Controlling fleas Print E-mail
News - Rubrieke
Thursday, 27 February 2014 23:38
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Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

It seems as if the fleas have moved up from the coast – kitchen sink and all. The reason is probably the warm humid weather we are having, which is perfect for flea survival and breeding. The flea’s lifecycle can be completed in two to three weeks in good environmental conditions.

The problem with controlling fleas is that those adult fleas that you see are only a part of the adults on your pet, and adults only make up 5% of the flea population: 50% are eggs, 35% larvae and 10% pupae.

Adults need blood meals to survive. They can live for a long period without a meal, but females must have a blood meal to lay eggs. She can lay up to 2 000 eggs in her lifetime. Fleas only lay eggs on pets. Once the eggs dry out they will fall off the pet and collect in your home and yard. Sandy areas may be particularly difficult to clean. Try very hot water to scald larvae and eggs.

Eggs hatch into larvae within one to 10 days. Larvae avoid light and migrate to dark places: cracks and crevices in your home or your pets’ kennel. They feed on a variety of organic substances, but predominantly dried blood from the host which is contained in adult fleas’ droppings. Larvae develop to pupae, which are resistant to most forms of control.

There is no one treatment that is going to kill all life-stages. Treatment has to be aimed at killing adult fleas on the dog to prevent itching and allergic skin disease and decrease egg production.

Eggs and larvae in the environment need to be controlled by environmental sprays or by cleaning the house and putting flea powder into the vacuum cleaner. Pets’ bedding need to be washed at temperatures higher than 60°C. 

Adult fleas are generally killed by contact with the insecticide or growth inhibitor in the product used. Eggs, which are on the dog and are exposed, will also be affected and will not hatch. Some products are absorbed into the bloodstream and the fleas need to feed before they are affected. Some products contain insect growth regulators and others insecticidal compounds or combinations thereof.

Cats are extremely sensitive to poisoning by insecticides and will develop severe neurological signs, which often progress to death if a dip or spot-on product intended for dogs is used on them.

Dips, shampoos, powders and spot-on applications are all effective. The advantage of spot-on is that the effect lasts much longer. Liquid dips need to be applied every seven to 10 days, and powders shake off within two to three days. Dogs which have a monthly parlour groom and dip are often not at all protected as the shampoo has a short lifespan.

Many of the spot-on treatments require the natural oils on the skin to distribute all over the body (Frontline®, Certifect®, Fiprotec®, Practic®, Activyl®, which treats fleas only, and Advantix®). It is essential that the animals are not washed two to three days before application so as to maximise the spreading. It is also not advisable to wash the dog two to three days after application. 

Other spot-on preparation, such as Revolution® and Advocate®, are absorbed through the skin and are systemic – the flea needs to feed to become affected.

Dosing is important. Spot-on treatments are sold in aliquots for different weight ranges. Sharing one pipette for two animals will result in unequal spread of the constituents and probable decreased efficacy.

You need to calculate the number of sprays your dog requires, especially with Frontline. Your dog needs 3 ml/kg – that is six sprays of the small container and three sprays of the larger containers. A few squirts along the back every time you see fleas is not going to be effective.

When returning home from high-risk area such as the coast, use a product that kills every flea on your dog within hours. Dose your pet with Capstar® a few hours before you depart, spray all bedding with an environmental spray or wash at temperatures higher than 60°C. Capstar® starts killing within 30 minutes, lasts 24 hours and is then out of the system.

Controlling fleas in the environment and on your pet will take at least three months.


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