218
THE SPREAD OF DISEASE — SOME IMPORTANT PROBLEMS IN THE LATTER YEARS OF THE TWENTIETH CENTURY
G. C. COOK, M.D., D.SC., F.R.C.P., Honorary Consultant Physician, Hospital for Tropical HIS account will be confined to a number of of viral, bacterial and parasitic
diseases origin
which in a world context are major health moment, and could well become even greater hazards in future years if adequate awareness of their potential consequences is ignored. A comprehensive account under this heading would deal not only with infective diseases but also conditions such as obesity, coronary and cerebral vascular disease, diabetes mellitus and bronchial carcinoma which are largely associated with affluence, higher social standards and living conditions of the &dquo;western world&dquo;. Such diseases have already arrived, and are spreading rapidly, in the oil-rich nations of the Middle-East but are still some way off in the truly &dquo;third world&dquo; countries. Of infectious diseases, those caused by some viruses afford far and away the greatest threat because treatment of the resulting conditions is still very unsatisfactory. However, although bacterial and parasitic infections are in many cases brought under control with adequate chemotherapy, due to inadequate publichealth and preventive methods, together with the development of resistance of both organism and/or -vector to previously effective agents, serious problems remain and are in some cases increasing in size and
problems
at the
complexity. This account will deal first with virus diseases which especially important health hazards, and then with some bacterial and parasitic diseases which still pose problems in a world medical context. are
Poliomyelitis In the years after the Second World War there were up 8,000 cases of poliomyelitis annually in the United Kingdom. Following the development of effective and virtually safe vaccines, the incidence of that disease had fallen between 1972 and 1975 to 3-6 per year. However, in 1976 there were 8 notifications in patients from 7 months to 41 years. That suggests that the disease might be becoming more prevalent although it is true that little can be deduced from a single incidence rate. Poliomyelitis is a virus disease spread by the orofaecal route and it has an incubation of 3-21 days.’1 Following involvement of the pharynx and small intestine, the virus replicates in lymph glands and following that a viraemia gives rise to a sore throat, headaqhes and gastro-intestinal symptoms. In approximately one per cent of those paralysis occurs; the incidence seems to increase with advancing age. §g Obviously, in 1977 poliomyelitis is not a health hazard in the United Kingdom. However, the to
°
three sero-types of very low protection rate has been shown in 16-18 year old police cadets. The lesson to be gained from this disease, therefore, is that vaccination must be continued both in children in the United Kingdom and also in individuals (children and adults) going abroad for holidays or other reasons. Poliomyelitis, like many tropical diseases, has now become largely localized in tropical countries. This is due to inadequate public health facilities in those countries and has nothing to do with the climate. Poliomyelitis in 1977 is still a major problem in the &dquo;third world&dquo;, despite the fact that the means are available to prevent it.
Glasgow had immunity to all poliomyelitis, and more recently
a
Infant gastro-enteritis In all of the &dquo;third world&dquo; countries, one of the major of infant mortality is gastro-enteritis. Infant gastro-enteritis is also a major problem in the United Kingdom. Until a few years ago it was impossible to isolate a pathogen from 70-80 per cent of cases. Over the last few years there have been considerable advances in this field. Rotaviruses have been shown to be associated with many cases,2 and the Norwalk virus has been incriminated in &dquo;winter vomiting disease&dquo;. Certain strains of Escherichia coli, which produce two separate enterotoxins, have also been shown to be responsible for acute diarrhoea in children,3 and also in Traveller’s diarrhoea.4 The toxins exert a direct action on the surface of the intestinal cells (&dquo;enterocytes&dquo;) producing a flux of water and electrolytes towards the lumen of the small intestine. These diseases are usually spread by the oro-faecal route and obviously depend on adequate public health methods for their control. With the recognition of causative agents, the way should be clear for effective vaccines in the future. causes
Virus
hepatitis Although not usually regarded as a tropical disease, virus hepatitis has always been a major health hazard to travellers in tropical areas,5 as well as indigenous populations in the &dquo;third world&dquo;. It has also caused significant morbidity and mortality in the United Kingdom. Despite recognition during the Second World War that the disease almost certainly had a viral cause, progress with prevention and control of the disease has been extremely slow. Recent work associating one form f the disease (hepatitis B) with Australia antigen HB,AG and e antigens) has, however, set the scene for a major breakthrough with respect to prevention of the ðisease.6 There are still substantial problems especially with regard to the short-incubation period type of virus hepatitis (type A). Furthermore, it has recently become clear that some cases of virus hepatitis are caused by neither type A nor type B viruses (non-A
major QHbsAg,
fact that the disease occurs at all indicates that vaccination procedures have not been adequately carried out. It shows that much complacency has resulted from the gross fall in its incidence rate over the last two decades. In 1973, only 50 per cent of pre-school children in
Diseases
Downloaded from rsh.sagepub.com at MOUNT ALLISON UNIV on June 11, 2015
219 type C hepatitis). this is a disease which is often spread by the oro-faecal route. However, there are other methods of spread. Thus blood-transfusion with blood from an infected individual, sharing the same syringe in drugaddicts, and even sexual (both hetero- and homo-) contact with an infected individual’ are amongst the methods of transmission now recognized. Gamma globulin is highly effective in the prophylactic treatment of the disease. However, supplies are both limited and costly. It seems wise therefore to limit its use to travellers who are going to areas with a high endemic rate of virus A infection (i.e. the &dquo;third world&dquo;), and also in the limitation of epidemics. Preliminary results are now available of 8 more specific vaccine preparations for virus hepatitis.8 non-B,
nor
Again
Lassa, Marburg and Ebola diseases
Many articles in the popular press have drawn attention recently recognized virus diseases, all of which originated in the African continent. Each of them has a significant mortality rate; in the case of Lassa fever that has undoubtedly been exaggerated, but it is extremely high with Marburg and the very newly recognized Ebola virus disease.9 Whether these are new diseases due to a recent mutation or whether they have for long been present in Africans (and/or vectors) in to these three
rural Africa is not yet clear. The evidence as far as Lassa fever is concerned is that the disease had certainly been present long before the first recognition of it as a distinct entity in 1969.10 At present there are no satisfactory vaccines for this group of diseases. The only remedy available is convalescent serum; although there is a clinical suggestion that that is of value there is as yet no scientific evidence of that. With rapid air travel and the probability that Marburg and Ebola disease can be readily transmitted by person-to-person contact (the evidence for that in Lassa fever is far less satisfactory) the potential hazards associated with this group of diseases are obvious.
’
I I
I
Rabies A further example of a disease which presents a possible hazard to the population of the United Kingdom is rabies. Although originally endemic in the United Kingdom, for several decades, owing largely to adequate public health measures, the disease has not been a problem. As with so many other virus diseases, including poliomyelitis, it is very commonly encountered in tropical countries and indeed there are few countries in the world which are free of the disease. Now, the disease is widely spread on the continent of Europe&dquo; 11 and affects especially the red fox. The introduction of a single rabid animal to the United Kingdom could easily lead to the beginning of an explosive focus. Domestic animals are not at present immunized against rabies and are therefore totally susceptible. A good case can be made for starting prophylactic immunization. Exclusion of the disease is therefore, at present, entirely dependent on the strict application of animal importation regulations.12 Fortunately, important advances are being made with regard to vaccines for use in man’3 14 IS. Newer preparations make use of human diploid cells rather than neural cells, and seem to afford good protection both before and after exposure. Rabies therefore is a further example of a disease which in the United Kingdom must be constantly kept at the forefront in preventive medicine if a major spread is to be avoided.
BACTERIAL INFECTIONS THE UNKNOWN is usually more alarming than the known! At present, therefore, virus diseases, often with totally inadequate known methods of prevention and cure, dominate the scene regarding spread of disease. That does not exclude the importance of continued awareness of the possible dangers of bacterial infections. Two examples of such diseases which are occasionally encountered in the United Kingdom are typhoid and cholera. In 1975 for example, there were 180 imported cases of typhoid infection.’6 Much could be written on the continuing importance of tuberculosis in the ’third world’ countries; in the United Kingdom it is largely under control.
Typhoid Despite the fact that treatment for this disease, caused by Salmonella typhi, is now fairly well worked out, typhoid fever still carries a significant mortality rate. In recent years, cases diagnosed in the United Kingdom were virtually all contracted abroad. Many have been in travellers to the Indian subcontinent, although some have originated in the Near East, Far East and Africa. A significant number also have been in holiday-makers in Europe, especially Spain.
Present antibiotic treatment is either with chloram-
phenicol, &dquo;Septrin&dquo; (trimethoprim and sulphamethoxazole) or the newer penicillin derivatives (especially amoxycillin). Despite a number of clinical trials in various parts of the world there is still no general agreement upon the best therapeutic agent. Obviously food-handlers are especially important in this disease, as they are in bacillary dysentery, and they must be prevented from working until there is adequate evidence of a complete cuie. Cholera The Middle-East, the Indian subcontinent and the Far East are the areas of the world where cholera is especially common. Despite several outbreaks the disease has not become endemic (for reasons that are largely obscure) on the African continent&dquo; ’8. There is evidence to show that the introduction of the disease (the El Tor variety) to West Africa was by air travel; that again illustrates that that mode of transport is now a major method of spreading disease from country to country, and indeed continent to continent. Added to the basic epidemiology of the disease, i.e. transmission by contaminated water supplies, so admirably demonstrated by John Snow in 1849, must now be added therefore this new route in the spread of the disease. Vaccination against cholera was abandoned as a pre-requisite for entry by many countries after the recommendation by the 26th World Health Assembly in 1973 that it was of limited public-health value’9. However a number of countries are still enforcing this rule especially in the Middle-East. Regarding treatment of the disease, major advances have been made over the last decade2°. That the enterotoxin, mediated by cyclic A.M.P., has a direct effect on the enterocyte, without interfering with morphological integrity of the cell, is now clear. Furthermore, perfusion studies have shown that if oral fluids containing glucose and/or glycine at certain concentrations (eg. 120 m-mole 1-’) are presented to the enterocyte, absorption, accompanied by sodium ions and water occurs. Such fluids given orally can thus rehydrate the patient in a very high proportion of cases. There is thus no reason why intravenous fluids should be required, or why death should occur in this disease. -
Downloaded from rsh.sagepub.com at MOUNT ALLISON UNIV on June 11, 2015
220 PARASITIC INFECTIONS have an parasitic effective form of treatment. However, there are a number of exceptions. Malaria is returning to many areas of the world where it had previously been eradicated. That is due to a number of reasons, amongst which disregard for public-health standards for one reason or another, and resistance of the malarial parasite or its vector to the appropriate chemotherapeutic agent or chemical, are important. Schistosomiasis too is an example of a disease which is rapidly spreading, especially on the African continent, owing to an increase in irrigation schemes and damming of rivers with the production of large areas of stagnant or
OVERALL,
slow-moving
MOST
diseases
now
water.
Malaria In the United Kingdom in 1975 there were 750 cases of malaria diagnosed&dquo;. Most were caused by Plasmodium vivax usually obtained in the Indian subcontinent. The majority of P. falciparum infections were contracted in Africa. There is very good evidence that for a variety of reasons, malaria is increasing more rapidly than in the past in the United Kingdom2’. Amongst important routes of infection are blood-transfusions22 and infected syringes used by drug-addicts. In a world context, the disease has recurred, and is a major problem in several areas, including Sri Lanka, which was previously cleared of the disease, and India, which has now a rapidly increasing incidence of the disease23. Drug-resistant malaria now presents a very serious problem. Several recent reviews have25 been largely devoted to that aspect of the disease24 but the problem is very far from solved. To date most of the resistance has occurred in the Far-East. That problem in Africa has been so far confined to limited areas. However, the fact remains that malaria is on the increase in a world context. Formerly a disease with a distribution involving many temperate areas as well as the tropics, including the United Kingdom, intensive efforts to eradicate it diminished its distribution very substantially. Now in 1977 the situation is deteriorating, and it is worth remembering that in Africa alone one hundred million people are affected, of whom one million die each year. Although a human vaccine is on the horizon, &dquo;it would be wrong to conclude that a malaria vaccine is just around the corner&dquo;, as was remarked in a recent editoria126.
Schistosomiasis
the serious drawback is severe confusion in the presence of portal-systemic shunting. Hycanthone (’Etrenol’) has met with a degree of success, but is certainly not without hepato-toxicity and there are reports of hepatic failure associated with that com-
pound. CONCLUSION COMPLACENCY IS an extremely dangerous factor in 1977 in the problems facing the world’s disease pattern. It is true that newly described virus diseases, in some probably due to mutations of viruses previously in existence, are associated with substantial mortality rates. However, many known diseases have well established forms of prophylaxis and treatment. Only if those measures are strictly and intelligently applied can the spread of those diseases be halted. Medical and scientific literature is full of descriptions and applications of measures to combat the spread of disease. By positive action and implementation of those observations and data the means to prevent much human suffering and unnecessary morbidity and mortality are at our
disposal.
REFERENCES 1 SPILLANE, J. D. (1973) Ed., Tropical Neurology, Oxford University Press, London. The Lancet (1975), 2 , 257-259. Rotaviruses of man and animals. 1 3 RYDER, R. W., WACHSMUTH, I. K., BUXTON, A. E., EVANS, D. G., DUPONT, H. L., MASON, E. and BARRETT, F. F. (1976). Infantile diarrhoea produced by heat-stable enterotoxigenic Escherichia coli. New England Journal of Medicine, 295, 849-853. 4 MERSON, M. H., MORRIS, G. K., SACK, D. A., WELLS, J. G., FEELEY, J. C., SACK, R. B., CREECH, W. B., KAPIKIAN, A. Z. and GANGAROSA, E. J. (1976) Traveller’s diarrhoea in Mexico. A prospective study of physicians and family members attending a congress. New England Journal of Medicine, 294, 1299-1305. 5 British Medical Journal (1977) 1, 189-190. Tourist Hepatitis. 6 WOOLF, I., and WILLIAMS, R. (1977). Acute viral hepatitis. British Journal of Hospital Medicine, 17 , 117-124. 7 HEATHCOTE, J. and SHERLOCK, S. (1973). Spread of acute type-B hepatitis in London, The Lancet, 1, 1468-1470. 8 MAUPAS, P., GOUDEAU, A., COURSAGET, P., DRUCKER, J., and BAGROS, P. (1976). The Lancet, 1, 1367-1370. The Lancet, (1977) 1, 581-582. After Marburg, Ebola 9 10 Memorandum on Lassa fever (1976). Department of Health and Social Security and the Welsh Office. H.M.S.O. British Journal of Hospital Medicine (1976), 16, 197. Rabies. 11 12 BAHMANYAR, M. (1976). Measures against rabies. British Journal of Hospital Medicine, 16, 199. British Medical Journal, 1, 45-46 (1974) Rabies vaccination in 13 ...
man. 14
CRICK, J. and BROWN, F. (1976). Rabies virus and the problems of
rabies vaccination in man. Transactions of the Royal Society of Medicine and Hygiene, 70, 196-201. 15 TYRELL, D. (1976). Vaccination against rabies. Transactions of the Royal Society of Tropical Medicine and Hygiene, 70, 202-204. 16 British Medical Journal , (1976), 1 232. Some imported infections. 17 BARUA, D. (1972). The global epidemiology of cholera in recent years. Proceedings of the Royal Society of Medicine, 65, 423-428. The Lancet, (1973), 2, 601-602. SNOW (1849) on cholera (1973). 18 19 The Lancet (1973), , 1369-1370. Cholera vaccine and interna1 tional travel. 20 The Lancet (1972), 2, 167-168. New light on cholera. 21 BRUCE-CHWATT, L. J., SOUTHGATE, B. A., and DRAPER, C. C. (1974). Malaria in the United Kingdom. British Medical Journal, 2, 707-711. 22 The Lancet (1973), 1, 32: Blood-transfusion and tropical disease. 23 W. H. O. Chronicle (1974), , 479-487. The malaria situation in 28 1973. 24 PETERS, W. (1971). Malaria: Chemoprophylaxis and Chemotherapy. British Medical Journal, 2, 95-98. 25 HALL, A. P. (1976). The treatment of malaria. British Medical Journal, 1 , 323-328. The Lancet (1977) 1 26 , 130-131. Continuous culture of humanmalaria parasites. 27 STANLEY, N. F., and ALPERS, M. P. (Ed). (1975). Man-made lakes and Human Health. Academic Press, New York. British Medical Journal (1975), 3, 451. Circulating antibodies and 28 antigens in schistosomiasis.
Tropical
During 1975, approximately 180 cases of schistosomiasis were notified in the United Kingdom’6. About half were due to Schistosoma mansoni, about one quarter to S. haematobium and in the remainder the diagnosis was based on serology and a species diagnosis was not possible. Most of those infections were acquired in Africa, often by holiday-makers, and about 10 per cent originated in the Near-East. The disease is rapidly increasing, especially in Africa. Efforts to control the disease have so far not met with much success27 28. Theoretically, the methods of control are: 1. mass treatment of all human cases, 2. reduction or prevention of fresh water pollution, which depends very largely on an intelligent and co-operative human population, 3. prevention of human contact with water containing the infective stage, and 4. elimination of the snails which are essential for transmission to man. Successes with molluscicides have never been anything like 100 per cent. For treatment of the human disease, Niridazole (’Ambilhar’) is now widely used although
Downloaded from rsh.sagepub.com at MOUNT ALLISON UNIV on June 11, 2015
THE SPREAD OF DISEASE — SOME IMPORTANT PROBLEMS IN THE LATTER YEARS OF THE TWENTIETH CENTURY
G. C. COOK, M.D., D.SC., F.R.C.P., Honorary Consultant Physician, Hospital for Tropical HIS account will be confined to a number of of viral, bacterial and parasitic
diseases origin
which in a world context are major health moment, and could well become even greater hazards in future years if adequate awareness of their potential consequences is ignored. A comprehensive account under this heading would deal not only with infective diseases but also conditions such as obesity, coronary and cerebral vascular disease, diabetes mellitus and bronchial carcinoma which are largely associated with affluence, higher social standards and living conditions of the &dquo;western world&dquo;. Such diseases have already arrived, and are spreading rapidly, in the oil-rich nations of the Middle-East but are still some way off in the truly &dquo;third world&dquo; countries. Of infectious diseases, those caused by some viruses afford far and away the greatest threat because treatment of the resulting conditions is still very unsatisfactory. However, although bacterial and parasitic infections are in many cases brought under control with adequate chemotherapy, due to inadequate publichealth and preventive methods, together with the development of resistance of both organism and/or -vector to previously effective agents, serious problems remain and are in some cases increasing in size and
problems
at the
complexity. This account will deal first with virus diseases which especially important health hazards, and then with some bacterial and parasitic diseases which still pose problems in a world medical context. are
Poliomyelitis In the years after the Second World War there were up 8,000 cases of poliomyelitis annually in the United Kingdom. Following the development of effective and virtually safe vaccines, the incidence of that disease had fallen between 1972 and 1975 to 3-6 per year. However, in 1976 there were 8 notifications in patients from 7 months to 41 years. That suggests that the disease might be becoming more prevalent although it is true that little can be deduced from a single incidence rate. Poliomyelitis is a virus disease spread by the orofaecal route and it has an incubation of 3-21 days.’1 Following involvement of the pharynx and small intestine, the virus replicates in lymph glands and following that a viraemia gives rise to a sore throat, headaqhes and gastro-intestinal symptoms. In approximately one per cent of those paralysis occurs; the incidence seems to increase with advancing age. §g Obviously, in 1977 poliomyelitis is not a health hazard in the United Kingdom. However, the to
°
three sero-types of very low protection rate has been shown in 16-18 year old police cadets. The lesson to be gained from this disease, therefore, is that vaccination must be continued both in children in the United Kingdom and also in individuals (children and adults) going abroad for holidays or other reasons. Poliomyelitis, like many tropical diseases, has now become largely localized in tropical countries. This is due to inadequate public health facilities in those countries and has nothing to do with the climate. Poliomyelitis in 1977 is still a major problem in the &dquo;third world&dquo;, despite the fact that the means are available to prevent it.
Glasgow had immunity to all poliomyelitis, and more recently
a
Infant gastro-enteritis In all of the &dquo;third world&dquo; countries, one of the major of infant mortality is gastro-enteritis. Infant gastro-enteritis is also a major problem in the United Kingdom. Until a few years ago it was impossible to isolate a pathogen from 70-80 per cent of cases. Over the last few years there have been considerable advances in this field. Rotaviruses have been shown to be associated with many cases,2 and the Norwalk virus has been incriminated in &dquo;winter vomiting disease&dquo;. Certain strains of Escherichia coli, which produce two separate enterotoxins, have also been shown to be responsible for acute diarrhoea in children,3 and also in Traveller’s diarrhoea.4 The toxins exert a direct action on the surface of the intestinal cells (&dquo;enterocytes&dquo;) producing a flux of water and electrolytes towards the lumen of the small intestine. These diseases are usually spread by the oro-faecal route and obviously depend on adequate public health methods for their control. With the recognition of causative agents, the way should be clear for effective vaccines in the future. causes
Virus
hepatitis Although not usually regarded as a tropical disease, virus hepatitis has always been a major health hazard to travellers in tropical areas,5 as well as indigenous populations in the &dquo;third world&dquo;. It has also caused significant morbidity and mortality in the United Kingdom. Despite recognition during the Second World War that the disease almost certainly had a viral cause, progress with prevention and control of the disease has been extremely slow. Recent work associating one form f the disease (hepatitis B) with Australia antigen HB,AG and e antigens) has, however, set the scene for a major breakthrough with respect to prevention of the ðisease.6 There are still substantial problems especially with regard to the short-incubation period type of virus hepatitis (type A). Furthermore, it has recently become clear that some cases of virus hepatitis are caused by neither type A nor type B viruses (non-A
major QHbsAg,
fact that the disease occurs at all indicates that vaccination procedures have not been adequately carried out. It shows that much complacency has resulted from the gross fall in its incidence rate over the last two decades. In 1973, only 50 per cent of pre-school children in
Diseases
Downloaded from rsh.sagepub.com at MOUNT ALLISON UNIV on June 11, 2015
219 type C hepatitis). this is a disease which is often spread by the oro-faecal route. However, there are other methods of spread. Thus blood-transfusion with blood from an infected individual, sharing the same syringe in drugaddicts, and even sexual (both hetero- and homo-) contact with an infected individual’ are amongst the methods of transmission now recognized. Gamma globulin is highly effective in the prophylactic treatment of the disease. However, supplies are both limited and costly. It seems wise therefore to limit its use to travellers who are going to areas with a high endemic rate of virus A infection (i.e. the &dquo;third world&dquo;), and also in the limitation of epidemics. Preliminary results are now available of 8 more specific vaccine preparations for virus hepatitis.8 non-B,
nor
Again
Lassa, Marburg and Ebola diseases
Many articles in the popular press have drawn attention recently recognized virus diseases, all of which originated in the African continent. Each of them has a significant mortality rate; in the case of Lassa fever that has undoubtedly been exaggerated, but it is extremely high with Marburg and the very newly recognized Ebola virus disease.9 Whether these are new diseases due to a recent mutation or whether they have for long been present in Africans (and/or vectors) in to these three
rural Africa is not yet clear. The evidence as far as Lassa fever is concerned is that the disease had certainly been present long before the first recognition of it as a distinct entity in 1969.10 At present there are no satisfactory vaccines for this group of diseases. The only remedy available is convalescent serum; although there is a clinical suggestion that that is of value there is as yet no scientific evidence of that. With rapid air travel and the probability that Marburg and Ebola disease can be readily transmitted by person-to-person contact (the evidence for that in Lassa fever is far less satisfactory) the potential hazards associated with this group of diseases are obvious.
’
I I
I
Rabies A further example of a disease which presents a possible hazard to the population of the United Kingdom is rabies. Although originally endemic in the United Kingdom, for several decades, owing largely to adequate public health measures, the disease has not been a problem. As with so many other virus diseases, including poliomyelitis, it is very commonly encountered in tropical countries and indeed there are few countries in the world which are free of the disease. Now, the disease is widely spread on the continent of Europe&dquo; 11 and affects especially the red fox. The introduction of a single rabid animal to the United Kingdom could easily lead to the beginning of an explosive focus. Domestic animals are not at present immunized against rabies and are therefore totally susceptible. A good case can be made for starting prophylactic immunization. Exclusion of the disease is therefore, at present, entirely dependent on the strict application of animal importation regulations.12 Fortunately, important advances are being made with regard to vaccines for use in man’3 14 IS. Newer preparations make use of human diploid cells rather than neural cells, and seem to afford good protection both before and after exposure. Rabies therefore is a further example of a disease which in the United Kingdom must be constantly kept at the forefront in preventive medicine if a major spread is to be avoided.
BACTERIAL INFECTIONS THE UNKNOWN is usually more alarming than the known! At present, therefore, virus diseases, often with totally inadequate known methods of prevention and cure, dominate the scene regarding spread of disease. That does not exclude the importance of continued awareness of the possible dangers of bacterial infections. Two examples of such diseases which are occasionally encountered in the United Kingdom are typhoid and cholera. In 1975 for example, there were 180 imported cases of typhoid infection.’6 Much could be written on the continuing importance of tuberculosis in the ’third world’ countries; in the United Kingdom it is largely under control.
Typhoid Despite the fact that treatment for this disease, caused by Salmonella typhi, is now fairly well worked out, typhoid fever still carries a significant mortality rate. In recent years, cases diagnosed in the United Kingdom were virtually all contracted abroad. Many have been in travellers to the Indian subcontinent, although some have originated in the Near East, Far East and Africa. A significant number also have been in holiday-makers in Europe, especially Spain.
Present antibiotic treatment is either with chloram-
phenicol, &dquo;Septrin&dquo; (trimethoprim and sulphamethoxazole) or the newer penicillin derivatives (especially amoxycillin). Despite a number of clinical trials in various parts of the world there is still no general agreement upon the best therapeutic agent. Obviously food-handlers are especially important in this disease, as they are in bacillary dysentery, and they must be prevented from working until there is adequate evidence of a complete cuie. Cholera The Middle-East, the Indian subcontinent and the Far East are the areas of the world where cholera is especially common. Despite several outbreaks the disease has not become endemic (for reasons that are largely obscure) on the African continent&dquo; ’8. There is evidence to show that the introduction of the disease (the El Tor variety) to West Africa was by air travel; that again illustrates that that mode of transport is now a major method of spreading disease from country to country, and indeed continent to continent. Added to the basic epidemiology of the disease, i.e. transmission by contaminated water supplies, so admirably demonstrated by John Snow in 1849, must now be added therefore this new route in the spread of the disease. Vaccination against cholera was abandoned as a pre-requisite for entry by many countries after the recommendation by the 26th World Health Assembly in 1973 that it was of limited public-health value’9. However a number of countries are still enforcing this rule especially in the Middle-East. Regarding treatment of the disease, major advances have been made over the last decade2°. That the enterotoxin, mediated by cyclic A.M.P., has a direct effect on the enterocyte, without interfering with morphological integrity of the cell, is now clear. Furthermore, perfusion studies have shown that if oral fluids containing glucose and/or glycine at certain concentrations (eg. 120 m-mole 1-’) are presented to the enterocyte, absorption, accompanied by sodium ions and water occurs. Such fluids given orally can thus rehydrate the patient in a very high proportion of cases. There is thus no reason why intravenous fluids should be required, or why death should occur in this disease. -
Downloaded from rsh.sagepub.com at MOUNT ALLISON UNIV on June 11, 2015
220 PARASITIC INFECTIONS have an parasitic effective form of treatment. However, there are a number of exceptions. Malaria is returning to many areas of the world where it had previously been eradicated. That is due to a number of reasons, amongst which disregard for public-health standards for one reason or another, and resistance of the malarial parasite or its vector to the appropriate chemotherapeutic agent or chemical, are important. Schistosomiasis too is an example of a disease which is rapidly spreading, especially on the African continent, owing to an increase in irrigation schemes and damming of rivers with the production of large areas of stagnant or
OVERALL,
slow-moving
MOST
diseases
now
water.
Malaria In the United Kingdom in 1975 there were 750 cases of malaria diagnosed&dquo;. Most were caused by Plasmodium vivax usually obtained in the Indian subcontinent. The majority of P. falciparum infections were contracted in Africa. There is very good evidence that for a variety of reasons, malaria is increasing more rapidly than in the past in the United Kingdom2’. Amongst important routes of infection are blood-transfusions22 and infected syringes used by drug-addicts. In a world context, the disease has recurred, and is a major problem in several areas, including Sri Lanka, which was previously cleared of the disease, and India, which has now a rapidly increasing incidence of the disease23. Drug-resistant malaria now presents a very serious problem. Several recent reviews have25 been largely devoted to that aspect of the disease24 but the problem is very far from solved. To date most of the resistance has occurred in the Far-East. That problem in Africa has been so far confined to limited areas. However, the fact remains that malaria is on the increase in a world context. Formerly a disease with a distribution involving many temperate areas as well as the tropics, including the United Kingdom, intensive efforts to eradicate it diminished its distribution very substantially. Now in 1977 the situation is deteriorating, and it is worth remembering that in Africa alone one hundred million people are affected, of whom one million die each year. Although a human vaccine is on the horizon, &dquo;it would be wrong to conclude that a malaria vaccine is just around the corner&dquo;, as was remarked in a recent editoria126.
Schistosomiasis
the serious drawback is severe confusion in the presence of portal-systemic shunting. Hycanthone (’Etrenol’) has met with a degree of success, but is certainly not without hepato-toxicity and there are reports of hepatic failure associated with that com-
pound. CONCLUSION COMPLACENCY IS an extremely dangerous factor in 1977 in the problems facing the world’s disease pattern. It is true that newly described virus diseases, in some probably due to mutations of viruses previously in existence, are associated with substantial mortality rates. However, many known diseases have well established forms of prophylaxis and treatment. Only if those measures are strictly and intelligently applied can the spread of those diseases be halted. Medical and scientific literature is full of descriptions and applications of measures to combat the spread of disease. By positive action and implementation of those observations and data the means to prevent much human suffering and unnecessary morbidity and mortality are at our
disposal.
REFERENCES 1 SPILLANE, J. D. (1973) Ed., Tropical Neurology, Oxford University Press, London. The Lancet (1975), 2 , 257-259. Rotaviruses of man and animals. 1 3 RYDER, R. W., WACHSMUTH, I. K., BUXTON, A. E., EVANS, D. G., DUPONT, H. L., MASON, E. and BARRETT, F. F. (1976). Infantile diarrhoea produced by heat-stable enterotoxigenic Escherichia coli. New England Journal of Medicine, 295, 849-853. 4 MERSON, M. H., MORRIS, G. K., SACK, D. A., WELLS, J. G., FEELEY, J. C., SACK, R. B., CREECH, W. B., KAPIKIAN, A. Z. and GANGAROSA, E. J. (1976) Traveller’s diarrhoea in Mexico. A prospective study of physicians and family members attending a congress. New England Journal of Medicine, 294, 1299-1305. 5 British Medical Journal (1977) 1, 189-190. Tourist Hepatitis. 6 WOOLF, I., and WILLIAMS, R. (1977). Acute viral hepatitis. British Journal of Hospital Medicine, 17 , 117-124. 7 HEATHCOTE, J. and SHERLOCK, S. (1973). Spread of acute type-B hepatitis in London, The Lancet, 1, 1468-1470. 8 MAUPAS, P., GOUDEAU, A., COURSAGET, P., DRUCKER, J., and BAGROS, P. (1976). The Lancet, 1, 1367-1370. The Lancet, (1977) 1, 581-582. After Marburg, Ebola 9 10 Memorandum on Lassa fever (1976). Department of Health and Social Security and the Welsh Office. H.M.S.O. British Journal of Hospital Medicine (1976), 16, 197. Rabies. 11 12 BAHMANYAR, M. (1976). Measures against rabies. British Journal of Hospital Medicine, 16, 199. British Medical Journal, 1, 45-46 (1974) Rabies vaccination in 13 ...
man. 14
CRICK, J. and BROWN, F. (1976). Rabies virus and the problems of
rabies vaccination in man. Transactions of the Royal Society of Medicine and Hygiene, 70, 196-201. 15 TYRELL, D. (1976). Vaccination against rabies. Transactions of the Royal Society of Tropical Medicine and Hygiene, 70, 202-204. 16 British Medical Journal , (1976), 1 232. Some imported infections. 17 BARUA, D. (1972). The global epidemiology of cholera in recent years. Proceedings of the Royal Society of Medicine, 65, 423-428. The Lancet, (1973), 2, 601-602. SNOW (1849) on cholera (1973). 18 19 The Lancet (1973), , 1369-1370. Cholera vaccine and interna1 tional travel. 20 The Lancet (1972), 2, 167-168. New light on cholera. 21 BRUCE-CHWATT, L. J., SOUTHGATE, B. A., and DRAPER, C. C. (1974). Malaria in the United Kingdom. British Medical Journal, 2, 707-711. 22 The Lancet (1973), 1, 32: Blood-transfusion and tropical disease. 23 W. H. O. Chronicle (1974), , 479-487. The malaria situation in 28 1973. 24 PETERS, W. (1971). Malaria: Chemoprophylaxis and Chemotherapy. British Medical Journal, 2, 95-98. 25 HALL, A. P. (1976). The treatment of malaria. British Medical Journal, 1 , 323-328. The Lancet (1977) 1 26 , 130-131. Continuous culture of humanmalaria parasites. 27 STANLEY, N. F., and ALPERS, M. P. (Ed). (1975). Man-made lakes and Human Health. Academic Press, New York. British Medical Journal (1975), 3, 451. Circulating antibodies and 28 antigens in schistosomiasis.
Tropical
During 1975, approximately 180 cases of schistosomiasis were notified in the United Kingdom’6. About half were due to Schistosoma mansoni, about one quarter to S. haematobium and in the remainder the diagnosis was based on serology and a species diagnosis was not possible. Most of those infections were acquired in Africa, often by holiday-makers, and about 10 per cent originated in the Near-East. The disease is rapidly increasing, especially in Africa. Efforts to control the disease have so far not met with much success27 28. Theoretically, the methods of control are: 1. mass treatment of all human cases, 2. reduction or prevention of fresh water pollution, which depends very largely on an intelligent and co-operative human population, 3. prevention of human contact with water containing the infective stage, and 4. elimination of the snails which are essential for transmission to man. Successes with molluscicides have never been anything like 100 per cent. For treatment of the human disease, Niridazole (’Ambilhar’) is now widely used although
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