The problems that fleas can cause families Print E-mail
Written by Rebecca Stevenson MA Vet MB MRCVS is Veterinary Technical Manager at Merial Animal Health Ltd.   
Most people are aware that fleas can cause problems for the cats and dogs that they infest, but fewer people are aware of the wide-reaching problems that a flea infestation can cause for the whole family.  A recent survey carried out by Merial Animal Health Ltd confirmed the importance of flea infestations in dogs and cats. Thirty-one veterinary practices in the UK examined every dog and cat entering their practice in a one-week period in July 2005. It was found that over one in ten cats and dogs had a flea infestation. Worryingly, the pets’ owners had noticed fewer than 50 per cent of these infestations and nearly 40 per cent were unaware that, if their pet had fleas, so did their home[1].

Tip of the iceberg

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The fleas seen on pets are just the tip of the iceberg. Ninety-five per cent of any flea infestation exists unseen as eggs, larvae and pupae in the pet’s environment. Adult fleas lay eggs on the pet’s coat, which fall off into the home. The flea problem escalates quickly as female fleas can lay up to 50 eggs in a day or 1,500 in a lifetime. A pet with fleas acts like a saltshaker, sprinkling flea eggs throughout the home wherever it goes.

The eggs hatch into larvae, which are photophobic and geophilic. They therefore move away from light and burrow deep into nooks and crannies in the flooring and furniture. Before becoming an adult flea the larva develops a protective cocoon around itself, forming a pupa. Pupae can lie dormant for a considerable time (even as long as a year) before hatching out to re-infest the pets or to bite humans.

A problem for pets


Fleas can cause many problems for the pets they infest, including skin irritation, pruritus and anaemia. Some pets are allergic to flea faeces and/or flea saliva and will suffer a particularly severe skin reaction. In addition, fleas can carry and transmit diseases to their host such as tapeworm (Dipylidium spp.), cat scratch disease (Bartonella henselae), Rickettsia felis and Haemoplasma species. Any pet-loving owners will want to protect their pets from all of these problems, but they are unlikely to be aware of the risks that these fleas could be posing to their family.

A problem for human health


It is a common misconception that when humans are bitten by fleas they are bitten by fleas that jump directly off the pet. In fact, humans are most commonly bitten by newly hatched fleas jumping from the environment in search of their first blood meal. This explains the common pattern of fleabites, which are found on the ankles and the lower parts of the legs.

Most people will suffer mild skin irritation at the site of the bites, with visible red papules in the skin. Some people, however, can be allergic to flea saliva and suffer a more severe skin reaction.Unfortunately the problem of human fleabites can run a lot deeper than just skin irritation. We have already indicated that fleas can transmit some blood-borne diseases to the pets they infest, and some of these diseases can affect humans too. Fleas play an important role in the transmission of bubonic plague (Yersinia pestis)[2]. Historically bubonic plague has been responsible for thousands of human deaths in the UK.

More recently, a study has demonstrated that 50 per cent of fleas in the UK are positive for at least one pathogen when tested using polymerase chain reaction (PCR) techniques. Seventeen per cent were shown to be positive for Bartonella henselae, which causes cat scratch disease, and 21 per cent were positive for Rickettsia felis, which induces a spotted fever syndrome in humans. Forty per cent were positive for Haemoplasma species and 20 per cent were positive for more than one pathogen[3].

It was commonly accepted that cat scratch disease was transmitted from cat to human via scratches or bites, but it is also possible that it is transmitted indirectly by inoculation of infected flea faeces through skin abrasions[4].

Cat scratch disease generally causes a mild and transient flu-like illness involving enlarged lymph nodes and fever. In most cases it resolves spontaneously but in some cases, such as in elderly or immuno-compromised individuals, a more severe disease may be observed and less typical manifestations may be seen such as endocarditis and ocular disease[5,6].

In addition, a systemic disease with prolonged fever and micro-abscesses in the liver and/or spleen has been reported in association with cat scratch disease[7].

Rickettsia felis is transmitted directly through fleabites, and can be maintained in cat fleas by vertical transmission for up to 12 generations without the benefit of an infected host[8]. The clinical features in humans include fever, marked fatigue, headache and a generalised maculopapular rash9. Antibiotics seem to be successful in treating Rickettsia felis infections.

A problem in the home


It is common for people who are unaware of the details of the flea lifecycle to assume that by using an effective flea control product on their pet they can quickly get rid of a flea infestation. Unfortunately once owners see fleas on their pets, the build-up of eggs, larvae and pupae in the home will already be underway. There are environmental sprays that can be used to kill flea eggs and larvae in the home, but the real problem lies with the flea pupae – inside their cocoons they are protected from environmental treatments. This means that new fleas will hatch and will be seen for several weeks or months after the start of the flea control programme. This is normal and these fleas will be killed when they jump on to a pet that has been treated with an effective flea product. The sight of live fleas on a treated pet can be perceived as a problem by pet owners if they are unaware of the lifecycle and are not expecting to see any fleas after they start their flea control measures.

So good education at the point of sale for any flea product is critical to ensure customer satisfaction. For example, pupae can be encouraged to hatch by vacuuming regularly and making sure the house is warm. Washing the pets’ bedding regularly may help with the mechanical removal of flea pupae and it is important to ensure that pets have continued access to infested areas of the house so that they can act like a ‘flea vacuum’ by picking up any newly hatched fleas from the environment. This will also help to reduce the likelihood of fleas biting humans in the house.

To ensure ongoing protection it is important that pets are treated all year round. With central heating, the problem of fleas does not stop in the winter. It is important to use a product that will give several weeks of flea control to provide the pet with ongoing protection from new infestations.

References


1. Bond et al. A survey of flea infestation in dogs and cats in the UK during 2005. Accepted for publication in The Veterinary Record.
2. Hinnebusch BJ. The evolution of flea-borne transmission in Yersinia pestis. Curr Issues Mol Biol 2005; 7(2): 197–212.
3. Shaw SE et al. Pathogen carriage by the cat flea Ctenocephalides felis (Bouché) in the UK. Vet Microbiol 2004; 102: 183–188.
4. Foil L et al. Experimental infection of domestic cats with Bartonella henselae by inoculation of Ctenocephalides felis (Siphonaptera: Pulicidae) feces. J Med Entomol 1998; 35(5): 625–628.
5. Curi AL et al. Ocular manifestation of cat scratch disease in HIV positive patients. Am J Ophthalmol 2006; 141(2): 400–401.
6. Ben-Ami R et al. Cat scratch disease in elderly patients. Clin Infect Dis 2005; 41(7): 969–974.
7. Liao HM et al. Systemic cat scratch disease. J Formos Med Assoc 2006; 105(8): 674–679.
8. Wedincamp J Jr, Foil LD. Vertical transmission of Rickettsia felis in the cat flea (Ctenocephalides felis Bouche). J Vector Ecol 2002; 27(1): 96–101.
9. Parola P et al. Tick and flea-borne rickettsial emerging zoonoses. J Vet Research 2005; 36: 469–492.
 
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