WHAT ARE BIOLOGICS?

Shannon News, 26 February 1929, Page 4

WHAT ARE BIOLOGICS?

methods W treating disease In recent years great progress has been made in the per (lection • and sue. cossful employment of biological preparations for the prevention and cure of infectious or germ-caused diseases of farm animals! The general term "Biologies" has come to bo applied t«» these preparations, and-it'-includes anti-toxins, vaccines, bacterins, serums and various forms or types of those products of the laboratory. As they ore in common use by veterinarians, stockmen should know something regarding the nature of biologies, and a few facts on the subject may, therefore,' be instructive.

True vaccines contain living m:t weakened or attenuated terms of the disease each is used to control. The germs are suspended in broth, dilute glycerine, or saline solution. They are solely used as preventatives or immtin-. ising agents, having no curative properties. Injection of a Vaccine ' causes a mild attack of the disease or infection represented, and that confers an active immunity against subsequent natural infection. Vaccines have been much used for the control cf anthrax and blackleg, and there is also vaccine against contagious abortion and one against rabies. '

Bacterins, or bacterial vaccines, contain killed bacteria which have been grown in suitable media. They also contain the immunity-producing products of the germ growth, and when injected into the animals, stimulate the formation of protective substances which combat the subsequent invasion of disease-producing bacteria. They have been tried out as preventives and euros' for most infectious diseases :ind f| in some instances, have given good satisfaction. Anti-bacter-ial scrums are obtained from animals that have been hyperimmu'niseel against specific disease germ? and contain protective antibodies. Protective serum is much iisedin the immunising of hogs against cholera. Used alone, it confers passive or temporary'immunity; combined with virus (the cause of the disease), it' confers active or lasting immunity. Antitoxins are obtain-' cd from the blood pprura of horso* that have been actively immunised against specific germ poisons (toxins). They contain eleincnts (anti-toxins) which combat the toxin of the disease germs when they happen to invade the 1 body. The anti-toxins against tetanus (lockjaw) and diphtheria are good examples of this class of biologic. Our readers will also have heard of filtrates and nggressins usod in the control of blackleg, etc. Blackleg lil-i tratts, for example, is the media in! which blackleg bacilli have been' grown, but from which the bacilli have been removed by filtering. It contains the toxin used to produce immunity against blackleg. Aggressin is the fluid extracted from the tissues of affected animals, and contains the '■ immunising aggressin formed during the progress of the disease, and isi freed from the germs by filtration. Blackleg aggressin is a good example.

In attempting to control and cure mastitis in its various forms, bactcrins have been much employed and with fair success in some instances. An autogenous mastitis bacterin is that made from Anils'taken from an .affected udder, the germs therein being killed, and a herd autogenous bacterin is that which, is made from the fluids taken from several affected udders in the same herd, and is used to immunise unaffected cows in that herd.