Chemical alternatives to treatment of cattle with Ivermectin
McCracken, D & Bignal, E
An information sheet describing alternative methods of anti-parasite treatment for cattle.
Ivermectin is a broad spectrum antiparasitic drug introduced onto the international animal health market in 1981. In Britain it is approved for the use in cattle, sheep, goats, pigs and horses. The drug is absorbed systemically after administration and is excreted mainly in the faeces. Being insecticidal, residues of ivermectin in cow dung can reduce the number and variety of insects in the dung beetles, residues of the drug have been shown to adversely affect certain types of fly larvae, appearing to inhibit larval development and/or prevent pupation from taking place.

Fears have been expressed that this reduction in the fauna could have an adverse effect on the wildlife, particularly birds, reliant on cow dung as an important invertebrate food source. Such a reduction also has the potential to delay dung degradation, leading to fouling of pastures. In addition, there is concern over the effects that long-term ivermectin usage in any area may be having on the populations of insects associated with cow dung within that area. The purpose of this information note is to provide a summary of the currently available chemicals for treatment of cattle against internal nematode parasites and certain arthropod ectoparasites, that are more 'environmentally sensitive' than ivermectin (Ivomex as an injection or pour-on formulation).



The figure below shows the major chemical groupings available for anthelmintic treatment of stock, and the spectrum of activity of each. No adverse effects on the invertebrate fauna of cow dung have been reported after treatment of cattle with chemicals from the first three of these groupings, and therefore they provide viable alternatives to ivermectin.
Most of the anthelminitics currently available belong to a group of chemicals commonly referred to as benzimidazoles. These are highly effective against most of the gastrointestinal nematodes of cattle, and the ranges of activity of the more recently introduced benzimidazoles include lungworms, tapeworms and liver fluke. These chemicals have, with one exception, to be given by mouth and they are marketed in a range of drench and paste preparations. Oxfendazole is also available for intra-ruminal injection or incorporated into one of two pulse-release devices ('Autoworm' or 'Synanthic Multiclose') which are normally administered at the start of the grazing season. A does of oxfendazole is released from the devices at regular intervals throughout the grazing season, up to a maximum of 5 or 6 times, giving them active lives of up to 130 days.
Levamisole is highly effective against a range of gastointestinal nematodes and lungworms parasitising cattle. While it is normally given by mouth or subcutaneous injection, pour-on preparations are also marketed for use in cattle. Levamisole preparations should not be given simultaneously with organophosphorous preparations, or for a period of 14 days before or after treatment.
Morantel tartrate is highly effective against adult and developing immature gastrointestinal nematodes, and is currently marketed as a slow-release device in cattle ('Paratext Flex Bolus') which remains active for about 90 days. Morantel has no activity against lungworms, and therefore a lungworm vaccination programme should be used in conjunction with this chemical.


spectrum of activity of anthelmintic groups


Ivermectin is also approved for use against certain ectoparasites of cattle (eg sucking lice, warble fly), and so alternative control methods for these pests need to be implemented if ivermectin usage is discontinued. Two main chemical groupings are used as the basis for the commonly used ectoparasitivides, namely the organophosphates and the synthetic pyrethroids.
These chemicals can persist in the animals coat for a reasonable period, but residues in animal tissues are short-lived. Some organophosphates, eg coumaphos, are formulated as powders for use against lice and fleas, while others, eg chlorphyrifos, are used as sprays for tick control. Some have the ability to act systemically, given orally or as a pour-on, and can be used for the control of warble fly larvae, lice and the mites causing sarcoptic and chorioptic mange of cattle. These chemicals can be dangerous for the operator to use, therefore, protective clothing should be worn when applying them.
It should be noted that residues of the organophosphate dichlorvois in horse dung (from animals treated with the drug to control internal nematode and arthropod parasites) can have an adverse effect on the beetle fauna of the dung, and therefore the use of systemic members of this grouping should be considered carefully. In addition, magpies have died after feeding on the backs of cattle treated with organophosphate warblicides.
Synthetic pyrethroids
These persist well on the coat or skin, but not in tissue, and so are of particular value against parasites which feed on the skin surface, eg. Lice, ticks on sheep, some mites and nuisance flies. They have a low mammalian toxicity, but they are very poisonous to fish and crustaceans (and so containers should be disposed of with care). Synthetic pyrethroids can be applied to cattle as sprays for fly and lice control; impregnated in ear tags for fly control; or in a pour-on formulation for the control of flies, lice and ticks.


Whichever chemical and method of application is selected, it is important to read the manufacturers instructions, with particular regard to the types of pest against which the product is active, the class of stock for which it is recommended and any limitations to use, the dose rate, and the withholding period. In addition, it is advisable to consult a veterinary surgeon to develop a control strategy designed for the farm which preferably does not rely too heavily on chemical treatment of the stock.
It should also be borne in mind that the use of alternative chemicals may result in an increase in antiparasitic treatment costs, and may also necessarily involve more handling of the animals throughout the year.
Finally, a note of caution – resistance of certain nematodes to anthelmintics have been reported in sheep, and therefore, although such resistance has not yet been reported in cattle, it might be prudent to select a different drug from each anthelmintic grouping on an annual basis to utilize their different modes of action and thus minimize the development of resistance.
Wall, R. & Strong, L. 1987. Environmental consequences of treating cattle with the anti-parasitic drug ivermectin. Nature 327: 418-421.
Jackson, H.C. 1989. Ivermectin as a systemic insecticide. Parsitology Today 5: 146-156.
Ridsdill-Smith, T.J. 1988. Survival and reproduction of Musca vetustissima Walker (Dipteral Muscidae) and a scarabaeine dung beetle in dung of cattle treated with ivermectin B. Journal of the Australian Entomological Society 27: 175-178.
Wardhaugh, K.G. & Rodriguez Menendez, H. 1988. The effects of the antiparasitic drug, ivermectin, on the development and survival of the dung-breeding fly, Urthelia comicina (F) and the scarabaeine dung beetles, Copris hispanus L., Bubas bubalus (Oliver) and Onitis belial F. Journal of Applied Entomology 106: 381-389.
Madsen, M., Nielsen, B.O., Holter, P., Paderson, O.C., Jepensen, J.B., vagn Jenson, K.M., Neerson, P, & Granvold, J. 1990. Treating cattle with Ivermectin and effects on the fauna and decomposition of dung pats. Journal of Applied Ecology 27: 1-15.
Campbell, W.C. 1989 (ed.). Ivermectin and Abamectin. Springer, New York.
The authors thank Dr G. B. B. Mitchell, Senior Veterinary Investigation Officer with the Scottish Agricultural College for his helpcul comments on this information note.
Dr David McCracken & Dr Eric Bignal
2 pages A4
Please cite as: McCracken, D & Bignal, E, (1991), Chemical alternatives to treatment of cattle with Ivermectin, 2 pages A4