FOOT-AND-MOUTH DISEASE.

Northern Advocate, 5 August 1924, Page 6

FOOT-AND-MOUTH DISEASE.

CAUSATIVE FACTORS

(C. S. M. lIOPKIRK B.V.Sc. (Melb.) Veterinary Laboratory, Wallaceville.,

Foot-and-mouth disease is an acute, febrile, contagious, and infectious dis-

ease of cloven-footed animals, in the course of which an eruption of vesicles develops on the mucous membrane and the skin, especially in the mouth and in the interdigital spaces. The causative factor is an ultra-microscopic mi-cro-organism. The disease exists in Europe, Asia, North Africa, parts of the United States, and in South American States. Australia, New Zealan.l, and Canada are still free from infection.

The disease attacks domesticated ruminants (cattle, sheep, and goats) and swine, but has been proved to exist rarely in deer, camels buffaloes, wild boar, horses, dogs, and even fowls. Human children are slightly more susceptible than adults, usually dying from a gastro-intestinal catarrh. Few humans, however, are ever affected. THE CASUAL ORGANISM. Loeffler and Frosch, in 1897, showed that the organism, in contradistinction to many that we know, would pass through a filter. The organism is found present in the blood generally at first, but later it becomes confined to vesicles and certain lymph-glands. According to Caree and Valle, secretions (except urine) are only infective it contaminated with vesicular lymph. There is no sustained proof that any other visible microscopic organism acts in conjunction with the virus. The tenacity of the virus is not of the , first order. It is supposed to live in j a closed glass phial in the dark for five j or six months, but otherwise it is very j susceptible to acidity, heating, drying, | fermentation, etc. Thus it is j killed in clieaese or butter by acidity or pasteurisation, and at a depth of j about Bin. below the surface in dunglieaps. Dahmer and Frosch (Germany) claimed recently to have discovered the casual organism of foot-and-mouth disease by means of a special ultra photographic apparatus made by KohTer, of Java, and to have reproduced the disease from various sub-cultures j of the organism. They named the lat- I ter Loeffileria revermanni, after two well-known scientific workers. This | claim will have to be confirmed by other investigators before being definitely placed on reeford as correct. PATHOGENICITY. ! Direct infection: Fresh lymph intro- ( duced into the veins of cattle produces | the disease lesions in one to seven [ days, with a dose of I.C.C. of a suspension of 1 of lymph to 100,000 of diluting fluid. Later the udder and feet are affected. Swine-lympli is more virulent than cattle-lymph. Scarification (scratching) of mucous membrances, with introduction of virus, proves fatal. Artificially dogs and cats are susceptible. Similarly, guinea- j pigs are susceptible if scarified on a ! surface without hair, or if injected in- J traven'ously. Rats have proved to be } i susceptible to injection and to intra- j venous inoculation, also by living in j • contact (Beattie, Lancet). j

Indirect infection: This is common and important, and may be through fodder, litter, stalls, trucks, r'oads, pastures, markets, drinking-water, attendant's hands, clothes, boots, etc., and possibly hides, wool, manure, and milk contaminated by excretions. There is also the possibility of carriers, such as birds, and this might actount for the jumps of the disease for distances of oiie hundred miles in a day or two. Sir Stewart Stockman and Garnett are authorities for this theory, though objections have been raised by prominent ornithologists. Beattie and Pede'ri, iii their experiments on glands from slaughtered cattle which were contact cases of foot-and-mouth disI ease, found vesicles on the feet and on

pleural surfaces of the lungs of rats,

containing a virus which seemed identical with that of the disease. Their

experiments have not yet been com- j pleted. The present outbreak in Eng- j land has been put down by Sir Stewart j Stockman to importation 'of green vegetables from the Continent of Europe, and of material fr,om the Argentine, where the disease has been particularly rife, but this has not been proved. In Switzerland experiments have proved that the disease will remain on a farm for at least six months, and it is said by Caree and Vallee in the Recueil de Medecine Veterinaire (September, 1922), that the virus remains for six weeks to eight m'onths in pockets of hooves of anii mals which have been affected. These investigators also declare that urine at the beginning ,of the disease is virulent, and would appear to be a greater source of contamination of fodder, etc., than other secretions. SYMPTOMS. The disease commences with fever —104deg, to 106deg. F.—more apparent in young animals than in old, accompanied by an accelerated pulse, diminished appetite, decrease in lactation, and constipation. The temperature j subsides With the appearance of vesi- • cles. Then there is, in cattle, a charj acteristic sucking of the lips and freJ quen t swalowing, with later a smacking of the lips. Saliva is first frothy, then becomes ropy and mixed with shreds of epithelium hanging from the mouth. Foot lesions cause lameness through inflammation of the coronet. In cattle, mouth lesions generally occur first, followed usually by foot

ions. In cows, udder lesions and

!. sions of vaginal mucous membrane ■ :iav also appear. In sheep and pigs, iui-nth lesions are not so constant, foot lesions being more important. Other regions affected are conjunctiva, trachea, and pharynx occasionally.

The seats of mouth lesions are the tongue (body and tip) and the mucousmembrane lining of the lips and dental pad. These lesions are all vesicular in character, and quite superficial and shallow. The vesicles and ulceration vary from the size of a pea to about lin. in diameter. The vesicles burst in about one to three days, threads of epithelium remaining attached for a while. Finally a raw, shallow ulcer is left, which becomes deep only if a secondary bacterial invasion occurs, j Healing is by simple ingrowth of epi- j thelium from the sides ,of the ulcera- { tion. Foot lesions occur at the junction of hair and hoof, and sometimes inside the hoof, especially in heel bulbs and [ interdigital spaces. They may cause I sloughing 'of the hoof if secondary invasion by other bacteria occurs, or even though confluence of several large vesicles destroying the coronary bands. Acute catarrhal gastro-enteritis often occurs in young animals, proving fatal. A malignant type may occur, chiefly in old animals, where a form of intoxication develops, showing rigors, paralysis, intestinal haemorrhage and finally coma and death. COURSE OF THE DISEASE. The disease in the majority of cases takes a favourable course 'of some five to six dayn. In mild cases two to three weeks may elapse if the various areas of infection show vesicles simultaneously. Following healing of the

| local lesions some animals quickly regain their former condition. If unfav- | ourablc conditions the animals may I die from multiple abscess formation, septicaemia, or intoxication, the result i of absorption from the secondary abscesses, etc.. which may be formed. The mortality is practically nil from the disease itself, but the after-effects are those which cause so much economic loss. According to Davidson, this is particularly heavy in dairy cattle through the following factors: — | Loss of condition, which in many i cases is never regained, or only with Considerable expenditure in suitable foods. Winter coats may be carried without casting—a sign of a "bad doer.'' Milk-yield is greatly increased for the remainder of the lactation period. Cows usually dry off a considerable time before next calving, and subsequent lactation periods seldom approach the old standard.

Hoof lesions often lead to arthritis, particularly in heavy animals, which have to be slaughtered. It is said that bulls are of little use for service till their hooves have sloughed off, when their vitality is often impaired.

Abortion is a common sequel, or calves at full time may be born dead or die later. Retention of the placenta is common, so bringing about sterility; and a percentage of the young Stock born from affected animals prove sterile subsequently. Mastitis, with loss of quarters, is a. common result. Dislocation of trade occurs, due to veterinary police measures. DIAGNOSIS AND TREATMENT. A diagnosis of the disease can be made by the presence of fever and constitutional disturbance, followed by foot or mouth lesions, or both, causing a shallow ulceration. Rapid contagion

and simultaneous affection of cattle, sheep, and pigs are factors of great use in diagnosis. In a newly infected country inoculation experiments from one anima.l to another might be required for confirmation.

Treatment would be impossible in a

new countrv such as New Zealand, nor

is it possible in England, where the disease is not always present. Slaughter of all contacts is advisable, and State policy generally provides for compensation for animals compul- ! sni-ilv slaughtered. In older countries

local lesions are treated, and in Hong

Kong a treatment which had some beneficial result was the intravenous injec- ; tion of trypan blue for its destructive j action on the organism, although liarm--1 less to body cells.

"The debtor is on fire," whispered a waiting litigant in the Court to the senior-sergeant of police, who was sitting at the lawyers' table (states the "Dannevirke News"). Sure enough he was, for smoke was issuing from a side-pocket. When the debtor entered the witness-box he had evidently placed a lighted pipe in his pocket and was serenely replying to examining counsel oblivious of the possibledanger to his person and clothing. The business of the Court was suspended for a few seconds while the police officer assisted the man to "extinguish the incipient blaee."

"The great advance made in sur-*; gery in recent years, especially during the war, has to some extent been the cause of the increased expenditure in hospitals all over the Dominion," stated Sir James Wilson in his annual report to the Palmerston North Hospital Board. "Modern demands necessitated new expensive methods of treatment, namely bacteriological, physiological, electric-therapeutic, and Xray departments. The average cost of these rtlone in New Zealand is £7 per bed." —"Manawatu Fvening Standard. *'