Antiparasitic treatments are drugs designed to limit, eliminate, or destroy all or part of a population of pathogens commonly called parasites, i.e., different from bacteria and viruses that could threaten your horse. They include, depending on the nature of the parasite species, antifungals (against fungi), antiprotozoals, acaricides, insecticides and anthelmintics (against worms). Their use on horses must follow certain rules.
Routine treatment, prevention, or treatment of a horse with parasites
The first case must be part of a prophylaxis program, integrating many criteria. The second case must consider the fact that it is a weakened subject whose natural defenses and elimination capacities may be reduced.
Who is treated, what is treated and where?
An antiparasitic treatment (or another type: antibiotic, anti-inflammatory…) is prescribed for a specific subject who has been precisely diagnosed, in this case suffering from an identified parasitic disease or a group of known parasites. It can be extremely dangerous to extend a drug that has already been used for others to other identical individuals with similar disorders.
The use of an antiparasitic drug is subject to dosage rules and contraindications
It is important to know the characteristics of the product (precise spectrum, dose, route of administration, frequency of use) and its side effects and toxicity (sensitive subjects, very young, pregnant females, suffering from other diseases). All this practical information appears on the prescription issued by a veterinary doctor, who alone can take responsibility for prescribing a drug outside its regulatory use.
It is essential:
- to consider that there is no molecule likely to kill all parasites, even those belonging to the same group or located in the same apparatus (for example tapeworms and strangles);
- not to aim absolutely and constantly at a “zero parasite” state: the aim is to limit the parasite population and not to eliminate it totally because the horse will not develop any effective immune response against them;
- to consider the external environment and the other animals recontamination a decontamination subject. Treating a living animal within a group is sometimes useless;
- not to conclude that a molecule is inactive because the horse presents the same parasites afterwards, because it is usually a recontamination.
The disadvantages linked to the incorrect use of antiparasitic are varied and some of them are potentially serious:
- first of all, risks of intoxication due to the administration of a substance not intended for the horse (a fortiori when it is a matter of substances intended for the external environment as for example for the treatment of premises against insects) or, by a route not retained by the producing laboratory (the intravenous route instead of the intramuscular route) or, with an erroneous dose (error in the dose used, in the weight of the animal).
Molecules such as levamisole or amitraz are practically forbidden for use in horses or are potentially dangerous;
- these risks are also to be taken into consideration for the owner or the person in charge of applying an insecticide for example, a molecule sometimes toxic for humans;
- Finally, erroneous treatments, based on an underestimated dosage, according to inaccurate rhythms, can favor the appearance of resistant parasites, i.e., having the capacity to survive to doses of “normally” effective drugs. This leads to therapeutic failures that are difficult to manage.
