TREATMENT OF FOOTROT

Southland Times, Issue 23374, 4 December 1937, Page 19

TREATMENT OF FOOTROT

DISEASE REGARDED AS INFECTIOUS FORMALIN AND BLUESTONE CURES The most extraordinary thing about footrot as a sheep trouble in this country is that no one ever thinks of regarding it as an infectious disease, writs Bluestone in The Australasian. We have never come to look on any sheep complaint except anthrax, and minor ones like “pinkeye” as being contagious things, yet black disease, for instance, is one of the worst of this type imaginable, and its control should lie more m the complete destruction of the carcasses of sheep that have died from it than in vaccination. The latter is always a preventive against heavy losses from disease. Control work therefore really lies in stamping any disease out at its origin, so that germs do not exist to cause further infection. This is the present position so far as footrot is concerned. For decades sheep men have accepted it as part and parcel of their ownership of well-grown pastures that are damp or wet with dew in the autumn and spring. Footrot today is widely believed to be “in the ground and so not worth the worry of trying to eradicate. Such an outlook would be poor enough if it were true, but happily it is not so. The reason for this is that the one fact above all others that has come out of the Council for Scientific and Industrial Research’s work at the McMaster Animal Health Laboratory, Sydney, in recent years, is that footrot must be classed as a highly contagious disease. What this means is that if the germ or germs responsible can be stamped out before they get to unaffected sheep s hoofs, footrot can be beaten on every farm. The disease has been proved not to be one inherent in thick moist pasture at all, even though this seems to be one essential for the spread Oi the infective organisms. NATURE OF INSPECTION An officer of C.S.I.R. (Mr W. I. B. Beveridge, B.V.Sc.), who is on the eve of departing for America to study the disease with other research men at present working on it there, has found out much about footrot in the last two years. The actual germ, or, as it seems to be, group of germs, responsible has not yet been isolated, but that is of no consequence to the grazier, since it is known that one or more out of four types of bacteria are responsible. The actual details of these would probably tire the reader somewhat, so it will suffice to say that “organism X” found two years ago is not the causative agent by itself. Along with three others, it is concerned with the cause of footrot, and these other three organisms have all been isolated from typical footrot cases. It has been known for some time that if material is taken from the feet of a footrot sheep and applied to those of an unaffected animal, nothing happens; but if the latter’s hoof-soles and spaces between the toes are first scratched sharply or allowed to become inflamed by the penetration of the larvae of a very common harmless sheep parasite—Strongyloides pappillosis—then, typical cases of footrot occur. This meant that the necrotic or dead material contained the causative germs, and that piece of information is the item of extreme value to the sheep owner so far as control disease is concerned. He now knows that by no other method out of the hundreds'that have been tried by C.S.I.R. can sheep be infected with footrot. All the germs for fresh cases have to come from sheep already infected, who are continuously

spreading them from their overgrown feet about the pastures. PENETRATION OF GERMS From these infected pastures clean sheep soon pick up the causative germs, which merely adhere to the horn or skin awaiting a chance to penetrate and set up the characteristic lesion of the disease itself. They cannot break through the horn or skin unaided, and have to wait for occurrences which are beyond mortal aid in preventing to assist them. The skin between the toes is usually the first to present a break for the germs, as it is soft and open to scalding by the little mud and grass packs that build up there in the moist pasture. Sometimes the skin is pierced by thistle spines or woody splinters, and at others by the Strongyloides larvae. Whatevei is the cause of the actual skin penetration, is nearly always associated with the type or the larval contamination ot the pasture on which the sheep contract the disease so frequently. This actual skin penetration by some unrelated

means is absolutely necessary before the infective germs have any chance of causing footrot. The moist, well-grown type of pasture on which the disease invariably recurs each year is also favourable to infection for two other reasons. Sheep are stocked on these plots very heavily, and one infected animal can spread the organisms about the grass blades so well that many of its mates are bound to come into contact with them inside one or two days of |heir release from the rotten feet of infected stock. This brings us to the second significant feature of this class of pasture, which is, that, by providing moisture, warmth, and cover, it makes it possible for the organisms to live more than the few hours they would last for if dropped on to bare ground in the sunlight. None of the footrot germs exist for long under unfavourable conditions, but these richer pastures provide the best natural ones for them to persist in, and even then they do not live more than two or three days at the most. CONTROLLING DISEASE If the germs die out so easily, why do they persist over the dry summer months, when the pastures provide no protection for them? The answer is that they are carried from season to season in the feet of chronically infected sheep, which do not show any ill-effects in those dry months because the horn and skin are too dry for the germs to proliferate and cause marked and visible hoof destruction. This is the big problem in control. It is definitely established now that footrot is carried over the dry summer by such sheep, and that if they are detected and cleaned up in the spring, the disease will die out with them, unless carried by other outside sheep introduced to the flock. Of course, on sheep country that is green and moist throughout the summer it would be almost impossible to stamp footrot out, as there would always be plenty of cover for the germs in the pasture; but this does not apply in the greater portion of our footrot areas. As a routine practice each year, all the sheep on a property should be gone over as soon as the pastures start to dry off properly in the late spring, and even the least suspicious foot pared back. Then every animal should be run through a footbath, which entails holding them for periods of up to 30 minutes in two to three inches of 2 per cent, formalin and water, or 5 -'er cent, to 10 per cent, copper sulphate and water; and this is a rather tedious and exasperating job. After it, however, not one of those sheep, unless perhaps a very bad case, which should be isolated, will be likely to infect the pastures again. If they are turned into a paddock that has not run any sheep for a week, there is little

risk of footrot breaking out in the mob again next season, provided no infected sheep are added to them and that thei are not turned on to pastures vacated less than a week before by similar stock in whom footrot is present. These, very briefly, are the prin-1 ciples by which it is believed footrot can be effectively controlled, and, summed up, they merely consist of adequate precautions against reinfecting the pastures on which clean sheep are run together with a previous thorough treatment of those sheep to ensure that they are not likely to harbour the disease in lesions of the feet which are chronic, and so do not cause the severe lameness that requires immediate attention.