JOHNE’S DISEASE IN CATTLE

Wanganui Chronicle, Volume 79, Issue 239, 9 October 1936, Page 11

JOHNE’S DISEASE IN CATTLE

STATEMENT BY MINISTER OF AGRICULTURE Owing to certain references to the disease of cattle known as Johnes disease, which have recently appeared in the Press, the Minister of Agriculture (Hon. W. Lee Martin) to-day stated that in view of the possibility of any scare being created in the minds of stockowners through any misconception of the nature of the disease, the characteristics of which were not generally known to farmers, he considered it desirable to issue a statement referring to the disease and its occurrence in New Zealand, also outlining the action which the Department of Agriculture is taking with regard to its control.

Johne’s disease gets its name from Professor Johne of Dresden, who in 1895 discovered the germ which causes the disease. Previous to that date a disease of cattle the symptoms of which were chronic scouring, with

rapid emaciation of the animal, was known to be common in Continental countries, but its cause had not been demonstrated. So far as the occurrence of Johne’s disease in New Zeland is concerned, a case occurred in an imported cow from Jersey Island in 1912. This animal was destroyed, and subsequently information was disseminated to the field staff of the livestock division so that a careful watch might be instituted respecting occurrence of further cases. As a result of this, specimens from suspicious cases were from time to time forwarded to the vetinary laboratory at Wallaceville. but it was not until 1928 that another case was diagnosed as Johne’s disease. This occurred in Taranaki and as a consequence attention was again focussed on the disease and further intensive inquiry revealed its presence on certain other Taranaki farms. Moreover, from reports received it appeared that the disease was more widespread than was at first thought, as cases with symptoms resembling Johne’s disease were described by farmers, the animals having either died or been destroyed without the matter being reported to the department. As the department’s officers had no legal authority to deal with Johne’s disease at thatl time, and the owners ol certain affected herds objected to the measures that were recommended to them in an attempt to control the disease, it was added to the list of scheduled diseases under the Stock Act in 1931.

Johne’s disease is one which develops very slowly and insidiously. It is due to a germ, not unlike the germ of tuberculosis, but wheras the latter mainly affects the glands, lungs, and other organs of the body, the Johne’s germ attacks the lining members of the intestine, causing chronic inflammation and thickening. As a result, of this there is at first intermittent scouring, which later becomes persistent, and is associated with rapid emaciation, resulting eventually in the animal’s death. Symptoms are rarely seen in cattle under three years old, and are most likely to occur following calving, at which time an infected cow is often observed to develop the symptoms of scouring and to break down very rapidly. Treatment is of no avail.

The manner by which the disease is spread is by the germ gaining entrance to the animal’s system in food and water. The germs are disseminated in the droppings of affected cal tie. One of the greatest difficulties connected with the control of this disease is the lengthy period which elapses between the time of infection of the animal and the appearance of symptoms. This is generally not less than two years and may be considerably longer. As an example of this a case can be mentioned which occurred in New Zealand where an animal showed symptoms of Johne’s disease over four years after it had been exposed to infection. It will be apparent

from this how difficult is the control of this disease, and how it Is that within the past quarter of a century it has been carried by apparently healthy animals into all parts of the world, in spite of quarantine. It must be apparent from what has been said that for there to be any hope of controlling the spread of this disease, a diagnostic test that will detect its presence in the animal before symptoms are shown is essential .and after many years of research such a test was eventually evolved. It is called the Johnin test, and is carried out in a manner similar to one of the commoner methods of testing for tuberculosis. After extensive preliminary trials on isolated cases of the disease the livestock division decided to test the value of Johnin testing at. half-yearly intervals as a means of eradicating the disease from two affected grade herds in Taranaki. This experiment has been under way now for nearly two years, and so far it appears to have given promising results. Moreover it has provided additional and very valuable information on the interpretation of the test results. The department is fully alive to the necessity for strenuous effort in an attempt to limit the occurrence ot this disease. It must, however, be reiterated that control of Johne’s disease presents most serious difficulties, a fact which is freely admitted in all countries in which it exists to-day. Total eradication does not appear, in the light of present knowledge of the disease, practicable, and attention is being directed to efforts to reduce its incidence on farms on which it occurs. To this end the department intends to carry out. periodical tests of animals on such farms, and by this means it is hoped to detect any cases and by their elimination control further spread of the disease. Reports from the Continent and also from the Channel Islands refer to the apparent good result following the application of heavy dressings of burnt lime to affected pastures, the effect of lime apparently being inimical to the life of the germ in the soil. This aspect is one which is being followed up by the department. Regulations have already been made providing for all imported cattle to be Johnin-tested, and since the disease is not known to occur in the South Island, the regulations also provide, where the department considers it necessary, that cattle from the North Island be tested similarly before a permit is issued for their shipment to the South Island. Some concern has been occasioned in the minds of farmers on account of recently published statements respecting the slaughter of an entire herd in Taranaki owing to the presence of Johne’s disease. In this instance such action became necessary