NOTES ON A FORM OF NERVE DERANGEMENT IN HORSES.

New Zealand Journal of Agriculture, Volume XII, Issue 5, 20 May 1916, Page 364

NOTES ON A FORM OF NERVE DERANGEMENT IN HORSES.

C. J. REAKES,

D.V.Sc., M.R.C.V.S., Director, Live-stcck Division

Some interesting cases of nerve derangement have occurred lately among horses in certain parts of the Dominion, principally in North Canterbury and in the immediate neighbourhood of Christchurch. A few others occurred in South Canterbury and on two farms in the Wairarapa, several miles apart. Though this is the first time any-general attention has been drawn to this trouble, the-inquiries which have been instituted have elicited the fact that occasional cases have occurred before in the North Island. . The affection is distinct from that which has- been • noted as a result .of ergotism or of feeding upon the ripe heads of certain varieties of rye-grass, Lolium temulentum in' particular. Though its' immediate causative agent is as yet undetermined, and is proving extremely difficult to discover, it is evidently a trouble whose onset is influenced by climatic ■ conditions, all the cases which are known to have' occurred having arisen in districts where an altogether unusually hot and dry summer has been experienced.The symptoms are not identical in every instance, they apparently varying according to the severity of. the attack; but the most usual and prominent is an exaggerated form of stringhalt (see photographs), sometimes accompanied by a gradually developing well-marked wasting of the muscles of the hind limbs. In some instances, usually in younger animals, this is not so noticeable, and a knuckling-over of the fetlocks of the fore or of both fore and hind -limbs is frequently observed Avin the most severe cases the animal goes down and is unable to rise without assistance, though actual paralysis of the hind quarters does not exist. .. Though the present is the first occasion on which this trouble has manifested itself in the Dominion to a sufficient extent to have been brought under the notice of the Department, it is well known in Australia, and in veterinary text-books is described under the term “ Australian stringhalt.” Mr. H. S. S. Kyle, Veterinarian in the Department, has seen cases in Australia, and is clearly of opinion that the affection now under notice is identical with this. In Australia it is not regarded as an infectious disease, and our observations and investigations here have afforded no cause for

differing from this opinion. The cause is evidently some toxic (poisonous) agent which acts directly upon the nervous system by causing a lack of control and co-ordination of muscular movements, and does not affect the appetite or the general functions, of the digestive and urinary systems. It may, however,, cause disturbance of the respiratory functions, affected animals, when forced to quick exertion for a little time, sometimes showing distressed and stertorous breathing.

A careful investigation is being carried out in an endeavour to determine how this toxic agent is produced, and it is already evident

that this is going to be a difficult matter, call ng for very thorough and systematic work. In Australia, according to latest advices, the cause, though not yet definitely determined; is believed to be of dietetic origin, and it is especially noticeable that there the trouble is most common in the driest seasons. No form of treatment has yet been found which ' will bring about quick recovery, but in all but acute cases, where death may occur within a few days, recovery takes place after the expiration of a long period, often as much as twelve months. We are at present experimenting with various forms of medicinal treatment, and any owners of affected horses should apply to the Department for the services of a Veterinary Officer in advising and assisting in the . treatment of the animals

if no available qualified veterinarian in private practice be available. Then all that we can do will be done.

One ■ noticeable feature is that the affection is not limited to horses grazing on pastures, a few cases having occurred among stable-fed horses, which certainly have been allowed to run outside at ■ night, but only in small enclosures where little or no herbage was present. In this connection- feeding experiments have been carried out at Wallaceville Veterinary Laboratory with chaff on which affected animals had been fed, but these have given entirely negative results. :

Investigations are being carried out on various lines, especially in the direction of endeavouring to determine whether any form of vegetable mould may be responsible, and in this Mr. A. H. Cockayne, Biologist to the Department, with his staff, is co-operating and rendering valuable aid. That moulds are capable of exerting a poisonous action upon the lower animals is a well-known fact, and this action is especially exerted upon the nervous system.

A careful observation is being kept on the Canterbury cases by Mr. J. Kerrigan, Veterinary Supervisor, and Mr. W. C. Barry, Veterinarian, together with Inspectors F. Mackenzie and J. Munro, and every endeavour is being , made to get to the bottom of the trouble. In addition to the work at Wallaceville, experimental

medicinal treatment is being carried out by the above-mentioned Veterinary Officers, and Mr. Kyle and Mr. A. M. Paterson (Veterinary Inspector at Timaru), and, in spite -of the obscurity of the immediate cause of the trouble, it is hoped that good results will accrue. .

In view of the evident identity of the trouble with so-called Australian stringhalt, it will be of interest to reproduce a portion of an address on “ Shoeing and Stringhalt,” given by the late Professor McCall before the' National Veterinary Association, London, at the annual meeting of that body in 1910, as follows :- AUSTRALIAN STRINGHALT. This disease, which in some respects resembles stringhalt in Great Britain, appears to be peculiar in Australia, where it affects large numbers of horses in certain districts. We are indebted to Professor W. T. Kendall, of the Melbourne Veterinary College, and Mr. Edward Stanley, F.R.C.V.S., for particulars of this malady. The following extracts and notes are made from veterinary reports furnished by them to the Minister of Agriculture for Victoria. In 1865 or 1867 the disease appeared in Victoria. It seems to follow in the wake of agriculture, and breaks out most frequently in paddocks which have been ploughed and then laid down to grass. As a rule it prevails in low-lying rich lands, and. it always comes on suddenly without any assignable cause; and usually about the autumn. Professor Kendall considers that the malady has three forms — namely, local, .general, and acute general. ' . 1 • The local form is the most common, and “ is characterized by a peculiar jerking action in one or both hind- limbs, ; which may be so slight as to be only noticeable when the animal is suddenly turned round or made to go backwards ; but in more severe cases both hind legs may be so badly affected , that " progress , can only be accomplished by a succession of bounds and plunges extremely painful to witness.” In cases where both legs - are badly affected, when the horse desires to move forwards the hind quarters are suddenly elevated, and one hind leg is violently jerked upwards, sometimes so high that the foot strikes the belly and remains so drawn up ; the other is then brought up in a similar manner, the former being at the same time suddenly brought to the ground with great force. At other times both hind legs will be jerked up simultaneously, or in quick succession, and the hocks remaining, flexed to their utmost extent, until the haunches almost reach the ground, before the horse has power to bring the feet down. The appetite is almost invariably good, and the digestive and urinary organs appear to perform their functions properly. This form of the disease seldom proves fatal, and affected animals gradually recover without treatment in from twelve to eighteen months.

General Form. The fore limbs are generally affected as well as the hind ones, but instead of being jerked up like the latter they are carried stiffly, forward, the knee being scarcely bent at all. When undisturbed a horse affected in this manner may graze and get abou: without much

difficulty, but cannot get along at all when chased or excited, but begins to plunge and flounder about; some fall, and others, after making violent struggles to get away, come to a sudden standstill, their heads being elevated and nostrils dilated. If near enough the heart may be heard beating violently. Acute Form. — The symptoms differ differently from those of either of the other forms, but as all three are found affecting different animals in the same mobs at the same time and under precisely similar circumstances, it is evident that they are . only modifications of the same disease. There is a dragging in all the limbs and frequent stumbling, the hind fetlocks knuckle over, and the thighs have a thin, wasted appearance when viewed from behind. If the horse is made to move any distance he breaks into a perspiration. The attack is usually very sudden. Should the horse fall or lie down he may be unable to rise, and struggles violently ; but if raised by means of slings he can both stand and walk, and if properly attended to he usually recovers. Treatment. Change of pasture, as well as of locality, is one of the surest means not only of preventing the disease, but also for hastening recovery in those already affected. Medicinal treatment is of doubtful benefit. Causes. —-Eating of so-called dandelion, metallic poisoning from venadium, intestinal worms, rheumatism, ticks, and flies have all been credited with being responsible for the disease; but, upon close investigation, the evidence necessary to incriminate any one of these has been found wanting.