RESISTANCE OF DISEASE

Taranaki Daily News, 24 November 1934, Page 24 (Supplement)

RESISTANCE OF DISEASE

QUESTION OF HEREDITY AN IMPORTANT PROBLEM. A problem of great importance to breeders of live stock, and to a lesser extent, possibly, to the medical profession, is the difficult one of what part heredity plays in resistance to infectious disorders, writes the medical correspondent of the London Morning Post. In a report by Mr. A. Bradford Hill, issued by the Medical Research Council, there is reviewed the existing experimental data, much of which is on a statistical basis. It is clear that the problem is complex, for while different species of animals may show a well-recognised difference in their susceptibility to infections, within the same species the parts played by environment, habits and exposure to infection are difficult to unravel. Mothers can certainly pass on to their offspring anti-bodies circulating in their blood, and this form of what is termed “passive immunity” will persist for a certain period of time. More lasting immunity, however, is what the stockbreeder requires, and there the evidence becomes confusing. From his careful review, Mr. Bradford Hill concludes that between strains of the same species there is definite evidence of increased resistance due to inherited factors. Within any particular strain results are confusing, but it is reasonably clear that inherited factors do play a large part, and the “factors for resistance are dominant, or partially dominant, to those for susceptibility.” Whether such inheritance is specific for one particular type of infection or more general for all the noxious agents of disease is still unsettled. “The possibility of breeding a strain,” runs the conclusion on this aspect, “with fairly fixed factors for resistance or susceptibility to at least a particular agent, certainly seems to be an eminently reasonable supposition.” As to the degree of resistance which can be developed by breeding, the evidence is again conflicting, but it does seem possible to develop a scheme for the “combing out” of resistant animals, and the rules upon which this should he based are clearly laid down.