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The flea reproductive break point — what it is and how it is pivotal for successful flea control
The cat flea Ctenocephalides felis is a source of revulsion, distress and irritation for pet owners worldwide. In addition, C. felis can also cause flea allergic dermatitis (FAD) in susceptible pets as well as significant bite reactions in people. This in combination, with the cat flea’s capability of transmitting a number of vector-borne diseases, makes control of this parasite vital. Veterinary nurses play a key role in educating clients about fleas and putting practical control programmes in place. A crucial component of this is the flea reproductive break point, which if not considered will lead to failure of flea control programmes.
This article considers flea control, and the importance of the reproductive break point in ensuring that flea control strategies are successful.
Fleas (Order: Siphonaptera) are highly specialised insects with more than 2500 species worldwide. Adult fleas are small, wingless, laterally flattened, blood feeders with strong hind legs adapted for leaping. The flea most commonly seen on both dogs and cats is the ‘cat flea’ Ctenocephalides felis. C. felis is a source of revulsion, distress and irritation for pet owners but can also cause significant health-related issues for people and pets alike. It is a cause of flea allergic dermatitis (FAD) in susceptible pets as well as significant bite reactions in people. Anaemia may develop through blood loss if large numbers of fleas are present. C. felis acts as a vector for many flea-borne diseases including Rickettsia felis (the spotted fever agent), Haemoplasma spp. (the cause of feline infectious anaemia), bubonic plague (Yersinia pestis) and murine (endemic) typhus (Rickettsia typhi). It is also an intermediate host for the flea tapeworm Dipylidium caninum.
Control therefore is vital to reduce disease risks associated with infestation and avoid erosion of the human–animal bond. The veterinary nurse is at the forefront of flea control and development of control programmes with owners. This may take place in flea clinics or at reception where questions about fleas are frequently asked. This article considers flea control, and the importance of the reproductive break point in ensuring that flea control strategies are successful.
The success of the cat flea
The success of cat fleas and their dominance over other species of flea on domestic pets hinges on three factors.
Rapidlreproduction — adult fleas lay eggs (Figure 1) within 24 hours and can lay 40–50 eggs per day. The eggs hatch in 1–6 days and the larvae (Figure 2) can then pupate in as little as 10–20 days under warm humid conditions. Adult fleas can then emerge from pupae in 3 weeks. Under most household conditions, the life cycle can be completed in less than 8 weeks (Blagburn and Dryden, 2009). The speed and reproductive potential of this life cycle means just a few adult fleas can lead to heavy environmental contamination of homes very quickly and at any one time, 95% of the flea population exists in the environment as eggs, larvae and pupae (Blagburn and Dryden, 2009).
Persistentl environmentall stage — although adults can emerge from the pupae within a few weeks, if conditions are unfavourable then pupae can remain viable for 1–2 years (Blagburn and Dryden, 2009). This means that infestation can be established even if mammalian hosts have been absent for some time. Pupae hatch in response to heat and movement and so are reactivated by the presence of possible hosts. This can lead to people being bitten by fleas when entering properties that have been vacant for months or even years.
Parasitisel al widel rangel ofl mammalianl hosts — cat fleas can parasitise a wide range of mammals including dogs, rabbits, ferrets and wildlife such as foxes and hedgehogs. This adaptability allows infestation to continue in a wide variety of household situations and makes treatment of all susceptible pets vital to bring infestations under control. People are bitten by cat fleas but will not become infested themselves due to apparent innate immunity.
Figure 1. Adult cat flea and eggs.Figure 2. Flea larvae.
Understanding the reasons for the cat flea’s success is the key to establishing the steps needed for successful flea control. For flea elimination programmes to be successful adult fleas must be killed on the pet before they can initiate egg production. While growth regulators and environmental insecticides are useful at reducing larvae and eggs, they will have minimum effect on pupae in the environment and so effective rapid killing of adults is required to completely break the reproductive cycle.
The basis of flea control is therefore:
The use of an effective adulticide — to prevent egg laying and break the reproductive cycle
Effectivelenvironmentallcontroll— use of environmental sprays to reduce environmental factors and prevent growth. These sprays typically contain a larvicide/ovicide and a growth inhibitor. Lufenuron can also be used in pets to prevent flea eggs from hatching. Without treatment of the environment some flea infestations will take many months to eliminate (Dryden et al, 2000)
Managementloflclientlexpectationl— heavy infestations of fleas may still take at least 3 months to eliminate, even when environmental treatment is used (Dryden et al, 2000). If this is not made clear to clients they may become disheartened very quickly.
All of these factors are important to bring infestations under control as quickly as possible, limit dermatological signs and reduce disease transmission. It is the use of an effective adulticide however, that is the most important step. If egg laying can be prevented then persistent infestation will not occur. This makes it important to consider what the features of an effective adulticide are.
Effective adulticides and the reproductive break point
To effectively prevent flea reproduction a flea adulticide product must:
Kill 100% of fleas— if any fleas are not killed then reproduction and egg laying will continue. Use of a product that is not 100% efficacious or attempting to physically remove fleas is therefore fruitless.
Achieve 100% flea kill quickly enough to prevent egg laying—100% efficacy is not sufficient if the fleas are able to reproduce before they are killed. Adult fleas can lay eggs within 24 hours so effective adulticides must kill fleas at least within that time (Blagburn and Dryden, 2009).
Bel applied often enough to continue to prevent egg laying — the time after application at which fleas survive long enough in the presence of the product to lay eggs is known as the ‘reproductive break point’. If the reproductive break point is reached then flea control will fail.
A wide range of flea products are available which when applied correctly and frequently enough will achieve adequate control. Lists of the products may be found on the ESCCAP UK & Ireland website (www.esccapuk.org.uk) and the Veterinary prescriber subscription website (www.veterinaryprescriber.org). New products however, are frequently launched and license claims are constantly changing so it is important to refer to individual data sheets as well, to keep up to date with current products and license claims. Even when an efficacious product is used, a number of factors can affect the reproductive break point.
Swimming and use of shampoos— sebum stripping shampoos will increase the required frequency of application if compounds absorbed into this layer, such as fipronil and imidacloprid, are used. When frequent application of these shampoos are required such as in Malassezia spp. infection then flea products absorbed systemically rather than solely into the coat/sebum layer may be more desirable.
Ambiguous licensing claims — some license claims can be misleading and the individual patient should be considered. For example, fipronil spot on is licensed for 5 weeks in cats and for 2 months in dogs depending on level of challenge. The spray is licensed for 2 months in cats and 3 months in dogs. The license advises monthly application in flea allergic dermatitis cases, but in reality heavy infestations will require monthly treatment of all pets at risk of infestation to achieve control.
Size of dog—because the speed of the kill is proportional to the concentration of product administered, the reproductive break point is reduced in very large dogs at the upper end of the dose range. This needs to be taken into account if large dogs are on the border of a treatment dose range, e.g. a 40 kg dog being treated with a 20–40 kg product. These dogs may need to have product applied more frequently if adequate flea control is not being achieved.
Poor compliance — if clients are having difficulty applying a product or if finances are an issue they may try and increase the dosing frequency recommendation beyond veterinary and license claim advice. It is important for nurses to stress to clients that this will lead to control failure as the reproductive break point is reached. Practice plan schemes where, cost of flea treatments are spread, and discussing with clients whether they would prefer a spot on, tablet or collar preparation, will help to prevent this. Nurses demonstrating to clients how to apply products correctly are also useful to improve compliance.
If these factors are not taken into account, it may give the impression of flea insecticide resistance being present as flea control breaks down. Despite numerous large scale studies into the efficacy of POM-V flea treatments, fipronil and imidacloprid (Young et al, 2004; Beugnet and Franc, 2009; Dryden et al, 2011), there is currently no evidence of flea resistance in the field. Even where resistance genes are known to exist in laboratory strains of flea, fipronil, selamectin and spinosad have all been shown to be highly efficacious at 3 weeks post application (Bass et al, 2004, Dryden et al, 2013). If resistance is blamed for flea control failure by veterinary professionals and other factors affecting compliance and the reproductive break point are not considered, then control may continue to not be achieved, even if the flea product is changed. This is likely to lead to frustration on the part of the client and an increased risk of lack of compliance going forward as faith in the programme is lost.
To avoid this, veterinary nurses must help clients to understand the importance of the reproductive break point. By understanding the importance of giving the correct dose of flea product at the right frequency, compliance is improved and control maintained. Correct advice must also be given by nurses, both in terms or recommending efficacious products and the correct method and frequency of application. Often flea control will also form part of wider parasite control requirements such as ticks and endoparasites and so other parasite control requirements should be considered when deciding which flea treatment product to recommend. Giving this advice will often fall to veterinary nurses as advice is often sought at reception and nurse consultations rather than with the veterinary surgeon. Nurse flea consults are an ideal opportunity to spend time with clients, assessing their lifestyle and preferences before recommending a flea treatment/control protocol. Although many flea treatments are POM-V, requirements and treatment frequencies can still be assessed prior to POM-V treatment recommendation by a veterinary surgeon if this is required.
Conclusion
Flea control is important in terms of human nuisance and revulsion, reducing vector-borne disease and the clinical signs associated directly with flea infestation. Flea control continues to remain a challenge and it is vital for veterinary nurses and suitably qualified persons (SQPs) to remain up to date both in terms of new products coming onto the market, but also in giving accurate advice. Understanding the reproductive break point and using it to form the basis for this advice is crucial. By considering frequency of application and compliance, flea egg laying can be suppressed and flea control maintained.
Key Points
Ctenocephalides felis is the most common flea found on cats and dogs
C.felis is of veterinary significance as a vector of disease, cause of flea allergic dermatitis and a source of bites and revulsion to owners. This makes flea control vital.
Despite an arsenal of effective products, failures in flea control programmes are commonplace due to poor compliance, inappropriate drug use and unrealistic client expectations.
Understanding the concept of the flea reproductive break point is important in assessing why flea control programmes fail. It is also useful in helping owners to understand the importance of correct flea treatment dosing frequencies and application.
This article discusses flea control and the relevance of the reproductive break point to nurses giving flea control advice.
