RABBIT DESTRUCTION BY CHICKEN CHOLERA.

Mount Ida Chronicle, Volume 29, Issue 1478, 26 February 1898, Page 3

RABBIT DESTRUCTION BY CHICKEN CHOLERA.

Mr Gilrutb, M.R.0.V.5., Chief Veterinary Officer and Bacteriologist, to the Government, has this week arrived at Mr Log-Mi's, Maritarga, to conduct further experiments in rabbit destruction l>y means of chicken cholera. It will lie remembered that in 1896 Mr Gilruth visited Europe, and at the Pasteur Institute, Paris, specially studied this subject. Last year at Clydevale he conducted a series of experiments on a larger scale than had hitherto been attempted, and under favourable circumstances. Clydevale station has an area of 35,000 acres, but the part experimented on was an area of about 3000 acres, and is the worst on tht. station. The preparation of the virus is thus described :

" Cultures of the virus (originally brought from the Pasteur Institute by me) in sterilize >1 alkalinized broth were used nearly always, for purposes of certainty and convenience, though at times the blood of rabbits dead of the disease was substituted. At first a mixture of one part of a 24 to 48 hours' old culture to two parts of water was employed, but later on the strength was reduced to one part culture to six parts of water. The usual method of procedure was to dissolve 51b of sugar in five pints of warm water, and, after cooling to under bloodheat, to add three-quarters to one pint, of broth culture, the whole being thoroughly mixed. Then, gently stirring meanwhile, pollard was gradually added, till the mass was of a tough, doughy consistency; after which it was rolled out on a board, and cut into small pieces, each about iin square and |in thick. It fact, the usual method of mixing phoaphorised pollard was followed in principle. Six pints of liquid required ahout 201b of pollard, and made from 5000 to 6000 pellets of the above size- These pellets, freshly made, were deposited towards evening on up-turned sod 3, near burrows, the sides of gullies, on the riverflats, &c. Generally two pellets were placed on each sod, which as a rule was about 10 paces apart from the next, but when it became evident the material was liked, only one was deposited. Later on, a plough furrow was traced round the tops and bottoms of the gullies, alongside the fences, &c , as being more convenient than turning a sod by means of a spade. The intention of turning a fresh sod was to draw the rabbits to the oait, but further experience showed this .to be absolutely unnecessary as they were discovered almost wherever placed. In fact, the fear that the rabbits would not eat these pellets, seeing the paddocks were far from being bare, was soon found to be unwarranted, for the morning after the first distribution not more than from 3 to 5 per ceut. remained uneaten. Each pellet would, as a rule, contain from one drop to one drop and a half of the original culture ; and I have repeatedly found that a third, or even a fourth, of a pellet was as deadly in results as two or three. However, as it might have been raised as an objection that dosing a rabbit with a dissolved pellet was not a proper control, and in order to ascertain the truth of a suspicion I had that a rabbit having tasted the pollard, and found it pleasaut, followed up ths trail with his keen scent, making a regular meal as it were of the pellets, I decided to make sume experiments in an inclosed area "

A large number of experiments were made) from a very le gthy description of which we cull the following extract: . '* An enclosure was made, but containing no burrow, the shelter being supplied by some cut gorse-bushes, and 15 rabbits were placed therein. This was in order to observe, if possible, rabbits eating the material, and also to secure, without requiring to dig them out, those which died. On the 12th June 40 pellets were placed around the edge of the enclosure at 5 p.m. Half-an-hour afterwards none could be found, but it was probable many were trampled under foot by the rabbits endeavouring to get through the netting. On the morning of the 14th one rabbit was found dead; another died at noon. The same day 15 pellets were placed on a long fiat piece of boarding, the rabbits being watched. The first to come out of the brushwood sniffed at the board and went off without tasting the material; the next tasted a piece, and, evidently find ing it good, picked up five of the other pieces in about half a minute, fiually running off as if startled ; the third acted in a similar manner, and ate the remainder, and hopped about the grass as if looking for more The same afternoon a semi-liquid mass of the consistency of porridge was made up, of about the usual strength, and a dozen teaspoonfuls placed at intervals on the plank. I expected this would not be so templing but found all eaten in half an hour. On the

15th two were found dead in the morning, and another died at 1 p.m. On the 17th two more died, on the 18th one died, and on the 19th none. On the 19th, thiee rabbits remaining, 24 pellets, mide with virus kindly supplied by Mr Pound, from Queensland, were placed in ihe eoclosure, with the usual result that all were' eaten. On the 21st two were found dead, and on the 26th the remaining one died. All these animals died from chicken cholera, as verified ; and control experiments were carried out as usual on other rabbits, with the same material as was placed in the enclosure, f hus it was conclusively shown that rabbits relished these pellets, and that the virulence was not decreased by the material being mixed with pollard and sugar. In fuct, there is no doubt that the sugar is able to conserve the virulence of the virus, for I found pellets still virulent after being exposed to the weather tor three days, during which time there was hard frost, snow, rain, and also abont eight hours'sunshine. Again, pellets kept on the window sill for 70 days exposed to the sunlight by day and frost by night still retained their virnlence."

"Asa result of the distribution of a large cfuantity of virus, oyer thirteen gallons of diluted culture having b;eu used in various manners, the method of distributing in semisolid nature seemed to be the best. I found very little difference, if any, between the results obtained from'?pellets mixed with sugar, and those without sugar, There was no doubt that wheie rabbits were, comparatively speaking, fewin number, the results of the distribution was more apparent, as was to be expected. The virus iisrd'was chiefly that brought by me. from't « Pa;teur Institute, although .on a. few - occasions, after being supplied by Mr Pound with the Queensland vi>us, that was used, but the results were in no way different."

He believes that there is no reason to hope that it will eradicate the pest. It is, however, a cheap poison, aifttho trusts that further experiments "in suininer may prove it to be more'etftoaeious theti than it proved in winter. In certain circumstances, compared with phosphorizcd pollard the latter shows bettor results.

" Comparing these two poisons, ho remarks regiinling chicken cholera.— I. It is easy to prepare. Before the material is distributed, a small quantity should be forcibly administered, to, say, three rabbits,;, after death, in about twenty four hones; tlie liver, heart, and kidneys of each should be cut up, and, with the bloody nlixed with a pint of water, and to this liquid, strained through a cloth,; /sfaould be udded the requisite quantityof pollard to make pellets. A boy can prepare the material by using caught rabbits and drenching them as indiciiied, or by keeping a small enclosure without burrows in whicn a few could be f«d at intervals. The rapacity of the hawk* prevents one from using those that have died outside the burrows. The" first supply of virus could be sent direct from Wellington, and afterwards incubated in the living rabbits as indicated. Pellets, after being made up, may be kept a very considerable length of time, especially in a durk place. 2. It is not dangerous to msn or other animals, such us cattle, lv>rscs, and sheep, e.g., at Clyde* ale I mixed- sixty pellets with water and drenched a sheet , and, as lit' showed not the slightest ill effects Uterefiom in six days, I injected forty drops of a pure culture underneath the akin of the ti.igh, :ind with the exception of a slight stiffness for a day. the animal showed un illness. 3 If care is taken, it is not dangerouw to fowls. At Clydevale the cultures were made, aid the pollard mixed, in a small office, not ten yards from the poultry yard, aid the fou'ls witu frequently close up to the door of the building, yet not a. Minple cxi« of the dixea»o occurred amongxi them 4 Mixed with jwjlard it is readily eaten by lh" rubHtv. iii*?l -tao as !i!y b yvp*&j

'U but in summer further sxperiments are executed to show- it to be very useful. especially - when phosphorus other poisons are ■ f little use.. 5. Death is practically paiiil'-fg, and so other rabbits are not frightened as with phosphorus, or with trapping. 6. Although mildly so with rabbits living under" natural condition', the disease is undoubtedly contagious, thereforea dead animal in a burrow is always a possible source of infection to the others, especially young rabbits, and particularly as the virus may live for months if protected from light. Of phoaphorised pollard he remarks : "It the phosphorus be dissolved by bisulphide of calcium, as was the case at Clydevale, and pellets properly made, the rabbits take them readily. Naturally, as phosphorus and bisulphide have not a pleasant taste, there "is no question of one rabbit eating a quantity of material. Again, as the death from phosphorus is very painful, and the rabbits cry out in agony, the others leave, as is well known to all having experience with this poison, a result benefical from the individual point of view only. But against all this, in dealing with phosphorus, the danger to human.beings and stock is a great disadvantage, especially with small runholders and farmer* whete it is very iuconvenient to shift the stock, and it is on these places where the dissemination of chicken cholera virus may be found to be of most value.