IiNet



Flea Control

The most common flea found on cats and dogs is the cat flea ( Ctenocephalides felis). Using modern treatments it is now possible virtually to eliminate fleas on cats.

Why control fleas? 

While many cats live with fleas and show minimal signs of infestation, control is advisable because:

• The cat flea carries the larval stage of the tapeworm Dipylidium caninum. Cats can be infested with these worms by eating fleas during grooming. Fleas have the potential to transmit other infectious agents.

• Adult fleas feed on cats' blood and in young kittens this can cause anaemia. Anaemic kittens are weak.

• Some dogs and cats develop an allergy to flea bites which causes them to scratch excessively or to develop skin disease.

• Cat fleas can cause itchy bites on sensitive humans, typically around the ankles.

Does my cat have fleas? 

During grooming cats eat fleas in their coat, making them difficult to find. An itchy cat, or insect bites on human ankles, may be the only signs of infestation. The best way to demonstrate the presence of fleas is to place the cat on a sheet of white paper and comb it meticulously. A fine-toothed flea comb may trap one or two fleas in the brushings. 'Flea dirt' - flea excrement consisting of undigested cat blood - can usually be found. These are characteristically black and comma shaped. When placed on damp cotton wool 'flea dirt' slowly dissolves producing bloody streaks.

Flea life cycle 

The adult flea lives permanently on its animal host. Within two days of finding a host and feeding on its blood, the female starts to produce eggs at a rate of 50 a day. The eggs fall off the cat's coat into the environment together with 'flea dirt', which provides food for the hatching larvae. Eggs and larvae may be found anywhere the cat has been, but are particularly concentrated in places where the cat sleeps. The larvae move away from light and penetrate deep into carpet and soft furnishing. Larval development ends with the formation of a pupa in its sticky cocoon. A pre-emerged adult develops in the cocoon where it awaits signals suggesting the presence of a host, such as heat, carbon dioxide and vibrations. The flea can emerge and attach to the host in seconds. However, if no host is present the flea can lie waiting in the cocoon for up to two years. In the right conditions the whole cycle can be completed in 15 days. Centrally heated homes with fitted carpets provide ideal conditions for all year round development of fleas. One adult flea can leave hundreds of eggs, larvae and pre-emerged adults in the house.

Flea control 

For effective control, adult fleas on the cat must be killed and reinfestation from the environment prevented.

Killing adult fleas

A wide range of products is available to kill adult fleas on the cat. These vary in their formulation, speed, efficacy, duration of action, ease of use and cost. For an animal allergic to flea bites, where the aim is to prevent any bites, an agent which kills fleas rapidly should be chosen.

Removing fleas in the environment

Frequent vacuuming can help to reduce, but not eliminate, environmental infestation. Vacuum bags should be disposed of to prevent collected immature flea stages continuing to develop in the house. Anything that is heavily infested, such as pet bedding, should be disposed of. Treatments can be used to prevent reinfestation in a number of ways:

• Using a long acting treatment to kill adults on the infested animal and all other animals in the household thereby preventing egg laying.

• Treating the house to kill the various flea stages. This approach suffers several problems. The larvae and pre-emerged fleas lie at the bottom of the carpet pile and other such places that are difficult to reach. Treatment of the whole house is essential - this can be expensive and time consuming. All soft furnishings should be treated. All nooks and crannies should be included, such as gaps between floorboards and skirting boards. Vacuuming before treatment is advised as this stimulates adults to emerge from cocoons. Manufacturers' guidelines must be followed carefully to avoid the potential toxicity associated with environmental sprays.

• Insect development inhibitors can be used to eliminate immature flea stages from the environment. These are given to, or used on, cats to prevent fleas from hatching into larvae (chitin synthesis inhibitors) or to prevent flea larvae developing into adults (juvenile hormone analogues). To be effective these products must be given to all cats and dogs in the household. These products do not kill adult fleas.

To be effective all treatment guidelines should be followed. For some treatments there may be a lag of weeks to months in which fleas in the environment continue to develop.

Long term flea control 

Once the adult fleas have been removed from all the animals in the house and the environmental stages have been eliminated, treatment can be reappraised. In a completely indoor household where none of the pets go out, no further treatment may be necessary. However, where pets go outside further treatment will be needed, probably in the form of a single agent. This could be residual treatment that kills adult fleas on the animals or one that provides environmental control by interrupting the flea's life cycle. An on-off approach to flea control is not recommended as this provides ideal conditions for the development of flea allergy in animals.

What products are available? 

Flea control products can be purchased from the veterinary surgery, chemists and elsewhere. However, the new, safe and very effective generation of flea control products are only available from veterinary surgeries where advice on their use is provided.

Flea control products come in many forms: collars, shampoos, sprays, foams, powders, tablets and spot-ons. A product that is difficult to apply is unlikely to succeed. Shampoos have a very short duration of action. Rinsing out the shampoo also removes the insecticide that kills the fleas and so there is no residual effect. Likewise powders are only effective while on the coat - a few days at most. Collars are not recommended because the agent they contain does not spread over all the coat, making them considerably less effective.

Traditional preparations 

Traditional flea preparations contain organophosphate, carbamate, pyrethroid or pyrethrum insecticides. These are potentially toxic to cats. When used on cats, dosing frequency is determined more by the consideration of safety for the cat than efficacy. Thus less than 100 per cent efficacy can be expected. Pyrethrum and pyrethroids can give very rapid killing of fleas over a short period. Many environmental sprays include traditional insecticides either alone or in combination with an insect growth regulator.

Suggested precautions include removing pets and children before using the spray and covering food preparation areas and fish tanks to protect them.

Traditional flea products can be used safely provided instructions are followed carefully. It is usually necessary to use other flea control products simultaneously. These should be chosen carefully to avoid potentiating toxicity. If in doubt seek veterinary advice.

New products 

A number of new products are available that are very safe because they act at receptors that are not present in mammals, only in insects. These products show a high level of efficacy that remains over a prolonged period permitting dosing frequencies of up to a month or longer. They have excellent safety profiles enabling the treatment of kittens from a young age.

• Frontline (Merial) kills adult fleas and is available as a pump or spot-on. The pump is licensed for use from the age of two days, the spot-on from 12 weeks. Very rare toxicity problems have been reported associated with the alcohol base where cats have been placed in confined containers immediately after application of a spray.

• Advantage (Bayer) kills adult fleas and is available as a spot-on.

• Program (Novartis) contains a chitin synthesis inhibitor that prevents the flea eggs from hatching. It is given to the cat as a liquid once a month or by injection every six months. Fleas imbibe the treatment when they drink the cat's blood. This treatment does not kill adult fleas.

• Staykil (Novartis) spray contains cyromazine, another chitin synthesis inhibitor for use directly in the environment. It prevents larvae developing into adults by inhibiting the formation of the adult's chitinous exoskeleton.

• Juvenile hormone analogues such as methoprene (used in Acclaim 2000, made by Sanofi) and pyriproxifen (used in Indorex, made by Virbac) act by preventing flea larvae developing into adults. A single application of the spray to the environment can last for six months to a year, depending on the product used. These products also kill flea eggs and have also been used on animals as sprays and in collars.

Other products 

Sodium polyborate applied to carpets kills environmental flea stages by desiccation. It is available as a powder for DIY application or by specialist application that lasts for a year. Contact your vet for details.

Natural botanical products that have been suggested to have insecticidal or insect repellant quality include: eucalyptus oil, pennyroyal oil, tea tree oil, citrus oil and D-limonene. These products have not been through the rigorous safety and efficacy evaluation required for veterinary licensed products. All the agents listed are aromatic oils that are potentially neurotoxic to cats. Often the exact concentration of the active ingredient is unknown so they do represent a potential hazard.

Safety advice 

Cats are particularly susceptible to developing toxic reactions to flea control products containing traditional insecticides. Some products for use on dogs are toxic to cats. The use of several products containing similar active ingredients or interacting agents on the cat, animals it comes into contact with or in the environment, can lead to toxicity. Products that contain insecticides similar to those used in flea control include wood treatments and garden, household and agricultural insecticides. If in doubt seek veterinary advice. Tell your vet about any flea treatments you have used if he/she is prescribing flea control products, other medication or contemplating sedation or anaesthesia of your cat.

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