Guide to Preventing Parasites.pdf - Royal Canin Canada

Praziquantel + febantel +
pyrantel
Injectable Dogs, cats 6 weeks
Drontal Plus Tablets Dogs, cats > 1 kg
Praziquantel + pyrantel Drontal Tablets Cats 4 weeks ou >1
kg
Pyrantel Pyran Tablets Dogs, cats 2 weeks
Pyr-a-Pam Tablets Dogs, cats 2 weeks
Strongid* Drench Dogs, cats 2 weeks
Pyrantel + oxantel Pyr-a-Pam Plus Tablets Dogs
Selamectin Revolution Topical liquid Dogs, cats 6 weeks
Sulfadiazine S-125 Tablets Dogs, cats N.A.
Toltrazuril* Baycox* Drench Dogs, cats 3 weeks
5.4 The residual effect
The residual effect of drugs has almost never been tested in pets. In herbivorous animals
kept on a pasture, it is relatively easy to approximately calculate the length of this period.
If the infection pressure is high, fecal samples are taken from the animals every week or
every other week. The animals are treated at the beginning of the period, and the interval
between when parasite egg-laying disappears and the reappearance of eggs in the feces is
calculated. Then we simply subtract the prepatency period from the calculated period to
obtain the duration of the residual effect.
Another way to do this, with experimental infections, is to treat the animal and infect it
after a determined period of time. Thus, administering infective Uncinaria larvae to dogs
treated 18 days earlier with moxidectin did not cause any infection in the animals (Epe,
2004). It can thus be conclude that, in experimental conditions, moxidectin persisted for
18 days in the animals at a concentration high enough to protect them against Uncinaria
infections. However, it would be risky, to say the least, to extrapolate this conclusion to
any other species of parasite, as long as it has not been investigated in a specific
experiment.
However, the duration of this residual effect is important in term of flea prevention.
Efficacy studies have carefully calculated this duration. For example, 27 days after
administering selamectin to a dog at a rate of 6 mg/kg of bodyweight, it was infested with
100 fleas. Seventy-two hours later, the animal’s coat was combed with an appropriate
instrument to find every living flea that was still present on the animal. Ninety-eight
percent of the fleas had disappeared (McTier et al., 2000). It can therefore be concluded
that the duration of the residual effect of selamectin against fleas is greater than 27 days.
However, the limits of our definition of “residual effect” should be spelled out
beforehand. We will thus need to determine the cutoff below which we consider that the
drug loses its efficacy. A number of products presently in use exhibit a residual effect
lasting approximately a month.
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