treat cats with dog products, they are often not suitable and can be potentially toxic.