Diarrhea in developing regions

Diarrheal disease is a disease of poverty, having an especially high prevalence among the populations of developing nations. The disease has an exceptionally high prevalence among the children of such developing populations, and is associated with high mortality rates and long-term detriments that impact access to central capabilities. There have been a number of approaches developed to combat the disease, however it remains a sizable problem globally.

Health effects
There is evidence to suggest negative impacts of diarrheal disease on both physical fitness and mental development. "Early childhood malnutrition resulting from any cause reduces physical fitness and work productivity in adults," and diarrhea is a primary cause of childhood malnutrition. Further, evidence suggests that diarrheal disease has significant impacts on mental development and health; it has been shown that, even when controlling for helminth infection and early breastfeeding, children who had experienced severe diarrhea had significantly lower scores on a series of tests of intelligence.

Cause
Poverty is a very good indicator of the prevalence of diarrheal disease in a population. This association does not stem from poverty itself, but rather from the conditions under which impoverished people live. The absence of certain critical faculties and resources compromises the capacity of the poor to defend themselves against the threat of diarrheal disease. "Poverty is associated with poor housing, crowding, dirt floors, lack of access to sufficient clean water or to sanitary disposal of fecal waste, cohabitation with domestic animals that may carry human pathogens, and a lack of refrigerated storage for food, all of which increase the frequency of diarrhea... Poverty also restricts the ability to provide age-appropriate, nutritionally balanced diets or to modify diets when diarrhea develops so as to mitigate and repair nutrient losses. The impact is exacerbated by the lack of adequate, available, and affordable medical care."



Clean water
One of the greatest causative factors in the incidence of diarrheal disease, is the lack of access to clean water sources. Often, improper fecal disposal leads to contamination of groundwater sources. Human feces contains a sizable variety of potentially harmful human pathogens, the majority of which are transmitted by the fecal-oral route (i.e. material contaminated with feces is unintentionally ingested leading to infection). When infectious feces is not disposed of properly, it can enter the water supply, causing wide-scale infection, and dissemination of disease, especially in the absence of water filtration or purification.

Nutrition
Proper nutrition is vital for proper health and bodily functioning, but it is also vital in the prevention of infectious diseases such as diarrheal disease, and is especially important to young children who do not have a robust and fully developed immune system. In fact, studies have shown that zinc deficiency, a condition often found in children in developing countries can, even in mild cases, have a significant impact on the development and proper functioning of the human immune system. Indeed, this relationship between zinc deficiency reduced immune functioning has been shown to correspond with an increased severity of diarrheal disease. Children who had lowered levels of zinc were found to have had a greater number of instances of diarrhea, severe diarrhea, and diarrhea associated with fever. Similarly, vitamin A deficiency can cause an increase in the severity of diarrheal episodes, however there is some discrepancy when it comes to the impact of vitamin A deficiency on the incidence of disease. While some scholars argue that a relationship does not exist between the rate of disease and vitamin A status, others suggest a significant increase in the incidence of diarrheal disease associated with vitamin A deficiency. Given that recent estimates suggest that approximately 127 million preschool children worldwide are vitamin A deficient, this vulnerable population has the potential for increased risk of disease contraction.

Breastfeeding
Breastfeeding practices have been shown to have a dramatic effect on the incidence of diarrheal disease in poor populations. Studies across a number of developing nations have shown that those who receive exclusive breastfeeding during their first 6 months of life are better protected against infection with diarrheal diseases. Exclusive breastfeeding is currently recommended during, at least, the first six months of an infant's life by the WHO.

Hand washing
Basic sanitation techniques can have a profound effect on the transmission of diarrheal disease. The implementation of hand washing using soap and water, for example, has been experimentally shown to reduce the incidence of disease by approximately 42–48%. Hand washing in developing countries, however, is compromised by poverty as acknowledged by the CDC: "Handwashing is integral to disease prevention in all parts of the world; however, access to soap and water is limited in a number of less developed countries. This lack of access is one of many challenges to proper hygiene in less developed countries." Solutions to this barrier require the implementation of educational programs that encourage sanitary behaviours.

Proper nutrition
Dietary deficiencies in developing countries can be combated by promoting better eating practices. Supplementation with vitamin A and/or zinc. Zinc supplementation proved successful showing a significant decrease in the incidence of diarrheal disease compared to a control group. The majority of the literature suggests that vitamin A supplementation is advantageous in reducing disease incidence. Development of a supplementation strategy should take into consideration the fact that vitamin A supplementation was less effective in reducing diarrhea incidence when compared to vitamin A and zinc supplementation, and that the latter strategy was estimated to be significantly more cost effective.

Clean water
Given that water contamination is a major means of transmitting diarrheal disease, water sanitation efforts have the potential to dramatically cut the rate of disease incidence. In fact, it has been proposed that we might expect an 88% reduction in child mortality resulting from diarrheal disease as a result of improved water sanitation and hygiene. Similarly, a meta-analysis of numerous studies on improving water supply and sanitation shows a 22–27% reduction in disease incidence, and a 21–30% reduction in mortality rate associated with diarrheal disease.

Water filtration
Chlorine treatment of water, for example, has been shown to reduce both the risk of diarrheal disease, and of contamination of stored water with diarrheal pathogens.

Immunization
Immunization against the pathogens that cause diarrheal disease is a viable prevention strategy, however it does require targeting certain pathogens for vaccination. In the case of Rotavirus which was responsible for around 6% of diarrheal episodes and 20% of diarrheal disease deaths in the children of developing countries, use of a Rotavirus vaccine in trials in 1985 yielded a slight (2-3%) decrease in total diarrheal disease incidence, while reducing overall mortality by 6-10%. Similarly, a Cholera vaccine showed a strong reduction in morbidity and mortality, though the overall impact of vaccination was minimal as Cholera is not one of the major causative pathogens of diarrheal disease. Since this time, more effective vaccines have been developed that have the potential to save many thousands of lives in developing nations, while reducing the overall cost of treatment, and the costs to society.

Treatment
While the above solutions primarily represent preventative measures for combating diarrheal disease, there are also cheap and easily accessible treatment options that are highly effective in preventing mortality following infection. Oral rehydration therapy (ORT) is a simple mixture of salts and sugar, which is mixed with water and then ingested. Studies have shown the overwhelming efficacy of ORT in preventing diarrheal disease deaths, with models predicting over 3 million deaths averted annually as a result of usage.

Epidemiology
Diarrhea is a common ailment worldwide, impacting many millions of people annually. As of 1990, there were a total of 9.4 incidences per person per year worldwide. When compared to other classes of disease, infectious gastroenteritis resulting in diarrheal symptoms constituted 16% of all illness, second only to upper respiratory tract infections. More recent studies suggest that these numbers have changed very little over the years. The majority of such cases, however, occur in the developing world, with over half of the recorded cases of childhood diarrhea occurring in Africa and Asia with 696 million and 1.2 billion cases respectively, compared to only 480 million in the rest of the world.

Diarrheal disease primarily affects the lives of the children of developing nations. Just twenty years ago, there were an estimated 12,600 child mortalities every day in Asia, Africa, and Latin America, while more modern estimates suggest around 2.5 million deaths annually. Further, the trend of increased disease prevalence in impoverished areas is present among children, with urban poor children having significantly higher rates of infection than their counterparts living in the United States. In India and Brazil, children experienced an average incidence of disease per year, that was six times greater than their American counterparts. In the Americas, diarrheal disease accounts for a total of 10% of deaths among children aged 1–59 months while in South East Asia, it accounts for 31.3% of deaths. A median estimates suggests that around 21% of child mortalities in developing countries are attributable to diarrheal disease.