ABAMECTIN,IVERMECTIN
Many breeders treat their rats and mice for mites, lice, and worms have used this group of chemicals.  Perhaps this will clarify the many misconceptions about this and other similar products.
In the following, the expression of dosage in terms of micrograms (ug) per kilogram of body weight has become commonplace in accounts of the efficacy of these compounds, and this form has been widely used in the book I took a lot of this text from. 
Toxicological studies, however, usually deal with multiples of milligrams, rather than fractions, in that context, dosages are expressed in terms of milligrams (mg) per kilogram of body weight. (In short, for those of you who do not understand the terminology - 2ug is lower than 2mg or in other words, less toxic than the mg).
Having said that, it appears that the text (in particular, the dosages) in some of the papers I used to research this product/compound is in question, and due to my time being limited to research this properly, I have been unable to quote much of what has been mentioned because it may be wrong due to the misuse of the ug as opposed to the mg.  This highlights just how important it is not to believe everything you read without proper research.
Source of Streptomyces avermitilis and Discovery of the Avermectins ? The microorganism that produces the avermectins was isolated from a soil sample collected near a golf course at Kawana, ItoCity, Shizuoka Prefecture, Japan.  Research scientists at the Kitasato Institute in Tokyo under the director of Dr. Satoshi Omura, isolated this culture.
Ivermectin was introduced to the marketplace as an antiparasitic drug in 1981 and abamectin was introduced as an agricultural pesticide (and as an antiparastic drug) in 1985. They are both members of the avermectin family of compounds.  Abamectin was found to be unstable when using it to treat parasites in animals and the pharmaceutical companies were unable to get standardisation of the compound in its present form so other synthetic products has been manufactured which are more suitable for use in animals.  Some examples of this are Ivomec and Abamectin, Selamectin, Doramectin and Moxidectin.  For example, Selamectin was manufactured because the Collie dog, in particular, had a toxic reaction to other ??mectin? products.  Selamectin itself is not manufactured in large quantities and the price reflects this.  The avermectin family is considered to be extremely safe for animals, plant life and humans to come into contact with. The related family to avermectins is the milbemycins.
The Halo Effect and Skin Absorption:
 One such relation, Selamectin (used in Revolution ? the cat and dog flea treatment) creates a halo effect around the animal being treated and it will provide some coverage for the offspring.  This is because some of the selemectin is absorbed through the skin to the into the milk supply and also, as the mother sits on them, she is also coming into contact with the babies and any residue of the product on that skin is transferred to the babies.
In theory you would think all would be easily treated in this way but it becomes necessary to re-treat some mice/rats later on. Often, there is a proportion of young ?buried? within the group who do not get enough exposure to the product.  When the fur grows, around 10 days, those animals need re-treating.
The Liquid Ivermectin/Ivomec is not to be considered to be embryo toxic (i.e. toxic to unborn babies).   For those of you who are still sceptical, it is also suggested that ivermectin is poorly absorbed percutaneously (through the skin) and this was confirmed in Monkeys tested so the spray is quite safe.   So too is the oral (by mouth) method but generally, you would increase the dose in topical (on the skin) formulations, so comparing toxicities between the oral and spray methods is sometimes difficult to gauge. 
Overdose
These are some of the symptoms of acute toxicity ? OVERDOSE:
In mice: uncoordinated movement, abnormally slow respiration rate and tremors.  If you have overdosed your animal, these symptoms will appear within 1 hour of treatment and most deaths occur within 24 hours.
In rats: uncoordinated movement, drooping upper eyelids, decreased activity and death is generally preceded by loss of righting.  Death can occur within 12-48 hours.
Dosages/Product Strengths/Reactions
It is often confusing trying to understand the measurements used in the application of liquids and pastes.  It is not practical to use teaspoon measures here because of their inaccuracy when dealing with weight but anyone can get a 1ml syringe (or in the case of Equimec, a 5 ml syringe as well) from the local chemist or possibly your doctor or vet although you may get a questioning look from them as to why you want it.  Just explain why you require it and ask for one without the needle attached.   The 1-ml is divided into 100 divisions, so it should be easy to measure out 0.12ml.  The only other thing you need to know is that 1000mm = 1 ml, or 100mm = 0.1ml. Dose rates are worked out on the basis of the dose required to kill at least 99% of the parasites.  This dose, the therapeutic dose ug is usually significantly lower than the dose at which signs of toxicity appear.  For example in horses and sheep you have to give 10 or 20 times the recommended dose before toxic signs appear.
Here are some of the methods of application in as simple a language as possible:
Selamectin (Revolution) - This product is used for treating cats and dogs for fleas.  It is alcohol based and some rats/mice may get a reaction to this, the alcohol, not the selamectin.  The alcohol can make the red skin and itchy.   You would apply selamectin at the rate of ?a smear or pinheads drop? on the back of the neck and it must be in contact with the skin to work.  The tubes are sold with a puncture tool attached in the cap, but this is allows too large liquid to flow out and it would be better to use a fine needle.  Because alcohol evaporates, it is important to reinsert the needle after use to close the hole.
Liquid Ivermectin  (also known as Ivomec/Avomec) - check weight and dose accordingly.  It is not recommended that you use the Ivomec sheep or cattle drenches unless you have some knowledge of how to calculate weight measurements.  The quote from the book ?You would have to use extremely excessive amounts before damage was done using Ivermectin? (I believe that is in the case of large animals such as cattle/sheep so use extreme caution when applying to small animals Editor).
 In the case of Ivomec for sheep and cattle, the dose rate is the same (200mg/kg) but the formulations are quite different.  Ivomec for sheep is a drench and contains 0.8g/litre of Ivermectin.  Ivomec for cattle is an injectable product and contains 10g/litre.
The liquid Ivermectin/Ivomec can be used as a spray.  Diluted, it can be sprayed directly onto the animal.  It should be made up of 1 part of Ivermectin to 100 parts of water, i.e. 1:100.   That is, in the case of rats and mice, 1ml to 100 ml water.  
Also, 1 ml Ivomec liquid can be used in 1 litre of water and can be put in the water bottle.  But, this method is not always guaranteed as it is unlikely that all the mice/rats would be getting equal quantities of the oral dose i.e. each animal drinks different quantities according to weather, pregnancy, general health, etc. but nonetheless, it is an option.
In Australia, there is only one type of lice that can affect your rats and mice, the sucking type belonging to the genera Polyplax and Hoplopleura, a photo of which can be found in a book by D. Bowman called ?Georgi?s Parasitology or Veterinarians?. They can be controlled by oral ivermectin and spray on treatments of ivermectin.  The length of treatment depends and this can differ by days.  The spray solution of 0.01% should last for 12 weeks (every three months) before reapplication is needed.  With the sprays, they are very safe but they still should not be used on a continual basis, weekly or daily over a long period of time.  Rats and Mice are similar to humans in that they do suffer from the occasional allergic reactions.  Once again, you should check your animals? surroundings and bedding materials and eliminate the parasite from those areas.
Equimec, Equimax, Equimax LV ? Horse worming Products
Other products many people have used to treat mites and lice are horse-worming treatments in the form of Equimec, which contains 18.7mg of Ivermectin, and Equimax, which has Abamectin 3.7mg, and contain 46.2mg Praziquantel.  Praziquantel is the worming ingredient and can be used to kill tapeworm in rats and mice.  Equimax LV contains 18.7 mg Ivermectin and 140 mg Praziquantel.  For all registered horse products, all the information you need is in the 2003 IVS Annual.  The Liquid Equimec has 10g/litre of Ivermectin.
Another product often used as a vehicle carrier in these horse worming products is a waxy substance that makes the paste adhere to whatever it is put on or given to.  There can be side effects from skin contact with this product, and in tests, the side effect in humans was skin irritation but the risk of that happening was minute. When tested on cats (mouse/rat statistics were not available), there was some hair loss recorded but that was less than 1%.
Equimax LV Oral Paste for Horses has been tested on Rats as an IV solution and its half live (longevity/viability/working ability/staying power) was calculated at 1 day.  90% of the administered dose is excreted in the faeces with less than 1% appearing in the urine and less than 2% in the breast milk and this is regardless of whether Ivermectin is administered parentally or orally.
Equimec (the horse worming paste) commonly used by Breeders in the past has not been tested as to its accuracy and in fact there is not even any record of whether this dose is even beneficial at that rate.  However, no harm has ever come from using this method and that is administered directly to the mouth as ?a half grain size of rice size of paste? (use a toothpick for a scoop measure) and for a rat, the size of a grain of rice. The animals find it quite palatable and it is unlikely that you would have to hide it in anything.   Do not use on foodstuffs if you have more than one mouse or rat as one animal may get more than the others and an overdose may occur (so it is said!).
Using the horse paste may be too difficult to measure out, but using Equimec liquid, you could measure out the dose using a 1-ml. syringe.  The dose is 1ml/50kg so the best way to do that would be to draw up 1-ml. into a 5 ml. syringe, then draw up 4 ml of distilled water so you have a mixture that would have to be administered at 1-ml./kg.  Then, you could weigh the rat on kitchen scales and easily calculate and administer the dose.  For example, a rat weighing 350 gm would need a dose of 0.35 ml.
Find the mass of the container including the lid, (if you use one) without the mouse
Put the mouse into thje container and measure the total mass
Abamectin/Ivermectin is photosensitive.  It can lose its volatility if exposed to air and sunlight.  It degrades rapidly and has a half life of 4-6 hours particularly in sunlight, so it is important to always keep it tightly capped and do not leave the lid off for long periods of time.
Note:  It is not wise to use other products than those mentioned especially if they contain organophosphates which to lead to more ingestion into the body through the skin and this in turn can have a detrimental effect over a period of time.
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