FOOTROT IN SHEEP

Wairarapa Times-Age, 27 November 1939, Page 3

FOOTROT IN SHEEP

FORMER UNKNOWN ORGANISM RESPONSIBLE RESULTS OF RECENT RESEARCH APPROVED MEANS OF CONTROL. (Canterbury Chamber of Commerce Agricultural Bulletin.) All diseased conditions of the feet of sheep associated with inflammation and pain and consequent lameness are generally designated footrot. By far the most common and most serious, however, is the chronic contagious form of this disease which is characterised by the separation of the horn from the soft tissues of the foot and ■ by little tendency to spontaneous reRecent research has demonstrated quite clearly that the bacillus necrophorus is not the cause of footrot, nor can the disease be produced by maceration of the feet with water. The primary cause of footrot is now known to be a hitherto unrecognised and. as yet. unnamed bacterium referred to in the literature as “organism K.” . . . The specific infective agent of footrot. unlike the bacillus necrophorus, is not universally distributed but found ■ only in areas where sheep are affected with this particular disease. Since every farmer is quite familiar with the common symptoms of footrot, it is unnecessary to describe them. The pain and lameness which are shown to an extent varying with the stage of the disease, reduce the normal grazing movements of the sheep and result in a rapid loss of condition. This in itself is a serious cause of economic loss where severe outbreaks of the disease occur annually; but it is not the only cause, for it must be appreciated that, under such circumstances, the sheep become very susceptible to more serious ailments such as pregnancy toxaemia, “bearing trouble," abortion and parasitic disease. PREDISPOSING CAUSES, Before the infective agent can obtain entry, some break in the continuity of the skin or horn of the foot must take place. Anything which does this is thus a predisposing cause. Most farmers know that one of the most common of such causes is some injury or abrasion of the soft tissues in the space between the claws producing the condition commonly known as “scald.” Grit and dirt lodged in the interdigital space may irritate the skin and cause small wounds. Constant grazing on wet low-lying pastures or on irrgated areas causes the horn structures of the foot to be softened, weakened and even decayed. Under such conditions also, the hooves become overgrown and distorted, thus encouraging the formation of cracks and the separation of the wall of the hoof from the sole. All of these conditions provide an opportunity for the infective agent, If it is present, to gain entry to the foot and so set up the disease. It will be appreciated, therefore, that “scald” is a distinct entity. It is not necessarily followed by footrot—though frequently it is—nor does it necessarily precede it. THE INFECTIVE AGENT. Since it is a specific contagious disease of sheep, it is clear that typical footrot cannot occur in any area, no matter how wet the pastures may become, or in what way the feet may be injured, unless the specific infective agent is present—in exactly the same way as such diseases as foot-and-mouth disease or anthrax do not occur in the absence of their specific infective agent. Footrot, however, has a definite seasonal and area incidence, being active and spreading in wet seasons or areas and not evident, or, at least, not spreading at other times or places. Since the disease does not arise spontaneously, it is necessary to consider where the infection comes from to start a new outbreak after the disease has been apparently absent during a dry period. In this respect there are several possibilities. The first is that the infective agent may survive apart from, the sheep, in the mud and faeces in yards or in damp pastures. Carefully controlled experiments have shown that the infection does not survive longer than three weeks under such conditions—in many cases not longer than a few days. The second is in the foot lesions of chronically affected sheep; i.e., animals—of which' there are usually a few on most farms —carrying a long-standing infection, frequently in malformed feet, but showing little or no sign of lameness. In the feet of such animals it has been demonstrated that infection may survive for at least three and a half years, and this is undoubtedly the chief source of infection for other sheep when conditions for the development of footrot again become favourable. The third possibility and no doubt a common method, is by the introduction on to a clean property of sheep suffering from the disease. A fourth and much less important means of spread is by the mechanical transmission of the organism in recently infected material such as mud and dirt adhering to men’s boots, motorcar tyres and the feet of farm animals. In a similar fashion clean sheep may pick up infection when taken to infected neighbouring properties or when driven over roads along which infected animals have travelled wilh'in the previous few days.

CONTROL. Since footrot has been shown to bej a specific contagious disease of sheep, the common methods used with other such diseases may be used in its control and eradication. By suitable treatment the disease can be eradicated | from the property and provided the | necessary precautions are taken to' prevent reinfection from outside, the property will remain free of the disease. As previously mentioned, it has been shown that the casual agent cannot survive apart from the sheep for more than three weeks. Therefore if pas-' tures are kept without sheep for a period longer than this, they can reasonably be expected to be free of Ihe infeetve agent. Ths first step in the control of this disease then is to subject the whole of the flock to a thorough examination for any signs of footrot. The feet of all sheep must be carefully examined for any signs of malformation or lameness. In this respect it is essential to remember that the infection may be deeply seated, and that in order to expose the affected tissues to the action of the solution used in treatment, all overgrown and diseased horn must be carefully pared away. Although it is essential to strip off all under-run horn, injury to healthy tissue should be avoided since it provides a means of entry for infection. The apparently healthy sheep should then be put through a footbath containing a suitable disinfectant solution and then turned out into a pasture which has been free of sheep for the requisite period. After the feet of the affected animals have been carefully cleaned and pared down, they also are put through the foot-bath. Following treatment these sheep are put into a special isolation or “hospital" paddock and treated at frequent intervals until complete recovery takes place. The more stubborn cases usually require the application of special hand dressings. Occasionally, a few cases do dot even respond to this treatment. Such animals are best eliminated from the flock. After the sheep in the "hospital” paddock have been free of all signs of the disease for about a month, they should be returned to the main flock after passing once again through the foot-bath. By such methods the disease can be eliminated from the flock. In order to reduce the chances of reinfection, all bought-in sheep should be regarded as suspects, treated as outlined above and put into the main flock only after spending an isolation period in the "hospital” paddock. Sheep taken to neighbouring properties for shearing or crutching should be treated in a similar fashion. TREATMENT. The most satisfactory method of treating the feet is by permitting the sheep to stand in a footbath containing a suitable disinfectant solution. It is unnecessary to describe such footbaths in detail since most farmers are familiar with their construction. In order to obtain the maximum efficiency from this method of treatment, however, it is well to bear in mind the following practical points. (1) The feet of the sheep should be as clean as possible before entering the footbath. Some baths provide for this by having a section about eight feet long containing water and small pebbles. Out of this the sheep come on to grating to allow hie excess water to drain away before entering the disinfectant solution. (2) The sheep must be left standing in the bath for three or four minutes to permit complete penetration of the disinfectant. (3) After coming out of the bath they should be detained on the grating of the shearing shed or in I the concrete pens of the dip so that I the disinfectant has time to take I effect, before being turned out, preferably to a dry pasture. (4) There is no necessity to put more solution in the bath than is sufficient completely to cover the feet of' the sheep. Disinfectant solutions—Although numerous preparations have been used as I disinfectants in the treatment of footrot. from the point of view of efficiency, cost and safety, it is doubtful if there is any more satisfactory' than copper sulphate (bluestone) or formalin. The strength of the solutions varies with the object of the treatment. Copper sulphate used as a safeguard should be mixed at the rate of four ounces to the gallon. For this puri pose also, one part of formalin is used to eight parts of water. For the treatment of severe "scald” and mild -cases of footrot, these concentrations should be doubled. Severe cases of footrot are best treated by hand dressings which may be in the form of solutions or ointments. After careful preparation of the foot, one of the following preparations may be applied daily or once every two days. 1. One part of formalin to two parts of water. 2. One pound of bluestone to one gallon of water. 3. 2-3 ounces of bluestone to one quart of vinegar. 4. 8 ounces bluestone, 4ounces of lyscl or fluid dip to one gallon of water. 5. One part powdered bluestone to two parts Stockholm tar. 6. Tincture of iodine. If arsenical preparations are used every precaution should be taken to guard against the possibility of ingestion of the poison.