15 Apr 2025
Ian Wright
Job Title
Image: Mauricio / Adobe Stock
Fleas are highly prevalent on domestic cats and dogs across the UK, with 28.1% of cats and 14.4% of dogs having been demonstrated to be infested; 11.3% of these infestations were found to be harbouring Bartonella species, which are zoonotic with potential to cause chronic morbidity and even be life threatening in immunosuppressed individuals (Abdullah et al, 2019).
As a result, pet owners are likely to seek flea control advice either because of existing infestations or for routine prevention.
Many flea products may now be purchased outside of veterinary channels and some without prescription. This often results in products being purchased without adequate advice on which product to choose, how to apply it correctly and how often to use it. This is likely to result in poor flea control and increased environmental exposure to product through misuse.
Veterinary professionals, therefore, must take every opportunity when interacting with pet owners in practice or through social media channels to give advice on which products to choose, based on lifestyle and compliance. Several factors need to be considered when selecting a flea product.
Adult fleas can lay eggs within 24 hours, so the adulticide chosen must kill fleas at least within that time for control to be achieved. They must also be administered frequently enough to prevent flea egg laying.
The time after application of the adulticide at which fleas survive long enough to lay eggs is known as the “reproductive break point”. If the reproductive break point is reached, then flea control will fail. It is important to discuss duration of activity with owners, both regarding products they are currently using and ones they might select in the future.
Many non POM-V flea tablets contain nitenpyram, which, while effective, has a very short duration of action. The frequency at which this would need to be applied as a single means of flea control is prohibitive for both preventive treatment and for controlling existing infestations. More typical durations of action for products include the following.
Monthly or four-weekly. Many isoxazoline tablets and spot-on preparations containing fipronil, imidacloprid or selamectin have this duration of action. It is important to check whether treatment is four-weekly or monthly on the product licence to ensure treatment gaps do not occur – particularly in controlling existing infestations. If monthly deworming for Toxocara species, lungworm or tapeworm is required, then this frequency may be selected to make the timing of all parasite treatments coincide. Some owners also prefer keeping track of medications by calendar month.
Every 12 or 13 weeks. Spot-on preparations and tablets containing fluralaner have a 12-week duration of action, and a spot-on preparation for cats containing tigolaner, emodepside and praziquantel has a 13-week duration of action against fleas and ticks. These durations of action are useful where treatment for worms approximately every three months is also indicated and parasite treatments can coincide.
Every six months. An injection for cats containing lufenuron lasts six months. This does not kill fleas, but prevents flea eggs from hatching. It is useful where cats are kept entirely indoors and frequent exposure to large numbers of fleas is unlikely. For existing infestations, an adulticide will need to be used initially alongside treatment of the home to help resolve irritation and conditions such as flea-allergic dermatitis.
Longer than six months. A collar containing flumethrin and imidacloprid is licensed for seven to eight months’ protection against fleas and ticks. Its efficacy is likely to be reduced by frequent swimming or shampooing, and use in pets with these lifestyle factors should be avoided. A fluralaner injection for dogs with 12 months’ duration of activity against fleas and ticks has been developed. These longer-acting treatments are useful where the administration of spot-on and tablet treatments is difficult, and where requirements for deworming frequency are low.
It is vital that clients feel confident administering a product and in its efficacy. Preference for spot-on, collar, tablet or injection should be discussed, and whether a preference exists for monthly or longer-acting formulations.
If the owner is not happy with the administration and formulation of a product, or simply unable to apply it, then compliance and subsequent control will be lost. By involving the client in the decision-making process, they are more likely to be happy with the mode of application and compliance is improved. A number of points in this regard should be discussed with the client.
Even if all these techniques are employed, some pets will be uncooperative to the point where it is impractical or dangerous for owners to attempt to administer products. In this situation, administering products in practice may be the only way to ensure correct application and compliance. In these cases, long-acting products are more practical.
Frequent swimming or shampooing may affect the efficacy and duration of action of some imidacloprid and fipronil products, and may also lead to environmental contamination (Perkins et al, 2024; Yoder et al, 2024), so this should be considered when choosing a specific product.
Pyrethroids should be avoided in cats due to toxicity concerns, except for flumethrin (present in Seresto; Elanco). Particular care should be taken to ensure correct dosage when using licensed macrocyclic lactone products in multidrug resistance mutation 1 (MDR1) breeds, such as the collie. Products containing moxidectin and milbemycin should not be used in combination in the absence of large-scale safety studies indicating their safe use in combination.
Owners may have concerns regarding adverse events from personal experience of using products or from reported adverse events in the press or on social media. Some of these events may represent true adverse reactions, whereas others may have no link to the product.
Any real or perceived event will make owners reluctant to use products, and any concerns should be taken seriously. Any suspected adverse event in the practice should be reported and the owner reassured that it will be taken seriously and investigated.
If concerns arise from reported cases that have occurred elsewhere, then it is important to emphasise to clients that while adverse events can occur when any product is used, they are rare for licensed products used as indicated.
After discussion and reassurance, if owners are still doubtful about the safety of a product, then an alternative should be offered. Clients are unlikely to confidently use a product they perceive may be harmful to their pet. Data sheet information should also be used, such as safety data on use during pregnancy and lactation.
Many effective flea and tick control products are also licensed for the treatment and prevention of endoparasites such as intestinal roundworm, tapeworm and lungworm.
By considering overall parasite control while keeping the number of products used to a minimum, compliance will be improved, as the owner has fewer products to administer.
The use of broad-spectrum parasiticides and endectocides will reduce the number of treatments required for owners to administer where broad-spectrum parasite cover is required. In the case of endectocide products containing more than one compound, owners should be reassured that safety studies will have been carried out to ensure combination of products are as safe as possible, as long as data sheet guidance is followed.
If only flea control is required, the monovalent products containing imidacloprid are available. These may not be the most suitable, however, if the pet frequently swims or is shampooed.
Effective treatments can be expensive, and owners may be tempted to try to increase the time between treatments or to purchase products away from the practice that are less effective.
Practice websites, social media and waiting room posters, displays and materials are opportunities to emphasise the advantages that products bought in practice bring. These may include high efficacy, a wide range of parasites treated, long duration of action and safety.
These messages can also be combined with application and control advice, improving client bonding to the practice and giving a feeling of value for money. Costs can be spread through practice plans or reduced through discounts on multiple treatments, or on purchases with deworming products or parasite screening tests.
The whole practice team has an essential role to play in helping clients select the best flea treatment for their pet and maximising compliance.
Increased pet owner compliance and adherence to prescribed treatment protocols is essential for good preventive treatment outcomes.
By discussing preferences, lifestyle and overall parasite control needs, products can be selected that clients are willing and able to administer effectively, and at the correct frequency.
In doing so, parasite control is maximised while reducing the risks of adverse events and environmental contamination.
In an increasingly busy practice environment, information can also be disseminated via waiting room materials, websites and social media.
