AU2009100045A4 - Prevention of blowfly strike of sheep - Google Patents

Description

Description AUSTRALIAN INNOVATION PATENT SPECIFICATION PREVENTION OF BLOWFLY STRIKE OF SHEEP PJM SCIENTIFIC PTY LTD FIELD OF THE INVENTION This innovation relates to stable veterinary formulations containing insecticidal compounds suitable for sustained internal application to sheep wherein the compounds are excreted via the animal's urine and/or faeces. In the process of excretion, traces of the compounds or their metabolites, which have insecticidal properties, are deposited onto the fleece or skin of the sheep thereby reducing or preventing invasion by flies leading to myiasis.

BACKGROUND OF THE INVENTION Flystrike is a common disease of sheep in which flies lay their eggs on the surface of sheep and the developing maggots use the sheep as a food resource. The result is myiasis, an infestation of the body of the sheep with the larvae of flies. Contamination of the wool with faeces or urine forms an attractant to flies and predisposes the sheep to flystrike.

Many compounds are currently used to prevent flystrike on sheep and consequently, myiasis. These compounds belong to the endectocide and insecticide classes of chemicals and are generally applied topically to sheep. These compounds are chemical toxins or insect growth regulators (IGR) which, either kill the eggs or larvae of the blowfly or prevent their development from the egg or through the larval stages.

The presence of insecticidal chemicals reduce the likelihood or prevent the blowfly using the sheep as a food resource and consequently avoid myiasis and the associated suffering and possible death of the sheep. Even in the absence of death, myiasis Oresults in reduced commercial value of the animal and wool. Many of these 0 O compounds are suitable for delivery to the animal orally and they are then metabolised in the animal and the compounds or their metabolites excreted via the animal's urine and/or faeces.

Over many years, sheep have been protected from flystrike by a surgical procedure t'4 referred to as 'mulesing'. This process involves the removal of the skin around the Obreech region of the unanaesethised sheep with shears resulting in scarring and Otightening of the skin without the regrowth of wool. This procedure is painful to Osheep and is at odds with current animal welfare considerations and good sheep 0husbandry. The present innovation will provide a suitable alternative to this painful and archaic process.

While mulesing provides protection once the healing and scarring occurs, there is a period of vulnerability to flystrike during this healing process (Cook and Steiner 1990. Australian Veterinary Journal 10:352-5). Animals are also vulnerable to further injury and infection during this period. Mulesing only provides protection from flystrike to the breech area and it is known that the belly region around the pizzle of male animals which becomes contaminated with urine is a predilection site for flystrike.

In the absence of mulesing or to protect sheep from myiasis in regions other than the breech, sheep are sprayed, 'dipped' or 'jetted' using a dilute solution of insecticide.

This provides some respite from the threat of flystrike but requires several applications at high doses of pesticide during a fly season to provide continuous protection.

OBJECT OF THE INVENTION It is an object of this innovation to provide stable veterinary formulations of a chemical or combination of chemicals to provide a sustained period of protection to sheep from blowfly strike, thereby preventing surgical intervention (mulesing) and avoiding large deposits of chemical in the wool through dipping, spraying or jetting chemicals to the fleece of sheep.

1 STATEMENT OF INVENTION 0 O The present innovation provides stable veterinary formulations suitable for sustained internal administration to sheep and combines the knowledge of formulation of chemicals with an understanding of their metabolism and insecticidal properties O which prevent flystrike. The innovation provides sustained delivery, over 60 days or longer, to ensure a controlled release into the animal's gastrointestinal system, Th subcutaneous region or other suitable internal region. In the process of metabolism Oand excretion, the chemicals with insecticidal properties are removed from the body Oof the sheep with the urine or faeces. When small quantities of this excrement remain O attached to the skin or wool, the insecticide is also retained. This insecticide provides a level of protection from flystrike. The device provides protection during a period of a 'fly wave' which occur on a seasonal basis when climatic conditions are suitable for the development and breeding of myiasis producing flies.

The present innovation protects sheep for 30 or more days with the application of a single controlled release dose and may extend for up to 1 year. The amount of the formulated active ingredients or their metabolites is self-administered in small amounts via the excrement thereby minimising any problem of pesticide residue contamination in the wool of sheep.

In one aspect of the innovation, chemicals formulated in a controlled release device and excreted in the faeces with insecticidal properties include members of the macrocyclic lactone class (ML or endectocides) for example, ivermectin, avermectin, abamectin, milbamycin, selemectin, moxidectin, doramectin, nemadectin and the like.

Members of the benzyl urea class such as diflubenzuron, triflumuron, methoprene, pyriproxyfen or the triazine, cyromazine which are excreted either in faeces or urine are also suitable either alone or in combination with each other or the ML compounds would form another aspect of the innovation.

Preferably, the use of compounds that are currently registered for application to sheep and used in animal parasite control and management would provide advantages to the regulatory and compliance process. Ivermectin, abamectin, doramectin, moxidectin, cyromazine, triflumuron, diflubenzuron and spinosad are suitable examples.

The ML class are particularly suitable for formulation in controlled release devices being presently used to control internal parasites (worms) and some external parasites and have activity at low dose rates. They are known to be excreted in faeces and one member of this class has been shown to protect sheep from breech strike (Rugg, Thompson, Gogolewski, Allerton, Barrick and Eagleson 1998. Australian Veterinary Journal 76:350-4). Similarly, cyromazine has been used, in an experimental context, in a controlled release device for protection of sheep from myiasis (Anderson, McKenzie, Laby, Strong and Jarrett 1989. Research in Veterinary Science 46:131-8).

The controlled release device used in these experiments was first described in Australian Patent Application Number 35908/78 and reported to be successful as a mechanism of delivery of anthelmintics for control of gastrointestinal worms (Anderson, Laby, Pritchard and Hennessy 1980. Research in Veterinary Science 29:333-31).

The benzyl urea, triazine and spinosad classes of chemicals or insect growth regulators are also particularly suitable being presently used as topical chemicals for protecting sheep from blowfly strike and other external parasites such as sheep lice.

Cyromazine and triflumuron have also been administered in food to chickens to prevent the development of flies and other insects in the dung (litter) (Vesirianzadeh, Jervis and Kidd 2007. Iranian Journal of Arthropod-Borne Diseases 1:7-13). In these examples, the compounds, which are formulated as granules or powders were administered on a daily basis with the feed. The compounds remain in the faeces which form the litter and the resource used by the flies. In a similar manner, diflubenzuron has been formulated into a bolus and administered to cattle to control horn fly in the dung after it has been deposited on the pasture.

In the normal course of sheep grazing some excrement remains on the sheep and provides a site of attraction for blowflies, leading to myiasis. Administration of the present innovation, leads to insecticidal residue in the faeces or urine reducing or preventing the fly pest from exploiting the sheep as a food resource thereby preventing myiasis. The trace amounts of the compound in the excrement become deposited onto the skin or fleece, with any excrement contamination, and thereby reduce attractiveness to flies and prevent the damage from the developing stages of these blowflies.

Because sheep are grazing animals, there is no opportunity to provide a daily feed product. The delivery dose and total quantity of chemical to be delivered is obtained empirically. A balance exists between the total dose, the rate of delivery and the potential delivery time. The overall effectiveness of the innovation, is increased by the formulation containing agents to protect the active ingredient from degradation from environmental conditions such as ultraviolet light. Further enhancements and improved efficacy come from binders and stabilisers in the stable veterinary formulation.

The controlled release device can be in the form of a capsule as exemplified in Australian Patent Number 35908/78, or suitably formulated into an implant, a tablet, a solid, a semi-solid or a depot-liquid.

Claims (6)

1. Stable veterinary formulations for administration in a controlled release Otechnology suitable for internal application to sheep wherein the stable formulations comprises one or more compound with insecticidal properties and the compounds or '4 their metabolites are excreted via the urine and/or faeces wherein their residual presence on the skin or fleece protect sheep from myiasis.

2. The veterinary compounds as described in Claim 1 wherein these Ocompounds include members from the endectocide, benzyl urea or spinosad classes of ochemicals for example avermectin, abamectin, ivermectin, doramectin, moxidectin, nemadectin, selemectin, milbamycin, cyromazine, diflubenzuron, triflumuron, methoprene, pyriproxyfen, spinosad or the like.

3. The controlled release device as described in Claims 1 2 wherein the formulation are contained in a delivery technology such as an intra-ruminal capsule, an implant, a tablet, a solid, a semi-solid or depot liquid administered into the gastrointestinal tract, subcutaneous tissue or other suitable internal region of the animal.

4. Stable veterinary formulations as described in Claims 1 3 wherein the formulations may contain agents such as UV protectants, stabilisers or binders to protect the residual compounds or metabolites from ultra-violet light, to improve chemical stability or to enhance adhesion to the skin or fleece of the sheep.

Stable veterinary formulations as described in Claims 1 4 wherein the delivery dose rate is controlled to result in residual concentrations which protect sheep from myiasis.

6. Stable veterinary formulations as described in Claims 1 5 wherein the delivery would be sustained over a period of time sufficiently long to provide practical benefits to farmers being more than 30 days but preferably 60 90 days and may extend for up to 1 year.