Fecal Oral Route

Fecal material is almost universally recognized as being unsanitary. How is it then that the fecal-oral route is such an important source of disease transmission (in food and from direct contact, as well as for water)? Part of the answer can be seen in Figure 12.3. Towns historically have been located along rivers or streams that served as their water source. Water typically is withdrawn upstream of the town and wastewater is discharged downstream. Beyond the obvious sanitary merits of this approach, it allowed both water delivery and wastewater collection to be by gravity: the water and wastewater flowing downhill. However, as areas became more densely populated, the wastewater discharge of one town soon became the water intake for the next community downstream.

Raw w

Raw w

Figure 12.3 Typical pattern of water supply and wastewater disposal.

Most diseases transmitted by the fecal-oral route (whether through water, food, or direct contact) have their primary effect on the intestines and thus are referred to as enteric. To understand their importance, it is helpful to look at the historical impact of two such bacterial diseases, cholera and typhoid fever.

Cholera Cholera is an acute intestinal disease marked by severe diarrhea and vomiting. The bacterium responsible, Vibrio cholerae, reproduces in the small intestine, releasing an enterotoxin (a toxin affecting the intestines) that triggers the resultant stress on the victim. Bodily fluids may be depleted so rapidly that the victim dies within hours unless preventive measures are taken, such as providing intravenous replacement of fluids and salts.

Cholera was originally endemic to South Asia, but there have been seven major pandemics (the first beginning in 1817), and it is now also endemic to South and Central America and perhaps to the Gulf coast of the United States. The early U.S. epidemics (first: 1832-1834; second: 1849-1854) produced widespread fear—not surprisingly, since there was no cure for this usually fatal disease. In 1832, 20% of the population of New Orleans died of cholera, while in 1849 another 5000 people died there, along with 8000 in New York City.

In 1854, Dr. John Snow (Figure 12.4) performed two studies of the incidence of cholera in London. These are now recognized as the first epidemiological studies ever

Figure 12.4 John Snow in 1857, one year before his death.

Figure 12.5 John Snow: cholera deaths and the Broad Street pump.

conducted, predating the formalization of the germ theory of disease (Section 12.1.1). In the better known of these studies, Snow plotted on a map the residence of each person who died of cholera in one area of town served by public wells with pumps (buildings there did not have indoor plumbing). He found 521 cholera deaths within 250 yards of the Broad Street pump (Figure 12.5). The incidence of cholera was much higher among people living close to, and therefore presumably using water from, this pump as opposed to others located in the area. He also found evidence that this well was contaminated with sewage, and in an example of an early public health measure, had the pump handle removed (rendering it unusable)! The adjacent pub is now named in his honor (Figure 12.6).

In the second study, Snow reviewed cholera deaths in another part of London served by two competing water companies. Customers of the Southwark and Vauxhall Company had 31.5 cholera deaths per 1000 houses served, whereas the rate for the Lambeth Company was 3.7 per 1000 houses served. Both companies took their water from the Thames River and delivered it through pipelines, without treatment. However, Southwark and Vauxhall withdrew water from the river near central London, where it was contaminated with untreated sewage, whereas Lambeth's source was upstream of the city, and relatively pure.

Attempts to control cholera also figured in some of the earliest efforts at water purification as a public health measure. During the German epidemic of 1892, the adjoining cities Hamburg (upstream) and Altona (downstream) were drawing their water from the Elbe. However, Altona practiced slow sand filtration, and despite the more contaminated

Figure 12.6 Snow's Pub in London's Soho district, adjacent to the infamous Broad Street pump.

water source, had a cholera death rate of only 2.3 per 1000 people (many traceable to drinking Hamburg water), compared to 13.4 for Hamburg (Table 12.4).

Medical treatment traditionally involved intravenous rehydration until the disease ran its course. However, this was not available to many in poorer countries. A simpler treatment called oral rehydration therapy (ORT) is saving many lives around the world (see Section 9.9).

Cholera was eradicated (eliminated) in the United States in 1911. However, it reappeared in 1973, and there have been small numbers of cases since, mostly associated with eating shellfish harvested along the coast of the Gulf of Mexico. Worldwide, cholera still accounts for more than 120,000 deaths per year.

Typhoid Fever Although typhoid fever (caused by Salmonella typhi) was later transmitted mainly through food in the United States, originally it was also a major waterborne disease. Although it does not have as high a mortality rate, and thus did not provoke quite the same level of fear as cholera, it probably lead to more deaths overall: 500,000 cases with 40,000 deaths in 1909, for example. Water filtration also had a beneficial effect in reducing the incidence of typhoid fever, as can be seen in Table 12.4 for the cities of Pittsburgh, Cincinnati, and Louisville.

Another water treatment technology, disinfection with chlorine, was first utilized for an urban water supply in the United States in Jersey City, New Jersey, in 1908. Some of the early beneficial effects of chlorination in controlling disease are also shown in Table 12.4.

TABLE 12.4 Correlation between Sand Filtration (SF) or Chlorination (Chlor) of Water Supplies and Deaths from Cholera or Typhoid Fever

Disease

Date

City

Treatment

Deaths

Rate/100,000

Cholera

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