,,INTERNATIONAL SOCIETY OF BIOCLIMATOLOGY AND BIOIETEOROLOGY" First Bioclimatological Congress Vienna, 23 27 September1957 -

Human Bioclimatology (General Pathological Bioclimatology)

THE BIOCLIMATIC APPROACH TO THE PREVENTION OF POLIOMYELITIS

Mr. F.A. Irving (Great Britain)

I.

I N TR

O DUC

T I ON

Consideration of the epidemiology of poliomyelitis shows that it is well established that t h e d i s e a s e i s o f an i n f e c t i o u s nature, b u t t h a t on t h e o t h e r h a n d t h e i n f e c t i o u s nature of the disease alone does not account for several important features of outbreaks, namely (a) an u n u s u a l l y p r o n o u n c e d s e a s o n a l d e p e n d e n c e ; ( b ) t h e f r e q u e n c y w i t h w h i c h o n l y one m e m b e r o f the household is often attacked ( a l t h o u g h s o m e t i m e s more t h a n one member o f a h o u s e h o l d may be attacked); (c) the increasing severity of the seasonal waves of the disease in countries with increasingly high standards of living. It seems clear therefore that any attempt tG evaluate the environmental factors which are of importance in predisposing both the population and individuals to attacks of poliomyelitis , m u s t t a k e i n t o a c c o u n t and p r o v i d e an e x p l a n a t i o n for these phenomena. With regard to the dependence of poliomyelitis upon seasonal conditions, a further point requires t o be e l u c i d a t e d , namely, in different parts of the world outbreaks of the disease may v a r i o u s l y coincide with the bot season or the cold or wet season, and the environmental f a c t o r when f o u n d m u s t be of s u c h a n a t u r e as t o e x p l a i n o u t b r e a k s of t h e d i s e a s e u n d e r these varying circumstances also. II. The f o l l o w i n g these problems:

is

a description

I N V E S T I G A T I O N

o f an i n v e s t i g a t i o n

w h i c h h a s b e e n made w i t h a v i e w

to

solving

SEASONAL DEPENDENCE Many a t t e m p t s h a v e b e e n m a d e i n t h e p a s t t o r e l a t e the incidence of poliomyelitis tic conditions, e.g. sunlight, rainfall, relative humidity, mean temperatures etc., without success,in t h a t no c o n s t a n t conditions have been found whzch are predisposing myelitis .

to climabut all to polio-

Many a t t e m p t s h a v e a l s o b e e n m a d e t o f i n d a c a r r i e r of the infection of a seasonal nature, but all these have been without success, and t h u s i t a p p e a r s t h a t t h e s e a s o n a l w a v e s o f poliomyelitis are due to bioclimatic factors, i.e. the factors within the environment which increase the susceptibility of the population to poliomyelitis . I n an e a r l i e r investigation I drew a t t e n t i o n f l o w s i n E s s e x when p l o t t e d i n a c e r t a i n way the weekly number of poliomyelitis infections o f t h i s r i v e r c u r v e and i t s c o i n c i d e n c e w i t h when i t i s r e a l i s e d that this river curve is myelitis wave c u r v e s , t h r o u g h o u t the northern c i d e n c e of t h e two c u r v e s i s o f s u c h a n a t u r e lightly.

to t h e f a c t t h a t t h e wave c u r v e of the river gave a reasonable correspoudence to the curve of i n E s s e x b e t w e e n 1947 and 1 9 5 4 . The s i g n i f i c a n c e the poliomyelitis wave i n E s s e x i s g r e a t l y e n h a n c e d of t h e same g e n e r a l s h a p e and t i m i n g as t h e p o l i o t e m p e r a t e z o n e s o f t h e w o r l d , and t h u s t h e coinand s u c h i m p o r t a n c e t h a t i t c a n n o t be dismissed

2 From t h e c o r r e l a t i o n between the outbreaks of poliomyelitis and the hot weather in this c o u n t r y and t h e f a l l i n g river levels, i t may be d e d u c e d t h a t t h e h u m a n b o d y m a y a t this time o f t h e y e a r be s u f f e r i n g from salt depletion due to evaporative effects, and this deduction g a i n s some s u p p o r t f r o m t h e s i m i l a r i t y b e t w e e n t h e f a c t o r s w h i c h a r e known t o c a u s e s a l t depletion and many of w h i c h same f a c t o r s a r e known t o be p r e d i s p o s i n g to paralytic poliomyelitis. In Essex there are indications that the incidence of poliomyelitis is less in the areas of the County with more saline water supplies. Rinehart (1944) noted that studies of patients early in the course of poliomyelitis reveal t h e common o c c u r r e n c e o f s a l t d e p l e t i o n . Dr. Gallup (1950) found that poliomyelitis cases had a lower salt intake than similar control groups. Examination of the seasonal changes in the environment in Great Britain suggests that almost a l l of them s u p p o r t t h e s a l t d e p l e t i o n theory, although in addition the place of fruit and vegetables i n t h e d i e t may a l s o be a f a c t o r a t t h i s t i m e o f t h e y e a r . I f t h e salt depletion theory is applied to poliomyelitis outbreaks in other parts of the world, it seems that it can be s a i d t h a t t h e r e i s n o t a n y m a t e r i a l difference between the environmental factors in other countries in the northern hemisphere, and t h a t i t i s o n l y a m a t t e r , possibly of the relative degree of importance of the respective complementary factors. There are parts of Africa where it has been reported that the poliomyelitis wave i s c o i n c i d e n t with the onset of the wet season, b u t t h e same p r i n c i p l e s c a n w e l l be a p p l i e d , namely there are circumstances w h i c h may g i v e r i s e to salt depletion, and f u r t h e r , i t i s t h e t i m e t h e r e when t h e f r u i t and vegetables ripen and when the inhabitants no d o u b t p a r t a k e f r e e l y o f a v e g e t a r i a n diet. The c o n n e c t i o n b e t w e e n the ripening of fruit and v e g e t a b l e s and the incidence of poliomyelitis in Great Britain and S o u t h Africa (and also Mauritius) raises the question of the susceptibility of vegetarians to poliomyelitis. EPIDEMICS IN TIlE MALTESE ISLANDS,

1942 -

1951:

Very careful consideration has been given to these epidemics which gave rise to a total o f 743 c a s e s w i t h 27 d e a t h s . They are interesting in that they are in an island community and have been the subject of special study. Furthermore, the water supplies on M a l t a are saline and similar in many respects t o some of t h e s a l i n e w a t e r s u p p l i e s in Essex. It has been said that the solving of the problem of the outbreaks of poliomyelitis i n M a l t a may l e a d t o the understanding andeventual control of poliomyelitis. The p r e s e n t r e s e a r c h into this matter has been directed to ~istinguishing between the poliomyelitis outbreaks which occurred during the natural expected poliomyelitis s e a s o n t h e r e and t h e s p e c i a l outbreaks which have occurred outside what w o u l d n o r m a l l y be r e g a r d e d a s t h e p o l i o m y e l i t i s season. Of t h e f o u r m a j o r o u t b r e a k s i n t h e t i m e m e n t i o n e d i t h a s b e e n f o u n d t h a t two o f t h e m c o i n c i d e d with the anticipated poliomyelitis s e a s o n i n t h e h o t t e r m o n t h s of t h e y e a r , and t h e o t h e r ~two outbreaks both occurred in November. As a r e s u l t of careful s t u d y of t h e G o v e r n m e n t and o t h e r r e c o r d s r e l a t i n g to Malta it has been established t h a t b o t h t h e N o v e m b e r 1942 a n d t h e N o v e m b e r 1945 o u t b r e a k s c o m m e n c e d immediately following the issue of large quantities o f d r i e d m i l k p o w d e r . The N o v e m b e r 1942 outbreak commenced upon the relief of t h e s i e g e of M a l t a when q u a n t i t i e s of dried milk were issued, particularly to the children, a m o n g s t whom t h e d i s e a s e w a s w i d e s p r e a d ; and the November 1945 o u t b r e a k f o l l o w e d i m m e d i a t e l y upon a m i l k s h o r t a g e w h i c h was s o l v e d by t h e d e r a t i o n i n g of milk powder. Wis r e g a r d t o t h e p o s s i b l e effect of the saline water supplies upon the incidence of peliomyelitis i n M a l t a , t h e r e i s e v i d e n c e t h a t t h e r e i s some f a c t o r in Malta which protects the native population, and t h i s , i t s e e m s , m i g h t w e l l be t h e s a l i n e w a t e r s u p p l y . SPECIAL PLACE OF MILK IN THE DIET: Because of the apparent implication of the dried milk in the Malta outbreaks,special consider~ tion has been given to this matter, not from the point of view of the recognised food value of milk, but from the point of view of its power to neutralise a c i d s i n t h e s t o m a c h . The r e s u l t is that it is concluded that a diet which includes considerable quantities o f m i l k may r e d u c e the acidity of the stomach for long periods, quite apart from the acid requirements for ~he digestion of the remainder of the diet. This is very important since there are many indications that the poliomyelitis v i r u s may be s u s c e p t i b l e to destruction in the stomach where conditions a r e a c i d , b u t on t h e o t h e r h a n d t h e v i r u s may s u r v i v e i n t h e s t o m a c h i f c o n d i t i o n s are less acid. In view of the possible c o n n e c t i o n b e t w e e n m i l k c o n s u m p t i o n and t h e i n c i d e n c e of p o l i o m y e l i tis, the changes in diet in Great Britain h a v e b e e n e x a m i n e d a s b e t w e e n 1938 and 1947 and 1954, as have world trends of milk consumption in eight other countries. B e t w e e n 1938 and 1 9 4 7 , ac-

cording to official information, one o f t h e m a j o r c h a n g e s i n t h e d i e t i n G r e a t B r i t a i n was an i n c r e a s e d m i l k c o n s u m p t i o n and a d e c r e a s e d m e a t c o n s u m p t i o n , and i t i s p o s s i b l e t o d e m o n s t r a t e mathematically that there is a definite correlation between the incidence of poliomyelitis and milk consumption in the total of nine countries which have been reviewed, S a b i n ( 1 9 5 1 ) and G e b h a r d and B a c h t o l d ( 1 9 5 3 ) h a v e f o u n d t h a t t h e y w e r e o n l y able regularly t o i n f e c t some m o n k e y s w i t h p o l i o m y e l i t i s by t h e o r a l r o u t e ( b y f e e d i n g ) on c o n d i t i o n o f m a k i n g them take milk or milk/cream (or similar) with or before the virus. FIELD

INVESTIGATION:

The foregoing inquiry and discussion suggest that any investigation in the field should be directed to elucidating those factors in the human environment and diet which may decrease the acidity of the stomach, and in particular, low salt intake, vegetarian diets and high milk consumption. With this in mind an investigation has been made of the habits and diets of carefully selected families wherein there had been 55 cases of poliomyelitis (46 paralytic, 9 nonparalytic). (The cases included two deaths and two instances of two cases in one family). The findings for the 55 cases of poliomyelitis have been compared with the findings for 55 members of the same families who did not contract poliomyelitis paired exactly according to age and sex. In addition the 55 cases were compared with 132 members of the same families in the same age groups as the cases, but ,ith a different age distribution.

III.

S U M M A R Y

The result of the field

investigation

A) THOSE WLI0 DID CONTRACT

A N D

C O N C L U S I O N S

in Essex showed that with some exceptions:

PARALYTIC POLIOMYELITIS

(1) Usually put little or no salt on their food (or are otherwise to be salt depleted) and/or

(2) Usually consume large quantities of milk or milk products ice cream) (a total of more than one pint per day)

and/or (3) Usually eat little or no meat

(i.e.

likely

(including

are "vegetarians")

B) THOSE WHO DID NOT CONTRACT PARALYTIC POLIOMYELITIS (1) Usually put at least an average not likely to be salt depleted and/or

(2) Usually do not consume milk etc. per day

and/or

(3)

Usually rians)

eat

at

least

an a v e r a g e

amount

of salt on their food andwere

in quantities

exceeding half a pint

amount o f m e a t ( a n d a r e n o t

vegeta-

It is concluded that salt depletion and a diet which reduces the acidity of the stomach are important factors in poliomyelitis. There may be other factors connected with the diets described. The environmental factors described satisfy all the requirements enumerated in the Introduction. I commend these findings vention of poliomyelitis.

Reference:

to the earnest consideration

F.A.

Irving:

of all who are interested

"The Environmental Approach of Poliomyelitis (1956)"

in the

to the Prevention

pre-