How pesticides for dogs and cats work

Protecting our four-legged friends from unwanted guests is essential: ticksfleas and intestinal parasites can take a toll on their health. This is why science has developed molecules borrowed from agricultural pesticide researchadapting them to be safe on our animals. These molecules they selectively attack molecular structures of parasitesoften causing paralysis, but remaining safe for our animals (except for permethrin, safe for dogs, but highly toxic to cats). Whether they are in tablets, collars or spot on vials, there is something for all tastes: the important thing is always follow the instructions of your veterinarian.

What molecules are in pesticides

The first pesticides placed on the market date back to mid-19th centurywith the commercial production of pyrethruman insecticide designed for plants and then also used on animals. Their use developed in course of the twentieth centurywhile spot-ons and more delicate formulas have appeared since the 1990s. Historically, they are distinguished into ecto and endo parasiticides.

Ectoparasiticides

They include historical classes such as pyrethrins and pyrethroids, organophosphates and carbamatesup to more recent molecules such as phenylpyrazoles (fipronil), neonicotinoids, spinosins and isoxazolines, the latest to arrive on the market around 2014. These molecules act against external parasites such as fleas, ticks, mites, lice and insects, which, even if they are not lethal in themselves, can cause serious skin lesions, cause weight reduction and generally worsen the animal’s living conditions, not to mention that they can be vectors of other pathologies.

Endoparasiticides

This group includes molecules such as benzimidazoles, imidazothiazoles, tetrahydropyrimidines, praziquantel and emodepside. They act against internal parasites (endoparasites), such as intestinal worms (nematodes and tapeworms) and protozoa, which can cause both subclinical diseases and clinical manifestations with high morbidity and mortality.

Endectocides

A separate case is represented by pesticides that act on both internal and external parasites: they are endectocides. The following belong to this category macrocyclic lactones, which, starting from the 1980s, have contributed to making the distinction between “internal” and “external” pesticides less clear. The most represented molecules are ivermectinmilbemycin oxime, moxidectin, selamectin. Today, thanks to these molecules and the combined formulationsmany products allow you to simultaneously control multiple parasitic species with onesingle administration.

What is their mechanism of action

Most pesticides act on the nervous system of parasites, exploiting biological targets that are vital to the parasite but absent or very different in mammals.. Isoxazolines and fipronil, for example, block chloride channels regulated by gamma amino butyric acid (GABA) and glutamate: this causes hyperexcitation of the nervous system which leads to paralysis and rapid death of the parasite. THE pyrethroids they keep them open longer voltage-gated sodium channels, causing repeated nervous discharges. The target is different, but the result is the same: paralysis and death of the parasite.

THE macrocyclic lactoneshowever, work in the opposite but equally lethal way: they open the chlorine channels permanently, causing a flaccid paralysis. In intestinal worms, this prevents them from moving or feeding, leading to starvation or facilitating their expulsion through the intestine. Other molecules, such as emodepsideact on specific receptors (latrophilin) ​​that interfere with the neuromuscular coordination of the parasite. Finally, benzimidazoles act on fundamental cellular processes, blocking the cell division of parasites.

What types exist

The type of pesticide to use depends on the animal, its lifestyle and, obviously, the doctor’s advice. Each formulation has advantages and limitations: tablets reduce the risk for humans to come into contact with the drug, spot ons and collars pay for their convenience with a greater risk of exposure for people. Here are the types:

• Tablets: They can be useful for dogs. The active ingredient it is absorbed in the intestineand spreads into the blood killing the parasite. But try giving a tablet to a cat! Even the most appetizing and tasty ones can represent a real challenge.
• Spot on: for cats these vials are preferred and are usually squeezed onto the skin where the cat cannot reach by licking and can act locally in the skin lipid film or be absorbed systemically.
• Collars: comfortable due to their long life. They contain a higher concentration of active ingredient which is released slowly and they can even last several months.

How long do pesticides last, when to apply them and the risks

Most ectoparasite products guarantee a protection of at least one monthwhile some newer formulations, particularly isoxazolines, can offer coverage of up to three months. Even when choosing “when” to put them, everything depends on the life of your four-legged friend. In general, however, since they are used a preventive purposethey are often placed all year round, but it is always better to rely on the advice of the vet.

Given the selective toxicity towards parasites, pesticides are quite safe for our animal friends. Except in the case of permethrinsafe in dogs, but highly toxic to cats, which do not have the enzymes necessary to metabolize it. Even a few drops, even via the skin, can cause neurological disorders. Also overdoses and the simultaneous use of multiple products or incorrect dosages increases the risk of adverse effects. Finally, we must take into account the individual sensitivity of the animal: puppies, elderly animals or those with pre-existing pathologies may be more vulnerable.