AU2016202546A1 - Ectoparasitic treatment method and composition - Google Patents

Abstract

A method of treating an animal preferably a sheep infested with biting lice characterised by the step of administering internally to the animal a pharmaceutically effective amount of spinosyn such that the spinosyn is present systemically within the animal.

Description

ECTOPARASITIC TREATMENT METHOD AND COMPOSITION TECHNICAL FIELD This invention relates to an ectoparasitic treatment method and composition. 5 In particular, the present invention relates to the treatment of biting lice on sheep, although it should be appreciated that aspects of the present invention can be extended to related matters. BACKGROUND ART Ectoparasites are a significant animal health concern as well as significantly affecting 0 production and increasing labour and capital costs. In general, there are many ways to treat ectoparasites, but it is a continual battle to find new and more effective treatments. Referring now to a specific problem the inventors seek to address, lice and blowflies are the two most significant external parasite problems experienced by sheep in Australia. Both 5 parasite groups cause extensive production losses and serious animal welfare concerns. Of these two ectoparasite groups only the lice are obligate and permanent sheep parasites. That is, they are dependent on spending their entire life cycle on sheep. The most prevalent and most important of the sheep lice is the biting louse, Bovicola (formerly Damalinia) ovis. Lice are typically categorised into those that feed directly on the blood of the host, i.e. sucking .0 lice, and those that feed on the skin surface (e.g. on secretions and skin debris), i.e. biting (or chewing) lice. Three species of sucking louse are known to occur on sheep but are rarely identified or implicated in production losses or disease in Australia. These are Linognathus ovillus (the face louse) and Linognathus pedalis (the foot louse) and Linognathus africanus (O'Callaghan et al., 1989). 25 In Australia, lice have been estimated to cost the wool industry more than $120 million per year.' Such costs include expenditure on treatment and control of infestations as well as production losses. Significant reductions in fleece value (e.g. up to 30%), greasy fleece weight and clean fleece weight have all been demonstrated in lice-infested flocks (Wilkinson et al., 1982; Niven & Pritchard, 1985; Elliott et al., 1986; Cleland et al., 1989). Lice infestation has also 30 been shown to detrimentally affect the colour of the fleece, i.e. making it less bright and more yellow (Kettle and Lukies, 1982), and can result in the downgrading of skins due to 'cockle' (Heath, 1995a). 1 The impacts on animal welfare and production due to sheep lice (i.e. B. ovis) are a consequence of the irritation experienced by infested sheep. Primarily, the sheep show signs of pruritus (itchiness) such as rubbing, biting and scratching and these behaviours damage the integrity of the fleece (e.g. causing 'pulled' or cotted wool). In some sheep the pruritus can be '5 intense and the irritation can manifest as changes to the skin, including increased scurf and thickening of the epidermis and overlying lipid layer (Britt et al. 1986; Heath et al. 1995b). There is variation between individual sheep susceptibility to lice and this may be linked to an immune response to infestation (James 1999; James et al. 2002). B. ovis are recognised as feeding on "skin scurf, lipids, loose stratum corneum squares and 0 bacteria" (James, Moon & Brown, 1998). Although most lice (particularly adults) have been observed in the fleece, away from the skin surface, they are quite mobile and are likely to feed on substrates other than just the loose debris present at that location (Sinclair, Butler & Picton, 1989). The feeding behaviour of B. ovis at skin level appears to occur only on the surface of the epidermis and does not bring it into direct contact with the internal tissues or blood of the host. 5 Observations have determined that B. ovis "does not ingest nucleated keratinocytes and apparently does not penetrate deeper than the outer layers of the stratum corneum" (James, Moon & Brown, 1998). Lice are transmitted between sheep via direct contact. Lice control relies upon effective chemical treatment of an entire flock and subsequent biosecurity measures to prevent re .0 infestation (i.e. exclusion of lice-infested sheep). Due to the surface-feeding habits of B. ovis, all successful chemical treatments previously used have involved topical delivery of the lousicidal chemical. The methods used can be broadly categorised into high-volume application of diluted chemical (i.e. in water) or low-volume delivery of concentrated chemical formulations. High-volume application methods used in the past have included plunge dips, shower dips, 25 jetting races and hand jetting. These methods require prolonged wetting of the animal or high pressure jets to ensure adequate penetration or saturation of the fleece with the chemical solution (Rothwell, 2005). Although they have often proven to be very reliable some disadvantages of these methods of application include the capital expenditure on equipment, additional labour required, exposure of operators to chemical (Anon., 2006), stress to animals, 30 secondary disease problems (e.g. transmission of infections), in-use maintenance of adequate chemical concentrations (Levot, 1995) and the safe disposal of left-over chemical solution (Levot, Lund & Black, 2004; Beynon, 2012). Low-volume application methods have become very popular due to their convenience and include pour-on and spray-on formulations. These products are generally ready-to-use and the 35 operator applies them to individual sheep using a manual or gas-powered applicator. There is inevitably a high concentration of chemical at the sites of application but its subsequent h~ttp://www,woolom/Grow UceBoss.htm Accessed on: 3 May 2012. 2 distribution through the fleece and over the skin is uneven. Persistent chemical residues from some of these products have been identified as a potential environmental risk when the wool is processed at scouring plants (Anon., 2006). Furthermore, the uneven distribution and persistence of sub-lethal concentrations of chemicals in the fleece have been implicated in '5 accelerating the development of insecticide resistance within sheep lice populations (Johnson, Boray & Dawson, 1992; Rothwell, 2005). Insecticide resistance within sheep lice populations in Australia has become a significant problem. Reports of synthetic pyrethroid (SP)-based lousicide failures became frequent in the mid-1 980s and resistance to the insect growth regulator (benzoylphenyl urea) pour-on products o emerged around 2003-2004 (Levot & Sales, 2008). Chemical groups to which sheep lice in Australia are generally regarded as susceptible include the organophosphates (OPs), macrocyclic lactones (MLs), neonicotinoids and spinosyns. However, the limited number of different product formulations containing these chemicals restricts the ability of sheep producers to choose between different methods of application. 5 It is evident that an ideal lousicide will: 1) Incorporate an active ingredient to which sheep lice are known to be susceptible 2) Deliver a high level of lousicidal efficacy 3) Be safe for administration to sheep 4) Rapidly deliver lethal insecticide concentrations to all areas of skin where the lice reside .0 5) Be convenient for the operator to apply 6) Minimise operator exposure to the chemical 7) Ensure minimal chemical residues persist in the fleece 8) Not require disposal of used or excess chemical into the environment It can therefore be seen why there is continued research to find effective ways to treat 25 ectoparasites - biting ones in particular. An ideal treatment would achieve a high insect mortality rate (via even exposure of the parasites to lethal chemical concentrations), have no detrimental effects on the host animal, be cost effective and not labour intensive, and it would be safe for operators and the environment. It is an object of the present invention to address the foregoing problems or at least to provide 30 the public with a useful choice. All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly 35 understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the 3 common general knowledge in the art, in New Zealand or in any other country. Throughout this specification, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, 5 or group of elements, integers or steps. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF THE INVENTION 0 According to one aspect of the present invention there is provided a method of treating an animal infested with biting lice characterised by the step of administering internally to the animal a pharmaceutically effective amount of at least one spinosyn such that the spinosyn is present systemically within the animal. 5 According to a further aspect of the present invention there is provided a composition when used for internal administration to an animal to treat biting lice, the composition including at least one spinosyn in the order of 0.1% to 65 w/v. According to a further aspect of the present invention there is provided a use of a composition including a pharmaceutically effective amount of at least one spinosyn, wherein the use .0 includes administering the composition internally to the animal such that the spinosyn is present systemically within the animal, characterised in that the use of the composition is for the treatment or prevention of biting lice. According to yet another aspect of the present invention there is provided a dosage regime to treat biting lice on an animal characterised by the step of administering at least one spinosyn 25 internally to the animal with a total dosage of equal to or less than 100 milligrams per kilogram animal. Throughout the specification, the use of the present invention will be described mainly in relation to the treatment of biting lice on sheep (Bovicola ovis). It should be appreciated however that the principles in the present invention could apply to and be useful for other 30 situations - for example treating biting insects on other ruminant and camelid species. Many of the problems associated with sheep are also present in, for example, cows, goats, and alpaca, albeit with different species of biting lice. The inventors expect that the present invention may 4 be applicable, for reasons discussed herein, to many animals that are prone to, or suffer from, biting lice. Such animals that are prone to different species of biting and sucking lice are well documented, for instance as outlined in the published document below (herein incorporated entirely by reference): 5 http://www.pested.msu edu/resources/buletins/pdf/2601/pne2601ca4.pdf The medicament can be administered to the animal by a variety of means. For example, in one embodiment the medicament may be administered orally, for example with a drench gun such as that used for other medicaments. Alternatively, an injectable liquid may be used and delivered via an injector - for example such 0 as that used to deliver antibiotics. However other methods may be incorporated, for example solid dose forms (e.g. tablets, pellets, boluses, implants) or other routes of administration/absorption (e.g. transcutaneous, transmucosal). A critical aspect of the invention however is that regardless of the mode of administration, the 5 spinosyn is present systemically within the animal. Overview of prior art uses of spinosyn and other lousicides The first major chemical group that included systemic pesticides used for control of ectoparasites on animals were the organophosphates (OPs). These systemically-active chemicals were absorbed by the animal and carried, via the bloodstream, to the parasite (Khan, .0 1964; Pitman & Rostas, 1981). During the 1960s there was a significant focus on development of systemic parasiticides for livestock with over 100 new compounds tested during this period (Khan, 1969). The new, systemically-active compounds significantly influenced the evolution of ectoparasiticide products for livestock and three major trends were identified by Drummond (1985): 25 1) A reduction in the amount of material applied dermally (i.e. from spray or dip, to pour-on, to spot-on) 2) Increasing use of oral or percutaneously-absorbed chemicals to control various ectoparasites 3) The development of sustained-release devices to provide prolonged efficacy 30 During this period extensive research was conducted into the systemic OP chemicals for use in livestock species. There was a universal shift from high-volume to low-volume dermal application methods (e.g. from dip to pour-on formulations) and the introduction of alternative routes of administration of systemic ectoparasiticides (i.e. oral or injectable). Despite these developments to products for other livestock and/or parasite species, no such advances 5 occurred in the control of sheep lice, which are known to be biting lice not sucking lice. That is, until introduction of the (non-systemic) SP pour-ons in the early 1980s. Therefore, for two decades (i.e. from 1958 until registration of the SPs), Australian sheep producers were reliant upon OP and arsenic-based dips for control of sheep lice (Levot, 2001). 5 Numerous OPs were available for use on sheep, the most popular including: diazinon, chlorfenvinphos, coumaphos, fenthionethyl and carbophenothion (Levot 2001). These chemicals were usually applied by plunge or shower dipping - a mode of application intended to bring the chemical into contact with the parasite rather than via systemic absorption (Pitman & Rostas, 1981). Unfortunately, during this period, "the incidence of properties with lice was 25 0 30%" and "many treatments were ineffective" (Levot, 2001). In addition, there was regulatory pressure to quarantine those flocks affected (Levot, 2001). Within this context there was certainly strong demand for new and effective sheep lousicide products during the 1960s and 1970s in Australia. Unfortunately none of the developments in OP control of biting lice on other livestock species, e.g. cattle, were successful in sheep. For 5 example, a fenthion-based product for sheep (Tiguvon@ Sheep Dip) was available in Australia from the late 1960s. The efficacy of fenthion as a systemic insecticide for use in cattle was described in 1967 (Cox, Mullee & Allen, 1967). Despite the subsequent development of fenthion into a highly-effective systemic spot-on for sucking and biting lice on cattle (Tiguvon@ Spot-On Cattle Lice Insecticide), released in the early 1970s, a low-volume fenthion-based product was .0 never successfully developed for control of sheep lice. Coumaphos was another OP with established systemic activity in cattle (Cox, Mullee & Allen, 1967) that was used extensively for control of sheep lice in Australia from the 1960s. As for fenthion, neither coumaphos nor any of the other OP chemicals with recognised systemic activity in other species and/or against blood-feeding parasites of sheep were developed into 25 systemically-active products for sheep lice control. The next major class of parasiticides to be developed with systemic activity were the MLs. These chemicals have been used extensively for control of internal and external parasites of sheep and cattle since abamectin was introduced in Australia in 1985 (Holdsworth, 2005). The term 'endectocide' was coined to describe the MLs because they have been so successful for 30 control of both internal (endo-) and external (ecto-) parasites. Abamectin, ivermectin, doramectin eprinomectin and moxidectin have all demonstrated activity against biting lice on cattle, i.e. Bovicola bovis (Titchener et al, 1994; Clymer et al, 1998; Colwell, 2002; Holste, 1997; Lloyd et al, 2001; Lloyd et al, 1996). However, due to their skin surface feeding habits, B. bovis are more susceptible to the topical formulations of MLs applied 35 on or near the sites of infestation than those administered by injection (Logan et al, 1993; Cleale, 2004). Consistent with this observation is the fact that "sucking lice are typically more 6 susceptible to injectable formulations of macrocyclic lactones than are chewing lice" (Cleale et al, 2004). Although the purely systemic route of ML delivery to B. bovis is not ideal, injectable products based on doramectin and moxidectin carry claims to "aid in the control" of this parasite in 5 Australia. Products based on all of the MLs (except eprinomectin and doramectin) have been registered and used extensively since the 1980s for control of internal parasites of sheep in Australia. Topical formulations, i.e. an ivermectin jetting concentrate and an abamectin pour-on, have been used for control of B. ovis on sheep. However, despite the experience with biting lice in cattle, none of the MLs delivered via the o systemic route have been registered for control of biting lice on sheep. Likewise, a search of the published literature does not yield evidence of any of the MLs providing control of these sheep lice when administered via the systemic route. Doramectin has shown efficacy against biting lice when administered by injection to cattle. Based on published literature (Barber et al, 2003), this formulation was selected as a good 5 candidate to provide sufficient systemic levels to control sheep lice following injection. Yet, doses up to 3-times that recommended for cattle were administered to sheep with natural infestations of B. ovis. No efficacy against the lice populations was observed (data not published). The consensus in published literature is that, despite their activity against other ectoparasites of .0 sheep, the MLs delivered via the systemic route do not provide effective control of the biting louse, B. ovis (Coop et al, 2002; Bates, 2004). In reference to B. ovis, Bates (2012) states clearly: "No ML injection is effective against chewing lice". The reasons for the differences observed in ML activity following systemic administration for biting lice on cattle and sheep are unclear. Although related, B. bovis and B. ovis are distinct 25 species of biting lice, which are known to be very host-specific. This means that each louse species is highly adapted to its particular host animal species. In other words, B. bovis cannot infest sheep and B. ovis cannot infest cattle. Given that the lice are host-adapted, there may be differences in their biology (e.g. preferred skin substrates to feed on, frequency of feeding, proximity to skin surface, mobility) that make B. bovis on cattle more susceptible to MLs (and 30 perhaps OPs) delivered via the systemic route. Theoretically, some chemicals present in the blood stream may be delivered to the skin surface by diffusion between cells of the skin (intercellular), diffusion through cells of the skin (intracellular), diffusion into the hair follicles, secretion in sweat, secretion in sebum or by accumulation inside epidermal cells which gradually move towards the skin surface (Patzelt et 35 al 2008). 7 It is not known precisely which of these mechanisms are responsible for the delivery of ML and OP chemicals to the skin surface of cattle where they can exert an effect on B. bovis. However, marked differences in the skin layers and appendages (i.e. hair follicles, sebaceous glands and sweat glands) are known to occur between different species. 5 For example, cattle skin may have around 890 follicles/cm2 whereas a Merino sheep can have up to 10,000 follicles/cm2 (Mills & Cross, 2006). The density of blood vessels, thickness of the skin, and the rate and composition of the sebaceous secretions can also differ (Mills & Cross, 2006). It is evident that the significant structural and physiological differences between the skin of cattle and sheep could certainly influence the delivery of chemicals to biting lice feeding on 0 the skin surface. Also, the different structural and chemical features that exist between compounds are known to have a considerable and often unpredictable consequence on their potential to transfer from the bloodstream to the skin surface in humans (Patzelt et al 2008). The same variability is expected in other mammals and further compounded by the physiological differences between 5 non-human species. Therefore, although OPs and MLs have been shown to have a therapeutic effect against biting lice in cattle when administered systemically, it does not translate that other actives will be able transfer to such vectors in a similar mode of action. WO 0111961 and WO 0111962 (Eli Lilly and Company) both describe formulations containing spinosyn for controlling insects/pests in small ruminants, such as sheep and goats. The .0 formulations and methods of controlling these insects/pests are described as being topically applied to a ruminant. This follows the general understanding that to treat biting lice, such as those seen on sheep, the spinosyn containing composition was topically applied. This general consensus is further supported by the review of spinosyns and their use in Kirst et a/ 2 . 25 NZ 516790 describes an oral formulation for controlling an ectoparasite infestation on a companion animal for a prolonged time, said formulations comprising a spinosyn component. NZ 516790 follows conventional wisdom in that it describes a method of treatment only to be used for killing sucking lice, which feed from the blood of the animal. Pages 7-8 of NZ 516790 provides a good overview on the understanding and spinosad usage 30 for treating lice: "Systemic efficacy (ingestion of blood containing spinosad by the blood feeding parasites, such as fleas) provides different mode of exposure compared to topically applied ectoparasitcides where contact with the parasite at the skin surface is the mode of exposure. The advantages of oral systemic treatments and killing of parasites from 35 ingestion of blood, compared to topical applications and contact killing include: 8 a) Reduced exposure to the human applicator and children and objects in the animal's environment (e.g. flooring, carpets, furniture), b) No worry about loss from exposure of the animal to water (lakes, streams, bathing, etc) or from loss due to rubbing, 5 c) No concern about UV exposure and degradation d) No problems with oxidation from oils on skin, etc; and e) Assurance that the entire dose is administered (compared to a topical application where some of the dose may drip off, rub off and/or maintain in the dispensing tube immediately after treatment)." [EMPHASIS ADDED] 0 It is clear from this passage that there are many advantages to systemic treatment opposed to topical treatment for killing lice. WO 03024223 describes the use of a synergistic combination of spinosad and a macrocyclic lactone. The trials therein show that systemic use of spinosad is more effective than contact application. However, opposite the present invention, the term "systemic" is used in regard to 5 the pest (i.e lice) rather than the host (e.g. sheep). While the trials did determine that ingestion of sheep epidermis treated with the composition is effective in killing the lice, it does not teach that systemic administration to the host is effective at killing the lice. Given the different structure of the skin between sheep and cattle, and the general understanding in the art, as discussed above, it would be unexpected that systemic .0 administration of a spinosyn would provide a therapeutic effect by killing biting lice such as those on sheep. It can be summarised that it has been commonly understood and is general practice to: - treat biting lice with topically applied spinosyn compositions as the active agent will be present on the external surfaces which are ingested by the lice; or 25 - treat sucking lice with systemically applied spinosyn compositions as the active agent will be present in the blood. Definitions Throughout this specification, the term spinosyn (also known as fermentation product A83543) should be taken as meaning any compound, a derivative or analogue thereof, either naturally 30 derived or synthetically derived, generally having a 5,6,5-tricyclic ring system, fused to a 12 membered macrocyclic lactone, a neutral sugar (2N,3N,4N-tri-O-methylrhamnose) and an amino sugar (forosamine). The meaning of spinosyn is further outlined in NZ 531787, the contents of which are incorporated herein in its entirety for reference. 2 Current Topics in Medicinal Chemistry 2002, 2, pages 675-699 9 R1 OR C 0I OCH3 0; H yO OR6 R4 HH ~~~ H The family of natural components of A83543 include a genus taught in EP 0375316 and having the general formula: wherein R 1 is H or a group selected from (C H 3

)

2 N H 3 (C H 3 )N H (a)(b

H

2 NCH or) (CH3) N

CH

3 (d) and R 2 , R 4 , R 3 , R 5 and R 6 are hydrogen or methyl; or an acid addition salt thereof when R 1 is other than hydrogen. Spinosyns are known to occur in over 20 natural forms and currently can be provided in over 200 synthetic forms. Incorporated herein by reference, Kirst et al and NZ 516790 further 10 outlines the scope and variants of spinosyns. As discussed in Kirst et aland NZ 516790, one such example is Spinosad which includes a racemic mix of two spinosyns, Spinosyn A, the major component and Spinosyn D (the minor component), an approximate 17:3 ratio. An example of a more recent spinosyn derivative is 'spinetoram' which, when compared to Spinosad, has been found to be effective against a greater spectrum of insect pests with an 15 increased potency and duration of efficacy 3

,

4 . Spinetoram includes a major component (3'ethoxy-5,6-dihydro spinosyn J) and a minor component (3'-ethoxy spinosyn L). 3 Sparks, T.C., Watson, G.B. and Dripps, J.E. (2010) A6 Addendum: The Spinosyns. In: Insect Control: Biological and Synthetic Agents, Eds: Gilbert LI. and Gill, S.S., Academic Press, London 4 Kirst, H.A. (2010) The spinosyn family of insecticides: realizing the potential of natural products research, The Journal of Antibiotics, vol. 63, pp 101-111. 10 Throughout this specification, the term biting/chewing lice should be taken as meaning ectoparasites whose mouthparts are adapted for chewing, and eat skin fragments, skin secretions, feathers, hair and/or wool. Throughout this specification, the term sucking lice should be taken as meaning ectoparasites 5 whose mouthparts are adapted for sucking the blood of their host. Throughout this specification, the term systemic treatment should be taken as meaning any treatment which is applied internally to an animal and which reaches different areas of the body primarily through the bloodstream. For example, this may include oral, parenteral, and anal delivery. 0 Throughout this specification, the term topical treatment should be taken as meaning any treatment which is applied onto an external surface of an animal such as the skin or hair/wool of an animal. Throughout this specification, the term Bovicola ovis should be taken as meaning a sheep body louse (plural = lice). 5 Preferred embodiments of the present invention Preferred method of treatment Preferably the biting lice is the species Bovicola ovis (B.ovis). As discussed previously, it was very unexpected that spinosyn, when administered systemically, would have been effective in treating biting lice (B.ovis) in sheep, especially due to .0 the different characteristics between the skin of sheep and other animals (e.g. cows). Preferably the animal is a sheep. Bovicola ovis is a species of lice specific to sheep, known to be biting lice rather than sucking lice. With knowledge of the present invention, the inventors extrapolated that spinosyn may also be effective for systemic treatment of biting lice present in other animals beyond sheep. 25 Preferably, the administration route is oral. For example, it is envisaged that the composition may be provided as a suspension, tablet, powder, drench or the like. Alternatively, the administration route is via injection. Regardless of whether the administration is oral or via injection, the main advantage of 30 systemic administration is that it helps to ensure the total dosage is being given to the animal. With topical administration, as per conventional wisdom with spinosyns used for biting lice, the 11 disadvantage is the dosed medicament may be licked off by other animals, rubbed off by the animal or possibly be washed away in rain. Preferably, the spinosyn is spinosad. As noted above, spinosad is a mixture of spinosyn A and spinosyn D. These two spinosyns are 5 currently known as very effective types of spinosyn insecticides. Also, spinosad is beneficial to use as per the present invention, as it is already used both topically (for biting lice) and systemically (for sucking lice). Therefore, it is known to be safe to use, has low side effects and has widespread approval amongst the farming industry. Of course, it should be recognized that other forms of spinosyn (whether currently available or o developed in future) may be used in the present invention without departing from the scope thereof. One such preferred example of a spinosyn derivative, more recently identified as being particularly effective, is spinetoram. Indeed, it is thought that other members of the spinosyn insecticide class may also have the physicochemical properties, similar to spinosad, that are required to be effective via this route. 5 It is believed by the inventor that contrary to expectations, a systemic introduction of a spinosyn causes the chemical to be present in vectors that biting lice feed on, for example skin, skin secretions and associated debris (e.g. dead cells) at concentrations sufficient to be lousicidal. It should be appreciated that the present invention can be co-formulated with other active ingredients, for example anthelmintic treatments, vaccines, vitamins/mineral supplements and .0 the like. Not only does this offer advantages by having two or more treatments being delivered in a single dose, but there may also be complementary effects resulting. For example, the inclusion of vitamins and minerals may assist the skin recovery of an animal once the biting lice have disappeared as a result of the insecticide treatment. Preferred composition 25 It is envisaged that preferred compositions will include spinosyn in the order of 0.1 % to 65 % w/v as. Preferably, the concentration of spinosyn is 1 % to 35% w/v. More preferably, the concentration of spinosyn is approximately 9 % w/v. In preferred formulations, in addition to the active there may be provided dispersing agents, 30 preservatives, anti-foaming agents and humectants. Preferably, the composition is prepared as an oral composition. For example, this may be in the format of a tablet, powder, drench, gel and so forth. 12 Alternatively, the composition may be in the form of an injectable composition or sustained release composition such as a bolus or implant, or the like. Preferred dosage In the past, Spinosyn previously was administered topically for treatment of biting lice. One of 5 the advantages identified by the inventors in administering spinosyn systemically was the lower than expected dose that is required to be therapeutically effective in ridding the animal of biting lice. After the inventors arrived at the present invention, the transfer of the Spinosyn from blood to the external skin surface was still expected to be inefficient and only partial, at best. Instead, the lower concentrations and dosages used in tudies were for the most part highly effective at o killing biting lice, despite being at levels similar to or even below those described in NZ 516790 (for killing sucking lice). This was quite unexpected, and is a considerable advantage, as outlined further below. Trial 1 (see Best Mode section) identified that a daily dosage of about 1620 mg per sheep was found to be an effective and safe (due to the inherent safety of spinosyns such as spinosad). 5 However, the inventors were surprised to find that the dosage could be lowered significantly below 1620 mg per sheep yet still provide a therapeutic effect. Therefore, preferably, the daily dosage administered (mg/per sheep) is less than about 2000 mg/sheep/day. More preferably, the dosage may be between 100 - 2000 mg/sheep/day. .0 One significant advantage of these findings is reducing production costs. A further advantage may be lowering side effects, avoiding a build-up of resistance, and so forth. Preferably, the spinosyn is administered at total dosage of equal to or less than 100 milligrams per kilogram of animal. Although preliminary trials showed no harmful effects were seen when higher total dosages 25 (e.g. 80 mg per kg) were used, lower dosages also showed acceptable therapeutic effects. For instance, after 14 days post treatment (one dosage of 6.75 mg spinosad per kg animal on day 0), the inventors observed a total depletion of live lice on the sheep. Although a further 10-fold reduction in dosage (0.675 mg/kg animal) led to only partial reduction of live lice on the sheep, the inventors still expect that the dosage may be reduced 30 significantly below 6.75 mg/kg; for example to a total dosage of about 1-6 mg/kg animal. The dosage regime may also vary significantly. In preliminary trials, the inventors identified that either a single or double dosage of 6.75 mg/kg/day (i.e. just on day 0, or on both day 0 and day 13 1) regime was sufficient to eradicate the lice. However, other regimes may also be suitable, for example depending on the severity of the condition. For example, this may include the administration of a number of discrete dosages over a few days, or alternate embodiments could involve the use of a slow release device. One such 5 possibility is a sustained release product which releases the active at low levels over a given period of time, such as 3-7 days. Naturally, the composition being administered will vary dependent upon the administration route and whether a single dose will be used or the active is to be administered over time. Further, as discussed previously, the present invention can be used with other actives as well. 0 It can be seen that the present invention has a number of advantages over the prior art. Firstly, there is provided an alternate treatment for biting lice which does not have the intensive labour requirement, capital overheads and potential human health risks of topical treatments. Further, by determining a systemic administration route, and an appropriate dosage level then equal delivery of a sufficiently high dosage to all of the parasites can be ensured - providing 5 reliable efficacy and avoiding factors that accelerate the development of insecticide resistance. Further, minimisation of insecticide residues in the fleece will reduce the risks to the environment secondary to wool processing. BEST MODES FOR CARRYING OUT THE INVENTION .0 Preferred compositions are shown in examples 1 to 4. Example 1: Injectable composition A composition suitable for administration by injection is provided in Table 1. 25 Ingredient Quantity %w/v Spinosad 5 NMP 35 Castor oil 14 BHT 0.05 Soyabean oil qs Table 1 14 Example 2: Tablet composition A composition for a 1000 mg tablet, suitable for oral administration is provided in Table 2. Ingredient Quantity mg/tablet Quantity %w/w Spinosad 315 31.5 Monopropylene glycol 55 5.5 Povidone K 30 26 2.6 Dicalcium Phosphate 150 15.0 Microcrystalline Cellulose 150 15.0 Sodium starch glycolate 265 26.5 Aerosil 200 18 1.8 Magnesium stearate 21 2.1 Table 2 Example 3: Tablet composition 0 A further composition for a tablet, suitable for oral administration is provided in Table 3. Ingredient Quantity mg/tablet Quantity %w/w Spinosad 315 31.5 Microcrystalline cellulose 150 15.0 Lactose 285 28.5 Sodium starch glycolate 150 15.0 Povidone K 30 30 3.0 Magnesium stearate 50 5.0 Silicon dioxide, colloidal 20 2.0 Table 3 15 15 Example 4: Oral drench composition A composition suitable for administration as an oral drench is provided in Table 4. Ingredient Quantity %w/v Spinosad 9.0 Propylene glycol 12 Tween 80 12 Benzyl alcohol 1.0 Sodium metabisulphite 0.1 PVP K25 2.5 Aerosil 200 1.0 Defoamer RD 0.2 Citric acid 1.9 Deionised water q.s. 5 Table 4 Example 5: Trial 1 In a first trial, a number of lousicide agents were tested to determine their efficacy for treating biting lice on sheep (B. ovis) when administered systemically. It was expected as per 0 conventional wisdom that systemic administration would not present the active compound in vectors which would be consumed by the biting lice. Treatment Group Dose level Dosage regime No. Pre-treatment - Day 14 Sheep arithmetic mean arithmetic lice per sheep mean lice per sheep 1. Untreated - 5 316.8 296.2 2. Ivermectin 0.2 mg/kg Once daily for 3 days 5 336.6 286.0 3. Spinosad 1620 mg/sheep Once daily for 3 days 5 296.4 0.0 4. Imidacloprid 5 mg/kg Once daily for 3 days 5 257.6 245.4 Table 5 16 Contrary to expectations, trial 1 illustrated that at 14 days after treatment the live lice on sheep dropped to zero for the spinosad group (group 3) but appeared unaffected in the imidacloprid and ivermectin-treatment groups (group 2 and 4). This supported that spinosad, unlike ivermectin and imidacloprid, unexpectantly was able to present itself to the biting lice. 5 Example 6: Trial 2 Building on the results seen in trial 1, the results of preliminary trial 2 further supports the efficacy of systemically administered spinosyn(s) for control and treatment of biting lice, such as those of sheep (B. ovis). This trial also illustrates the potential dosage requirements necessary to achieve a required therapeutic effect. o Five groups of sheep were treated with a range of oral dosages of spinosad as detailed in Table 6. The average weight of the sheep in the trail was approximately 40 kg. The dosage form used for the trial was the commercially available tablet ComfortisTM, by ElancoTM. The tablets used in the trial contained either 270 mg or 1620 mg of spinosad. The assessment of live lice present on the animals after days 5, 14, 30 and 56 is provided as a 5 mean for each group in Table 7. Four groups showed 100% reduction in lice numbers. The lowest dose group showed only a partial and short-lived reduction in live lice numbers. Blood plasma levels and fleece concentrations of spinosad were determined for two of the groups, as shown in Tables 8 and 9. Plasma and fleece concentrations correlated with the dose administered. .0 The study again showed, contrary to expectations and what would be expected for the treatment of biting lice, that systemic administration of spinosad is able to present itself in at least one vector (e.g. wool) which contains substrates that are eaten by the biting lice, thereby providing a preventative and/or therapeutic effect. 25 Daily Dose Daily Dose Total Dose No Treatment Group Administered Administered Dosing Regime Administered No. (mg/sheep) (approx. mg/kg) (approx. mg/kg) Sheep 1. Spinosad 27 mg 27 mg/sheep* 0.675* Once on Day 0 0.675 5 2. Spinosad 270 mg 270 mg/sheep 6.75 Once on Day 0 6.75 5 3. Spinosad 540 mg 270 mg/sheep 6.75 Once n Day 0 13.5 5 4. Spinosad 1620 mg 162/heep 40.5 Once on Day 0 40.5 5 5. Spinosad 3240 mg 1620 40.5 Once on Day 0 81 5 ____________mg/sheep _ ______and Day 1_______ ____ Table 6: Dosage regime of five treatment groups. 17 *A single 270 mg spinosad tablet was ground finely and evenly suspended in approx. 50 mL of water. Each sheep in Group 1 received 5 mL of the suspension. Treatment Group Total Dose Mean No. Live Lice per Sheep Administered (approx. mg/kg) Day -5 Day 14 Day 30 Day 56 1. Spinosad 27 mg 0.675 269.0 51.2 241.2 446.0 2. Spinosad 270 mg 6.75 337.4 0.0 0.2 0.0 3. Spinosad 270 mg + 270 mg 13.5 261.2 0.0 0.0 0.0 4. Spinosad 1620 mg 40.5 246.2 0.0 0.0 0.0 5. Spinosad 1620 mg + 1620 mg 81 212.0 0.0 0.0 0.0 5 Table 7: Assessment of live lice per sheep over time in five treatment groups Total Dose Mean Spinosad Concentration in Wool Treatment Group Administered (mg/kg) (approx. mg/kg) Day 14 Day 30 2. Spinosad 270 mg 6.75 0.33 0.20 4. Spinosad 1620 mg 40.5 2.26 0.84 0 Table 8: Assessment of mean spinosad concentration in wool over time in treatment groups 2 and 4. Total Dose Spinosad Concentration in Composite Plasma Samples Treatment Group Administered (mg/L) (approx. mg/kg) 2 hours 4 hours 8 hours 24 hours 48 hours 2. Spinosad 270 mg 6.75 0 0.035 0.064 0.076 0.056 4. Spinosad 1620 mg 40.5 0.049 0.17 0.42 0.4 0.18 15 Table 9: Assessment of spinosad concentration in plasma in treatment groups 2 and 4. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the 20 scope thereof as defined in the appended claims. 18

Claims (20)

1. A method of treating an animal infested with biting lice characterised by the step of administering internally to the animal a pharmaceutically effective amount of spinosyn such that the spinosyn is present systemically within the animal.

2. A method as claimed in claim 1 wherein the biting lice is the species Bovicola ovis.

3. A method as claimed in either claim 1 or claim 2 wherein the animal is a sheep.

4. A method as claimed in any one of claims 1 to 3 wherein the administration route is oral.

5. A method as claimed in any one of claims 1 to 4 wherein the spinosyn is spinosad.

6. A method as claimed in any one of claims 1 to 4 wherein the spinosyn is spinetoram.

7. A method as claimed in any one of claims 1 to 6 wherein the spinosyn is administered in a total dosage of equal to or less than 40 milligrams per kilogram of the animal.

8. A method as claimed in any one of claims 1 to 7 wherein the spinosyn is administered over a period of time.

9. A method as claimed in claim 8 wherein the spinosyn is administered in multiple doses.

10. A method as claimed in claim 8 wherein the spinosyn is administered in slow release form.

11. A composition for internal administration to an animal including a spinosyn in the order of 0.1% to 65% w/v.

12. A dosage regime to treat biting lice on an animal characterised by the step of administering a spinosyn internally with a dosage equal to or less than 40 milligrams per kilogram of the animal.

13. A dosage regime as claimed in claim 12 wherein the administration is over a period of time.

14. A dosage regime as claimed in claim 12 wherein the spinosyn is administered in multiple doses.

15. A dosage regime as claimed in claim 13 wherein the spinosyn is administered by a slow release route. 19

16. A dosage regime as claimed in any one of claims 12 to 15 wherein the dosage is administered to the animal in the order of equal to or less than 40 milligrams of spinosyn per kilogram of animal.

17. A dosage regime as claimed in the previous claim wherein the spinosyn is administered to the animal in the order of two or more 1 to 6 milligrams per kilogram dosages spaced apart by a day or more.

18. A method substantially as herein described in the Best Modes Section.

19. A composition substantially as herein described in the Best Modes Section.

20. A dosage regime substantially as herein described in the Best Modes Section. 20