INFANTILE PARALYSIS.

Hauraki Plains Gazette, Volume XXXVI, Issue 4817, 2 March 1925, Page 3

INFANTILE PARALYSIS.

KNOWLEDGE OF THE DISEASE.

CAUSE AND MANNER OF SPREAD.

Throughout the world from 1880 to the present day over 150 outbreaks of infantile paralysis have been recorded- states Dr. T, H. A. Valintine, Di-recton-General of Health, in a paper on the disease. In 45 epidemics which occurred before 1905 the average number of eases recorded was low, namely, 21. Since then there has been a marked increase both in the frequency of the epidemics and in the average cases recorded in each. Over a quinquennial period the number of cases per epidemic now averages from 300 to 600', and as an exceptional instance Ne.w York City reported 8928 cases in 1916, with 2407 deaths.

This increase cannot be wholjy accounted for by the fact that infantile paralysis is now better known and is therefore more readily recognised and diagnosed as such. Wickman, cf Sweden, in 1905-6 made the first systematic tstudy of the disease from an epidemiological point of view and found evidence that it was inflections He directed special attention to several factors in its spread, namely, routes of travel, public gatherings of children, abortive or ambulant cases, and healthy intermediate carriers.

in 1909 the disease was experimentally conveyed to monkeys by inoculation from the spinal cord of a child who had died of the disease. Since then leading geientists-end physicians in many countries have added considerably to our knowledge. The svmptoms of- the disease have been clearly, described. Its Pathology, thanks to the monkey, is definitely known. As regards bacteriology, this disease has been definitely shown to be one of those produced by organisms so minute that they will pass through the pores of the finest laboratory filter and remain invisible under the highest powered microsmope available. In this respect it is on all-fours with smallpox, measles, mumps, rabies, typhus, and yellow fever, which have been under investigation for many years. It is true of infantile paralysis, as of some of these other, “filter passers,” that by special culture methods visible and characteristic colonies or clumps of the organism have been cultivated, and that by repeated inoculation of a series of monkeys these clumps have been proved to contain the germ.. Work on filterpassing organisms its an advanced branch of bacteriology. Eminent bacteriologists are working at it daily. Neither care nor expense has been spared What we in New Zealasid can do is to provide a very small reinforcement to the large and expensively equipped army already in the field in this; branch of inquiry.

The virus obtained from the spinal cord, brain, splen, bone-marrow, etc., of fatal eases, or from the nose, mouth, and bowel discharges of living casets reproduces the disease when in - jected into the brain of higher ape;:. It has also thus been conveyed by swallowing and by application to the mucous membrane of the nose. This virus in the laboratory is readily killed by heat and by weak disinfectants (particularly hydrogen peroxide* in 1 per cent, solution and’permanganate of potash 1 part to 500 of water), but it resists freezing and drying for long periods; It has been proved that heaKhy associates of infantile paralysis cases occasionally harbour the virus in their noses and throats. •IMMUNITY. One attack of infantile -paralysis confers a high degree of immunity. Monkeys which have recovered from the infection show a high degree of resistance in that they are not susceptible to infection by .again inoculating them, and their blood-serum when mixed with the virus renders it harmless to other monkeys. ' It has also been shown recently that human blood serum from mild or abortive cases when mixed with the virus renders it inert, just as does the serum of typical cases in which paralysis has developed. MODES OF TRANSMISSION. The modern explanation of recurrent epidemics pfi infantile paralysis and their, distinctive features is that it is a very communicable disease, like measles, and is much more widespread in the community than would be indicated by the paralytic cases alone. Most cases are mild, escape not'ce, aud leave the individual protected against further attacks There is thus a high degree of acquired immunity except in the young. Only the occasional severe case with paralysis is recognised and diagnosed a? infantile paralysis. It is most infectious during the early stage of the disease We arc therefore dealing wi'h a common infection, always present in the community, but which in recent years and partielarly in the late summer and autumn seasons has gained an increased virulence. Persons of live years and under contribute approximately 70 per cent, of the cases, and epidemics in any one country tend to recur every three to five years, seemingly when a fresh supply of susceptible children is available. Persons under sixteen years contribute over 90 per cent, of the cases. There is much evidence to support the opinion that the disease both in its mild aud in its severe form is directly transmissible from person to person. In addition he.althy carriers, persons who have been in contact with a case, can carry the virus in the mucous membrane of their noses and throats without suffering any symptoms. These carriens, even if the infection they carry, comes from a mild unrecognised case, may produce an attack of severe type if they chance to convey the infection to a sufficiently susceptible person. INSECT-BORNE THEORY.

In this disease, the seasonal prevalence of which as a general rule corresponds to the seasonal prevalence of most insects, the possibility of conveyance by biting or other insects has bean closely investigated by many observers in different epidemics. The conclusion arrived at is that although

it has been possible, but difficult, to convey it experimentally from monkey to monkey by the bite of the stable fly and by contact of the house fly, this not .the way infection is spread from man to man in nature. With regard to vermin, such as lice, fleas, etc., the disease is quite as common u obviously clean and well-ap-pointed households as in those where vermin are evident. Although bedbugs and lice may invade any house, if they were necessary carrier-' of the drtase we should have a iioticeabiy increased incidence in houses most ’ike'y to be frequently by them. Moreeve! .t is the exception to find insectl.> te.= c the bodies of the children affee’e 1 with the disease. Again, it is li>id t. reconcile insect transmission with the small total incidence of the disease in any one epidemic and its preponderating occurrence in children. CLIMATIC THEORY. Though infantjle paralysis is now universally recognised to be an infectiouis disease, and though the concensus of opinion, which every year is further substantiated, ascribes its spread to contact direct or indirect, it has been thought by some that peculiar climatic conditions may predispose to tne disease and determine an epidemic, the germ itself being widespread in non-epidemic times. The data collected from many epidemics, inc’uding .a number of winter ones,.do not support this idea. Epidemics have occurred under very variable weather conditions as regards humidity, temperature, dustiness, rains aind snowfall. and wind. Again, in the late summer and early autumn epidemics, which are admittedly the commonest, it has often been noted that the radial spread of the disease does not correspond to any constant climate factor. The disease appears to follow lineis of transport rather than to corresponii to any definite climatic factor. Epidemics of most infectious diseases have a seasonal incidence. In the Northern Hemisphere this seasonal incidence over a long period of years has been accurately tabulated. In the Southern Hemisphere the reverse months are chosen—e.g., infantile paralysis favours January io March, diphtheria March to June, scarlet and typhoid fevers April and May. measles June to August, and whooping cough August to October The reverse is true of the Northern Hemisphere. ANIMALS. Domestic animals, such as the dog and cat as well as pigs and poultry, are known to Buffer at times from paralysis, and this was thought to be, perhaps, associated in some way with the human forms of infantile paralysis ; but during epidemic periods many examinations of such animals have been made, and no convincing evidence has as yet been adduced to establish this connection. The weight of present opinion inclines to the view that infantile paralysis is exclusively a human disease, and is spread oy personal contact. The victims of the disease are almost without exception sturdy, robust children. Though this has caused much speculation and is a very marked feature of infantile paralysis, it is b yno means exceptional with other infectious diseases. Pneumonia and, in some epidemics influenza, select the robust, and it may be said of infectious diseases as a whole, with the possible exception of tuberculosis, that the apparently robiist are as susceptible as the frail. This may te due to the fact that children brought up in remote' districts, while more robust than those living in crowded areas, have not been called upon to fight infection from the milder and more constantly prevalent types of the disease, and have.thus not acquired the immunity fthich such mild infections confer. Thus when the more virulent type of infection <s abroad th'e robust appear to suffer most. Probably a weakly child would, suffer more than a robust one if each had the same absence of acquired immunity and were exposed to an equally virulent infection. (Of late years it has been common to find in epidemic investigations that, roughly, one-third of the cases had been in recent contact with previous cases actually diagnosed. Mild or abortive cases which are not notified or specially controlled and which presumably can convey the infection are a constant feature in these outbreaks. This more than doubles the apparent possibilities of personal contagion. The Hypothesis of the transmission of Ihe disease through the agency of water, milk, dust, or mosquitoes has not been confirmed in a long series of experiments, nor in the epidemiological facts collected during various epidemics. It behoves us to inquiie closely into the incidence of each case, including in this inquiry all the patient’s movements and possible means of infection for at least one month prior to the attack.