Active Chemical Groups
It is important to understand what the chemicals do if you are to implement a successful worming program. This will ensure that whatever your worming strategy you give a wormer fit for purpose.
Praziquantal and Pyrantel Embonate
Moxidectin and Benzimidazole (5 days)
Adult Redworm and Roundworms
Ivermectin, Moxidectin, Pyrantel Embonate, Benzimidazole
Lungworm & Bots
Ivermectin and Moxidectin
A detailed table showing the complete range of each chemical is at the bottom of this information page, and a summary of the coverage of each chemical is listed below.
Praziquantel is a chemical that is only effective against tapeworm, however it has a larger range than pyrantel embonate (Strongid P / Pyratape P/ Exodus/Embotape) and attacks the three specie of tapeworm. It is available on its own in a single syringe (Equitape), combined with the ivermectin chemical (Equimax / Eqvalan Duo) or with the moxidectin chemical (Equest Pramox). When used on its own it should be an additional treatment in a chemical worming program as it has no coverage against any of the roundworms. This is of benefit if using in a strategic program to reduce the resistance of the roundworm to worming chemicals. Only Equimax is licensed for use in pregnant and lactating mares and foals from two weeks of age.
Pyrantal can be used as a base wormer in a chemical rotational worming program. When used at double the standard recommended dosing rates it is effective against A.perfoliata tapeworm. It is effective against many adult roundworms.
Fenbendazole (Panacur) and Menbendazole (Telmin) have a large coverage range against roundworms, both adult and larvicidal. When Fenbendazole is given over 5 days (Panacur Equine Guard) it is also effective against encysted small redworm larvae. Some horses in the UK have worms that are resistant to the benzimidazole chemicals. These can be identified using worm egg counts. However, the 5-day treatment still works on the larvae of resistant adults, and should be used in Nov to reduce the levels of worms encysting in the winter and emerging in the spring.
Macrocyclic Lactones has the largest range of impact on worms. Ivermectin affects most adult and larvicidal roundworms and also includes lungworm and bots. It should be the main chemical in worming programs for donkeys and should be in every worming program during the winter months to control bots. It should be given after the first frost, which is when the adult bot fly will be eliminated. If it is given any earlier then the bot fly could re infect the horse.
Ivermectin is extremely dangerous to fish and aquatic life. Treated animals should not have access to ponds, waterways, ditches and surface water.
Dogs and cats can also be adversely affected by the ivermectin and should not have access to spilled paste or used syringes.
Although moxidectin is from the same chemical groups as ivermectin it has slightly different coverage. The effect of the chemical is longer and it also works on encysted small redworm larvae. It is not licensed for use in foals under four months of age and can cause reactions at only twice the normal dose in foals and three times the normal dose in adults. Each syringe only treats 575kg so for horses over 15.3hh, more than one syringe may be required.
Moxidectin is extremely dangerous to fish and aquatic life. Treated animals should not have access to ponds, waterways, ditches and surface water.
Dogs and cats can also be adversely affected by the moxidectin and should not have access to spilled paste or used syringes.
Detailed Chemical Comparison Table
The table below shows in detail how each chemical is effective against different types of worms and some treat both adult and larvicidal stages.