METHOD OF TREATING PARASITES

TECHNICAL FIELD

The invention relates to treating or preventing an infestation by a parasite in or on an animal .

BACKGROUND ART

Macrocyclic lactones are used to treat infestations by endoparasites and ectoparasites in or on animals. Macrocyclic lactones include the LL-F28249 compounds, the milbemycins and the avermectins .

The LL-F28249 family of compounds are natural endectocidal agents isolated from the fermentation broth of Streptomyces cyaneogriseus subsp. noncyanogenus . The LL- F28249 family of compounds includes moxidectin.

The milbemycins, also known as the B-41 series of antibiotics, are naturally occurring macrocyclic lactones isolated from the microorganism Streptomyces hygroscopicus subsp. aureolacrϊmosus. The milbemycins include milbemycin A, milbemycin B, milbemycin D and others.

The avermectins, also known as the C-076 family of compounds, are a family of closely related compounds produced by Streptomyces avermitilis or by synthetic or semisynthetic means. Members of the avermectin family include avermectin A _Xa , A _2a , B _la , B _2a , Ai _b , A _2b , B _ib and B _2b . The avermectins include ivermectin, abamectin, doramectin, eprinomectin and others.

Ivermectin is a semisynthetic derivative of abamectin. Ivermectin contains at least 80% of 22,23- dihydroavermeetin Bi _a and not more than 20% of 22,23- dihydroavermectin Bχ _b .

Macrocyclic lactones, including ivermectin, have been used

to treat endoparasites, such as worms, and ectoparasites, such as lice and mites, in or on animals.

The formulations containing ivermectin approved for use in Australia for the treatment of parasites in or on pigs are formulations that are administered in admixture with the animal's feed or administered by subcutaneous injection. Oral drenches containing ivermectin have been approved for use in Australia to treat parasites in or on horses, dogs, cattle and sheep. Topical formulations containing a macrocyclic lactone have been approved for use in Australia to treat parasites in or on cattle.

DISCLOSURE OF INVENTION In a first aspect, the present invention provides a method of treating or preventing an infestation by a parasite in or on an animal, the method comprising providing an aqueous formulation comprising a macrocyclic lactone to the animal and allowing the animal to drink the aqueous formulation for an extended period.

The extended period during which the animal is allowed to drink the aqueous formulation is typically greater than about 6 days. In some embodiments, the extended period is from about 7 to about 14 days. In other embodiments, the extended period is about 3 months or about 100 days.

The macrocyclic lactone is present in the aqueous formulation at a concentration such that by drinking the aqueous formulation, the animal consumes a parasiticidally effective amount of the macrocyclic lactone.

In some embodiments, the aqueous formulation comprises the macrocyclic lactone at a concentration such that when the aqueous formulation is drunk by the animal, the animal consumes about 50 to about 300 μg, for example, about 100 to about 300 μg, of the macrocyclic lactone per kg

liveweight of the animal per day.

Typically the aqueous formulation is the only, or the principal, source of water available to the animal for drinking .

Preferably, the macrocyclic lactone is in solution in the aqueous formulation.

The macrocyclic lactone may be any macrocyclic lactone.

The macrocyclic lactone may be an LL-F28249 compound (for example, moxidectin) , a milbemycin (for example, milbemycin A, milbemycin B or milbemycin D) , or an avermectin (for example, ivermectin, abermectin, doramectin or eprinomectin) . In some embodiments, the macrocyclic lactone is ivermectin.

In some embodiments, the aqueous formulation comprises two or more macrocyclic lactones.

Typically the animal is an intensively farmed animal kept in a controlled environment. The animal may be a mammal or a bird. The animal may, for example, be a pig, poultry (e.g. a chicken, turkey, guineafowl, duck or goose), cattle (e.g. cattle kept in a feed lot) or sheep.

The parasite may be a worm, lice or mite. For example, if the animal is a pig, the parasite may be selected from one or more of gastrointestinal roundworms, kidney worms, lungworms, lice and mange mites.

In some embodiments, the macrocyclic lactone is provided in a concentrate that is added to a source of water available to the animal for drinking, to produce the aqueous formulation.

In one embodiment, the present invention provides a method

of treating or preventing an infestation by a parasite in or on an animal, comprising mixing a formulation comprising: one or more macrocyclic lactones; one or more co-solvents;r one or more preservatives; one or more buffers; and water, with a source of water available to the animal for drinking to form an aqueous formulation comprising the one or more macrocyclic lactones, and allowing the animal to drink the aqueous formulation for an extended period.

In a second aspect, the present invention provides a method of treating or preventing an infestation by a parasite in or on an animal, the method comprising administering a macrocyclic lactone in an amount of from about 50 to about 300 μg per kg liveweight of the animal per day to the animal in the animal's drinking water for an extended period.

In a third aspect, the present invention provides a formulation comprising: one or more macrocyclic lactones; one or more co-solvents; one or more preservatives; one or more buffers; and water, when added to a source of water available to an animal for drinking .

In a fourth aspect, the present invention provides a formulation comprising: one or more macrocyclic lactones; one or more co-solvents; one or more preservatives; one or more buffers; and

water, when added to a source of water available to an animal for drinking to form the aqueous formulation used in the method of the first aspect of the present invention.

The formulation of the third or fourth aspect of the present invention may be added to the source of water available to the animal for drinking in an amount which results in the source of water comprising the one or more macrocyclic lactones in an amount of from about 250 to about 10,000 μg/L.

In some embodiments, the one or more macrocyclic lactones is in solution in the formulation of the third or fourth aspect of the present invention.

In some embodiments, the formulation of the third or fourth aspect of the present invention comprises: the macrocyclic lactone (s) in an amount of 0.1 to 100 g/L; the co-solvent (s) in an amount of 200 to 300 g/L; the preservative (s) in an amount of 20 to 50 g/L; and the buffer (s) in an amount of 8 to 15 g/L.

MODE(S) FOR CARRYING OUT THE INVENTION

It has been found that parasites in or on an animal can be treated by administering a macrocyclic lactone over an extended period of time in the water drunk by the animal. Surprisingly, administering macrocyclic lactones to the animal via this route provides a number of advantages over administration of macrocyclic lactones in admixture with the animal's feed, by subcutaneous injection or by an oral drench .

In one aspect, the present invention provides a method of treating or preventing an infestation by a parasite in or

on an animal, the method comprising providing an aqueous formulation comprising a macrocyclic lactone to the animal and allowing the animal to drink the aqueous formulation for an extended period.

Typically the aqueous formulation is prepared and provided to the animal by adding the macrocyclic lactone to a source of water available to the animal for drinking, that is, the macrocyclic lactone is added to the animal's drinking water.

Typically the macrocyclic lactone is added to all sources of water available to the animal for drinking.

Typically the macrocyclic lactone is added to the source of water available to the animal for drinking in an amount such that the resultant aqueous formulation comprises from about 250 to about 10,000 μg/L of the macrocyclic lactone. In some embodiments, the aqueous formulation comprises the macrocyclic lactone in an amount of from about 250 to about 2,500 μg/L. In some embodiments, the concentration of the macrocyclic lactone in the aqueous formulation is from about 500 to about 2,500 μg/L. In some embodiments, the concentration is less than about 2,000 μg/L.

Typically, the aqueous formulation comprises the macrocyclic lactone at a concentration such that when the animal drinks the aqueous formulation, the animal consumes about 50 to about 300 μg of the macrocyclic lactone per kg liveweight of the animal per day.

The extended period is typically a period of more than about 6 days. In some embodiments, the extended period is a period of more than about 7 days, for example, a period of from about 7 to about 100 days (e.g. from about 7 to

about 14 days) . In other embodiments, for example where the animal is infected with a very persistent parasite, it may be more appropriate to treat the animal for a period of 14 to 21 days or longer. In some embodiments, the extended period is 7 days, 10 days, 14 days, 21 days or 28 days. In some embodiments, the extended period is 60 days, 90 days, 3 months or 100 days.

In some embodiments, the macrocyclic lactone is ivermectin. However, other macrocyclic lactones may be used. In some embodiments, the aqueous formulation comprises two or more macrocyclic lactones.

Typically the macrocyclic lactone is in solution in the aqueous formulation.

The methods of the present invention may be used to treat or prevent an infestation by any parasite that is killed or whose growth or reproduction is inhibited by a macrocyclic lactone.

For example, ivermectin and other macrocyclic lactones can be used to treat or prevent infestations by worms, lice and mange mites in or on an animal. When the macrocyclic lactone is ivermectin, the methods of the present invention can, for example, be used to treat or prevent infestations by large round worm {Ascris suum) , small brown stomach worm {Hyostrongylus rubidus) , nodule worm (Oesophagostomum spp) , stomach worm (Ascarops strongylina) , intestinal thread worm (Strongyloides ransomi) , kidney worms (Stephanurus dentatus) , lung worms (Metastrongylus spp) , lice {Haematopinus suis) and mange mites (Sarcoptes scabiel var. suis) in or on pigs. When the macrocyclic lactone is ivermectin, the methods of the present invention can, for example, be used to treat or prevent infestations by round worm (Ascaridia galli) , caecal worm (Heterakis gallinae) , hairworm (Capillaria

spp.), lice (Manacanthus stramineus; Menocan gallinae L.) and mites (Acarina spp.) in or on poultry. The methods of the present invention can be used to treat or prevent infestations by these or similar parasites in or on other animals.

The animal may be any mammal or bird. The animal may, for example, be a companion animal such as a dog or cat, 'a domestic animal such as a horse, pony, mule, llama, alpaca, pig, cow or sheep, or a zoo animal such as a primate, felid, canid, bovid or ungulate. In some embodiments, the animal is a pig, camel, deer, cow, sheep, goat, antelope, llama, alpaca, monkey, horse, donkey, mule, mouse, rat, rabbit, guinea pig or buffalo. In some embodiments, the animal is a chicken, turkey, guineafowl , duck or goose .

In the methods of the present invention, the macrocyclic lactone is present in the aqueous formulation at a concentration such that when the aqueous formulation is drunk by the animal, the animal consumes a parasiticidally effective amount of the macrocyclic lactone.

As used herein, by a "parasiticidally effective amount" it is meant an amount effective to reduce the number of parasites in or on an animal or to prevent an infestation by a parasite in or on an animal. As used herein, the phrase "infestation by a parasite" includes a single parasite, that is, an animal has an infestation by a parasite if one or more individuals of that parasite species are present in or on the animal .

The parasiticidally effective amount of a macrocyclic lactone will vary with factors such as the type of animal treated, the particular parasite, the extent of the parasitic infestation, the age, weight and condition of the animal, the particular macrocyclic lactone used, and

the duration of treatment. A parasiticidally effective amount of a macrocyclic lactone would readily be able to be determined by a veterinarian. A parasiticidally effective amount of a macrocyclic lactone may, for example, be determined by reference to conventional doses of the macrocyclic lactone used for the prevention or treatment of infestations by the parasite when the macrocyclic lactone is administered by another means, e.g. when administered as an oral drench.

A parasiticidally effective amount of ivermectin for the treatment of infestations by large round worm {Ascaris suum) , small brown stomach worm {Hyostrongylus ruJbidus) , nodule worm {Oesophagostomum spp) , stomach worm {Ascarops strongylina) , intestinal thread worm {Strongyloides ransomi) , kidney worms (Stephanurus dentatus) , lung worms {Metastrongylus spp) , lice (Haematopinus suis) or mange mites {Sarcoptes scabiel var. suis) in or on pigs is between about 100 μg and about 300 μg per kg liveweight per day.

For the prevention or treatment of an infestation by worms, mites or lice, in or on sheep or cattle, a parasiticidally effective amount of ivermectin may be about 200 μg/kg liveweight per day.

Typically, the aqueous formulation comprising the macrocyclic lactone is a dilute solution of the macrocyclic lactone.

The concentration of the macrocyclic lactone in the aqueous formulation is typically less than 10,000 μg/L. In some embodiments, the concentration is from 500 to 2,500 μg/L. In some embodiments, the concentration is less than 2,000 μg/L.

Typically, the animal is allowed to drink the aqueous

formulation over an extended period by making the aqueous formulation accessible to the animal for drinking, and leaving the animal in the presence of the aqueous formulation for the extended period under conditions such that the animal drinks the aqueous formulation.

Typically, the aqueous formulation comprising the macrocyclic lactone is the only source of water available to the animal throughout the extended period. However, in some embodiments, other sources of water may be available to the animal at the same time as the aqueous formulation comprising the macrocyclic lactone or at different times during the period of treatment, for example, at different times of the day.

Typically the methods of the present invention are used to treat multiple animals simultaneously, eg a herd of pigs.

An advantage of the methods of the present invention is that they can be used to treat or prevent an infestation by a parasite in or on an animal with less handling of the animal than treatment regimens that involve the administration of a drench or an injection. The administration of a drench or an injection to an animal can be stressful for the animal, which may reduce weight gain by the animal. For larger animals such as pigs, injecting the animal can also be stressful and dangerous for the animal handler. Further, administration of the macrocyclic lactone via the animal's drinking water over an extended period can be more effective in treating persistent parasites than treatment regimens involving the administration a single dose of the macrocyclic lactone.

An advantage of the methods of the present invention compared to administering the macrocyclic lactone, or other parasiticidal agents, in an in-feed medication mixed with the animal's feed is that the methods of the present

invention allow for more accurate dosing as sick animals may not eat as much as a healthy animal but typically continue to drink. Further, by administering the macrocyclic lactone in the drinking water over an extended period, any short term fluctuations in water consumption by an animal will have little effect on the total dosage consumed by the animal over the extended period, minimising variations in the total dosage consumed by different animals in a herd of animals being treated by the method of the present invention.

The administration of a macrocyclic lactone in the water drunk by an animal further allows for more rapid commencement and cessation of administration of the macrocyclic lactone to a herd of animals than treatment using an in-feed medication, allowing the manager of the animals to respond quickly to changing circumstances. A macrocyclic lactone can typically be quickly included in the drinking water for a herd of animals, and the inclusion of the macrocyclic lactone in the drinking water can also be quickly stopped. In contrast, when an in-feed medication is used to treat a herd of animals, it is typically not economically viable to cease treatment by removing any uneaten feed that has been mixed with the in- feed medication and the feed mixed with the in-feed medication therefore typically remains available to the animals until all the feed has been consumed.

Typically the aqueous formulation comprising the macrocyclic lactone is prepared shortly before the aqueous formulation is provided to the animal for drinking.

Typically the aqueous formulation comprising the macrocyclic lactone is prepared by mixing a formulation comprising the macrocyclic lactone (referred to below as "the concentrated formulation") with water to form the aqueous formulation. The concentrated formulation may,

for example, comprise one or more macrocyclic lactones, one or more solvents, one or more preservatives, one or more buffers and water. The concentrated formulation may also comprise other components such as flavours (e.g. sucrose, lactose, artificial sweeteners such as saccharine, salt or yeasty extracts) or colouring agents (e.g. food grade dyes) .

Accordingly, in some embodiments, the method of the first aspect of the present invention comprises mixing a formulation comprising: one or more macrocyclic lactones; one or more so-solvents; one or more preservatives; one or more buffers; and water, with water, providing the resultant aqueous formulation to the animal and allowing the animal to drink the aqueous formulation over an extended period.

The concentrated formulation may, for example, contain the constituents referred to in Table 1 in the amounts referred to in Table 1.

Table 1

The co-solvent or co-solvents solubilise the macrocyclic lactone in the formulation and assist in maintaining the macrocyclic lactone in solution when the concentrated formulation is mixed with water. Suitable co-solvents

include propylene glycol, a mixture of propylene glycol and Ecoteric T80/Tween 80, a mixture of propylene glycol and propyl alcohol, or a mixture of propylene glycol and glycol formal. Other suitable co-solvents include vegetable oils, myglyol 840 and mineral oils. A mixture of different co-solvents may be used.

The preservative or preservatives act to preserve the macrocyclic lactone during storage of the concentrated formulation and after the concentrated formulation has been mixed with water. Any preservative soluble in the concentrated formulation may be used. Suitable preservatives include benzyl alcohol, methyl paraben and propyl paraben .

The buffer or buffers maintain the pH of the concentrated formulation during storage of the concentrated formulation. The buffers are typically selected to maintain the pH of the concentrated formulation at about 5.5 to 7.5.

It has been found that formulations comprising: one or more macrocyclic lactones; one or more so-solvents ; one or more preservatives; one or more buffers; and water, can be prepared comprising 0.1 to 100 g/L of the macrocyclic lactone (s). Advantageously, these formulations comprise water as a solvent. Water is a relatively cheap solvent compared to the solvents used in some prior art formulations containing a macrocyclic lactone at a similar concentration. It has also been found that such formulations, containing water as a solvent, can be prepared which are stable during storage for many months. Without wishing to be bound by theory, it is believed that the presence of the preservative (s)

and the buffer (s) in the formulation stabilise the macrocyclic lactone in the formulation.

An example of a concentrated formulation is the formulation set out in Table 2. This concentrated formulation consists of the constituents referred to in Table 2 in the amounts referred to in Table 2. The concentrated formulation set out in Table 2 may be mixed with water to form an aqueous formulation comprising ivermectin for use in the treatment or prevention of an infestation by a parasite such as large round worm {Ascaris suum) , small brown stomach worm (Hyostrongylus rubidus) , nodule worm (Oesophagostomum spp) , stomach worm {Ascarops strongylina) , intestinal thread worm {Strongyloides ransomi) , kidney worms {Stephanurus dentatus) , lung worms (Metastrongylus spp) , lice (Haematopinus suis) or mange mites (Sarcoptes scabiel var. suis) , in or on pigs in accordance with the method of the present invention.

Table 2

The formulation set out in Table 2 is a micellar solution containing the ivermectin in solution.

When the formulation set out in Table 2 is mixed with water to form an aqueous formulation comprising less than about 10,000 μg/L of ivermectin, the ivermectin remains in solution in the aqueous formulation due to the low concentration of ivermectin in the aqueous formulation.

In the methods of the present invention, the macrocyclic lactone is present in the aqueous formulation at a concentration sufficient to treat or prevent an infestation by a parasite in or on an animal (i.e. a concentration sufficient to provide a parasiticidally effective amount of the macrocyclic lactone) when the aqueous formulation is drunk by the animal over an extended period. The concentration required to provide a parasiticidally effective amount of the macrocyclic lactone will vary with the weight of the animal and the water consumption of the animal.

The typical weight range, typical daily water consumption and suitable concentrations of ivermectin in the animal's drinking water to provide a dose of about 100 μg of ivermectin per kg liveweight per day for various classes of pigs are set out in Table 3.

Table 3

When the concentrated formulation set out in Table 2 is mixed with water to form an aqueous formulation comprising ivermectin for use in the treatment or prevention of an infestation by a parasite in or on pigs, the concentrated formulation is typically mixed with water in an amount to form an aqueous formulation containing a concentration of ivermectin sufficient to provide about 100 μg of ivermectin per kg liveweight per day when the aqueous formulation is drunk by the pigs.

The aqueous formulation is typically provided to the pigs for drinking for a period of from about 7 to 14 days, however, depending on the nature of the parasite being treated, this period can be extended. The concentration of ivermectin in the aqueous formulation is typically within the ranges set out in Table 3. Typically, the concentrated formulation is mixed with water to form the aqueous formulation shortly before the aqueous formulation is drunk by the pigs. Typically the aqueous formulation is drunk by the pigs within less than a day after the concentrated formulation is mixed with water to form the aqueous formulation. However, it has been surprisingly found that when the concentrated formulation set out in Table 2 is mixed with water to form a solution containing less than about 10,000 μg/L of ivermectin, the ivermectin

remains stable in the water for more than 28 days at room temperature (i.e. about 30 ⁰ C).

An advantage of the methods of the present invention using the concentrated formulation set out in Table 2 to form the aqueous formulation comprising the macrocyclic lactone is that when the concentrated formulation is mixed with water to form an aqueous formulation comprising ivermectin in an amount of less than about 10,000 μg/L, the ivermectin is in solution in the water. As a result, when the aqueous formulation is consumed by a pig, the ivermectin is in a form that can be readily absorbed by the pig. In contrast, when feed mixed with an in-feed medication containing ivermectin is consumed by a pig the ivermectin needs to be dissolved before it can be absorbed by the pig.

The aqueous formulation comprising the macrocyclic lactone is provided to the animal (s) for drinking over an extended period of time. If the aqueous formulation comprising the macrocyclic lactone is the only source of water available to the animal (s) , providing the aqueous formulation to the animal (s) over ^' an extended period advantageously minimises the effects of any fluctuations in day to day water consumption (for example due to changes in temperature) on the total dose of the macrocyclic lactone consumed by the animal (s) over the treatment period compared to shorter treatment periods. However, in some embodiments, the aqueous formulation may be provided to the animal (s) in a manner that results in the animal (s) consuming a predetermined amount of the macrocyclic lactone per day, irrespective of any fluctuation in water consumption from day to day. This may be achieved by determining the minimum volume of water that will be consumed by the animal (s) in a day, preparing an aqueous formulation having a concentration of the macrocyclic lactone such that when that volume of the aqueous formulation is drunk

by the animal (s) they will have consumed the predetermined amount of the macrocyclic lactone, supplying the aqueous formulation to the animal (s) until that volume of the aqueous formulation has been consumed, and then supplying water not containing the macrocyclic lactone for the remainder of the day. For example, the aqueous formulation comprising the macrocyclic lactone may be supplied to the animal (s) using a large gravity feed medication tank which will be drunk until empty, and then non-medicated water supply would commence for the remainder of the day. This method may advantageously reduce the overall cost of the treatment program by ensuring that the animals are not over-dosed with the macrocyclic lactone.

In some embodiments of the methods of the present invention, the aqueous formulation comprising the macrocyclic lactone is prepared by mixing a concentrated solution of the macrocyclic lactone with water using a proportionating pump, such as those sold under the trade mark DOSATRON (manufactured by DOSATRON INTERNATIONAL, RUE PASCAL, B. P. 6, 33370 TRESSES, BORDEAUX, FRANCE) . Such pumps are currently used for medicating drinking water with products such as vitamins, electrolytes, and nutritional supplements. These pumps are installed in the water supply line, and operate without electricity, using water pressure as the power source. The water pressure activates the injector, which takes up a percentage of the concentrated solution of the product to be mixed with the water from a stock solution container. Inside the injector, the concentrate is mixed with the water, and the water pressure forces the solution downstream. The amount of concentrate is directly proportional to the volume of water entering the injector, regardless of variations in flow or pressure which may occur.

EXAMPLES

Example 1 - Comparison of the method of the present invention and an in-feed control program

Trials were carried out to compare the efficacy of administering ivermectin in the drinking water of pigs over an extended period with an in-feed treatment regimen in inhibiting intestinal parasitism due to Ascaris suum in pigs.

Two separate sites were used in the trials, each site having several rows of pig sheds, allowing side by side treatment groups . Five sheds were used for each treatment group in the trial, each shed holding approximately 400 pigs from 8 weeks old until slaughter age at 22 weeks old. At each site, two treatment groups were established; the "Ivermectin treatment group" (treatment group (A) ) and the "Morantel in-feed treatment group" (treatment group (B) ) .

Treatment group (A) was administered ivermectin in the pigs' drinking water at a dosage of 100 μg/kg liveweight/day for 7 days ending 7 days prior to slaughter. The pigs had free access to the medicated drinking water and free access to feed throughout this 7 day period. At other times during the trial, the pigs had free access to unmedicated drinking water and free access to food.

Treatment group (B) was treated with the commercial product sold under the name "Wormtec" by Morantel in admixture with the pigs' feed. The product was mixed with the pigs' feed in accordance with the directions on the label for the product . The label states that the product contains 3O g morantel citrate per kg. The product was mixed with the feed at 1 kg per tonne of finished feed. The pigs had free access to the medicated feed until all

this feed had been consumed (all the medicated feed was consumed before 7 days before slaughter) . Prior to commencement of the administration of the medicated feed and after all the medicated feed had been consumed, the pigs had free access to unmedicated feed. Throughout the trial, the pigs had free access to drinking water.

Measurements were conducted for treatment groups (A) and (B) of the total mortality within an entering population of grower pigs until slaughter, average daily weight gains in the grower-to-finisher period, numbers of intestines infected with adult worms at slaughter and number of livers affected with "milk spots" . An evaluation of the occurrence of intestinal parasitism and other conditions was made on the basis of typical macroscopic findings at autopsy and at slaughter of all trial pigs.

As the results set out in Table 4 below show, of the 1,920 pigs in treatment group (A) , none had detectable ascarid infection in their small intestines. Of the 1,980 pigs in treatment group (B), 583 (30.7%) had detectable ascarid infections in their small intestines. The numbers of livers affected with noticeable "milk spots" was 46 to 51% in each group. The growth rates and mortality rates among pigs in each group were similar.

Table 4

These results demonstrate that administering ivermectin to the pigs via their water supply was more effective in inhibiting ascarid development in the later intestinal stages of development than the commercially available in- feed treatment .

Example 2 - Comparison of the method of the present invention with control, in-feed and injection treatment regimens

Forty eight young (2-9 months of age) pigs were selected on the basis of confirmed positive individual strongyle faecal egg counts.

The trial pigs were relocated to individual pens and introduced to a fully fed ration and water in individual drinkers. Pens were raised with metal mesh floors and were vigorously cleaned at least once daily (using a high pressure water hose) to prevent any further infections occurring post relocation. Individual daily water consumption and feed intake were monitored from day -7 to day 0 to confirm normal water intake and feed intake and to assist with dose calculations. Individual faecal

samples were collected between day -3 and -1 (inclusive) , and individual strongyle faecal egg counts performed (along with a single bulk coproculture for larval differentiation) . On day -1 or 0, trial pigs were ranked (from highest to lowest) on individual strongyle faecal egg counts, sequentially blocked (into fours) and randomly allocated from within each block to four treatment groups, each of twelve pigs. Allocation was such that each group had a similar group mean strongyle faecal egg count and range of egg counts within the group.

All pigs were weighed on day 0 (using electronic stock scales which were validated before and after use) .

Trial pigs in Group 2 were treated with the test formulation (the formulation set out on Table 2) for seven days in their drinking water to provide a dosage of ivermectin of 100 μg/kg liveweight/day . Medication was mixed up and supplied once daily. Water plus medication was supplied in individual drinkers and individual daily water intake assessment (Group 2 only) continued from day 0 to 6 inclusive, to determine actual administered dose rates .

Pigs in Group 3 commenced treatment with a registered ivermectin-based in feed medication (Ivomec Premix for Pigs ^® ) , at 100 μg/kg in feed. Medication was mixed up according to label directions in the pigs' feed and supplied once daily from day 0 to day 6 inclusive. Medicated feed was supplied in individual feeders and individual daily feed intake (Group 3 only) continued from day 0 to day 6 inclusive, to determine actual administered dose rates.

Pigs in Group 4 were treated once on day 0 (via subcutaneous injection) with Ivomec Antiparasitic

Injection for Pigs ^® according to day 0 bodyweight, at the label dose rate (300 μg/kg) .

Pigs in Group 1 were retained untreated as negative controls.

The treatment details are summarised in Table 5.

Individual faecal samples were collected from all trial pigs on day 10 (4 days after the conclusion of water medication) and on day 17 (10 days after the conclusion of water and in-feed medication) and individual strongyle faecal egg counts and group bulk coprocultures for larval differentiation performed. The average number of eggs from Strongylus species, Trichostrongylus species, Ascaris species, and Metastrongylus species in the faecal samples collected on day 17 for each treatment group are set out in Table 6.

Table 5

Table 6

Example 3 - Stability of ivermectin formulation

A formulation having the components set out in Table 6 below was prepared for stability testing.

Table 6

Material Name Concentrate

Ivermectin 92.87% w/w cone, 10.77 g/L

Ecoteric T80 / Tween 80 100.00g/L

Propylene Glycol USP 160.00 g/L

Benzyl Alcohol BP 30.00 g/L

Sodium Phosphate Anhydrous 9.90 g/L

Monohydrate

Sodium Phosphate Diabasic 1.10 g/L

Anhydrous

Butylated Hydroxy Toluene 2.00 g/L

R. O. Water 7183.22 g/L

TOTAL 1031.99 g/L

Samples were packed in 100 mL white, HDPE containers and placed for stability testing for 24 months in an oven set at a temperature of 30 ⁰ C, and at warehouse conditions.

The HPLC validated analytical method no. PHARMl was used for Ivermectin active ingredient content testing and CIPAC methods for examination of physical parameters.

The results for samples stored over 3, 6, 12 and 24 months are shown in Table 7. These results demonstrate that the ivermectin in the formulation described above is stable for a considerable period of time.

Table 7

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.