FIELD OF THE INVENTION

The present invention provides methods and devices for harvesting whole, intact and fragmented parasitic material from infected animals.

BACKGROUND OF THE INVENTION

Animals frequently carry parasitic infections, many of which pose serious health problems. As such, there is a considerable drive to generate effective treatments and/or vaccines for such infections. However, the production of large quantities of medicaments or vaccines often requires equally large (often kilogram) quantities of parasitic material .

Haemonchus contortus is the single most important nematode parasite of sheep and goats in the world. To-date, control has relied on anthelmintic drugs combined with pasture management. However drug resistant Haemonchus are becoming increasingly widespread and the need to find alternative control methods is pressing. Vaccination is one potential solution but there are no commercial vaccines for any gut nematode parasite of any host. One solution to this is to use native antigen harvested from the nematode worm as a vaccine to induce immunity in the host. Furthermore, the problem of obtaining sufficient parasitic antigen is a major bar to successful vaccine production.

While it is possible to process organ and/or tissue material from infected animals by hand, the process is slow and unable to keep pace with modern abattoirs where several thousand animals might be slaughtered in a day.

As such, the inventors have set out to obviate the problems associated with the prior art and to devise methods and devices which could rapidly and easily process organ and/or tissue material from a large number of animals to yield sufficient i quantities of parasitic material for use in the production of medicaments, vaccines and the like.

SUMMARY OF THE INVENTION

The present invention provides an apparatus for harvesting or collecting parasitic material, for example, whole or intact parasitic organisms (or fragments thereof). In particular the invention provides a means of harvesting parasitic material from tissue and/or organ material derived from, for example, animals infected with said parasites.

In particular, the present invention is based on the finding that when tissue and/or organ material from animals infected with a parasite is processed and filtered, the retentate contains parasites, which may readily be harvested therefrom.

As such, a first aspect of this invention provides a method for harvesting parasitic organisms from infected animals, said method comprising the steps of:

(a) processing tissue and/or organ material derived from an animal infected with a parasite;

(b) filtering said processed material;

(c) collecting a retentate and harvesting parasites therefrom.

In a second aspect, the invention provides a device for harvesting parasitic material from infected animals, said device comprising a filter arrangement for receiving processed tissue and/or organ material and a system for collecting retentate, the retentate comprising parasitic material.

While the methods and devices described herein may be used to harvest different parasitic organisms from a range of different tissue/organ types from a variety of different hosts, they are particularly suited to harvesting parasites from organs and/or tissues derived from ungulate species such as, for example, those known as ruminants. One of skill in this field will appreciate that ruminant organisms may include cattle, goats, sheep, giraffes, bison, yak, buffalo, deer, camels and the like.

Ruminant organisms, of the type described above, may carry or be infected by one or more different parasitic species and it should be understood that the methods and devices provided by this invention might be used to harvest any of these.

For example, the methods and devices described herein may be particularly suited to harvesting parasitic nematodes, especially those that colonise or infect the gastrointestinal tract. Although one of skill in this field will be familiar with such organisms, specific examples may include members of the Trichinella, Ancylostoma. Strongylus, Trichostrongylus, Haemonchus, Ostertagia, Ascaris, Toxascaris, Uncinaria, Trichuris, Dirofilaria, Toxocara, Necator, Enterobius, Strongyloides and Wuchereria genera. Examples of species within these genera include, for example, Trichinella spiralis, Ancylostoma caninum, Strongylus vulgaris, Trichostrongylus colubriformis, Haemonchus contortus, Ostertagia ostertagi, Ascaris suum, Toxascaris leonina, Uncinaria stenocephala, Trichuris vulpis, Dirofilaria immitis, Toxocara spp, Necator americanus, Ancylostoma duodenale, Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularus, Strongyloides stercoralis and/or Wuchereria bancrofti.

In one embodiment, the methods and/or devices described herein may be particularly suited to harvesting the parasitic nematode, Haemonchus coniortus from ovine hosts such as, for example, lamb or sheep.

Accordingly, one embodiment of this invention provides a method for harvesting Haemonchus contortus from infected ovine subjects, said method comprising the steps of: (a) processing tissue and/or organ material derived from an ovine subject infected with Haemoncus contortus;

(b) filtering said processed material to yield waste matter and a filtrate;

(c) collecting the filtrate and harvesting parasites therefrom.

The inventors have found that using the devices and methods described herein, it is possible to obtain large quantities of parasitic material. In particular, when organ and/or tissue material from ovine subjects infected with Haemoncus contortus is processed using the methods and/or devices described herein, one obtains a high yield of whole, intact and live parasite material. Furthermore, the devices of this invention allow a large amount of infected tissue and/or organ material to be processed at any one time, further increasing the yield of harvested parasitic material.

Methods and processes for obtaining large amounts of live Haemoncus contortus are of particular use when preparing vaccines which often require large amounts of material in order to extract sufficient antigen for successful inoculation. In the case of Haemoncus contortus native antigen vaccines, kilogram quantities of clean adult worm are required - the devices and methods provided by this invention provide a rapid and reliable means of obtains such large quantities of material.

The organ material may comprise whole organs or parts thereof as well as tissue material and the like. For example whole or partial heart, lung, stomach, intestine, pancreas, liver, kidney and/or brain material may be used. Additionally, or alternatively, blood (whole blood or fractions thereof), skin, muscle, connective tissue, epithelial/endothelia tissue may also be used. One of skill will appreciate that this list of suitable organ/tissue material is by no means exhaustive and the exact choice of tissue or organ material will depend on the parasite(s) to be harvested. For example, to harvest parasites colonising or infecting organs or tissues of the gastrointestinal tract (for example the intestines or stomach etc.), it may be necessary to process gastrointestinal material.

By way of example, the parasitic nematode Haemonchus coniortus infects the gastrointestinal system of ruminants (in particular sheep) and adult worms live either attached to the abomasal mucosa or in close assocation with it. As such, in order to harvest these parasites from infected ruminants, in particular sheep, it may be necessary to process abomasa using the device and/or methods provided by this invention.

In one embodiment, the organ or tissue material may be processed by mechanical means to remove, dislodge or separate parasitic material from the organ/tissue material. Where the organ or tissue material further comprises blood or the products of digestion (i.e. gastrointestinal contents) etc., the processing procedures described herein may further separate these substances and any parasites from the organ and/or tissue material. It should be appreciated that while a number of different processing techniques may be used (mechanical or otherwise), advantageously, the techniques dislodge any parasites present in or adhered/associated to/with the organ/tissue material being processed without damaging, or substantially damaging, the parasitic material to be harvested. That is to say, in certain embodiments, the organ/tissue material is processed using techniques that preserve the parasitic material and ensure maximum recovery of whole (intact) parasitic organisms. Furthermore, in order to reduce the amount of organ/tissue material harvested, the selected processing technique may preserve the integrity of said material. In this way contamination of harvested parasitic material with particulate processed organ/tissue material can be minimised. The term "processed" may encompass techniques which wash, agitate, homogenise and/or disrupt the organ/tissue material. Furthermore, it should be understood that organ/tissue material which has been "processed" comprises a waste component comprising organ/tissue material and a "filtrate" component comprising parasitic material.

In one embodiment, the organ/tissue material may be processed by continual agitation and/or washing in a mixing or blending device. Suitable devices for processing organ and/or tissue material may include, for example, those comprising rotating drums into which material to be processed may be placed. The speed at which the drum of such devices rotates may vary but typically speeds of between lrpm and l OOrpm may be suitable. In one embodiment, the drum may rotate at approximately 10rpm-90rpm or in other embodiments at approximately 20rpm to 60rpm. In particular rotational speeds of approximately 3O-5Orpm may be most suitable . One of skill will appreciate that through prolonged rotation, agitation and/or washing, material within the drum may be subject to complete or partial homogenisation and/or disruption resulting in a separation of any parasitic organisms from said material. In a further embodiment, the organ/tissue material may be processed in a mixing or blending device which comprises internal baffles and/or blades to further agitate, wash, disrupt or homogenise the organ/tissue material while rotating.

Advantageously, the mechanical means for processing organ and/or tissue material may be sufficiently large to receive and hold approximately 200 litre volumes of material. Of course, small or indeed larger sizes may be used and typically the mechanical processing devices are capable of receiving and holding at least approximately 50 -100 litres of material. Suitable devices may include, for example food mixing or blending devices and/or concrete/cement mixing devices.

In addition, the inventors have determined that by adjusting the speed and duration of rotation of the devices described above, the amount and quality of the parasite yield may be modulated with longer and/or faster periods of rotation generally increasing yield. Furthermore, parasite yield may be modulated by adjusting the dimensions of any internal baffles. By way of example, to modulate or increase the yield of parasitic material, the size and spacing of the baffles may be increased and/or decreased. Moreover, in order to maximise the yield of whole/intact parasites and reduce contamination of harvested parasites with particulate organ/tissue material, the internal baffles of the processing devices described herein may be padded to reduce the agitation, homogenisation and/or disruption of the organ/tissue material. Additionally or alternatively, the number of baffles may be increased.

As such, in one embodiment, the method provided by this invention comprises a first step in which organ and/or tissue material from animals infected with parasites is mechanically processed to separate, dislodge or remove parasitic material from the organ/tissue material. In a yet further embodiment, the present invention provides methods and devices in which tissue and/or organ material is first processed in a blending or mixing device, such as, for example, a concrete or cement mixer.

Advantageously, the devices provided by this invention may comprise means for processing tissue and/or organ material. For example, mechanical processing devices such as a blending or mixing device of the type described above may be an integral part of the devices described herein.

In one embodiment, large tissue and/or organ material may optionally be cut or opened to facilitate the mechanical processing of the type described herein. This optional step may be particularly useful where the organ or tissue has been derived from the gastrointestinal tract. As such, organs such as the rumen, reticulum, omasum and/or abomasum may first be opened with a knife before being subjected to the processing protocols described above.

In one embodiment, the organ/tissue material may be processed together with a volume of a suitable solution, for example a buffer solution. Suitable solutions may include, for example, water, saline and/or phosphate buffered solutions. The volume of solution added to the tissue/organ material to be processed may vary and may depend on the amount of organ/tissue material being processed. For example, to process a single abomasum from a sheep, a volume of approximately 5L of fluid (for example saline solution) may be added. When large amounts of tissue/organ material are to be processed together (for example two or more abomasa) it may be possible to use less fluid per abomasum. By way of example, processing between 8 and 15 abomasa may require the addition of approximately 20 to 30 litres of a suitable solution. It should be understood that the solution added to the tissue/organ being processed need not be of any specific gravity. For example, it is not necessary to use solutions comprising ethyl alcohol and/or isopropyl alcohol.

Advantageously, the device described herein comprises a filter arrangement for receiving and filtering processed organ/tissue material. In one embodiment, the filter arrangement may comprise first and second filters.

Advantageously, the second filter receives filtrate from the first filter.

Typically, the first filter may be adapted to retain or substantially retain the waste component of the processed organ/tissue material and allow passage of a filtrate which may comprise particulate matter, small portions of organ/tissue material (including for example the products of digestion and blood), fluid and/or parasitic material (for example, whole/intact and/or fragmented parasite). In one embodiment, the first filter may comprise a material having an open mesh, woven or knit construction, defining apertures allowing the passage of the above described filtrate but dimensioned to substantially retain or trap the waste component of the processed organ/tissue material. The first filter may take the form of a sieve and suitable materials for the construction of the filter may include materials such as, for example, fabrics (gauzes/muslin and the like), plastics and/or metals.

In one embodiment, the first filter may comprise a trap, which prevents processed organ/tissue material not correctly received by the first filter or which has not been correctly deposited into the first filter, from contaminating the second filter. The trap may take the form of a shield which contains and/or surrounds the first filter. In one embodiment, the first filter comprises a trap which houses or surrounds a filter or sieve as described above. The filter may take the form of a basket constructed of a rigid, inflexible material (such as metal) and having an open mesh structure defining apertures having widths of approximately 2- 1 Ocm.

One of skill will appreciate that depending on the type of organ/tissue material processed the aperture or pore dimensions defined by the first filter used may vary. For example, the first filter may comprise a material which defines apertures or pores having a width or diameter of imm-lOmm - filters defining apertures or pores with these dimensions may be particularly suitable where the processed organ or tissue material is fluid or semi fluid. In other embodiments the apertures defined by the material of the first filter may be larger having widths or diameters of l cm to 20cm or widths of approximately 2cm- 10cm. In certain embodiments, the apertures or pores defined by the material of the first filter may have widths or diameters of approximately 3cm. In addition, the first filter may be sufficiently large to retain approximately 1 -100 litres of processed organ material - in this way large amounts of processed tissue/organ material can be filtered. Of course, one of skill will appreciate that depending on the volume or amount of processed tissue/organ material, different sizes of first filter could be used. As such, a further embodiment of this invention may provide a device in which the first filter is removable so that it can be easily replaced with smaller or larger first filters.

In a further embodiment, the devices or methods of this invention may incorporate or use a pre-filter adapted to filter processed organ or tissue material before it enters the first filter.

The second filter may be adapted to retain at least a portion or fraction of the filtrate received thereby (i.e. filtrate from the first filter), said portion or fraction comprising parasitic material. The retained fraction may otherwise be referred to as a retentate - the retentate comprising parasitic material. Advantageously, the second filter may comprise a material having an open or mesh, woven or knit construction. Suitable materials may include, for example, fabrics (gauzes/muslin and the like), plastics and/or metals. The open or mesh, woven or knit construction of the second filter may define apertures or pores dimensioned to ensure that a proportion (preferably a significant proportion) of the parasitic material contained within the filtrate are retained on, or caught by, said filter. In one embodiment, the open or mesh, knit or woven construction of the second filter defines apertures having a width or diameter of 0.1mm to 10mm, preferably 0.5mm to 9mm, more preferably lmm to 8mm. In one embodiment, the apertures or pores defined by the material of the second filter may be approximately 5mm.

In one embodiment, the second filter may allow passage of, or be porous to, fluid and small particulate matter (such as for example particulate or small organ/tissue material or gastrointestinal contents), but may substantially retain parasitic material present in the filtrate from the first filter. The second filter may be positioned so as to be located directly underneath the first filter and in one embodiment, filtrate from the first filter may be directed on to said second filter by means of a chute or channel. In one embodiment, the chute or channel may direct the filtrate to flow on to the second filter at an angle (preferably an acute angle). This is particularly advantageous where the parasitic material to be harvested is verminous (i.e. thread like) and may further improve the harvest yield by reducing the amount of parasite that could pass through apertures and/or pores defined by the material/construction of the second filter.

The second filter may take the form of a continuous loop of material and in one embodiment, the continuous loop of material is moveable and may move or rotate through 360 degrees.

Advantageously, the second filter may comprise a continuous loop, conveyor or belt having a surface for receiving filtrate and a contralateral surface. In one embodiment, the continuous loop, conveyer or belt may have a width of approximately 5-50 cm, preferably 10-40 cm and most typically 10-30 cm.

In one embodiment, the conveyer or belt of the second filter continually moves through 360 degrees and the surface for receiving filtrate continually receives filtrate from the first filter. In this way, the filtrate is not deposited on to a single part of the surface for receiving filtrate of the conveyer but is deposited across a wide area thereof.

Movement or rotation of the second filter may be brought about by one or more rollers, wheels or cogs which engage with a portion of the second filter, for example a portion of the conveyer or belt described above. In one embodiment, the rollers or cogs may engage with the edges or margins of the conveyer or belt of the second filter. Where movement or rotation of the second filter is affected by cogs, the teeth of the cogs may locate in apertures defined by the edges or margins of the conveyer or belt of the second filter. One of skill will appreciate that by rotating at least one of the rollers, wheels or cogs, the second filter may also move.

The device and methods provided by this invention may further comprise or use a system for collecting at least a fraction or portion of the retentate retained by/caught on the second filter. Preferably the collected fraction comprises parasitic material. Said system may comprise a wash apparatus which washes the retentate from the second filter and into a collection vessel. One of skill will appreciate that in order to increase or maximise the yield of parasitic material, a wash apparatus or system may be used. Advantageously, where the second filter comprises a continuously moving conveyer or belt (as described above), the wash system may be positioned so as to wash or recover retentate from the second filter, to a collecting vessel. Additionally, or alternatively, the system for collecting retentate may comprise a pressurised air system for blowing retentate from the second filter, a scraping device (for example a blade which traverses the second filter) which retains retentate and/or scrapes retentate from the surface thereof. Additionally or alternatively, the system may comprise some means of shaking or vibrating the second filter such that retentate is dislodged therefrom.

In other embodiments, the system for collecting retentate may further comprise a fluid reservoir into which at least part of the second filter is submerged. In this way, where the second filter is a moving conveyer and the conveyer passes through the fluid reservoir, retentate on the second filter will dislodge/float off and collect in the reservoir. The system for collecting filtrate may comprise one or more of the abovementioned systems.

In one embodiment, and where the second filter takes the form of a continuous looped belt or conveyer, filtrate from the first filter (which comprises parasitic material) is continually received by the second filter as described above and the retentate of the second filter transported or conveyed to the system for collecting retentate.

Advantageously, the system for collecting retentate from the second filter may comprise a wash system positioned to direct fluid to the contralateral surface of said looped belt or conveyor. In this way, retentate is easily and effectively washed into a collecting vessel. Advantageously, fluid from the wash system and washed retentate is caught by, or collected in, a collecting vessel.

In one embodiment, the collecting vessel may take the form of a large bucket or basin positioned to catch (washed) retentate from the second filter. Where the system for collecting at least a fraction of the filtrate comprises a washing system, the collecting vessels may collect fluid expelled by the washing system together with at least some of the retentate.

When in use, the collecting vessels may become full and/or heavy with fluid and as such are difficult to manoeuvre. In one embodiment, the collecting vessels may be mounted on platforms dimensioned to allow the user to easily move vessels into position under the wash system described above. Advantageously, the platforms may hold the collecting vessels at approximately waist height or between 50-80cm above ground level. In a further embodiment, the platform may comprise rollers or wheels to further facilitate movement of the collecting vessels. The inventors have discovered that gravity (or preferential floatation) separation techniques may be used in order to extract parasitic material from the collecting vessels. The principle of gravity (or floatation) separation is based on the finding that in solution (for example the wash solution collected in a collecting vessel) certain fractions of the retentate washed from the second filter float and others sink. The fractions that sink may include parasitic material. In addition, the inventors have discovered that parasitic material may further separate from other sinking debris to form a distinct layer in the collecting vessel. As such, the parasitic material can easily be harvested from the collecting vessel.

To facilitate harvesting of the parasitic material and to increase the separation of parasitic material from other debris in the collecting vessel, the collecting vessel may be tilted. In this way much of the fluid and floating debris is decanted from the collecting vessel and the more dense, sinking debris, separates at the lowermost point of the vessel. In use, the parasitic material may separate from other organ/tissue debris to form a distinct layer which may easily be removed by hand using, for example, forceps or the like. Advantageously, the collecting vessel may be gradually tilted either by hand or my some mechanical means. In one embodiment, the collecting vessel may be tilted to an angle of about 80 degrees.

In one embodiment, the platforms for holding or supporting the collecting vessels may further comprise a section which tilts at an angle of between 50 and 90 degrees, relative to the platform surface.

In a third aspect, the present invention provides a device for harvesting parasitic material from infected animals, said device comprising;

a blending or mixing means for processing tissue and/or organ material to yield a filtrate and waste matter, said filtrate comprising parasitic material; a first filter for receiving processed tissue and/or organ material having a mesh, knit or woven construction and defining apertures allowing the passage of the filtrate but not the waste material;

a second filter receiving filtrate from the first filter and having a mesh, woven or knit construction which retains parasitic material present in said filtrate;

a system for collecting said parasitic material from the second filter, comprising a wash apparatus adapted to wash the parasitic material retained by the second filter; and

a collecting vessel for collecting parasitic material washed from the second filter.

In a fourth aspect, the present invention provides the use of a device according the second or third aspects of this invention for harvesting parasitic material from infected animals.

In one embodiment, the device of the third aspect of this invention and device for use in the fourth aspect of this invention are for harvesting Haemoncus contortus from infected ovine tissue and/or organ material.

In one embodiment, the invention provides a method for harvesting Haemonchus contortus, said method comprising the steps of:

(a) processing organ and/or tissue material infected with Haemonchus contortus to yield a filtrate and waste matter;

(b) filtering the processed organ and/or tissue material to remove the waste matter: and

(c) harvesting Haemoncus contortus from the filtrate by gravity and/or floatation separation. In a further embodiment, the invention provides a method for harvesting Haemonchus coniorlus from infected ovine subjects, said method comprising the steps of:

(a) processing tissue and/or organ material derived from an ovine infected with Haemonchus coniorlus to yield a filtrate and waste matter;

(b) passing the processed tissue and/or organ material through a first filter to remove at least some of the waste matter;

(c) passing the filtrate from step (b) through a second filter adapted to retain any Haemonchus coniorlus present in said filtrate;

(d) washing retentate from the second filter and collecting the washed retentate in a vessel; and

(f) harvesting Haemonchus contortus by gravity and/or floatation separation.

The retentate may be washed with water, saline or a buffered solution (for example PBS). The washed retentate together with the washing solution may be collected in a vessel. When full, retentate collected in the vessel may be allowed to settle. In such conditions, the inventors have noted that any Haemonchus coniorlus material will sink to form a distinct layer at the bottom of the collecting vessel whereas any waste material - most of which will float.

It should be understood that the devices and/or methods described herein may be automated and/or continuous processes which quickly and continuously process large amounts of organ/tissue material and consequently yield large quantities of harvested parasitic material. Moreover, the methods and/or devices can be operated at a speed which keeps pace with the rate at which an abattoir process animals (sheep) - abattoir processing rates may approach 500 animals an hour. In one embodiment, the processing means may continually deposit processed organ/tissue material into the filter arrangement of the devices described herein and the system for collecting retentate may be continually operable to recover retentate from the filter arrangement. DEATAILED DESCRIPTION

The present invention will now be described in detail with reference to the following Figures which show:

Figure 1 provides an image of a device according to the second aspect of this invention.

Figure 2 is an elevation of the side of a device according to one embodiment of the second aspect of this invention.

Figure 3 is a perspective view of the device shown in Figure 2.

Figure 4 is a perspective view of the device shown in Figures 2 and 3.

Figure 5 is an image of part of a device according to one embodiment of the second aspect of this invention.

Figure 6 is an image of a further part of a device according to one embodiment of the second aspect of this invention.

Figure 7 is an end elevation of the device shown in Figures 2, 3 and 4.

Figure 8 is a plan of the device shown in Figures 2, 3, 4 and 5.

Figure 9 shows the volume of worms recovered or harvested from 7 individual sheep by a device according to this invention.

Figure 10 is a process diagram showing the steps of a method for harvesting parasites from infected animals according to the first aspect of this invention.

Figure 1 shows a device designated reference numeral 10, for harvesting parasitic material from infected animals according to the second aspect of this invention. Device 10 comprises a filter arrangement 2 for receiving processed tissue and/or organ material and a system 4 for collecting at least a fraction of the filtrate from said filter arrangement 2.

In this embodiment, device 10 further comprises mechanical processing means 6 for processing organ/tissue material. Here, the mechanical processing means 6 takes the form of a cement mixer having a rotating drum 8 and internal baffles (not shown).

In use, organ/tissue material to be processed is placed into the mechanical processing means 6 which, through rotation of the drum 8 and the action of the internal baffles (not shown) agitates the organ/tissue material for a set period of time. It should be understood that the organ/tissue material might be processed in the mechanical processing means 6 together with a volume of fluid. The processing procedure separates parasitic material from the organ/tissue material and yields a filtrate which comprises parasitic material and a waste component which comprises organ/tissue material.

The filter arrangement 2 receives processed organ/tissue material and comprises a first filter 2a and a second filter 2b. In use, processed organ/tissue material is deposited into first filter 2a. Filter 2a to comprises a trap 2c and a filtration basket 2d. In use, the processed organ/tissue material is deposited into the filtration basket 2d of the first filter 2a. Filtration basket 2d comprises a rigid inflexible material such as metal and has an open mesh construction defining apertures having widths of approximately 3cm. As such, the mesh structure of filtration basket 2d retains the waste component of the processed organ/tissue material and allows passage of the filtrate. In use, trap 2c of device 10, catches processed organ/tissue material not correctly deposited into filtration basket 2d. In this way, contamination of the second filter 2b with unfiltered processed organ/tissue material is avoided. Filtrate from first filter 2a is received by second filter 2b. In this embodiment, filter 2b takes the form of a moving belt or conveyer 2e having a surface for receiving filtrate 2f. Filtrate from first filter 2a is directed on to the surface for receiving filtrate 2f of the conveyer 2e by angled chute 3.

The conveyer 2e of second filter 2b moves and rotates through 360 degrees.

Rotation of the conveyer 2e is brought about by a plurality of cogs 12. In this embodiment, the cogs 12 engage the edges or margins of conveyer 2e and via the motorised rotation of at least some of the cogs 12, the conveyer 2e is driven to rotate through 360 degrees.

In this embodiment, chute 3 deposits filtrate on to the moving surface for receiving filtrate 2f of conveyer 2e. Conveyer 2e comprises an open mesh construction and the fluid component of the filtrate from the first filter 2a, passes through the mesh structure of conveyer 2e and is caught in a waste bucket (not shown). In contrast, parasitic material within the filtrate is caught by, or retained on, the surface for receiving filtrate 2f of conveyer 2e.

The conveyer 2e of the second filter 2b, transports or conveys retentate (which comprises parasitic material) to the collecting system 4. In this embodiment, collecting system 4 is a wash system which directs fluid to the surface 2g contralateral to the surface for receiving filtrate 2f of the conveyer 2e. In use, wash system 4, washes parasitic material caught on or retained by the surface for receiving filtrate 2f of the conveyer 2e into a collecting vessel best shown in Figure 4.

Reference is now made to Figure 2 which is an elevation of the side of a further embodiment of a device according to the second aspect of this invention and generally designated reference numeral 20. Here, the mechanical processing means again takes the form of a cement mixer and for convenience has been designated reference numeral 6 as in Figure 1. In this embodiment, the mechanical processing means 6 is placed to the side of the device 20. Best shown in this Figure is the placement of a waste bucket 16, into which the waste component of the processed organ/tissue material retained by filter 2a may be placed.

Figure 3 clearly shows the first filter of device 20; again, for convenience, the first filter has been designated reference numeral 2a and in this embodiment comprises trap 2c and filter 2d. Here, filter 2d comprises a mesh panel 18a which allows passage of a filtrate (including any parasitic material) and some processed organ/tissue material, but retains larger waste processed organ/tissue material.

Filter 2d is fixed to the trap 2c of first filter 2a via hinges 19 which allow filter

2d to be lifted out from trap 2c and waste material caught or retained thereon scraped or removed to waste bucket 16.

Reference is now made to Figure 4 which best shows the collecting vessels 22 which collect fluid from wash system 4 and parasitic material washed from second filter 2b. In this embodiment, the collecting vessels 22 take the form of large trays. Collecting vessels 22 are placed beneath the system 4 for collecting retentate and are placed on a platform 24 which is conveniently dimensioned to allow the user to easily and quickly manoeuvre the collecting vessels. One will appreciate that when device 20 is in use, collecting vessels 22 becomes heavy with fluid and to facilitate their movement, platform 24 comprises rollers 25. In this way collecting vessels 22 may easily be located under the system 4 to permit collection of parasitic material and, when full of fluid, quickly moved away from system 4 so as to allow placement of another collecting vessel 22 under the system 4.

Once full of fluid, the collecting vessels 22 are moved to a tilting platform 28, best shown in Figure 5. Tilting platform 28 comprises a retaining bar 30 such that when the platform is tilted about hinges 32, the collecting vessel remains on platform 28 and does not fall off. In this way, as the tilting platform 28 is tilted, a substantial volume of the fluid and floating debris collected in the collecting vessel 22 is decanted therefrom. Furthermore, the inventors have discovered that when tilting platform 28 tilts the collecting vessel to an angle of about 80 degrees (relative to platform 28), the dense material which has sunk to the bottom of collecting vessel 22 separates to yield a layer substantially comprising parasitic material and which may easily be harvested with the use of forceps or the like.

Wash system 4 is clearly shown in Figure 6. In this embodiment, the wash system comprises a hose 4a which is connected to a pressurised water source - for example the mains water supply. Valve or tap 4b controls the supply of water to nozzles 4d which are connected to valve/tap 4b via two secondary pipes 4c. When valve/tap 4b is opened, nozzles 4d direct a pressurised spray of water to the contralteral surface 2g of the conveyer 2e of second filter 2b. In this way, retentate caught on or retained by second filter 2b (the retentate comprising parasitic material) is washed into collecting vessels 22. Also shown here are cogs 12 which engage with the second filter 2b and which through rotation, cause the conveyer 2e of second filter 2b to continually move through the spray from nozzles 4d.

Reference is now made to Figure 7 which best shows the mechanical processing means 6. Here, the mechanical processing means is a cement mixer having a drum 8 and is mounted on a platform 32. In this embodiment, platform 32 is dimensioned to locate the cement mixer above first filter 2a and at a position which, when the drum 8 is tilted downwards, allows the contents of the drum 8 (for example processed organ/tissue material) to be deposited into first filter 2a and in particular the filtration basket 2d thereof (not shown in this figure). Figure 8 provides a plan view of the device 20 and clearly shows the mechanical processing means 6. the filter arrangement 2, including first filter 2a and second filter 2b. Also shown is the mesh panel 18a of filter 2d located within the trap portion 2c of the first filter 2a and waste bucket 16 into which a component of the waste processed organ/tissue material retained or caught by filter 2d may be scraped or deposited.

Also shown is the conveyer 2e of filter 2b and the surface for receiving filtrate 2f thereof. In this embodiment, the belt is approximately 30cm wide and has edges 2h engaging with a number of cog elements 12, some of which are motorised to bring about movement of the conveyer 2e.

Figure 8 also shows platform 24 and rollers 25 upon which collecting vessels 22 are placed.

Figure 9 shows the volume of worms which can be recovered from 7 individual sheep by a device provided by this invention and shown in Figures 1 -6 above.

Referring to Figure 10, there is shown the steps of a method for harvesting parasites from infected animals according to the first aspect of this invention. The method has been designated reference numeral 30 and comprises steps designated 32, 34, 36, 38 and 40. First step 32 involves obtaining organ/tissue material from animals infected with parasites. In certain embodiments, the infected animals may be lambs or sheep and the parasite they are infected with is Haemonchus comortus. The organ/tissue material comprises gastrointestinal material and in particular abomasa in which the adult Haemonchus parasite lives attached to the mucosa or in close assocation with it.

Prior to step 34, the organs (for example abomasa) to be processed, are first be opened with a knife. In step 34, the organ/tissue material (for example abomasa) collected or obtained in step 32 are processed, typically by mechanical means, to separate parasitic material (Haemonchus contortus material) from the organ/tissue material. Where the method utilises a device provided by this invention, such as the devices shown in Figures 1 -6, the mechanical processing means is a concrete mixer (show in Figures 1 -

6 as reference numeral 6) which processes the organ/tissue material by continual agitation. Processing step 34 yields processed organ/tissue material which comprises a waste component comprising organ/tissue material and a filtrate comprising fluid and parasitic material. To increase the amount of filtrate, the organ/tissue material is combined with a volume of fluid 33 (for example water or a buffer).

Processed organ/tissue material is then filtered as shown in step 36. Again, where the method shown in Figure 8 utilises a device provided by this invention, the filtration of the organ/tissue material is achieved with the use of first and second filters. The first filter retains the waste component of the processed organ/tissue material and allows passage of a filtrate which is received by the second filter. The second filter is adapted to retain parasitic material present in the filtrate but allows passage of fluid and other matter. In this way the retentate from the second filter comprises parasitic material.

Step 38 involves collecting the retentate from the second filter and this is achieved using wash systems to wash the retentate into collecting vessels. Thereafter, parasitic material is harvested from the collected retentate as shown in step 40. The inventors have discovered that in solution, the retentate separates into two components, one component comprising debris which floats and another comprising more dense debris and parasitic matter which sinks. Furthermore, the inventors note that as the sinking dense matter settles, the parasitic matter further separates from the dense sinking debris to form a distinct layer easily harvested using forceps. In addition, the inventors have noted that by tilting collecting trays at angles of about 80 degrees, this separation phenomenon can be enhanced and the harvesting of the parasitic matter is greatly facilitated.

Various improvements and modifications may be made to the above described embodiments without departing from the scope of the invention. For example the second filter 2b may take the form of a rotating wheel having a surface for receiving filtrate from a first filter circumferentially placed about the wheel. In other embodiments, the system for collecting retentate may comprise a pressurised air system which directs air under pressure to the contralateral surface of the conveyer. In this way, rather than being washed from the second filter, the retentate (which comprises parasitic material) may be blown off and collected in a collecting vessel optionally be pre-filled with water. In yet further embodiments, the retentate might be collected by shaking or vibrating the second filter to dislodge retentate caught thereon - again, retentate collected in this way may be collected in vessels optionally filled with water. Other possible means of collecting retentate from the second filter include scraping. For example, a blade or other scraping device may be fixed close to the surface of the conveyer such that as the conveyer moves, retentate caught thereon is retained or scraped from the surface of the conveyer, by the blade or scraping device.

Additionally or alternatively, the part of the conveyer could be submerged in a fluid, for example water held in a container or the like, such that as the conveyer moves with retentate caught or collected thereon, it passes through the fluid and the retentate is dislodged or floats away or from the conveyer. In this way, parasitic material would settle at the bottom of the fluid filled container and could be easily be retrieved. One of skill will appreciate that the system for collecting retentate may comprise one or more of the systems described herein.

Example 1

In order to make a commercial native antigen vaccine from a nematode parasite such as Haemonchus contortus, kilogram quantities of clean adult worms are required. To be optimally cost-effective the parasites are best harvested from fat lambs destined for slaughter in an abattoir. Three weeks before slaughter these sheep will be deliberately infected with a suitable dose of Haemonchus infective larvae.

The optimal dose of larvae will depend to some extent on the isolate of the parasite, but will typically be in the 1000 to 5000 range. An ideal dose is one which yields maximum weight of adult worms without compromising the health of the host in any way.

Twenty-one days after infection has been chosen as the optimal killing time for similar reasons. Haemonchus contortus starts feeding on blood from about 7 days after infection, reaches sexual maturity by about 16 days but does not attain maximum size until about day 28. However, the longer the interval between infection and slaughter, the greater the blood loss caused by the continuously feeding parasites and the more anaemic the sheep becomes. This suggests that it would be preferable to collect immature worms. However, it is difficult to separate 14 day worms from fine debris present in the digesta or from blood clots which accumulate on the mucosa. When an ovine abomasum containing 21 day old Haemonchus is opened and the contents tipped out, about half the parasites are found in the contents and half remain adherent to the mucosa. Adherent worms can be readily removed by immersing the abomasum in a basin of warm saline and rubbing the mucosa by hand to remove the parasites.

Clean worms can also be recovered from the abomasal contents by gently sieving. Day 21 Haemonchus males are approximately 1.0 to 1.5 cm long while females measure 1.5 - 2.0 cm. They are almost entirely retained by meshes with a pore of 5mm or less. Below this pore diameter, the amount of contaminating digesta increases.

While this manual method is perfectly adequate for small scale worm harvesting, it would not cope with the pace of a modern abattoir where several thousand sheep can be slaughtered in a day. The objective was to devise an apparatus which could 1 ) dislodge the adherent worms and 2) separate both these and those in the contents from most of the digesta. Both processes would have to be achieved rapidly to match the pace the abattoir e.g 500 abomasa per hour.

A partially mechanised process for rapidly harvesting clean adult Haemonchus from sheep

Each abomasum is manually opened longitudinally with a knife over a 1 OL bucket. The opened abomasum is added to the contents in the bucket and 5 L of warm water poured in. The contents of the bucket are then tipped into the worm harvesting apparatus

The worm harvesting apparatus

This consists of three separate elements :

A) a cement mixer for dislodging worms adherent to the mucosa

B) a sieving conveyor which separates most of the digesta from the parasites and deposits them in a tray and

C) a tray decanting module which further separates worms and debris Clean worms are then harvested manually from the trays into 50ml tubes containing phosphate buffered saline and stored frozen.

(A) The cement mixer

A small electric cement mixer was used to dislodge adherent Haemonchus from the abomasal mucosa.

The particular model had an 8OL capacity drum which rotated at 30 rpm. It was fitted with two metal baffles inside the drum. The abomasa of 6 sheep, which 21 days earlier had been infected with 10,000 larvae each, were individually processed in the mixer in an attempt to optimise some of the variables which might affect the degree of worm removal. This was assessed by carefully inspecting the mucosal surface of each abomasum after it had been through the mixer to determine whether any worms remained adherent.

Variables tested included :-

1 ) The size of the gap between the baffles and the drum

2) The rotation time 3) The volume of saline added to the mixer

4) Whether the abomasum was processed alone or with its contents

Following experimentation with several Haemonchus infected abomasums it was concluded that:-

1 ) Reducing the gap between the baffles and the drum from 60 to 5 mm with layers of pipe insulation foam rubber greatly increased the degree of agitation because the abomasa were lifted and dropped by each baffle as it passed through the fluid in the mixer. The soft foam lining also reduced the possibility of the abomasa being chopped up by the baffles.

2) Once the baffles were padded, a rotation time of one minute was adequate to remove all the worms from the mucosa.

3) 5L was an adequate volume of saline to remove all the worms from a single abomasum

4) It appeared from a single sheep that processing contents and abomasums together had no effect on worm recovery an observation confirmed in later experiments

(B) The sieving conveyor

Two prototypes were evaluated both of which worked on the same principle Both consisted of a length of plastic mesh (n x nmm) about 20cm wide arranged in a continuous moving loop. The contents of the cement mixer were directed to flow slowly onto this moving mesh. Most of the digesta would pass straight through whereas most of the worms were retained. The retained worms (and some coarser debris) were subsequently back washed from the mesh with a high pressure spray of warm water and collected into trays which were slowly decanted to enable further separation of worms and debris. Initially this decantation was done manually - later a mechanical tray tipper was used for this procedure. Prototype 1.

After agitation in the cement mixer for a minute, the contents were tipped into a 5OL container from which they flowed onto a plastic mesh which was attached to the circumference of a vertically mounted bicycle wheel. The wheel rotated at about 2 rpm and the flow of abomasa] washings arrived when the mesh was horizontal at the top of the wheel. Most of the debris and fluid flowed straight through the mesh into a small hopper from where it was directed through a fine sieve to waste. This sieve was checked periodically for parasites but none were found.

The mesh bearing the retained material including the parasites moved slowly downwards as the wheel rotated. At the bottom of the cycle, when the mesh was inverted relative to when it was loaded, it was back-washed by a high pressure spray of warm water which dislodged the parasites and any remaining debris into a tray at floor level. This prototype was simple and worked well. However its geometry meant that steps had to be climbed to load the cement mixer and the parasite enriched material was delivered at floor level.

Prototype II was designed to overcome these ergonomic issues as follows: - Prototype Il The wheel in Prototype 1 was replaced by an S-shaped conveyor which collected the parasites and coarse debris from about 50 cm above floor level and delivered them to trays at bench height. The lower starting height meant that the cement mixer could be loaded without climbing steps. As with the first prototype, when the mesh was inverted and horizontal it was back-washed with a high pressure spray of warm water and the parasites and remaining debris were collected into trays.

Nearly all the parasites sink to the bottom of the collecting tray where they usually form clumps. Some of the lighter debris floats on the surface. The trays were then transferred to the tray decanting module.

C) the tray decanting module

Essentially this is a table with a top which can be tilted nearly vertical by a linear actuator. A tray containing mesh back-washings is placed on the surface of the decanting module and then slowly and steadily tipped on one of its edges to about 80 degrees. Water and floating debris are decanted away from the worms at the bottom of the tray. A partial, density dependent separation of the parasites from the residual sinking debris also occurs. Once the tray has been fully tipped most of the parasites can be seen as a distinct pinkish layer along the lower edge of the tray whereas the debris forms a greener zone above it.

The pink parasite-rich zone can be harvested manually by dragging a pair of forceps along it. The worms which are largely free of debris are then placed in tubes containing PBS and frozen Results of trials with the worm harvesting apparatus.

Some potential issues which might arise when this apparatus was employed under abattoir conditions were examined. 1) Speed and efficiency of recovery

Worms clean enough for antigen extraction were routinely obtained within 3 minutes of the cement mixer being filled.

With two operators it is anticipated that the apparatus will keep pace with an abattoir throughput of about 500 sheep per hour. There is potential for further automation eg mechanical opening of the abomasa, electronic control of the cement mixer

2) Effect of using water rather than saline

When worms were harvested manually they were processed in saline. It would be much easier if water could be used under the larger scale conditions of a slaughterhouse.

Substituting water for saline in the cement mixer had no apparent effect on worm recovery, nor did harvesting them off the mesh with a spray of water. The parasites remained alive and could be observed forming clumps in the base of the trays. Most importantly the yield of protective antigen recovered from worms harvested with water was no different from the yield obtained with saline

3) Delay between abomasum removal and opening. It was considered important to find out if some delay between the abomasums being removed and opened would affect the yield of worms as this would be inevitable in an abattoir Five sheep were infected with 5,000 Haemonchus larvae each and killed 22 days later. Their abomasa were removed and left unopened until all 5 sheep had been killed which took about 20 minutes. Each abomasum was processed individually through the apparatus with 5L warm water. Clean worms were obtained from each stomach within 2 minutes The delay did not affect the yield

4) Processing several abomasa in a batch

In a slaughterhouse where 500 sheep are processed in an hour more than 8 abomasa would require to be processed per minute. Clearly it would be very advantageous it several could be processed together in a batch rather than one by one.

Ten sheep were killed over about 25 minutes. Their abomasa were removed and held together in a bucket until the last one was recovered. All ten were opened and their contents were pooled into a bucket which was emptied into the cement mixer with 2OL warm water. The yield of worms recovered and their cleanliness was very similar to that expected had the abomasa been processed individually. Example 2

Table 1 : Recovery of adult Haemonchus from sheep infected with different doses of larvae July 2008 to Jun 2009

* mean vol. of worms recovered = packed settled volume in a 50ml centrifuge tube (Fig 7).

Table 1 shows that the yield of clean worms recovered from sheep by the device provided by this invention is similar to that when done manually. However, it should

be understood that harvesting using the device is much quicker than the manual method. Furthermore up to 10 stomachs can be processed simultaneously by the device. Figure 7 shows the volume of worms recovered from 7 individual sheep by the device.

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