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Fleas Infestation in Dogs and Cats

Flea infestation causes discomfort to pets (itching and irritation) and flea bites can lead to  more serious allergies resulting in itchy, crusty lesions, (flea allergic dermatitis) and hair loss. Fleas also carry and can transmit infectious agents (e.g. tapeworms, Bartonella agent of cat scratch fever).

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  • The clinical signs associated with fleas can vary, and some animals will show no clinical signs even with heavy flea burdens.

    Flea bites cause intense itching, which may lead to a rash, inflammation and hair loss for the pet. Fleas may also carry infectious agents that they can transmit to pets and even to people. If your pet is itchy and scratches, bites, rubs or licks its skin or coat frequently, flea infestation might be there. Sometimes fleas only cause a small amount of irritation to your pet, but if your dog or cat is bitten a lot (especially if it is a young puppy or kitten), this can lead over time to serious anaemia in some cases.

    Some dogs and cats react very strongly to flea bites. They develop an allergic reaction (Flea allergic dermatitis) to flea saliva and are troubled by persistent itching, which causes a tremendous amount of irritation and discomfort. Often this scratching will cause them to lick repeatedly and their coat can become sparse. Ultimately, this can lead to loss of hair and to skin inflammation and possible infection. Flea bite hypersensitivity is the most common hypersensitivity disorder of these animals. Affected animals generally manifest their pruritus (scratching) on the back half of the body including the tail head, thighs, and  abdomen. In cats, crusted papules can also be noted around the rump, head and neck. The clinical pattern of flea infestation varies from mild to severe.

    Fleas are small, narrow, dark brown creatures and can be detected crawling or jumping around in your pet’s fur. You may also see tiny black specs in your pet’s fur, this is flea faeces, made up of digested blood

    Summary of signs

    • Scratching, itching, skin licking
    • Hair loss, crusts
    • Bacterial skin infections
    • Flea Allergy Dermatitis (a hypersensitivity to flea saliva)
  • It is essential to identify and treat fleas quickly and effectively. How can you tell if your
    pet has fleas? If your pet scratches, bites and licks its fur more than usual, you can be suspicious of flea infestation. Some pets show few signs even with a heavy infestation, however, you may see fleas or flea dirt in the coat.

    A definitive diagnosis requires finding adult fleas and/or their droppings. Because they are so small, fleas are often difficult to detect and removing them can be more difficult than you think. You can check for fleas by running a special flea comb through your pet‘s fur. Along with looking for fleas, check also for tiny reddish black flea dirt. To confirm this, the flecks can be placed on a white wet paper towel: you will see reddish brown spots appear (due to the digested blood present in the flea dirt).

    Flea bite hypersensitivity is also the most common hypersensitivity disorder of these animals. Affected animals generally manifest their pruritus (scratching) on the back half of the body including the tailbase, thighs, and underneath the abdomen. In cats, crusted papules can also be noted around the head and neck. The diagnosis of flea allergic dermatitis is made using several pieces of information with the history, the clinical signs and the presence of fleas or “flea dirt”. On physical examination, the presence of fleas or flea dirts on the dog or cat is noted as well as the lesions and distribution of the dermatitis. An intradermal skin test can be used and will yield a positive immediate reaction in the majority of flea allergic animals. However response to therapy with a complete flea control program is the most commonly used.

    Because fleas can carry tapeworm larvae, any dog or cat that swallows an infected flea can also become infected. It has been known for humans, and children in particular, to be infected by the tapeworm. Good hygiene and avoiding face-licking can reduce the risk.
    It has been shown that fleas transmit cat scratch fever in humans via bacteria from the Bartonella genus. Although the classic symptoms of cat scratch fever (fever and lymph node swelling) are relatively benign, more severe forms of the disease may occur. These include generalised bacterial infection or localised joint pain and central nervous system disorders. An infected flea can infect a cat which in turn can infect a human by biting or scratching them. It is also thought that the disease might be transmitted directly from fleas to humans through biting.

  • It is essential to adopt the right strategy to prevent flea infestation by consulting your vet for advice.  Although it has advanced dramatically during the past few years, successful flea control can still be challenging. There are several once-a-month products for treatment that either are applied on to the animal‘s back or are given orally.

    Because most of the flea’s life cycle is actually spent off the host, it is important to treat both the environment and the pet. Pet owners should vacuum thoroughly, launder bedding and consider using a spray that helps control other life stages for quicker results. While some commercial products are effective against more than one life stage of the flea, none effectively kill the pupae stage. Some products are also effective in helping to manage the environment.

    The Treatment for fleas must therefore focus on three points:

    1.  Kill adult fleas on your pet quickly: Choose a flea treatment that kills fleas quickly on your pet to minimise the itching, irritation and risk of disease transmission caused by adult fleas.

    2. Kills flea eggs to stop further contamination of the environment: flea-infested pets continuously spread numerous eggs. Remember, 10 fleas can lay up to 15 000 eggs in one month! To stop further infestation of your home, you should select a flea treatment which also kills flea eggs.

    3. Kills flea larvae in the contaminated environment: 95% of flea stages are found in the environment. A flea treatment that also kills the flea larvae and existing eggs will help you to get rid of a flea infestation.

  • Once the flea infestation has been eradicated from your pet and its environment, you should continue to treat your pets regularly as this can considerably reduce the chance of flea re- infestations. Being proactive about prevention is important with any health condition. As fleas can be found all year round and can multiply rapidly, it is important to treat your pets on a regular basis – usually monthly. You should ask your vet and the practice staff for advice.

  • Question : I treated my cat for fleas with a spot-on preparation 2 weeks ago and I am finding fleas on him again . What has gone wrong?

    Answer : Have you treated his environment as well? If not, eggs are probably hatching in cracks between floorboards or skirting edges, from within the carpet or in his bedding , and they are jumping onto him . They will be killed by the preparation you have applied, but you must also vacuum the house and use a product that will help clear the environment of residual eggs and larvae. Your veterinary practice will be able to help you with this.

    Question : I have found small red sores on my legs and waist which are very itchy. My cat has fleas and someone has told me that the spots could be caused by flea bites. Is this true.

    Answer : Yes . Fleas from dogs and cats can bite humans and could cause small sores such as you describe. If you are concerned you should seek medical advice.

    Question : When I apply my spot-on product to my dog I only have to put it at the base of his skull . Does it really kill fleas that I have found near his tailbase?

    Answer : Yes. The spot-on contains a spreading agent that will ensure its effects reach the rest of the dog’s body.

  • Fleas are the most common of all external parasites found on pets. Ctenocephalides felis, the cat flea, is the most prevalent species of flea found on both cats and dogs. An infestation of fleas is both unpleasant and potentially dangerous for pets and their owners.

    A flea‘s life cycle lasts anywhere from a few weeks to a month, though under the right conditions it can continue for much longer. During the lifecycle fleas go through a complete metamorphosis in three main stages:

    • Adult fleas jump on to a host (e.g. cat, dog or human) and within minutes begin feeding on the host’s blood. The flea bites lead to itching and irritation and may also transmit serious diseases.
    • In less than 48 hours fleas begin laying numerous flea eggs that quickly fall off the animal into the environment.
    • In a few days these eggs hatch into flea larvae. These larvae dislike light and immediately crawl deep into carpets and cracks in floors making them hard to spot. The larvae spin cocoons in which they develop into pupae and when conditions are right they emerge as new adult fleas ready to jump onto a warm-blooded host and perpetuate the cycle.

    A single female can lay up to 50 eggs per day. In one month, 10 females could lay up to 15 000 eggs. The pet spreads flea eggs everywhere it goes, leading to a massive infestation in the home environment. A flea can jump as far as 33 cm in one leap, so infestation of other pets and humans is easy. Fleas measure 1-2 mm making them hardly visible. For every 5 fleas on the animal, 95 are invisible in the environment (eggs falling off the animal, existing eggs, larvae and pupae in the environment). The whole home, including carpets, sofas, beds and the entire environment of the pet can be heavily infested by flea eggs and larvae, which are the seeds of future pet re-infestation. Vacuuming will only remove a small number of eggs and larvae because they are hidden deep in floors and rugs, and entwined in the fibres. Fleas can survive up to 6 months in the environment.

    A single flea will bite its host around 10 times a day and ingest up to 15 times its weight in blood. Fleas also start to feed very shortly after landing on their host; 25% of fleas take their first feed within 5 minutes and 97% within an hour. This means that in cases of heavy infestation, fleas can produce anaemia in otherwise healthy animals, and in extreme cases, even death in smaller animals.

    One of the main factors that allow fleas to rapidly complete their lifecycle is warmth, central heating therefore means fleas can reproduce all year round.

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