Abamectin ? Cancerous Properties
Abamectin differs from ivermectin by a single double bond at the C22-23 position.   Abamectin is a pesticide with many different agricultural uses.  It has been tested in acute, subacute*, and geno toxicity assays similar to those for ivermectin with similar results, except that abamectin is slightly more toxic than ivermectin. Neither compound is geno toxic.
Abamectin was recorded in toxicology studies as not being carcinogenic (cancerous) in rats when given in the diet at varying doses.
Abamectin was recorded in toxicology studies as not being carcinogenic (cancerous) in mice when given in the diet at varying doses.
A lot of the parasites listed either do no occur in Australia or only occur only in wild rodents.  The main nematode in Australia is the Aspiculuris and possibly Syphacia and Hymenolepis.  I would also have liked to record the actual doses mentioned in trials to treat the parasites but there is some question as to their accuracy, i.e. the ug/mg as opposed to the mg/k rate so I will list the parasite but the findings will be without dose rates used, until such time as it is clarified. Editor
Mice
1.     Endoparasites
tetraptera- Ivermectin added to drinking water for 24 hours only. Hasslinger and Wiethe 1987.
Syphacia obvelata ? Ostlind, Nartowicz, and Mickle (1985) reported that feeding a diet containing ivermectin for 6 days to mice naturally infested with pinworms was more than 99% effective against both adult and immature worms. Other dose rates recorded varying effectiveness.
Nematospiroides dubius ? oral treatment on days 3 or 6 post infection was reported to remove all worms present Sayles and Jacobson 1983; Rajasekariah and colleagues (1986) reported that a much lower dose than that of Sayles and Jacobson completely eliminated adult worms from mice.
Strongyloides spp ? Grove 1983 reported that a single dose 6 days after infection eradicated intestinal adult worms.  Others gave other smaller more regular doses like Rajasekariah and colleagues and Grove (1983) also with good results.
A Toxocara canis- treating mouse with Ivermectin does not completely eradicate the larvae.  It alters the distribution of the larvae:  The larvae are retained in the liver and lungs and fewer migrate to the brain. None of the dose rates completely eradicate the parasite from the tissues.  Doses of Ivermectin for 2 to 7 days after infection and smaller doses on days 15 to 28 after infection
Trichinella spp ? Treating the mice with avermectin reduced the number of intestinal T. spiralis 80% to 90%Campbell, Blair, and Lotti 1979).  The number of parasites was not reduced significantly, However, it was effective against intestinal forms of T. nelsoni and T. nativa in this study reducing their number by 91% to 96%(relative to controls), following other treatments on Days 1 and 6 post infection.
Trichuris muris ? after repeated doses of ivermectin, mice treated for T. muris infestation were not completely cured Rajasekariahet al.1986.
2.  Microfilariae
Ivermectin?s microfilaricidal activity has been demonstrated against immature stages of a number of filarial parasites in mice.
Single low doses of ivermectin destroyed 100% of Onchocerca lienalis microfilariae within 5 days after treatment.  The same dose, administered at various times prior to microfilariae infection, reduced parasite recoveries by 92% for infection 4 days after treatment (Bianco et al 1986)
Devaney and Howells (1984) reported that Bugia pahangi microfilaremia was reduced by 87% 24 hours after treatment of mice orally; the peritoneal microfilariae of this species were unaffected.  O.lienalis larvae in the cutaneous and subcutaneous tissues, and Dirofilaria immitis microfilariae in the blood of mice were also killed at this dose.
Zahner and colleagues (1987) reported that subcutaneous treatment of dipetalonema viteae-infected Mastomys natalensis with ivermectin once or less on 5 consecutive days reduced microfilaremia 100% over a 42-day trial period.  Higher doses were required to remove microfilariae of Litomosoides carinii.  Lower doses removed circulating microfilariae of both species for shorter period of time.  Activity against adult D.viteae was demonstrated following 5 consecutive daily treatments at a lower dose, then higher doses of ivermectin and this did not affect the numbers of adult L. carinni at these dose rates.
3.    Ectoparasites
The efficacy of ivermectin has been evaluated against some parasitic arthropod species in the mouse.
a.   Mites
Silverman, Blatt, and Lerro (1983) reported that feeding mice a commercial diet containing ivermectin/kg of feed for two 6-day periods, 1 week apart, effectively eliminated Myobia musculi mites.  Efficacy of the product against murine mites, was confirmed by Wing, Courtney, and Young (1985), who demonstrated that 2 subcutaneous injections, given 1 week apart, effectively eliminated Mycoptes musculinus and Myobia musculi from laboratory mice.  Single treatments reduced infections only temporarily.  Rad fordia Afinis are not mentioned in this study.  Often, the only indications of pinworms in the mouse are a prolapsed rectum from straining.)  Baumanset al. (1988) reported that spraying mice with a .01% solution of ivermectin was effective in eliminating symptoms of mite infection for 12 weeks after treatment.
b. Triatomid bugs. Treating mice with ivermectin at 0.2 mg/kg was reported to have caused high mortality and a reduction in egg-laying potential of Rhodnius prolixus and Hemiptera triatominae feeding on these animals (Azambuja et al. 1985).
c.   Cuterebra fontinella.  The C. fontinella mouse model was used to demonstrate the systematic insecticidal efficacy of the avermectins.  Ostlind, Cifelli, and Lang (1979) reported an avermectin mixture to be effective.  Drummond (1980) subsequently confirmed this activity using ivermectin in mice with induced C. fontinella infections.
Rats
Rats have been used as a model system to assess ivermectin?s basic toxicology, as well as for extensive studies on the drug?s mode of action, pharmacology, and pharmacokinetics (Calcott and Fatig 1984; chiu et al. 1986; Olsen and Snowman 1985; Pong and Wang 1980; Pong, Wang, and Fritz 1980; Williams and Yarbrough 1979).
Antiparasitic evaluation has been limited to a few endoparasites ? rat models, although efficacy has been demonstrated against natural pinworm infestations.
a.   Syphacia muris.  Treatment of rats with ivermectin for 5 consecutive days was 99% effective against natural infections of this parasite (Battles et al. 1987).  There was no difference in body weight between treated and control animals, and no toxic signs were observed after treatment.
b.  Angiostrongylus cantonensis. Although treatment of 6-week-old infections of A. cantonensis resulted in a lower fecal egg and larval count in rats (indicating an effect on the fecundityfertility of the parasite), ivermectin did not have a demonstrable vermicidal effect at this level.  Oral treatment at a higher dose 3 days after induced infection did result in a significant reduction in the number of worms recovered (Ishii et al. 1983).
c.  Hymenolepis (the dwarf tapeworm) common in Australia is not mentioned in this study.
d.  Trichinella spiralis
Although treatment was only 84% effective against migrating larvae and 83% effective against encysted worms, increasing the dose rate was reported to increase efficacy to 94% and 99% respectively, against these 2 stages of T. spiralis (Rapic, Dzakula, and Matic-Piantanida effective against intestinal T. spiralis (Alcaino, Gorman, and Imbert 1984)
e.   Syphacia muris
Treatment of rats with ivermectin for 5 consecutive days was 99% effective against natural infections of this parasite (Battles et al. 1987).  There was no difference in body weight between treated and control animals, and no toxic signs were observed after treatment.
Ectoparasites in Rats
Mites
a.     Radfordiaensiferia (fur mites) are not tested in this study.
*subacute ? describes a disease that progresses more rapidly than a chronic condition but does not become acute.
LIST OF REGISTRATIONS
Ivermectin was released for registration by Merck & Co., Inc., in 1981 and first registered in France as IVOMEC injection for Cattle that same year.
Since that time ivermectin has been approved for use in over 60 countries.  It is currently registered for use in cattle, sheep, horses, goats, swine, dogs, camels, reindeer, and bison.
The following lists the products and the countries in which ivermectin is registered.
IVERMECTIN APPROVAL
IVOMEC* Injection for Cattle
AVOMEC
* Trademark of Merck & Co. Inc. Rahway, New Jersey U.S.A.
Information was taken from the book, Ivermectin and Abamectin by William C. Campbell Editor - ISBN 0-387-96944-6 Springer-verlag Publishers. Data saftey sheets for the various products, Tom Donelly, University of Sydney, 2003 IVS No. 1033-2863 and i would like to thank Peter K Ward, Vibrac (Australia) P/L and Dr. Ian Beveridge BVSc PhDDVSc Melbourne Veterinarian Science University for their time and expertise in putting together this paper
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