Moxidectin is regarded as the bird wormer of choice by most veterinarians.

It is effective against roundworm, hairworm and any external parasites that feed off body fluids (i.e. mites, pigeon flies & lice). It can be used during moulting and breeding and can either be given in its concentrated form directly into the throat or alternatively diluted into the drinking water. (5ml to 2litres of water).

It is also well absorbed through the skin and can therefore can be applied topically (blow the feathers apart at the back of the neck and put one drop on the bare skin [as you would with ivermectin 1% spot-on] - wear gloves to prevent absorption into your own skin.  This can be  easier for small birds such as canaries and budgerigars.

The drug has a wide safety margin and birds can be fed and watered normally during its use.

Often how products work and how they were developed is really interesting. Moxidectin is no exception.

There is a group of chemicals called macrocyclic lactones. Within this group are two sub-groups. One group is the avermectins. This includes ivermectin, which most fanciers will be familiar with. The other group is the milbemycins. The milbemycin group only contains two drugs, namely milbemycin and moxidectin.

Incredibly, ivermectin was originally isolated from the fermentative broth of a fungus called Streptomyces avermitilus.  Researchers having found such a useful drug in one type of Streptomyces kept their eyes open for further species that might yield even more useful drugs. Eventually another was found in, of all places, a golf course in northern Victoria and it was from this that moxidectin was isolated.

ivermectin and moxidectin work by stimulating the release of an enzyme called GABA.

GABA is a neurotransmission inhibitor. This means that it interferes with the normal transmission of a nervous impulse along a nerve.

In roundworms and hairworms, ivermectin does this at the junction between the central (i.e. spine) and peripheral nerves, while in insects it exerts this effect at what is called the neuromuscular junction (i.e. the gap between the end of the peripheral nerves and the muscles). The result is that the parasite is paralyzed and dies.

Moxidectin also acts at these two sites but at two further sites as well. Both drugs are metabolized by the liver, but moxidectin to a lesser extent, making it safer to use in birds with underlying liver problems such as Chlamydia, Salmonella or Herpes virus.

When moxidectin and ivermectin are compared, moxidectin is more potent and is also more soluble in fat (i.e. lipophilic), which means that it is more persistent in the body, exerting its effect for longer. It is because of these reasons that moxidectin is often preferred over ivermectin.

Although older wormers have their use at times, each has problems:

These include
Piperazine, (drug resistance, decreased worm clearance),
Fenbendazole (Panacur) (causes fret marks on feathers if used during moulting)
Levamisole (vomiting and worm resistance).

Moxidectin has none of these side effects.