The first diagnostic tests for Johne's disease were created after the discovery of how to cultivate M. paratuberculosis in the laboratory. Recognition of the disease in the U.S. led to early warnings of its potential impact on animal agriculture.

By the early 1900's, pseudotuberculous enteritis was well recognized as a new disease and one that was widespread. Scientists proposed a variety of alternative names for the disease, such as paratuberculosis and hypertrophic enteritis. In the Annual Report for 1906 of the Principal of the Royal Veterinary College, J. McFadyean coined the term "Johne's disease". Most publications since then have used either Johne's disease or paratuberculosis when referring to the disease. In 1908, L Pearson published the first report of Johne's disease in the USA (Pennsylvania).

The 1910's witnessed many discoveries about Johne's disease. In Denmark, O. Bang learned that animals with Johne's disease responded weakly or not at all to intradermal injection of antigens prepared from the tubercle bacillus (Mycobacterium bovis), but responded well to avian tuberculin (antigens prepared from Mycobacterium avium). On the basis of this observation, Bang suggested that avian tuberculin could be used for diagnostic testing of animals. This was confirmed a year later in England by G.P. Male. Thus, even before the bacterium that caused Johne's disease was isolated, scientists believed it to be related in someway to the bacterium causing tuberculosis in birds. A critical difference was that the organism causing avian tuberculosis could be grown on laboratory culture but the organism causing Johne's disease could not.

A serendipitous observation by the British scientist F.W.Twort led to the isolation of the etiologic agent during attempts to culture the Johne's disease bacterium. Twort's failure to keep pace with cleaning laboratory glassware and his discriminating eye enabled him to note small bacterial colonies growing like satellites around larger colonies in old cultures he was preparing to discard. The larger colonies were contaminants of the common hay bacillus, Mycobacterium phlei. Suspecting that the M. phlei bacteria were providing some essential nutrient, Twort incorporated a heat-killed preparation of M. phlei into his culture medium. This new culture medium, he discovered, supported the growth of a new acid-fast bacterium. He named it "Mycobacterium enteriditis chronicae pseudotuberculosae bovis Johne". In 1912, H. Holth also reported successful isolation of the cause of Johne's disease. Holth recognized the disease descriptions of Bang and simply called the organism he isolated the paratuberculosis bacillus. He failed to receive much recognition for his discovery.

After the etiologic agent could be cultivated in the laboratory, antigens were obtained from it for diagnostic testing. They were used in skin testing (as was done for tuberculosis), and for assays to detect antibodies in serum samples using complement fixation and agglutination techniques. The man who first referred to the disease as Johne's disease coined the term "johnin" for the skin test antigen since the equivalent preparation for skin testing for tuberculosis was called tuberculin. The next several decades were devoted to evaluation of these and other diagnostic tests and to improvements in methods for laboratory cultivation of the organism.

Early warnings in the USA

K.F. Meyer, in a report to the Pennsylvania State Livestock Sanitary Board said:

"....the economic loss will become one of a very serious nature if necessary steps for the control of this disease, which has been brought to this country by importation, are not taken."

Scientific advances

In the 1920s, paratuberculosis was described in animals on the African and Asian continents. Valle and Rinjard, recognizing that the subcutaneous injection of M. paratuberculosis did not cause disease, evaluated vaccination as a means to control spread of the Johne's disease. In 1923, the first edition of Bergey's Manual of Determinative Bacteriology was published and officially named the causative agent of Johne's disease Mycobacterium paratuberculosis (Bergey's Manual is a catalogue of all bacteria and their characteristics and is considered "the bible" of bacterial identification). Much energy was spent in the 1920s to find a small laboratory animal model of Johne's disease. Although some investigators will debate this conclusion, the goal of finding a small laboratory animal that develops pathology and disease truly typical of Johne's disease after experimental challenge with M.paratuberculosis remains elusive.

A comprehensive description of Johne's disease

Bulletin 343 from the University of Wisconsin Agricultural Experiment Station provides a 22 page description of Johne's disease, complete with pictures of affected animals, tissues and laboratory cultures of M. paratuberculosis. In this publication, these astute scientists gave sound advice to farmers that is still true today such as:

"...eradication (of the infection from a herd) by elimination of those animals showing symptoms would, in most instances, not be successful."

"Prompt removal of all suspicious animals from the herd and care in the purchase of animals will certainly do much to limit the continued spread of this disease."

"The prompt separation of calf and dam will, undoubtedly, prevent the infection of the former, as it does in tuberculosis."

Unheeded Warnings

Larson, Beach and Wisnicky from the University of Wisconsin reported on the occurrence of Johne's disease in Wisconsin dairy herds in the Journal of the American Veterinary Medical Association and offered this advice:

"The disease has, at present, a limited number of sources from which it can spread.....These sources of infection will continually increase, unless agencies are operative to offset the constantly increasing commerce in cattle."

"...the present position of Johne's disease is compared with that of bovine tuberculosis 60 years ago and, if not controlled, it may become a more troublesome scourge for future generations than tuberculosis is for the present generation of cattle owners."