DELIVERY FORMS of veterinary PARASITICIDES to DOGS, CATS, HORSES and LIVESTOCK - cattle, sheep, goat, pig, poultry

The way a parasiticide is best delivered or administered to an animal is often not essential for its efficacy, and a choice is often possible, e.g. between ivermectin administered as injectable, as a pour-on, as a drench or as a feed additive. To make a decision, it is good to know what are the pros and cons of the different delivery methods, and what alternatives are available.

On-animal and off-animal treatment of livestock and pets with parasiticides

Basically, veterinary parasites of livestock - cattle, sheep, goats, pig, poultry - dogs and cats can be controlled with products that are applied on-animal or off-animal.

On-animal treatment is most frequent against:

• All internal parasites such as roundworms, tapeworms, flukes, etc. and
• Those external parasites that spend all or at least part of their life-cycle on their hosts, e.g. lice, mites, fleas, ticks, etc.

Typical on-animal treatments are injectables, pour-ons, spot-ons, drenches, etc.

Off-animal treatment is often the best choice or a recommended complement against parasites or nuisance insects that spend a substantial part of their life-cycle in the environment, i.e. off the host, e.g. houseflies, filth & nuisance flies, mosquitoes, etc. Off-animal treatment is often preferred on dairy operations and layers because they do not leave undesirable residues in milk or eggs. The most frequent off-animal uses of veterinary parasiticides are:

• Baits containing insecticides: used abundantly against houseflies, filth & nuisance flies.
• Premise and environmental treatment of surfaces, manure, ponds, etc.: used e.g. against houseflies, stable flies, mosquitoes, etc.
• Traps: used against certain flies such as houseflies, filth & nuisance flies, tsetse flies, blowflies, etc.

Internal use and external use of parasiticides

Parasiticides for on-animal treatments of livestock and pets can basically be for external use, or for internal use.

External use, also called topical use. The most relevant delivery forms of parasiticides for external use are:

• Collars impregnated with insecticides; used only on pets.
• Dipping: used mainly on cattle, sheep and goats.
• Dressing: used on livestock, horses and pets.
• Dusts, back rubbers and other self-treatment devices: used mainly on poultry, pig and cattle.
• Ear-tags impregnated with insecticides: used only on cattle.
• Pour-ons: used mainly on cattle, sheep, horses, goats and pigs.
• Shampoos, soaps, sprays, powders, creams and the like: used mainly on pets.
• Spot-ons: used mainly on dogs and cats, very seldom on livestock.
• Spraying: spray-races, hand spraying, jetting, etc: used mainly on livestock and horses

Internal use, usually divided into enteral use (=oral administration) or parenteral use (=injection). The most relevant delivery forms of parasiticides for internal use are:

• Additives for feed or drinking water: used mainly on pig, poultry as well as horses, less on cattle and sheep, seldom on pets.
• Injectables: used mainly on cattle, sheep, goats and pigs; scarcely on poultry, pets, and horses.
• Drenches = Oral liquids: used both on livestock (drenches) and to some extent in pets.
• Pastes & gels = Oral semi-solids: used mainly on horses, a few products also for pets.
• Tablets, pills, etc. = Oral solids, etc. used mainly on pets and poultry, scarcely on ruminants and pigs.
• Slow-release boluses: used mainly on ruminants, i.e. on cattle, sheep and goats.

Whether a particular parasiticide product is for external or internal use does not depend on whether the parasite to be controlled is an external parasite (ectoparasite) or an internal parasite (endoparasite). This means that both ectoparasites and endoparasites can be treated with parasiticides for external or internal use, and vice versa.

It is obvious that not all antiparasitic active ingredients can be administered and are available in all the delivery forms mentioned above. E.g., pet wormers are available almost only as tablets or drenches for oral administration or a few as spot-ons for topical administration. And some particular delivery forms may be available in certain countries and not in other ones.

Remember, that we are talking here about parasiticides (i.e. antiparasitics) and what applies to parasiticides may not apply to other veterinary medicines (e.g. antibiotics, anti-inflammatory drugs, anti-bacterial and anti-viral vaccines, hormones, etc.).