Setting for Action
Dietary Management of Infection
Dietary Prevention of Infection
Infectious Disease Control
The interaction of infection and nutrition as a cause of mortality and severe morbidity in children is well documented, and has a disproportionately high impact on lower socio-economic groups. Addressing infectious disease is thus a second essential part of actions to improve nutrition. Malnutrition and infection form a cycle. Here, nutrition actions as they affect infectious disease in terms of prevention and management are discussed in some detail. Infectious disease control itself is so important - both in its own right and in relation to nutrition - that it is also included under this heading.
Because malnutrition and infection interact and are closely linked, it is relevant to talk about a "malnutrition-infection complex". Of the about 13 million infants and children who currently die each year in developing countries, most of the deaths are due to infections and/or parasitic disease, and many if not most of the children die malnourished. The malnutrition and infection complex remains the most prevalent public health problem in the world today21.
The principles underlying malnutrition and infection can be summarized as follows. Inadequate dietary intake leads to low nutritional reserves, which are manifested as weight loss or failure of growth in children. Depleted nutritional reserves are associated with a lowering of immunity, probably with almost all nutrient deficiencies. Particularly in protein-energy and vitamin A deficiencies there may be progressive damage to mucosa, lowering resistance to colonization and invasion by pathogens. Lowered immunity and mucosal damage are the major mechanisms by which defences are compromised. Under these circumstances, the incidence, severity, and duration of diseases may be increased. The relative importance of these three factors is not fully worked out under all conditions. The disease processes themselves exacerbate loss of nutrients, both by the host's metabolic response, and by physical loss from the intestine. These factors themselves worsen the malnutrition, leading to further damage to defence mechanisms. At the same time, many diseases are associated with a loss of appetite, and other possible disabilities, cycling back to further lower the dietary intake. While other relationships play a part, these are some of the most important, and account for much of the high morbidity and mortality under circumstances of high exposure to infectious disease and inadequate diet, characterizing many poor communities.
Control of infectious disease, and dietary/nutrition interventions to promote this process, are thus of major importance in cutting into the cycle of malnutrition and infection. Controlling infectious disease through primary health care is a major priority of the health sector. Concern for nutrition only reinforces this priority. It is worth noting that prevention and management of infection is particularly important in malnourished communities: for example, measles immunization would be expected to save more lives in malnourished communities than in those better off.
Dietary interventions during and immediately after infectious disease can affect the course and effects of the disease, and reduce the extent to which nutritional status suffers. Nutrition is thus relevant to disease management. Adequate nutrition maintains immunity and other protection against disease, so that nutritional or dietary interventions can be important in prevention; indeed, it has been claimed that longer-term trends (over decades) towards improved health in many countries are basically due to the preventive effect of better nutrition22.
Interventions during management of infection often fall naturally within the existing concerns of the health sector - as examples in combating anorexia, and in maintaining dietary intake during persistent diarrhoea. Nutritional interventions for prevention may or may not be through the health sector; for example the social services are responsible in some countries.
In sum, policies to improve nutrition necessarily include control of infectious disease. Often, they will reinforce priorities that are already accepted: for example, the prime importance of breastfeeding needs to be promoted through the health and other sectors. Equally, nutrition considerations would support the priority given to environmental sanitation, housing, as well as measures such as immunization, oral rehydration, parasite control, etc. Within these conventional health measures, nutrition considerations may have a part to play in terms of targeting and monitoring and evaluation of outcomes.
Concern with nutrition improvement may be particularly usefully translated into action by emphasis on feasible, usually incremental, actions incorporated within services. These are stressed here, not least because of their obvious relation to nutritional concerns, and the fact that they may get lost sight of in sectoral planning. The scope for action is discussed later as specific strategies for tackling malnutrition and infection in the context of primary health care and its support systems, under three main headings:
- dietary management of infectionGrowth monitoring is important for all three aspects and should be promoted for individual problem detection, for communication with mothers and communities, for assessing progress, and for other reasons23.
- dietary prevention of infection
- infectious disease control to improve nutrition.
While the control of infectious diseases is accorded a high priority within health departments, effective programmes are complex, costly and difficult to implement. Furthermore, to be most effective they require substantial contributions from sectors other than health. Financing of the health sector is traditionally assigned a low priority in developing countries with market economies. Within limited health budgets, a high proportion of funds is allocated to hospital-based curative care, involving major capital and recurrent costs and leaving only minor resources for the development of preventive programmes. Limitations of health infrastructure result in low overall coverage which in turn limits the reach of primary health care programmes and their infectious disease control components.
The control and prevention of infection should be central to health policy in developing countries where infectious disease morbidity is the major component of hospital admission. Primary health care programmes give clear priority to a range of services and activities designed to reduce the incidence and severity of common infections. While infectious disease is a clear priority for the health sector, a number of the principal interventions for its control are the responsibility of other sectors. Adequacy and safety of water supply, sanitation and housing are usually substantially determined by public works departments and local authorities.
The interaction between infection and malnutrition has an overwhelming impact on those who are poorest in social, economic and environmental terms and is the major cause of death, sickness and disability in infants and young children as well as being an important contributor to ill-health and reproductive problems of their mothers. Its occurrence is the single most powerful expression of the biological consequences of poverty and disadvantage. Reduction of the frequency and severity of infection in the long-term requires addressing poverty and deprivation within the broader framework of economic growth and social development. In the context of this paper, such an approach includes the improvement of household food security, environmental hygiene, child caring capacity, and the empowerment of women. These are discussed in sections B and D. Micronutrient deficiency control programmes are covered further in section E.
Dietary management seeks to modify the course and outcome of infection by the improvement of food intake during disease and recovery, particularly in young children. This is applied principally through education programmes enabling mothers and carers to acquire and apply the necessary food resources and skills in an effective manner. The education may be formal, through the school system for example, but importantly includes information and counselling through health care workers. Under a number of circumstances, supplementary food, micronutrient supplements, and technologies such as for fermented and amylase-rich foods may be supplied as part of the services. A brief list of possible actions, related as appropriate to specific common diseases follows.
i) Continuation of breastfeeding during infections This applies to all infections, but with particular force to diarrhoea, measles, respiratory tract infections, and malaria. In children up to four to six months of age, exclusive breastfeeding is recommended. During episodes of diarrhoea, continued exclusive breastfeeding (with increased frequency and duration of feeds if possible) is the most important nutritional aspect of management. If such infants nonetheless become dehydrated, rehydration therapy may be required. When breastfeeding is maintained during diarrhoea, the growth faltering commonly associated with diarrhoea is rarely seen, and the risk of death is minimized. Continued breastfeeding, as required with increased frequency, is also central to the management of other acute infections, such as measles and acute respiratory tract infections, of which pneumonia is the most serious. In children older than four to six months, continued partial breastfeeding is of similar importance, and its continuation during episodes of infection should be emphasized.
ii) Maintenance of diet during infection, especially persistent diarrhoea, including both active and recovery (catch-up) phases Maintaining supplementary foods in young children (above four to six months of age) during the course of infection, and increasing intake during the recovery period, is essential. This is made more difficult by the anorexia that commonly accompanies infectious disease, and by the low energy density of many weaning foods. The mistaken view that is still prevalent in some communities that dietary intake should be restricted during infection is particularly pernicious, and needs to be vigorously counteracted. In this context, not only is encouragement to continue feeding required, but promotion of methods that increase the energy density of palatable diets should be stressed - there is considerable potential for use here of fermented foods (often along traditional lines) and use of amylase-rich flours to reduce bulk. Supply of supplementary foods may also be a means of increasing food intake during these critical periods.
iii) Administration of vitamin A in the management of measles, acute respiratory infections, etc.24 In areas where vitamin A deficiency exists particularly during and in the immediate post-infection phases of measles and respiratory tract infections, vitamin A supplementation has been shown to be effective in reducing case-fatality, preventing further infection and promoting recovery. This may be accomplished by counselling for vitamin A-rich foods in the diet, and often can also be effectively achieved by direct provision of vitamin A supplements.
iv) Use of oral rehydration therapy in treatment of acute diarrhoea This intervention is well known and widely applied, and has relevance to nutrition not only in the management of the disease itself, but very possibly in counteracting anorexia, thus enabling more successful application of the interventions mentioned here. Home-prepared fluids (e.g. gruels) for treating dehydration may be considered.
v) Dietary support in chronic infections With diseases such as tuberculosis, leprosy and AIDS, attention to maintaining adequate dietary intake forms an important part of the management. Methods in young children are similar to those discussed above, including continuation of breastfeeding, and provision of higher energy density and palatable foods, and emphasis on frequency of feeding.
vi) Iron and malaria Malaria is frequently associated with iron-deficiency anaemia, and the interactions are complex. However, current evidence is that oral administration of iron during the treatment of malaria, in moderate doses, is valuable. This will help enhance immunity, and the benefits of oral supplementation are considered to outweigh the risks which are peculiar to malaria since the parasite requires iron for multiplication.
vii) Other micronutrient deficiencies Multiple micronutrient deficiencies are commonly associated with infectious disease and have particularly been implicated in acute respiratory infections (notably zinc, iron, and possibly vitamin D). Due attention to micronutrient status during management is appropriate.
viii) Intestinal parasites Infection with intestinal parasites is frequently associated with malnutrition, and the potential for integrating parasite control and nutrition programmes is clear. In this context, where intestinal parasite infestation is prevalent, parasite control programmes may usefully include food supplementation, and vice versa.
ix) Effective nursing/caring during sickness in the family In effect, many of the interventions discussed here depend upon family members and helpers. To be effective these may need counselling and support to care for sick children during infection, and importantly in the nutritional context to promote their rapid catch-up during the recovery phase. Emphasis on providing the appropriate information through all available channels is required, because this aspect is frequently overlooked in the delivery of health and nutrition programmes.
Dietary prevention seeks to reduce the frequency and severity of infection by ensuring a safe and nutritionally adequate diet and limiting energy expenditure, to protect nutritional status. Good nutritional status prevents infection by a number of mechanisms, notably through the immune system and maintaining the integrity of epithelial tissues. Again, education and information are important means of implementation. Specific interventions through the health system may also be needed. Dietary prevention of infection includes promoting or ensuring the following.
i) Exclusive breastfeeding for four to six months Exclusive breastfeeding helps to prevent diarrhoea by minimizing the infant's exposure to diarrhoeal pathogens, which are common in other foods and in water. At the same time, breast milk provides anti-bacterial activity in the infant's gut, reducing the risk of disease if contaminants should be ingested. Similarly, breastfeeding has direct benefits in preventing other diseases, from acquired passive immunity from the mother. It also probably prevents malnutrition, not only secondarily to diarrhoea, through the cycle of suckling promoting production of maternal milk.
ii) Continued breastfeeding into the second year of life Continued breastfeeding promotes prevention of disease through protection of nutritional status, as well as some continuing direct protection against infectious disease. Indirect effects are also important, through birth spacing.
iii) Satisfactory quality and intake of complementary foods A number of issues arise here, concerning energy density, nutritional value, and food hygiene. It is essential to promote frequent feeding of foods of adequate energy density (including use of amylase-rich flours). Microbial contamination may be reduced using fermented foods. Good feeding practices may be promoted through education, and in some circumstances, perhaps notably in urban areas, special weaning foods may be marketed.
iv) Vitamin A status in relation to measles and respiratory tract infections Vitamin A supplements are indicated in all populations at high risk from measles where vitamin A deficiency exists. Measles precipitates vitamin A deficiency, and the disease is worsened in the deficient individual. There is also accumulating evidence that vitamin A deficiency increases risks of developing respiratory diseases, and that children who are vitamin A deficient are more likely to suffer from chronic ear infections. Thus prevention of vitamin A deficiency is particularly important to reduce the incidence and severity of respiratory tract infections, of which pneumonia is the most serious. In general terms, preventing vitamin A deficiency by dietary improvement, fortification and/or supplementation is expected to ameliorate infectious disease, through effects on immunity and on epithoreal tissues.
v) Prevention of low birth weight Improving women's nutritional status, especially pre- and during pregnancy, is important not only for the nutrition of women but in preventing low birth weight (especially intra-uterine growth retardation) and subsequent likely higher risks of malnutrition, morbidity and mortality in the offspring. A number of interventions to improve women's nutrition are mentioned in section D, and those that are particularly relevant in this context include maternal supplementation, reduction of energy expenditure, and family planning, with particular reference to adolescent mothers. Low birth weight infants are considered to be at particular risk of respiratory tract infections, thus reducing low birth weight may have this specific benefit of reducing RTIs.
vi) Iron and malaria As for management of malaria and anaemia, there are complex issues concerning iron supplementation in malaria endemic areas. In general, oral iron should be administered to all pregnant women under malaria chemoprophylaxis; however this issue does not arise for the population in general, since malaria chemoprophylaxis is no longer recommended on a population basis, at least for young children, in situations where there is inadequate assurance that it can be maintained in the long-term. Where malaria chemoprophylaxis cannot be administered systematically, it is nonetheless expected that iron supplementation under these conditions would be of benefit, due to the immune effect relating to malaria, as well as through improving anaemia. In general, assuring adequate iron status will have widespread public health benefits, reducing anaemia and improving immunity.
Control of infectious diseases which will improve nutrition and have other benefits, is widely described25. The main point to emphasize here is that concern for nutrition inevitably includes priority for infectious disease control.
Controlling infectious diseases involves improving the health environment, and assuring access to adequate health services - indeed all the factors encompassed under the concept of primary health care. In the context of child malnutrition, particular emphasis may be appropriate to programmes of immunization (EPI), controlling respiratory infections, malaria, schistosomiasis, and intestinal parasites. At the same time, promoting the early diagnosis and treatment of infection in children and mothers (especially during pregnancy) by primary care services has a central role. Of the specific disease programmes in relation to malnutrition and young children, those that address diarrhoeal disease, not only acute diarrhoea for which rehydration is important, but also persistent diarrhoea for which dietary management is of particular importance, must be stressed.
Malnutrition and infection can be measured by well-established methods, including anthropometry often as growth monitoring26. Assessing the processes outlined in this section is also relatively straightforward in principle, from service or administrative sources in some cases, otherwise from household surveys. Some relevant indicators are proposed below; those generally only available from household surveys are designated (S), although data availability (and reliability) from service or administrative sources will vary greatly and may also require special surveys.
For assessing management of infectious diseases, the following indicators (usually as percentages) may be important: case fatality rates by disease (e.g. diarrhoea, pneumonia, measles; measles cases given vitamin A; individuals with chronic diseases given food and/or micronutrient supplements; proportion of mothers breastfeeding during child's illness (S); feeding patterns and frequency during child's illness (S); aspects of child care during illness including use of oral rehydration therapy (S).
For assessing prevention, the following indicators should be considered: incidence of low birth weight; age at first pregnancy; proportion of short birth intervals (e.g. less than 24 months); contraceptive prevalence rates. Other important information may be obtained from such data as: proportion of infants exclusively breastfed for four to six months (S); feeding frequency, weaning food preparation, with respect to both quantity and quality (S); vitamin A supplementation and disease-specific mortality (S).
Infectious disease control is assessed by a number of standard methods, generally involving household or individual surveys, which would include: immunization coverage rates; coverage of programmes for control of diarrhoeal disease, acute respiratory infections, parasites; proportion of individuals receiving effective primary treatment of infections.
The prevention and control of malnutrition/infection requires substantial inputs from other sectors than health to be effective. The priorities of those sectors may not be compatible with those of the health sector in terms of nature, area, targeting or timing; some examples follow. Physical planning and housing policies determine the adequacy of the physical (and often social) environment and the degree of overcrowding. The re-development of urban slums is a costly and sometimes disruptive process, and the extension of water and sanitation to temporary settlements often conflicts with longer term plans for permanent developments. Crowded education curricula may not permit the introduction of health education within official school hours and teaching staff may not live in the community. Agricultural policy which encourages commercial cash cropping may have adverse effects on nutrition if income increases are not translated into improved diet and better quality care. Irrigation schemes can markedly extend the distribution of schistosomiasis. Changes in agricultural patterns resulting in greater involvement of women and children can affect health care and exposure to infectious diseases (e.g. malaria, hookworm). Development of a more stable society and infrastructure can have a direct effect on infectious disease transmission (e.g. STDs).