Fleas are known to transmit tapeworms as well as bacterial and viral pathogens to both companion animals and humans. Moreover, the presence and blood-feeding of these parasites often results in allergic reactions and can cause a substantial blood loss. This emphasises the necessity of efficient flea control.

The cosmopolitan distribution of fleas and the fact that they are major nuisance pests, a matter of public health and the source of FAD, make control definitely necessary. Regular application of parasiticides to prevent flea infestation is a common strategy in veterinarian practice. A lot of different flea control products are provided by the pharmaceutical world, with many of them exhibiting almost 100% efficacy. Major differences regarding the speed of action and the issue of resistance are due to the active substances.

If a substance possesses a fast mode of action, the probability decreases that transmission of pathogens occurs within the remaining feeding time. With imidacloprid, Bayer provides a proven active ingredient, which effectively stops flea feeding within minutes.

The regular use of preventative products to avoid infestation of the animals and consequently their environment is recommended.

Resistance in fleas against frequently used flea control products is an issue of major importance. Flea control measures should be designed to minimise the risk of resistance developing with incorrect dosing. In 1999, Bayer started a global flea susceptibility program to monitor possible resistance developments against imidacloprid in fleas. In more than 1,800 Ctenocephalides felis isolates bioassayed between 2002 and 2017 no evidence of a decreased susceptibility to imidacloprid could be observed (Rust et al., 2018). Due to the nature of flea infestations, with the majority of development stages in the environment and less accessible to treatment, the elimination of an established infestation can take considerable time and measures need to be followed stringently to avoid failure.But often, biological factors like reinfestation from refugia on domestic and wild animals, or the failure of adjusting insecticide application to variations in humidity and temperature – or cultural conditions such as substrates or even carpet types – may cause control failures.


There are two main reasons why flea larvae escape most adulticidal treatments indoors:

  1. The treatment fails to reach them at the base of carpet fibres where they develop
  2. Larvae are less sensitive to treatment and about 2.5-times more insecticide per gram body weight is required to kill larvae than adults (Dryden and Rust, 1994)


Also the ‘pupal window’, describing the fact that the pupal stage can be as short as ten days, but the preemerged adults might remain in the cocoons for up to six months may cause problems in control measures and has to be understood by pet owners (Dryden, 1996).

Fleas may continue to emerge from cocoons for up to four weeks after insecticide and insect growth regulator application to the environment (Dryden and Prestwood, 1993). These resurgences are attributed to the presence of pupae and preemerged adults in cocoons at the time of treatment.


Dryden MW: A look at the latest developments in flea biology and control. Vet Med Suppl. 1996, 3, 3-8 

Dryden MW, Prestwood AK: Successful flea control. Comp Cont Educ Pract Vet. 1993, 15, 821-31 

Dryden MW, Rust MK: The cat flea: biology, ecology and control. Vet Parasitol. 1994, 52, 1-19 

Rust MK, Blagburn BL, Denholm I, et al.: International program to monitor cat flea populations for susceptibility to imidacloprid. J Med Entomol. 2018, 55, 1245-53




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