What’s new in companion animal parasite control? - Veterinary Practice
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What’s new in companion animal parasite control?

RENATA TURLEJ of MSD Animal Health reviews recent developments in parasite control which provide veterinary surgeons with greater flexibility in their choice of preparations

FLEA control has always been a need at the epicentre of the small animal veterinary practice and the options for managing seem to increase every year.

With the plethora of ectoparasiticides available, in order to implement optimal flea control it is essential to understand the mode of action of the selected products to have a realistic expectation of the results.

The potential pitfalls of implementing an effective flea treatment strategy lie with the owner as well as the vet. Educating the client is essential to ensure good compliance if the treatment strategy is to work at its best, so ensuring correct advice is given and taken on board by the pet owner is every bit as fundamental as the choice of preparation.

This area is a particular concern, not least when sales of these products are increasingly outside the influence of the practice.

Key points which need to be put across to the client are:

  • eliminating adult fleas is the tip of the iceberg of the problem;
  • effective environmental control is required for optimal management;
  • reducing environmental biomass with regular vacuuming, washing of bedding, etc.;
  • correct product application and discipline in the frequency of use.

Pupal-window effect

The continual or delayed emergence of fleas from the pupal stage is known as the pupal-window effect and is attributed to the resilience of existing flea pupae in the environment.

As a consequence, it may take several months of regular treatment to fully eradicate a heavy infestation, with a correspondingly large environmental biomass, in spite of the implementation of optimal flea control using effective ovilarvical products.

In addition to an effective flea product, persistence and consistence are key to obtaining a flea-free household.

The choice of insecticidal actives available varies widely and selection should be based on what the veterinary surgeon is trying to achieve: flea control, with or without ovilarvicidal activity, targeting specifically the flea or, if there is a requirement, other ectoparasites, including mites and lice.

Vets should be aware of the mode of action of the active and, in particular, the stages of the life-cycle that it treats. Choosing an effective adulticide will have major limitations without effective environmental control.

Main considerations

The main points to be considered when choosing your active are:

  • What stages of the flea lifecycle are treated?
  • How long will the treatment last?
  • When should I expect the flea problem to be controlled?
  • Is there any known resistance to the molecule?

Manufacturers are constantly searching for novel methods to tackle the on-going flea problem that can help improve efficacy, safety or convenience.

The active, indoxacarb, was recently introduced into the veterinary ectoparasiticides market. It is a “novel” molecule with no known flea resistance.

It is essentially a pro-drug which is converted into its active form inside the flea, using gut enzymes, by a process called “bioactivation” which delivers targeted flea control at the site it’s needed – the flea.

Studies have shown a rapid onset of action and persistent levels of efficacy throughout the 28-day application interval. Egg production is affected immediately after application and is inhibited within 72 hours, thereby completely disrupting the flea life-cycle.

Ingesting debris

Flea larvae, found mainly in the environment, are similarly destroyed by the bioactivation process as they ingest the organic debris, mainly skin cells, coated in indoxacarb which are sloughed off during the natural shedding of skin cells in the regeneration process.

In a recent study carried out by M. Dryden on healthy cats, Activyl, containing the active indoxacarb, was shown to have 100% efficacy against the cat flea, Ctenocephalides felis, over a 28-day period whereby cats were infested with fleas on days -2, 7, 14, 21, 28, 35 and 42 (Figure 1).

It continued to maintain a high level of efficacy on days 35 and 42 at 99.6%, up to two weeks after the required subsequent treatment date.

Flea egg production was inhibited by 66% or two-thirds within 24 hours and only 4% of the eggs laid during this time managed to hatch.

Indoxacarb is an active suitable for vets wanting to implement a specific flea-targeted treatment, with a persistent duration of efficacy and environmental control.

Making sense of parasite control

Products containing a combination of actives also target some of the important intestinal worms, Angiostrongylus vasorum and for dogs travelling to heartworm-endemic areas Dirofilaria immitis, but no single preparation is effective against the full range of ecto- and endoparasites we might want to control.

With new claims and new technologies come a greater range of options for controlling the spectrum of parasites we wish to manage (Figure 2).

Milbemax contains both milbemycin and praziquantel which provides broadspectrum worming including tapeworm.

Comprehensive cover

Given the recent licensed claim for prevention of Angiostrongylus for Milbemax, the use of this product in conjunction with the MSD range of ectoparasiticides gives optimum flexibility and choice to provide comprehensive endectocide and ectoparasiticide cover to suit a wide range of requirements in practice.

These recent changes and developments in parasite control provide veterinarians with greater flexibility in their choice of preparations in the persistent battle they face against common parasites affecting our companion animals.

For further information go to www.bioactivation-in-fleas.co.uk


Dryden, M. W., Payne, P. A., Smith, V. et al (2013) Efficacy of indoxacarb applied to cats against the adult cat flea, Ctenocephalides felis, flea eggs and adult flea emergence. Parasites and Vectors 6: 126.

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